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CTBUH Research Report

Dario Trabucco, Antony Wood, Olivier Vassart, Nicoleta Popa, and Donald Davies

Life Cycle Assessmentof Tall Building Structural Systems

© Council on Tall Buildings and Urban Habitat

Research Funded by:

Dario Trabucco, Antony Wood, Olivier Vassart, Nicoleta Popa, and Donald Davies

Life Cycle Assessmentof Tall Building Structural Systems


Bibliographic Reference:Trabucco, D., Wood, A., Popa, N., Vassart, O. & Davies, D. (2015) Life Cycle Assessment of Tall Building Structural Systems. Council on Tall Buildings and Urban Habitat: Chicago.

Principal Research Investigators: Dario Trabucco, Antony Wood, Olivier Vassart, Nicoleta Popa & Donald DaviesAdditional Researchers: Meysam Tabibzadeh, Eleonora Lucchese, Mattia Mercanzin & Payam BahramiEditorial Support: Jason GabelLayout: Mattia Mercanzin & Marty Carver

Published by the Council on Tall Buildings and Urban Habitat (CTBUH) in conjunction with ArcelorMittal

© 2015 Council on Tall Buildings and Urban Habitat

Printed and bound in the USA by The Mail House

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Library of Congress Cataloging-in-Publication DataA catalog record has been requested for this book

ISBN: 978-0-939493-48-7

Council on Tall Buildings and Urban HabitatS.R. Crown Hall Illinois Institute of Technology3360 South State StreetChicago, IL 60616Phone: +1 (312) 567-3487 Fax: +1 (312) 567-3820Email: [email protected] www.ctbuh.orgwww.skyscrapercenter.com

CTBUH Asia Headquarters OfficeCollege of Architecture and Urban Planning, Tongji University1239 Si Ping Rd, Yangpu District, Shanghai, China 200092 Phone: +86 21 65982972Email: [email protected]

CTBUH Research OfficeIuav University of Venice Dorsoduro 2006, 30123 Venice, ItalyPhone: +39 041 257 1276 Email: [email protected]

Front Cover: Image sources; Clockwise from top left: FreeImages.com/Bo de Visser; Marshall Gerometta, (cc-by-2.0) U.S. Army Materiel Command, mzacha via RGBStock, FreeImages.com/steph poitiers

Research Funded By:


Principal Researchers / Authors

Dario Trabucco, Research Manager, CTBUH / Iuav University of VeniceAntony Wood, Executive Director, CTBUH / Illinois Institute of Technology / Tongji University

Olivier Vassart, Head of Global R&D Long Carbon, ArcelorMittalNicoleta Popa, Senior Research Engineer, ArcelorMittal

Donald Davies, Principal, Magnusson Klemencic Associates

Additional Researchers / Contributors

Eleonora Lucchese, CTBUH Research Office, VeniceMattia Mercanzin, CTBUH Research Office, Venice

Meysam Tabibzadeh, CTBUH Research Office, ChicagoPayam Bahrami, CTBUH Research Office, Chicago

Contributors / Project Steering / Peer Review Panel

Mark Aho, McNamara / SalviaPeyman Askarinejad, Arabtec

Martina Belmonte, CTBUH/IUAV Joseph Burns, Thornton Tomasetti

Luis Simoes Da Silva, University of CoimbraEdward DePaola, Severud Associates

Chukwuma Ekwueme, Weidlinger AssociatesPaul Endres, Endres Studio

David Farnsworth, Arup Rolf Frischknecht, Treeze

Erleen Hatfield, Buro HappoldBen Johnson, Skidmore, Owings & Merrill

Leif Johnson, Magnusson Klemencic AssociatesMakoto Kayashim, Taisei

Raffaele Landolofo, University of NaplesDennis McGarel, Brandenburg

Declam Morgan, Buro HappoldLevon Nishkian, Nishkian Menninger

Tatsuo Oka, Utsunomiya UniversityArif Ozkan, Arup

Stefano Panseri, DespeJohn Peronto, Thornton Tomasetti Dennis Poon, Thornton Tomasetti

Christopher Rockey, Rockey StructuresRonald Rovers, RiBuilIT

Tim Santi, Walter P MooreAllen Thompson, WSP

Robert Victor, BrandenburgJohn Viise, Thornton Tomasetti

Wolfgang Werner, Urban FabrickYong Wook Jo, Arup

Nabih Youssef, Nabih Youssef & Associates


4 © Council on Tall Buildings and Urban Habitat

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Contents

About the CTBUH 6 About ArcelorMittal 6 About the Authors 7

Preface 8

1.0 Tall Buildings Today 12 1.1 Role of Structural Systems in a Tall Building 14 1.2 Review of Current Structural Systems in Tall Buildings 16 1.3 Foundation Types 21

2.0 Sustainability and Tall Buildings 24 2.1 Energy Consumption of Tall Buildings 27 2.2 Embodied Energy of Tall Buildings 30

3.0 Life Cycle Assessment 32 3.1 Explanation of ISO LCA 34 3.2 Definition of the Goal of the Study 35 3.3 Scope Definition of this Study 36 3.4 Scenario Analysis and Identification of 37 Functional Units 3.5 System Boundaries 40 3.6 Structural Systems and Materials 40 3.7 Floor Systems Used 40 3.8 Inventory of Materials 41

4.0 Steel: Cradle to Grave 44 4.1 Steel Production 46 4.2 Structural Steel Profiles 48 4.3 Steel Plates 48 4.4 Steel Fabrication 49 4.5 Steel Rebar 50 4.6 Welded Wire Fabric 51 4.7 Metal Decking 52 4.8 Steel Production Inventory Data 53 4.9 Life Phase 54 4.10 Recycling 55

5.0 Concrete: Cradle to Grave 58 5.1 Cement Production and Transportation 60 5.2 Cement Substitutes 61 5.3 Gravel, Sand, and Aggregates 64 5.4 Concrete Production and Transportation 65 5.5 Environmental Data for Concrete 66 5.6 Recycling of Concrete and Aggregates 68

6.0 Fireproofing Materials: Cradle to Grave 70 6.1 Types of Fireproofing Materials 73 6.2 Environmental Impacts of Fireproofing Materials 74

7.0 Transportation and On-Site Energy Use 76 7.1 Transportation and On-Site Operations in Literature 78 7.2 Transportation 81 7.3 Crane Operations 81 7.4 Concrete Pumping 83 7.5 Formworks 84 7.6 Foundations 84

8.0 The End-of-Life of Tall Buildings 86 8.1 High-Rise Demolition Techniques 88 8.2 Impact of Structural Materials on the 90 End-of-Life of Tall Buildings 8.3 Energy Use in Demolition 91 8.4 Transportation Assumptions for Debris 93 8.5 Sources of Data on Tall Building Demolition 94

9.0 Inventory of Materials and Research Results 96 9.1 The Assessment of Two Environmental Impacts 98 9.2 Comments on the Selected Indicators 98 9.3 Research Results 99 9.4 Comparison with Literature Results 99 9.5 General Research Conclusions 102 9.6 Future Research 107

10.0 Appendix: Detailed Results of Each Modelled Scenario 112

Acknowledgements 178

Bibliography 179


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About the CTBUH

About the Research Funding Sponsor: ArcelorMittal

The Council on Tall Buildings and Urban Habitat (CTBUH) is the world’s leading resource for professionals focused on the inception, design, construction, and operation of tall buildings and future cities. A not-for-profit organization, founded in 1969 and based at the Illinois Institute of Technology, Chicago, CTBUH has an Asia office at Tongji University, Shanghai, and a research office at Iuav University, Venice, Italy. CTBUH facilitates the exchange of the latest knowledge available on tall buildings around the world through publications, research, events, working groups, web resources, and its extensive network of international representatives. The Council’s research department is spearheading the investigation of the next generation of tall buildings by aiding original research on sustainability and key development issues. The Council’s free database on tall buildings, The Skyscraper Center, is updated daily with detailed information, images, data, and news. The CTBUH also developed the international standards for measuring tall building height and is recognized as the arbiter for bestowing such designations as “The World’s Tallest Building.”

With annual achievable production capacity of approximately 127 million tons of crude steel, and 222,000 employees across 60 countries, ArcelorMittal is the world’s leading steel and mining company. With an industrial presence in over 20 countries, they are the leader in all major global steel markets including automotive, construction, household appliances and packaging, with leading research and development and technology, sizeable captive supplies of raw materials, and extensive distribution networks.

ArcelorMittal uses their researchers’ expertise in steel to develop cleaner processes and greener products, including ultra-high-strength steels (UHSS) and Ultra-Low CO2Steelmaking (ULCOS), to make steel production more sustainable and help reduce both their own environmental impact and that of their customers.

Co u n c i l o n Ta l l B u i l d i n g s a n d U r b a n H a b i t a t


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About the Authors

Dr. Dario Trabucco, PhD Research Manager, Council on Tall Buildings and Urban Habitat / Researcher, Department of Architecture Construction and Conservation, Iuav University of VeniceVenice, Italy

Dario Trabucco is a tenured researcher in Building Technology at Iuav University of Venice, Italy. From March 2013 to February 2014 Dario was a research associate at the Council on Tall Buildings and Urban Habitat/Illinois Institute of Technology, primarily working on the funded research project “A Whole Life Cycle Assessment of the Sustainable Aspects of Structural Systems in Tall Buildings.” In 2014, he assumed the role of CTBUH Research Manager and established the CTBUH Research Office in Venice. Since then, he has acted as Principal Investigator for two additional sponsor-funded research initiatives by the CTBUH, “A Study on the Architectural and Engineering Properties of Composite Megacolumns” sponsored by ArcelorMittal and “A Study on the Damping Technologies Available for Tall Buildings: Comfort and Safety,” supported by Bouygues Construction.

Dr. Antony Wood, PhD, RIBA Executive Director, Council on Tall Buildings and Urban Habitat / Research Professor, Illinois Institute of Technology / Visiting Professor, Tongji University, ShanghaiChicago, USA

Antony Wood has been Executive Director of the Council on Tall Buildings and Urban Habitat since 2006. He is responsible for the day-to-day running of the Council in conjunction with the Board of Trustees, of which he is an ex-officio member. Prior to this, he was CTBUH Vice-Chairman for Europe and Head of Research. His tenure has seen a revitalization of the CTBUH and an increase in output and initiatives across all areas. Based at the Illinois Institute of Technology, Chicago, Antony is also a Research Professor in the College of Architecture at IIT, and a visiting professor of tall buildings at Tongji University Shanghai. A UK architect by training, his field of speciality is the design, and in particular the sustainable design, of tall buildings.

Nicoleta Popa Senior Research Engineer, ArcelorMittalLuxembourg City, Luxembourg

Nicoleta has been involved in, managed and coordinated internal and European research projects, with partners and subcontractors coming from all over Europe, USA and China. Each research project aims at achieving deliverables such as: new products and solutions, standards/codes/regulations/technical agreements, design aids, as well as promotional materials and campaigns. Her expertise includes: fire design, composite construction, composite bridges, cost optimization, sustainability and building physics. She has ensured the dissemination of research results through seminars, conferences, distribution to engineers and architects as well as through papers in scientific publications, conferences, and seminars.

Professor Olivier Vassart Head of Global R&D Long Carbon, ArcelorMittalLuxembourg City, Luxembourg

Olivier Vassart graduated as a Structural Engineer from the Polytechnic School of Louvain in Belgium. He also completed a PHD in Fire engineering at the University Blaise Pascal in France. Since 2002, he has worked for ArcelorMittal, where he is now a member of the Board of Directors of ArcelorMittal Global R&D in charge of the Long Carbon Sector. As well as his activities for ArcelorMittal, he is Professor of Steel and Composite Structures at the University Catholic of Louvain in Belgium and he is also an Invited Professor at the University of Ulster Firesert Northern Ireland.

Donald W. Davies, P.E., S.E. Senior Principle, Magnusson Klemencic Associates Seattle, USA

Donald Davies is a Senior Principal at Magnusson Klemencic Associates (MKA). He leads MKA’s Hospitality and High-rise Residential work, as well as MKA’s Sustainability Committee. Don is a CTBUH advisory group member; and a founding board member of the Carbon Leadership Forum, an academic/professional collaboration focused on carbon-reduction strategies in the built environment. Over his 25-year career, Don has designed buildings up to 105 stories tall, with projects in more than 31 US cities and 16 countries.


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Preface

Despite the history of the skyscraper spanning well over a century, and the fact that the world is now constructing tall buildings in excess of 1,000 meters in height, with the exception of the events of 9/11, we have never actually demolished or dismantled a building taller than 187 meters. That building was the Singer Building, a 187-meter tower in New York City that was demolished in 1968 to make way for 1 Liberty Plaza. The reality is that we are now building many hundreds of skyscrapers – in addition to those already in existence – with little idea about their real longevity, what variances and experiences they will have during their whole life cycle, and what will happen to them at the end of that life cycle.

These are massively important issues that should influence the design of all skyscrapers from the very outset (i.e., how to design buildings for multiple changes in function, an indeterminate future, or even perpetual existence?), but the industry does not even have a template for assessing the relative implications – energy or otherwise – of the different stages of a building’s life. In the sustainability realm, emphasis has been placed on the reduction of operational energy at the expense of all other facets. While the reduction of operating energy is vitally important, it is far from the complete picture. Reducing the embodied energy of the materials in the building itself is equally important. As technologies increasingly allow buildings to move towards carbon-neutral operation (though we are still far away from that holy grail), embodied energy will become the main energy consumer, and thus it is the most critical area for further consideration now. In short, the true environmental impact

of the full life cycle of tall buildings is a significantly unknown quantity.This is the point of departure for this guide, and the three-year research project that underpins it. A Life Cycle Assessment (LCA) is a methodology that gauges the consequences of human actions by analyzing the flow of materials used in a product or a building and traces the environmental impacts linked to each stage of its life cycle. An LCA thus begins by analyzing the effects of material extraction and processing, accounting for the specific pieces of equipment used and the energy needed to turn raw materials into a final product (in this case, a building). The assessment also evaluates the impacts of manufacturing, transportation, and on-site construction activities, taking note of both power consumption and carbon emissions during each process. Finally, operational activities, demolition, and end-of-life recycling are considered. When information from each stage is combined, a holistic picture of environmental impacts can be formed for a given product, one that acknowledges the various actions that are required to bring a single entity into existence through contemporary means.

The true benefits of the LCA methodology are realized when numerous assessments are performed for different versions of a product. This allows researchers to compare alternatives along various impact categories, and provides a basis for making informed decisions that produce the greatest environmental benefits over time. Given this fact, it is clear that Life Cycle Assessment is largely the missing piece in the sustainable puzzle for tall buildings.

This research, which was undertaken by the CTBUH Research Division and sponsored by multinational steel manufacturer ArcelorMittal, identifies and compares the life cycle implications for multiple comparative structural systems found in 60- and 120-story buildings. Structural systems are by no means the entirety of a tall building, and an LCA of the components that are more likely to change over time (façades, MEP systems, interior fit out) would also be extremely valuable. However, the means to evaluate life cycle energy is still in its infancy and is an especially complicated subject. Thus, for this first study, focusing on the structural systems of a building – which accounts for a large share of the material inventory and has major impacts on all aspects of building performance – seemed a sensible choice.

This report thus represents the first-ever full LCA on tall building structural systems ever performed, and represents a “first stab” at environmentally quantifying the decisions made in the design and engineering process of skyscrapers. Using the results found herein, industry professionals and researchers can recognize the performance of these systems along two key impact categories: Global Warming Potential (GWP) and Embodied Energy (EE). Global Warming Potential is measured by calculating the amount of carbon (or carbon equivalent) that is released over the course of a structure’s life cycle, allowing impacts on climate change to be determined. Embodied Energy was selected as an indicator for natural resource depletion, since the amount of energy consumed over the lifetime of the structural systems and their materials has direct implications


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for the consumption of electricity, fossil fuels, and natural gas. In addition to this report’s ability to serve as a reference in the design process, it also serves as a launching point for further research into the life cycle of tall buildings. Indeed, as is typical with undertakings of this nature, more questions tend to arise than answers. From the outset, it was the Council’s goal to explore this topic with an emphasis on finding where further investigation is needed. Suggestions for further research are thus provided at length in the final section of the report.

As evidenced in this study, the CTBUH Research Division plays a very important role, not only in achieving the Council’s mission of disseminating information on tall buildings to professionals and stakeholders around the world, but to engage in the global debate on sustainability that has relevance far beyond the industry itself. The CTBUH is well-positioned for research such as this due to its intermediary role between a diverse set of professionals, with members and contributors ranging from architects, engineers, material specialists, owner/developers, city planners, construction companies, and equipment suppliers. The Research Division is one of the ways that the Council uses these resources to address the research gaps identified in the Roadmap on the Future Research Needs of Tall Buildings, a 2014 CTBUH publication that lists and prioritizes topics that are in greatest need of further exploration. By focusing the efforts of the CTBUH in this way, attention is brought to often ignored or underrepresented aspects of tall buildings, mobilizing individuals to obtain a more complete understanding of the industry.

The daunting complexities of life cycle research require the collaboration between numerous individuals within varying specializations. This LCA alone drew on the support and expertise of numerous companies, all of whom are acknowledged on page 178. Thus, this project is truly an indication of concern for many in the tall building industry regarding the “big picture” of sustainability for our cities. So let this report serve not only as a plunge into an emerging field of study, but a call to action that emphasizes the importance of looking at the consequences of our choices, from beginning to end.

Antony WoodChicago, USA

Dario TrabuccoVenice, Italy


1.0 Tall Buildings Today


Figure 1.2: Equitable Life Building, 1870, New York, considered by some to be the first tall building in history due to its exploration of the potentialities offered by the passenger elevatorSource: (public domain) Emerson7

Figure 1.1: Home Insurance Building, 1885, Chicago, generally accepted as the first tall building because of its curtain wall construction on a steel frame.

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The Council on Tall Buildings and Urban Habitat (CTBUH) recognizes three different ways of defining a tall building. According to the CTBUH, tall buildings exhibit some element of “tallness” in one or more of the following categories:

• Height Relative to Context: a building is taller than those in the surrounding area with respect to a prevailing urban norm;

• Proportion: a tall building has a slender appearance made evident by a relatively small base in comparison to its height;

• Tall Building Technologies: a building contains technologies which may be attributed as being a product of its height (e.g. specific vertical transport technologies, structural wind bracing as a product of height, etc.).

In addition to the above criteria, there are two definitions that establish universal height thresholds for tall buildings: the CTBUH defines “supertall” buildings as those over 300 meters in height, and “megatall” buildings as those over 600 meters in height. Although great vertical strides are currently being achieved by an increasing number of tall buildings every year, there are only 93 supertall and three megatall buildings completed and occupied globally as of June 2015.

The birthplace of the tall building typology is still a heavily debated topic among experts. However, it is commonly agreed that the first tall buildings in history were found in New York and Chicago (Barr, 2014).

An early observation by Fryer (Fryer, 1891) mentions three basic elements that contributed to the birth of skyscrapers:

1.0 Tall Buildings Today

| Tall Buildings Today © Council on Tall Buildings and Urban Habitat

Figure 1.3: Load bearing wall system for skyscrapers Monadnock Building, Chicago, (Floor Plan)Source: Leslie, Thomas (2013), “The Monadnock Building, Technically Revisited” CTBUH Research Paper, 2013 Issue IV, pp 29. Redrawn by CTBUH

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the modern passenger elevator, the invention of iron/steel structures (see Figure 1.1), and the terracotta flat arch element to protect horizontal iron beams from fire. Rem Koolhaas (Koolhaas, 1978), almost one century later, also cites steel frameworks and the passenger elevator as the elements that made the construction of tall buildings possible.

Both of the above definitions exclude several notable examples of buildings that, despite having a load bearing masonry wall system (such as the 1893, 17-story Monadnock Building in Chicago), can clearly be considered a tall building (Leslie, 2013).

Considering this argument, the elevator is the only remaining determinant for a tall building. In this case, the Equitable Life Building (see Figure 1.2), completed in New York in 1870, would be the first tall building in the history due to its exploration of the potentialities offered by the passenger elevator (Weisman, 1970).

The increased heights and different shapes that New York skyscrapers adopted as a result of the 1916 Zoning Resolution, which also affected the design of tall buildings in all other American cities (Willis, 1986), did not alter the basic structural schemes used since the birth of the skyscraper typology. In fact, from a structural perspective, all skyscrapers built before the Second World War are quite similar, and were based on the principle of a rigid frame, with required stability against lateral loads provided by the stiffness of beam-column connections (Ali & Moon, 2010) as well as the natural bracing effect provided by the solid façade panels. The solid decorated urban blocks used in early skyscrapers evolved since the 1950’s toward a more neat and transparent

style that spread all over the world in a movement known as the “International Style.” Even if virtually all tall buildings have a façade freed from any load bearing or structural function, the International Style marked an evolution in the performance of tall buildings. Fully glazed and sealed façades, introduced for the first time in buildings such as the Lever House in New York and the Commonwealth Building in Portland, Oregon, dramatically reduced the thermal inertia of buildings.

This lead to an increase in the reliance on mechanical air conditioning and ventilation systems, together with the thermal inertia of the internal structure and surfaces. Glazed façades also significantly reduced the weight of tall

buildings, while also taking away the solid walls punctuated by small windows that provided bracing against lateral loads.

As a consequence of this, and of the increasing height and slenderness of tall buildings, bracing functions were later transferred toward the interior by creating braced trusses around the elevator core. Thus, using these new features, the modern tall building typology was born. One of the earliest examples of these features can be found in the Seagram Building in New York.

Since the end of the Second World War, tall buildings have spread from their country of origin, the United States of America, to become a global symbol of modernity and

Tall Buildings Today | © Council on Tall Buildings and Urban Habitat

Figure 1.4: Graph illustrating the “Premium for Height” conceptSource: CTBUH Redrawn on the basis of M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects,” Architectural Science Review, Volume 50.3, pp. 205-223

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wealth in many countries, with landmark towers erected all over the world, from South America to Europe, and from Russia to Australia. However, US cities remained the testing grounds for tall buildings, at least until the 1970s, when cities in Asia began raising their financial districts towards the sky. This latter phenomenon was different from what happened 20 years earlier in Europe and South America. In fact, cities such as Tokyo, Hong Kong, Seoul, and many others started to build their own landmark towers, yet dozens of normal, functional skyscrapers were also built to accommodate new businesses and residences. In response to the demographic trends and booming economies of the 1990s, other countries started to develop significant tall building cultures: Philippines, Indonesia, and Singapore built their own vertical cities by adopting an American model. In the 2000s, while the echoes of the 9/11 terrorist attacks were questioning the future of tall buildings in the US, skyscrapers became a global phenomenon: China, United Arab Emirates, Panama, South Korea, Singapore, Qatar, Australia, Canada, Turkey, and other countries marked their presence in the skyscraper world with the development of many new tall and

supertall buildings. During the same period, more conservative European cities also experimented with the construction of tall buildings (London, Madrid, Milan, Paris, Frankfurt, Moscow, Saint Petersburg, etc.), not as a dominant building type, but as unique, widely debated landmarks.

Today (in 2015), more than 3,000 towers taller than 150 meters exist in the world and this number increases at an unprecedented rate, with one new tower opening for business every other day, mostly in Asian cities.

1.1 Role of Structural Systems in a Tall Building

From a structural point of view, a tall building is simply a beam cantilever with its base fixed to the ground. The structural systems must provide resistance to vertical loads (the building’s weight and design loads) as well as shear and bending resistance to lateral loads caused by wind and earthquakes.

Gravity loads do not affect tall buildings in the same way as low- or mid-rise buildings. Gravity loads can be

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static (permanent) or dynamic (time dependent). Static loads include the weight of structural and non-structural elements and can therefore be calculated at the design stage. On the contrary, live loads are less predictable and their design values are defined by building codes, as they can be uniformly distributed or concentrated depending on the use of each space.

As these values take a lot of safety factors into account, they are very conservative and tend to be overestimated.

Considering that the vertical load design principles for tall buildings are not significantly different from standard buildings and they scale proportionally with the size of the building, they do not impact the design of various structural elements, except for the floor systems. What should be carefully considered in this case are the effects of lateral loads; mainly, seismic and wind forces.

These two forces don’t follow a proportional progression with building height. Instead, their effects on structures increase exponentially as buildings get taller. Accordingly, a tall building is also defined by its structural consideration of horizontal forces over vertical forces. As a consequence, it is important to acknowledge the lateral resisting system of a tall building structure.

During the 1960s, Fazlur Khan introduced the concept of a “premium for height” (Ali & Moon, 2010) (see Figure 1.4). Since floor system weight remains constant with a regular building plan, the ratio of floor weight to the number of floors remains constant as building height increases. At the same time, the size and number of columns must increase progressively toward the base of the building in order to transmit the gravity loads accumulated


Figure 1.5: Woolworth Building under construction, 1913, New York CitySource: (cc-by-sa) Bain News Service

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on the floors above. Thus, considering only gravity loads, doubling the number of stories means doubling the weight and strength of the columns. However, when lateral loads are taken into account, the amount of materials used in columns must be increased even more. In this case, columns need to be heavier, going from the top toward the base, to resist lateral loads, and the weight of the lateral resisting elements should also be considered when calculating the weight/gross area ratio.

As the height of the building increases, the lateral drifts start to control the design of the structure, and the stiffness of the components becomes the dominant factor instead of their strength. Therefore, the need for appropriate structural systems, beyond the simple rigid frame, must be properly addressed in the design of tall buildings, accounting for the prominent loads and forces that differ depending on a building’s height.

Many aspects should be carefully considered when addressing lateral loads, especially in the case of wind: strength and stability, fatigue, excessive lateral deflections, frequency and amplitude of sway (the resonance of building oscillations can create problems with an elevator’s hoist rope), and possible buffeting are some of these aspects. Additionally, wind can also affect the surroundings of a building. There can be wind acceleration nearby or annoying acoustic disturbances that can be heard from far distances. Overall, it is necessary to consider wind loads when determining the required strength and stiffness of building frames.

The effect of wind on a building can be described as follows: when wind vortices are shed alternately first on one side and then on the other side of a

building, impulses occur in a direction perpendicular to the downstream flow, alternating from left to right, in addition to the impulse in the along-wind direction. Therefore, in addition to a building’s superstructure, information on local wind conditions is required in order to determine the necessary strength and stiffness of wall elements, roof elements, and their fastenings.

Looking at the seismic design of structures, as their degree-of-freedom increases, there is a higher number of significant modes to be taken into consideration and the response to seismic excitement becomes more complex. Tall buildings appear to be less flexible than

“...the ideal structure to withstand the

effects of bending, shear and vibration is a system in which the vertical elements are

located at the furthest extremity.”


Figure 1.8: International Style example: United Nations Secretariat Building, 1953, New York City Source: (cc-by-sa) ZeroOne

Figure 1.7: Commercial style high-rise example:Guaranty Building, 1896, New York City Source: Terri Meyer Boake

Figure 1.6: Commercial style high-rise example:Home Insurance Building, 1885, ChicagoSource: (cc-by-public domain) LX

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low-rise buildings and thus generally experience lower accelerations. On the other hand, when the attenuation of seismic waves is taken into account, long-period components are not attenuated as fast as short-period components with the distance from a fault. Thus, taller buildings can experience more severe seismic loads than low-rise buildings that are located at the same distance from a fault. Overall, from a seismic design perspective, while members designed for vertical loads are able to provide the resistance required for the vertical aspect of the seismic loads, a dedicated lateral load-resisting system must be designed to withstand the inertial forces caused by ground motion.

Strength and stiffness are the main parameters controlling the limiting factors of motion and vibration. With lateral forces being the driving parameter for the design of a tall building’s structural system, the ideal structure to withstand the effects of bending, shear, and vibration is a system in which the vertical elements

are located at the farthest extremity from the geometric center of the building (Taranath, 1998), such as in a hollow tube. Here, the parameters that control the efficiency of the structural element’s layout are bending and shear rigidity. From the bending rigidity standpoint, the best solution would be to maximize the total moment of inertia of the overall structure, positioning columns at the corners along the outermost perimeter of the building. As far as shear efficiency is concerned, the ideal solution would be a continuous wall without openings.

The existing structural systems used in contemporary tall buildings stem from the basic principles described above. During the last 50 years, rigid frame systems adopted in older tall buildings evolved into different structural families that are used depending on a number of parameters including the size of the building, the magnitude of the external solicitations, the availability and cost of materials, and labor and stylistic decisions made by the

architect and the developer (to maximize the real estate value of the building).

1.2 Review of Current Structural Systems in Tall Buildings

From the first 12-story skyscraper born in Chicago in 1885, the Home Insurance Building, to the under-construction 1000 meter Kingdom Tower, structural systems for tall buildings move with the times, changing according to not only architectural styles, but also technical evolutions (e.g., vertical transportation systems, construction techniques, and mechanical services).

The first phase of skyscraper evolution happened in the Midwestern United States, with Chicago at the epicenter. Economic drivers allowed the first tall buildings to develop in response to the ever-growing need for office space and high-value rentable areas. After the Great Chicago Fire in 1871, “Commercial Style” high-rise structures were characterized


Figure 1.9: Empire State Building under construction, 1930-1931, New York CitySource: (cc-by-sa) Daniel Ahmad

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by steel rigid frames clad with non-load bearing materials such as brick, terracotta, and glass windows (see Figures 1.6 and 1.7). This kind of structural choice became preferred over the use of conventional load-bearing masonry walls, which were considered outdated (as they were not fire resistant). As a result of this new structural system, a surge of skyscraper development began in New York City, resulting in significant achievements like the Chrysler Building (319 m, 1930), the Empire State Building (381 m, 1931) (see Figure 1.9), and the General Electric Building (196 m, 1931). Unfortunately, as the race continued into the 1950s and 1960s, no major technical advancements were developed. Since structural analyses at the time were still affected by many uncertainties, the buildings of that period were overdesigned. Aside from the efficient use of steel rigid braced frames, the amount of materials used in these buildings was excessive. The economic upturn after World War II revitalized the development of skyscrapers, and was accompanied by

the application of European modernist architectural practices.

The use of steel rigid frames was then replaced by tubular forms. Led by the technological growth that supported the development of rational analysis systems, the adoption of structural tubes led to the development of the so-called “International Style” skyscrapers (see Figure 1.8). Major examples of this period includes the World Trade Center in New York (417 m, 1972) and the Willis Tower in Chicago (442 m, 1974). From the 1980s, a driving Postmodern architectural force guided tall structures towards the development of “mega-frames”, core-and-outrigger systems, as well as mixed steel and concrete structures.

No longer is the International Style a dominant force, as a host of factors must now be taken into account in skyscraper development. The balance between innovation and consumption now involves practical requirements and site

conditions, the supply, transportation, and delivery of materials, preferred construction methods, and many others. These issues entail the need for designers to consider all of the identification factors typical of each job site from time to time (Balridge, 2008, March 3-5).

Classifications based on different parameters were proposed by many authors. Probably one of the most renowned and highly adopted is the classification proposed by Mir Ali and Kyoung Sun Moon (Ali & Moon, 2010), which distinguishes interior structural systems from exterior structural systems. This classification is based on the distribution of the primary lateral load-resisting components across the building layout. Interior structures are those in which the lateral load resisting system is located on the interior of the building (called the core). Likewise, in an exterior structure, the lateral load resisting system is located along the building perimeter (see Figures 1.10, 1.12, 1.14 and 1.16).


Figure 1.10: Classification of tall building structural systems by Fazlur Khan (concrete) Source: M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects,” Architectural Science Review, Volume 50.3, pp. 205-223. Redrawn by CTBUH

Figure 1.11: “Rigid-frame” example: Seagram Building, 1958, New York CitySource: Marshall Gerometta

18

The following structural systems can be defined as the first category, interior structures:

• Braced hinged-frames: Steel shear trusses and steel hinged frames are included in this type as they resist lateral loads via axial forces in the shear truss members. They are effective for buildings up to about 10 stories.

• Rigid frames: A frame is considered rigid when its beam-to-column connection has sufficient rigidity to hold (virtually unchanged) the original angles between intersecting members. Rigid frames can be made up of either steel or concrete members. Moment-resisting frames are effective for buildings up to about 30 stories (see Figure 1.11).

• Shear wall: These structures benefit from the presence of concrete single or coupled shear walls acting as lateral load resisting elements. They

are effective for buildings up to about 35 stories.

• Shear wall (or shear truss) – frame interaction systems: Shear walls are interconnected with a system of beams and columns (rigid frame). The frame deflects in a shear mode, while shear walls deflect in a bending mode. As the two systems coexist in the same building, they are forced to sway together. This results in an enhanced stiffness since the walls are restrained at the upper level by the presence of the frame, and vice versa at the lower levels where the shear walls are subjected to a smaller amount of sway. They are effective for buildings up to about 60 to 70 stories.

• Outrigger structures: This structural system is characterized by the presence of a core (see Figure 1.13), either constituted by braced frames or shear walls, and horizontal cantilever outrigger trusses or

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Figure 1.12: Classification of tall building structural systems by Fazlur Khan (steel)Source: M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects,” Architectural Science Review, Volume 50.3, pp. 205-223. Redrawn by CTBUH

Figure 1.13: Example of concrete central core and steel frameSource: Dario Trabucco

19

girders connecting the core with the exterior columns. Lateral deflections and bending moments of the core are reduced when the building is subjected to horizontal loads as the outrigger opposes the rotation of the core, transferring tension and compression action to the windward and leeward columns respectively. They are effective for buildings up to about 150 stories.

The following structural systems can be defined as the second category, exterior structures:

• Tubes (framed tubes, braced tubes, bundled tubes, tube-in-tube): These systems are comprised of closely spaced columns placed in the building perimeter that are connected to deep spandrel beams at each floor level, arranging a three-dimensional system that uses the entire building perimeter to resist lateral loads. They

are effective for buildings up to about 110 stories, depending on the type (see Figure 1.15).

• Diagrids: If the vertical columns of a traditional tube structure are replaced with closely spaced diagonals in both directions, a diagrid is obtained. Diagrid structures provide both bending and shear rigidity without the need of a core. They are effective for buildings up to about 100 stories, depending on material (steel or concrete).

• Exoskeletons: The exoskeleton represents a lateral load resisting system that is located outside of the building, away from the façade. They are effective for buildings up to about 100 stories.

• Space truss structures: These are modified braced tubes with diagonals connecting the exterior to the interior instead of being located parallel to the façades in plan. They are effective

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Figure 1.14: Interior structuresSource: M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects,” Architectural Science Review, Volume 50.3, pp. 205-223. Redrawn by CTBUH

Figure 1.15: “Bundled tube” system example: Willis Tower, 1974, ChicagoSource: Marshall Gerometta

20

for buildings up to about 150 stories (see Figure 1.17).

• Megaframes: These structures include megacolumns, braced frames of large dimensions at the building corners, linked by multistory trusses. They are effective for buildings up to about 160 stories, depending on material (steel or concrete).

In this study, two ranges of height for tall buildings are analyzed in order to cover the most typical structural systems for high-rise buildings between 1961 and 2010 (data provided by CTBUH Journal, Issue II, 2010).

The first range includes buildings 200 meters to 300 meters in height, or similarly from 50 to 60 stories. Of the 19 buildings within this threshold that were completed in the mentioned period of time, five of them present a framed tube structural system, five have diagonalized structures (trussed tube, diagrids, or braced frames),

four use tube-in-tube structures, and four use a core and outrigger system, leaving only one hybrid structure example (combined use of two or more structural systems, e.g. diagonalized outrigger core). Most of these buildings were built with steel and were completed between 1960 and 1980, while few were built with concrete or composite.

The second range includes buildings 400 meters to 500 meters in height, or similarly from 100 to 110 stories. Only eight buildings are found within this range, half of which were completed between 2001 and 2010 with composite structures (diagonalized, hybrid, core/outrigger, and tube in tube). The second half are represented by steel structures (bundled tubes or framed tubes) completed between 1961 and 1980.

Looking at the presented data, some trends can be found: tall buildings between 200 meters and 300 meters mostly utilize a structural system

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Figure 1.16: Exterior structuresSource: M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects“, Architectural Science Review, Volume 50.3, pp. 205-223 Redrawn by CTBUH

Figure 1.17: “Space truss” system example: Bank of China, 1989, Hong KongSource: (cc-by-3.0) WiNG

21

realized with tubes, typical of the period of time in which they were constructed. With an increase in height (400 to 500 meters), structural systems get more diverse, with core and outrigger systems along with hybrid structures playing an emerging role.

1.3 Foundation Types

The high pressures imprinted on the ground by a tall building could originate some problems in the designing and in the construction of the foundations. They represent crucial elements in the design process, since they could support about, or more, 0.5-0.8 MPa.

However, some foundations typologies are recurrent for high-rise buildings design, including: pile, combined piled-raft and slab and increased stiffness box foundations (Ukhov, 2003).

In order to select a suitable foundation system for a tall building, several factors

must be taken into consideration (Chew Yit Lin, 2001), among the most important of which are soil conditions, load transfer pattern, shape and size of the building, site constraints, underground tunnels and/or services, and environmental issues.

There are two main types of foundations for tall buildings: shallow and deep, as described here below.

• Shallow foundations: These transfer loads to the earth just below the base of the substructure’s column or wall. Among them, mat and spread footings (isolated footings such as column footings, strip footings such as wall footings and combined footings) are considered the most common. These foundations are suitable for sites where soil conditions are adequate, since highly concentrated and eccentric column loads require a large foundation thickness.

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• Deep foundations: They transfer the load to a point far below the substructure. They are suitable where loads must be transferred in layers located below the ground surface due to the lower load bearing capacities of the soil near the surface.

The most common types of deep foundations are piles and caissons, as described below:

• Piles: These behave like columns embedded in the ground and transfer the load to a lower level of the subsoil. A wide variety of materials and installation processes are used in the piles. They can be classified based on the technology used in their construction. Non-displacement piles are those in which a column of soil is removed and replaced with steel reinforcement and wet concrete. Displacement piles are driven in the soil, but they are losing popularity since the driving process causes noise, vibration, and dust (Chew Yit Lin, 2001). This category includes precast reinforced concrete piles, steel H-piles, composite piles, etc. Based on the load resistance system used in each case, piles can be end bearing (when the load on the pile is transferred to the soil layer located at the head pile level) or friction (when the resistance is mainly provided by the adhesion or friction action of the soil around the perimeter).

• Caissons: They are shells or casings that, when filled with concrete, form a structure similar to a cast-in-place pile but larger in diameter. They allow the load to spread over an area large enough to meet the soil bearing capacity. Their lengths are set based on a distance in which a

satisfactory bearing stratum such as rock, dense sand, gravel, or firm clay can be reached. Caissons can vary, from the technologies adapted in them, to various types: bored caisson, gow caisson, socketed caisson, box caisson, and pneumatic caisson.

Poulos (Poulos, 2011) highlights how the design of foundation systems for high-rise buildings involves particular requirements based on the cyclic nature of wind, earthquakes, and wave loadings; moreover, differential settlements, both within the high-rise footprint, and between high-rise and low-rise areas, should be controlled by the design.

According to some authors (Poulos, 2011) (Quick, 2005), high-rise buildings are usually founded on some form of piled foundation which is exposed to a combination of vertical, lateral, and overturning forces. Particular attention is paid to the piles and especially Combined Pile-Raft-Foundation systems (CPRF), which are the predominant types used nowadays.

In CPRF system, loads are transferred by the skin friction and end bearing of the piles as well as the contact pressures of the raft foundation (bearing pressure). While in most cases a raft foundation provides the required factor of safety by itself, serviceability might not be guaranteed. Therefore, piles are associated to a raft, creating a composite load bearing system that benefits from the control of settlements accomplished with piles that provide most of the stiffness at serviceability loads, with the additional capacity (at ultimate loading) provided by the raft.

In order to give an approximation for the amount of concrete required in a CPRF system, a 77 meter tower situated in

Frankfurt, Germany used 0.5 m3 of concrete per m2 of building area, which comes out to 143 m3 of concrete per floor.

In Shanghai Tower, a 632-meter supertall tower in China according to the data on CPRF material take offs provided by Si et al. (2012) and the building dimensions provided by CTBUH (128 floors, 420,000 m2), 0.24 m3 of concrete is used per m2 of building area, which comes out to 785 m3 of concrete per floor.


23Tall Buildings Today | © Council on Tall Buildings and Urban Habitat

2.0 Sustainability and Tall Buildings


Figure 2.1: Integrated wind turbine example: Bahrain World Trade Center, 2008, ManamaSource: (cc-by-sa) Ayleen Gaspar

26

Skyscrapers are often accused of being a non-sustainable building typology because they require a greater amount of energy to operate compared to a normal building, they require increased quantities of materials for their structures as a consequence of their height, and they involve a higher amount of embodied energy used to produce these materials. Indeed, tall buildings require more structural materials than lower buildings and they utilize additional features (such as elevators) that are not needed in shorter buildings.

The environmental sustainability issues of tall buildings became evident in 1973-1974 when the first energy crisis caused a rise in oil and energy prices in western countries. During the years following 1974, extensive analyses were carried out in North American cities to determine the actual energy performances of tall office buildings (Stein, 1977), while technical innovations were introduced to decrease their overall energy consumption (mostly in the field of mechanical ventilation and internal illumination), thus creating a new generation of efficient tall buildings. Since then, tall buildings have undergone

buildings with extensive use of “visible” sustainable principles exist today. This is mainly due to the increased construction and management costs associated with developing such buildings, which need to be addressed by drivers beyond basic design factors. In fact, most high performance buildings have been built using less visible – but nonetheless effective – measures, rather than bold, outstanding innovations with very high capital costs. Thanks to the use of modern curtain wall systems, the exploitation of natural ventilation, energy efficient

major transformations that have changed not only the energy needed for their daily operations, but their architectural appearance as well.

Sustainability has clearly become a major driver of change in tall building development, and the integration of “green” solutions has resulted in a whole new family of towers (Yeang, 1996) that have inspired the introduction of a new vernacular for tall buildings (Wood, 2007) (Yeang, 1996). However, green architectural features have been used sporadically, and only a few tall

2.0 Sustainability and Tall Buildings

“Sustainability has clearly become

a major driver of change in tall building

development...”

| Sustainability and Tall Buildings © Council on Tall Buildings and Urban Habitat

Figure 2.2: Photovoltaic façade example: Palazzo Lombardia Building, 2011, MilanSource: Dario Trabucco

Figure 2.3: Integrated wind turbine example:Pearl River Tower, 2013, GuangzhouSource: Tansri Muliani

27

elevators, combined heat and power units, and intelligent building control systems (Ali & Armstrong, 2008), buildings consume far less energy than their 1970s predecessors (Oldfield, et al., 2009).

With a decrease in the energy consumption of tall buildings, a new issue arose, requiring the renewed attention of building experts and professionals: life cycle thinking. In fact, buildings consume energy and cause emissions, not only during use, but throughout their entire lives. From material production, construction, and maintenance, to demolition and the recycling of building materials (or disposal into a landfill), they consume energy as well as emit gases and substances into the environment. All of these phases have an impact on the total life cycle performance of a tall building, and one should make sure that the benefits of an energy reduction strategy (such as the use of a double skin façade) are carefully studied, so as not to create bigger drawbacks for other environmental characteristics; for example, by augmenting the initial embodied energy that offsets the benefits created in daily energy consumption.

2.1 Energy Consumption of Tall Buildings

The energy consumption of tall buildings evolved significantly over the past 100 years, reaching a maximum before the first energy crisis and then diminishing remarkably (Oldfield, et al., 2009). The theoretical limit of 90 kWh/m2 per year mentioned by Raman (Raman, 2001) excludes the presence of on-site energy generation. Thanks to the exploitation of renewable sources such as photovoltaic

cells or wind turbines, tall buildings can be not only efficient in consuming energy, but also in producing it.

Photovoltaic panels are being installed on a number of tall building’s rooftops, such as the Euro Tower in Rome, or façades, as on the Palazzo Lombardia in Milan (see Figure 2.2), but their effect is limited to the surface of their external envelopes, which are quite limited when compared to the building’s usable floor area. Therefore, their energy production rate is small when compared to the high energy consumption of the whole building.

Only a few tall buildings with integrated wind turbines have been built; the Strata Tower in London, the Bahrain World Trade Center in Bahrain, and the Pearl River Tower in Guangzhou (see Figure 2.3) are probably the most relevant examples. Generally speaking, renewable energy production systems are not as effective as expected, and cause many drawbacks to the comfort of a tower’s inhabitants (noise, vibrations, etc.). These drawbacks prevent their full exploitation and require mitigation measures (Killa & Smith, 2008) in the use of such systems, which have to be carefully assessed from a life cycle perspective.

Sustainability and Tall Buildings | © Council on Tall Buildings and Urban Habitat

Figure 2.3: 30 St. Mary Axe, 2004, LondonSource: Phil Oldfield

28

Leung and Weismantle (Leung & Weismantle, 2008) analyze possible sources of sustainability for supertall buildings that are achievable thanks to their height. Their study indicates that the gains through such measures are not enough to justify pursuing height for the sole sake of sustainability.

The ultimate goal of the above mentioned sustainability measures (and other energy efficiency or on-site production solutions) is to realize a Net Zero Energy Building (NZEB), which would establish a balance between what the building receives from the grid, and what it returns to the grid during peaks of on-site energy production. So far, all attempts at reaching the NZEB

goal for tall buildings have failed, due to: the excessive costs of high-performing systems, a lack of confidence and familiarity with such technologies (Chambers, 2014), and external vetoes (Frechette & Gilchrist, 2008). Even if the objective of creating a Net Zero tall building was realized – although this possibility is still debated – it would be far from a real “Zero Energy Building” (where a balance is established between what a building consumes in its life cycle – thus including the production of materials and construction – and what the building feeds back into the grid). In fact, energy reduction measures always come with an energy cost that is difficult to offset by on-site production, even on a small, simply-constructed building, making

Energy Consumption [kWh/m2 per year]

Temperate Climate[Sydney]

Tropical Climate[Singapore]

Boilers 5.5 2.9% 0.0 0.0%

Chillers 13.4 7.0% 56.9 23.8%

AHU Distribution Fans 16.0 8.4% 17.5 7.3%

Water pumps 6.8 3.6% 10.3 4.3%

Cooling Tower Fans and Condenser 4.8 2.5% 12.1 5.1%

Package Unit 1.6 0.8% 1.6 0.7%

Tenant Condenser 3.9 2.0% 3.9 1.6%

Auxiliary Ventilation Fans 6.2 3.3% 6.2 2.6%

Total Base Building HVAC 58.2 30.6% 108.5 45.3%

Common Area Lighting 7.4 3.9% 7.4 3.1%

Lifts 13.7 7.2% 13.7 5.7%

Domestic Hot Water 2.2 1.2% 1.1 0.5%

Diesel Generator Testing 1.3 0.7% 1.3 0.5%

Hydraulic and Fire Pumps 1.9 1.0% 1.9 0.8%

Miscellaneous Non-Tenant Loads 2.0 1.1% 2.0 0.8%

Total Base Building Energy use 86.7 45.6% 135.9 56.7%

Tenancy Lighting 34.3 18.0% 34.3 14.3%

Tenancy Receptacle Equipment 69.3 36.4% 69.3 28.9%

Total Building Energy 190.3 100.0% 239.5 100.0%

Table 2.1: The Energy Consumption of a 60-story Office Building in Both Temperate (Sydney) and Tropical (Singapore) ClimatesSource: Partridge, et al., 2012; updated by CTBUH

“Because of the relatively recent

‘introduction’ of the notion of Life Cycle Assessment... there

are no comprehensive Life Cycle Assessments with real verified data

for tall buildings.”


29

SourceAssessment

Method(see section 3)

StructuralSystem

TotalEmbodied Carbon

[kg CO2/m2 GFA]

Embodied Carbon Structural Frame[kg CO

2/m2 GFA]

TotalEmbodied

Energy[GJ/m2 GFA]

Embodied Energy

Structural Frame[GJ/m2 GFA]

BuildingHeight[story]

Foraboschi et al. 2014ProcessAnalysis

Steel Frame + Concrete Core

- - - 3.15 40

- - - 3.94 50

- - - 3.77 60

Concrete Frame

- - - 2.20 40

- - - 2.57 50

- - - 2.46 60

Kofoworola and Gheewala 2009

ProcessAnalysis


- - 6.80 5.30 * 38

Oldfield 2012ProcessAnalysis

Steel Diagrid 955 340 - - 40

Trabucco 2011 Input/Output Steel Frame - - 23.20 - 40

Trabucco 2012Hybrid

AnalysisConcrete Frame - - 15.70 4.23 40

Treloar et al. 2001 Input/Output

Concrete Core + Composite

Column- - 18.00 11.70 42


- - 18.40 11.60 52

* Data not explicitly indicated in the paper, extracted through interpretation.

Table 2.2: Previously published studies on the life cycle assessments of tall buildingsSource: CTBUH

it an almost impossible task when it comes to buildings as complex as skyscrapers.The energy consumption of a 60-story office building in both temperate (Sydney) and tropical (Singapore) climates can be divided as described in Table 2.1 (Partridge, et al., 2012). Interestingly, the results of the mentioned study show that the design team is responsible only for a small share of the total energy consumed by the building. In fact, the tenants’ office equipment (PCs, printers, etc.) can be responsible for a large portion of a building’s total energy (approximately 30% of the energy consumed in an office building is used by this equipment). As most of the electricity used by such equipment is turned into heat, HVAC

energy is needed to control these excessive heat gains, both from the equipment and other internal sources (especially for towers in a tropical climate).

A similar concept can be applied to the consumption of the lighting energy in the space, though the design team can play a more important role in this aspect by choosing proper orientation, building shape, façade system, and by taking advantage of the available daylight to prevent the unnecessary use of artificial lighting during the day.

Only a few of the above mentioned aspects related to a building’s energy use are really connected with building height; lifts,

water pumps, and HVAC fans are among those few. Other aspects (heating and cooling, domestic hot water, etc.) are more connected with the location and size/area of the building rather than its shape.

Even the carbon releases that are related to the energy mix on the grid can be reduced by choosing to install energy conversion systems (such as fuel cells) in the building that reduce the need to utilize grid energy. When heating is needed in the building, using the heat generated in the space by the conversion systems as a heating source can also help reduce the energy and carbon impact of a building.

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consumption of 0.23 GJ/m2 per year. The building is entirely made of concrete, with a PVC lighting system on the floor slabs.

Kofoworola and Gheewala (Kofoworola & Gheewala, 2009), studied a 38-story building in Thailand and found an initial embodied energy of 6.8 GJ/m2 GFA and a 0.86 GJ/m2 annual energy consumption. The structure in this case is made of a reinforced concrete core and steel frame and structural materials represent 77.8% of the total embodied energy (corresponding to ca. 5.3 GJ/m2 GFA).

Another paper presents the embodied energy or embodied carbon studies of existing or theoretical tall buildings, without benchmarking them against the total energy consumption of the building over its whole life cycle. A study on five buildings with different heights (3, 7, 15, 42, and 52 floors above grade) was performed using an input-output approach (Treloar, et al., 2001).

2.2 Embodied Energy of Tall Buildings

Because of the relatively recent “introduction” of the notion of Life Cycle Assessment, and as a consequence of the inherent complexity of tall buildings that makes the acquisition of the necessary data a challenging task, there are no comprehensive Life Cycle Assessments with real verified data for tall buildings. At the same time, a few studies have been published on the topic from a theoretical and academic perspective (see Table 2.2).

Oldfield (Oldfield, 2012) performed a Life Cycle Assessment for a 40-story office building in London (30 St. Mary Axe) and assessed the embodied carbon as 955 kg CO

2/m2 of gross floor area (1,159 kg CO

2Eq.

including building maintenance over 50 years of life phase) while the building’s total energy consumption per year stands at 95 kWh/m2 of electricity and 120 kWh/m2 of gas which equals to 74 kg CO

2/m2 of

gross floor area each year.

Oldfield takes into account the anticipated reduction of CO

2 intensity in the UK’s

electricity mix, and the final CO2 emission

during a 50-year life is 3.5 tons of CO2 per

m2. However, if the CO2 content from the

electricity production is kept at today’s value, the final carbon content would be 3.7 tons of CO

2 per m2 of the gross area.

The studied building has a steel diagrid structure and concrete is used only on the floor slabs. Trabucco (Trabucco, 2011) estimates the total embodied energy of the same building to be 23.2 GJ/m2 GFA and the energy consumption to be at 0.43 GJ/m2 per year.

Another study by the same author (Trabucco, 2012) on a 160-meter-tall building in Milan presents an initial embodied energy of 15.7 GJ/m2 GFA (4.23 GJ/m2 for the main structural components) compared with an energy


31Sustainability and Tall Buildings | © Council on Tall Buildings and Urban Habitat

3.0 Life Cycle Assessment


34

“...Life Cycle Assessment (LCA) is a methodology

aimed at assessing the environmental

consequencesof human actions,

particularly the production of goods.”

or on a process analysis. Such systems try to take advantage of the positive aspects of the two main methods by combining them to perform a quick, comprehensive, and detailed LCA analysis. Hybrid systems are still relatively under development but they seem to be very promising for the future (Zamagni, et al., 2008).

For the purposes of this study, a process-based analysis was adopted, as described in the International Reference Life Cycle Data System Handbook (JRC, 2010), a handbook released by the European Union’s Joint Research Centre, Institute for Environment and Sustainability, to guide users through the steps described in more general terms by ISO Norm 14044:2006.

3.1 Explanation of ISO LCA

ISO Norms 14040:2006 and 14044:2006 are the reference standard for the LCA. According to ISO 14040:2006 (see Figure 3.1), a LCA is composed of four phases:

• Goal and scope definition: the definition of a study goal indicates whether the analysis is meant to simply provide a data set for a process – thus a Life Cycle Inventory (LCI) is its main deliverable – or a complete LCA analysis in which the Life Cycle Inventory is interpreted and compared to similar results for other processes or goods. The goal definition also identifies the intended purpose of the study (i.e., comparison of similar products) and the target audience. In the scope definition, the subject of the analysis is identified and described in line with what was stated in the goal definition. This includes the identification of the system boundaries and the functional unit; the analysis on the consistency of the methods; assumptions and

Developed during the 1990’s, Life Cycle Assessment (LCA) is a methodology aimed at assessing the environmental consequences of human actions, particularly the production of goods. In the past two decades, LCA analysis has become more and more popular in all disciplines, including architecture and engineering. Despite the fact that LCA has been used for thousands of research projects analyzing the environmental characteristics of materials, components, and even entire buildings, and is widely described in books and scientific publications, doubts and criticisms still exist in the scientific community about the effectiveness and accuracy of LCA methods in accounting for all environmental characteristics of buildings and the built environment (Lenzen, et al., 2004) (Zamagni, et al., 2008).

There are three main methodologies found in literature for performing a LCA (Treloar, 1998):

1. Process-based LCA: In a process-based assessment, the process to be analyzed is divided into all of its sub-processes. The inputs and outputs of each sub-process are quantified and the process analysis is repeated on all of the inputs, tracing the processes back to a “cradle,” where raw materials are excavated or harvested. This method has several problems, most notably concerning the arbitrary process of defining the boundaries of the analyzed system (to decide which processes are to be included or excluded from the analysis) and the availability and reliability of information regarding upstream processes. It is also a very time consuming and complex method. On the other hand, the process-based analysis is notable for its specificity and precision when it comes to detailed product studies.

2. Input-output LCA: In input-output assessment, all production inputs are converted into economic factors using industry-aggregated data on economic interchanges. All of the infinite material and non-material upstream inputs are included in the analysis using a mathematic algorithm. This method has been adapted from the environmental analyses that emerged from the research developed by Nobel Laureate W. Leontief in the 1940s. The problem with this method is that it uses industry-wide average data, and therefore is not specific to a single product, site, or country, and the production processes and technologies for the same product can be very different in different parts of the world. The positive aspect of this method lies in its ability to assess the seemingly infinite upstream processes with a quick, simple calculation method.

3. Hybrid LCA: Hybrid systems can either be based on an input/output analysis

3.0 Life Cycle Assessment

| Life Cycle Assessment © Council on Tall Buildings and Urban Habitat

Figure 3.1: Life Cycle Assessment Framework from ISO 14040:2006Source: CTBUH

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Life Cycle Assessment Framework

Goal Definition

Scope Definition

Inventory Analysis

Interpretation

ImpactAssessment

data; and finally, the declaration of the results‘ reproducibility.

• Inventory analysis: during this phase, all inputs and outputs of the process are acquired and described in line with the goal and scope definitions. It is usually the most time-consuming phase of a LCA, as it requires collecting and measuring a large quantity of data, which often comes from external sources. It is from the accuracy and completeness of the LCI that a LCA study gains its quality.

• Impact assessment: The Life Cycle Impact Assessment (LCIA) is the phase in which all inputs and outputs to the process collected during the LCI phase, are converted into impact indicators. Impact indicators are the tools that measure the impact of an analyzed process on target categories such as human health, the natural environment, and natural resources.

• Interpretation of results: The interpretation of results is often the most interesting and “proactive” phase of a LCA, as it gives recommendations on how to improve a process or selects the better process when two processes are compared.

3.2 Definition of the Goal of the Study

The intended application of this study is to inform the community of professionals and researchers specializing in tall buildings on the environmental performance of the most common structural systems (reinforced concrete, steel and composite structural alternatives) by providing the most accurate, up-to-date analysis on two key impact categories: Global Warming Potential (GWP) and Embodied Energy (EE). The limitations of this study are represented by the fact that only

two impact categories (GWP and EE) are considered here, while other impact categories may lead to different results. Similarly, the obtained results are influenced by the quality of the information used, both in terms of environmental data (i.e., the “quality” and representativeness of the environmental data contained in the international databases used in the study) and data completeness (for example, environmental data on the end-of-life of tall buildings simply doesn’t exist, and had to be collected specifically for this research). The studied scenarios are representative of the most common structural systems for buildings of the height here considered.

This research is a complete Life Cycle Assessment of structural systems for 60- and 120-story buildings.

The main reason to conduct this study is that there is a lack of reliable and comprehensive information on the environmental impacts of various structural systems and materials for tall buildings, as well as the impacts of the construction phase on such projects. Also, a comparison on the relative importance of selecting various structural materials and structural systems for a tall building is needed. The intended audience of this public study is the community of tall building experts involved in the

Life Cycle Assessment | © Council on Tall Buildings and Urban Habitat

Figure 3.2: 300 North LaSalle, 2009, ChicagoSource: Marshall Gerometta

36

choices for the construction of tall buildings. The main deliverable of this study is represented by a Comparative Assertion LCA Study, which will identify the most and least convenient structural scenarios for a tall building from an environmental point of view, so as to quantify the environmental impact of the relative sector in the building industry.The study evaluates only the above-grade structural system for tall buildings of a given shape that differ in terms of height (246 meters for the 60-story scenario and

490 meters for the 120-story scenario), and are ideally located in Chicago, USA. Considerations are therefore valid only for the given environment and under the prescriptive characteristics detailed further on. However, considerations derived from the results of this study can be applied to buildings of different heights, shapes, and locations from the studied building, provided that the variables remain within reasonable limits of the parameters in this study.

As mentioned above, the system being analyzed is the above grade structural system of a tall building. The results will be presented considering the whole structure of the buildings, which represents the functional unit for this study.

The scope of this study consists of the identification of the most sustainable structural system for tall and supertall buildings through a Life Cycle Assessment. Two different impact categories considered for this study are Climate Change and Resource Depletion, with Global Warming Potential and Embodied Energy as their selected indicators.

Fay et al. (Fay, et al., 2000) define Embodied Energy (EE) as “the direct energy purchased to support the (production) process under consideration, plus the indirect energy embodied in the inputs to the process.”

Global Warming Potential (GWP) is defined as “the ratio of the time-integrated radiative forcing from the instantaneous release of 1 kg of a trace substance relative to that of 1 kg of a reference gas” (Shine, et al., 2010), which corresponds the measure of how much heat a greenhouse gas traps in the atmosphere compared to the amount of heat trapped by a similar mass of carbon dioxide.

ownership, development, design, planning, construction, operation, maintenance, and research of tall buildings. The study was commissioned and sponsored by ArcelorMittal, the world’s largest producer of structural steel profiles and reinforcing bars for concrete construction.

3.3 Scope Definition of this Study

As stated in the goal definition, the intent of this study is to provide a preliminary evaluation of the different structural


37

The system boundaries of the study are extended to the whole life of the building structure, from the production and transportation of materials to the building site, through the construction and use phase, and including the demolition of the building as well as the recycling potentialities of the various components.

The data used in the Life Cycle Inventory (LCI) has been collected with the highest level of accuracy within the time and budget constraints of the research. Water consumption is not considered as an indicator in the study, regardless of the quantity. A detailed description of the methodology used to acquire the relevant information and prepare the LCI is described in the following sections of this report.

For the interpretation and analysis of the results, this study considers three different parameters in the structure of a tall building:

• Height: the impact of building height is assessed by comparing buildings of 60 and 120 floors. According to Fazlur Khan’s “premium for height,” a building twice the height of another will have more than twice the structural materials of the shorter building due to the exponential increase of the lateral forces acting on its structure (Kahn, 1969).

• Structural material: steel, reinforced concrete, and composite (steel and concrete) materials are considered in the study as the structural materials of a building. These represent the most commonly used materials for the structural components of a tall building today.

• Structural scheme: several structural alternatives are considered by the study, covering the diverse types of

tall building structures built today (Ali & Moon, 2007).

The structural schemes and materials are combined to recreate realistic design options. All plausible combinations of structural schemes and materials are studied for the two different heights, even if, in some cases, the resulting design would not be a common choice for a real building.

The cut-off criteria, coming from the comparative scope of the main deliverables, were set after an initial LCI model was modeled with the software used in the research (GaBi 6.0). This has allowed for the contribution of each flow to be identified, in addition to setting the cut-off criteria. The cut-offs pertaining to each specific part of the analysis will be described in their specific sections.

Even though it is difficult to set an accurate life span for structural systems, literature shows that a 100-year time frame is a reasonable life for such complex structures. Despite this, the research has evidenced a progressive reduction in the life span of buildings, including tall buildings. This aspect is more extensively described in the section of this study that covers the end-of-life of tall buildings. It is important to mention that the final results of the research will be normalized for life cycles of 50 and 100 years. This will make the results comparable to similar research efforts on the energy consumption of office buildings and with the internationally adopted energy classification systems.

3.4 Scenario Analysis and Identification of Functional Units

The purpose of this research is to study the whole life cycle of tall building structures and to compare the environmental effects

caused by variations in height, structural material, and structural scheme.

The initial idea was to use data derived from real buildings to assess the environmental impacts of the different variations. The data were collected from the design firms for a number of office buildings recently completed in downtown Chicago. This strategy proved to be unreliable, mainly because the number of variables included in the analysis would increase excessively, while other random facts (design, shape, soil conditions, exposure to winds, etc.) that are not considered in the study would have affected the results, making them impossible to compare with each other.

To limit the analysis to the three factors studied in this research (height, structural material, and structural scheme), the comparison had to be made among very similar designs, so as to keep the other variable’s effects minimal. Therefore, a different strategy was adopted and the focus was

“The purpose of this research is to study...

tall building structures and to compare the

environmental effects caused by variations in height, structural

material and structural scheme.”


38

and core penetrations on each side of the core that must be inserted via 2.5- by 3-meter openings.The shorter design would represent a normal office building of medium height in most global cities, if it were to be built. Its construction is quite standard and doesn’t require any particular design feature.

On the contrary, the taller design would become the fifth-tallest building in the world and would have approximately one and a half times the gross floor area of the Burj Khalifa, the world’s current tallest building. This design, though realistic, does not represent a standard building of its height category. A building of this size would have been treated with an iconic architectural approach (Abdelraq, Baker, & Chung, 2004) in order to obtain constructive advantages from an informed design (Weismantle, et al., 2007). Also, as in the case of other supertall buildings (Baker, et al., 2007), various means of structural optimization would have taken

switched from a real case study to a fictitious building prototype inspired by a real building, which represents the current building practice for producing tall office buildings: 300 North LaSalle in Chicago, a 239-meter, 59-story office building completed in 2009 (see Figure 3.2).

The building has a rectangular floor plan and a net rentable area of approximately 120,000 m2. Its structural system consists of a central concrete core and external steel columns connected via outriggers. The floor system used in the building was a composite solution that consisted of concrete slabs on metal decking.

With this in mind, two main categories of design scenarios were studied: the first category for a building of 246 meters in height (59 levels above grade), and the second category for a tower of 490 meters (119 levels above grade). The shorter design is directly inspired by a “simplified” geometry of the 300 North LaSalle building. The taller design was modeled by

scaling up the smaller scenario, keeping within realistic proportions, especially in terms of core-to-window depth: it was kept at 13.5 meters representing a standard value in North American modern office buildings (see Figure 3.3). A realistic core size was also defined based on similarly tall skyscrapers, resulting in a NRA/GFA ratio of 75% (Trabucco, 2008).

Having imposed the height, core take-up of the gross floor area, the floor plan aspect of 2:3 (like the shorter building), and the constant core to width ratio of 13.5 meters, a tower with a floor plan area of 75 by 50 meters was created (see Table 3.1).

The 60-story tower has a floor plan of 60 by 40 meters including structural elements. An area of 35 by 13 meters in the lower 40 stories and of 16.5 by 13 meters in the upper portion is allocated for the core programming of vertical services, lifts, etc. Outriggers are designed at the 40th floor. Assuming three interior core cross walls below the outrigger level; the outer two cells drop off after the outrigger level, at 2/3 the tower height (40 stories).

The 120-story tower has a floor plan of 75 by 50 meters including structural elements, and an area of 55 by 23 meters in the lower 40 stories and 33 by 23 meters in the upper 80 stories are allocated for the core programming of vertical services, lifts, etc. It is imagined that three interior core cross walls are located below the outrigger level; the outer two cells drop off after the first outrigger level, at 1/3 the tower height (40 stories). The core program reduces after the first service level (40th floor) with added columns.

In both cases, floor-to-floor height is four meters tall, with the exception of the lobby (6 m), mechanical floors (8 m),

Parameter

246 m scenarios

(60-story equivalent)

490 m scenarios(120-story

equivalent)

Built Floor Area 144000 m2 450000 m2

Floor Plan Dimensions 40 x 60 m 50 x 75 m

Tower Slenderness 6:1 10:1

Lease Span (core to window

depth)13.5 m 13.5 m

Floor-to-Floor Height 4 m 4 m

Lobby Height 6 m 6 m

Mechanical Floor Height

8 m 8 m

Table 3.1: Data of the Case Studies Used for this ReportSource: CTBUH

“The inventories obtained for the

same scenario by two different firms should

not be compared to determine a more

efficient design or a ‘better’ solution.”


39

place (such as tapering, variations of its geometry to “confuse” the wind, use of tuned mass dampers, etc).As a result of this “boxy” and non-optimized shape, the 490-meter-tall scenario might result in being oversized, from a structural perspective, when compared to real tall buildings of similar height. Bearing this in mind, it was decided to proceed with the study of these scenarios in order to assess the environmental impacts connected with increases in the height of the building. As previously mentioned, the results of this study will be refer to the building as a whole, representing the functional unit of this study.

Environmental impacts “per net square meter” or “per floor” are not considered in this study, as buildings are often built to occupy the maximum volume

246 m Scenario

490 m Scenario

Interior Structures (the central core

acts as primary element to resist lateral loads)

Concrete Core with Steel Frame Scenario 1a Scenario 4a

Concrete Core with High Strength Steel Frame Scenario 1b Scenario 4b

Concrete Core with Composite Columns Scenario 1c Scenario 4c

Concrete Wide and Shallow Beams Scenario 2a Scenario 5a

Concrete Narrow and Deep Beams Scenario 2b Scenario 5b

Exterior Structures (the exterior diagrid system

acts as primary element to resist lateral loads)

Steel Diagrid Scenario 3a Scenario 6a

High Strength Steel Diagrid Scenario 3b Scenario 6b

Composite Diagrid Scenario 3c Scenario 6c

Table 3.2: Scenario Codes for the Case Studies Used for This ReportSource: CTBUH

Life Cycle Assessment |

Figure 3.3: Configurations for the 60- and 120-Story VariationsSource: CTBUH

Scenario 3c & 6cComposite Diagrid(Steel grade 345MPa)

Scenario 3a, 3b, 6a & 6b Steel Diagrid

(a = Steel grade 345 MPab = Steel grade 450 MPa)

Scenario 1c & 4cConcrete core & Composite frame

(Steel grade 345MPa)

Scenario 2a, 2b, 5a & 5bAll Concrete structures

(a = with wide and shallow beamsb = with narrow and deep beams)

Scenario 1a, 1b, 4a & 4bConcrete core with Steel frame

(a = Steel grade 345MPab = Steel grade 450MPa)

4.00

4.00

8.00

6.00

170.

00

334.

00

490.

00

4.00

4.00

13.0

013

.00

23.0

023

.00

50.0

050

.00

40.0

040

.00

35.00

55.0075.00

16.50

60.00

6.00

8.00

246.

00

17.0

0

33.0075.00


40

construction and use phase (subsequently excluded from the results), the demolition of the building, and the recycling potentialities of the various components (presented as additional information since it is beyond the system boundaries set by European Norm 15978 “Sustainability of construction works – Assessment of environmental performance of buildings – Calculation method”) (European Norm, 15978:2011).

3.6 Structural Systems and Materials

The scope of the analysis in this study also includes the assessment of the role that different structural materials and systems play in the Life Cycle Assessment of tall buildings. Even if virtually all combinations of materials and schemes are possible and all buildings somehow act as “unique” structures,

two main families can be identified: interior and exterior structural systems based on the location of the primary lateral load-resisting system (Ali & Moon, 2007). The 16 scenarios imagined for this study are defined, including all possible configurations: interior and exterior structures (see Table 3.2); steel, concrete, and composite constructions; and eventually, two different steel grades of 345 MPa (50 ksi) and 450 MPa (65 ksi); and four concrete grades between 30 MPa (4 ksi) and 70 MPa (10 ksi).

3.7 Floor Systems Used

The floor systems adopted in this research represent the most common technologies used in tall steel or concrete buildings. The floor plate spans and programming of the study towers generally conform to structural bay depths that may be

allowed by local codes, so the net usable area is typically a consequence, not an objective, of a building’s design. The study omits the occupancy phase of the building, and it is thus not applicable to a specific duration of use, as research evidence showed that the impact of the structural components during a building’s use phase was not measurable, and the environmental performance of the building is predominantly controlled by other aspects of the design (function, curtain wall performance, MEP systems, etc).

3.5 System Boundaries

The system boundaries of the study (see Figure 3.4) are extended to the whole life of the building structure, from the production and transportation of materials to the building site, through the

Product Stage

(A1 – A3)

EN15978 System Boundary

Use(B1 – B7)

End of Life(C1 – C4)

Benefits and Loads Beyond theBuilding Life Cycle

B6: Operational Energy(Hvac, Hot Water & Lighting)

Operational Energy(All remaining energy

used within the building)

Transport ofConstruction

B7: Operational Water

A1:

Raw

Mat

eria

ls E

xtra

ctio

n

B1: U

se

C1:

De-

cons

truc

tion

/ Dem

oliti

on

Reus

e

A2:

Tra

nsp

ort

B2: M

aint

enan

ce

C2:

Tra

nsp

ort

Reco

very

B4: R

epla

cem

ent

A3:

Man

ufac

turin

g

B3: R

epai

r

C3:

Was

te P

roce

ssin

g

Recy

clin

g

C4:

Dis

pos

al

Exp

orte

d En

ergy

B5: R

efur

bis

hmen

t

A4:

Tra

nsp

ort

A5:

Con

stru

ctio

n &

Inst

alla

tion

ConstructionStage

(A4 – A5)

Figure 3.4: EN15978 System BoundarySource: CTBUH

(D)

Labour


41

considered for office programming. The information provided, though, is not exclusive to commercial office construction. The systems considered could equally be used for hotel, residential, and mixed-use towers.

Users of this study will need to make informed decisions on the comparative use of its data, based upon the selection of floor framing systems and floor spans for their specific projects.

Three different alternatives were imagined: one steel-concrete composite solution that was adopted on all structures with steel or composite columns, and two alternatives to be used only on the “all-concrete” scenarios.

The composite floor system was defined based on a 7.5 cm corrugated metal deck with a 6.5 cm collaborative slab of concrete that embeds a welded wire fabric and additional reinforcing rebar (when required). Shear studs directly connect the concrete to the steel beams underneath, thus creating a composite floor system that represents the common floor system for tall buildings. Gravity beam quantities were not calculated by the design firms, who designed vertical structures. Instead, they were derived using average values from the real case study and as a reference for this research.

The concrete towers were studied considering two different floor variations: one with narrow and deep concrete beams, and another with wide and shallow concrete beams. The narrow and deep design is made of a 15 cm-thick slab with 40 cm-wide and 45 cm-deep beams every three meters, while the wide and shallow floor scenario is based on a 22 cm-thick slab and band beams 45 cm-thick and 200 cm-wide, aligned with the columns.

3.8 Inventory of Materials

Methods for obtaining information in the Inventory of Materials are described below.

These topics are then covered at length in the sections that follow.Quantities of Materials

The analyzed system is represented by the functional unit (i.e., the structural system) delivered by the construction company to the other contractors that will transform the structural skeleton for future use. It does not include secondary non-structural components of the building, such as the exterior envelope enclosure, partition systems, finishes, and MEP systems.

Inputs to the analyzed system were modeled by attributing the material quantities to the supply-chain of the construction company, represented by the material suppliers and the transport companies that deliver the materials to the site. With the use phase being excluded for the above mentioned reasons, research considerations skip to the end-of-life scenario for a demolition company, whose “inputs” (energy) and “outputs” (emissions and debris) are quantified.

Production of Materials

All the above mentioned quantities were calculated thanks to the support of several industry leaders who voluntarily contributed to the research by modeling specific structural scenarios: Arup, Buro Happold, Halvorson & Partners, Magnusson Klemencic Associates, McNamara/Salvia, Nishkian Menninger, Severud Associates, Skidmore, Owings & Merrill, Thornton Tomasetti, Walter P Moore, Weidlinger Associates, and WSP USA. These structural engineering firms provided the structural material quantities on the basis of a document containing general design information for the scenarios, which itself was prepared with the support of Magnusson Klemencic Associates.

The document contained a description of the analyzed structural systems, the schematic layout and section of the structure to be designed, details of the

floor systems (designed by Magnusson Klemencic Associates), as well as the structural loads to be considered for the design of the vertical structures. Each scenario was assigned to two engineering firms.

The structural engineering firms contributing to this research were asked to design the buildings using their business experience, but were limited in terms of structural optimization (i.e., by adding tuned mass dampers). Consequently, the resulting inventories of materials are likely to be over-designed when compared to the inventories of equivalent tall buildings in the real world. Also, it is important to note that the inventories obtained for the same scenario by two different firms should not be compared to determine a more efficient design or a “better” solution.

Eight different configurations for the vertical structure were identified for the 60-story tower, and eight for the 120-story variation (see Table 3.2). A total of 16 scenarios were thus identified, with each scenario submitted to two design firms, so as to obtain 32 “bills of materials” that represent the basis of information for the subsequent phases of this research. The resulting quantities were integrated with data on the horizontal structural elements (i.e., floor beams, floor slabs, etc.) obtained from a comparison with buildings of the same size, function, and scale to those considered for the research. This phase regards steps A1–A3 (from raw material extraction to manufacturing) as described by EN 15978. The results of this section, directly derived from participating engineering firms, are presented in Table 3.3.

Especially for the taller scenarios, even within the rigid boundaries of the design document, significant differences existed in the solutions provided by contributing firms. Where there are no significant design variations, the LCA results from two engineering firms designing the same scenario will be presented as an average


42

Short Description

Scenario Number

(SF = Structural

Firm)

10 ksiConcrete

[t]

9 ksi Concrete

[t]

8 ksi Concrete

[t]

6 ksi Concrete

[t]

4-5 ksi Concrete

[t]

Steel Rebar

[t]

WeldedWire

Frame[t]

Steel Studs

[t]

Metal Decking

[t]

Steel Beams

[t]

Steel Columns

[t]

Steel Trusses

[t]

Fireproofing Spray

[t]

Normal Steel + Concrete Core

1a_SF 01 11.944 - 12,857 6,077 28,424 1,388 260 25 1,212 4,011 1,971 186 1,651

1a_SF 02 - - 7,608 12,036 28,424 957 260 25 1,212 3,949 1,614 333 1,651

High Strength + Concrete Core

1b_SF 01 11.944 - 12,857 6,077 28,424 1,388 260 25 1,212 4,011 1,840 186 1,651

1b_SF 02 - - 7,608 12,036 28,424 957 260 25 1,212 3,949 1,307 333 1,651

Concrete Core and Composite Frame

1c_SF 01 13.032 - 13,844 8,218 28,424 1,554 260 25 1,212 4,011 786 186 1,600

1c_SF 02 - - 8,758 13,761 28,424 1,122 260 25 1,212 3,949 667 333 1,600

All Concrete Wide and Shallow Beams

2a_SF 01 24.150 - 13,340 6,900 80,803 3,332 260 - - - - - -

2a_SF 02 5.962 - 31,464 8,280 80,803 7,481 260 - - - - - -

All Concrete Narrow and Deep Beams

2b_SF 01 24.150 - 13,340 6,900 58,939 3,281 260 - - - - - -

2b_SF 01 33.782 - 6,955 5,631 58,939 6,309 260 - - - - - -

All Steel Diagrid Normal Steel

3a_SF 01 - - - - 28,424 548 260 25 1,212 4,862 5,850 1,800 1,742

3a_SF 02 - - - - 28,424 548 260 25 1,212 4,156 2,050 4,970 1,742

All Steel Diagrid HS Steel

3b_SF 01 - - - - 28,424 548 260 25 1,212 4,756 4,250 1,700 1,742

3b_SF 02 - - - - 28,424 548 260 25 1,212 4,051 1,640 4,900 1,742

Composite Diagrid 3c_SF 01 - - - 13,617 28,424 778 260 25 1,212 4,848 3,050 1,900 1.600

3c_SF 02 6.049 - 5,221 3,243 28,424 1,188 260 25 1,212 4,236 610 1,490 1.600


4a_SF 01 76.864 - 23,242 64,209 83,543 7,424 764 75 3,563 11,861 25,923 2,641 4,844

4a_SF 02 144,744 - 29,938 - 83,543 10,683 764 75 3,563 11,608 19,369 5,125 4,844


4b_SF 01 76,864 - 23,242 64,209 83,543 7,424 764 75 3,563 11,861 25,923 2,641 4,844

4b_SF 02 144,744 - 29,938 - 83,543 10,683 764 75 3,563 11,608 16,420 5,125 4,844


4c_SF 01 85,130 - 32,563 81,793 83,543 8,028 764 75 3,563 11,861 5,526 2,641 4,702

4c_SF 02 179,399 - 38,511 - 83,543 10,560 764 75 3,563 11,608 3,538 4,990 4,702


5a_SF 01 104,871 - 65,368 40,242 237,496 17,064 764 - - - - - -

5a_SF 02 139,518 - 82,184 49,981 237,496 20,399 764 - - - - - -

All Concrete, Narrow and Deep

Beams

5b_SF 01 104,871 - 65,368 40,242 173,232 16,915 764 - - - - - -

5b_SF 02 139,518 - 82,184 49,981 173,232 21,330 764 - - - - - -


6a_SF 01 - - - - 83,543 1,611 764 75 3,563 18,062 14,850 54,900 5,284

6a_SF 02 116,667 71,029 41,765 - 83,543 9,991 764 75 3,563 11,147 784 29,719 5,166


6b_SF 01 - - - - 83,543 1,611 764 75 3,563 18,062 11,700 54,900 5,284

6b_SF 02 116,667 71,029 41,765 - 83,543 9,991 764 75 3,563 11,147 784 29,719 5,166

Composite Diagrid 6c_SF 01 56,925 - 31,050 37,261 83,543 7,911 764 75 3,563 18,062 - 8,550 4,702

6c_SF 02 55,306 24,724 17,281 32,799 83,543 5,620 764 75 3,563 10,952 648 21,138 4,702

Table 3.3: Inventory of Materials Calculated Through the Research ProjectSource: CTBUH


43

value. In other cases, the two variations will be presented as two different alternatives for the same basic design scheme. For example, Buro Happold decided that a concrete core was needed in all of the diagrid systems for scenarios 6a, 6b, and 6c, while SOM felt it necessary to add concrete shear walls only on scenario 6c to meet the design criteria. Clearly, these choices have an impact on the inventories of materials and, consequently, on the LCA of the buildings. In the real world, these possibilities (and many more different design alternatives) would have been assessed for the design of a building structure, taking a greater number of variables into account such as cost of labor and materials, project timeline, contractor’s expertise, local and time-sensitive variables, etc. The resulting inventories of materials are presented in Section 9.

Construction Process and Transportation Phase

The transportation phase was modeled on the basis of the real material transportation distances for the construction of a tall office building completed in 2009 in Downtown Chicago, for which the engineering firm responsible for the comparative real building was able to provide a comprehensive set of information.The foundation systems associated with each of the considered tall building structures are highly relevant, but they are also very site-specific. Given the geographic variability of tall building projects, analyzing foundation systems were found to disproportionately skew the data sets in this study. Full LCA’s should include such considerations, but they have intentionally been omitted from this study to allow for a better comparative understanding.

Data for the on-site operations was calculated by contacting the suppliers of the largest machines operating on the comparative building site during the erection of the structures (cranes and concrete pumps) to receive information on their energy consumption. This phase regards steps A4 and A5 as described by EN 15978.

End of Life

The end-of-life quantities were obtained by consulting with three large demolition contractors operating on an international scale. Only the 60-story scenario was used in this circumstance as the demolition of such a building would still significantly exceed any previously demolished tall building. The same documentation that was provided to the engineering firms for the creation of the “bills of materials” was provided to the demolition firms in order to gather information on how a demolition project on this scale would be handled, which kind of machinery would be involved, and how long the demolition job would take.

The responses of the consulted demolition contractors informed the creation of an end-of-life scenario for the various scenarios of the building structures. The demolition materials are considered to be hauled to the closest scrapyard and concrete recycling plant to the building site. This phase regards steps C1–C3 as described by EN 15978.


4.0 Steel: Cradle to Grave


Figure 4.1: Schematic of a Blast Oxygen Furnace Source: Yellishetti et al, 2011, redrawn by CTBUH

STOCKHOUSE

IRON ORECOKE

LIMESTONEDOLOMITE

PARTICULATE EMISSION

GASCLEANING

BOILERS

COMBUSTIONAIR 80%

EFFICIENCY

CENTRAL BOILER STATION

COLD STEAMELSEWHERE

STEAM 3100 kPa400°C COKE OVEN

CONDENSERS

BLOWINGENGINE

1035 kPaSTEAM

AIRTURBINE

AIRTURBINE AIR

TURBINE(C, Fe)

Cast HouseEmissions

Control

FLUEDUSTFe, C, S

COLDBLAST

Raw BFGN2

CO2

NO2

BFG (exported)

COLD BLAST AIRHEAT OF COMPRESSION 150°C

HOT BLASTWIND

O2

IRO

N(F

e,

C, S

)

SLA

G (C

a, S

, F)

PART

ICU

LATE

(NO

2)

CO2,

SO2,

NO

X

EMIS

SIO

NS

CO2,

H2O

, NO

X

EMIS

SIO

NS

FEED

WA

TER

FUEL

STOVES1/3 BURN150°C

TO SINTER PLANT

ELECTRICITY

46

4.0 Steel: Cradle to Grave

Steel is a highly demanded product used for many purposes, including buildings and automobiles. The use of steel as a structural element in buildings goes back to the mid-18th century, when the industrialized production of steel was made possible. It is a metal product with the unique ability to withstand both compression and tension forces, making it a great candidate for building structures.

As the construction of tall buildings became a trend in the 20th century, steel framed structures have become very popular. Their light weight in comparison to concrete or masonry structures, their capability of holding large forces (both horizontal and vertical) over wide

carbonated to make steel. The steel is then molded and rolled into the desired shape (Yellishetty, et al., 2011).

There are only a few integrated BOF mills in the United States that are able to produce large amounts of high-grade steel, a material mainly used in big steel profiles such as large structural steel sections and sophisticated steel products such as high-strength steel or alloy steel.

As steel is a highly recyclable material, a significant part of the new steel produced in the industry, especially in Europe and North America, is made out of recycled steel scrap. This production method utilizes Electric Arc Furnaces (EAF). Unlike

spans, and relatively small profile (which results in more space efficiency) are the qualities that gave rise to the popularity of structural steel products.

4.1 Steel Production

Steel is produced using a complicated and energy-intensive process: it is produced through the carbonation of iron (pig iron or cast iron made of iron ore). This initial production procedure is done in blast oxygen furnaces (Yellishetty, et al., 2011).

A Blast Oxygen Furnace (BOF) uses iron ore, oxygen blast, and coke, heating the compounds to make pig iron (see Figure 4.1). The produced iron pellets then get

| Steel: Cradle to Grave © Council on Tall Buildings and Urban Habitat

Figure 4.2: Schematic of an Electric Arc FurnaceSource: Yellishetti et al, 2011, redrawn by CTBUH

47

et al., 2010), although the impact of steel production in EAFs also vary based on the energy source used to generate the required electricity.

Although most new steel mills use electricity as their power source instead of burning coal or natural gas (ATHENA Sustainable Materials Institute, 2002), the average carbon footprint (1.77 kg CO

2/

kg average) and embodied energy (24.4 MJ/kg average) of steel products is on par with the average of the world’s combined production processes (Hammond & Jones, 2008).

There are two grades of steel used in the tall building structures considered in this research; normal-strength (50 Ksi/345 MPa) and high-strength (65 Ksi/450 MPa).

Although normal-strength and high-strength steel are not very different in terms of embodied energy and CO

2

emissions (Stroetmann, 2011), the use of high-strength steel in tall building structures helps reduce the environmental impacts of steel by using a smaller quantity of steel profiles.

Although the high-strength steel used in steel structures is mostly limited to

blast oxygen furnaces, EAFs use electrical energy to melt steel scrap and form the molten steel back into various shapes though molding and rolling (Yellishetty, et al., 2011) (see Figure 4.2). In 2014, 60% of steel in the EU was produced with the BOF method, while the remainder came from EAFs. In the US, the above mentioned percentages were inverted, with 40% coming from BOFs, and 60% from EAFs (WorldSteel, 2014).

Although the BOF method uses mostly virgin iron and the EAF method uses mostly scrap as the raw material, there is still scrap used in the BOF steelmaking process (about 25% scrap is used in BOF furnaces) and some virgin iron is needed in EAFs (5% virgin iron on average). The steel made in combination mills, which use a combination of EAFs and BOFs, thus contain an average amount of steel scrap based on the proportion of each production route in the overall number of steel products (Briggs, et al., 2010). Production data for steel typically utilizes an average of these routes, on both national and international levels.

The steel products from EAF mills are usually smaller in size and sometimes lower in grade compared to the steel from integrated BOF mills. Steel rebar and other reinforcement steel products are mostly produced using the EAF method and thus contain significant scrap content, while structural steel sections are produced using both EAF and BOF routes (Yellishetty, et al., 2011). The actual scrap ratio of various steel products may differ based on the location of their source and, consequently, the environmental impacts associated with steel production can vary by production process. The coke-making and iron-making processes in a BOF mill contribute much more to the environmental impacts of steel than the electricity used in EAF mills (Briggs,

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INFILTRATIONO2, N2

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Steel: Cradle to Grave | © Council on Tall Buildings and Urban Habitat

Figure 4.3: Example of steel profileSource: ArcelorMittal Group

48

vertical structural members (Stroetmann, 2011) due to the lack of stiffness in lighter, high-strength steel profiles (AISC, 2012), they can be widely used in composite structures, where concrete coverage provides the stiffness needed by the design criteria, especially for the vertical elements whose design is dominated by buckling forces (Trabucco, et al., 2014).

4.2 Structural Steel Profiles

Structural steel sections are the main components in a steel structure. Made out of hot rolled steel and usually shaped into a wide flange profile (I- or H-shaped), steel profiles are made in a way that directs the material mass to where the forces are applied on the structure (see Figure 4.3). The load-bearing capacity of steel components is related to their size (web height and flange width in case

of bending) and material thickness (for both web and flanges in case of shear or buckling). In other words, similar-sized steel profiles can have different thicknesses, and therefore different structural capabilities.

Structural steel sections are produced using both blast furnaces and electric-arc furnaces in medium- to large-scale steel mills. Using a higher grade of steel compared to steel rebar, structural steel can use either less or more recycled steel, depending on its source and production location. ATHENA (ATHENA Sustainable Materials Institute, 2002) assumes 76% scrap content for structural steel profiles, while EcoInvent uses a higher scrap content as the average European value (85%). As the EcoInvent values have been adopted by Worldsteel Association as examples for good steel production

practice, they were also used in this research study. The GWP value of 1.14 kg CO

2/kg and an EE of 14.8 MJ/kg are

therefore used for this research.

Structural steel sections represent high-value steel components with a very high recyclability of 95% (American Iron and Steel Institute, 2013). Easy to dismantle, easy to access steel sections are very easy to recycle, compared to the reinforcement steel, which is embedded in concrete. A description of the possible re-uses of large steel profiles is given in the section dedicated to the end-of-life for tall buildings, see Section 8.

Considering the fact that these buildings are constructed with very large steel elements, the research team, based on the results of the demolitions inquiry (see Section 8), decided to increase the recycling rate of structural steel components to 99% instead than the above mentioned 95%, which represents the average American recycling rate.

4.3 Steel Plates

Steel plates are thicker, stronger sheets of steel that are mainly used in stiffeners, connections, or as base plates in steel structures. The steel plate connections are cut into specific sizes/shapes and then welded to the corresponding steel sections in order to make structural members (mostly beams and trusses). This process is done in the fabrication workshop.

Unlike steel sections and rebar, steel plate consists of a high amount of virgin material (only 11% scrap content according to EcoInvent), as it is typically a product of a BOF steel-making route with high environmental impacts (with a GWP of 2.46 kg CO

2Eq. and an EE of 26.07

MJ/kg). ATHENA (ATHENA Sustainable Materials Institute, 2002) considers 36% of


CO2 [Kg] Energy [MJ]

Material Production 894,000 11,500,000

(% of Total) 59% 58%

Fabrication 277,000 3,640,000

(% of Total) 18% 18%

Erection 342,000 4,740,000

(% of Total) 23% 24%

Total 1,510,000 19,900,000

Table 4.1: Breakdown of the Various Stages of Steel ConstructionSource: (Guggemos, et al., 2010)

49

scrap content, resulting in lower GWP and EE figures (1.33 kg CO

2Eq. and 24.71 MJ/

kg) for steel plates, while Hammond and Jones (Hammond & Jones, 2011) consider no scrap content, resulting in much higher GWP (3.27 kg CO

2Eq.) and EE figures (45.4

MJ) for each kg of plates.

Due to its thickness, steel plates can’t be cold rolled, but need to be hot rolled like steel sections and larger steel products, making them even more energy intensive.

At the same time, the content of steel plates in a building structure is limited to connections and stiffeners, which are considered to be about 5% of the weight of steel beams and trusses.

4.4 Steel Fabrication

Steel sections, plates, and connections need to be fabricated to produce the correct steel components for a building structure. The fabrication process includes: cutting to size, welding, drilling, and coating – and has to be done according to each project’s drawings and specifications. The carbon emissions and embodied energies associated with steel fabrication is described in Section 4.8.

Usually, fabrication shops are located at a steel mill and perform welding, drilling, and machine-work as well as apply coatings and primers in controlled, factory conditions. Approximately 5% of new scrap is a result of this procedure, which returns to the melting furnaces right away (Davis, et al., 2007). Therefore, there is virtually no transportation involved in this procedure. Steel components are then shipped to the job site using high-capacity transportation means, like trains and trucks.

The GWP and EE of the fabrication process must be considered when calculating the total environmental impacts of steel elements after they have been delivered to the building site (see Table 4.1).

In this research, the various structural elements are considered with different levels of complexity: trusses are simple steel profiles; beams are fully fabricated products (through the addition of steel plates as described below); and columns are steel profiles fabricated without the addition of any plates.

Consequently, the total GWP and EE of columns and beams are calculated as follows:

Total GWP or EE of Steel Elements = GWP or EE of Steel Production + GWP or EE of Steel Fabrication

As the GWP and EE of all steel products are available through cradle-to-gate Life Cycle Inventories used by the LCA software, the GWP and EE associated with fabrication procedures were not immediately available and had to be found in literature.

A study conducted by the American Institute of Steel Construction (AISC) in 2010 shows that fabricating 1 kg of structural steel would have an average GWP of 0.215 kg CO

2Eq. (Ranging from 0.261 kg CO

2Eq./

kg to 0.193 kg CO2Eq./kg) and an average

primary EE of 2.82 MJ (ranging from 2.42 MJ/kg to 3.71 MJ/kg) (Weisenberger, 2010).

A different study (Guggemos, et al., 2010) shows that the electricity used to fabricate 1 kg of structural steel in the same project was 0.75 MJ/kg of the final product, which would correspond to 2.23 MJ of primary embodied energy (also accounting for energy waste during the production and distribution of electricity).

Among all fabrication procedures, shot-blasting (surface treatment with the use of metal shots to clean the surface and maximize attachment to the coating) and welding are the most energy intensive, together consuming 92% of the total energy used by the fabrication shop (Guggemos, et al., 2010).

ArcelorMittal, however, provided a report prepared by P. E. International, a third-party LCA firm, which indicated the electricity input per kg of steel produced equal to 0.15 MJ. This case-specific value has therefore been used for this research.

Electricity inputs of 0.15 MJ (corresponding to an EE of 0.44 MJ and a GWP of 0.03 kg of CO

2) are added to each kilogram of beams


Figure 4.4: Use of steel rebar for the construction of structural reinforced concrete elementsSource: Dario Trabucco

50

and columns; consequently, steel beams are considered as per the following:

1 kg Steel Beams = 0.95 kg of Steel Profiles + 0.05 kg of Steel Plates + 0.15 MJ of Electricity

Columns are considered as:

1 kg Steel Columns = 1 kg of Steel Profiles + 0.15 MJ of Electricity

4.5 Steel Rebar

Steel reinforcement bar (rebar) are the “ribbed” steel rods used to reinforce concrete elements where the concrete is weak, in the places that tension, bending, or shear forces are at work. The reinforced concrete can be used to build structural members such as beams, columns, and shear walls, replacing other structural

materials like wood or steel elements in building structures.

Steel rebar is the lowest grade of steel products, produced locally almost everywhere using small scale electric-arc mills (see Figure 4.4). It also has the highest content of recycled steel (containing 85% of recycled steel according to ATHENA and 69% according to Worldsteel) among all steel products used in the construction industry (ATHENA Sustainable Materials Institute, 2002) (WorldSteel Association, 2011).

Thanks to the high content of steel scrap, rebar have a GWP of 1.24 kg CO

2Eq./kg

and an EE of 16.42 MJ/kg according to WorldSteel. However better values can be found in the literature, such as the 0.45 kg CO

2Eq./kg on Inventory of Carbon and

Energy ( Hammond & Jones 2011).

Unlike structural steel, rebar and other reinforcement products are usually fabricated to the required form in a different location than the original steel mill. This adds a transportation factor to be considered when making comparisons in the LCA study (Guggemos, et al., 2010). The actual transportation means and distances, including those for the reinforcing steel, were calculated for this research based on what was used for the buildings that served as a reference.

On the other hand, studies done on the end-of-life procedures at a leading concrete recycling facility near Chicago for reinforced concrete reveals that the reinforcements removed from crushed concrete members have concrete remainders attached to them (between 10% to 25% of weight), which makes them a lower grade of scrap and less


Figure 4.5: Welded wire fabricSource: (cc-by-sa) Frank Vincentz (Ies)

51

desirable materials for recycling and re-melting in steel mills (Guggemos, et al., 2010). This would decrease the recyclability of steel rebar to only 70% compared to structural steel, of which 99% can be easily used as scrap (American Iron and Steel Institute, 2013).

This is mainly because of concrete particles that remain attached to the rebar even after crushing the reinforced concrete pieces and separating the rebar from the concrete. The concrete particles need to be taken off by hand, which makes the rebar more expensive to recover, and therefore, less desirable for scrap dealers. At the same time, concrete recyclers confirm that around 5% of the total reinforcements used in the reinforced concrete remains in the crushed concrete pieces.

In the present study, however, a much-higher recycling rate is considered. In fact, rebar used in tall buildings is thicker than those used in smaller buildings, thus making them easier and more profitable to be recovered. Consequently a recycling rate of 95% was used in this research.

4.6 Welded Wire Fabric

Welded wire fabric (WWF), also called welded wire mesh (WWM), is a reinforcing steel mesh used in steel-concrete composite floors (see Figure 4.5). This material is commonly used in steel structures at large scales, including tall buildings. Although WWF works as the main tension resistance element in the floor construction, additional layers of rebar mesh can be added on top of it, based on the design criteria for lateral loads, or to improve the fire resistance of the assembly.

Welded wire fabric is made of steel wire rod that contains almost 28% scrap according to Worldsteel Association (Worldsteel Association, 2011) and 42%

according to Hammond and Jones (Hammond & Jones, 2008). However in most countries WWF is made from steel rebar, thus sharing the same environmental property of this highly-recycled material.

Considering that there is no cradle-to-gate process for WWF as a standard product in the current LCA databases, an alternative gate-to-gate procedure for WWF was created for this research to be used in the LCA procedure plans. The necessary information for creating the gate-to-gate LCA procedures were acquired by Schnell, a manufacturer of the machines used to produce WWF that shared with the research team the average inputs for a certain production of WWF.

The energy, materials, and parts used for producing WWF were calculated based on the specifications of the machine used for its manufacturing, while transportation factors were calculated based on the figures used from the manufacturer’s locations and transportation distances for the building that served as the reference for this research.

The results show that the production process for 1 kg of WWF would have a global warming potential (GWP) of 1.25 kg CO

2Eq. and an embodied energy (EE)

of 16.57 MJ. Looking at the GWP and EE results for production of 1 kg of WWF, one can clearly see that the production of the steel wire rods keeps the highest share in both categories (99.3% of GWP and 98.3%


52

of EE). Table 4.3 shows the GWP and EE for the production of 1 kg of WWF.

In order to verify the gate-to-gate process created for WWF, the results from the study were then compared with the results from similar studies in the literature.

In the LCA of North American steel products conducted by ATHENA (ATHENA Sustainable Materials Institute, 2002), the total Embodied Energy for 1 kg of WWF is 15.24 MJ and the GWP is equal to 1.06 kg CO

2Eq.

In the Inventory of Carbon and Energy, Hammond and Jones (Hammond & Jones, 2008) consider 1.71 kg CO

2Eq. as the GWP

of the 1 kg of WWF, while the EE of its production would consume 24.6 MJ in their database.

When the GWP and EE from the gate-to-gate model developed for this study are compared to the above mentioned studies, the results show similarity to the LCA of North American steel products (ATHENA Sustainable Materials Institute, 2002), and remains in scale with the Inventory of Carbon and Energy results.

Being a reinforcing steel element embedded deep into concrete floors and other components, WWF does not have a great recyclability potential. As with rebar, there is still 10% to 20% of concrete remainders on the element as well as a 5% steel remainder in the crushed concrete aggregates (as mentioned in Section 4.5).

4.7 Metal Decking

In steel structures, steel decking is an important component of a composite steel-concrete floor. The steel decking

(made of corrugated steel sheets) holds all other components of the floor system together (steel reinforcements, WWF, and concrete slab), while also working to resist bending (see Figure 4.6).

The advantage of the metal deck slab system is the elimination of formwork and shoring, and the consequent increase in construction speed. The metal deck can be used as a working and erection platform. Also, it acts as a diaphragm to help stabilize the steel skeleton by integrating all members into a system (Vinnakota, et al., 2003).

Metal decking sheets are made from hot-dip galvanized cold rolled metal sheets (with only 10% scrap content) (Worldsteel Association, 2011). The galvanized sheets are then bent and corrugated using electric powered hydraulic press machines and rollers, and finally cut into standard sheets.

The scrap content, total GWP, and EE for producing the metal decking were also verified against the data from related studies. ATHENA considers 13% of scrap in the decking, resulting in the GWP of 1.76 kg CO

2Eq. and EE of 27.66 MJ per 1 kg

of decking sheets. Hammond and Jones, however, consider the decking made all out of virgin materials (no scrap content), yielding a GWP of 2.82 kg CO

2Eq. and EE

of 39 MJ for 1 kg of the final product. The Worldsteel data used in this research holds an average figure between ATHENA and Hammond’s results equal to a GWP of 2.56 kg CO

2Eq. and an EE of 28.22 MJ per 1 kg.

Like every other steel element, most of the energy consumption and carbon emissions for producing metal decks arises from the production of steel sheets

in the mill (ATHENA Sustainable Materials Institute, 2002). Although cold rolled steel is not considered a large steel product, the high content of virgin iron makes it an energy- and carbon-intensive product typically made in BOF steel mills.

The thickness, span, and depth of the ribs in decking may vary based on the loading criteria of the project as well as the span of beams and above slabs (Vinnakota, et al., 2003). The steel deck alone has to withstand the weight of the wet concrete, plus any construction loads for the placement of concrete to achieve the desired non-shored condition, while the composite steel deck (steel deck + concrete) has to withstand the factored superimposed dead and live loads (Vinnakota, et al., 2003).

As for commercial high-rise structures, the need for more net rentable office area and better daylight and view conditions in the space usually leads to longer spans, which need a deeper, thicker decking sheet (Vinnakota, et al., 2003).

The metal deck, like other steel floor elements such as beams and joists, is connected to other floor elements via steel shear studs made from steel wire rods (28% from scrap according to Worldsteel). The size, number, and location of the studs depend on the design loads of the floor system as well as the criteria from structural design drawings and specifications.

As an exposed steel element covering all floor slabs, metal decks are recycled fairly easily by detaching them from the slab during the structure’s demolition process. They are therefore considered with the same recycling rate of 99% which is used

Process Global Warming Potential [Kg CO2 Eq.] Embodied Energy [MJ]

Total 1.25 100.0% 16.57 100.0%

Raw Material (steel rebar) 1.24 99.3% 16.42 98.3%

Electricity Grid Mix 0.013 0.6% 0.20 0.8%

Diesel Mix at Refinery 0.002 0.1% 0.20 0.9%

Table 4.3: GWP and EE for the Production of 1 Kg of Welded Wire FabricSource: CTBUH


Figure 4.6: Example of metal deckingSource: (cc-by-sa) Kim Traynor

53

for structural steel scrap, shipped directly from the demolition site to the scrap yard together with structural steel sections. The steel shear studs, however, are to remain in the concrete slab and to be recovered later in the concrete recycling plant.

4.8 Steel Production Inventory Data

As the credibility of a LCA analysis depends on the depth, accuracy, and comprehensiveness of the Life Cycle Inventory (LCI) it is based upon, the choice for the correct LCI that represents the most accurate datasets is a critical part of every LCA study.

The cradle-to-gate LCI of each steel product needs to be assessed carefully from an ISO-complying, reliable database which is internationally recognized. The used “datasets” (LCI Processes) also need to best represent the region in which the study is done, following the most realistic routes for all components as well as the final product (Zygomalas & Baniotopoulos, 2013).

Two of the main LCI databases used widely in LCAs on structural steel construction are the EcoInvent and Worldsteel databases, both of which are available (as complete cradle-to-gate datasets) for the software used in the research (GaBi V.6.0). These datasets are also available as pre-defined, detailed cradle-to-gate processes in the software library of materials. The characteristics of both mentioned data are described as follows:

• EcoInvent datasets: The EcoInvent LCI database was initially developed in the late 1990s and contains more than 4,000 datasets referring to products, services, and processes. It was developed in Switzerland by the Swiss Centre for Life Cycle Inventories, which is also responsible for data updates. It refers to a mix of European technology, and the collection method used was a sampling procedure based on literature. A number of research centers in Switzerland and Germany

were involved with the development and constant update of the database, and the data are intended for use mainly within the European region (Zygomalas & Baniotopoulos, 2013). The EcoInvent database includes the dataset for steel manufacturing in an EAF route based on data from the year 2000, and also accounts for the transportation of scrap metal and other input materials to the EAF and casting. However, because this dataset refers to the manufacturing of steel up to the casting stage, it does not include the processes required for the production of hot-rolled structural steel members such as the reheat furnace operation, the hot rolling process, and the transportation of the finished products to final storage locations before being sent out for use (Zygomalas & Baniotopoulos, 2013). The EcoInvent processes are marked with RER in the LCI databases.


54

• Worldsteel datasets: The Worldsteel Association conducted an LCI study at a global scale in order to quantify all raw material, energy, and environmental emissions associated with producing steel products, including structural steel sections. The database was established in 1994–95, and was updated in 1999–2000 and 2010. The Worldsteel datasets provide cradle-to-gate (from raw material extraction to the steel factory gate) data on all the major raw materials. The study includes data on the energy usage, energy waste, air emissions, and water emissions of steel products. All environmental inputs and outputs are calculated for the production of 1 kg of steel products at the factory gate according to the ISO 14040 standard (Worldsteel Association, 2011). For structural steel, as an example, the data were collected from all over the world (but with very limited coverage of US mills). The mills from which the Worldsteel data were collected use some EAF steel-making routes and some blast furnace routes. Therefore, the datasets use an average of both routes (Zygomalas & Baniotopoulos, 2013).

Another notable fact about the Worldsteel data is the credit for recycling. The scrap ratios and therefore the scrap credits are based on the global average ratio (80% for steel sections, for example), while the corresponding recycled content for steel in Europe and the US are much higher (the current US corresponding rate for structural steel is about 98% according to ATHENA) (ATHENA Sustainable Materials Institute, 2002).

Looking at the two mentioned databases, the EcoInvent steel datasets miss some significant production processes (mainly reheating and the hot-rolling

process of steel), while data presented as Worldsteel “Global” datasets do not reflect commonly practiced steel production methods in the US market.

This fact makes it difficult to use any of the predefined cradle-to-gate datasets that would best represent American produced steel, which is used in the studied scenarios for this research. The steel products included in the GaBi database (used in this research) do not include comprehensive cradle-to-gate data on American steel products yet. At the same time, creating replacement gate-to-gate processes for them can affect the consistency and accuracy of the whole LCA.

Despite the fact that most of the structural and reinforcement steel products in the US are produced through an EAF route, while in their equivalent European products there is a higher share for BOF steel, the scrap content for European and American Steel is fairly similar. Additionally, the environmental regulations considered in American steel production is also more similar to European regulations than other parts of the world. This makes the European data a better replacement to the American cradle-to-gate datasets missing from the LCA software.

At the same time, because the Worldsteel datasets are the most inclusive cradle-to-gate data on steel production – including almost all inputs, outputs, energies, and emissions – the best data for steel products used in the LCI come from Worldsteel.

However, in recent versions of the software used in this research (GaBi V.60), the European average data presented in Ecoinvent datasets, is now adopted and completed by Worldsteel databases (Pe International, Inc., 2012). This new generation of processes can be used

as a replacement for US steel processes missing from the databases.

Given these considerations, the cradle-to-gate datasets for all steel products used in this research are taken from the average European data (EcoInvent data adopted by Worldsteel) whenever available. Having a generally higher content of steel scrap (compared to the global average) in addition to generally lower environmental impacts, are the main reasons they are used in the research.

4.9 Life Phase

Structural elements are considered permanent parts of a building through its life span, so there usually aren’t many changes, repairs, or replacements for steel structures, even if a building goes through a major retrofit or even a change of function.On the other hand, steel elements are subject to corrosion when exposed to the outside environment, yet most steel structure components are covered by a thick layer of fireproofing, coatings, and paint layers. This reduces the chance of corrosion and the need for replacement to a negligible level (Doering, et al., 2013).

At the same time, the concept of “durability” in building structures has become broader than just the degradation of structural materials when sustainability aspects are taken into account. Canadian Architect (Canadian Architect, n.d.) proposes a new definition for durability that helps measure sustainability as the consideration of the durability like the equivalence between the useful service of a material (or component or system) and its time required for the absorption of its impact by the ecosystem. In other words, energy and resource-intensive structural materials need to have a very long service life to be considered durable, while structural materials mostly made


Figure 4.7: Steel scrap yardSource: Dario Trabucco

55

of natural materials do not need to live as long to be considered durable/sustainable (Buonopane, 2010).

Structural steel, together with its alternative, is predicted to last throughout a building’s entire service life, which lasts between 75 and 100 years for tall buildings and is almost unlimited for supertall buildings (Buonopane, 2010). Therefore, structural steel is considered permanent and its environmental impacts minimal during the lifetime of a building.

4.10 Recycling

As much as the concept of recycling steel members, such as beams and columns, sounds attractive from an environmental standpoint, liability issues, together with the need for thorough inspections and longer, more expensive dismantling procedures, keep the structural re-use of steel from finding a real market, especially when it comes to skyscrapers with large-scales and highly optimized designs.

Steel, in general, is a highly recyclable material (95% according to American Iron and Steel Institute) (American Iron and Steel Institute, 2013) with a very high residual value ($385/T according to American Metal Market and Scrap Price Bulletin). Most of the revenue for both demolition contractors and recycling plants come from steel and other metal components that were once used in a building.

The high value and large market for recycled steel or scrap (Worldsteel Association, 2011), (Yellishetty, et al., 2011) in addition to the fact that steel keeps its characteristics after recycling, provide a great advantage to steel structures versus concrete structures, which are heavier, more difficult to demolish, and can be recycled only to gravel for road construction. Even the steel reinforcements used in concrete

structures have lower residual values because of the large amount of concrete still attached to them after demolition (Guggemos, et al., 2010). According to the Worldsteel association, there are two different methods for assessing the life cycle of steel products: “closed loop” LCA and the “Credit/Burden methodology” (Worldsteel Association, 2011).

In the “closed loop” method, scrap materials from the demolition/recycling process return to the beginning of the steel production process, while the open credit/burden methodology focuses on the credit (negative figure in the final LCA results) that can be received from the scrap obtained from the demolition of the building structure.

In this case, since the steel products used in the software datasets already use a high

quantity of scrap as raw materials through the EAF production route (or combination routes including both BOFs and EAFs), the credit for scrap can only be awarded to the “net value of scrap” produced in the demolition process (Worldsteel Association, 2011). The net value of scrap is calculated by subtracting the steel scrap obtained from demolishing a certain steel product from the original quantity of scrap used to produce that product. Structural steel sections have higher EE and GWP than steel rebar, as they contain a higher grade of steel with higher level of virgin materials like iron ore (Worldsteel Association, 2011). As an example, to produce 1 kg of European steel sections, there is a need for 0.85 kg of steel scrap. The net scrap value for the average European data steel sections is calculated as follows:


Figure 4.8: Steel scrap yard Source: Dario Trabucco

56

Net value of scrap for steel sections = 1 kg – 0.85 kg = 0.15 kg

Out of the 1 kg of steel scrap created by the demolition of sections, 0.15 kg is the amount which can be used to “obtain” the credit, as the remaining fraction was already produced using steel scrap.

The global warming potential and embodied energy for the production of different steel elements differ based on their manufacturing process and source. At the same time, the steel scrap coming from a demolition project is a mixture of all the different steel products used in the building. Therefore, an average net value for scrap has to be

calculated in order to assess the credit for scrap correctly.

This average value will depend on the net scrap ratio for each steel product as well as the share of each product in the final scrap mix. This ratio also differs from building to building, depending on the types of steel products used in them. For instance, the scrap from a concrete structure is mainly made of steel rebar, while a steel building with a concrete core or an all-steel building can contain different amounts of steel sections, plates or decking which are more easily recycled.

In order to obtain an average net scrap value for each design scenario, quantities of the different steel products in that scenario are calculated, while the scrap inputs for each steel product are taken from the LCI of each structural material. The net value of scrap for each steel product in the scenario are then calculated by subtracting the total scrap input for each product from the total quantity of that product in the building. The result from this equation is the total net scrap from that product.

As structural and reinforcement steel scraps have different recycling routes and different recycling factors, the total net scrap quantities for structural and reinforcement steels are calculated separately for each design alternative. These two numbers are then added to calculate the total net scrap quantity for that design. The net scrap ratio, for which the scrap credit is awarded, is then calculated by dividing the total net scrap quantity by the total steel used in the building. (Worldsteel Association, 2011).

However, it is important to note that the scientific community of LCA practitioners does not unanimously accept the procedure suggested by Worldsteel. In

“...The research results are presented under

two different scenarios to denote end-of-life

of the building...”


Figure 4.9: Separation of the different material wasteSource: Dario Trabucco

57

particular, the fact that a benefit (i.e., the credit for scrap) is awarded now for something (i.e., the recycling of the material) that may or may not happen in the future is criticized. The “credit for scrap” principle is based on the assumption that the use of steel will grow indefinitely worldwide and, consequently, that the need for steel scrap will always exceed its availability. As a result, one can assume that the steel produced today will be recycled and, therefore will save both the raw materials and energy associated with the extraction, transportation, and production of steel from virgin iron. Despite this assumption – which is based on the current conditions of the steel market – if steel use should decrease in

the future, some of the steel used today will not be recycled as scrap and the environmental benefits accounted for by the credit would not be realized.

For this reason, the research results are presented under two different scenarios to denote the end-of-life of the building: one where the energy for demolishing the building is considered, but no credit is awarded for the recycling of its materials, and another that includes “Module D” as described by EN 15978.


5.0 Concrete: Cradle to Grave


Figure 5.1: Cement clinkerSource: (cc-by-sa) Amit Kenny

60

Various types of concrete are used in high-rises: normal and lightweight (especially for floor systems); and conventional and high performance (with higher strength, durability, and workability). These are often integrated in the technologies adopted in tall buildings, which can vary from traditional Reinforced Concrete (RC) to post-tensioned systems that use high-performance concrete.

Although in some recent studies (Weisenberger, 2010), where the benefits of structural steel frames have been demonstrated (reduced column sizes, high strength-to-member-size benefits), concrete systems have gained great acceptance and the material has been widely used by designers, especially since the 1970s. This is partially related to the fact that the concrete wall is the stiffest element currently in the structural engineer’s tool kit when conceiving tower framing systems. Tall building design is often controlled by stiffness more that strength. Also, concrete can be poured into different shapes, even under extreme weather conditions and temperatures, and is easily delivered to job sites (concrete plants tend to be conveniently located, even to city centers and busy metropolitan areas). Aggressive environmental conditions are countered with additives that are able to significantly enhance the durability of the material.

As a consequence of the increase of concrete use, the environmental impact of concrete production is growing. Concrete production is considered to be responsible for up to 10% of global CO

2

emissions (Ochsendorf, 2005), including infrastructure construction.

5.1 Cement Production and Transportation

Cement consists of a controlled chemical combination of calcium oxides, silicon, aluminum, iron, and other ingredients.

The most common manufacturing process for cement is a dry method. After quarrying raw materials including limestone, shells, and chalk (or marl), they are crushed in several stages using crushers and hammer mills. Crushed rock is then combined with other components such as shale, clay, slate, blast furnace slag, silica sand, and iron ore. The mixture is fed into a cylindrical steel rotary kiln that heats the ingredients to about 1480°C, powered by burning powdered coal, oil, alternative fuels, or gas under a forced draft. This heating and mixing process releases both clinker and gasses. Clinker (see Figure 5.1) is brought down to handling temperature in coolers. In order to increase burning efficiency and save fuel, heated air is returned to the kilns. The cooled clinker is

then mixed with small amounts of gypsum and limestone, then ground to a fine powder commonly known as cement.

Among all concrete production procedures, cement production is responsible for the greatest amount of CO

2 emissions: on average, every ton

of cement produces 0.9 tons of CO2.

Although cement industries have focused their efforts on reducing CO

2 emissions

related to the thermal energy of clinker production, little can be done to reduce the carbon released from limestone decomposition, unless the amount of Portland cement is minimized in the design mix.

In fact, it is important to note in the equation below, CO

2 is not released just as

a consequence of the fossil fuels burnt to heat the mixture in the kiln, but also as a by-product of the chemical reaction that transforms the limestone in clinker, with the following percentages (Kestner, et al., 2010): 40% from the production of clinker;

5.0 Concrete: Cradle to Grave

| Concrete: Cradle to Grave © Council on Tall Buildings and Urban Habitat

61

60% from the decomposition of limestone under high temperatures (above 1370°C).

Simplified chemical reaction of cement production:

CaCO3 + Heat → CaO + CO

2 ↑

Considering that 15% to 20% of cement is used in conventional concrete mixes, replacing 50% of cement with fly ash or other substitutes can lead to a significant reduction in CO

2 related to

the “carbonation” of cement. A good concrete mix design is one that meets the required levels of workability, strength, and durability for every building. However, in order to meet more stringent sustainability requirements, the designer may consider using non-cement binders and recycled aggregates.

The cement industry produces about 7% of global manmade CO

2 emissions

(Ochsendorf, 2005), of which 60% arises from the chemical process, and 40% from burning fuel. Emissions from cement production plants, apart from CO

2, include

dust, nitrogen oxide (NOx), sulphur oxide

(SOx), as well as some micro-pollutants

(World Business Council for Sustainable Development, 2002). Heavy metals (Tl, Cd, Hg, etc.) are often found as trace elements in common metal sulfides. Pyrite (FeS

2),

zinc blende (ZnS), and galena (PbS) are present as secondary minerals in most of the raw materials.

In terms of energy consumption, cement production requires 4 GJ of energy per ton of clinker produced (Kestner, et al., 2010). Typical primary fuels used in clinker production are fossil fuels such as coal and petroleum cokes, as well as natural gas and oil. It is possible to use selected waste that meets strict specifications for combustion in a kiln, partially replacing fossil fuels. This waste often contains not

only recoverable calorific value, but also useful minerals such as calcium silica, alumina, and iron; therefore, it can be used as raw material in the kiln. However, the distinction between alternative fuels and alternative raw materials is not always clear, since some of them are characterized by both recoverable calorific value and useful minerals. Organic substances as well as alternative fuels can be used for this purpose, since the high temperatures of the kiln gasses destroy the toughest organic substances.

Sustainability is not an empirical property of materials, since the choice of suitable materials cannot be based on numerical parameters, as is done in the process of selecting materials for their strength and elasticity characteristics. Therefore, in assessing the sustainability of building materials it is necessary to compare and quantify the environmental impacts as well as identify the context in which the material will be applied.

Cement leaves the cement plant and is transported to either a distribution terminal or a final customer, such as a concrete production plant or a ready mix plant. Transportation and distribution occurs via boat, train, or truck. Cement transportation requires special care in order to avoid: contamination by residues or previous cargoes; solidification, if cement is exposed to humidity and wet conditions; and dust released during loading (dust can react with water and harden, damaging the transportation tools). Transportation by ship is particularly difficult: specialized ships called cement carriers are available with different capacities. More advanced technologies include cement carriers equipped with self discharging systems.

As the commodity cost is quite low, transportation cost is a key factor in

competitively supplying customers with cement.

5.2 Cement Substitutes

The American Concrete Institute’s Building Code Requirements for Structural Concrete (ACI318-11) defines a High Performance Concrete (HPC) as a special engineered concrete in which one or more specific characteristics have been enhanced through the selection of components. Thus, the concept of HPC has been evolving since the 1970s. For this reason Mehta (Mehta, 2004) suggests that the term “high performance” should be applied to the entire family of concrete mixtures that offer higher strength, higher durability, and higher workability. One of the engineered processes of HPC production is the partial substitution of Portland cements in mix

“...Cement substitutes...reduce the carbon footprint, embodied

energy, material waste in landfills, extraction

of virgin materials and the environmental

impacts related to manufacturing Portland cement

clinker...”

Concrete: Cradle to Grave | © Council on Tall Buildings and Urban Habitat

Figure 5.2: Reinforced concrete core under constructionSource: Dario Trabucco

62

design. Complementary Cement Materials (CCM) can partially replace cement and complement the hydration of cement products with a secondary reaction, forming a calcium silicate hydrate component. Fly ash (up to a 25% replacement in mass), slag (up to a 60% replacement in mass), and silica fumes (up to a 70% replacement in mass) are the most commonly used cement substitutes in concrete mixes. From an environmental standpoint, they reduce the carbon footprint, embodied energy, material waste in landfills, extraction of virgin materials, and the environmental impacts related to manufacturing Portland cement clinker, as they modify the chemical reaction happening in the kiln or during the hydration process. From a performance standpoint, they generally enhance workability, facilitate pumping, reduce bleed water, offer better resistance to segregation, and increase the durability of the final product. On the other hand, as these substitutes develop a lower hydration heat, they are characterized by a slower rate of strength gain. For this reason, they may

be more suitable for use in the foundation and shear walls of high-rise structures, as these elements are not subject to high loads in the first few months of the project. Concrete mixes with cement substitutes may be not suitable for post tensioned slabs, where high strength is necessary in early stages. In order to achieve more sustainable results, Mehta (Metha, 2005) suggests the use of high-volume fly ash (HVFA), in which the replacement of cementitious material is greater than 50% in mass.

Fly ash is a pozzolanic product of coal-fired power plants, defined in Cement and Concrete Terminology (ACI Committee 116) as “the finely divided residue resulting from the combustion of ground or powdered coal, which is transported from the firebox through the boiler by flue gases.” Class C fly ash – obtained by burning lignite or sub-bituminous coal - is the main type offered by ready mix suppliers for residential applications. High performance concrete (high strength, workability, and durability)

mix is considered as high-volume fly ash (HVFA) when fly ash comprises more than 50% of the mixture’s cementitious material by mass. Mehta (Metha, 2004) also suggests mixtures with low water (< 130 kg/m3) and cement content (< 200 kg/m3). Detailed requirements for superplasticizer use and slump tests are based on strength requirements.

As the American Concrete Institute “Proportioning Concrete Mixtures Commission” (ACI 211) only provides specifications for concrete mixes with regular values of fly ash (up to 35%), but not the values found in HVFA, concrete producers only supply ready mixed designs for those mixtures. However, the procedure provided by ACI 211 offers solutions to design trivial batches of HVFA and also provides information on the adjustments needed in partially-cement-replaced concretes. The Committee is currently working on a report specifically on HVFA concrete (Bentz, et al., 2013).Some of the advantages of using HVFA concrete (Bentz, et al., 2013) are as follows:

• Reduced demand for water in the design mix (up to 20%): Using HVFA helps prevent cement flocculation by providing a desirable dispersion that reduces the amount of water required to achieve a given consistency. It also reduces friction and facilitates mobility, allowing it to act as a low-density void filler.

• Improved workability: The mixtures using HVFA seem cohesive, easy to pump, and are less likely to segregate. A superplasticizer may be required for heavily reinforced applications.

• Minimized cracks from drying shrinkage: Drying shrinkage is influenced by the amount of water in the mix, so reducing water


Figure 5.3: Concrete floor slabs under constructionSource: Dario Trabucco

63

demand also helps reduce drying shrinkage cracking.

• Minimized thermal cracking: It has been proven that a 40 MPa concrete containing 350 kg/m3 of cement can raise curing temperatures by 55-60°C, resulting in a high cooling rate that can cause cracking. The same mixture with a 50% replacement of fly ash will only raise temperatures by 30-35°C, therefore reducing the possibility for thermal cracks.

• Enhanced resistance to reinforcement corrosion, sulfate attack, and alkali-silica expansion: The durability of reinforced concrete components is affected by the permeability (especially by percolation) of the concrete through the interfacial micro-cracks close to aggregate surface. Fine particles of fly ash help to fill pores and reduce weaknesses in the concrete microstructure.

The process also consumes a large amount of fly ash, thus diverting it from landfill and reduces overall concrete quantities from achieving a higher-strength mix. Some of the disadvantages of using HVFA concrete are as follows:

• Longer setting time: The lower hydration rate of the fly ash creates a longer setting period. As chemical accelerators may be useful to improve the delays, the cost increase for using these substances can become prohibitive.

• Longer curing (moistening) time (longer than seven days): As fly ash hydrates slower than Portland cement, the water not consumed in the early-stage chemical reaction or absorbed by hydration may evaporate. Therefore, it is

fundamental to cure (moisten) the HVFA concrete for longer than the typical seven-day period.

• Higher tendency for plastic shrinkage cracking: HVFA concrete is harder than normal concrete and its mechanical behavior is similar to glass, with a higher fragility than normal concrete.

• Slower strength development at early ages: In this case, in order to achieve acceptable early-age strength, it is possible to either reduce the water/cement ratio, replace Type I with Type III cement (for a 10% cost increase), or add fine limestone.

There are examples where HVFA has been used instead of cement in concrete mixes for various projects in the US, most of which achieved positive results in terms of carbon emission reductions. HVFA with 50% cement replacement has been used in the US and Canada since 1987 for different applications such as slabs, beams, columns,

foundations, and finishing. Some examples of this, according to Mehta (2004), are the Hindu temple (2003) in Chicago (800 tons of CO

2 saved), the Utah Capitol State Building

seismic renovation (2006) in Salt Lake City (900 tons of CO

2 saved), and the CITRIS

Building (2007) at the University of California at Berkeley (1,950 tons of CO

2 saved).

From a life cycle perspective, the use of waste materials such as fly ash or silica fumes to replace cement in a concrete mix design allows for a significant reduction in the embodied carbon of concrete used in various buildings. According to the US Environmental Protection Agency (EPA), fly ash carbon emission is significantly low (0.011 kg of CO

2 per kg of fly ash)

compared to cement (0.95 kg of CO2

per kg of cement, data provided by ICE 2011) since fly ash is the byproduct of coal combusted for electricity generation. Also, no emissions are attributed to fly ash except those caused by its transportation.As far as durability is concerned, concrete is “durable” if it has achieved the desired


Figure 5.4: Steel reinforcement after the separation from concrete elements Source: Dario Trabucco

64

service life without excessive maintenance costs due to degradation or deterioration. ACI 201 “Guide to Durable Concrete” defines durability indicators as the behavior of the concrete with respect to:

• Freezing and thawing (including the effects of de-icing chemicals);

• Aggressive chemical exposure (sulfate, seawater, acid, and carbonation);

• Abrasion (floors, pavements, studded tires, and tire chains);

• Corrosion of metals and other materials embedded in concrete;

• Chemical reaction of aggregates (alkali-silica reaction and alkali-carbonate rock reaction).

Research and tests on concrete made with cement replacements (Chan & Wu, 2000) demonstrate enhanced durability compared to concrete mixtures that use Ordinary Portland Cement (OPC). In concrete with cement substitutes, the porosity index is reduced, specimens have a good response to water permeability (if the cement replacements are accurately selected), composition appears to be

more homogeneous, and the number of micro-cracks is reduced. More specifically, according to Bentz et al. (Bentz, et al., 2013), HVFA concrete provides significant reductions in Rapid Chloride Permeability Test (RCPT) values and corresponding increases in measured surface resistivity. It also shows increased resistance to deleterious expansion caused by Alkali-Silica Reactions (ASR) and a reduction in electrical conductivity (diffusivity).

Despite the fact that cement substitutes are now becoming more popular, even in high-end applications such as tall buildings, the present research considers normal, commercially available concrete, as it still represents the most common choice in building sites around the world.

5.3 Gravel, Sand, and Aggregates

Aggregates are inert granular materials (such as sand, gravel, or crushed stone) that constitute the bulk of a concrete mixture and account for 60% to 75% of its total volume.

There are two types of aggregates used in concrete: fine and coarse. Fine aggregates consist of natural sand or crushed stone,

most of which pass through a 1 cm sieve. Coarse aggregates generally fall between 1 cm and 3.8 cm in diameter and are used in concrete in the form of gravels or crushed stones.

The total cost of surface mining dictates the technology used to extract aggregates (Smith, et al., 2001). The most commonly used procedure is simply called “quarrying” and the excavation methods depend on the type of deposit and its degree of consolidation. Highly consolidated rocks (or simply “hard rocks”) require drilling and blasting to reduce the mass to particle size (which can be dug from a loose pile). Primary fragmentation may be realized through explosions (using high explosives such as TNT-based dynamites or blasting agents such as ammonium nitrate solutions in a mixture of oil and wax) or ripping (mechanical breaking with a single tooth mounted at the rear of a powerful crawler tractor). If secondary fragmentation is required, it usually consists of secondary blasting, drop balling, or the use of hydraulic impact breakers. Under-consolidated or weakly-consolidated rocks can be directly extracted from the ground without these disaggregation procedures. There are various types of earth moving machines used for this purpose, among which the most common are hydraulic shovels and hydraulic backhoes.

Particle sizes and shapes are obtained by crushing the extracted raw materials. Typical machines used for this purpose are the jaw, gyratory, and fixed blow-bar impactors powered by diesel engines. The jaw crusher compresses rock between a fixed jaw and a moving jaw to create breakage. The particle size is determined by the width of the aperture when the moving jar has fully retreated. Impactors are characterized by a chamber with a horizontal rotor revolving inside. The


Figure 5.5: Concrete recycling Source: Dario Trabucco

65

rotor is fitted with either swing hammers or blow-bars. Comminution is achieved through the combined effects of the rock impacting against hammers or blow bars, inter-particulate collisions, and impact against the chamber lines (breaker plates).

Typically, these systems are directly fed by quarried rock carried by dump trucks. More recently, the high cost of dump truck hauling has been an incentive to develop in-pit crushing systems mounted on fully mobile or semi-fixed frames. Hauling is a major cost factor in the production of construction aggregates, with considerable expenditures incurred in fuels, tires, and engine wear. Nowadays, most aggregates are moved by Heavy Goods Vehicles (HGVs), although air pollution and road traffic congestion may be reduced via freighting quarry products on rail or on inland waterways.

Recycled aggregates coming from Construction and Demolition Waste (CDW) have a high potential to be used in concrete mixes (Silva, et al., 2014). The three main types of materials derived from CDW are crushed concrete, crushed masonry, and mixed demolition debris. If these materials are not reused, CDWs have to be placed in landfills or downcycled as ballasts for road and rail construction. Thormark (Thormark, 2001) suggests that the need for energy and natural resources can be reduced by recycling building waste, thus limiting the land area needed for landfill.

5.4 Concrete Production and Transportation

Concrete production is a time-sensitive process consisting of mixing cement, water, and aggregates, sometimes adding chemical components called additives, to create a semi-fluid admixture which is poured into formworks to harden,

developing compressive strength and much lower tensile strength.

In general, concrete is a composite material and its performance depends on the amount and ratio of mixed components. During the concrete curing/hydration process, the cementitious material reacts with water to create a cement paste that bonds the aggregates together until it hardens, obtaining a solid mass. The chemical reaction of hydration is presented below in standard notation:

Ca3SiO

5 + H

2O →(CaO)•(SiO

2)•(H

2O)•(gel)+

Ca(OH)2

Sand, natural gravels, and crushed stones are usually indicated as aggregates. A good design and redistribution of the aggregates in a concrete mix is achieved through vibration in order to avoid segregation, obtain a homogeneous mixture, and enhance durability. This is an issue, especially during concrete pouring and curing processes, since a strong and efficient covering for steel reinforcements must be maintained to prevent the penetration of water and moisture that causes uncontrolled steel corrosion or volume increase.

Additionally, chemical admixtures may be added to the concrete mix with different purposes: to speed up or slow down the hydration process (accelerators or retarders), entrain air bubbles (air entrainments), increase the workability of plastic concrete paste (plasticizers and super plasticizers), minimize the corrosion of steel reinforcements (corrosion inhibitors), improve pumpability (pumping aids), or color concrete paste (pigments).

Other fine materials may also be added to the mix to improve concrete properties (durability, compressive strength, and workability) or as a replacement for Portland cement, such as fly-ash, blast furnace slag, and silica fumes.

Concrete production may take place either in ready mix concrete plants, in which all components (except water) are mixed together, or central mix plants, where all components including water are mixed. The latter offers more control over concrete quality, but requires the plant to be close to the construction site, since the process of hydration begins immediately and concrete may harden during transportation.


Glob

al W

arm

ing

Pote

ntial

, kgC

O2e

/kg

Embo

died

Ene

rgy,

MJ/

kg

Compressive Strength, KSI

EPDs of concrete

y = 0,0891x + 0,7826

y = 0,0166x + 0,0739

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,70

0,90

1,10

1,30

1,50

1,70

1,90

2,10

2,30

2,50

0 1 2 3 4 5 6 7 8 9 10

Embodied EnergyGWPProjected Embodied EnergyProjected Global Warming Potential

Figure 5.6: EPD Trends for Concrete Source: CTBUH

66

Once concrete is delivered to the job site by truck, it is poured into formworks and hardens, assuming the shape of the formwork it is poured into. The first few days after concrete pouring are essential to guarantee strength and prevent cracking. The curing process calls for controlling temperature and humidity conditions carefully; covering, spraying, or ponding concrete surfaces with water allows hydration chemical reactions to take place and prevents water evaporation.

From an energy standpoint, little is spent on the concrete mixing process and the environmental characteristics of concrete are mainly determined by the ingredients of the mix, which will be analyzed separately in the following section. From a transportation perspective,

concrete plants are nearly ubiquitous in developed regions, even in the proximity of metropolitan areas. Therefore, concrete has to travel shorter distances compared to other building materials. However, being a heavy material, its transportation requires many truck loads and the environmental impacts of this are significant.

5.5 Environmental Data for Concrete

As shown in the inventory of materials for each scenario (see after the conclusions), the most common concrete used in the analyzed structural designs is “normal” C30/37 concrete. This concrete grade is being used for the creation of the composite floor system in steel-based scenarios, and to create the whole floor

assembly in all-concrete scenarios. For this material, environmental data are extensively available in the Ecoinvent database and the average values for European production are used for this research. On the contrary, no information is available for the higher-grade concretes being used for the vertical structures. The basic materials that constitute concrete, which were presented in the previous section, can be mixed in different proportions to create concretes with different properties. The “recipe” for these proportions is called the mix-design. Depending on the desired characteristics of the final product (i.e., cost, strength, workability, resistance to chemical substances, etc.), the amount of each material can vary significantly (Bharatkumar, Narayanan, Raghuprasad, &


67

Ramachandramurthy, 2001). From a LCA perspective, this can have very important implications in terms of the Embodied Energy (EE) and Global Warming potential (GWP) of the final product.

According to a study by the National Ready Mix Concrete Association (Nisbet, Marceau, & VanGeem, 2002), where an LCI of concrete products ranging between 20 and 70 MPa of compressive strength are presented, cement manufacturing represents the largest share of EE for the product, ranging between 69% and 84% of the total, with the highest shares corresponding to the highest concrete grades. The impacts of cement are even higher when CO

2 emissions and GWP are

considered, due to CO2 being releasing

not just as a consequence of the energy used during its production, but also in the chemical reaction as limestone transforms into cement (see Section 5.1).

For this reason, reductions in the amount of cement in the mix can have a major impact on its environmental properties (Khan & Siddique, 2011). For instance, the use of fly ash as a cement substitute can substitute a certain portion of cement (as much as 70%) with a by-product of other industrial processes (Dinakar, Kartik Reddy, & Sharma, 2013).

However, cement substitutes may have an impact on other characteristics of concrete, such as curing time and hydration heat, so the appropriate mix should be selected according to each specific case (Alves, Cremonini, & Dal Molin, 2004). As a consequence of the variability in the ingredients that constitute a concrete mix, it has not been possible to identify environmental values for specific concrete mixes. As a consequence, average values for the concrete mix being used in the case studies have been identified by

comparing over 1,400 Environmental Product Declarations (EPDs) from different concrete producers that operate in the San Francisco Area. These mixes present a great variability within each strength class, thus reinforcing the idea that a single value is unrepresentative of the many possibilities available. Also, no EPDs were available for concrete grades with a compressive strength above 50 MPa (7.5 kPSI); consequently, such environmental values were obtained with a linear projection of the GWP and EE contents of the lower concrete grades (see Figure 5.6).

In order to ensure the reliability of the results, and to show the major discrepancies that can arise with various design mixes from an environmental perspective, a second set of results was sought. This data was obtained from the French Syndacat National du Beton Pret a l’Emploi through the online BETIE (Beton et impacts environnementaux) tool (see Table 5.1). In this system, values existed for concrete with compressive strengths of 30, 40, 50, 60, and 80 MPa. Consequently, the environmental data of grade 55 concrete was obtained by averaging the values of 50 and 60 MPa concretes, while the data for 70 MPa

concrete was obtained by averaging the values of 60 and 80 MPa concretes. Because of the silica fume contained in the concrete mix for the 80 MPa concrete, which is used to reduce the heat released by cement, the environmental data of the 70 MPa concrete is actually slightly better than the 55 MPa concrete, highlighting the variability of results across different concrete mixes.

By comparing the results of these two data sources for similar compressive strengths, major differences become evident. Such differences can be caused for a number of reasons. A non-comprehensive list includes:

• Different production systems: Small variations in the chemical composition of the raw materials can cause different emissions of CO

2, especially during the chemical

reaction that produces cement.

• Different energy sources and energy mixes in the local power supply: A wide range of fuels can be used to produce the heat in a kiln. These can include natural gas or solid energy sources, including trash and used tires. Also, operations relying on electricity can have very different environmental impacts depending

Derived from BETIE Derived from EPDs

GWP [kgCO

2Eq./kg]

EE [MJ/kg]

GWP [kgCO

2Eq./kg]

EE [MJ/kg]

C30-37 0.11 0.83 0.15 1.22

C40 0.15 1.12 0.17 1.28

C55 0.17 1.25 0.20 1.49

C70 0.16 1.23 0.24 1.67

Table 5.1: Environmental Values Used for the Different Concrete Grades, as derived from the online tool BETIE and from concrete EPDs in the San Francisco areaSource: CTBUH


Fig. 5.7: Concrete recycling Source: Dario Trabucco

68

on the sources of the electricity supply in that area. Gas- or oil-powered plants, hydroelectric plants, and nuclear power plants all have varied carbon intensities per unit of distributed electricity.

• Different efficiencies in the production process: Varied and obsolete technologies can drastically affect the efficiency of production operations.

Additionally, it should also be remembered that the accounting method used while compiling the Life Cycle Inventory of each specific product plays a major role in the precision of the final results because some of the operations may have been disregarded or overlooked when the information was collected.

For this reason, the scenarios in this research were analyzed twice using both sets of environmental values. It is important to note that the environmental impacts represented here should not be considered as two ends of the spectrum in terms of efficiency. On the contrary, the fact that both values are derived from developed economies in areas with well developed environmental regulations (France and California) indicates that these represent good concrete production practices. Consequently, more negative

environmental values for concrete are likely to be found for cements produced in less-developed economies.

5.6 Recycling of Concrete and Aggregates

Construction and Demolition Waste (CDW) represents a large share of the waste stream in most countries. It is responsible for about 32% of the 3 billion tons of total waste generated in Europe (European Environment Agency, 2010). It represents 154 million tons of waste in the US (Environmental Protection Agency, 2003) and 17.5% of China’s waste production (Urban Development Working Group, 2005). In Europe, concrete and other mineral debris represents the largest portion of CDW, though it varies by country due to the different construction techniques adopted. On the contrary, wood debris is the largest residential CDW in the US, while concrete is the more common material in non-residential CDW (Environmental Protection Agency, 2003). In Europe, CDW is recycled with varying percentages of efficiency, ranging from 98.1% in the Netherlands to 13.6% in Spain (Fischer & Tojo, 2011), but awareness of the problem is rapidly rising everywhere (Nitivattananon & Borongan, 2007).Landfilling of CDW is now forbidden in an increasing number of countries and,

even where it is still allowed, landfill taxes are applied per ton of disposed material, making concrete an extremely expensive material to discard. CDW recycling sites accept incoming concrete waste and transform it into recycled aggregates (RA) and other byproducts with market value.

Increasing the recycling percentages of CDW depends on the quality of debris and their on-site subdivision into different batches of homogeneous materials. Unlike low-rise residential projects, where a multitude of materials are used (Environmental Protection Agency, 2003), infrastructures and tall buildings are largely composed of two primary materials (reinforced concrete and steel) and economies of scale can be realized to facilitate an accurate sorting of debris from those representing smaller quantities, such as plaster, tiles, bricks, and carpets.

Demolished concrete piles can either be processed on site, such as in the case of road construction (where crushed concrete is directly re-used as recycled aggregate), or transported to a processing facility for off-site crushing and sorting. Tall buildings tend to be located in dense urban environments and on-site crushing is typically prohibited due to noise and dust pollution. However, a certain degree of material sorting occurs during the demolition process, when large steel components (beams, corrugated sheets, etc.), aluminum, and other metals are separated from concrete for immediate recycling through the use of crushers and hydraulic shears mounted on robots and excavators.

Different strategies exist to crush concrete blocks offsite. The first step usually consists of the primary crushing of blocks through an impact crusher that creates blocks approximately 80 mm in diameter. The output of the impact crusher is then


69

conveyed through a magnet that attracts steel reinforcements that once formed reinforced concrete. Crushed materials are then processed a second time, either with an impact crusher, rotary crusher, or through more innovative systems, explained below. This technique produces recycled aggregates that can be used as filling material after being washed. The finer dust produced is usually hauled to a land fill, though some alternative uses are being assessed.

Transportation to the processing facility or landfill happens exclusively by truck and the distance travelled plays a fundamental role in the overall economic and energy balance of disposing/recycling crushed concrete (Marinkovic’, et al., 2010). Visits to Bluff City Materials, a CDW processor in the Chicago Area, showed that incoming loads (trailers or semi-trailers) are accepted free of charge if the demolition company hauls the material to the company’s main facility located 52 kilometers west of the city center, while Bluff City charges about $2.50 per ton if the material is hauled to their facility located 12 kilometers from the city center. Figures may vary if concrete is mixed with other CDW.

If the quality of the incoming crushed concrete doesn’t meet specific requirements, the full load can be refused, as an excessive presence of other CDW can exceed the necessary levels of quality assurance for reuse, even as a road backfill material (Wahlstrom, et al., 2000).

End-of-life concrete has always been viewed as a waste material with limited reuse possibilities because of the decreased quality of the product compared to natural aggregates (downcycling). Even after World War II, concrete and crushed masonry from bombed buildings were used as filling materials for the construction of road

beds, river banks, and other infrastructure. Such applications still represent the most common use of crushed concrete. In recent years, new possibilities have been investigated, predominately because of the excessive production of CDW in relation to the demand of filling materials. Among these, one of the most advanced programs is represented by the EU funded C2CA research (Advanced Technologies for the Production of Cement and Clean Aggregates from Construction and Demolition Waste - Grant Agreement n.265189), whose aim is to explore the possible uses of recycled aggregates from end-of-life concrete. According to the most advanced research in the field, innovative systems, including flow cavitation disintegration, high performance sonic impulses, thermal-mechanical beneficiation, microwaves, and electric discharges can be used to weaken the cement paste that binds aggregates together in concrete, so as to obtain, through fine crushing, a better separation of aggregates from the cement paste (Menard, et al., 2013). The cement paste obtained with this method can be used as meal for the production of new cement clinker (Galbenis & Tsimas, 2006), while sand (Ulsen, et al., 2013) and aggregates can be used for the production of new concrete, both for non-structural (Soutsos, et al., 2011) and structural applications (Wagih, et al., 2013) even if the performance differences between concrete using natural or recycled aggregates are well debated in literature (Rao, et al., 2007). Tests have been carried out to assess the structural characteristics of highly “sustainable” concrete samples using a mix of recycled aggregates and fly ash cement, but results have not been satisfactory, with compression and tensile strengths being seriously compromised when substitution rates exceeded 30% of both aggregates and cement (Kim, et al., 2013).

Evidence shows that the environmental benefits of recycling concrete are limited and they can only be increased if broader system boundaries than those used in standard LCA analyses are included, particularly if social aspects and economic costs are included through a Life Cycle Sustainability Assessment (LCSA) (Hu, et al., 2013). Even in countries where the use of recycled aggregates is regulated, such as in Switzerland, cultural and economical barriers prevent a diffused use of recycled aggregates for high-profile applications (Knoeri, et al., 2011). However, natural resource depletion and land fill saturation are a growing concern in developed countries and increasing legislation will continue to promote research and development in this field.

As for today’s research, the increased porosity and water absorption of recycled aggregates (Rao, et al., 2007) requires greater cement content (approximately 5% more) compared to natural aggregate concrete. Because of the large energy consumption and CO

2 emissions of

cement production (Hammond & Jones, 2008), the increased quantity of the bonding components shifts and annuls the environmental benefits of using recycled aggregate (Marinkovic’, et al., 2010). For this reason, and the purposes of this research, end-of-life concrete is supposed to be used as a recycled filling material only, and it is credited to the end-of-life scenario accordingly.

The recycling plant visited for this research requires, on average, 3.5 KWh and 0.7 liters of diesel per ton of recycled aggregate produced (only energy used on site). These values provide a combined energy consumption of 38 MJ per ton. This number is higher than those that the reference found in the literature, such as the 18.1 MJ/t calculated by Marinkovic’ (Marinkovic’, et al., 2010).


6.0 Fireproofing Materials: Cradle to Grave


Figure 6.1: Standard Time-Temperature Relationship for Fire Tests (Left) and Steel Strength Decreases with Temperature (Right)Source: CTBUH

72

6.0 Fireproofing Materials: Cradle to Grave

Section Factor [H

p/A]

Cementitious Sprayed-On MaterialsDry Thickness in mm to Provide Fire Resistance for up to:

0.5 h 1.0 h 1.5 h 2 h 3 h 4 h

30 10 10 14 18 26 35

50 10 12 17 22 33 43

70 10 13 19 25 37 48

90 10 14 21 27 39 52

110 10 15 22 28 41 54

130 10 16 2 29 42 56

150 10 16 23 30 44 57

170 10 16 23 30 44 57

Notes: For castellated or cellular beams, or fabricated beams with holes, the thickness of the fire protection material should be 20% more than the thickness determined from the section factor of the original.

Table 6.1: Requested Thickness of Typical Spray Cementitious Fire Protection MaterialSource : ASFP Yellow-Book, 4th Edition 2012

The fire resistance of a structure or a material is usually expressed by a number that represents, in units of time (minutes), their capacity to withstand the high temperatures of a fire before losing their mechanical characteristics. Concrete is not inherently susceptible to fire, but reinforced concrete can suffer serious problems if it is not adequately protected; in fact, the internal tensions generated by heat can cause spalling, a quick erosion of the thin concrete layer that protects the steel reinforcements. If the contained steel rebar is exposed to the heat generated by a fire, it will lose its strength capacity, thus causing a collapse of the entire reinforced concrete element. In general, a reinforced concrete structural element is self-protecting against fire, simply because the layer of concrete that protects the steel rebar is thick enough to prevent exposure. Composite elements (formed by steel profiles encased in concrete elements) are completely self-protecting, as the layer of concrete encasing them is, for structural reasons, much thicker than what would be required for fire-protection purposes. Modern safety standards require the installation of auto-shutoff systems, but fireproof-treatment for structures must still be achieved in order to ensure appropriate fireproofing in case of an out-of-service sprinkler system.

For steel, the process of losing strength starts at about 300°C and increases rapidly after 400°C. At 550°C, steel conserves only 60% of its characteristic yield strength. Usually, an unprotected steel section loses its load-bearing capacity within 30 minutes (BauForumStahl 2008) (see Figure 6.1). In steel design, the “section factor” is a parameter that relates the geometry of a section to the heating rate of the elements:

Section Factor = Hp / A

Hp identifies the Heat perimeter of the steel

section; A is the sectional area of the profile.

From this equation, it is clear that a massive section will heat up slower than a light, slender section. To avoid the risk of collapse due to fire, different passive fireproofing systems are used in steel construction. To ensure adequate fire safety and prevention, it is necessary

to use special coatings or claddings for steel structures and utilize concrete cover cases of appropriate size and thickness for RC structures (Tomasetti, et al., 2005) (Cowlard, et al., 2013) (see Table 6.1).

This research is aimed at comparing the environmental implications of different structural systems and solutions from a life cycle perspective. Consequently, the

| Fireproofing Materials: Cradle to Grave

Standard Fire Test BS476 Part20

High Temperature Steel Properties

1200

1000

800

Tem

pera

ture

°C

Room

Tem

pera

ture

Str

engt

h Ra

tio

600

400

200

0 0 200 400 600 800 1000 1200 14000.0

0.2

0.4

0.6

0.8

1.0

20 40

Time (minutes) Temperature °C

60 80 100 120


73

Pro Cons

On-SiteApplication

NonReactive

Board

• Appearance• Fixing• Quality assured• Surface preparation is

not required

• Cost• Application• Speed

Sprayed-On

• Cost• Application• Durability• Surface preparation is

not required

• Appearance • Overspray needing

Flexible/Blanket Systems

• Low cost• Fixing

• Appearance

Concrete Encasement

• Durability

• Cost• Time requested• Space utilization• Weight

ReactiveThin Film

IntumescentCoatings

• Aesthetics• Finish• Application• Servicing

• Cost• Application• Limited fire-

resistance period

Off-SiteApplication

ReactiveThin Film

IntumescentCoatings

• Reduced construction time and relative costs

• Simplified installation• Standard of finish,

quality, and reliability• Reduced on-site

activities

• DFT is dependent on the steel section used (Hp/A)

Table 6.2: Summary of Principal Fire Proof TechnologySource: CTBUH

different structural possibilities under analysis have to be comparable across a similar level of fire protection. For this reason, the environmental consequences of a fire-proofing layer are added to the steel components of steel structures in order to ensure comparable fire behavior with concrete and composite structures.

In current international building code, the minimum required fire resistance has been changed from four hours to three hours (Gilsanz, 2008). For tall buildings in particular, the code requires that buildings must maintain their structural performance for a duration of three hours, ensuring not only the total evacuation of the building, but also an acceptable level of safety for the preliminary fire-brigade response that will extinguish the fire.

6.1 Types of Fireproofing Materials

Passive fireproof materials (PFPM) can be divided in two families: non-reactive and reactive (see Table 6.2).

Intumescent fire resistive material (IFRM) coatings are made from paints that are inert at low temperatures, but provide insulation as a result of a complex chemical reaction at temperatures of approximately 200-250°C (see Figure 6.2 and 6.4). Typical expansion ratios of an IFRM coating are about 50:1, so a 1 mm-thick coating will expand to about 50 mm. In order to ensure optimal fire-resistance efficiency, the thickness of the intumescent film is calculated based on the A/V ratio. In this way, optimizing structural steelwork to ensure the lightest elements may prove disadvantageous when considering the costs related to the application of intumescent paints. Thin film intumescent coatings can be applied on-site or off-site, and their main advantage is their capacity to cover complex shapes.

In terms of sustainability, during recent years, companies have developed “green” intumescent paints. In fact, in reference to ISO9001:2008, intumescent coating are water-based and include low Volatile Organic Compounds (VOC) formulations.

Non-reactive protective materials can be classified in three broad families: Boards, Sprayed mineral coatings, and concrete encasements.

The use of boards (plasterboards, gypsum-made boards, etc.) is a non-reactive solution to protect steel elements from fire. This technology offers a cleaner solution as it represents a dry mode of

construction. Another advantage is the possibility of covering structural steelworks without the pre-treatment of steel surfaces. The required thickness of the boards depends on the location of steel sections, the number of fire exposed sides, and the fireproofing time request.

Sprayed mineral coating technology consists of a paste that is sprayed on a protected surface. The treatment of steel elements is usually not required, especially when the protective coating is based on Portland cement. Like IFRM, sprayed-on cement or mineral coating systems can be used to protect complex shapes. To ensure better adhesion and

Fireproofing Materials: Cradle to Grave | © Council on Tall Buildings and Urban Habitat

Figure 6.2: One World Trade Center, 2014, New York City during construction, sprayed-on fire protection is used on all steel elementsSource: Dario Trabucco

Figure 6.3: Use of Concrete for Protecting the Steel Component in the Seagram Building, 1958, New York CitySource: CTBUH

74

an adequate retention of the sprayed protective material, metal mesh made of galvanized steel is often used around larger structural elements. This solution is avoided whenever possible due to the high installation cost of such mesh.

One of the oldest methods of increasing the fireproofing performance of steelworks is concrete encasement. Examples of this can be found in many tall buildings from the past, including Mies’s famous Seagram Building in New York (see Figure 6.3). Until the late 1970s, concrete was the most used material to ensure an adequate fire-resistance for steelworks. On one hand, this solution ensures high levels of durability, but on the other hand, it involves significant loads added to the building structure, provides inefficient space utilization, and elevates costs (compared to lightweight systems).

6.2 Environmental Impacts of Fireproofing Materials

Research was conducted by reaching out to many international producers of fire-insulating materials. This yielded unsatisfactory results due to the fact that LCAs are not commonly performed by members of this industry. For intumescent paints, contacted companies use a “sustainable” label for water-based products that omit chemical solvents and for the reduction of volatile organic compounds (VOC) in their products.

In general, technical datasheets provide a wealth of information about the performance of each product, but

“...The most common fireproofing solutions

adopted in tall buildings is the use of spray-on mineral coatings, which are

capable of providing a cheap and reliable

insulation...”

| Fireproofing Materials: Cradle to Grave © Council on Tall Buildings and Urban Habitat

Figure 6.4: One World Trade Center, 2014, New York City during construction, sprayed-on fire protection is used on all steel elementsSource: Dario Trabucco

75

unfortunately, values for embodied energy and embodied carbon are not available, except for plasterboard or gypsum-based materials. In the US, some gypsum-based plasterboard companies founded the “Gypsum Association” and, in February 2013, conducted a LCA study.

The research found the GWP of 1 square foot of 1.25 cm and 1.60 cm plasterboard to be 233.3 and 315.4 kg CO

2Eq. respectively.

However, the most common fireproofing solutions adopted in tall buildings is the use of spray-on mineral coatings, which are capable of providing a cheap and reliable insulation that is applied on vertical and horizontal structural

elements soon after their installation in the building. Spray-on fireproofing material has been estimated as the sum of its basic components, so in the case considered, cement and polystyrene fibers. A specific LCA was then conducted on this paste and a GWP of 0.26 kg CO

2Eq. and an EE of 4.37

MJ for each kg of paste was determined. The density of such compounds is approximately 240 kg/m3.

Grace, a fireproofing producer that operates in the US market communicated to the CTBUH that its products are being certified with a GWP of 0.22 kg CO

2Eq.

per kg and an EE of 2 MJ for each kg of sprayed-on concrete. The environmental information obtained by Grace have been

used for the fireproofing material in this research, which is applied with a 2.5 cm layer around vertical steel columns and the primary floor beams.

Fireproofing Materials: Cradle to Grave | © Council on Tall Buildings and Urban Habitat

7.0 Transportationand On-Site Energy Use


78

YearGasoline

[PJ]Diesel

[PJ]Total[PJ]

ConstructionIndustry

Total[PJ]

Light Trucks(on-highway)

1997 6260 250 6510 400

2002 6940 270 7210 3440

Medium/Heavy Trucks(on-highway)

1997 490 3820 4310 740

2002 600 4690 5290 910

Construction Equipment(off-highway)

1997 38 700 740 740

2002 36 800 840 840

Total1997 6790 4770 11550 1880

2002 7570 5760 13330 2190

Table 7.1: 1997 and 2002 Estimates of Gasoline and Diesel Use for Construction in Petajoules in the US, per YearSource: Sharrard, et al., 2007

7.0 Transportation and On-Site Energy Use

Transportation and on-site operations are often omitted from many analyses on the sustainability of buildings. This is due to the assumption that such operations play a marginal role in the environmental impact of buildings. Because of the unique factors involved in tall building projects, this research examines these impacts to confirm or deny this assumption.

The complexity of the construction site has direct consequences on an environmental impact assessment. Unlike ordinary manufacturing industries, the products of the construction industry are always complex and unique, including a wide range of techniques and systems. Therefore, it is not possible to apply a globally recognized value for the environmental impact of each building (Gangolells, et al., 2011).

The construction phase of a building is accounted for in stage “A5” of the LCA analysis scheme, according to the European Norm 15804, and it might play an important role in the total environmental impact of the building due to the necessary use of heavy equipment

(often diesel fueled), temporary and consumable material use, and waste generation (Guggemos & Horvath, 2006).

7.1 Transportation and On-Site Operations in Literature

On-site construction processes can cause soil and ground contamination, atmospheric emissions, waste generation, resource consumption, and more (Gangolells, et al., 2009). One important environmental impact of the on-site construction phase is waste generation. In order to obtain a sensible reduction of on-site waste production, construction design and management should be well-planned, minimizing excess construction materials (Oka, et al., 1993). Asdrubali (Asdrubali et al., 2013) divided the construction phase into three sub-systems: the material production phase, building construction phase (the main topic of this section), and the “end-of-life” phase.

In a Life Cycle Energy Assessment (LCEA) (Ramesh, et al., 2010) (Buyle, et al., 2013) (Cabeza, et al., 2014), the amount of energy used on-site for

building construction is computed in the Initial Embodied Energy (IEE: energy “contained” in all the materials used in the building and technical installations) that contributes to the determination of the Life Cycle Energy (LCE) value, together with Recurring Embodied Energy (REE: energy involved with the repair and replacement/rehabilitation of the building), Operating Energy (OE: energy used to maintain comfort conditions), and Demolition Energy (DE: energy from demolition and transporting waste to landfills) (Dixit, et al., 2012) (Plank, 2005). In order to reduce not only the operational energy demand, but also to ensure that attention is paid to the impacts caused by building construction, the minimization of initial embodied energy must be taken into account, especially for the design of buildings involved in a nearly-zero-energy design strategy.

Construction phases are often neglected by LCA analyses (Sharrard, et al., 2008) (Srinivasan, et al., 2014), but this value can be very important. Despite the fact that most of the energy consumed during the life of a building is concentrated on the “use phase” (with operational consumption caused by HVAC systems, lighting, etc.), an optimization of the construction site and the construction process can ensure that energy and material waste is minimized from the beginning of a building’s life cycle. It’s useful to note that in the United States, 30% of total energy consumption, 60% of electricity use, and 16% of potable water goes toward the operation of buildings (USGBC, 2009) (Haney, 2011).

Total on-site energy consumption includes the sum of the energy needed for excavation (digging, excavation, and groundwork), the foundation construction process, material handling (with cranes), and pumping concrete to upper levels.

| Transportation and On-site Energy Use © Council on Tall Buildings and Urban Habitat

79

Energy Consumption

GWP[%]

Constr.Phase

Material Manufacturing

94.89 % 95.16 %

Transportation 1.08 % 1.76 %

On-Site Construction

4.03 % 3.08 %

Total 100% 100%

Table 7.2: Distribution of Energy Consumption and GWP in the Construction Phase of a Typical Residential BuildingSource: Hong, et al., 2014

Execution PhasePercentage

of CO2 Emission

Tower Crane 39%

Excavator/Backhoe 26%

Generator 15%

Steel Bending Machine 3%

Material Hoist 2%

Passenger Hoist 3%

Gondola 2%

Concrete Vibrator 1%

Submersible Pump 1%

F.S. Pump 2%

Vibrator Rammer/Plate Compactor

2%

Compaction Roller 3%

Rock Drill Machine 1%

Total 100%

Table 7.3: Distribution of Energy Consumption of On-Site Construction Equipment for a Case Study Residential Building from the LiteratureSource: Wong, et al., 2013

Execution Phase Percentage

Pit Support Construction 59.40 %

Excavation 18.30 %

Site Cleaning 12.30 %

Backfill Rank 7.50 %

Dewatering Operations 2.50 %

Total Value 100.00 %

Table 7.4: Distribution of Environmental Impacts for an 11-Story Building in Beijing Source: Li, et al., 2010

Most of the existing literature analyzes the “construction phase” in terms of environmental impacts, evaluating/estimating the amount of polluting substances (NO

x, CO, HC, SO

x, etc.) emitted

by “non-road” vehicles (Sharrard, et al., 2007), or trying to calculate this data with the EPA2004 formula (Ahn, et al., 2009) (Zhang, et al., 2014) (E.P.A., 2009) (see Table 7.1).

Emission = Engine Power (hp) * Operating hours (hrs) * Emission Factor (g/hp-hr) * Load Factor

Some literature focuses on the important role played by “site-operation” simulators to minimize waste, optimize working-time, and reduce economic costs (Olearczyk, et al., 2014) (Wong, et al., 2013) (Hasan, et al., 2013) (Hajibabai, et al., 2011).

Some US construction industry energy consumption data collected in 1997 are available in the bibliography. From these, it is possible to note how, for that year, the construction industry represented 3.7% of industrial electricity purchases and 0.8% of overall electricity use in the U.S. In the same year, electricity purchased by the construction industry required 422,000 TJ of total energy (Matthews, et al., 2005). Another study (Sharrard, et al., 2007) compares 1997 and 2002 data on energy consumption related to the US construction industry, estimating the gasoline and diesel use for construction in PetaJoules (1015 J) (see Table 7.1).

Some researchers have demonstrated the importance of considering the construction phase to obtain a more detailed evaluation of a LCA analysis. Hong et al. (Hong, et al., 2014), for example, demonstrated the following subdivisions of energy-consumption during the construction phase for a residential building (LCA modules A+B) (see Table 7.2).

Some research uses a holistic hybrid model to evaluate a LCA (O’Donnell, et al., 2013) (Sharrard, et al., 2008). There are also studies that try to explain the importance of optimizing tower crane operations (Huang, et al., 2011) (Hasan, et al., 2013), excavation strategies (Hudson, 1993), and workplace optimization (Ismail, et al., 2013), to ensure optimal work conditions (minimizing waste and pollutant emission).

Research on low-carbon construction processes (Wong, et al., 2013), which are based on a case study of a residential building, demonstrated that the main cause of “CO

2 emissions” in the

construction phase are tower-cranes and excavation equipment (see Table 7.3). Another case study (Li, et al., 2010) based on an 11-story reinforced concrete frame building (45 meters, 48,036 m2) built in Beijing, demonstrated the following percentages regarding the total environmental impact of the construction phase (Table 7.4).

“Transportation and on-site operations are

often omitted from many analyses... due

to the assumption that such operations play

a marginal role on the environmental impact

of buildings.”

Transportation and On-site Energy Use | © Council on Tall Buildings and Urban Habitat

80

In this particular case, the largest amount of energy consumption belonged to excavation and site-clearing operations, because those operations required the use of heavy equipment such as bulldozers, trucks, and steamrollers, which require a large amount of diesel fuel. It is important to note that excavation and site-clearing operations are related to the specific case of each building site, and determining average values of energy-consumption data is difficult.

As shown (Haney, 2001), one of the most effective strategies to ensure lower energy consumption and emissions is characterized by the list reported in see Table 7.5.

Another author (Ko, 2010) suggests a “to do list” to make the construction phase as sustainable as possible:

• Choose the right machine for the task – avoid inefficiently oversized machines

Procedures

Percentage of Reduction for Construction Phase Energy Consumption

and CO2 Emissions

Sourcing Materials Within 500 Miles

17.5%

Shipping only Full Loads of Materials

8.5 %

Improving Site Logistics and Crane-Sizing to

Reduce Erection Time6.4 %

Switching from an 8-Hour to a 10-Hour

Work Day3.0 %

Total Reduction 35.4 %

Table 7.5: Possible Reductions in Total Construction Phase Energy Consumption and CO

2 Emissions

Source: Haney, 2011

• Select equipment that is more fuel efficient

• Service equipment correctly• Use sustainable, low carbon fuels• Operate equipment efficiently (e.g.

minimize idling time and using an appropriate amount of power)

In 2002, the US construction industry was one of the highest emitting sectors, producing approximately 1.7% of total US GHG emissions (equivalent to 6% of all US industrial sectors). In the same report, the EPA subdivided GHG emissions into three sub-categories: fossil fuel combustion, purchased electricity, and non-combustion activities. Construction industry GHG emissions are subdivided in the following tables using these classifications (see Table 7.6 and Table 7.7).

One of the main goals of construction phase optimization should be the reduction of waste and the minimization of impacts on the local community. A carefully designed process that makes these considerations can, at the same time, minimize waste directed to landfills and also save money by providing an efficient, safe, and expedient construction process (Plank, 2005).

For the purposes of this research, it was assumed that most sources of on-site energy consumption would be constant throughout all of the studied solutions. In fact, energy consumption related to site clearing, the construction of foundations, worker-related services, and lighting is not connected with building materials. However, it must be acknowledged that some differences exist in the vertical movement of building materials for the structural system, and that a different amount of energy for the hoisting of materials and pumping of concrete has been considered for each scenario.

“For the purposes of this research, it was assumed that most

sources of on-site energy consumption

would be constant throughout all of the

studied solutions.”

As seen in the existing literature (Goldenberg & Shapira, 2007) (Shapira, et al., 2007), there are five fundamental pieces of equipment needed during the on-site construction process: tower cranes, material handlers, concrete pumps, hoists/lifts, and forming systems (decks, etc.). Unfortunately, little information is available in the literature that can contribute reliable and complete information for the specific case of tall building construction.

In order to ensure useful and objective data of those on-site operations, two leading companies in the field of crane construction, Terex-ComEdil Cranes, and in the field of concrete pumps, Putzmeister, have been contacted to provide case-specific information to be inputted in the software model for the creation of the LCA analysis.

Also, the transportation of materials varies significantly depending on their point of origin.


81

FuelEmissions

[kg CO2

/ unit materials]

Estimate of Sector-Wide Emissions Reductions*

Using 3% Less Fuel Using 10% Less Fuel

Diesel 2.79 kg CO2/liter 2.02 x 1 million tons CO

26.73 x 1 million tons CO

2

Gasoline 2.34 kg CO2/liter 0.63 x 1 million tons CO


2

Propane 1.52 kg CO2/liter N.A.** N.A.**

Natural Gas 0.19 Kg CO2/m3 0.36 x 1 million tons CO


2

Notes: Emissions factor for diesel and gasoline were converted from EPA’s 2008 Inventory of Greenhouse Gases 1999-2006, Table A-29 and A30. Emissions factor for propane and natural gas were converted from EIA data sources.

MMTCO2 = million metric tons of CO

2*. Estimate of possible emission savings from percentage reductions are based on 2002

fuel consumption estimates used in the EPA report, Quantifying Greenhouse Gas Emissions in Key Industrial Sectors in the U.S. (May 2008). Numbers presented are for the purpose of illustrating the magnitude of possible reductions only and should not be interpreted as absolute quantities. No economic census data are available to estimate sector-wide propane consumption.

N.A.** = Data not available.

All numerical value are converted to the international metric system, assuming:1 US gallons liquid = 3.7845 liters; 1lb = 0.45359 Kg; 1 ft3 = 0.028317 m3)

Table 7.6: GHG Emissions Reduction Scenarios from Reduced Fossil Fuel Use for the USSource: E.P.A., 2009

For this reason, these two items of energy consumption have been assessed with greater detail in order to provide a case-specific result for each analyzed scenario.

7.2 Transportation

For energy consumption (and its relative environmental impacts), all considerations and values in this report are derived from the available data of the construction process for the identified case study (300 North LaSalle, as illustrated in Section 3.4).

A travel distance of 2 kilometers was assumed for concrete, which would be transported by a mixer truck (with a gross weight of 28 tons) from the nearest cement plant.

Structural steel sections were assumed to travel 163 kilometers, equivalent to the distance between the hypothetical building site and the nearest steel producer. That distance is reduced to 98 kilometers for steel studs and metal decking, which can be moved either with a small truck with

a 7.5-ton capacity or bigger one, with a gross weight of 30–40 tons.

Steel rebar and welded meshes were assumed to not only travel by truck (with a gross weight of 30–40 tons), but also by train (considering routes of 875 km for the steel rebars and nearly 1,700 km for the welded mesh). The energy consumption of debris transportation was also considered, with an assumed travel distance of 38 km in a truck with a gross weight of 12–14 tons for the concrete debris and 22 km (with the same kind of vehicle) for steel scraps (see Table 7.8).

7.3 Crane Operations

Cranes perform one of the most important roles during the construction phase. Given the scarcity of scientific literature about this topic (the bulk is concentrated almost exclusively on the placement of cranes and their optimization in terms of management), in order to be able to objectively assess their energy consumption, some case-specific information was obtained from Terex-ComEdil.

Some considerations have to be made in order to establish an accurate estimate of a crane’s environmental impact during the construction of a tall building. The crane’s operations during the construction phase of a building are not limited to the hoisting of materials, but they are used for a large extent of on-site material handling. Thus, the use of a simple parameter is not viable (i.e. Kw/ton/meter of height) to assess their global energy requirement.

Tall buildings require custom-designed cranes for their construction that must be designed in parallel with the design of the structures themselves. This optimizes construction times, reduces construction costs, and minimizes energy consumption.

Emissions SourceMillion

Metric Tons of CO

2Eq.

Percent of Total

Fossil Fuel Combustion 100 76%

Purchased Electricity 31 24%

Total 131 100%

Table 7.7: US Construction SectorGreenhouse Gas Emissions, 2002Source: E.P.A., 2009


Figure 7.1: One World Trade Center, 2014, New York City, during construction phaseSource: Dario Trabucco

82

It’s important to observe that these cranes (which are designed specifically for each building) experience a significant amount of wear by the end of the construction phase. It is often impossible to reuse them for the construction of another building. The dismantling of the crane should be anticipated in the design phase in order to minimize the risk of damaging the building’s façades and those of surrounding buildings.

One of the most important pieces of data needed to evaluate energy consumption of cranes is the duration of the construction period. In order to calculate these values, durations of 18 months for the 60-story tower (246 meters) and 36 months for the 120-story tower (490 meters) have been assumed based on a comparison with similar projects, with an assumed 12 hours of operation per day and 30 days per month. Such durations may seem shorter than the on-site construction of similar tall buildings, but this case only considers the construction time for structural systems, while in real building sites, construction proceeds on many simultaneous parts of a building.

In order to estimate a precautionary value as close as possible to the real value, three scenarios were established with varying load cycles (maximum, medium, and minimum). An average is then calculated from these three values. Using product information available on company brochures, an energy consumption of 160, 100, and 40 kW/h can be assumed for crane operations on the 60-story structure during the maximum, medium, and minimum load cycles. Such schemes may be associated with the different materials used for the construction of the tower.

Consequently, the maximum load scheme was used for the steel scenario, the minimum load scheme for the concrete


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Values Per Kg Truck

Distance [km]

Type of TruckTrain

Distance [km]

Concrete - - -

9-10ksi Concrete-C70 2

Mixer-TruckUp to 28 Ton Gross

Weight

-

8ksi Concrete-C55 2 -

6ksi Concrete-C40 2 -

4-5ksi Concrete - C30/37 2 -

Structural Steel Components

- - -

Steel Beams 163Truck-Trailer

30/40 Ton Gross Weight

-

Steel Columns 163 -

Steel Trusses 163 -

Reinforcing Steel Com-ponents

- - -

Steel Rebar 228 Truck-Trailer30/40 Ton Gross Weight

875

WWF 2 1698

Other Components - - -

Steel Studs 98Truck

Up to 7.5 Ton Gross Weight

-

Metal Decking 98Truck-Trailer

30/40 Ton Gross Weight-

Fireproofing Spray N.A. N.A. N.A.

Demolition Waste - - -

Concrete Debris 38 Truck12/14 Ton Gross Weight

-

Steel Scrap 22 -

Table 7.8: Mode of Transport and Travel Distance for Materials Considered in the StudySource: CTBUH

scenario, and the medium load scheme for the composite scenario. In this case, it must be remembered that the energy consumption of the concrete pumps will be added to the crane’s consumption in order to establish an estimate for the overall hoisting of materials.

For 60-story scenarios:

PowerMAX,MID,MIN

* 18 months * 30 days * 12 hrs

A bigger crane needs to be used for the taller tower, as heavier structural elements will need to be hoisted to greater heights. In this case, the energy consumption of the crane is considered to be 190, 110, and 60 kW/h for the maximum, medium, and minimum loading schemes. However, such values are only provided for a 200-meter construction scheme, while the 120-story scenario is 490 meters in height. Thus, the final result needs to be multiplied by 2.4 (490/200) to account for the increased hoisting consumption.

For 120-story scenarios:

2.4 * PowerMAX,MID,MIN

* 36 months * 30 days * 12 hrs

The results shown in the chart above have been used and inputted in the LCA models of each scenario as electricity coming from the grid. In some particular cases, however, an on-site diesel generator can provide the energy needed, but this case has not been assessed here.

7.4 Concrete Pumping

As previously mentioned, a further important role is played by concrete-pumping systems during the on-site construction phase.

Putzmeister, a global manufacturer of concrete pumps was contacted to obtain reliable average values of energy consumption.

According to Putzmeister, different factors have to be considered:

• The concrete mix-design (water/cement ratio, type of inert materials, quantity of fine particles in the mixture, and the presence or absence of certain additives) as well as external factors such as environmental temperatures play an important role regarding the friction factor of the concrete in the pipeline during the pumping phase.

• Increasing distance or prevalence (height) increases the power required for pumping and, consequently, the fuel needed (in pumps driven by diesel engine) or electrical energy consumed (with electric motors).

Keeping this in mind, a common industry approximation assumes an


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Figure 7.2: Deep-ground piles, like those at the Port of Tampa, Florida, US, can be extremely complex and expensive, which is why newer structures often re-use existing foundationsSource: (cc-by-public domain) OTB

energy consumption of 1 liter of diesel for each ton of concrete pumped at 100 meters. As pointed out several times by the manufacturer, this parameter lacks scientific relevance, as many factors influence the real equation. However, this rough estimate is used while speaking with clients in order to provide an estimate of the diesel that is used for concrete pumping.

7.5 Formworks

Formworks are needed in concrete buildings to create the shape of the cast for concrete elements before the concrete has cured to its final strength. These play a fundamental role in the construction of concrete buildings and the technology is rapidly evolving. The creation of a formwork system can often dictate the organization of a building site, and automatic systems

have been developed in the past few years to facilitate their installation.

However, formworks only have a marginal impact on the environmental balance of the construction process as their energy consumption is limited to transportation and hoisting. Their relatively low weight (compared to actual construction materials) makes them relatively low-impact and the quantification of the formwork system is therefore excluded by this analysis.

In terms of their embodied energy, formworks must be considered instrumental goods (as cranes, trucks, concrete mixers, etc) and their deterioration and eventual replacement can be consequently excluded from the quantification of environmental impacts caused by the concrete construction system.

7.6 Foundations

As described in Section 1.3, different types of foundations exist in tall buildings as a consequence of the soil conditions under the construction site. The geologic conditions that characterize each site are so varied, even in the relatively small area of a city, that it is not possible to identify a representative foundation technology

that is widely applicable for the research. Similarly, the foundations of very tall building, or those that are located in areas where horizontal loads are important, may be required to oppose the drift caused by the building rather than preventing it from “sinking” into the ground. For this reason, it can be argued that heavier buildings require more foundation structures as, in some circumstances, the weight of the building prevents the overturning forces transferred to the ground. As a consequence, the different solutions available vary remarkably in terms of material use and necessary machinery, and an inventory of materials for the foundation structures would not be realistic.

Also, it should be noted that foundations are rarely “demolished” at the end of a building’s life cycle. In fact, the removal of deep-ground piles and caissons would be extremely complex and expensive (see figure 7.2). On the contrary, existing foundations are often re-used for newer structures or, if they prove to be unsuitable for a new tall building, they can be “bypassed” with new piles dug in proximity to the old structure. Consequently, it would have been unpractical to account for the initial embodied energy of the building foundation, without the ability to include them in the end-of life scenario, as described in Section 8.

Accordingly, all underground foundation structures are not included in the present research, and the above-grade structures are considered as sitting on their “ideal” conditions.

Story Count

RC Structure

Hybrid Composite Structure

Steel Structure

60 st. 442 GJ 2,421 GJ 3,695 GJ

120 st. 6,515 GJ 11,887 GJ 21,604 GJ

Table 7.9: Crane Operation Energy Demand for All Case Studies Considered in this ResearchSource: CTBUH


85Transportation and On-site Energy Use | © Council on Tall Buildings and Urban Habitat

8.0 The End-of-Lifeof Tall Buildings


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Building Name City Height Year of Demolition Reason for Demolition

One World Trade Center New York City (US) 417 m 2001 Uncontrolled collapse due to terroristic attack

Two World Trade Center New York City (US) 415 m 2001 Uncontrolled collapse due to terroristic attack

Singer Building New York City (US) 187 m 1968 Demolished to make room for 1 Liberty Plaza

Seven World Trade Center New York City (US) 174 m 2001 Uncontrolled collapse due to terroristic attack

Morrison Hotel Chicago (US) 160 m 1965 Demolished to make room for the First National Bank Building (now Chase Tower)

Deutsche Bank New York City (US) 158 m 2011 Irreparable damages caused by previous terroristic attack

One Meridian Plaza Philadelphia (US) 150 m 1999 Irreparable damages caused by fire

Table 8.1: Recent Cases of Demolished Tall Buildings (italics denote buildings demolished through catastophic events)Source: CTBUH

8.0 The End-of-Life of Tall Buildings

The CTBUH Skyscraper Center database (Council on Tall Buildings and Urban Habitat, 2015) shows that only seven buildings taller than 150 meters have ever been demolished to date (see Table 8.1). However, this list includes the two tallest buildings ever demolished, the World Trade Center Twin Towers, which collapsed as a consequence of the terrorist attacks of September 11, 2001, together with Seven World Trade Center that collapsed at the same time. Excluding these three cases, only four buildings taller than 150 meters have ever been voluntarily demolished, with the 187-meter Singer Building (demolished in 1969) holding the title of the tallest building ever dismantled, followed by the 1965 demolition of the Morrison Hotel in Chicago. Interestingly, the Deutsche Bank building in New York City and the One Meridian Plaza in Philadelphia (respectively the 6th and 7th tallest in the list) have been demolished, though not as proper demolition projects, but as a result of consequences suffered during two catastrophic events (9/11 for the former, and a fire occurring in 1991 for the latter).

Except for a few demolitions that cleared the way for the construction of bigger towers during the 1970s, one could say that significant tall buildings are almost never demolished. A number of options exist to rejuvenate old towers (Trabucco & Fava, 2013) and demolition is typically not the preferred response to the evolution of market needs, but more demolitions will likely take place in the future as many tall buildings are now approaching the end of their service lives.

Fast growing economies are putting ever increasing pressures on city centers, with a continuous demand for new offices, luxury hotels, and trophy residences. While nobody argues that many iconic buildings are likely to grace a city’s skyline for centuries, evidence shows that typical tall buildings suffer from a much faster aging processes, not in terms of structural and material obsolescence, but in terms of functional obsolescence. One of the most striking examples may be the 142-meter Ritz-Carlton hotel in Hong Kong that was demolished a mere 16 years after construction to be replaced with a taller office tower as a consequence of Hong Kong’s booming office market.

8.1 High-Rise Demolition Techniques

Implosions are the most dramatic way to demolish buildings and they have been adopted in a number of cases (Liss, 2000), especially in the US. At 125-meters, the Great Hudson Store in Detroit is the tallest building ever imploded. Though this system is still widely used, it is being banned in most downtown areas due to the heavy impact it has on the city in terms of dust and pollution. Even where it is allowed, assurance liabilities and preparative mitigation works on nearby buildings make this system unsuitable for large-scale tall buildings in dense urban environments. On February 2013, the 116-meter AfE Turm in Frankfurt, Germany was imploded, making this the second-tallest building ever demolished with explosives, though it likely had a bigger volume than the Great Hudson Store.

A slight variation of the implosion system is the controlled collapse system, which has been applied at its largest scale on a 14-story residential block in Vitry-sur-Seine, France. With this method, the load bearing structural system of the building is weakened in a convenient location

| The End-of-Life of Tall Buildings © Council on Tall Buildings and Urban Habitat

Figure 8.1: Kajima Demolition Method applied at the Kajima HQ, JapanSource: Kajima Corporation

Figure 8.2: Taisei Corporation’s Ecological Reproduction System (Tecorep) applied at the Grand Prince Hotel, JapanSource: Taisei Corporation

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Building Name HeightDuration of Demolition

WorksNotes

Deutsche Bank, New York 158 m 48 monthsActual duration of 47 months,

demolition halted for 9 months due to a fire

One Meridian Plaza, Philadelphia 150 m 24 months -

Ritz-Carlton, Hong Kong 142 m 12 months Small floor plate

Hennessy Centre, Hong Kong 140 m 18 months -

Table 8.2: Duration of Demolition ProjectsSource: CTBUH

through pull-cables or hydraulic rams until the tower collapses on itself. The weight of the falling structure above the collapse point crushes the lower portion with an effect similar to the use of explosives. Though this system is less dangerous in some ways, it creates the same problems as explosives and is therefore unsuitable in dense urban environments.

Deconstruction (or dismantling) is a less-invasive demolition method that can be applied to any kind of structure and is the most widely adopted system for tall buildings. Deconstructing tall buildings is a long term task that sometimes requires more time than was needed for the construction of the tower (see Table 8.2). Before demolition starts, the building must be protected with scaffolds to prevent falling debris. The scaffolding system can be “traditionally” supported from the ground (and attached to the main structure) or suspended from the roof of the building and jacked down as deconstruction proceeds downward. The latter option was extensively covered by the media in two very recent cases: the demolition of the 74-meter UAP Tower in Lyon, France as well as the 140-meter Grand Prince Hotel Akasaka and the Otemachi Financial Center, both in Tokyo (Kayashima, et al., 2012).

Deconstruction requires the use of small excavators and other machines hoisted to the roof of a building. Structural elements are demolished through shears, torches, saws, and crushers. The limiting factors of this method is the load bearing capacity of the floor system (that needs to be able to carry heavy equipment and building debris), and the actual floor plan that may prevent the presence of multiple machines. Debris must be lowered with a crane and cannot usually be dropped via gravity into empty elevator shafts as this will cause vibrations, danger for the

The End-of-Life of Tall Buildings | © Council on Tall Buildings and Urban Habitat

Figure 8.3: The Despe TopDownWay system applied at the Bluevale and Whitevale buildings in ScotlandSource: Despe

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operators on the lower levels, and will wear out the lower portion of the shafts, threatening the structural integrity of the building.

An even more spectacular demolition process was used for the deconstruction of the Kajima Corporation Headquarter complex in Tokyo. The two office towers (the tallest standing 85 meters) were demolished from the bottom up, lowering the whole building with hydraulic jacks and deconstruction proceeded on the bottom levels (Mizutani & Yoshikai, 2011) (see Figure 8.1).

For the purposes of this research project, demolition methods using explosives or a progressive collapse have not been considered due to their impossible applications on large-scale buildings in dense urban areas. Also, the bottom-up

dismantling method described above has been disregarded because it is not applicable to buildings at the scale of those considered in this study.

Therefore, the technology that has been assessed in this study is a conventional top-down deconstruction method, which is similar to the techniques used in the largest demolition works to date.

8.2 Impact of Structural Materials on the End-of-Life of Tall Buildings

Primarily, the impacts that structural materials have on the demolition process are time-related. Building debris must be lowered using a crane that usually has a capacity of 10 to 20 tons. Therefore, fewer crane operations are required for lighter buildings.

Entire bays of the steel frame are secured with steel cables to the remaining structure; they are torch cut and dragged inward with a skid drive, then cut into smaller pieces and lowered to the ground with the crane. Materials are lowered either as bundles of steel pieces or inside of a skip bucket. Concrete elements are partially cut with a concrete saw or are weakened with a hydraulic concrete crusher, then pulled inward with a small loader. Large structural elements can either be lowered with a crane, or crushed into smaller pieces and dumped into a skip bucket. Chutes can be used only for small amounts of materials and their use is normally unbeneficial in terms of time savings. Horizontal partitions (floors) are usually hammered from the level above or crushed from below, and small pieces of debris are usually dumped into large buckets before being lowered.


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The type of structural system and structural material is, according to an industry survey, the driving factor in standard demolition works where multiple options are available (Abdullah & Anumba, 2002). As this study excluded the implosion/controlled collapse scenarios for the above mentioned reasons, the only remaining option is the top-down dismantling of the structure.

Methods of intervention and types of machinery vary according to the structural material of a building, but more importantly, the structure of a building largely impacts the duration of the demolition process. Concrete buildings are more complex to dismantle than steel buildings. Composite construction tends to vary, depending on whether the structural elements are demolished with a diamond cable (that cuts through all materials) or through the use of two different demolition technologies: a crusher to break concrete (to expose the steel profile), and a shear or a torch to cut the steel elements. The expected demolition times are described below, as provided by the three demolition companies involved in the survey (see Table 8.3).

Obviously, concrete is abundantly present in concrete buildings, but it also represents a significant share of the demolition waste related to steel buildings, as it is used in vertical partitions but, more importantly, on floor slabs above metal decking. The demolition of concrete elements produces a significant quantity of dust. All demolition works use large quantities of water that is sprayed on concrete during demolition to reduce the amount of dust. Additionally, Taisei uses an enclosed demolition environment that prevents dust from escaping the building site. Brandenburg’s study mentioned an expected water consumption of 350 liters per hour of operation. The untreated water goes into the soil/sewage system, liberally flowing down through the building. During cold months, water is added with an environmentally friendly additive that prevents freezing.

One of the advantages associated with steel construction is the possible reuse of steel members from a demolished building. Though this is a possibility, there are a number of reasons that this practice is not realistic for tall building construction, described below:

• Liabilities: A steel beam would need to be tested before being reused in a new building to ensure that the performance of the steel profile has not been diminished during its previous use.

• Demolition process: Steel scrap is a valuable material, with a market value of $300–$400 per ton. New steel profiles are sold for a price that ranges between $500 and $700 per ton. During demolition and transportation, the extra care (in terms of equipment and labor) that would be required to prevent any damage to the existing steel profile would bridge the cost gap between new and reused steel profiles.

• Cost: The reuse of steel profiles would increase the transportation and stocking cost of profiles, thus negatively impacting the economic convenience of reusing structural elements.

8.3 Energy Use in Demolition

Most of the energy consumed during the deconstruction of tall buildings is from the diesel fuel required to operate demolition machinery (skid steers, bobcats, etc.). Electricity is used to operate cranes, but as materials are lowered down, gravity significantly reduces energy requirements.

The demolition plan inquiry returned by Despe for this research provided a list of the equipment needed for each scenario. However, several experts speculate that fuel cost is not a major concern in the demolition sector compared to other economic aspects like disposal/recycling costs, transportation, and liabilities, which can, with marginal variations, jeopardize the financial balance of a demolition job (see Table 8.4).

Expected Duration of Demolition Works in Months (for all 60-Story Buildings Considered in this Study)

CompanyConcrete Core

+ Steel Columns

Concrete Core + Composite

Columns

Concrete Structure

Steel Diagrid

Structure

Brandenburg 50* (17) 58* (19) 51* (17) 40* (13)

Despe 36** (15) 33** (14) 32** (13) 37** (15)

Taisei 16*** 17*** 19*** 15***

*Figures based on a 10 hour shift per day, with 8 hours of actual work. In brackets: the duration based on a 24-hour active site. Brandenburg says overnight demolition is unlikely to be allowed in dense downtown areas.

**Figures based on 10 hours of operation per day. In brackets: the duration based on 24-hour active site.

***According to Taisei, its Tecorep demolition system allows a noise abetment of 23db, thus allowing overnight operations.

Table 8.3: Expected Duration of Demolition ProjectsSource: CTBUH


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As only one of the three consulted demolition companies provided estimates for diesel consumption, a benchmark value was needed in order to validate the results on the basis of the following information.

A detailed list of the diesel-powered equipment used to deconstruct the remaining 26 stories of the Deutsche Bank Building in New York was obtained (Bovis Lend Lease, 2014) and provides a rough estimation of the total energy consumed by this equipment. Engine power information was retrieved from manufacturer catalogs and associated to the average annual fuel consumption of similar-sized construction equipment calculated for the U.S. Environmental Protection Agency (EPA) (Eastern Research Group, Inc., 2010). The EPA’s report lists the average fuel consumption measured by excavators and other diesel-powered construction equipment used on-site per year. This data matches values that were found in other sources (Abolhasani, et al., 2008) (see Table 8.5).

The demolition phase of the remaining 26 floors lasted approximately 19 months and the actual surface area that was dismantled is estimated at about 82,600 m2, resulting in a maximum diesel consumption of 2.1 liters/m2, equal to 78 MJ/m2, very similar to the value provided by Despe for the all-steel scenario. Another literature value of 0.0612 MJ/kg was found (Doka, 2003) that corresponds, for a building the size of the Deutsche Bank building, to approximately 37 MJ/m2.

Consequently, a value of 70 MJ/m2 will be considered realistic for the on-site demolition of a steel building, 120 MJ/m2 will be considered for a concrete building, 115 MJ/m2 will be considered for a composite building, and 110 MJ/m2 will be considered for buildings with a concrete core and steel columns.

Description Manufacturer Model Power

Average Fuel Consumption

Liters/Year (EPA)

Approximate Fuel

Consumption per Job (Liters)

Hydraulic Excavat. Daewoo 130Lc 81kW 13,722 21,727

Hydraulic Excavat. Daewoo SK225 110kW 13,722 21,727

Hydraulic Excavat. Daewoo S55V 38kW 4,883 7,731

Hydraulic Excavat. Daewoo S75LC 39kW 4,883 7,731

Loader Daewoo Mega 400 210kW 25,044 39,653

Skid steer Caterpillar 226 45kW 6,669 10,559

Skid steer Caterpillar 226B 45kW 6,669 10,559

Skid steer Caterpillar 246 55kW 9,353 14,809

Light Tower Ingersoll Rand L6 10kW 4,408 6,980

Compressor Ingersoll Rand P185WJD 35kW - -

Dozer Komatsu D31P-18A 53kW 6,669 10,559

Wheel Loader Kobelco 550 82kW 13,722 21,727

Total Fuel Consumption if all Equipment was Continually in use (liters) 173,762

Table 8.5: Estimated Fuel Consumption During Demolition Phase of Deutsche Bank in N.Y.Source: EPA, 2009 and CTBUH

EquipmentSteel Frame

with Concrete Core

Concrete Core and Composite

Frame

All Concrete Structure

Whole Steel Structure

Caterpillar 330 or Similar (number)

2 2 2 1

Case C75 or Similar (number)

5 6 6 4

Bobcat T300 or Similar (number)

3 3 3 2

Diesel Daily Consumption

(liters)528 576 648 344

Total Diesel Consumption

(Liters based job on duration)

440,000 430,000 480,000 290,000

Diesel Consumption (L/m2)

3.1 L/m2 3,0 L/ m2 3.4 L/ m2 2,0 L/m2

Table 8.4: Expected Fuel Consumption During the Demolition Phase (for All 60-Story Buildings Considered in this Study)Source: Despe


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Steel Frame with Concrete

Core

Concrete Core and Composite

Frame

All Concrete Structure

Whole Steel Structure

Burners on Site 3 3 1 4

Job Duration [months]

17 19 17 13

Total Oxygen Consumption

[m3]4,798 5,363 1,599 4,892

Total Acetylene Consumption

[m3]1,028 1,149 343 1,048

Table 8.6: Expected Man Power and Consumption of Steelwork During the Demolition Phase (for All 60-Story Buildings Considered in this Study)Source: Brandenburg

According to the initial expectations, it should be noted that these values represent a very small fraction of a building’s initial embodied energy.

Taisei’s study mentions that electricity can be produced using a regenerative brake system on the crane that converts the kinetic energy of descending debris into electricity. Some results of the adoption of this system can be found in the literature (Kayashima, et al., 2012), but it is not possible to determine the exact amount of energy produced and fed back into the grid using this technique. However, it can be speculated that in the near future all cranes will be equipped with energy recovery systems that will annul any other source of electricity consumption for crane operations (i.e. floodlighting, axial rotation, etc). For this reason, we have assumed the on-site energy consumption of a crane’s operations to be null for the purposes of this study.

8.4 Transportation Assumptions for Debris

When working in dense urban environments, the logistics of a building

site is an important consideration. In demolition works, crane capacity is a key factor as the loads of debris, when lowered, need to be directly loaded onto trucks. This is often necessary to avoid the multiple handling of debris (unnecessary loading/unloading of materials that would negatively impact the economics of the project) and to cope with the constraints of very small sites, where there is little room to temporarily stock materials.

The demolition of the Deutsche Bank building benefited from a unique “tolerance” by New York City as a consequence of the 9/11 terrorist attacks. Nonetheless, the site area was limited and materials were temporarily stocked in the lower levels of the building. In normal conditions, on-site operations are limited and the crushing of concrete is often not allowed. Brandenburg mentions an ideal capacity of 10 tons for trucks, which match the loading capacity of the on-site crane. Buckets of debris are directly loaded onto the truck and further processed off-site.

Crushed concrete, being a low-value material, requires accurate logistics, as small variations can cause a massive

difference in terms of profitability and environmental impacts (Marinkovic’, et al., 2010). For this research, two different transportation scenarios were imagined for end-of-life concrete: a primary recycling site, located 12 km west of the demolition site, accepts crushed concrete at $2.5 per ton. A second site accepts incoming loads free of charge, but it is 65 km west of the demolition site. Basically, the decision is assumed on the basis of the contractor’s internal organization. If there are enough trucks, materials can be hauled to the furthest location, otherwise the dumping fees of the closer site are accepted and savings are realized on fuel and operator costs.

With a price of $300 per ton, end-of-life steel is a much more valuable material, and transportation costs are not really relevant (Doka, 2003). A scrap yard was identified 11 km from the demolition site.

The environmental impacts of transportation were included in the LCA models based on the number of loads needed to haul all of the demolition materials to their recycling sites. As expected, on-site energy consumption is relatively small compared to other factors, including the environmental emissions that occur during the demolition of a building, such as the transportation of debris and recycling of materials (Martínez, et al., 2013).

Determining the environmental consequences of steel cutting is not a straightforward process. An oxygen/acetylene torch used for cutting thick steel profiles consumes an average of 1,400 liters of oxygen and 300 liters of acetylene per hour. No data was available for the demolition of the Deutsche Bank building. Fortunately, the number of required burners on-site was provided by the demolition companies that supported the present study. Brandenburg estimated the


Figure 8.4: Gash Area of the Deutsche Bank Building, 1974, New York CitySource: William Moore

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number of staff required. If an actual cutting time equal to 10% of the hours worked is considered, total fuel consumption can be estimated (see Table 8.6).

8.5 Sources of Data on Tall Building Demolition

The present research deals with scenarios for 246- and 490-meter-tall buildings. No published data on the demolition of tall buildings was found to describe the process, equipment used, and energy consumption required for the demolition of buildings at such magnitudes.

The goal and scope of this research is the definition of a comprehensive LCA for tall building structures. Other studies, which have been extensively covered in Section 7.0 describe the energy requirements and environmental impacts connected with the construction of tall buildings. But in order to have a comprehensive analysis, system boundaries have to be extended to include the end-of-life scenario. Even if demolitions are a very rare occurrence for tall buildings, it cannot be denied that every building, sooner or later, will be demolished. The demolition of buildings is a delicate task that needs to be accurately planned using the most modern techniques (Cheng & Ma, 2013); ideally, a demolition plan should be considered in the design and construction of every building. As noted previously, functional obsolescence is a driving factor in the demolition of tall buildings. The inclusion of an end-of-life scenario in new tall building development plans, especially in quickly evolving markets, can lead to significant economic and environmental savings in the long run.

The 490-meter scenario assessed in this research would become, if it were built, the fifth-tallest building in the world. Due to its height, this building would be considered “iconic,” and an end-of-

life scenario is unlikely to occur in a reasonable time frame. On the contrary, the shorter 246-meter scenario wouldn’t be out of the ordinary in many cities in North America, Asia, and the Middle East. Consequently, an end-of-life scenario for this building is more realistic, and should be thoroughly planned and carefully considered early in the development phase. Therefore, this study assesses the demolition of the 246-meter case study, although this scenario is 50% taller than the tallest building ever dismantled as well as 80% larger (in terms of floor area) than the Deutsche Bank Building in New York.

As no precedent case studies exist for the demolition of buildings of this size, original information had to be retrieved from market leaders in this very unique sector, and benchmarked against data on the Deutsche Bank Building demolition (see Figure 8.4). Comprehensive information is available on the Lower Manhattan Development Corporation website regarding the dismantling of the Deutsche Bank Building in New York (Anon., 2014).

A 12-page demolition plan inquiry was prepared and distributed to three international demolition contractors that had previous experience in tall building demolition: Depse (Italy), Brandenburg (US), and Taisei (Japan). The demolition plan included schematic drawings and material quantities acquired through the structural design inquiry previously described. The requested information included the duration of the demolition work, labor/equipment needed, mitigation procedures envisaged, expected final cost, and other important metrics. The results from the demolition companies, which were presented in this section, should not be seen as a competitive comparison to identify the most convenient offer, but rather as three possibilities to complete a job that has never been done before.

“The inclusion of an end of life scenario in new tall building development plans, especially in quickly

evolving markets, can lead to significant

economic and environmental savings

in the long run.”


95 The End-of-Life of Tall Buildings | © Council on Tall Buildings and Urban Habitat

9.0 Inventory of Materials and Research Results


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9.0 Inventory of Materials and Research Results

9.1 The Assessment of Two Environmental Impacts

As noted in Section 3.3, the scope of this study consists of the identification of the most sustainable structural system for tall and supertall buildings through a life cycle assessment. For the purposes of comparing the two alternatives, two impact categories are considered: Climate Change and Resource Depletion. Global Warming Potential (GWP) was selected as an indicator for Climate Change, and Embodied Energy (EE) was selected as an indicator for Resource Depletion. The reason for choosing these two impact categories is dictated by the initial goal of this research, which is to help designers and structural engineers in the selection of the most “sustainable” structural system for tall buildings.

Sometimes, the wide-ranging definitions for the term “sustainability” can cause confusion. Sustainability, as it is generally understood by scientists, is the

intersection between social, economic, and environmental growth. However, in daily life, the term sustainability is narrowed only to the concept of environmental sustainability, as it is the aspect that has been historically neglected. Thus, studies on environmental sustainability seek to identify the impact of human actions on the environment, in terms of natural resource depletion and changes to the environment.

Due to climatic changes that have occurred in recent years as a result of greenhouse gas emissions, many efforts in the field are focused on reversing this trend. Thus, it was an obvious choice to select Global Warming Potential (GWP) as an indicator for this research, because it provides an accurate indication of the environmental consequences, at a global scale, of the structural choices made by designers. With this knowledge in hand, the project team can take an informed approach to the structural design of a building with respect to its greenhouse gas emissions.

However, the research team agreed that this indicator alone would have oversimplified the intricate goal of identifying the most “sustainable” structural solution. As a consequence, Embodied Energy (EE) was selected as an indicator of Resource Depletion. Energy is the driving force of life on earth, and the cause of many political, military, and strategic decisions internationally. Acknowledging the importance of energy broadens the definition of “sustainability” to account for the social and economic implications of energy consumption beyond purely environmental considerations. However, energy is profoundly linked to environmental aspects too, as the use of fossil fuels and other non-renewable resources cause large emissions of CO

2

and other greenhouse gasses.

9.2 Comments on the Selected Indicators

The decision was made to research all types of energy resources (and not just non-renewable resources) due to the fact that energy is traded on a global market, and it was found that renewables play a relatively small role in the satisfaction of the world’s needs . As a consequence, the research team believes that it is counterproductive to use a renewable source (i.e., hydro-electric power) to perform a heat-intensive process (like smelting iron or powering a cement kiln) where natural gas or other fossil fuels might be more effective. The hydro-electric power saved in this case can be more efficiently used in other applications where electric power doesn’t need to be converted (or converted back) into heat, thus reducing the inefficiencies of the process.

The two main competing structural material industries (cement/concrete producers and steel producers) tend to have a different view on “sustainability.” Because the carbon emissions generated by cement are a result of the chemical reactions inherent in its production, the global warming potential of concrete suffers from a limited margin of improvement (unless cement substitutes are used) and, consequently, the cement industry tends to use embodied energy to indicate the sustainability of its products. On the contrary, the steel industry acknowledges the global warming potential of its products because emissions for steel can be reduced when a low-carbon source of energy (such as nuclear power or hydroelectricity) is used to power electric arc furnaces, thus resulting in a more “sustainable” product. The research results show that, as expected, concrete scenarios perform better from an embodied energy

“On average, steel scenarios have better

environmental performance (lower

Global Warming potential values),

while concrete scenarios have a lower

embodied energy.”

| Inventory of Materials and Research Results © Council on Tall Buildings and Urban Habitat

99

perspective, while steel scenarios generally result in lower carbon emissions.

Even in “all steel” scenarios, though, there is a significant volume of concrete in foundations and within the slab system. Similarly, in the “all concrete” building solutions there is a significant amount of steel in the form of rebar. Thus, a holistic look at all consumptive materials in any building solution must be considered with an agreement on the end boundary conditions.

9.3 Research Results

The key research results are summarized in Table 9.1 and Figures 9.1 – 9.4, which represent the Global Warming Potential and Embodied Energy results of all 16 scenarios being considered. Each scenario was modelled by two different engineering firms, which provided an inventory of materials. The 32 resulting inventories were multiplied for the two different sets of characterization factors, so as to reflect the variable environmental impacts of concrete (due to the variability of concrete design mixes). Figures 0.3–0.6 represent the entire life cycle (A1–C3) as described by EN 15978, which corresponds to the whole construction phase, from the extraction of raw materials to the installation on the building.

It should be noted that the results of the 6a and 6b scenarios, which were supposed to correspond to the “all-steel diagrid scenario,” present two very different results from one engineering firm to the other. Both firms agree that the building has an unusual shape for this structural system. Consequently, one firm decided to add a concrete core to help the external diagrid withstand the horizontal forces acting on the building. The other firm over-designed the steel diagrid to maintain the “all-steel”

idea, thus leading to the use of an unusual amount of structural steel.

9.4 Comparison with Literature Results

A small number of LCA studies on tall buildings have been found in published literature, some authored by members of this research team. In order to perform a comparison with their findings, the results of the A1–A5 phase of this research have been divided by the gross floor area of the studied scenarios (141,600 square meters and 446,250 square meters for the short and tall scenarios respectively). A comparison table with the literature sources is offered here (see Table 2.2, page 29).

Only a few prior studies consider buildings of similar heights to this research project. In some circumstances, the results of these studies evidence GWP and EE values significantly lower than those found in the literature case studies, but the following explanation can be provided to justify the discrepancies.

The 60-story case studies of the research by Foraboschi (Foraboschi et al. 2014) are quite similar to the results of this study, and the discrepancy can be justified by a different building shape (square floor plan, 1:7 aspect ratio) and the different source of the characterization factors (Hammond & Jones 2008).

Inventory of Materials and Research Results |

Short Description

Scenario Number

GWP [kg CO

2 Eq./m2]

EE [GJ/m2]

Building Height[story]

Normal Steel + Concrete Core 1a 222 2.4 60

High Strength + Concrete Core 1b 219 2.4 60

Concrete Core and Composite Frame 1c 216 2.3 60

All Concrete Wide and Shallow Beams 2a 241 2.2 60

All Concrete Narrow and Deep Beams 2b 209 2.0 60

All Steel Diagrid Normal Steel 3a 243 3.0 60

All Steel Diagrid HS Steel 3b 226 2.7 60

Composite Diagrid 3c 228 2.6 60

Normal Steel + Concrete Core 4a 361 4.1 120

High Strength + Concrete Core 4b 357 4.0 120

Concrete Core and Composite Frame 4c 308 3.3 120

All Concrete Wide and Shallow Beams 5a 300 2.8 120

All Concrete Carrow and Deep Beams 5b 277 2.6 120

All Steel Diagrid Normal Steel 6a 431 5.2 120

All Steel Diagrid HS Steel 6b 423 5.1 120

Composite Diagrid 6c 292 3.3 120

Table 9.1: Results of Research (Summary)Source: CTBUH


100

GW

P [t

CO

2 Eq

.]

1a 1a 1b 1b 1c 1c 2a 2a 2b 2b 3a 3a 3b 3b 3c 3c

35.000

30.000

25.000

20.000

15.000

10.000

5.000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core

High Strength + Concrete

Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams

All Steel Diagrid Normal

Steel


Steel

All Steel Diagrid HS

Steel


Steel

Composite Diagrid

Composite Diagrid

60-story Equivalent Scenario - GWP (A1-C3)

22,057

24,657

19,194

20,800

21,902

24,501

18,831

20,437

21,564

24,323

18,766

20,441

21,592

27,294

27,298

32,116

18,988

23,816

23,147

28,528

23,542

24,679

21,812

22,949

21,399

22,536

21,115

22,252

22,751

24,160

19,453

21,295

French Ready Mix Association A1-C3 GWP [t CO2Eq.]

US EPDs A1-C3 GWP [t CO2Eq.]

102%105%

118%

100%

EE [G

J]


350,000

300,000

250,000

200,000

150,000

100,000

50,000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

60-story Equivalent Scenario - EE (A1-C3)

244,424

263,987

216,702

231,539

242,404

261,966

211,972

226,809

235,764

256,308

209,916

225,305

207,121

251,875

279,177

321,772

185,091

221,318

238,914

276,970

289,123

300,208

266,519

277,604

261,258

272,343

257,472

268,557

270,043

283,307

225,903

240,998

French Ready Mix Association A1-C3 EE [GJ]

US EPDs A1-C3 EE [GJ]

108%

116%

100% 105%

Figure 9.1: Life Cycle Assessment (Phases A1-C3: Raw Materials Extraction to Waste Processing) of the 60-Story Scenarios, Global Warming Potential Source: CTBUH

Figure 9.2: Life Cycle Assessment (Phases A1-C3: Raw Materials Extraction to Waste Processing) of the 60-Story Scenarios, Embodied EnergySource: CTBUH


101

GW

P [t

CO

2 Eq

.]


160,000

140,000

120,000

100,000

80,000

60,000

40,000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

120-story Equivalent Scenario - GWP (A1-C3)

108,010

119,482

109,405

125,225

108,010

119,482

105,912

121,731

90,417

103,182

97,642

116,491

87,190

107,845

101,714

125,841

79,525

97,610

95,435

116,991

130,250

133,592

125,222

144,832

126,519

129,860

125,222

144,832

86,208

95,780

90,375

101,294

French Ready Mix Association A1-C3 GWP [t CO2Eq.]

US EPDs A1-C3 GWP [t CO2Eq.]

105%100%

108%118%

EE [G

J]


1,800,000

1,600,000

1,400,000

1,200,000

1,000,000

800,000

600,000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

120-story Equivalent Scenario - EE (A1-C3)

1,219,233

1,296,106

1,227,723

1,321,045

1,219,233

1,296,106

1,182,238

1,275,560

961,564

1,046,546

1,039,256

1,147,458

847,854

1,001,407

988,060

1,160,026

782,172

910,662

940,617

1,087,520

1,637,140

1,669,722

1,393,478

1,505,531

1,588,556

1,621,137

1,393,478

1,505,531

965,166

1,032,224

1,017,568

1,089,156

French Ready Mix Association A1-C3 EE [GJ]

US EPDs A1-C3 EE [GJ]

106%100%

123%

Figure 9.3: Life Cycle Assessment (Phases A1-C3: Raw Materials Extraction to Waste Processing) of the 120-Story Scenarios, Global Warming PotentialFor Scenarios 6a and 6b Please See Disclaimer in Section “Results” of the Executive SummarySource: CTBUH

Figure 9.4: Life Cycle Assessment (Phases A1-C3: Raw Materials Extraction to Waste Processing) of the 120-Story Scenarios, Embodied EnergyFor Scenarios 6a and 6b Please See Disclaimer in Section “Results” of the Executive SummarySource: CTBUH

Inventory of Materials and Research Results | © Council on Tall Buildings and Urban Habitat

102

is one and a half times higher than the 60-story diagrid considered in this research, but the building has a very iconic shape (30 St. Mary Axe, London) that might justify the discrepancy. Moreover, the study from Oldfield also includes the foundation quantities. The paper from Trabucco (Trabucco 2011) on the same building has a remarkably different result from this research (with a much higher difference ratio from the results obtained by Oldfield), but an input-output method was used to obtain the characterization factors.

The above mentioned discrepancies attest to the critical issues related to the LCA methodology and the variability of the results mentioned in the first and second point of the general conclusion.

9.5 General Research Conclusions

A summary of the research results can be found in the following section, where the main information on each studied building scenario is presented.

Some general outcomes are presented below, which highlight the overall findings of the research:

1 – After reviewing the results of the LCA analysis within the system boundaries of EN 15978 (thus without considering the credit for scrap), the conclusions cannot be generalized for the 60- and 120-story buildings and a clear “winner” cannot be identified in terms of an ideal structural material. On average, steel scenarios have better environmental performance (lower Global Warming potential values), while concrete scenarios have a lower embodied energy. This is especially true in the scenario variations that use the concrete environmental values for US cement production, which are higher than those of French production.

The 52-story building considered by Treloar (Treloar et al. 2001) uses characterization factors derived from a fundamentally diverse methodology (input-output). Also, the structural elements of this building represent a remarkable ratio with the total embodied energy of the building, suggesting an underestimation of the other building components (curtain wall, interior finishes, MEP, etc.).

The concrete frame of a shorter 40-story building considered by Trabucco (Trabucco 2012) has an EE value that is twice the figures resulting from this research, but the case study considered in that paper (Palazzo Lombardia in Milan) has a very peculiar shape. Additionally, a hybrid analysis (consisting of a different methodology) was used to extract the characterization factors of the building materials, thus the characterization factors for each material may vary significantly.

The GWP of the 40-story steel diagrid considered by Oldfied (Oldfield 2012)

“…horizontal components of

structural frames, rather than

vertical ones, are responsible for

the greatest share of environmental

emissions.”

As explained in Section 5.1, cement not only produces CO

2 as a consequence

of the energy consumed during the production process, but also from the chemical reactions that transform limestone into clinker. Consequently, even if the production of cement is not very energy-intensive, its associated CO

2

emissions are relevant. On the contrary, all of the CO

2 emitted during the production

of steel is a consequence of the energy needed for the production process. Thus, even in the hypothetical case that both materials are produced from a carbon-free source (i.e., nuclear or hydro-power), cement will always have a minimum value of CO

2 emissions determined by the

formula CaCO3 + Heat = CaO + CO

2.

It is important to note that for the 60-story scenario, all-concrete solutions perform worse (on average) than the other scenarios in terms of GWP, while all-steel scenarios are those with the highest EE.

For the 120-story scenario, the discrepancies between the solutions are smaller, with the composite diagrid representing the best solution from a GWP standpoint, while all-concrete scenarios have the lowest average EE.

2 – Steel is a recyclable material. At the end of its life cycle, steel can be melted to produce new steel products, whose mechanical properties are identical to those of the previous product. On the contrary, the post-consumer life of concrete involves significant “downcycling.” Recycled concrete cannot be used for structural purposes and the most common use of recycled concrete is as ballast material for road and railway construction, with a significant loss of value from its previous life (see Table 9.2).

Consequently, each tall building scenario can benefit from the recyclability of the


103

Characterization Factor Source French Concrete ValuesEnvironmentally Optimized

Scenario

LCA PhaseEntire Life Cycle (Modules A1-C3)

Entire Life Cycle (Modules A1-C3)

Short Description

Scenario Number

(SF = Structural Firm)

GWP [t CO

2 Eq.]

EE[GJ]

GWP [t CO

2 Eq.]

EE [GJ]


1a_SF 01 22,057 244,424 -30% -20%

1a_SF 02 19,194 216,702 -32% -20%


1b_SF 01 21,902 242,404 -30% -20%

1b_SF 02 18,831 211,972 -30% -20%


1c_SF 01 21.564 235,764 -28% -19%

1c_SF 02 18,766 209,916 -30% -19%


2a_SF 01 21,592 207,121 -13% -13%

2a_SF 02 27,298 279,177 -23% -21%

All Concrete Narrow and Deep Beams

2b_SF 01 18,988 185,091 -15% -15%

2b_SF 01 23,147 238,914 -23% -21%


3a_SF 01 23,542 289,123 -44% -25%

3a_SF 02 21,812 266,519 -43% -25%


3b_SF 01 21,399 261,258 -43% -24%

3b_SF 02 21,115 257,472 -43% -24%

Composite Diagrid 3c_SF 01 22,751 270,043 -38% -23%

3c_SF 02 19,453 225,903 -34% -21%


4a_SF 01 108,010 1,219,233 -35% -22%

4a_SF 02 109,405 1,227,723 -34% -23%


4b_SF 01 108,010 1,219,233 -35% -22%

4b_SF 02 105,912 1,182,238 -33% -22%


4c_SF 01 90,417 961,564 -27% -19%

4c_SF 02 97,642 1,039,256 -27% -19%


5a_SF 01 87,190 847,854 -16% -16%

5a_SF 02 101,714 988,060 -17% -16%

All Concrete, Narrow and Deep

Beams

5b_SF 01 79,525 782,172 -18% -17%

5b_SF 02 95,435 940,617 -18% -18%


6a_SF 01 130,250 1,637,140 -50% -28%

6a_SF 02 125,222 1,393,478 -32% -22%


6b_SF 01 126,519 1,588,556 -49% -28%

6b_SF 02 125,222 1,393,478 -32% -22%

Composite Diagrid 6c_SF 01 86,208 965,166 -33% -22%

6c_SF 02 90,375 1,017,568 -34% -22%

Table 9.2: Results of the A1-C3 phases (raw materials extraction to waste processing) of the research and comparison with the gains of the “environmentally optimized scenario” solution.Source: CTBUH

steel at the end of the building life cycle along varying magnitudes: concrete scenarios benefit from the recyclability of rebar (see Section 4.5), while steel buildings benefit from the recycling potential of a greater amount of steel, since the material represents a larger percentage of the total weight than in concrete scenarios. It means that a “credit” can be obtained for the steel parts forming the structure of a building. These include steel sections, rebar, steel decks, and so on. Some of the scenarios considered by this research produce such a high quantity of steel scrap that this “credit” is capable of offsetting the environmental “burden” caused by directing the remaining demolition waste (mainly concrete) to a landfill.

However, European Norm 15978, which has been used as a reference in this study, prescribes that the system boundaries of a building LCA must be limited to the disposal of the demolition debris. However, it cannot be denied that most materials have a residual value even after the demolition of the building.

In fact, it is not possible to “subtract” the credit from scrap from the environmental values of the other building phases (see Section 4.10). This is a highly disputed point of debate in the LCA community; several researchers are convinced that the credit from scrap should be included in the system boundaries of an LCA, as the recycling potential of materials should be considered in an environmental analysis to promote the use of recyclable materials. The steel industry is not the only industrial party pushing in this direction, as paper and plastic industries would also benefit from this option. On the other hand, those who believe that this information would be misleading if accounted for in an LCA also have solid arguments. Non-recyclable materials such as concrete and wood


104

EE [G

J]


350,000

300,000

250,000

200,000

150,000

100,000

50,000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

60-story Equivalent Scenario - EE (A1-D - Beyond the System Boundary in EN 15978)

222,333

241,895

194,410

209,247

220,560

240,122

190,259

205,096

216,166

236,710

189,407

204,796

219,514

264,269

277,858

320,453

193,378

229,606

237,396

275,452

251,446

262,531

231,712

242,797

227,043

238,128

223,821

234,906

239,358

252,621

200,848

215,943

French Ready Mix Association A1-D EE [GJ]

US EPDs A1-D EE [GJ]

106%111%

118%

101%

GW

P [t

CO

2 Eq

.]


35.000

30.000

25.000

20.000

15.000

10.000

5.000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

60-story Equivalent Scenario - GWP (A1-D - Beyond the System Boundary in EN) 15978)

19,021

21,621

16,237

17,843

18,894

21,493

15,939

17,545

18,772

21,531

15,984

17,659

21,868

27,570

26,015

30,833

18,996

23,824

22,031

27,413

19,025

20,162

17,619

18,756

17,272

18,409

17,052

18,188

18,901

20,310

16,230

18,072

French Ready Mix Association A1-D GWP [t CO2Eq.]

US EPDs A1-D GWP [t CO2Eq.]

100%100%

134%

101%

Figure 9.5: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the 60-Story Scenarios, Global Warming PotentialSource: CTBUH

Figure 9.6: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling ( (Additional Information Beyond the System Boundaries, According to EN 15978) for the 60-Story Scenarios, Embodied EnergySource: CTBUH


105

GW

P [t

CO

2 Eq

.]


140,000

120,000

100,000

80,000

60,000

40,000

20,000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

120-story Equivalent Scenario - GWP (A1-D - Beyond the System Boundary in EN 15978)

94,033

105,505

95,260

111,079

94,033

105,505

92,394

108,213

81,009

93,774

87,504

106,353

86,286

106,942

100,346

124,472

77,836

95,921

92,871

114,426

105,907

109,248

110,906

130,516

102,845

106,187

110,906

130,516

74,126

83,698

78,319

89,238

French Ready Mix Association A1-D GWP [t CO2Eq.]

US EPDs A1-D GWP [t CO2Eq.]

120% 123%

100%

EE [G

J]


1,600,000

1,400,000

1,200,000

1,000,000

800,000

600,000

400,000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

120-story Equivalent Scenario - EE (A1-D Beyond the System Boundary in EN 15978)

1,115,316

1,192,189

1,123,142

1,216,464

1,115,316

1,192,189

1,083,224

1,176,546

900,964

985,945

973,652

1,081,854

875,454

1,029,007

1,016,402

1,188,368

797,704

926,194

953,253

1,100,156

1,428,242

1,460,823

1,291,760

1,403,813

1,385,602

1,418,184

1,291,760

1,403,813

874,949

942,007

927,962

999,550

French Ready Mix Association A1-D EE [GJ]

US EPDs A1-D EE [GJ]

117%

105% 100%

Figure 9.7: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the 120-Story Scenarios, Global Warming Potential (For Scenarios 6a and 6b, See Disclaimer in Section 9.3)Source: CTBUH

Figure 9.8: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the 120-Story Scenarios, Embodied Energy (For Scenarios 6a and 6b, See Disclaimer in Section 9.3)Source: CTBUH


106

do not receive any “benefit” in this case, but are given equal consideration as the recyclable ones, as no one benefits from its recycling potentialities . As a consequence, according to EN 15978, Module D (the part of an LCA that deals with the recyclability of materials) is considered important additional information for the environmental accounting of various options (ATHENA 2002).

In this research, both approaches have been used: results are presented both by including and excluding the recycling potential of steel. If the credit for scrap is considered, the results change significantly. For the 60-story scenario, concrete solutions are those with the highest GWP and EE of all combinations, with mixed solutions (i.e., concrete core and steel or composite frame) resulting in the lowest environmental impacts. Composite diagrid, on the other hand, represents the best solution for the 120-story building scenarios (see Figure 9.5-9.8).

The high recycling potential is an intrinsic value of steel and metals in general, and this “credit” should be communicated as part of the additional information necessary to make an informed decision on the environmental properties of the various design solutions assessed by this research (ATHENA 2002) (WorldSteel Association 2011) (American Iron and Steel Institute 2013). The impact of Module D is evident when the credit for scrap is included as in Figures 0.8-0.11.Module D, developed and presented within this study, is a suggested approach with clearly identified impacts for further consideration and evaluation. Establishing methods to apply the credit value for steel scrap is a recommended topic of further research.

3 – The transportation of both construction materials and demolition

waste is not a very significant factor in a tall building LCA, with values typically ranging between 1–2.5% in terms of total GWP and 0.9–3.2% of total EE when only the construction phase is considered. This study accounted for the actual transportation distances of the materials that were used in the construction of the referenced case study. These impacts represent average values for a construction project of this magnitude.

Following an in-depth analysis, it was found that most of the environmental impacts associated with transportation occur during the final delivery of the materials to the construction site, and not during the previous phases of their fabrication process. In fact, the delivery of structural materials to the construction site is typically carried out by diesel-powered trucks. While the other stages of their fabrication utilize more efficient transportation means (ships, barges, trains, etc.), especially when materials need to travel long distances. This reality makes it possible to obtain structural materials with better environmental performance, even if the producers are located far away. Construction materials can be transported across greater distances without a significant impact on the overall sustainability of the building structure, especially when long-haul transportation methods employ ships, trains, and other “energy-efficient” means of transport.

4 – Tall buildings are commonly held responsible for a substantial depletion of construction materials as a consequence of the “premium for height” described by F. Khan, which is the extra structural materials that are needed to support tall structures given the increased lateral forces acting on them due to earthquakes and wind. This is not arguable, but it should be noted in the case studies examined that horizontal structures

(beams, floor slabs, etc.) represent 50–80% of the building’s weight on the shorter 60-story scenarios, and 30–60% of the building’s weight in the taller 120-story scenarios.

This indicates that horizontal components of structural frames, rather than vertical ones, are responsible for the greatest share of environmental emissions. This is independent of building height (see Tables 9.3-9.4). In fact, the horizontal structures forming the flooring system are repeated multiple times in a tall building (60 and 120 times in the considered scenarios) and their design is only marginally affected by the height of the building, as just a few of the horizontal beams come into play with the vertical structure. Consequently, the materials being used for floors are not a consequence of the building’s height but, rather, of its structural spans . Also, it is very important to note how an optimization of the horizontal structures, which are repeated many times on each floor, can significantly reduce the amount of required structural materials, and their consequent environmental emissions. These reductions can be realized if shorter structural spans are used (the studied scenarios had 13.5 meters of unobstructed lease span) or lighter flooring systems are adopted.

5 – Significant environmental benefits can be realized by choosing the best material production process, as the same material can have profoundly different environmental properties depending on its source. A special set of characterization factors was used to run “environmentally-optimized” scenarios. In this additional set of environmental data, the best environmental properties for metallic materials were used. Most of the steel products (steel profiles ASTM A913, rebar, etc.), for instance, can be purchased from


107

electric arc furnaces, which use recycled steel scrap as their predominant material input. The environmental properties of such products are extremely beneficial, and the resulting building structures designed with these materials have a GWP and EE significantly lower than the original structures designed with the average environmental values provided by WorldSteel (WorldSteel Association 2011) (Hammond & Jones 2011).

Additionally, special design mixes of concrete can be used to improve the environmental properties of structures. In fact, a significant percentage of cement in the mix can be substituted with components such as fly ash, furnace slag, or silica fume, significantly decreasing the GWP and EE of the resulting concrete. Also, the production process can use unconventional materials to substitute the conventional fossil fuels needed to produce heat in the kiln. In fact, post-consumer plastics such as used tires and other by-products can be used as a combustion material. The environmental benefits of this procedure, however, are difficult to account for in terms of their relative emissions. Scientists have not yet agreed whether the relative environmental impacts caused by the combustion of such alternative fuels should be credited to the original product, for instance a tire, or if it should be accounted for in the life cycle of the new product as a combustion material. If the former system is used, the resulting cement is virtually a zero-energy material and the only carbon releases are those associated with the chemical reaction that transforms limestone into cement. If the latter system is used, the same concrete is not an environment-friendly material due to the many pollutants that are released during the burning process of unrefined combustibles.

However, for the purposes of this research, concretes with cement substitutes have not been considered. In fact, these types of concretes have different behavioral properties than “normal” concretes, such as longer curing times, possibly increased fragility, etc. (Bentz et. al. 2013) (Fantilli & Chiaia 2012). As a result, these alternatives were not considered in this research in order to improve the comparability of the various scenarios. However, it should be noted that cement substitutes are being used in the construction of tall buildings when special characteristics are required (e.g., in hot climates, fly ash is used to reduce the heat of hydration when large quantities of concrete are poured) and they are consequently worthy of further consideration and research in terms of their environmental implications for tall building structural systems (see Figures 9.9-9.12).

9.6 Future Research

As mentioned before, the research results underline fundamental issues in the LCA methodology. Such problems are well known among LCA practitioners around the world. The most urgent issue, to increase the significance of LCA studies and extend their application, is to find solutions to the above-mentioned problems and inconsistencies. The identification of future research in this field is thus left to LCA specialists. However, there are many other research topics that can be developed and supported by the tall building industry.

A list of potential research topics stemming from the results of this LCA is presented below. The list is non-comprehensive, but it consists of the most evident aspects of the practice that need accurate and urgent research. Topics are presented in a sequence that reflects their relative position in the flow

of knowledge: from general/conceptual aspects related to the planning and design of tall buildings, to precise aspects related to the choice of construction materials and their use.

• A study to explore the real needs of tenants in terms of column-free structural spans in tall buildings. Tall buildings are often designed with the longest unobstructed spans possible to increase adaptability for final users. This brings about suboptimal design solutions that require extra structural materials on elements (floor beams) that are repeated thousands of times in a tall building. This particular typology is strongly driven by the market, and any research on the drawbacks of reducing the unobstructed lease span in tall buildings must carefully consider the market disadvantages (if any) of buildings with shorter spans.

• Similarly, a study on the optimal inter-story height would lead to significant savings in terms of structural materials; though it would contain the same available floor surface, a shorter building with optimized floor heights is subject to less forces, thus allowing a reduced quantity of structural materials for its vertical structures. Additionally, a shorter building has shorter vertical structures, thus significantly reducing the quantity of materials for structures and other building components: smaller façades, shorter ducts, etc. In order to achieve this, several strategies have to be studied and assessed. Acknowledging that tall buildings are market-driven projects, research should be carried out on the requested ceiling height by tenants. Once this is minimized without compromising the real


108

GW

P [t

CO

2 Eq

.]


35.000

30.000

25.000

20.000

15.000

10.000

5.000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

60-story Equivalent Scenario Environmental OptimizationGWP (A1-D Beyond the System Boundary in EN 15978)

15,330 12,814 15,261 12,652 15,552 12,926 20,654 23,398 17,800 19,811 12,782 11,982 11,834 11,677 13,787 12,529Environmentally Optimized A1-D GWP [t CO2Eq.]

117% 109%100%

169%

EE [G

J]


350,000

300,000

250,000

200,000

150,000

100,000

50,000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

60-story Equivalent Scenario Environmental OptimizationEE (A1-D Beyond the System Boundary in EN 15978)

200,969 175,339 199,560 172,039 197,499 172,373 206,675 250,189 180,721 213,919 215,552 199,463 196,153 193,187 210,175 179,755Environmentally Optimized A1-D EE [GJ]

100%105%

114%108%

Figure 9.9: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the “Environmentally Optimized” 60-Story Scenarios, Global Warming PotentialSource: CTBUH

Figure 9.10: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the “Environmentally Optimized” 60-Story Scenarios, Embodied EnergySource: CTBUH


109

GW

P [t

CO

2 Eq

.]


100,000

90,000

80,000

70,000

60,000

50,000

40,000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

120-story Equivalent Scenario Environmental OptimizationGWP (A1-D Beyond the System Boundary in EN 15978)

72,136 74,189 72,136 72,635 67,982 73,578 80,262 93,194 71,862 85,404 64,786 87,609 63,126 87,609 58,099 60,468Environmentally Optimized A1-D GWP [t CO2Eq.]

122%

100%

139%EE

[GJ]


1,400,000

1,200,000

1,000,000

800,000

600,000

400,000

200,000

Normal Steel +

Concrete Core

Normal Steel +

Concrete Core


Core


Core

Concrete Core+

Composite Frame

Concrete Core+

Composite Frame



All Concrete Narrow

and Deep Beams

All Concrete Narrow

and Deep Beams


Steel


Steel


Steel


Steel

Composite Diagrid

Composite Diagrid

120-story Equivalent Scenario Environmental OptimizationEE (A1-D Beyond the System Boundary in EN 15978)

978,686 986,840 978,686 955,108 818,800 882,113 811,734 940,761 734,516 874,282 1,181,396 1,142,486 1,147,501 1,142,486 775,483 819,037Environmentally Optimized A1-C3 EE [GJ]

117%

100%105%

Figure 9.11: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the “Environmentally Optimized” 120-Story Scenarios, Global Warming PotentialFor Scenarios 6a and 6b Please See Disclaimer in Section 9.3Source: CTBUH

Figure 9.12: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the “Environmentally Optimized” 120-Story Scenarios, Embodied EnergyFor Scenarios 6a and 6b Please See Disclaimer in Section 9.3Source: CTBUH


110

estate performance of the building, the inter-story height can be further optimized by reducing the space needed for the HVAC system and the height of the structural components. Research in this field would lead to significant advantages in the sustainability of tall buildings.

• Steel has an enormous advantage over concrete for the creation of modular, prefabricated elements that represent entire pieces of a building. Research should investigate these possibilities for their specific applications on tall buildings. Even if the credit for scrap cannot be considered within the building life cycle according to EN 15978, an easier assembly and dismantling of a tall building will have significant advantages, not only from an environmental perspective, but also in terms of costs, impacts on the city, and quality of construction.

• The present research suffers from a lack of knowledge on demolition procedures for tall buildings due to the limited number of such demolitions that have taken place in the past. Research on the demolition techniques for tall buildings is needed to reduce the impact of this phase across several dimensions, both for the benefit of the owner/developer (reducing the duration of demolition, its cost, and the liabilities toward other properties) and the surrounding community (in terms of noise/dust/vibrations during demolition and traffic congestion due to the removal of debris). Similarly, research is needed to design buildings that are easier to dismantle, which will ease this phase of a building’s life cycle.

• A comprehensive study on flooring systems is needed to identify solutions that use less structural materials and, consequently, release less environmental pollutants. Innovative decking systems, both for steel and concrete buildings already exist, and some of these modern systems have already been adopted in tall buildings. Research is needed to assess their benefits, from more than just an environmental standpoint.

Influ

ence

of H

oriz

onta

l & V

erti

cal S

truc

ture

s

1a1b

1c2a

2b3a

3b3c

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r.

Firm

BSt

r. Fi

rm A

Str.

Firm

BSt

r. Fi

rm A

Str.

Firm

BSt

r. Fi

rm A

Str.

Firm

BSt

r. Fi

rm A

Str.

Firm

BSt

r. Fi

rm A

Str.

Firm

B

Tota

l Hor

izon

tal

Stru

ctur

es

tons

34.4

1934

.419

34.4

1934

.419

34.4

1934

.419

83.0

5383

.053

61.1

3861

.138

34.1

6534

.165

34.1

6534

.165

34.1

6534

.165

%49

,2%

59,3

%49

,3%

59,6

%47

,1%

57,3

%64

,5%

61,9

%57

,2%

54,6

%76

,4%

78,7

%79

,6%

79,8

%61

,3%

63,8

%

Tota

l Ver

tica

l St

ruct

ures

tons

33.9

3722

.000

33.8

0621

.693

37.1

3424

.094

45.9

9251

.457

45.9

9250

.997

8.81

67.

480

7.01

06.

895

19.9

4917

.793

%48

,5%

37,9

%48

,4%

37,6

%50

,8%

40,1

%35

,7%

38,3

%43

,0%

45,6

%19

,7%

17,2

%16

,3%

16,1

%35

,8%

33,2

%

Tota

l Str

uctu

ral

Wei

ght

tons

70.0

0658

.070

69.8

7557

.763

73.1

5260

.112

128.

785

134.

250

106.

870

111.

875

44.7

2243

.386

42.9

1642

.801

55.7

1353

.558

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

4a4b

4c5a

5b6a

6b6c

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r.

Firm

BSt

r. Fi

rm A

Str.

Firm

BSt

r. Fi

rm A

Str.

Firm

BSt

r. Fi

rm A

Str.

Firm

BSt

r. Fi

rm A

Str.

Firm

BSt

r. Fi

rm A

Str.

Firm

B

Tota

l Hor

izon

tal

Stru

ctur

es

tons

101.

163

101.

163

101.

163

101.

163

101.

163

101.

163

244.

108

241.

910

179.

696

178.

578

100.

417

100.

417

100.

417

100.

417

100.

417

100.

417

%33

,2%

32,2

%33

,2%

32,5

%31

,6%

29,6

%52

,4%

45,6

%44

,8%

38,2

%55

,0%

26,8

%55

,9%

26,8

%39

,8%

38,5

%

Tota

l Ver

tica

l St

ruct

ures

tons

198.

243

208.

248

198.

944

205.

299

214.

323

235.

387

222.

460

289.

194

222.

460

289.

194

76.9

5026

8.62

973

.800

268.

629

147.

286

155.

994

%65

,0%

66,3

%65

,2%

65,9

%66

,9%

69,0

%47

,8%

54,5

%55

,4%

61,9

%42

,1%

71,8

%41

,1%

71,8

%58

,4%

59,7

%

Tota

l Str

uctu

ral

Wei

ght

tons

304.

952

314.

256

304.

952

311.

307

320.

189

341.

253

465.

805

530.

341

401.

392

467.

008

182.

652

374.

213

179.

502

374.

213

252.

406

261.

114

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

| Inventory of Materials and Research Results

Table 9.3 Influence of Horizontal & Vertical StructuresSource: CTBUH


111

• Despite the fact that the reuse of steel elements at the end of a building’s life is more of an academic idea rather than a true possibility, buildings can be designed to maximize the ability to sort, reuse, and recycle materials at the end of their life cycles. From this perspective, composite columns seem to be a nonoptimal solution due to the strong connections that exist between large steel profiles, steel rebar, and studs, which make it very difficult and labor-intensive to separate these materials at the end of their lives.

• A study on the measurable influences (in terms of mechanical properties, cost, environmental benefits, etc.) of cement substitutes in the concrete mixes required for the construction of tall buildings would be beneficial. The research should not only assess the mechanical properties of the new concrete designs, but also the other parameters that influence the construction process: curing time, hydration heat release, fragility, and the ease at which it could be pumped at height.

• Fireproofing is an essential component of steel construction. Due to the numerous fireproofing strategies that exist, research should be carried out to improve the environmental properties of fireproofing materials, especially with regards to their embodied energy and the ability to detach them from the steel structures after a building is dismantled. Currently, safety mandates call for a very strong bond between fireproofing materials and steel elements, making it very difficult to salvage the steel for recycling. Also, efforts should be taken to educate fireproofing companies on sustainability. The fireproofing contacts established during this LCA research showed little knowledge of LCA, embodied energy, and other assessment protocols of sustainability.

Influ

ence

of t

he

Slab

s

1a1b

1c2a

2b3a

3b3c

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Con

cret

e 30

-37

tons

28.4

2428

.424

28.4

2428

.424

28.4

2428

.424

80.8

0380

.803

58.9

3958

.939

28.4

2428

.424

28.4

2428

.424

28.4

2428

.424

%40

,6%

48,9

%40

,7%

49,2

%38

,9%

47,3

%62

,7%

60,2

%55

,1%

52,7

%63

,6%

65,5

%66

,2%

66,4

%51

,0%

53,1

%

Tota

l C

oncr

ete

tons

59.3

0148

.068

59.3

0113

1.61

163

.517

50.9

4312

5.19

312

6.50

910

3.32

910

5.30

728

.424

28.4

2428

.424

28.4

2442

.040

42.9

37

%84

,7%

82,8

%84

,9%

227,

8%86

,8%

84,7

%97

,2%

94,2

%96

,7%

94,1

%63

,6%

65,5

%66

,2%

66,4

%75

,5%

80,2

%

Tota

l Str

uctu

ral

Wei

ght

tons

70.0

0658

.070

69.8

7557

.763

73.1

5260

.112

128.

785

134.

250

106.

870

111.

875

44.7

2243

.386

42.9

1642

.801

55.7

1353

.558

%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%

4a4b

4c5a

5b6a

6b6c

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Str.

Firm

ASt

r. Fi

rm B

Con

cret

e 30

-37

tons

83.5

4383

.543

83.5

4383

.543

83.5

4383

.543

237.

496

237.

496

173.

232

173.

232

83.5

4383

.543

83.5

4383

.543

83.5

4383

.543

%27

,4%

26,6

%27

,4%

26,8

%26

,1%

24,5

%51

,0%

44,8

%43

,2%

37,1

%45

,7%

22,3

%46

,5%

22,3

%33

,1%

32,0

%

Tota

l C

oncr

ete

tons

247.

857

258.

225

178.

417

258.

225

283.

029

301.

453

447.

977

509.

178

383.

714

444.

915

83.5

4331

3.00

483

.543

313.

004

208.

779

213.

652

%81

,3%

82,2

%58

,5%

82,9

%88

,4%

88,3

%96

,2%

96,0

%95

,6%

95,3

%45

,7%

83,6

%46

,5%

83,6

%82

,7%

81,8

%

Tota

l Str

uctu

ral

Wei

ght

tons

304.

952

314.

256

304.

952

311.

307

320.

189

341.

253

465.

805

530.

341

401.

392

467.

008

182.

652

374.

213

179.

502

374.

213

252.

406

261.

114

%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%10

0,0%

100,

0%

Inventory of Materials and Research Results |

Table 9.4 Slabs IncidenceSource: CTBUH


10.0 Appendix


114

Scenario 1a 60-Story Building – Concrete Core with Normal Steel Frame Scenario

Geometric Properties

Scenarios 1a

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 2

Mec. Floors Height [m] 8

Office Floors 56

Floor-to-Floor Height [m] 4

Total Floor Number 59

Height [m] 246

Layout

Width [m] 60

Length [m] 40

Lower Core Width [m] 35

Lower Core Length [m] 13

Lower Core Floors [story] 40

Upper Core Width [m] 16.5

Upper Core Length [m] 13

Upper Core Floors [story] 19

Gross Total Floor Area [m2] 141,600

Lower Net Area [m2] 77,800

Upper Net Area [m2] 41,525

Total Net Area [m2] 119,325

Built Floor Area [m2] 126,750

Columns

Number of Lower Columns 16

Number of Upper Columns 20

Number of Diagrid Columns

Total Length of Columns 4,240

Table 10.1.1a: Geometric properties for Scenarios 1aSource: CTBUH

Scenario 1a Description• The structure is composed of a reinforced concrete core and standard structural

steel profiles (i.e. wide flange I-shapes). • The steel used for all structural elements is normal 50 ksi (345 MPa) steel• Steel beams at 3 m off-center, spanning core to exterior.

Perimeter edge beams are for gravity framing only (not lateral).• Beams are made of standard structural steel profiles.• Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal

deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.

| Appendix © Council on Tall Buildings and Urban Habitat

115

Scenario 1a Structural Firm 01

LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 21,027 221,299 23,627 240,861

Cradle to Site 21,633 232,223 24,233 251,785

Cradle to Grave 22,057 244,424 24,657 263,987

Cradle to Cradle (including recycling potential)

19,021 222,333 21,621 241,895

Table 10.3.1a: Results for Scenario 1a Structural Firm 01Source: CTBUH


LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 18,252 195,363 19,858 210,200

Cradle to Site 18,835 205,637 20,440 220,474

Cradle to Grave 19,194 216,702 20,800 231,539


16,237 194,410 17,843 209,247


Quantities of Materials

Material PropertyStructural

Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 11,944 -

9 ksi Concrete 0 0

8 ksi Concrete 12,857 7,608


4-5 ksi Concrete 28,424 28,424

Steel

Steel Rebar 1,388 957

WWF 260 260

Steel Studs 25 25

Metal Decking 1,212 1,212

Steel Beams 4,011 3,949

Steel Columns 1,971 1,614

Steel Trusses 186 333

Other Fireproofing Spray 825 825

Total Above Grade Structural Weight 70,006 58,070

Scrap

Scrap Input 6,357 5,827

Total Scrap not Landfilled 8,898 8,218

Net Scrap 2,541 2,391

Table 10.2.1a: Inventory of Materials for Scenarios 1aSource: CTBUH

Appendix | © Council on Tall Buildings and Urban Habitat

116

Scenario 1a: 60-Story Building – Concrete Core with Normal Steel Frame Scenario Structural Firm 01Graphical Representation of the Research Result

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput

Transportation and on-site Construction

Production ofmaterials

not relevant

US EPDs Values

French Concrete Values

US EPDs Values


during the use phase

not relevantduring the use phase

scrap recycling

starting point of future life of the materials


Construction

9.59

9

demolition

PREVIOUSLIFE OFMATERIALS

GlobalWarming Potential[tons CO2eq]

Life Phase

LIFE CYCLE SYSTEM BOUNDARY(ACCORDING TO EN 15978)

scenario 1a

BENEFITS AND LOADSBEYOND THE BUILDING

LIFE CYCLE(ACCORDING TO EN 15978)

Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

232.

223

betie

251.

785

epds

232.

223

betie

251.

785

epds

221.

229

betie

240.

861

epds

244.

424

betie

263.

987

epds

241.

895

epds

222.

333

betie

85.1

84

21.6

33 b

etie

22.0

57 b

etie

19.0

21 b

etie

24.2

33 ep

ds

21.6

63 b

etie

24.2

33 ep

ds

21.0

27 b

etie

23.6

27 ep

ds

24.6

57 ep

ds

21.6

21 ep

ds

Benefits of Using

Recycled Inputs

Production Process

Transportation and On-site Operations

Incidence on Use Phase

DemolitionCredits

for Scrap

Embodied Energy [GJ]

US EPDs-85,184

326,04510,924 N.A. 12,202 22,091

French EPDs 306,482

Global Warming Potential [tCO

2Eq.]

US EPDs

-9,599

33,226

606 N.A. 424 3,036French EPDs 30,626


117

Scenario 1a: 60-Story Building – Concrete Core with Normal Steel Frame Scenario Structural Firm 02Graphical Representation of the Research Result

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

demolition



Life Phase


scenario 1a



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

structural �rm 02

195.

363

betie

210.

200

epds

205.

637

betie

220.

474

epds

205.

637

betie

220.

474

epds

216.

702

betie

231.

539

epds

209.

247

epds

194.

410

betie

78.0

828.

799

18.2

52be

tie19

.858

epds

18.8

35be

tie20

.440

epds

18.8

35be

tie20

.440

epds

19.1

94be

tie20

.800

epds

16.2

37be

tie17

.843

epds

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-72,404

288,28210,275 N.A. 11,065 22,292

French EPDs 273,445


2Eq.]

US EPDs

-8,799

28,657

582 N.A. 360 2,958French EPDs 27,051


118

Scenario 1b 60-Story Building – Concrete Core with High-Strength Steel Frame Scenario


Scenarios 1b

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 2

Mec Floors Height [m] 8

Office Floors 56



Height [m] 246

Layout

Width [m] 60

Length [m] 40



Lower Core Floors [m] 40



Upper Core Floors [m] 19






Columns



Number of Diagrid Columns


Table 10.1.1b: Geometric Properties for Scenario 1bSource: CTBUH

Scenario 1b Description• The structure is composed of a reinforced concrete core and standard structural

steel profiles (i.e., wide flange I-shapes). • The steel used for the columns is 65 ksi (F450 MPa) high strength steel, while all

other structural elements use normal 50 ksi (345 MPa) steel.• Steel beams at 3 m off-center, spanning core to exterior.

Perimeter edge beams are for gravity framing only (not lateral).• Beams are made of standard structural steel profiles.• Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal

deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.


119



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 11,944 0

9 ksi Concrete 0 0



4-5 ksi Concrete 28,424 28,424

Steel

Steel Rebar 1,388 957

WWF 260 260

Steel Studs 25 25







Scrap



Net Scrap 2,522 2,348

Table 10.2.1b: Inventory of Materials for Scenario 1bSource: CTBUH

Scenario 1b Structural Firm 01

LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 20,873 219,294 23,473 238,856

Cradle to Site 21,478 230,205 24,078 249,767

Cradle to Grave 21,902 242,404 24,501 261,966


18,894 220,560 21,493 240,122

Table 10.3.1b: Results for Scenario 1b Structural Firm 01Source: CTBUH


LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 17,892 190,669 19,498 205,506

Cradle to Site 18,472 200,914 20,078 215,751

Cradle to Grave 18,831 211,972 20,437 226,809


15,939 190,259 17,545 205,096



120

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

demolition



Life Phase


scenario 1b



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

261.

966

epds

240.

122

epds

83.6

93

242.

404

betie

220.

560

betie

219.

294

betie

238.

856

epds

230.

205

betie

249.

767

epds

230.

205

betie

249.

767

epds

-9.4

3120

.873

betie

23.4

73 ep

ds

21.4

78be

tie24

.078

epds

21.4

78be

tie24

.078

epds

21.9

02be

tie24

.501

epds

18.8

94be

tie21

.493

epds

Scenario 1b: 60-Story Building – Concrete Core with High Strength Steel Frame Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-83,693

322,55010,911 N.A. 12,199 21,844

French EPDs 302,987


2Eq.]

US EPDs

-13,562

32,904

605 N.A. 423 3,008French EPDs 30,304


121

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

demolition



Life Phase


scenario 1b



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

structural �rm 02

226.

809

epds

205.

096

epds

74.5

93

211.

972

betie

190.

259

betie

190.

669

betie

205.

506

epds

200.

914

betie

215.

751

epds

200.

914

betie

215.

751

epds

8.40

617

.892

betie

19.4

98 ep

ds

18.4

72be

tie20

.078

epds

18.4

72be

tie20

.078

epds

18.8

31be

tie20

.437

epds

15.9

39be

tie17

.545

epds

Scenario 1b: 60-Story Building – Concrete Core with High Strength Steel Frame Scenario Structural Firm 02Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-74,593

280,10010,245 N.A. 11,058 21,713

French EPDs 265,263


2Eq.]

US EPDs

-8,406

27,904

580 N.A. 359 2,892French EPDs 26,298


122

Scenario 1c60-Story Building – Concrete Core and Composite Frame Scenario


Scenarios 1c

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 2


Office Floors 56



Height [m] 246

Layout

Width [m] 60

Length [m] 40












Columns



Number of Diagrid Columns 0


Table 10.1.1c: Geometric Properties for Scenario 1cSource: CTBUH

Scenario 1c Description• The structure is composed of a concrete core and by composite steel/concrete

columns on the perimeter. • The columns use standard structural steel sections with 50 ksi (345 MPa) strength

as their core, covered with high strength 8-10 ksi (60-70 MPa) reinforced concrete.• Steel beams at 3 m off-center, spanning core to exterior.

Perimeter edge beams are for gravity framing only (not lateral).• Beams are made of standard structural steel profiles.• Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system

metal deck with shear studs. Metal deck, beams and columns will include spray-applied fireproofing.


123



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete


9 ksi Concrete 0 0



4-5 ksi Concrete 28,424 28,424

Steel

Steel Rebar 1,554 1,122

WWF 260 260

Steel Studs 25 25



Steel Columns 786 667




Scrap

Scrap input 5,467 5,138


Net Scrap 2,415 2,299

Table 10.2.1c: Inventory of Materials for Scenarios 1cSource: CTBUH

Scenario 1c Structural Firm 01

LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 20,499 210,807 23,258 231,352

Cradle to Site 21,104 221,851 23,863 242,395

Cradle to Grave 21,564 235,764 24,323 256,308


18,772 216,166 21,531 236,710

Table 10.3.1c: Results for Scenario 1c Structural Firm 01Source: CTBUH


LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 17.794 186.903 19,469 202,292

Cradle to Site 18.376 197.268 20.051 212.657

Cradle to Grave 18.766 209.916 20.441 225.305


15.984 189.407 17.659 204.796



124

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

demolition



Life Phase


scenario 1c



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

256.

308

epds

236.

710

epds

73.2

56

235.

764

betie

216.

166

betie

210.

807

betie

231.

352

epds

221.

851

betie

242.

395

epds

221.

851

betie

242.

395

epds

8.25

520

.499

betie

23.2

58ep

ds

21.1

04be

tie23

.863

epds

21.1

04be

tie23

.863

epds

21.5

64be

tie24

.323

epds

18.7

72be

tie21

.531

epds

Scenario 1c: 60-Story Building – Concrete Core and Composite Frame Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-73,256

304,60711,044 N.A. 13,913 19,598

French EPDs 284,063


2Eq.]

US EPDs

-8,255

31,513

605 N.A. 460 2,792French EPDs 28,754


125

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

demolition



Life Phase


scenario 1c



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

7.75

917

.794

betie

19.4

69ep

ds

18.3

76be

tie20

.051

epds

18.3

76be

tie20

.051

epds

18.7

66be

tie20

.441

epds

15.9

84be

tie17

.659

epds

225.

305

epds

204.

796

epds

68.8

54

209.

916

betie

189.

407

betie

186.

903

betie

202.

292

epds

197.

268

betie

212.

657

epds

197.

268

betie

212.

657

epds


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-68,854

271,14610,365 N.A. 12,648 20,509

French EPDs 255,757


2Eq.]

US EPDs

-7,759

27,228

582 N.A. 389 2,782French EPDs 25,553


126

Scenario 2a60-Story Building – All Concrete with Wide and Shallow Beams Scenario


Scenarios 2a

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 2


Office Floors 56



Height [m] 246

Layout

Width [m] 60

Length [m] 40












Columns





Table 10.1.2a: Geometric Properties for Scenarios 2aSource: CTBUH

Scenario 2a Description• The structure is composed of a concrete core and by concrete columns on

the perimeter. The floor system is composed by a concrete slab with wide and shallow concrete beams.

• Multiple grades of concrete from 4 ksi (30 MPa) to 10 ksi (70 MPa) are used for different structural components. The lightweight 4-5 ksi is used for floors, while the higher grades (6 ksi and up) are used for the lateral elements. All reinforcements are also made of normal 50 ksi (340 MPa) steel.

• 220 mm rebar slab with PT/rebar band beams 2000 mm wide and 450 mm deep at 9 m off-center are used to match column lines.

• Beams and floors are made of 4-5 ksi (30-37 MPa) with normal 50 ksi steel. • Disposable wooden formwork is considered beneath all the floors and beams .


127



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 24,150 5,962

9 ksi Concrete 0 0

8 ksi Concrete 13,340 31,464


4-5 ksi Concrete 80,803 80,803

Steel


WWF 260 260

Steel Studs 0 0

Metal Decking 0 0

Steel Beams 0 0

Steel Columns 0 0

Steel Trusses 0 0



Scrap



Net Scrap 905 1,950



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 20,526 180,198 26,228 224,952

Cradle to Site 20,813 187,977 26,516 232,731

Cradle to Grave 21,592 207,121 27,294 251,875


21,868 219,514 27,570 264,269



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 26,065 250,159 30,884 292,754

Cradle to Site 26,498 259,736 31,317 302,332

Cradle to Grave 27,298 279,177 32,116 321,772


26,015 277,858 30,833 320,453



128

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

demolition



Life Phase


scenario 2a



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

20.8

13 b

etie

20.8

13 b

etie

21.5

92 b

etie

21.8

68 b

etie

26.5

16 ep

ds

20.5

26 b

etie

26.2

28 ep

ds

26.5

16 ep

ds

27.2

94 ep

ds

27.5

70 ep

ds

3.78

633

.596

187.

977

betie

232.

731

epds

180.

198

betie

224.

952

epds

187.

977

betie

232.

731

epds

207.

121

betie

251.

875

epds

264.

269

epds

219.

514

betie

Scenario 2a: 60-Story Building – All Concrete with Wide and Shallow Beams Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-33,596

258,5487,779 N.A. 19,144 -12,394

French EPDs 213,794


2Eq.]

US EPDs

-3,786

30,014

287 N.A. 779 -276French EPDs 24,312


129

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



321.

772

epds

320.

453

epds

Construction

8.15

9 demolition



Life Phase


scenario 2a



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

structural �rm 02

72.4

0426

.065

betie

30.8

84ep

ds

26.4

98be

tie31

.317

epds

26.4

98be

tie31

.317

epds

27.2

98be

tie32

.116

epds

26.0

15be

tie30

.833

epds

279.

177

betie

277.

858

betie

250.

159

betie

292.

754

epds

259.

736

betie

302.

332

epds

259.

736

betie

302.

332

epds


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-72,404

365,1589,577 N.A. 19,441 1,319

French EPDs 322,563


2Eq.]

US EPDs

-8,159

39,043

433 N.A. 799 1,283French EPDs 34,224


130

Scenario 2b60-Story Building – All Concrete Narrow and Deep Beams Scenario


Scenarios 2b

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 2


Office Floors 56



Height [m] 246

Layout

Width [m] 60

Length [m] 40












Columns




Total Length of Columns 4.240

Table 10.1.2b: Geometric Properties for Scenarios 2bSource: CTBUH

Scenario 2b Description• The structure is composed of a concrete core and by concrete columns on the

perimeter. The floor system is composed by a concrete slab with narrow and deep concrete beams.


• Beams 150 mm rebar slab with PT/rebar beams 400 mm wide and 450 mm deep at 3 m off-center. (assume pinned moment connection at core and perimeter for gravity system beam framing).

• Beams and floors are made of 4-5 ksi (30-37 MPa) with normal 50 ksi steel. • Disposable wooden formwork is considered beneath all the floors and beams.


131



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 24,150 33,782

9 ksi Concrete 0 0



4-5 ksi Concrete 58,939 58,939

Steel


WWF 260 260

Steel Studs 0 0

Metal Decking 0 0

Steel Beams 0 0

Steel Columns 0 0

Steel Trusses 0 0



Scrap



Net Scrap 892 1,655

Table 10.2.2b: Inventory of Materials for Scenarios 2bSource: CTBUH


LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 18,058 161,218 22,886 197,445

Cradle to Site 18,330 168,116 23,158 204,344

Cradle to Grave 18,988 185,091 23,816 221,318


18,996 193,378 23,824 229,606



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 22,089 213,372 27,470 251,428

Cradle to Site 22,468 221,623 27,850 259,678

Cradle to Grave 23,147 238,914 28,528 276,970


22,031 237,396 27,413 275,452



132

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



221.

318

epds

229.

606

epds

Construction

3.73

2

demolition



Life Phase


scenario 2b



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

33.1

2218

.058

betie

22.8

86ep

ds

18.3

30be

tie23

.158

epds

18.3

30be

tie23

.158

epds

18.9

88be

tie23

.816

epds

18.9

96be

tie23

.824

epds

185.

091

betie

193.

378

betie

161.

218

betie

197.

445

epds

168.

116

betie

204.

344

epds

168.

116

betie

204.

344

epds

Scenario 2b: 60-Story Building – All Concrete Narrow and Deep Beams Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-33,122

230,5676,899 N.A. 16,974 -8,288

French EPDs 194,340


2Eq.]

US EPDs

-3,732

26,618

272 N.A. 658 -8French EPDs 21,790


133

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



276.

970

epds

275.

452

epds

Construction

6.92

3

demolition



Life Phase


scenario 2b



Demolition

structural �rm 02

61.4

3622

.089

betie

27.4

70ep

ds

22.4

68be

tie27

.850

epds

22.4

68be

tie27

.850

epds

23.1

47be

tie28

.528

epds

22.0

31be

tie27

.413

epds

238.

914

betie

237.

396

betie

213.

372

betie

251.

428

epds

221.

623

betie

259.

678

epds

221.

623

betie

259.

678

epds

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

Scenario 2b: 60-Story Building – All Concrete Narrow and Deep Beams Scenario Structural Firm 02Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-61,436

312,8648,251 N.A. 17,292 1,518

French EPDs 274,808


2Eq.]

US EPDs

-6,923

34,393

379 N.A. 679 1,116French EPDs 29,012


134

Scenario 3a60-Story Building – All Steel (Normal Steel) Diagrid Scenario


Scenarios 3a

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 2


Office Floors 56



Height [m] 246

Layout

Width [m] 60

Length [m] 40












Columns






Scenario 3a Description• The structure is composed of a diagrid of standard structural steel profiles. Core

columns carry vertical loads only. Beams are composed of standard structural steel profiles.

• The steel used for all structural elements is normal 50 ksi (345 MPa) steel.• Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams

are for gravity framing only (not lateral).• Beams are made of standard structural steel profiles.• Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system

metal deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.


135



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 0 0

9 ksi Concrete 0 0

8 ksi Concrete 0 0

6 ksi Concrete 0 0

4-5 ksi Concrete 28,424 28,424

Steel

Steel Rebar 548 548

WWF 260 260

Steel Studs 25 25




Steel Trusses 1,800 4,970



Scrap



Net Scrap 3,255 3,040



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 22,439 266,769 23,576 277,854

Cradle to Site 23,288 280,526 24,424 291,611

Cradle to Grave 23,542 289,123 24,679 300,208


19,025 251,446 20,162 262,531



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 20,723 244,325 21,860 255,410

Cradle to Site 21,560 257,951 22,697 269,037

Cradle to Grave 21,812 266,519 22,949 277,604


17,619 231,712 18,756 242,797



136

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling


starting point of future life of the materials30

0.20

8ep

ds

262.

531

epds

Construction

16.7

98

demolition



Life Phase


scenario 3a



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

149.

071

22.4

39be

tie23

.576

epds

23.2

88be

tie24

.424

epds

23.2

88be

tie24

.424

epds

23.5

42be

tie24

.679

epds

19.0

25be

tie20

.162

epds

289.

123

betie

251.

446

betie

266.

769

betie

277.

854

epds

280.

526

betie

291.

611

epds

280.

526

betie

291.

611

epds

Scenario 3a: 60-Story Building – All Steel (Normal Steel) Diagrid Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-149,071

426,92513,757 N.A. 8,597 37,677

French EPDs 415,840


2Eq.]

US EPDs

-16,798

40,375

848 N.A. 255 4,517French EPDs 39,238


137

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



7.60

4ep

ds

242.

797

epds

Construction

15.1

25

demolition



Life Phase


scenario 3a



Demolition

134.

220

20.7

23be

tie21

.860

epds

21.5

60be

tie22

.697

epds

21.5

60be

tie22

.697

epds

21.8

12be

tie22

.949

epds

17.6

19be

tie18

.756

epds

266.

519

betie

231.

712

betie

244.

325

betie

255.

410

epds

257.

951

betie

269.

037

epds

257.

951

betie

269.

037

epds

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-134,220

389,63013,627 N.A. 8,567 34,807

French EPDs 378,545


2Eq.]

US EPDs

-15,125

36,984

837 N.A. 252 4,193French EPDs 35,848


138

Scenario 3b60-Story Building – All Steel (High-Strength Steel) Diagrid Scenario


Scenarios 3b

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 2


Office Floors 56



Height [m] 246

Layout

Width [m] 60

Length [m] 40












Columns






Scenario 3b Description• The structure is composed of a diagrid of standard structural steel profiles. Core

columns carry vertical loads only. Beams are composed of standard structural steel profiles.

• The steel used for the columns is 65 ksi (450 MPa) high strength steel, while beams and diagrid braces use normal 50 ksi (345 MPa) steel.

• Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral).

• Beams are made of standard structural steel profiles.• Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system



139



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 0 0

9 ksi Concrete 0 0

8 ksi Concrete 0 0

6 ksi Concrete 0 0

4-5 ksi Concrete 28,424 28,424

Steel

Steel Rebar 548 548

WWF 260 260

Steel Studs 25 25







Scrap



Net Scrap 2,996 2,954



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 20,314 239,120 21,451 250,205

Cradle to Site 21,148 252,701 22,285 263,786

Cradle to Grave 21,399 261,258 22,536 272,343


17,272 227,043 18,409 238,128



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 20,031 235,348 21,168 246,433

Cradle to Site 20,863 248,918 22,000 260,003

Cradle to Grave 21,115 257,472 22,252 268,557


17,052 223,821 18,188 234,906



140

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



2.34

3ep

ds

238.

128

epds

Construction

14.4

89

demolition



Life Phase


scenario 3b



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

128.

577

20.3

14be

tie21

.451

epds

21.1

48be

tie22

.285

epds

21.1

48be

tie22

.285

epds

21,3

99be

tie22

.536

epds

17.2

72be

tie18

.409

epds

261.

258

betie

227.

043

betie

239.

120

betie

250.

205

epds

252.

701

betie

263.

786

epds

252.

701

betie

263.

786

epds

Scenario 3b: 60-Story Building – All Steel (High-Strength Steel) Diagrid Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-128,577

378,78313,581 N.A. 8,557 34,216

French EPDs 367,698


2Eq.]

US EPDs

-14,489

35,940

833 N.A. 252 4,127French EPDs 34,803


141

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



8.55

7ep

ds

234.

906

epds

Construction

14.3

81

demolition



Life Phase


scenario 3b



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

127.

617

20.0

31be

tie21

.168

epds

20.8

63be

tie22

.000

epds

20.8

63be

tie22

.000

epds

21.1

15be

tie22

.252

epds

17.0

52be

tie18

.188

epds

257.

472

betie

223.

821

betie

235.

348

betie

246.

433

epds

248.

918

betie

260.

003

epds

248.

918

betie

260.

003

epds

Scenario 3b: 60-Story Building – All Steel (High-Strength Steel) Diagrid Scenario Structural Firm 02Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-127,617

374,05013,570 N.A. 8,555 33,651

French EPDs 362,965


2Eq.]

US EPDs

-14,381

35,548

832 N.A. 251 4,063French EPDs 34,412


142

Scenario 3c60-Story Building – Composite Diagrid Scenario


Scenarios 3c

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 2


Office Floors 56



Height [m] 246

Layout

Width [m] 60

Length [m] 40












Columns





Table 10.1.3c: Geometric Properties for Scenarios 3cSource: CTBUH

Scenario 3c Description• The structure is composed of a diagrid of composite steel/concrete members. • The columns and braces (all composite) standard structural steel sections with

50 ksi (345 MPa) strength as their core, covered with high strength 8-10 ksi (60-70 MPa) reinforced concrete.


• Beams are composed of standard shape structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system



143



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 0 6,049

9 ksi Concrete 0 0



4-5 ksi Concrete 28,424 28,424

Steel

Steel Rebar 778 1,188

WWF 260 260

Steel Studs 25 25



Steel Columns 3,050 610




Scrap



Net Scrap 2,929 2,522



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 21,560 244,061 22,970 257,324

Cradle to Site 22,403 258,185 23,812 271,449

Cradle to Grave 22,751 270,043 24,160 283,307


18,901 239,358 20,310 252,621



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 18,276 200,020 20,118 215,116

Cradle to Site 19,105 214,015 20,947 229,110

Cradle to Grave 19,453 225,903 21,295 240,998


16,230 200,848 18,072 215,943



144

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



3.30

7ep

ds

252.

621

epds

Construction

13.5

62

demolition



Life Phase


scenario 3c



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

120.

353

21.5

60be

tie22

.970

epds

22.4

03be

tie23

.812

epds

22.4

03be

tie23

.812

epds

22.7

51be

tie24

.160

epds

18.9

01be

tie20

.310

epds

270.

043

betie

239.

358

betie

244.

061

betie

257.

324

epds

258.

185

betie

271.

449

epds

258.

185

betie

271.

449

epds

Scenario 3c: 60-Story Building – Composite Diagrid Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-120,353

377,67814,124 N.A. 11,859 30,686

French EPDs 364,414


2Eq.]

US EPDs

-13,562

36,532

842 N.A. 348 3,850French EPDs 35,123


145

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



0.99

8ep

ds

215.

943

epds

Construction

9.59

0

demolition



Life Phase


scenario 3c



Demolition

50.000

100.000

150.000

200.000

250.000

300.000

50.000

100.000

5.000

10.000

15.000

20.000

25.000

5.000

10.000

30.000

structural �rm 02

85.1

0418

.276

betie

20.1

18ep

ds

19.1

05be

tie20

.947

epds

19.1

05be

tie20

.947

epds

19.4

53be

tie21

.295

epds

16.2

30be

tie18

.072

epds

225.

903

betie

200.

848

betie

200.

020

betie

215.

116

epds

214.

015

betie

229.

110

epds

214.

015

betie

229.

110

epds


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-85,104

300,22013,995 N.A. 11,888 25,055

French EPDs 285,125


2Eq.]

US EPDs

-9,590

29,708

829 N.A. 348 3,223French EPDs 27,866


146

Scenario 4a120-Story Building – Concrete Core with Steel (Normal Steel) Frame Scenario


Scenarios 4a

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 3


Office Floors 115



Height [m] 490

Layout

Width [m] 75

Length [m] 50




Upper Core Width [m] 33








Columns






Scenario 4a Description• The structure is composed of a reinforced concrete core and standard structural

steel profiles (i.e. wide flange I-shapes). • The steel used for all structural elements is normal 50 ksi (345 MPa) steel• Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams




147



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 76,864 144,744

9 ksi Concrete 0 0

8 ksi Concrete 23,242 29,938


4-5 ksi Concrete 83,543 83,543

Steel


WWF 764 764

Steel Studs 75 75





Other Fireproofing Spray 2,422 2,422


Scrap



Net Scrap 11,456 11,659



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 103,248 1,130,616 114,721 1,207,488

Cradle to Site 106,307 1,186,952 117,780 1,263,824

Cradle to Grave 108,010 1,219,233 119,482 1,296,106


94,033 1,115,316 105,505 1,192,189



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 104,497 1,136,533 120,317 1,229,855

Cradle to Site 107,643 1,194,378 123,462 1,287,700

Cradle to Grave 109,405 1,227,723 125,225 1,321,045


95,260 1,123,142 111,079 1,216,464



148

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values


during the using phase

not relevantduring the using phase

scrap recycling


starting point of future life of the materials1.

296.

106

epds

1.19

2.18

9ep

ds

Construction

60.3

16

demolition



Life Phase


scenario 4a



Demolition

535.

251

103.

248

betie

114.

721

epds

106.

307

betie

117.

780

epds

106.

307

betie

117.

780

epds

108.

010

betie

119.

482

epds

94.0

33be

tieep

ds

1.21

9.23

3be

tie

1.11

5.31

6be

tie

1.13

0.61

6be

tie1.

207.

488

epds

1.18

6.95

2 be

tie1.

263.

824

epds

1.18

6.95

2be

tie1.

263.

824

epds

105.

505

Scenario 4a: 120-Story Building – Concrete Core with Steel (Normal Steel) Frame Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-535,251

1,742,73956,336 N.A. 32,282 103,918

French EPDs 1,665,866


2Eq.]

US EPDs

-60,316

175,036

3,059 N.A. 1,702 13,977French EPDs 163,564


149

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs ValuesFrench Concrete Values

US EPDs Values




scrap recycling



Construction

58.2

23 demolition



Life Phase


scenario 4a



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

516.

681

104.

497

betie

120.

317

epds

107.

643

betie

123.

462

epds

107.

643

betie

123.

462

epds

109.

405

betie

125.

225

epds

95.2

60be

tie11

1.07

9ep

ds

1.13

6.53

3be

tie1.

229.

855

epds

1.19

4.37

8be

tie1.

287.

700

epds

1.19

4.37

8be

tie1.

287.

700

epds

1.22

7.72

3be

tie1.

321.

045

epds

1.12

3.14

2be

tie1.

216.

464

epds

Scenario 4a: 120-Story Building – Concrete Core with Steel (Normal Steel) Frame Scenario Structural Firm 02Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-516,681

1,746,53657,844 N.A. 33,345 104,581



2Eq.]

US EPDs

-58,223

178,540

3,146 N.A. 1,762 14,146French EPDs 162,720


150

Scenario 4b120-Story Building – Concrete Core with Steel (High Strength Steel) Frame Scenario


Scenarios 4b

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 3


Office Floors 115



Height [m] 490

Layout

Width [m] 75

Length [m] 50












Columns






Scenario 4b Description• The structure is composed of a reinforced concrete core and standard structural

steel profiles (i.e. wide flange I-shapes). • The steel used for the columns is 65 ksi (F450 MPa) high strength steel, while all

other structural elements use normal 50 ksi (345 MPa) steel.• Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams

are for gravity framing only (not lateral).• Beams are made of standard structural steel profiles.• Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal

deck with shear studs. Metal deck, beams and columns will include spray-applied fireproofing.


151



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 76,864 144,744

9 ksi Concrete 0 0

8 ksi Concrete 23,242 29,938


4-5 ksi Concrete 83,543 83,543

Steel


WWF 764 764

Steel Studs 75 75







Scrap



Net Scrap 11,456 11,243



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 103,248 1,130,616 114,721 1,207,488

Cradle to Site 106,307 1,186,952 117,780 1,263,824

Cradle to Grave 108,010 1,219,233 119,482 1,296,106


94,033 1,115,316 105,505 1,192,189



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 101,033 1,091,401 116,852 1,184,723

Cradle to Site 104,155 1,148,958 119,974 1,242,280

Cradle to Grave 105,912 1,182,238 121,731 1,275,560


92,394 1,083,224 108,213 1,176,546



152

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant


US EPDs Values




scrap recycling



Construction

60.3

16 demolition



Life Phase


scenario 4b



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

535.

251

103.

248

betie

114.

721

epds

106.

307

betie

117.

780

epds

106.

307

betie

117.

780

epds

108.

010

betie

119.

482

epds

94.0

33be

tie10

5.50

5ep

ds

1.13

0.61

6be

tie1.

207.

488

epds

1.18

6.95

2be

tie1.

263.

824

epds

1.18

6.95

2be

tie1.

263.

824

epds

1.21

9.23

3be

tie1.

296.

106

epds

1.11

5.31

6be

tie1.

192.

189

epds

Scenario 4b: 120-Story Building – Concrete Core with Steel (High-Strength Steel) Frame Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-535,251

1,742,73956,336 N.A. 32,282 103,918



2Eq.]

US EPDs

-60,316

175,036

3,059 N.A. 1,702 13,977French EPDs 163,564


153

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

54.4

42 demolition



Life Phase


scenario 4b



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

structural �rm 02

483.

131

101.

033

betie

116.

852

epds

104.

155

betie

119.

974

epds

104.

155

betie

119.

974

epds

105.

912

betie

121.

731

epds

92.3

94be

tie10

8.21

3ep

ds

1.09

1.40

1be

tie1.

184.

723

epds

1.14

8.95

8be

tie1.

242.

280

epds

1.14

8.95

8be

tie1.

242.

280

epds

1.18

2.23

8be

tie1.

275.

560

epds

1.08

3.22

4be

tie1.

176.

546

epds

Scenario 4b: 120-Story Building – Concrete Core with Steel (High-Strength Steel) Frame Scenario Structural Firm 02Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-483,131

1,667,85457,557 N.A. 33,280 99,014



2Eq.]

US EPDs

-54,442

171,295

3,122 N.A. 1,757 13,518French EPDs 155,476


154

Scenario 4c120-Story Building – Concrete Core and Compostie Frame Scenario


Scenarios 4c

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 3


Office Floors 115



Height [m] 490

Layout

Width [m] 75

Length [m] 50












Columns






Scenario 4c Description• The structure is composed of a concrete core with composite steel/concrete

columns on the perimeter. • The columns use standard structural steel sections with 50 ksi (34 MPa) strength

as their core, covered with high strength 8-10 ksi (60-70 MPa) reinforced concrete.• Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams




155



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 85,130 179,399

9 ksi Concrete 0 0

8 ksi Concrete 32,563 38,511


4-5 ksi Concrete 83,543 83,543

Steel


WWF 764 764

Steel Studs 75 75




Steel Trusses 2,641 0



Scrap



Net Scrap 8,732 9,376



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 85,569 869,740 98,334 954,722

Cradle to Site 88,511 926,235 101,276 1,011,216

Cradle to Grave 90,417 961,564 103,182 1,046,546


81,009 900,964 93,774 985,945

Table 10.3.4c Results for Scenario 4c Structural Firm 01Source: CTBUH


LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 92,580 943,434 111,429 1,051,636

Cradle to Site 95,626 1,001,996 114,475 1,110,198

Cradle to Grave 97,642 1,039,256 116,491 1,147,458


87,504 973,652 106,353 1,081,854



156

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

34.8

03

demolition



Life Phase


scenario 4c



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

308.

847

85.5

69be

tie98

.334

epds

88.5

11be

tie10

1.27

6ep

ds

88.5

11be

tie10

1.27

6ep

ds

90.4

17be

tie10

3.18

2epd

s

81.0

09be

tie93

.774

epds

869.

740

betie

954.

722

epds

926.

235

betie

1.01

1.21

6ep

ds

926.

235

betie

1.01

1.21

6ep

ds

961.

564

betie

1.04

6.54

6ep

ds

900.

964

betie

985.

945

epds


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-308,847

1,263,56956,494 N.A. 35,330 60,601



2Eq.]

US EPDs

-34,803

133,137

2,942 N.A. 1,906 9,408French EPDs 120,372


157

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

37.6

25

demolition



Life Phase


scenario 4c



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

structural �rm 02

333.

892

92.5

80be

tie11

1.42

9ep

ds

95.6

26be

tie11

4.47

5ep

ds

95.6

26be

tie11

4.47

5ep

ds

97.6

42be

tie11

6.49

1epd

s

87.5

04be

tie10

6.35

3ep

ds

943.

434

betie

1.05

1.63

6ep

ds

1.00

1.99

6be

tie1.

110.

198

epds

1.00

1.99

6be

tie1.

110.

198

epds

1.03

9.25

6be

tie1.

147.

458

epds

973.

652

betie

1.08

1.85

4ep

ds


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-333,892

1,385,52858,562 N.A. 37,260 65,604



2Eq.]

US EPDs

-37,625

149,054

3,046 N.A. 2,016 10,137French EPDs 130,205


158

Scenario 5a120-Story Building – All Concrete with Wide and Shallow Beams Scenario


Scenarios 5a

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 3


Office Floors 115



Height [m] 490

Layout

Width [m] 75

Length [m] 50












Columns






Scenario 5a Description• The structure is composed of a concrete core with concrete columns on the

perimeter. The floor system is composed of a concrete slab with wide and shallow concrete beams.


• 220 mm rebar slab with PT/rebar band beams 2000 mm wide and 450 mm deep at 9 m off-center are used to match column lines.



159



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 104,871 139,518

9 ksi Concrete 0 0

8 ksi Concrete 65,368 82,184

6 ksi Concrete 40,242 49,981

4-5 ksi Concrete 237,496 237,496

Steel


WWF 764 764

Steel Studs 0 0

Metal Decking 0 0

Steel Beams 0 0

Steel Columns 0 0

Steel Trusses 0 0



Scrap



Net Scrap 4,492 5,333



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 82,237 745,752 102,892 899,305

Cradle to Site 84,435 796,798 105,091 950,351

Cradle to Grave 87,190 847,854 107,845 1,001,407


86,286 875,454 106,942 1,029,007



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 96,248 875,061 120,375 1,047,027

Cradle to Site 98,611 930,803 122,737 1,102,769

Cradle to Grave 101,714 988,060 125,841 1,160,026


100,346 1,016,402 124,472 1,188,368



160

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

18.7

89

demolition



Life Phase


scenario 5a



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

166.

741

82.2

37be

tie10

2.89

2ep

ds

84.4

35be

tie10

5.09

1ep

ds

84.4

35be

tie10

5.09

1ep

ds

87.1

90be

tie10

7.84

5epd

s

86.2

86be

tie10

6.94

2ep

ds

745.

752

betie

899.

305

epds

796.

798

betie

950.

351

epds

796.

798

betie

950.

351

epds

847.

854

betie

1.00

1.40

7ep

ds

875.

454

betie

1.02

9.00

7ep

ds


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-166,741

1,066,04651,046 N.A. 51,056 -27,600

French EPDs 912,493


2Eq.]

US EPDs

-18,789

121,681

2,199 N.A. 2,755 903French EPDs 101,026


161

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

22.3

05

demolition



Life Phase


scenario 5a



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

197.

935

96.2

48be

tie12

0.37

5ep

ds

98.6

11be

tie12

2.73

7ep

ds

98.6

11be

tie12

2.73

7ep

ds

101.

714

betie

125.

841e

pds

100.

346

betie

124.

472

epds

875.

061

betie

1.04

7.02

7ep

ds

930.

803

betie

1.10

2.76

9ep

ds

930.

803

betie

1.10

2.76

9ep

ds

988.

060

betie

1.16

0.02

6ep

ds

1.01

6.40

2be

tie1.

188.

368

epds


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-197,935

1,244,96255,742 N.A. 57,257 -28,342



2Eq.]

US EPDs

-22,305

142,679

2,363 N.A. 3,103 1,369French EPDs 118,553


162

Scenario 5b120-Story Building – All Concrete with Narrow and Deep Beams Scenario


Scenarios 5b

Configuration

Lobby 1

Lobby Height [m] 6

Mec. Floors 3


Office Floors 115



Height [m] 490

Layout

Width [m] 75

Length [m] 50












Columns






Scenario 5b Description• The structure is composed of a concrete core with concrete columns on the

perimeter. The floor system is composed of a concrete slab with narrow and deep concrete beams.


• Beams 150 mm rebar slab with PT/rebar beams 400 mm wide and 450 mm deep at 3 m off-center (assume pinned moment connection at core and perimeter for gravity system beam framing).



163



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 104,871 139,518

9 ksi Concrete 0 0

8 ksi Concrete 65,368 82,184

6 ksi Concrete 40,242 49,981

4-5 ksi Concrete 173,232 173,232

Steel


WWF 764 764

Steel Studs 0 0

Metal Decking 0 0

Steel Beams 0 0

Steel Columns 0 0

Steel Trusses 0 0



Scrap



Net Scrap 4,455 5,568



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 74,982 689,966 93,067 818,456

Cradle to Site 77,126 737,493 95,211 865,983

Cradle to Grave 79,525 782,172 97,610 910,662


77,836 797,704 95,921 926,194



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 90,338 837,016 111,894 983,920

Cradle to Site 92,683 889,693 114,239 1,036,597

Cradle to Grave 95,435 940,617 116,991 1,087,520


92,871 953,253 114,426 1,100,156



164

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant





scrap recycling



Construction

18.6

32

demolition



Life Phase


scenario 5b



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

165,

347

74.9

82be

tie93

.067

epds

77.1

26be

tie95

.211

epds

77.1

26be

tie95

.211

epds

79.5

25be

tie97

.610

epds

77.8

36be

tie95

.921

epds

689.

966

betie

818.

456

epds

737.

493

betie

865.

983

epds

737.

493

betie

865.

983

epds

782.

172

betie

910.

662

epds

797.

704

betie

926.

194

epds

Scenario 5b: 120-Story Building – All Concrete with Narrow and Deep Beams Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-165,347

983,80347,527 N.A. 44,679 -15,532

French EPDs 855,313


2Eq.]

US EPDs

-18,632

111,699

2,144 N.A. 2,399 1,689French EPDs 93,615


165

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant





scrap recycling



Construction

23.2

86

demolition



Life Phase


scenario 5b



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

structural �rm 02

206.

646

90.3

38be

tie11

1.89

4ep

ds

92.6

83be

tie11

4.23

9ep

ds

92.6

83be

tie11

4.23

9ep

ds

95.4

35be

tie11

6.99

1ep

ds

92.8

71be

tie11

4.42

6ep

ds

837.

016

betie

983.

920

epds

889.

693

betie

1.03

6.59

7ep

ds

889.

693

betie

1.03

6.59

7ep

ds

940.

617

betie

1.08

7.52

0ep

ds

953.

253

betie

1.10

0.15

6ep

ds

Scenario 5b: 120-Story Building – All Concrete with Narrow and Deep Beams Scenario Structural Firm 02Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-206,646

1,190,56652,677 N.A. 50,923 -12,636



2Eq.]

US EPDs

-23,286

135,180

2,345 N.A. 2,751 2,564French EPDs 113,624


166

Scenario 6a120-Story Building – All Steel (Normal Steel) Diagrid Scenario


Scenarios6a

S.F. 01 S.F. 02

Configuration

Lobby 1 0

Lobby Height [m] 6 6

Mec. Floors 3 3

Mec. Floors Height [m] 8 8

Office Floors 115 115

Floor-to-Floor Height [m] 4 4

Total Floor Number 119 119

Height [m] 490 490

Layout

Width [m] 75 75

Length [m] 50 50

Lower Core Width [m] 55 55

Lower Core Length [m] 23 23

Lower Core Floors [story] 40 40

Upper Core Width [m] 33 33

Upper Core Length [m] 23 23

Upper Core Floors [story] 79 79

Gross Total Floor Area [m2] 446,250 446,250

Lower Net Area [m2] 99,400 99,400

Upper Net Area [m2] 236,289 236,289

Total Net Area [m2] 335,689 335,689

Built Floor Area [m2] 372,543 372,543

Columns

Number of Lower Columns 24 *

Number of Upper Columns 0 6

Number of diagrid Columns 60 60

Total Length of Columns 48,510 38,670

NOTE

Structural firm #2 decided to have a concrete core in the diagrid system so there are only 6 columns supporting the floors in the upper portion of the

building where the core steps back. Check for structural concrete.


Scenario 6a_Description• The structure is composed of a diagrid of standard structural steel

profiles. Core columns carry vertical loads only. In case of inadequate stiffness, concrete core and outriggers (at the service floor levels) can be added.

• The steel used for all structural elements is normal 50 ksi (345 Mpa) steel.• Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge

beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles.• Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga

system metal deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.

Additional Remarks:

As evidenced in this study, an all diagrid solution loses efficiency when the tower becomes too slender (i.e., the short direction of a rectangular floor plate). Diagrid tubes have been shown to be most effective on their own when the tower’s proportions are square. This finding points to the need for designers to exercise appropriate judgment when initially selecting building systems.


167



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete




6 ksi Concrete 0 0

4-5 ksi Concrete 83,543 83,543

Steel


WWF 764 764

Steel Studs 75 75







Scrap



Net Scrap 16,901 12,250



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 124,594 1,542,438 127,936 1,575,020

Cradle to Site 129,526 1,620,953 132,868 1,653,535

Cradle to Grave 130,250 1,637,140 133,592 1,669,722


105,907 1,428,242 109,248 1,460,823

Table 10.3.6a Results for Scenario 6a Structural Firm 01Source: CTBUH


LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 118,259 1,265,348 137,869 1,377,401

Cradle to Site 123,287 1,355,235 142,898 1,467,287

Cradle to Grave 125,222 1,393,478 144,832 1,505,531


110,906 1,291,760 130,516 1,403,813



168

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

114.

594 demolition



Life Phase


scenario 6a



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

1.01

6.92

9

129.

526

betie

132.

868

epds

130.

250

betie

133.

592

epds

105.

907

betie

109.

248

epds

1.54

2.43

8be

tie1.

575.

020

epds

1.62

0.95

3be

tie1.

653.

535

epds

1.62

0.95

3be

tie1.

653.

535

epds

1.63

7.14

0be

tie1.

669.

722

epds

1.42

8.24

2be

tie1.

460.

823

epds

129.

526

betie

132.

868

epds

124.

594

betie

127.

936

epds


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-1,016,929

2,591,94978,515 N.A. 16,187 208,899



2Eq.]

US EPDs

-114,594

242,530

4,932 N.A. 724 24,344French EPDs 239,188


169

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

64.6

32 demolition



Life Phase


scenario 6a



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

structural �rm 02

573.

557

123.

287

betie

142.

898

epds

125.

222

betie

144.

832

epds

110.

906

betie

130.

516

epds

1.26

5.34

8be

tie1.

377.

401

epds

1.35

5.23

5be

tie1.

467.

287

epds

1.35

5.23

5be

tie1.

467.

287

epds

1.39

3.47

8be

tie1.

505.

531

epds

1.29

1.76

0be

tie1.

403.

813

epds

123.

287

betie

142.

898

epds

118.

259

betie

137.

869

epds


Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-573,557

1,950,95889,887 N.A. 38,243 101,718



2Eq.]

US EPDs

-64,632

202,501

5,029 N.A. 1,934 14,316French EPDs 182,891


170

Scenario 6b120-Story Building – All Steel (High Strength Steel) Diagrid Scenario

Scenario 6b Description• The structure is composed of a diagrid of standard structural steel

profiles. Core columns carry vertical loads only. In case of inadequate stiffness, concrete core and outriggers (at the service floor levels) can be added.

• The steel used for the columns is 65 ksi (F450 Mpa) high strength steel, while beams and diagrid braces use normal 50 ksi (345 Mpa) steel.


• Beams are made of standard structural steel profiles.• Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga

system metal deck with shear studs. Metal deck, beams and columns will include spray-applied fireproofing.


Scenarios6b

S.F. 02

Configuration

Lobby 1 1


Mec. Floors 3 3





Height [m] 490 490

Layout

Width [m] 75 75

Length [m] 50 50








Lower Net Area [m2] 99,400 99,400

Upper Net Area [m2] 236,289 236,289

Total Net Area [m2] 335,689 335,689


Columns

Number of Lower Columns 24 *


Number of diagrid Columns 60 60


NOTE

Structural firm #2 decided to have a concrete core in the diagrid system so there are only 6 columns supporting the floors in the upper portion of the

building where the core steps back. Check for structural concrete.


Additional Remarks:

As evidenced in this study, an all diagrid solution loses efficiency when the tower becomes too slender (i.e., the short direction of a rectangular floor plate). Diagrid tubes have been shown to be most effective on their own when the tower’s proportions are square. This finding points to the need for designers to exercise appropriate judgment when initially selecting building systems.


171



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete




6 ksi Concrete 0 0

4-5 ksi Concrete 83,543 83,543

Steel


WWF 764 764

Steel Studs 75 75







Scrap



Net Scrap 16,457 12,250



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 120,894 1,494,230 124,236 1,526,811

Cradle to Site 125,801 1,572,438 129,142 1,605,019

Cradle to Grave 126,519 1,588,556 129,860 1,621,137


102,845 1,385,602 106,187 1,418,184



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 118,259 1,265,348 137,869 1,377,401

Cradle to Site 123,287 1,355,235 142,898 1,467,287

Cradle to Grave 125,222 1,393,478 144,832 1,505,531


110,906 1,291,760 130,516 1,403,813



172

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

110.

556 demolition



Life Phase


scenario 6b



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

981.

093

125.

801

betie

129.

142

epds

126.

519

betie

129.

860

epds

102.

845

betie

106.

187

epds

1.49

4.23

0be

tie1.

526.

811

epds

1.57

2.43

8be

tie1.

605.

019

epds

1.57

2.43

8be

tie1.

605.

019

epds

1.58

8.55

6be

tie1.

621.

137

epds

1.38

5.60

2be

tie1.

418.

184

epds

125.

801

betie

129.

142

epds

120.

894

betie

124.

236

epds

Scenario 6b: 120-Story Building – All Steel (High Strength Steel) Diagrid Scenario Structural Firm 01Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-981,093

2,507,90478,208 N.A. 16,118 202,953



2Eq.]

US EPDs

-110,556

234,792

4,907 N.A. 718 23,673French EPDs 231,450


173

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

64.6

32

demolition



Life Phase


scenario 6b



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

573.

557

123.

287

betie

142.

898

epds

125.

222

betie

144.

832

epds

110.

906

betie

130.

516

epds

1.26

5.34

8be

tie1.

377.

401

epds

1.35

5.23

5be

tie1.

467.

287

epds

1.35

5.23

5be

tie1.

467.

287

epds

1.39

3.47

8be

tie1.

505.

531

epds

1.29

1.76

0be

tie1.

403.

813

epds

123.

287

betie

142.

898

epds

118.

259

betie

137.

869

epds

Scenario 6b: 120-Story Building – All Steel (High Strength Steel) Diagrid Scenario Structural Firm 02Graphical Representation of the Research Result

Benefits of Using

Recycled Inputs

Production Process



DemolitionCredits

for Scrap


US EPDs-573,557

1,950,95889,887 N.A. 38,243 101,718



2Eq.]

US EPDs

-64,632

202,501

5,029 N.A. 1,934 14,316French EPDs 182,891


174

Scenario 6c120-Story Building – Composite Diagrid Scenario

Scenario 6c Description• The structure is composed of a diagrid of composite steel/concrete

members. In case of inadequate stiffness, concrete core and outriggers (at the service floor levels) can be added.

• The columns and braces (all composite) are standard structural steel sections with 50 ksi (345 Mpa) strength as their core, covered with high strength 8-10 ksi (60-70 MPa) reinforced concrete.


• Beams are composed of standard shape structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga

system metal deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.


Scenarios6c

S.F. 01 S.F. 02

Configuration

Lobby 1 1


Mec. Floors 3 3





Height [m] 490 490

Layout

Width [m] 75 75

Length [m] 50 50








Lower Net Area [m2] 99,400 99,400

Upper Net Area [m2] 236,289 236,289

Total Net Area [m2] 335,689 335,689


Columns

Number of Lower Columns * **


Number of Diagrid Columns 60 60


NOTE

*Structural firm #1 decided to have a concrete core in the composite diagrid system only, so

there are only 6 columns supporting the floors in the upper portion of the building where the core

steps back. Check for structural concrete**Structural firm #2 decided to have a concrete

core in the diagrid system so there are only 6 columns supporting the floors in the upper

portion of the building where the core steps back. Check for structural concrete.


Additional Remarks:

A composite concrete and steel diagrid on the building perimeter, which creates a “tube,” resulted (on average) in the best solution for the 120-story building, as all overturning is carried on the exterior. The tube’s efficiency was challenged in the narrow direction, though, and required supplemental stiffening to make it most effective.


175



Firm 01 [tons]

Structural Firm 02

[tons]

Concrete

10 ksi Concrete 56,925 55,306


8 ksi Concrete 31,050 17,281

6 ksi Concrete 37,261 32,799

4-5 ksi Concrete 83,543 83,543

Steel


WWF 764 764

Steel Studs 75 75



Steel Columns 0 648




Scrap



Net Scrap 9,860 9,884



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 81,929 882,647 91,501 949,705

Cradle to Site 84,863 935,740 94,435 1,002,798

Cradle to Grave 86,208 965,166 95,780 1,032,224


74,126 874,949 83,698 942,007



LCA Modules

French EPDs US EPDs

GWP [t CO

2Eq.]

EE [GJ]

GWP [t CO

2Eq.]

EE [GJ]

Cradle to Gate 86,092 934,628 97,011 1,006,216

Cradle to Site 88,999 987,616 99,918 1,059,203

Cradle to Grave 90,375 1,017,568 101,294 1,089,156


78,319 927,962 89,238 999,550



176

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

42.7

77

demolition



Life Phase


scenario 6c



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

379.

606

84.8

63be

tie94

.435

epds

86.2

08be

tie95

.780

epds

74.1

26be

tie83

.698

epds

882.

647

betie

949.

705

epds

935.

740

betie

1.00

2.79

8ep

ds

935.

740

betie

1.00

2.79

8ep

ds

965.

166

betie

1.03

2.22

4ep

ds

874.

949

betie

942.

007

epds

84.8

63be

tie94

.435

epds

81.9

29be

tie91

.501

epds


Benefits of Using

Recycled Inputs

"Production Process"



DemolitionCredits

for Scrap

"Embodied Energy" [GJ]

US EPDS-379,606

1,329,31153,093 N.A. 29,427 90,217

French EPDS 1,262,253

"Global Warming Potential" [tCO

2Eq.]

US EPDS

-42,777

134,278

2,934 N.A. 1,345 12,082French EPDS 124,705


177

EmbodiedEnergy [GJ]

Years

Years10 20 50 60 70

10 20 50 60 70

RecycledInput



not relevant

US EPDs Values


US EPDs Values




scrap recycling



Construction

48.6

10

demolition



Life Phase


scenario 6c



Demolition

300.000

600.000

900.000

1.200.000

1.500.000

1.800.000

300.000

600.000

40.000

80.000

120.000

140.000

160.000

40.000

80.000

180.000

structural �rm 02

431.

377

88.9

99be

tie99

.918

epds

90.3

75be

tie10

1.29

4ep

ds

78.3

19be

tie89

.238

epds

934.

628

betie

1.00

6.21

6ep

ds

987.

616

betie

1.05

9.20

3ep

ds

987.

616

betie

1.05

9.20

3ep

ds

1.01

7.56

8be

tie1.

089.

156

epds

927.

962

betie

999.

550

epds

88.9

99be

tie99

.918

epds

86.0

92be

tie97

.011

epds


Benefits of Using

Recycled Inputs

"Production Process"



DemolitionCredits

for Scrap

"Embodied Energy" [GJ]

US EPDS-431,377

1,437,59352,988 N.A. 29,953 89,606

French EPDS 1,366,005

"Global Warming Potential" [tCO

2Eq.]

US EPDS

-48,610

145,621

2,907 N.A. 1,376 12,056French EPDS 134,703


178

This publication presents the results of a three-year-long research project sponsored by ArcelorMittal.

The authors would like to recognize the work and support of the whole research team, including: Payam Bahrami (CTBUH), Martina Belmonte (CTBUH/Iuav), Donald Davies (Magnusson Klemencic Associates), Jean-Claude Gerardy (ArcelorMittal), Eleonora Lucchese (CTBUH/Iuav), Mattia Mercanzin (CTBUH/Iuav), Nicoleta Popa (ArcelorMittal), Meysam Tabibzadeh (CTBUH), Dario Trabucco (CTBUH/Iuav, Principal Investigator), Olivier Vassart (ArcelorMittal), and Antony Wood (CTBUH, Co-Principal Investigator).

A large group of firms and professionals contributed to the research by providing specific information that was used in various parts of the research to populate the bill of quantities for the various scenarios, the characterization factors, etc.:

Engineering Firms: Arup, Buro Happold, Halvorson & Partners, Magnusson Klemencic Associates, McNamara/Salvia, Nishkian Menninger, Severud Associates, SOM, Thornton Tomasetti, Walter P Moore, Weidlinger Associates, WSP;

Demolition Contractors and C&D Waste Processing Plants: ACM Recycling, Bluff City Materials, Brandenburg, Despe, MBL Recycling, Taisei;

Construction Companies and Material Providers: Clark Construction, Gerdau Ameristeel, Grace, Putzmeister, Schnell, Terex Group.

Acknowledgements

| Acknowledgements © Council on Tall Buildings and Urban Habitat

179

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Goode, M. G. (2004). “Fire Protection of Structural Steel in High-Rise Buildings” [Online] Available at: http://www.fire.nist.gov/bfrlpubs/build04/PDF/b04047.pdf [Accessed 09 Feb 2015].

Guggemos, A. A. & Horvath, A. (2005) “Comparison of Environmental Effects of Steel- and Concrete-Framed Buildings”, Journal of Infrastructure Systems, ASCE, Volume 11(2), pages 93-101,

Guggemos, A. A. & Horvath, A. (2006) “Decision support tool for environmental analysis of commercial building structures”, Journal of Architectural Engineering, Dec.12(4).

Guggemos, A. et al. (2010) “Greening Structural Steel Design, Fabrication and Erection: A Case Study of the National Renewable Energy” Laboratory Research Support Facilities Project, Fort Collins, CO: Colorado State University.

Hajibabai, L., Aziz, Z. & Pena-Mora, F. (2011) “Visualizing greenhouse gas emissions from construction activities”, Construction Innovation, Volume 11(3), pp. 356-370.

Hasan, S. et al. (2013) “Productivity and CO2 emission analysis for tower crane utilization on high-rise building projects”,Automation in Construction, Volume 31, pp. 255-264.

Hong, T., Yoon, C., Jang, M. & Park, H. (2014) “Assessment Model for Energy Consumption and Greenhous Gas Emission during Building Construction”, Journal of Management in Engineering, march/april, pp. 226-235.

Huang, C., Wong, C. & Tam , C. M. (2011) “Optimization of tower crane and material supply locations in a high-rise building site by mixed-integer linear programming”, Automation in Construction, Volume20(5) Aug., pp. 571-580.

Hudson, J., (1993) “Excavation, Support and Monitoring”, in “Comprehensive Rock Engineering: Principles, Practice & Projects” pp. 1-37.

Hu, M., Kleijn, R., Bozhilova, K. P. & Di Maio, F. (2013) “An approach to LCSA: the case of concrete recycling”, Volume 18(9), June 2013, pp. 1793-1803.

Kim, K., Shin, M. & Cha, S. (2013) “Combined effects of recycled aggregate and fly ash towards concrete sustainability”, Construction and Building Materials, Volume 48, pp. 499-507.

Knoeri, C., Binder, C. & Althaus, H.-J. (2011) “Decisions on recycling: Construction stakeholders’ decisions regarding recycled mineral construction materials”, Resources, Conservation and Recycling, Volume 55, pp. 1039-1050.

Kofoworola, O. F. & Gheewala, S. H., (2009) “Life Cycle Assessment of a typical office building in Thailand”, Energy and Buildings, Volume 41, pp. 1076-1083.

Lenzen, S. et al. (2004) “System Boundary Selection in Life-Cycle Inventories Using Hybrid Approaches”, Environmental Science & Technology, Volume 38(3), pp. 657-664.

Leslie, T. (2013) “The Monadnock Building, Technically Reconsidered”. CTBUH Journal, Volume Issue IV.

Li, X., Zhu, Y. & Zhang, Z. (2010). “A LCA-based environmental impact assessment model for construction processes”, Building and Environment, March, Volume 45(3), pp. 766-775.

Marinkovic’, A., Radonjanin, V., Malešev, M. & Ignjatovic’, I. (2010) “Comparative environmental assessment of natural and recycled aggregate concrete”, Waste Management, Volume 30, pp. 2255-2264.

Martínez, E., Nuñez, Y. & Sobaberas, E. (2013) “End of life of buildings: three alternatives, two scenarios. A case study”, The International Journal of Life Cycle Assessment, Volume 18, March, p. 1082–1088.

Menard, Y. et al. (2013) “Innovative process routes for a high-quality concrete recycling”, Waste Management, Volume 33, pp. 1561-1565.

Mizutani, R. & Yoshikai, S. (2011) “A New Demolition Method for Tall Buildings: Kajima Cut&Take Down Method”. CTBUH Journal, Issue 4, pp. 36-41.

O’Donnell, J., Keane, M., Morrissey, E. & Bazjanac, V. (2013) “Scenario modeling: A holistic environmental and energy management method for building operation optimization”, Energy and Buildings, Volume 62, July, pp. 146-157.

Oka, T., Suzuki, M. & Konnya, T. (1993) “The estimation of energy consumption and amount of pollutants due to the construction of buildings”, Energy and Buildings, volume 19, 1993, pages 303-311

Oldfield, P., Trabucco, D. & Wood, A. (2009) “Five energy generations of tall buildings: an historical analysis of energy consumption in high-rise buildings”, The Journal of Architecture, Volume 14(5), pp. 591-613.


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Olearczyk, J., Mohammed Al-Hussein, M. & Bouferguenè, A. (2014) “Evolution of the crane selection and on-site utilization process for modular construction multilifts”, Automation in Construction, Volume 43, pp. 59-72.

Plank, R. J. (2005) “Sustainable building construction for structural engineers”, The Structural Engineer, 17th June, 83(11), pp. 30-33

Raman , M. (2001) “Aspects of Energy Consumption in Tall Office Buildings”. CTBUH Review, Volume 1, Issue 3.Ramesh, T., Prakash, R. & Shukla, K. K. (2010) “Life cycle energy analysis of buildings: An overview”, Energy and Buildings, Volume 42(10), Oct., pp. 1592-1600.

Rao, A., Jha, K. N. & Misra, S. (2007) “Use of aggregates from recycled construction and demolition waste in concrete”, Resources Conservation & Recycling, Volume 50, pp. 71-81.

Sakumoto, Y., Nagata, T., Kodaira, A. & Saito, Y. (2001) “Durability Evaluation of Intumescent Coating for Steel Frames”, Journal of Materials in Civil Engineering, Volume 13, July/august, pp. 274-281.

Shapira, A., Lucko, G. & Schexnayder, C. J. (2007) “Cranes for Building Construction Projects”. Journal of Construction Engineering And Management, ASCE, Sep.2007, pp. 690-700

Sharrard, A. L., Matthews, H. S. & Roth, M. (2007) “Environmental implications of construction site energy use and electricity generation”, Journal of Construction Engineering and Management, Volume 133, pp. 846-854.

Sharrard, A. L., Matthews, S. & Reis, S. (2008) “Estimating construction project environmental effects using an input-output-based hybrid life-cycle assessment model”, Journal of Infrastructure Systems, Volume 14(4), pp. 327-336.

Silvaa, R. V., DeBrito, J. & Dhir, R. K. (2014) “Properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production”, Construction and Building Materials, Volume 65, pp. 201-217.

Soutsos, M. N., Tang, K. & Millard, S. G., (2011) “Use of recycled demolition aggregate in precast products, phase II: Concrete paving blocks”, Construction and Building Materials, Volume 25, pp. 3131-3143.

Srinivasan, R., Ingwersen, W., Trucco, C. & Ries, R. (2014) “Comparison of energy-based indicators used in life cycle assessment tools for buildings”, Building and Environment, Volume 79, May, pp. 138-151.

Stein, R. G. (1977) “Observations on Energy Use in Buildings”, Journal of Architectural Education, Volume 30(3), pp. 36-41.

Thormark, C. (2001) “Conservation of energy and natural resources by recycling building waste”, Resources, Conservation and Recycling, September, 33(2), pp. 113-130.

Trabucco, D. (2008) “An analysis of the relationship between service cores and the embodied/running energy of tall buildings”. In “The structural design of tall and special buildings”, Volume 17(5), pp. 941-952.

Trabucco, D. & Fava, P. (2013) “Confronting the Question of Demolition or Renovation”. CTBUH Journal, Book Chapter-Part Chapter, 2013, Issue IV, pp. 38-43.

Treloar, G. J., Fay R., R., Ilozor, B. & Love, P. E. D. (2001) “An analysis of the embodied energy of office buildings by height”. Facilities, Vol. 19 Iss: 5/6, pp.204 – 214

Ukhov, S. B. (2003) “Soil Mechanics and Foundation Engineering. Scientific Research Institute of Foundation and Underground Structures”, Volume 40(5), pp. 173-175.

Ulsen, C. et al. (2013) “Production of recycled sand from construction and demolition waste”, Construction and Building Materials, Volume 40, pp. 1168-1173.

Vinnakota, S., Foley, C. M. & Vinnakota, M. R., (2003) “Design of Partially or Fully Composite Beams, with Ribbed Metal Deck, Using LRFD Specifications”, Engineering Journal / American Institute of Steel Construction, pp. 60-78.

Wagih, A. M., El-Karmoty, H. Z., Ebid, M. & Okba, S. H. (2013), “Recycled construction and demolition concrete waste as aggregate for structural concrete”. Housing and Building National Research Center, Volume 9, pp. 193-200.

Wahlstrom, M. et al., 2000. Environmental quality assurance system for use of crushed mineral demolition wastes in road constructions. Waste Management, Volume 20, pp. 225-232.

Webster, M., 2010. Design for Adaptability and Deconstruction. In: Sustainability Guidelines for the Structural Engineer. Reston(Virginia): American Society of Structural Engineers, pp. 85-92.

Weisenberger, G., 2010. “The Fabrication Factor”., Modern Steel Construction, Volume July 2010, pp. 56-57. [Online] Available at: http://www.hamil.com/pdfs/modern_steel.pdf [Accessed april 2015].

Weismantle, P. A., Smith, G. L. & Sheriff , M. (2007) “Burj Dubai: an architectural technical design case study. The Structural Design of Tall and Special Buildings”, December, 16(4), pp. 335-360.

Willis, C. (1986) “ Zoning and Zeitgeist: The Skyscraper city in the 1920’s”, Journal of the society of architectural historians, Volume 45, pp. 47-59.

Wong, J. et al.(2013) “Toward low-carbon construction processes: the visualization of predicted emission via virtual prototyping technology”. Automation in Construction, Volume 33, pp.

Wood, A., (2007) “Sustainability: A New High-Rise Vernacular”. The Structural Design of Tall and Special Buildings. Dec., 16(4), pp. 401-410.

Yellishetty, M., Mudd, G. M., Ranjith, P. G. & Tharumarajah, A., 2011. Environmental life-cycle comparisons of steel production and recycling: sustainability issues, problems and prospects. Environmental Science & Policy, October, 14(6), pp. 650-663.

Zhang, H., Zhai, D. & Yang, Y. N., 2014. Simulation-based estimation of environmental pollutions from construction process”. Journal of Cleaner Production, Volume 76, pp. 85-94.

Zygomalas, I. & Baniotopoulos, C. (2013) “Uncertainty in Life-Cycle Assessment Induced by Life-Cycle Inventory Data: The Case of Structural Steel”. Engineering Journal


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Conference Papers:

Ahn, C., Rekapalli, P. V., Martìnez, J. C. & Pena-Mora, F., (2009) “Sustainability analysis of earthmoving operations”. Proceeding of Winter Simulation Conference, Austin, TX, pp. 2605-2611.

Ali, M. & Armstrong, P. (2008) “Overview of Sustainable Design Factors in High-Rise Buildings”, Conference Proceeding CTBUH 8th World Congress, Dubai. March 3-5 2008.

Balridge, S. M. (2008) ”Tall Structural Sustainability in an Island Context: the Hawaii Experience” , Conference Proceeding CTBUH 8th World Congress, Dubai. March 3-5 2008.

Frechette, R. & Gilchrist, R., (2008) “Towards Zero Energy: A Case Study of the Pearl River Tower Guangzhou, China”. Dubai, CTBUH Technical Paper, Conference Proceeding, CTBUH 8th World Congress, Dubai, March 3-5, 2008

Gangolells M., Casals, M., Gassò, S., Forcada, N., Roca, X. (2007) “A methodology for predicting the magnitude of environmental impacts related to the building construction process”, CIB World Building Congress 2007

Ismail, F., Baharuddin, H. & Marhani, M. A. (2013) “Factors towards Site Management Improvement for Industrialized Building System (IBS) Construction” AcE-Bs 2013 Hanoi (ASEAN Conference on Environment-Behaviour Studies), Hanoi Architectural University, Hanoi, Vietnam, 18-21 March 2013, Procedia - Social and Behavioral Sciences, Volume 85, 20 September 2013, Pages 43–50

Kayashima, M., Shinozaki, Y., Koga, T. & Ichihara, H. (2012) “A New Demolition System for High-Rise Buildings”, Asia Ascending CTBUH 9th World Congress 2012 Proceedings, pp. 631-636, Shanghai, CTBUH.

Kahn, F. (1969) “Recent structural systems in steel for high-rise buildings”, Proceeding of British Constructional Steelwork Association Conference on Steel in Architecture,. British Constructional Steelwork Association: London.

Killa, S. & Smith, R. (2008) “Harnessing Energy in Tall Buildings: Bahrain World Trade Center and Beyond”, CTBUH Technical Paper, Conference Proceeding, CTBUH 8th World Congress, Dubai, March 3-5,2008

Leung, L. & Weismantle, P. (2008) “Sky-Sourced Sustainability - How Super Tall Buildings Can Benefit From Height”, CTBUH Technical Paper, Conference Proceeding, CTBUH 8th World Congress, Dubai, March 3-5,2008

Matthews, H. S., Roth, M., Sharrad, A. & Bilec, M. (2005) “Economic and environmental implications of construction energy use and generation under new EPA (environmental protection agency) emission standards”, ASCE, Construction Research Congress 2005: Broadening perspectives, San Diego, Califrnia, United States, April 5-7, 2005, pp. 1-7

Nitivattananon, V. & Borongan, G. (2007) “Construction and Demolition Waste Management: Current Practices in Asia”, In:Proceedings of the International Conference on Sustainable Solid Waste Management, 5-7 September, Chennai, India. pp. 97-104

Ochsendorf, J. (2005) “Sustainable Engineering: The Future of Structural Design”, Conference Proceeding Structures Congress 2005: Metropolis and Beyond, New York, New York, United States, April 20-24, 2005, American Society of Civil Engineering, pp. 1 9

Oldfield, P. (2012) “Embodied Carbon and High-Rise”, CTBUH Technical Paper, Conference Proceeding, CTBUH 9th World Congress, Shanghai 2012.

Partridge, L, Gan E. S., Wei L., “Factors Influencing Building Energy in Different Climates” CTBUH Technical Paper, Conference Proceeding, CTBUH 9th World Congress Shanghai, 2012.

Quick, H. (2005) “Report on foundation design for high-rise buildings”, CTBUH Technical Paper, Conference Proceeding, CTBUH 8th World Congress, Dubai, March 3-5,2008

Shine, K. P., Derwent, R. G., Wuebbles, D. J. & Morcrette, J. J. (2010) “Radiative Forcing of Climate”, IPCC (Intergovernmental Panel On Climate Change).

Si, C., Jiang, W., Cui, Y. & He, J. (2012) “Supertall building Pile-Raft Foundation Design on Soft Soil”, CTBUH Technical Paper, Conference Proceeding, CTBUH 9th World Congress, Shanghai 2012.

Tomasetti, R., Abruzzo , J. & Panariello, G. (2005) “Applying the lesson learned from 9/11 to the Remedial Protective Design of Existing Buildings”, Conference Proceeding Paper, Part of: Structures Congress 2005: Metropolis and Beyond, Section: Forensic Engineering Symposium, pp. 1-4, ASCE, New York.

Trabucco, D. (2011) “The LCA of Tall Buildings: a Quick Pre-Design Assessment Tool” (unpublished). Seoul, CTBUH.

Trabucco, D. (2012) “Life Cycle Energy Analysis of Tall Buildings: Design Principles”, CTBUH Technical Paper, Conference Proceeding, CTBUH 9th World Congress, Shanghai 2012.

Trabucco, D., Wood, A., Tabibzadeh, M. & Vassart, O. (2014) “CTBUH Research Project: A Whole Life Cycle Assessment of the Sustainable Aspects of Structural systems in Tall Buildings - Interim Report”, CTBUH 9th World Congress, Shanghai 2012.

Reports:

SEI / AISC Thermal Steel Bridging Task Committee (2012) “Thermal Bridging Solutions: Minimizing Structural Steel’s Impact on Building Envelope Energy Transfer”, Supplement to Modern Steel Construction, March, pp. 1-16.

BAUFORUMSTAHL (2008) “Architect’s Guide Facilitating the market development for sections in industrial halls and lowrise buildings (SECHALO”. In: P. T. a. C. Arcelor Mittal, ed. Steel Buildings In Europe. Multi-Story Steel Buildings. s.l.:s.n.

BIS (2010) “Estimating the amount of CO2

emissions that the construction industry can influence, Supporting materials for the Low Carbon Construction” IGT Report, Crown: London

Bovis Lend Lease (2014) “Noise Mitigation Program”. [Online] Available at: http://www.renewnyc.com/content/pdfs/130libertyNoiseMitigationProgramNotarizedMarch27_2009.pdf

Bentz, D., Ferraris, C. & Snyder, K. (2013) “Best Practices Guide for High-Volume Fly Ash Concretes: Assuring Properties and Performance”, NIST (National Institute of Standards and Technology), Department of Commerce, Technical Note 1812.


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Doka, G., (2003). Building Material Disposal, Dubendorf: Swiss Centre for Life Cycle Inventories.

Doka, G., (2003). Life Cycle Inventories of Waste Treatment Services, Dubendorf: Swiss Centre for Life Cycle Inventories.

Environmental Protection Agency (E.P.A.) (2009) “Potential for Reducing Greenhouse Gas Emissions in the Construction Sector”, 1200 Pennsylvania Ave, NW Washington, DC20460: U.S. Environmental Protection Agency.

Eastern research Group, inc. (2010) “Construction Fleet Inventory Guide”, Environmental Protection Agency.

Environmental Protection Agency (E.P.A.) (2003) “Estimating 2003 Building-related Construction and Demolition Materials Amounts” EPA.

Environmental Protection Agency (E.P.A.) (2003) “Tool for the Reduction and Assessment of Chemical and OtherEnvironmental Impacts”

(TRACI): User’s Guide and System Documentation, Cincinnati, Ohio, USA: National Risk Management Research Laboratory.

European Environment Agency (2010) “Material Resources and Waste” Luxembourg: Publications Office of the European Union.

Fischer, C. & Tojo, N., (2011) “Europe as a Recycling Society” Copenhagen: European Topic Centre on Sustainable Consumption an.

Hammond, G. & Jones, C. (2008), “Inventory of Carbon and Energy (ICE) Version 1.6a”, Claverton Down: University of Bath.Hammond, G. & Jones, C. (2011), “Inventory of Carbon and Energy (ICE) Version 2.0”, Claverton Down: University of Bath.Haney, J. H. (2011) “Environmental Emissions and Energy use from the Structural Steel erection process: a case study”. Fort Collins (Colorado ): Colorado State University, Department of Construction Management.

Ko, J., (2010) “Report 006: Carbon: Reducing the footprint of the construction process. An Action plan to reduce carbon emission[Online] Available at: http://www.strategicforum.org.uk/pdf/06carbonreducingfootprint.pdf [Accessed april 2015].

Stroetmann, R. (2011) “High strength steel for improvement of sustainability” Budapers, Eurosteel.

Urban Development Working Group (2005) “Waste Management in China: Issues and Recommendations”, East Asia Infrastructure Department World Bank.

USGBC (2009) “U.S. Green Building Council”

Worldsteel Association (2011) “Life Cycle assessment methodology report” Worldsteel Association, Brussels, Belgium

WoldSteel (2014) “Steel Statical Yearbook” 2014, Brussels

Zamagni, A. et al., (2008) “Critical review of the current research Ne-eds and Limitations Related to ISO-LCA Practice”, Project no.037075, Project acronym: CALCAS, Co-ordination Action for innovation in Life-Cycle Analysis for Sustainability.

Theses:

Sharp, G. S. & Buchanan, A. (2003) “Earthquake damage to passive fire protection systems in tall buildings and its impact on fire safety”, final year project submitted for the degree of Bachelor of Engineering, University of Canterbury: Christchurh, New Zealand

Treloar, G. J. (1998) “A Comprehensive Embodied Energy Analysis Framework” (PhD. Thesis). Victoria: Deakin University.


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Board of TrusteesChairman: David Malott, Kohn Pedersen Fox, USAVice-Chairman: Timothy Johnson, NBBJ, USAExecutive Director: Antony Wood, CTBUH / Illinois

Institute of Technology, USA / Tongji University, ChinaSecretary: Craig Gibbons, Arup, AustraliaTreasurer: Steve Watts, Alinea Consulting LLP, UKTrustee: Joseph Chou, Taipei Financial Center

Corporation, Taiwan Trustee: Mounib Hammoud, Jeddah Economic

Company, Saudi ArabiaTrustee: Dennis Poon, Thornton Tomasetti, USATrustee: Kam-Chuen (Vincent) Tse, Parsons Brinckerhoff,

Hong Kong

China Office BoardMurilo Bonilha, United Technologies Research Center,

ShanghaiJianping Gu, Shanghai Tower Construction &

Development, ShanghaiEric Lee, JLL, Hong KongDavid Malott, Kohn Pedersen Fox, New York, USAWai Ming Tsang, Ping An Real Estate, ShenzhenAntony Wood, CTBUH / Illinois Institute of Technology,

USA / Tongji University, ChinaChangfu Wu, Tongji University, ShanghaiJunjie Zhang, ECADI, ShanghaiKui Zhuang, CCDI, Shanghai

Staff / Contributors Executive Director: Antony WoodAssociate Director: Steven HenryOperations Manager: Patti ThurmondChina Office Director: Daniel SafarikResearch Manager: Dario TrabuccoLeader Coordinator / Events Manager: Jessica RinkelMembership Coordinator: Carissa DevereuxDigital Platforms Manager: Son DangProduction Associate: Marty CarverStaff Writer / Media Associate: Jason GabelStaff Writer / Communications Coordinator:

Alannah SharryStaff Writer / Media Assistant: Benjamin Mandel Website Content Editor: Aric AustermannProduction Associate: Kristen DobbinsEvents Assistant: Chuck ThielResearch Assistant / China Operations: Peng DuSkyscraper Database Editor: Marshall GeromettaSkyscraper Database Assistant: Will MirandaPublications Associate: Tansri MulianiGeneral Counsel: Matt RossettiSpecial Media Correspondent: Chris Bentley

Advisory GroupChair: Peter Weismantle, Adrian Smith + Gordon Gill

Architecture, USAAhmad K. Abdelrazaq, Samsung Corporation, KoreaDonald Davies, Magnusson Klemencic, USAJohannes de Jong, KONE Industrial Ltd., Finland

Jean-Claude Gerardy, ArcelorMittal, LuxembourgFaudziah Ibrahim, KLCC, MalaysiaAbdo Kardous, Hill International, ChinaJames Parakh, City of Toronto, CanadaMic Patterson, Enclos, USAGlen Pederick, Waterman International, AustraliaRobert Pratt, Tishman Speyer Properties, ChinaMark P. Sarkisian, Skidmore, Owings & Merrill LLP, USA

Working Group Co-ChairsBIM: Stuart BullDemolition: Dario TrabuccoFaçade Access: Lance McMasters, Kevin Thompson

& Peter Weismantle High Performance Façades: Christopher Drew

& Mikkel KraghLegal Aspects of Tall Buildings: Victor Madeira Filho

& Arthur WellingtonPerformance Based Seismic Design: Ron Klemencic

& John ViiseSecurity: Sean Ahrens & Caroline FieldSustainable Design: Antony WoodTall Timber: Carsten Hein & Volker Schmid

Committee ChairsUrban Habitat / Urban Design: James Parakh, City of

Toronto Planning Department, CanadaExpert Peer Review Committee: Antony Wood, CTBUH

/ Illinois Institute of Technology, USA / Tongji University, China

Height & Data: Peter Weismantle, Adrian Smith + Gordon Gill Architecture, USA

Awards: Mun Summ Wong, WOHA, SingaporeExpert Chinese Translation Committee: Nengjun Luo,

CITIC HEYE Investment CO., LTD., ChinaSkyscraper Center Editorial Board: Marshall

Gerometta, CTBUH, USAYoung Professionals: Sasha Zeljic, Gensler, USA

Regional RepresentativesAustralia: Bruce Wolfe, Conrad Gargett ArchitectureBelgium: Georges Binder, Buildings & Data S.A.Brazil: Antonio Macedo, EcoBuilding ConsultoriaCambodia: Michel Cassagnes, Archetype GroupCanada: Richard Witt, Quadrangle ArchitectsCosta Rica: Ronald Steinvorth, IECA InternationalDenmark: Julian Chen, Henning Larsen ArchitectsFinland: Santeri Suoranta, KONE Industrial, Ltd.France: Trino Beltran, Bouygues ConstructionGermany: Roland Bechmann, Werner Sobek Stuttgart

GmbH & Co.India: Girish Dravid, Sterling EngineeringIndonesia: Tiyok Prasetyoadi, PDW ArchitectsIsrael: Israel David, David EngineersItaly: Dario Trabucco, Iuav University of VeniceLebanon: Ramy El-Khoury, Rafik El-Khoury & Partners Malaysia: Matthew Gaal, Cox ArchitectureMongolia: Tony Mills, Archetype GroupMyanmar: Mark Petrovic, Archetype Group

Philippines: Felino A. Palafox Jr., Palafox AssociatesPoland: Ryszard M. Kowalczyk, University of Beira InteriorQatar: Shaukat Ali, KEO International ConsultantsRomania: Mihail Iancovici, Technical University of Civil

Engineering of Bucharest (UTCB)Russia: Elena A. Shuvalova, Lobby AgencySaudi Arabia: Bassam Al-Bassam, Rayadah Investment

Company, KSASingapore: Juneid Qureshi, Meinhardt (S) Pte Ltd.South Korea: Dr. Kwang Ryang Chung, Dongyang

Structural Engineers Co., LtdSpain: Iñigo Ortiz Diez de Tortosa, Ortiz Leon ArquitectosSri Lanka: Shiromal Fernando, Civil and Structural

Engineering Consultants (Pvt.) LtdTaiwan: Cathy Yang, Shanghai TowerTurkey: Can Karayel, Langan InternationalUAE: Dean McGrail, WSP Middle EastUnited Kingdom: Steve Watts, alinea consulting LLPVietnam: Phan Quang Minh, National University of Civil

Engineering

CTBUH Organizational Members (as of July 2015) http://membership.ctbuh.org

Supporting ContributorAECOMARCADISARK Studio West | Architect Reza KabulBeijing Fortune Lighting System Engineering Co., Ltd.BuroHappold Engineering CCDI Group CITIC HEYE Investment CO., LTD.Dow Corning CorporationEmaar PropertiesHudson YardsIllinois Institute of TechnologyJeddah Economic CompanyKingdom Real Estate DevelopmentKohn Pedersen Fox AssociatesKONE IndustrialLotte Engineering & ConstructionNational Engineering BureauOtis Elevator CompanyPace Development CorporationPing An Financial Centre Construction & DevelopmentRenaissance ConstructionSamsung C&T Corporation Schindler Top Range DivisionShanghai Tower Construction & DevelopmentShenzhen Parkland Real Estate Development Co., Ltd.Skidmore, Owings & MerrillSun Hung Kai Properties LimitedSuzhou Zhongnan Center DevelopmentTaipei Financial Center Corp.Turner Construction CompanyUnderwriters LaboratoriesWSP GroupZhongtian Urban Development Group

CTBUH Organizational Structure & Members

CTBUH Organizational Structure & Members | © Council on Tall Buildings and Urban Habitat

186

PatronArabtec ConstructionBlume FoundationBMT Fluid MechanicsBund Finance Center, TheCitic PacificDeSimone Consulting EngineersDurst Organization, TheEast China Architectural Design & Research InstituteEmpire State Realty TrustGenslerHoboken BrownstoneHOK, Inc.Hongkong Land ISA ArchitectureKLCC Property Holdings BerhadLanganMeinhardt Group InternationalNBBJPermasteelisa GroupRidleyShenzhen Overseas Chinese TownSL Green ManagementStudio LibeskindThornton TomasettiThyssenKrupp AGTishman SpeyerUnited Technologies CorporationWeidlinger AssociatesWordsearchZuhair Fayez Partnership

DonorAdrian Smith + Gordon Gill ArchitectureALT LimitedAmerican Institute of Steel ConstructionAon Fire Protection EngineeringArquitectonica InternationalArupAureconBALA EngineersBroad Sustainable Building Co.Brookfield MultiplexCBRE GroupCH2M HILLChina Architecture Design & Research GroupEnclos Corp.Fender KatsalidisFrasers PropertyHalfen United StatesHenning Larsen ArchitectsHill InternationalHyder ConsultingJensen HughesJORDAHLJotun Group, TheLaing O’RourkeLarsen & ToubroLeslie E. Robertson AssociatesMagnusson Klemencic AssociatesMAKEMcNamara / Salvia, Inc.Nishkian Menninger Consulting and Structural

EngineersOutokumpu PDW ArchitectsPei Cobb Freed & PartnersPickard Chilton ArchitectsPNB Merdeka Ventures Sdn. Berhad

PT Gistama IntisemestaQuadrangle ArchitectsRowan Williams Davies & IrwinSAMOO Architects and EngineersSaudi Binladin Group / ABC DivisionSchücoSeverud Associates Consulting EngineersShanghai Construction (Group) GeneralSHoP ArchitectsShum Yip Land Company LimitedSika Services AGSinar Mas Group - APP ChinaSolomon Cordwell BuenzStudio Gang ArchitectsSyska Hennessy GroupTAV ConstructionTerraconTime EquitiesTongji Architectural Design GroupWalsh Construction CompanyWalter P. Moore and AssociatesWATGWerner Voss + Partner

ContributorAedasAkzoNobelAlimak HekAlinea ConsultingAllford Hall Monaghan MorrisAltitude Façade Access ConsultingAlvine EngineeringAMSYSCOArcelorMittalarchitectsAllianceArchitectural Design & Research Institute of South

China University of TechnologyArchitectural Design & Research Institute of Tsinghua

UniversityArchitectusBarker Mohandas, LLCBates SmartBenson Industries Inc.bKL ArchitectureBonacci GroupBosa Properties Inc.Boundary Layer Wind Tunnel LaboratoryBouygues ConstructionBritish Land CompanyBroadway MalyanBrunkeberg SystemsCadillac FairviewCanary Wharf GroupCanderel ManagementCB EngineersCCLCermak Peterka PetersenChapman TaylorClark ConstructionConrad GargettContinental Automated Buildings AssociationCosentini AssociatesCS Group Construction Specialties CompanyCS Structural EngineeringCTSR PropertiesCubic ArchitectsDar Al-Handasah (Shair & Partners)Davy Sukamta & Partners Structural EngineersDCA Architects

DCI EngineersDeernsDIALOGDong Yang Structural Engineersdwp|sutersElenberg FraserEllisDon CorporationEuclid Chemical Company, TheEversendai Engineering QatarFaçade TectonicsFXFOWLE ArchitectsGERB Vibration Control Systems (USA/Germany)GGLOGlobal Wind Technology ServicesGlumacgmp • von Gerkan, Marg and Partners ArchitectsGoettsch PartnersGrace Construction ProductsGradient Wind Engineering Inc.Graziani + Corazza ArchitectsGuangzhou Design InstituteHariri Pontarini ArchitectsHarman Group, TheHathaway DinwiddieHeller Manus ArchitectsHiranandani GroupHousing and Development BoardHumphrey & Partners Architects, L.P.Hutchinson BuildersIrwinconsult Pty.Israeli Association of Construction and Infrastructure

EngineersJAHNJaros, Baum & BollesJDS Development GroupJiang Architects & EngineersJiangSu Golden Land Real Estate Development Co., LtdJLLJohn Portman & AssociatesKajima DesignKEO International ConsultantsKHP Konig und Heunisch PlanungsgesellschaftLangdon & Seah SingaporeLeMessurierLend LeaseLusail Real Estate Development CompanyM Moser AssociatesMaeda CorporationMori Building CompanyNabih Youssef & AssociatesNational Fire Protection AssociationNational Institute of Standards and TechnologyNIKKEN SEKKEI LTDNorman Disney & YoungOMAOmrania & AssociatesOrnamental Metal Institute of New YorkPalafox AssociatesPappageorge Haymes PartnersPei Partnership ArchitectsPerkins + WillPlus ArchitecturePomeroy StudioProject Planning and Management Pty LtdPT Ciputra PropertyR.G. Vanderweil EngineersRafik El-Khoury & PartnersRambollRAW Design

Supporting Contributors are those who contribute $10,000; Patrons: $6,000; Donors: $3,000; Contributors: $1,500; Participants: $750.

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Read Jones ChristoffersenRelated MidwestRMC InternationalRonald Lu & PartnersRoyal HaskoningDHVSanni, Ojo & PartnersSchöck United StatesSematic S.r.l.Shanghai Jiankun Information Technology Co., Ltd.Shimizu CorporationSilverEdge Systems SoftwareSilverstein PropertiesSoyak Construction and Trading Co.Stanley D. Lindsey & AssociatesSteel Institute of New YorkStein Ltd.SuperTEC (Super-Tall Building Design & Engineering Tech

Research Center)Surface DesignSWA GroupTakenaka CorporationTaylor Devices, Inc.Tekla CorporationTerrell GroupTFP FarrellsTMG PartnersTSNIIEP for Residential and Public BuildingsUniestateUniversity of Illinois at Urbana–ChampaignUrbanTorontoVetrocareWaterman AHW (Vic) Pty Ltd.Weischede, Herrmann und PartnersWerner Sobek GroupWilkinson Eyre ArchitectsWOHA ArchitectsWoods BagotWTM Engineers InternationalWZMH ArchitectsY. A. Yashar ArchitectsYKK AP Façade

ParticipantsThere are an additional 255 members of the Council at the Participant level. Please see online for the full member list. http://members.ctbuh.org

CTBUH Organizational Structure & Members | © Council on Tall Buildings and Urban Habitat

We now find ourselves in an age where “green design” is at the forefront of many tall building projects around the world, where it seems that every year brings new technologies and innovations that are touted as the be-all and end-all for a long-term sustainable future. But these solutions tend to only reduce the environmental impacts of a building during its operation phases, with the stages before and after this period often neglected. This is perhaps best illustrated by the fact that the world is currently constructing tall buildings in excess of 1,000 meters in height yet we have never demolished a building of even 200 meters in height through conventional means. Despite this reality, our cities continue to be filled with myriad skyscrapers, most of which are not given full considerations for their entire life cycle, or end-of-life.

Through the Life Cycle Assessment (LCA) methodology, we can gauge the environmental consequences of human actions by analyzing the flow of materials used in a building and trace the environmental impacts linked to each stage of its life cycle. When information from each stage is combined, a holistic picture of environmental impacts can be formed for a given product, one that acknowledges the various actions that are required to bring a single entity into existence through contemporary means.

This research identifies and compares the life cycle implications for the structural systems found in 60- and 120-story buildings. It is intended to inform the international community of professionals and researchers specializing in tall buildings on the life cycle environmental performance of the most common structural systems by providing the most accurate, up-to-date analysis on two key impact categories: Global Warming Potential (GWP) and Embodied Energy (EE). In doing this it presents interesting research results, and also lays down a methodology in this emerging field for others to follow.

Research Funded by:


life cycle assessment - arcelormittal sections:...

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