RSA_Singapore Dennis Lam 2013

8/13/2019 RSA_Singapore Dennis Lam 2013

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Design of Steel and CompositeStructures to Eurocode 4

Prof Denn is Lam


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Contents

Introduction

Shear connectionDesign of composite slabsDesign of composite beams

Design of composite columns


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Aims of the Eurocode Programme

To harmonise all the code of practices across the wholeEuropean communities.

To harmonise between different construction materialsand construction methods.

To achieve full consistency and compatibility in terms ofloading, safety factors, etc.

To eliminate technical obstacles to trade andharmonisation of technical specification.


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The Structural EurocodesEN1990, Eurocode 0: Basis of Structural Design

EN1991, Eurocode 1: Actions on structures

EN1992, Eurocode 2: Design of concrete structures

EN1993, Eurocode 3: Design of steel structures

EN1994, Eurocode 4: Design of composite steel and concrete structures

EN1995, Eurocode 5: Design of timber structures

EN1996, Eurocode 6: Design of masonry structuresEN1997, Eurocode 7: Geotechnical design

EN1998, Eurocode 8: Design of structures for earthquake resistance

EN1999, Eurocode 9: Design of aluminium structures


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The Structural EurocodesEN1990, Eurocode 0: Basis of Structural Design

EN1991, Eurocode 1: Actions on structures

EN1992, Eurocode 2: Design of concrete structures

EN1993, Eurocode 3: Design of steel structures

EN1994, Eurocode 4: Design of composite steel and concrete structures

EN1995, Eurocode 5: Design of timber structures

EN1996, Eurocode 6: Design of masonry structuresEN1997, Eurocode 7: Geotechnical design

EN1998, Eurocode 8: Design of structures for earthquake resistance

EN1999, Eurocode 9: Design of aluminium structures


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EN1994

Composite

Structures

EN1993

Steel

Structures

EN1991Actions

Dead Imposed Wind

EN1990

Basis of Design

EN1992

Concrete

Structures


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Differences from BS5950

Symbols

TerminologyAxes Classification of cross sections Materials properties Slenderness


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SYMBOLSBS5950 EN1993 BS5950 EN1993 BS5950 EN1993

D h S Wpl py fy

B b Ix Iy Pb LTfy

T tf

Iy Iz Pc fy

t tw H Iw r i

Z Wel J It


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TERMINOLOGY

BS5950 EN1993

Force, F

Capacity, Pc Design strength, py

Dead load Live load

Wind load

Action, NEd

Resistance, N,Rd Yield strength, fy

Permanent action Variable action

Another type ofvariable action


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CONVENTIONS FOR MEMBER AXES

Member Axes Symbol used in

BS5950 EN1993

Major axis

Minor axis/vertical

axis

Direction alongthe member Definitions:

x-x

y-y

z-z

y-y

z-z

x-x


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CLASSIFICATION OF CROSS SECTIONS

BS5950 EN1993

= (275/py) = (235/fy)

Plastic (Class 1)

Compact ( Class 2)Semi-compact (Class 3)

Slender (Class 4)

Class 1

Class 2Class 3

Class 4


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MATERIALS PROPERTIES

Properties BS5950 EN1993

Youngs Modulus

Shear Modulus

205000 N/mm2

79000 N/mm2

210000 N/mm2

81000 N/mm2


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Slenderness,


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Value of for the appropriate non-dimensional slenderness, should be

determined from:


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Shear Connection


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Shear connector capacity in composite beams


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LoadSlip Characteristics


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Modes of failure


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Shear failure of the headed stud


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Conical concrete failure


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Combined failure of concrete and stud


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BS59503.1


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Design Resistance of Headed Stud ShearConnectors in Solid Slabs


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EN1992-1-1 Table 3.1


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EN1992-1-1 Table 3.1


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Modulus of Elasticity of Concrete, Ecm

GPaf

E cm

cm

3.0

1022

fcm = fck + 8 MPa


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The modulus of elasticity of a concrete is controlled by the moduli of

elasticity of its components. Approximate values for the modulus of

elasticityEcm, secant value between c= 0 and 0,4fcm, for concreteswith quartzite aggregates, are given in Table 3.1. For limestone and

sandstone aggregates the value should be reduced by 10% and 30%

respectively. For basalt

aggregates the value should be increased by 20%.

Note: A Countrys National Annex may refer to non contradictory

complementary information.

Modulus of Elasticity of Concrete, Ecm


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Profiled steel sheeting transverse to the beams

nr is the number of shear connectors in one rib, but not > 2.


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Kt ,max:Upper Limit for Kt


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Design Resistance of Headed Stud ShearConnectors in Metal Deck Flooring


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Design Resistance of Headed Stud ShearConnectors in Metal Deck Flooring

solidRdtdeckingRd PKP ,,


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Composite slabs withMetal Deck flooring


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Composite slabs have been the most widely usedmethod of suspended floor construction for steelframed buildings.

The profile steel sheeting is very thin for economicreasons, usually between 0.9 to 1.2 mm, it has to begalvanised to resist corrosion and it is about0.04mm thick.

The modern profiles are usually Class 4, therefore,calculation of the resistance to bending is complexand involves iteration, therefore safe load tables forbending resistance are based on experimentaltesting.


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Design of composite

slabs


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Bending Resistance

dyppfc

fAN,,

plpfcRd xdNM 5.0,

bfNx cdfcpl 85.0/,


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Resistance to longitudinal shear

For profiled sheeting that relies on frictionalinterlock to transmit longitudinal shear, there isno satisfactory conceptual model.

The shear resistance is based on m-ktest.


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Graphical determination of m and kto EN1994


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Graphical determination of m and k

to EN1994

kbLmAbdV

s

p

vs

pRd


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Reduction line

0.5 1.0 1.5 2.0 2.5 3.0 3.50

0.01

0.05

0.03

0.04

0.02

0.07

0.06

1

mr

kr

A

B

Regression linecmss

E

fdB

V

cmvs

p

fLB

A

cur

ss

prsss fk

LB

AmdBV

25.1

Graphical determination of mr

and kr

to BS5950


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Composite beam withmetal deck flooring


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Moment Resistance, Mpl,Rd full interaction between structural steel, reinforcement, andconcrete.

the effective area of the structural steel member is stressedto its design yield strength fydin tension or compression.

the effective areas of longitudinal reinforcement in tensionand in compression are stressed to their design yield

strength fsdin tension or compression.

the effective area of concrete in compression resists astress of 0,85 fcdconstant over the whole depth between the

plastic neutral axis and the most compressed fibre of the

concrete, where fcd

is the design cylinder compressive

stren th of concrete.


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Tension Capacity of the Steel Section, Na:

Aa= cross section area of the steel section

fyd= design strength of the steel

M0 = material partial safety factor

0M

ydaa

fAN


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Compression Capacity of Concrete Flange, Nc ,f

beff= effective breadth of concrete

fck= design strength of the steel

c= partial safety factor for concrete

c

pseffckfc

hhbfN

)(85.0,


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Nc,f Na(P.N.A. in concrete flange)

Neutral axis depth, x

Take moments about the top of concrete flange

P.N.A

.

Na

Nc,f= Na

fy

hs- hp

ha

hp

x

psfc

a hhNNX

,

22,

xN

hhNM a

asaRdpl

22,

,ps

fc

aasaRdpl

hh

N

NhhNM


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Na> Nc,f (P.N.A. in steel)

(i) Na> Nc,f Na,w (P.N.A. in steel flange)(ii) Nc,f < Na,w (P.N.A. in steel web)

where,

Na,w = Na2Na,f

Na,f = bftf fyd


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(i) Na> Nc,fNa,w (P.N.A. in steel flange)

Nc,f

Na

fyd

2fydNa- Nc,f

C.L.

Beam

P.N.A.

Take moments about the top flange of steel beam

222 ,,,

xNN

hhhN

hNM fca

pspfc

aaRdpl

ydf

fcapspfc

aaRdpl

fb

NNhhhN

hNM

422

2,

,,


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(ii) Nc,f < Na,w (P.N.A. in steel web)

P.N.A.

Na

Nc,f

fyd

hs- hp

ha

hp fydhs

Na


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Neutral axis depth, x


fcwyd Nxtf ,2

wyd

fc

tf

Nx

2

,

Nc,f

fyd

fy

Ma

Nc,f

fyd

fydP.N.A.

C.L. of

Beam

x

2 fyd


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Nc,f

fyd

fy

Ma

Nc,f

fyd

fydP.N.A.

C.L. of

Beam

x

2 fyd

Take moments about the centre line of steel beam

222 ,,,

xN

hhh

hNMM fc

ps

pa

fcaRdpl

wyd

fcpsa

fcaRdpltf

NhhhNMM

42

2

,

,,


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Full Shear Interaction


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Partial Shear Interaction


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Partial Shear Interaction


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Moment Resistance, Mpl,Rd

cfc

RdaplRdplRdaplRdN

NMMMM ,,,,,


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Composite Columns


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Typical cross-sections of composite columns


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Cross-sections limit for the composite columns


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Cross section resistance

Steel contribution ratio,

= Aafyd / Npl,Rd 0.2 0.9If < 0.2, the column should be designed as RCIf > 0.9, the column should be designed as Steel

Npl,Rd = Aafyd+Asfsd+ 0.85Acfcd

CHS:


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Relative Slenderness

0.2,

cr

Rdpl

N

N

NPl,Rk= Aafyd+Asfsd/s+ 0.85Acfcd/c

Ncr= 2 (EI)eff/ L2(EI)eff= EaIa+ EsIs+0.6 Ec,effIc

Buckling resistance

tEdEdG

cmeffc

NN

EE

)/(1

1

,

,


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Buckling resistance


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Buckling curve

EN1993-1-1


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Resistance to axial & bending

Calculate Npl,Rd, Npm,Rd, Mmax,Rd and Mpl,Rd

Npl,Rd = Aafyd+Asfsd+ 0.85AcfcdNpm,Rd = 0.85Acfcd

Mmax,Rd = Wpl,afyd+ Wpl,sfsd+ 0.85Wpl,cfcd /2

Mpl,Rd = Mmax,Rd - Wpl,a,n fyd- 0.85Wpl,c,n fcd /2Construct Interaction N-M Curve


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Interaction NM polygon


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Conclusions Eurocode 4 is the latest standard for design of composite

structures.

It covers the composite design of slabs, beams as well ascomposite columns which is not previously covered inBS5950-3.1.

This presentation highlights the major differences indesign using Eurocodes to the British Standard BS5950

on steel and composite structures.


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Thank you

Documents

RSA_Singapore Dennis Lam 2013