l1_fundamentals of composite construction_v2

CIV4202 COMPOSITE STEEL AND CONCRETE CONSTRUCTION

HOUSE KEEPING

§ Registration;

§ Mole site;

§ Use your phone as a clicker (ResponseWare);

Have you used clicker before?

A.  Yes

B.  No

AGENDA FOR PART 1 OF THIS LECTURE

§  Lectures + Design Exercise Classes – will be mixed;

§ A few ‘ground rules’;

§ Who I am and what I have been up to;

§ What we will cover in CIV4202 and learning outcomes;

§  Format of the Group Design Project;

§ Useful references & sources of information.

GROUND RULES

§  I’m not the authority here;

§  Do ask questions - stop me anytime;

§  Slow me down if I’m too fast.

ABOUT ME

§  Dr. Shan-Shan Huang

BEng, MSc, PhD

§  Lecturer in Structural Engineering

§  BEng from Beijing

§  MSc, PhD & Post-Doc from Sheffield

§  Contactable at [email protected]

VISITING LECTURERS

Dr. Lee Leston-Jones BEng, PhD, CEng, MIStructE

§  Director of Ramboll’s Manchester office

Dr. Georgeta Simona Peet BEng, PhD, CEng, MICE

§  Associate in Ramboll’s Manchester office

CIV4202 - LEARNING OUTCOMES

§  Demonstrate an understanding of fundamental behaviour of composite structures of steel and concrete under loading conditions;

§  Demonstrate an understanding of design principles of composite beams, columns and slabs under service and ultimate loads;

§  Design composite structures following guidance contained in the Eurocodes;

§  Develop a feel for the behaviour of the structure that is often missing when design is based solely by using codes of practice.

CALENDAR

Week Day 9(9.50 10(10.50 11(11.50 12(12.50 1(1.50 2(2.50 3(3.50 4(4.50

Mon

Wed

Fri

Mon

Wed

Fri

Wed

Fri

Wed

Fri

Tue

Wed

Fri

Week95 GDP9Feedback9Session

GDP9Feedback9Session

Submission9of9GDP9via9MOLE9@99am

Fundamentals9of9Composite9Construction9

Principles9of9Shear9Connection

Composite9Slab9Design9





Week93

Week94

Week91

CIV42029(9Composite9Steel9&9Concrete9Construction

Week92

Composite9Beam9Design9

Composite9Column9Design9

Case9Studies9+9Intro9to9GDP

ALLOCATION OF CREDITS FOR CIV4202

Group Design Project (100%)

USEFUL REFERENCES - EUROCODES

BS EN 1990 Eurocode 0: Basis of structural design BS EN 1991-1-1 Eurocode 1: Actions on structures – Part 1-1: General actions

– Densities, self-weight and imposed loads

BS EN 1991-1-2 Eurocode 1: Actions on structures – Part 1-2: General actions – Actions on structures exposed to fire

BS EN 1992-1-1 Eurocode 2: Design of concrete structures – Part 1-1: General – Common rules for building and civil engineering structures

BS EN 1992-1-2 Eurocode 2: Design of concrete structures – Part 1-2: General – Structural fire design

BS EN 1993-1-1 Eurocode 3: Design of steel structures – Part 1-1: General rules and rules for buildings

BS EN 1993-1-2 Eurocode 3: Design of steel structures – Part 1-2: General – Structural fire design

BS EN 1994-1-1 Eurocode 4: Design of composite steel and concrete structures – Part 1-1: General – Common rules and rules for buildings

BS EN 1994-1-2 Eurocode 4: Design of composite steel and concrete structures – Part 1-2: General – Structural fire design

JOHNSON, R P (2004)

COMPOSITE STRUCTURES OF STEEL AND CONCRETE

Blackwell Publishing. ISBN: 1405100354

§  Available online via StarPlus

JOHNSON, R P AND ANDERSON D (2004) DESIGNERS’ GUIDE TO EN 1994-1-1, EUROCODE 4: DESIGN OF COMPOSITE STEEL AND CONCRETE STRUCTURES

Thomas Telford. ISBN: 0727730118

§  Available online via StarPlus

THE FUNDAMENTALS OF COMPOSITE BEHAVIOUR

AGENDA FOR PART 2 OF THIS LECTURE

§  Fundamentals of composite design;

§  The basics of limit state design;

§ An introduction to Eurocode 4;

§ Methods of analysis and design.

LEARNING OUTCOMES FOR THIS LECTURE

§  Develop a knowledge of common forms of composite construction and key benefits over non-composite construction;

§  Develop an understanding of the basic mechanics of composite behaviour;

§  Develop and appreciation of limit state design and material properties in relation to composite design to the Eurocodes;

§  Develop a understanding of principle methods of analysis and design.

COMPOSITE FLOORS & BEAMS

COMPOSITE COLUMNS

Composite construction has a very high market

share (e.g. for high-rise buildings

in the UK) Why?

Composite construction normally uses steel and

concrete together Why?

WHY IS COMPOSITE SO POPULAR?

WHY IS COMPOSITE SO POPULAR?

Complimentary materials:

§ Concrete efficient in compression;

§ Steel efficient in tension;

§  Fire and corrosion protection;

§ Steel enhances ductility.

Benefits include:

§  Economic;

§  Functional;

§ Service and flexibility;

§ Assembly.

§  In (a) both parts behave separately and move freely relative to each other at the interface;

§  In (b) both parts are constrained to act together, and plain sections remain plain (no longitudinal slip);

§  Can you guess how strong and how stiff compared Case (b) with Case (a)?

BASIC MECHANICS OF COMPOSITE DESIGN


2 TIMES STONGER!


4 TIMES STIFFER!

STRUCTURAL EFFICIENCY

§ High strength

710 520 560

IPE400 IPE550 HE360B

Load resistance 100% 100% 100%

Steel weight 100% 160% 215%

Height 100% 130% 95%

Stiffness 100 – 70% 70% 45%

§  High stiffness §  Good ductility

Composite Non -Composite

Now consider this composite sec:on, where should a good design a=empt to locate the neutral axis of bending?

A.  In the concrete slab

B.  In the steel beam

C.  At the concrete/steel interface

D.  Not sure...

Plas:c design is now commonplace when dealing with composite construc:on. What is(are) its benefit(s) over elas:c design?

A.  Easier to use

B.  Leads to higher resistances

C.  Both

DESIGN PHILOSOPHY

Have you done CIV2200 Structural Engineering Design & Appraisal & CIV321 Mul4-‐Storey Building Design?

A.  Yes

B.  No

DESIGN REQUIREMENT

Should we eliminate this overlap?

A.  Yes, to prevent structural failure

B.  No

C.  Depends on the situaAon

§  Limit state design applies partial safety factors, both to the loads and to the material strengths;

§  Limit state philosophy forms the basis of the design methods in most modern codes of practice for structural design.

LIMIT STATE DESIGN

§  Ultimate limit states: strength, stability;

§  Serviceability limit states: deflection, cracking, durability.

§  Excessive vibration – which may cause discomfort or alarm as well as damage;

§  Fatigue – must be considered if cyclic loading is likely;

§  Fire resistance – this must be considered in terms of resistance to collapse, flame penetration and heat transfer;

§  Special circumstances – such as earthquake resistance, must be taken into account.

LIMIT STATES

For reinforced concrete beams, which limit state(s) usually governs(govern) the design?

A.  ulAmate limit states of bending and shear

B.  serviceability limit state of deflecAon and cracking

C.  Don't know...

Which limit state(s) is(are) normally more cri:cal in the design of concrete slabs?

A.  ulAmate limit states of bending and shear

B.  serviceability limit state of deflecAon

C.  Hmmm...

§  The following factors should be considered when selecting a suitable value for :-

§  The strength of the material in an actual member;

§  The severity of the limit state being considered.

PARTIAL SAFETY FACTORS FOR MATERIALS, γM

)()(

M

k

safetyoffactorpartialfstrengthsticcharacteristrengthDesignγ

=

Mγ

S:ll remember what characteris:c strength fk is about?

A.  Yes : )

B.  Hmmm...more or less

C.  Not at all : (

Characteris:c strength fk = mean strength fm -‐ 1.64s. What is '1.64s' about? It is: A.  to consider the deviaAon of test

results

B.  to ensure that the majority of material will have strengths higher than fk

C.  empirical and means nothing

Characteris:c strength fk = mean strength fm -‐ 1.64s.

'1.64s' is to ensure that the majority of material will have strengths higher than fk.

What does 'majority' mean here?

A.  75%

B.  85%

C.  95%

§  Recommended values of for strengths of material and for resistances (from Eurocodes ):-

PARTIAL SAFETY FACTORS FOR MATERIALS, γM

Mγ

Why does concrete have a higher par:al safety factor than steel?

A.  Concrete has lower strength than steel

B.  Concrete strength can be affected by many factors

C.  Concrete is a more consistent material than steel

D.  Not sure...

Why do ULS have higher par:al safety factors than SLS?

A.  ULS are more criAcal (governing the design) than SLS

B.  ULS are more severe (in terms of the consequence of failure) than SLS

C.  Don't know...

§  The loads acting on a structure are divided into four basic types:

§  Permanent (dead) loads, Gk gk;

§  Variable (live) imposed loads, Qk qk;

§  Wind loads;

§  Accidental Loads.

DESIGN LOADS ACTING ON STRUCTURES

When designing a structural element, do dead loads gk include the self-‐weight of the element itself?

A.  Yes

B.  No

C.  Not sure...

§  The value of should also take into account:-

§  The importance of the limit state under consideration;

§  Different type of loading;

§  The probability of particular load combinations.

PARTIAL SAFETY FACTORS FOR LOADS, γf

fγ

Design load = characteristic load× partial safety factor (γ f )

§  Values of and for persistent design situations (from Eurocodes ):

PARTIAL SAFETY FACTORS FOR LOADS, γf

Gγ Qγ

kk QGloadDesign 5.135.1 +=§  ULS –

kk QGloadDesign 0.10.1 +=§  SLS -

§  The load combination should be arranged to produce the worst possible effect on the structure in terms of bending moments, shear forces and deflections.

LOAD COMBINATIONS / PATTERN LOADING

Why is the par:al safety factor for variable unfavourable loads at ULS the highest?

A.  Because the variable unfavourable loads are usually the most criAcal

B.  For the uncertainty of variable loads

C.  Don't know

AN INTRODUCTION TO EUROCODE 4

§  The publication of structural Eurocodes is complete;

§  They replaced existing British Standards which were withdrawn on 31 March 2010;

§  Over 30% of the construction sector are already using Eurocodes by June 2009;

§  In order to allow for the variety of climatic and other factors across the EU, the Member States may produce their own National Annexes.

UPDATES ON THE EUROCODES

§  Eurocode 4 applies to the design of composite structures and members for buildings and civil engineering works;

§  Eurocode 4 is based on limit state principles and comes in several parts as follows:

§  Part 1-1: General rules and rules for buildings Replaces BS 5950-3.1 and BS 5950-4

§  Part 1-2: Structural fire design

Replaces BS 5950-8

§  Part 2: Bridges Replaces BS 5400-5

§  A UK National Annex (NA to BS EN 1994-1-1:2004) to

Eurocode 4 Part 1-1 is available.

EUROCODE 4

METHODS OF ANALYSIS AND DESIGN

§  The principal methods of analysis used for composite members and frames are:

§  The elementary elastic theory of bending;

§  The simple plastic theory in which the whole cross-section of a member is assumed to be yield, in either tension or compression.


§  Both theories are used for composite members, the differences being as follows:

§  Concrete in tension is usually neglected in elastic theory, and always neglected in plastic theory;

§  In the elastic theory, concrete in compression is ‘transformed’ into an equivalent area of steel by dividing its breadth by the modular ratio Ea / Ec;

§  In the plastic theory, the design ‘yield stress’ of concrete in compression is taken as 0.85 fcd , where fcd = fck / γc. Transformed sections are not used.


Composite beams incorporating composite deck slabs. (a) Deck perpendicular to secondary beam.

(b) Deck parallel to primary beam.

Plastic analysis of composite section under positive moment. (a) PNA in slab, (b) PNA in steel flange, (c) PNA in steel web.


How would you lay a one-‐way composite slab?

A.  Ribs parallel to the short span

B.  Ribs parallel to the long span

C.  Either way can do

LEARNING OUTCOMES FOR THIS LECTURE

§  Develop a knowledge of common forms of composite construction and key benefits over non-composite construction;

§  Develop an understanding of the basic mechanics of composite behaviour;

§  Develop and appreciation of limit state design and material properties in relation to composite design to the Eurocodes;

§  Develop a understanding of principle methods of analysis and design.

How do you feel about the use of clickers/phones?

A.  Like

B.  Dislike

C.  Neutral

How did you find about the clicker ques:ons?

A.  Useful -‐ helped with revising the design philosophies

B.  Useless -‐ too easy & waster of Ame

C.  Neutral

THANK YOU...

l1_fundamentals of composite construction_v2

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