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CE5509CE5509Advanced Structural Steel DesignAdvanced Structural Steel Design

http://www.ivle.nus.edu.sg/default.asp

J Y Richard LiewProfessor

PhD, PE, MIStructE, CEng

National University of SingaporeDepartment of Civil EngineeringDepartment of Civil Engineering

Blk E1A, #05-131 Engineering Drive 2

Singapore 117576TEL: 65-6516 2154FAX: 65-6779 1635

E-MAIL: cveljy@nus.edu.sg

LEARNING OBJECTIVESThe module introduces students the advanced principles and concepts of structural steel design. The course enables students to acquire the knowledge and practical skills through the design projects, homework and problem-solving sessions. They should develop the capability of applying the knowledge to produce acceptable technical designs of steel and composite structures and their components for multi-storey construction. It also requires students to learn how to use d i id f bl l idesign aids for problem solving

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INTENDED OUTCOME After the completion of the module students should have learned the principles of limit states design in

relation to composite steel and concrete construction and to apply them to “real world” steel building

j tprojects. know and be aware of the requirements of modern

design codes for members (slabs, beams, columns and joints) and systems (frames and building) under serviceability and ultimate limit states

have the ability to design steel structural components using basic engineering tools and design aids.be able to produce acceptable technical design of be able to produce acceptable technical design of steel and composite structures for the construction of multi-storey buildings.

be aware of the contemporary issues of implementation structural building projects, particularly from the point of safety and cost effectiveness

MODE OF TEACHING AND LEARNING

Lectures: Key information inclusive of theories and methods made available in PowerPoint slides. A copy of all the slides can be downloaded from IVLE.R di C h i l t t h b Readings: Comprehensive lecture notes have been developed and made available. Reference list is also given for deeper reading and research.

Design Projects: Using analysis software and design tables for designing a multi-storey building. Each student will be two to four weeks to prepare structural scheme, propose options and design structural components and frames Homework assignmentscomponents and frames. Homework assignments will be designated to form part of the project. Professional level and report submission is expected.

Homeworks: assignment of readings, 8 homeworks and project works.

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ASSESSMENT Nature of CA and final assessment CA consists of project assignments, homework

assignments and quizzes Quizzes and examinations 2 quizzes and one final examination Break up of CA and final assessment Main exam = 60%

quiz and assignments = 40% Schedule assignments/quizzes/projects/papers Every three-hour lecture will be followed with a

homework assignment. For assignment, letter gradeshomework assignment. For assignment, letter grades will be assigned based on performance relative to classmates and performance in comparison to lecturer' expectation.

ReferencesReferences Compulsory reading

British Standard Institute, BS 5950-1:2000: Structural Use of Steelwork in Building Part 1 Code of Practice for Design – Rolled and Welded Sections, British Standard Institute, 2000.

British Standard Institute, BS 5950:1989: Structural Use of Steelwork in Building Part 3.1 Composite Beams, 1989.

BCS and SCI, Handbook of structural steelwork, 3rd Edition, jointly published by The British Constructional Steelwork Association and The Steel Construction Institute, UK, 2002.

8 Chapters course notes by Prof. J Y Richard Liew.

Supplementary Readings

Johnson, R.P., "Composite Structures of Steel and Concrete", Vol 1, Beams, Slabs, Column and Frames for Buildings, Blackwell Scientific Publications, 2nd ed., 1994.

Steelwork Design Guide to BS5950 Part 1: 2000 Vol 1 Section Properties The Steel Steelwork Design Guide to BS5950 Part 1: 2000. Vol. 1. Section Properties, The Steel Construction Institute, 2001.

Johnson R P and Anderson D, Designers’ guide to EN 1994-1-1 Eurocode 4: Design of composite steel and concrete structures, Part1.1: General rules and rules for buildings, Thomas Telford, 2004.

Nethercot, D A (Editor), Composite Construction, Spon Press, 2003.

Steel Construction Institute, Commentary on BS5950:Part 3: Section 3,1, Composite Structures, The Steel Construction Institute, UK, 1990

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ContentsChapter 1 : Introduction to Limit States DesignChapter 2: Member DesignCh t 3 M lti St F D iChapter 3: Multi-Storey Frame DesignChapter 4: Simply Supported Composite BeamsChapter 5: Continuous Composite Beams Chapter 6: Composite slab SystemsChapter 7: Composite ColumnsChapter 8: Steel-Concrete Composite Systems forChapter 8: Steel Concrete Composite Systems for

Multistorey Building Construction

Schedule 2010Schedule 2010Date Activity

10/08/2010 Lecture 1

17/08/2010 L t 2

Date Activity

12/10/2010 Lecture 917/08/2010 Lecture 2

24/08/2010 Lecture 3

31/08/2010 QUIZ

07/09/2010 Lecture 4

14/09/2010 Lecture 5

21/09/2010 Lecture 6

19/10/2010 Quiz

26/10/2010 Lecture 10

02/11/2010 Lecture 11

23/11/2010 Final Exam

(Recess week, but lecture is ON!)

28/09/2010 Lecture 7

05/10/2010 Lecture 8

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Lecture 1

Introduction to Steel DesignIntroduction to Steel Design

BS5950 BS5950 -- Part 1 : 2000Part 1 : 2000

St t l f t l k iStructural use of steelwork in building

Part 1: Code of practice for design:Part 1: Code of practice for design: rolled and welded sections

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ScopeScope

To be used for hot rolled sections, flats plates, hot finished and cold rolled structural hollow sections

Primarily for building structures and other structures not specifically coveredother structures not specifically covered by other standards

Contents of BS5950:Part1Contents of BS5950:Part1

1. General2 Li it St t D i2. Limit States Design3. Materials and Section Properties4. Design of Structural Members5. Continuous structures6 Connections6. Connections7. Loading tests

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Aims of Structural DesignAims of Structural Design

Economy, safety, fitness for purpose

Ease of transport, handling and erection

Future maintenance

End of life options

Limit States ConceptLimit States Concept

Consider the limit states beyond which the structure would become unfit for its intended use

Ultimate Limit State (ULS)

Serviceability Limit State (SLS)

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Design Strength of SteelDesign Strength of Steel

Number of results

275 2300 350 N/

Mean

95% Confidence limit

Strength of material

275 2300 350 N/mm

Specifying Steel GradeSpecifying Steel Grade

BS EN 10025 - S 275 Replace BS4360

A steel to the standard Minimum yield of

275 N/mm2

S for “structural”

275 N/mm

275355460E for “engineering”

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Standardised steel grade Standardised steel grade systemsystem

European standard numberFor hot finished hollow section H=hollow section

EN 10210 S 355 J2H

For hot-finished hollow section

S = Structural steelSuffix for test Temperature

H=hollow section

Grade designationbased on yieldStrength t<16mm

For Impact test

JRJ0J2K2

“Room”zero-200C-300C

s sY U

1.0 1.2py=

Steel grade Thickness less than or equal to (mm) Yield strengthYs (N/mm2)

Design Strength of SteelDesign Strength of Steel

S235 16 235

40 235

63 215

80 215

100 215

150 205

S275 16 275

40 265

63 25563 255

80 245

100 235

150 225

S355 16 355

40 345

63 335

80 325

100 315

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Other properties

For analysis the following properties of steel y g p pmay be used:

Modulus of elasticityE = 205,000 N/mm2Shear modulus G= E/[2(1+)]Poisson’s ratio = 0 3Poisson s ratio = 0.3Coefficient of linear thermal expansion = 12 x 10-6/°C

Partial Safety FactorsPartial Safety Factors

Used to provide adequate reliability

Cover variability of:– material strength - m

– loading - l

– structural performance - p

l p = f

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Limit States DesignLimit States Design

f F R f F R m

F is the service load

f is the load factor > 1

R is the resistanceR is the resistance

m is the resistance factor > 1

- Yield strength Ys for steels supplied in accordance with

Chinese standard GB50017 plates, hot rolled sections, hollow sections

Steel gradeThickness less than or equal to (mm)

Yield strengthYs (N/mm2)

Q235 16 215

40 20540 205

60 200

100 190

Q345 16 310

35 295

50 265

100 250

Q390 16 350

With material factor 1.1

Guarantee yield

35 335

50 315

100 295

Q420 16 380

35 360

50 340

100 325

strength from manufacturer is higher

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Ultimate Limit StatesUltimate Limit States

Strength

Stability

Fatigue

Brittle Fracture

Structural Integrityg y

Limit State of StrengthLimit State of Strength

Load combination 1: 1.4 x Dead load and 1.6 x imposed load

Load combination 2: 1.4 x Dead load and 1.4 x wind load

Load combination 3: 1.2 x Dead load, 1.2 x imposed load and

1.2 x wind load

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Limit State of StrengthLimit State of StrengthDead load, except as below f = 1.4Dead with wind and imposed loads f = 1.2p f

Dead load counteracting other loads f = 1.0Dead load restraining sliding, uplift etc. f = 1.0Imposed load f = 1.6Imposed load with wind load f = 1.2Wind load f = 1.4Wind load with imposed load = 1 2Wind load with imposed load f = 1.2Earth Pressure (BS8002) f = 1.2

Common Load CombinationsCommon Load Combinations

1. 1.4 Dead Load + 1.6 Imposed Load + NHL (0.5% total factored gravity load)

2. 1.4 Dead Load + 1.4 Wind Load* 3. 1.2 Dead Load + 1.2 Imposed Load

+1.2 Wind Load*

*Minimum wind load is 1% factored gravity load

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Example 1 Simply Supported BeamExample 1 Simply Supported Beam

Dead load = 20kN/mImposed load =25kN/m

The maximum reaction will be

Dead load = 20kN/m

5m

= (25 x 1.6 + 20 x 1.4) x 5 /2= 170kN

Dead load = 20kN/mImposed load =25kN/m

4m1m A B

100kN

Imposed Example 2

Consider (Dead load + imposed load)Taking moments about BThe maximum reaction at A = (25 x 5 x 2.5 x 1.6 + 20 x 5 x 2.5 x 1.4 + 100x5x1.6)/4

= 412.5kNm

The corresponding reaction at B = (25 x 5 x 1.6 + 20 x 5 x 1.4 +100x1.6) - 412.5= 87.5kN87.5kN

Max RB is found by taking moments about A and using the dead load only to restrain the upliftwith a reduced load factor of 1.0 on the span AB.

25 x 1 x 0.5 x1.6 + 20 x 1 x 0.5 x 1.4 + 100 x 1 x 1.6 -20 x 4 x 2 x 1.0 +4 xRB =0RB= -8.5kN

1.4DL + 1.6IL 1.0DL

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Example 3 Gantry StructureExample 3 Gantry Structure

L d4m

Loads Dead = 3kNImposed (people) =3.5kN

S/w of each leg = 2kNWind (with people) = 5kN

Wind

7m

Wind (no people) = 4kNA B

Gantry StructureGantry Structure

4m

7m

Load combination 11.4 Dead Load + 1.6 Imposed Load

1.4(3+2+2) + 1.6(3.5) = 15.4kNA B

Reaction at A (RA)=15.4/2= 7.7kN

Reaction at B (RB)=15.4/2= 7.7kN

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Gantry StructureGantry Structure

Load combination 2 or Dead Load +1 4Wind load

Wind

4m

7m

or Dead Load +1.4Wind loadTake moments about B:Dead load restraining uplift DL = 1.0

RAx4- (1.0x2x4) – (1.0x3x2)+1.4x4x7 =0Thus RA= -6.3kN (uplift)

A B

Take moments about A:Dead load not restraining uplift DL = 1.4

(1.4x2x4) +(1.4x3.5x2) + (1.4x4x7) – RB x 4 = 0Thus RB = 15.05kN

Gantry StructureGantry Structure

Load combination 3

Wind

4m

7m

A B

Dl Dead Load +1.2Imposed Load +1.2Wind loadTake moments about B:

Dead load restraining uplift DL = 1.0RAx4 - (1.0x2x4) - (1.0x3x2) - (1.2x3.5x2) +

(1.2x5x7) =0 Thus RA= -4.9kN (uplift)T k t b t ATake moments about A:Dead load not restraining uplift DL = 1.2

(1.2x2x4) + (1.2x3x2) +(1.2x3.5x2) + (1.2x5x7) – RB x 4 = 0 Thus RB = 16.8kN

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SummarySummary

RA(kN) RB(kN)Load Comb. 1 7.7 7.7Load Comb. 2 -6.3 15.1Load Comb. 3 -4.9 16.8

D i i f 16 8 kNDesign compression force = 16.8 kNDesign tension force = -6.3 kN

Serviceability Limit StatesServiceability Limit States

o Deflection

o Vibration and oscillation

o Durability

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Serviceability Limit StatesServiceability Limit StatesDeflection Limit

Internal beam < Span/200 to Span /360 or 40mmEdge beam < Span/300 to Span / 500 or 20mm

D ift R i tDrift RequirementsInterstory and overall deflection for wind with 50 years

return period or notional loads < H/300 to H/600

Comfort CriteriaTop floor acceleration < 1.5%g with 10 year return period

of service windFloor vibration > 4 cycles/second(including interaction between primary and secondary

beams)See Table 8 of BS5950:Part 1

Load TestLoad TestPurpose of testing

a) the design or construction is not entirely in accordance with BS 5950;

b) the capacity of an existing structure or component is in doubt;

c) appropriate analytical or design procedures are not available for designing the particular component or structure by calculation alone;

d) th d i l d i it f td) the design load carrying capacity of a component or structure is to be established from a knowledge of its ultimate capacity;

e) it is intended to construct a number of similar structures on the basis of prototype testing.

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STEEL COSTCementitious fire spray = $200 - $280 /tonSand blasting & Priming = $120/ton2 coat paint = $150 /ton ($75/ton per coat)

Material: I or H section = $1000-1200/tonSHS = $1500-2000/ton

Fabrication: I or H section = $580 $750/tonFabrication: I or H section = $580-$750/tonSHS = $600-$1000/ton

Erection & Installation = $300-$600/ton

Fabrication I ll iMaterial

STEEL COST (2007)

T t l St l C t I H S ti $4000 $5000

Fabrication

(3o%)

Installation(20%)

Material(30% - 50%)

Total Steel Cost: I or H Section = $4000 - $5000SHS = $5000 - $6000

Per ton

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How to Reduce Cost?1 Fabrication & Installation

• Simple connection• Quality welding should be done at the

factory & bolting is preferred at the site• Avoid excessive weld - fillet weld is

cheaper than butt weld and easier to inspectinspect

• Consider installation sequence in design• Design for Simple construction rather

than continuous construction

How to Reduce Cost?

2 Material Economy• Use material sparingly and only when

necessary• High strength & lightweight steel?• Cost per ton for SHS is two times of I- or

H-Section

y

H Section• Be reasonable in design!

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• Consider an integrated system i e

3 BuildabilityHow to Reduce Cost?

Consider an integrated system, i.e., mechanical services, superstructure and foundation

• Use high strength lightweight design to reduce load on foundation Use fast track construction for early• Use fast track construction for early return of investment

• Use composite design to enhance strength and stiffness as well as for fire protection.

Singapore International Convention and Exhibition CentreSingapore International Convention and Exhibition Centre

5 Levels173m x 144m173m x 144m

3,400 tons roofJack up using 10

towers

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Keppel DistriparkKeppel Distripark

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Conclusion• Steel is buildable compared to precast

constructionconstruction• Cost effective and material can be

recycled.• Environmental Friendly • Light, Dry and Fast Construction

Aesthetic• Aesthetic• R&D and new design codes to enhance

capability and buildability

QuestionsQuestions What are ultimate limit states (ULS)? What will

happen when they are violated?ULS = strength, stability, overturning, fatigue, fracture.ULS strength, stability, overturning, fatigue, fracture. The structure may collapse.

What are serviceability limit states (SLS)? What will happen when they are exceeded?SLS = deflection, vibration, durability etc.Cause discomfort and minor cracks

How does factor of safety used in ULS design and SLS design?SLS design?Apply factor of safety to ULS designUse service loads for SLS design

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Reading Reading assignmentsassignmentsassignmentsassignments

BS 5950:Part 1 Code:Clauses 2.1, 2.4 & 2.5

Reference : Chapter 1