Naveed Anwar, AIT Solutions
Progression of Structural Design Approaches
Design of Tall Buildings: Trends and Advancements for Structural Performance
Bangkok-Thailand
November 7-11, 2016
Naveed Anwar, PhD
Naveed Anwar, AIT Solutions 2
Trends and Advancements in for Structural Performance
Why this Seminar and Workshop ?
And why is this topic imporant
Demand and Complexity is Increasing
Naveed Anwar, AIT Solutions
Percentage of Urbanized World
4
Naveed Anwar, AIT Solutions
World’s Population Urban-to-Rural Ratio
5
(www.un.org)
Naveed Anwar, AIT Solutions
Visions
6
Japan, 4000m Sky Mile Tower, 1700 m JapanDubai City Tower, 2400 m One Dubai Tower, 1008 m
Naveed Anwar, AIT Solutions
The Reality
7
Naveed Anwar, AIT Solutions 8
Source: CTBU Report, 2015
Naveed Anwar, AIT Solutions 9
Source: CTBU Report, 2015
Naveed Anwar, AIT Solutions 10
Source: CTBU Report, 2015
Naveed Anwar, AIT Solutions 11
Source: CTBU Report, 2015
Naveed Anwar, AIT Solutions 12
The Twisting Turning Towers Trend
Source: CTBU Report, 2015
Naveed Anwar, AIT Solutions 13
Naveed Anwar, AIT Solutions
Source: CTBU Report, 2015
Tall Buildings in Bangkok(> 200m)
Naveed Anwar, AIT Solutions 15
Source: CTBU Report, 2015
Naveed Anwar, AIT Solutions
Buildings and Structures are expected to be
• Safe
• Secure
• Serviceable
• Reliable
• The contents of the structures are often much more valuable than structure itself
• The loss of service/operations/business is a often larger than repair costs
• Protective
• Friendly
• Sustainable
• Affordable
Naveed Anwar, AIT Solutions 17
Needs Changes in Structural Design Approaches
Naveed Anwar, AIT Solutions18
Is my Structure safe?
(What level of Richter earthquake my structure sustain? Or what tornado level can it withstand,
or is it safe for explosions orHow long can it withstand the fire?)
Naveed Anwar, AIT Solutions 19
How long do we have
before the building will
collapse in this fire?
- Asks the Fire Chief from the structural
engineer
1974
Naveed Anwar, AIT Solutions
The Towering Inferno (1974)
20
https://www.youtube.com/watch?v=FagbC09BO2o
Naveed Anwar, AIT Solutions
Evolution of our Understanding of Structures
Limits on the allowable stresses to achieve in-direct FOS
Explicit consideration of partial FOS.
Formulation of limit state design principles.
Formulation of ultimate strength.
The recognition of the difference between brittle and ductile failure.
The introduction of capacity based design approaches.
Performance based design and more explicit linkage between demand and performance.
Risk integrated based design, and a more and holistic approach towards consequence based engineering.
Naveed Anwar, AIT Solutions
Design Approaches
Intuitive Design
Code Based Design
Performance Based Design
Consequences and Risk Based Design
Resilience Based Design
Naveed Anwar, AIT Solutions
Design Approaches
Intuitive Design
Code Based Design
Performance Based Design
Consequences and Risk Based Design
Resilience Based Design
Naveed Anwar, AIT Solutions
Development of Formal Buildings Codes
24
“Rebuilding of London
Act” after the “Great Fire of
London” in 1666 AD.
In 1680 AD, “The Laws of
the Indies” Spani
sh Crown
London Building Act of
1844.
In USA, the City
of Baltimorefirst building code in 1859.
In 1904, a Handbook of the Baltimore
City
In 1908 , a formal
building code was
drafted and adopted.
The International
Building Code (IBC) by (ICC).
European Union,
the Eurocodes.
Naveed Anwar, AIT Solutions
The Modern Codes – With “intent” to make buildings safe for public
25
(ACI 318 – 11)
Extremely Detailed prescriptions and
equations using seemingly arbitrary, rounded limits with
implicit meaning
(IS 456-2000)
Naveed Anwar, AIT Solutions
The General Code Families
26
UBC, IBC
ACI, PCI, CRSI, ASCE, AISI,
AASHTO
British, CP and BS
Euro-codesChina, USSR,
Japan
Naveed Anwar, AIT Solutions
Are All Buildings Codes Correct ?
• If they differ, can all of them be correct ?
• Did we inform the structures to follow which code when earthquake or hurricane
strikes ?
• Codes change every 3 or years, should we upgrade our structures every 3 or 5
years to conform ?
• Codes intend for “Life Safety”, not damage limits or cost implications
27
Naveed Anwar, AIT Solutions
Prescriptive Codes – A Shelter
• Public:
• Is my structure safe ?
• Will it be damaged, how much, how long to repair
• Structural Engineer:
•Not sure, but I did follow the “Code”
As long as engineers follow the code, they can be
sheltered by its provisions
28
Naveed Anwar, AIT Solutions
Shortcomings of Code Based Design for Tall Buildings
• Traditional codes govern design of general, normal buildings
Over 95% buildings are covered, which are less than about 50 m
• Not specifically developed for tall buildings > 50 m tall
• Prescriptive in nature, no explicit check on outcome
• Permit a limited number of structural systems
• Do not include framing systems appropriate for high-rise
• Based on elastic methods of analysis
• Enforce uniform detailing rules on all members
• Enforce unreasonable demand distribution rules
• Do not take advantage of recent computing tools
Naveed Anwar, AIT Solutions30
Naveed Anwar, AIT Solutions
The First Building Code: Code of Hammurabi (1792 BC to 1750 BC)
31
Clause 229:
If a builder builds a house for someone, and does not construct it
properly, and the house which he built falls in and kills its owner,
then that builder shall be put to death.
Naveed Anwar, AIT Solutions
Design Approaches
Code Based Design
Performance Based Design
Consequences and Risk Based Design
Resilience Based Design
Naveed Anwar, AIT Solutions
Performance Based Design (PBD)
• An approach in which structural design criteria are expressed in terms of
achieving a set of performance objectives or levels.
• Ensures structures reaches specified demands level in both service and
strength design levels.
• Why it was needed?
• Traditional codes not suitable/adequate
• Explicit verification not specified or required in most codes
• Public does not care about the code, or theories or procedures, they care about
“safety” and ‘performance”
33
Naveed Anwar, AIT Solutions
Define Performance Levels
34
Based on FEMA 451 B
Naveed Anwar, AIT Solutions
Link the Hazard to Performance Levels
35
Structural Displacement
Lo
adin
g S
ever
ity
Resta
urant
Resta
urant
Resta
uran
t
Ha
zard
Vulnerability
Consequences
Naveed Anwar, AIT Solutions
Is this acceptable?Even though it satisfies CBD and PBD
Naveed Anwar, AIT Solutions
Design Approaches
Code Based Design
Performance Based Design
Consequence and Risk Based Design
Resilience Based Design
Naveed Anwar, AIT Solutions
Beyond PBD
• For public, the performance
criteria still does reduce the
effects of the events
• Insurance companies want to
have greater reliability of
assessment of risk and
damages
38
Naveed Anwar, AIT Solutions
Questions still un-answered
• What if the chance that performance level is not
achieved?
• What is the risk ?
• What are the consequences?
• What if the performance levels are not sufficient?
Code based was implicit, with not confirmation of response
PBD is explicit, can help to confirm the response and
performance level
Naveed Anwar, AIT Solutions
Why do we need to go Beyond PBD
• For public and society, the performance criteria still does reduce the effects of the events, but it can reduce the risk level
• The non structural damage is not acceptable in modern buildings
• The disruption and loss goes much beyond the building
• Insurance companies want to have greater reliability of assessment of risk and damages
Naveed Anwar, AIT Solutions
Consequence Based Engineering
• It is not enough to say “Cracking and non-structural damage is acceptable, as long as structure does
not collapse”
• A natural extension of the performance-based design approach
• Structural consequences > DDD (dollars, deaths and downtime) (Porter, 2003).
41
The trigger of an event is not important, the consequences of an event are
Naveed Anwar, AIT Solutions
Consequence Based Engineering
• “Structural consequence and non-structural effects”
determined entirely from the analysis of structural
member as well as overall system behavior.
• Proceeds through the analysis of expected system
consequences, irrespective of the event triggering
these consequences.
• Requires the structural members to be designed for
variable reliability levels, depending upon their
contribution in causing adverse system
consequences.
42
Naveed Anwar, AIT Solutions
Risk Based Design Process
Safety Studies (Probability and
Consequence Analysis)
Risk Quantification
Safety Critical Element
Design Accidental
Load
Structure Design
Naveed Anwar, AIT Solutions
Special Purposes Guidelines from USA
44
Applied Technology
Council (ATC)
Federal Emergency Management Agency
(FEMA) and
National Earthquake
Hazards Reduction Program (NEHRP)
PEER Guidelines
for Tall Buildings
Tall Buildings Initiatives
(TBI)
CTBUH Guidelines
Naveed Anwar, AIT Solutions
What Next: What is still missing
• Adequacy, Performance and Risk reduction of Structure alone is not
enough
• Structure serves a purpose in society, economy, community > Should be
integrated with other aspects
• A more holistic approach, beyond structural design needed
45
Naveed Anwar, AIT Solutions
Design Approaches
Code Based Design
Performance Based Design
Consequences and Risk Based Design
Resilience Based Design
Naveed Anwar, AIT Solutions
RESILIENCE
Economic
Social
Organizational
Technical
Resourcefulness
Redundancy
Rapiditty
Robustness
Lower
Consequences
Faster
Recovery
More Reliability
4 Dimensions of
Resilience
4 Properties of
Resilience
3 Results of Resilience
47
Naveed Anwar, AIT Solutions
Resilience Based Earthquake Design
• A holistic approach which seeks to identify all hazard-
induced risks (including those outside the building
envelope) and mitigate them using integrated multi-
disciplinary design and contingency planning to achieve
swift recovery objectives in the aftermath of a major
earthquake.
• The key principle in resilience-based design is to limit
expected damage to structural and architectural
components and egress systems (elevators, stairs, and
doors)
48
Economic Loses
Loss of Community and Culture
Loss of Quality of
Life
Go Beyond Life Safety
Naveed Anwar, AIT Solutions
Link Performance to other Indicators
49
Restaurant Restaurant
Resta
uran
t
Operational (O) Immediate Occupancy (IO) Life Safety (LS) Collapse Prevention (CP)
0 % Damage or Loss 99 %
Ref: FEMA 451 B
CasualtiesLowest Highest
Rehab Cost to Restore after eventLowest Highest
Retrofit Cost to Minimize ConsequencesHighest Lowest
Downtime for RehabLowest Highest
Impact on Sustainability of CommunityLowest Highets
Naveed Anwar, AIT Solutions
Green Buildings Resilient Buildings
50
Main authors : ArupSupported by USRC and many others
Naveed Anwar, AIT Solutions 51
ARUP
Tools: How to design efficiently?
Naveed Anwar, AIT Solutions
The Growing Computational Requirements
• Dynamic Analysis
• Nonlinear modelling
• Nonlinear Time History Analysis
• Progressive Collapse
• Staged construction analysis
• A new and major concern for structural safety
• Structure should not collapse completely if one or two elements are
“destroyed”
• Backup systems, alternate load paths, additional redundancy
Naveed Anwar, AIT Solutions
The Role of Computers and Software
54
• Initially, computers were used to
program the procedure we had
• Now, we develop procedures that
are suited for computing
Naveed Anwar, AIT Solutions
Design Approaches evolved to match computing revolution
55
Naveed Anwar, AIT Solutions
A Swing Towards the AI
• Rich Pictures
• Analytical Hierarchy Process (AHP)
• Artificial Neural Networks (ANN)
• Genetic Algorithms (GA)
• Expert Systems (ES)
• Fuzzy Logic
• Deep Thinking
• Big Data and Data Mining
56
Naveed Anwar, AIT Solutions
Mobile computing might change how we design
57
Naveed Anwar, AIT Solutions
Can we make it safe, sustainable and resilient?
58
Thank you