Impact of Eurocode 4 on Composite SteelImpact of Eurocode 4 on Composite Steel and Concrete Structures

Chiew Sing-PingSchool of Ci il and En ironmental EngineeringSchool of Civil and Environmental EngineeringNanyang Technological University, Singapore

12 July 2013

Scope of Presentation

Design codesDesign codes

MaterialsMaterials

Composite columnsp

Composite beams

Composite slabs

2

Design Codes for Composite StructuresEffective 1st April 2015: Till 31st March 2015:

Eurocode 1 - for loadingsEurocode 2

BS 6399- for loadingsBS 5950-1Eurocode 2

- for concrete properties and some of the concrete related checks

BS 5950 1- for construction stage, design of pure

beam (such as longitudinal shear)

Eurocode 3 (many Parts)for construction stage design of

BS 5950-6- for design of profiled steel sheetingBS5950 3 1- for construction stage, design of

pure steel beam and profiled steel sheeting

BS5950-3.1- for design of composite beamBS5950-4

Eurocode 4 Part 1-1 - general rules of buildings Eurocode 4 Part 1 2

- for design of composite slabBS 5400-5

for design of composite columnEurocode 4 Part 1-2 - for the structural fire design

- for design of composite columnBS 5950-8- for structural fire design

3

g

Design Safety Factors

Eurocodes British Standards

Load safety factors 1.35 Gk + 1.5 Qk 1.4 Gk + 1.6 Qk (BS5950)oad sa e y ac o s 35 Gk 5 Qk Gk 6 Qk ( S5950)1.2 Gk + 1.5 Qk (BS5400-5)

Material f

Structural steel 1.0 1.0 (BS5950)1.05 (BS5400-5)

safetyfactors

Concrete 1.5 1.5

Reinforcement 1.15 1.15

4

Material Strength

Concrete and steel strengths in EC4 and BS5950

BS5950 EC4

ConcreteNormal C30 – C50 C20/25 – C60/75

Light weight C25 C40 LC20/22 LC60/66Light weight C25 – C40 LC20/22 – LC60/66

Structural steel ≤ 355 N/mm2 ≤ 460 N/mm2

Cube strength Cylinder strength / Cube strength

The ranges are narrower compared to EC2 (C12/15 – C90/105) and EC3 (≤ 690 N/mm2) because of more limited knowledge and experience in(≤ 690 N/mm ) because of more limited knowledge and experience in composite members with very high concrete and steel strengths.

5

Concrete Strength One of the most noticeable differences in Eurocodes is the way

t t th i ifi d th h tconcrete strength is specified throughout.

In British Standards, In EurocodesIn British Standards, the cube strength fcu is used.

In Eurocodes, the cylinder strength fck is used.

6

BSCube strength

25 N/mm2Will different strength gives different

25 N/mm2

Converting from the concrete different

resistance ?

EC

strength to equivalent plastic stress blockEC

Cylinder strength 20 N/mm2

stress block

BS: 0 45 f = 0 45×25 = 11 25 N/mm2BS: 0.45 fcu = 0.45×25 = 11.25 N/mm2

EC: 0.85 fck/γc= 0.85×20/1.5 = 11.33 N/mm2EC: 0.85 fck/γc 0.85 20/1.5 11.33 N/mm

No difference!

7

Steel Strength

EC3 has additional ductility requirements compared to BS5950 in terms of stress ratio, elongation and strain ratio.

Normal strength steel high strength steel• fu/fy ≥ 1.10

• Elongation at failure not

• fu/fy ≥ 1.05 (EC3-1-12)

• fu/fy ≥ 1.10 ( UK NA to EC3-1-12)Elongation at failure not less than 15%

• ε ≥ 15ε ε is the yield

u y ( )

• Elongation at failure not less than 10%εu ≥ 15εy εy is the yield

stain • εu ≥ 15 εy

8

Problem Some product standards only have requirements on the nominal yieldand tensile strengths, or their minimum values. The stress ratio calculated

di h i l l l i h h EC3 d iliaccording to these nominal values cannot comply with the EC3 ductilityrequirement.

N i l i ld N i l t ilStandard Grade Nominal yield strength (MPa)

Nominal tensile strength (MPa) Stress ratio

G500 500 520 1.04AS 1397

G500 500 520 1.04G550 550 550 1.00

AS 1595 CA 500 500 510 1.02AS 1595 CA 500 500 510 1.02EN 10326 S550GD 550 560 1.02ISO 4997 CH550 550 550 1.00

AS 1397: Steel sheet and strip – hot-dip zinc-coated or aluminium/zinc-coatedAS 1595: Cold-rolled, unalloyed, steel sheet and stripEN 10326: Continuously hot dip coated strip and sheet of structural steelsEN 10326: Continuously hot-dip coated strip and sheet of structural steelsISO 4997: Cold-reduced carbon steel sheet of structural quality

9

Profiled Steel Sheeting

Most types of profiled steel sheeting are manufactured fromG500/G550 steel in accordance with AS1397G500/G550 steel in accordance with AS1397.

10

Headed Stud Shear Connector

In BS 5950, the resistances of headed studs in solid slab are given for various combinations of height, diameter and concrete strength but the physics behind these numbers are not explained.

I EC4 th i t i d i t tiIn EC4, the resistance is expressed in two equations governed by the strength of concrete and steel.

11

Characteristic Resistance Qk of Headed Studs in

Di i f h d d t d h Ch t i ti t th f

Normal Concrete (BS 5950-3.1 Table 5)Dimensions of headed stud shear

connectorsCharacteristic strength of

concrete (fcu)Nominal shank Nominal As-welded 25 30 35 ≥ 40Nominal shank

diameter (mm)

Nominal height (mm)

As welded height (mm)

25 N/mm2

30 N/mm2

35 N/mm2

≥ 40 N/mm2

25 100 95 146 154 161 168

22 100 95 119 126 132 139

19 100 95 95 100 104 109

19 75 70 82 87 91 9619 75 70 82 87 91 96

16 75 70 70 74 78 82

13 65 60 44 47 49 52

12

Design Resistance of Headed Studs in Solid C t Sl b (EC4)Concrete Slab (EC4)

EC4 calculates the resistance as the minimum of two equations,EC4 calculates the resistance as the minimum of two equations, shown here as (1) and (2).

2u

RdV

0.8 4f dP πγ

= (1)Vγ

2ck cm

Rd

0.29 d f EP

α= ⎟

⎞⎜⎛ +=α 12.0 sch

(2)RdV

Pγ ⎟

⎠⎜⎝

+α 12.0d

(2)

The two equations represent the 2 possible failure modes:(i) failure in the shank of headed stud and (ii) failure in concrete.(i) failure in the shank of headed stud and (ii) failure in concrete.

13

steel failure

Failure in the headed stud

Push out Test SpecimenPush-out Test Specimen concretecrushes

14Failure in concrete

Comparison of Characteristic Resistances in i D i C d

Ch t i ti i t f h t d P (kN)

various Design Codes

Characteristic resistance of shear stud, PRk (kN)Headed shear studs embedded i lid t l b f

Characteristic strength of concrete (N/mm2)in solid concrete slab of normal weight concrete 25 30 35 40

BS5400 P t 5 2005 90 100 104 109BS5400: Part 5: 2005 90 100 104 109

BS5950: Part 3.1: 2010 95 100 104 109

EC4: Part 1.1: 2004 81.0 92.1 100.6 102.1

N t N i l h k di t 19Notes: Nominal shank diameter = 19mmNominal height = 100mm while as-welded height = 95mm

EC4 leads to a 17% reduction of the characteristic resistanceEC4 leads to a 17% reduction of the characteristic resistance.

15

Characteristic Resistance of Stud (EC4 and BS5950)

160

120

140BS (d=22mm, h=100mm)

EC (d=22mm, h=100mm)

80

100BS (d=19mm,h=100mm)

EC (d=19mm, h=100mm)

BS ( d=16mm, h=75mm)(kN

)

60

80EC (d=16mm, h=75mm)

P R k

20

40

0

20

25 30 35 40 45 5025 30 35 40 45 50Concrete strength (N/mm2)

Note: the differences are larger for smaller stud diameters

16

Note: the differences are larger for smaller stud diameters

In general, the resistance of headed stud shear connectors determined by EC4 is lower than BS5950.

more headed studs are needed in EC4 design ! g

17

Design Resistance of Headed Studs in C it Sl bComposite Slab

The design resistance of headed stud connector in compositegslab with profiled steel sheeting is more complex than in a solidslab. It is influenced by the following factors:

The direction of the ribs relative to direction of span of thecomposite beam;p ;

The mean breadth b0 and depth hp of profiled steel sheeting;

The diameter d and height hsc of the headed shear stud;

The number nr of the headed studs in one trough;r g

Whether or not a headed stud is central within a trough.

18

Reduction Factor ktt

Design shear resistance is taken as the resistance in a solid slab multiplied by the reduction factor kmultiplied by the reduction factor kt

b0 b0

h sc

sch

h p

h p/2

h P

h s

h

sc0 17.0 khbk ≤⎟⎟⎞

⎜⎜⎛

=EC4: maxt,ppr

t 1 khhn

k ≤⎟⎟⎠

⎜⎜⎝

−=EC4:

BS5950 3 1: The coefficient is 0 85 and 0 6 for re entrant trough profilesBS5950-3.1: The coefficient is 0.85 and 0.6 for re-entrant trough profilesand 0.63 and 0.34 for open trough profiles

For the EC4 these values are about 17% lower than the BS for re-entrantFor the EC4 these values are about 17% lower than the BS for re entrant profiles, but about 40% higher than the BS for open trough profiles.

19

Upper Limit kt,max for the Reduction Factor kt

Generally, most profiled sheet sheeting is designed such that their limiting value dominates, so the reduction factor is independent of the geometry

profiled Number of stud Thickness tEC4 BS 5950-3.1

g y

profiled steel

sheeting

Number of stud connectors per

trough

Thickness tof sheet

(mm)

Stud not exceeding 20mm in diameter and

welded through

Stud not exceeding 19mm in g

profiled steel sheeting diameter

Re-entrant nr=1 ≤1.0>1 0

0.851.0 1.0Re entrant

trough>1.0 1.0

nr=2 ≤1.0>1.0

0.700.8 0.8

≤1 0 0 85Open trough

nr=1 ≤1.0>1.0

0.851.0 0.82

nr=2 ≤1.01 0

0.700 8 0.45nr 2 >1.0 0.8 0.45

For open trough profiles, the reduction factor in EC4 ≥ BS5950F t t t h fil th d ti f t i EC4 ≤ BS5950For re-entrant trough profiles, the reduction factor in EC4 ≤ BS5950

20

Characteristic resistance of shear stud, PRk (kN), Rk ( )Headed shear studs in

composite slab with profiled

Characteristic strength of concrete fcu(N/mm2)composite slab with profiled

steel sheeting 25 30 35 40

Re entrant 95 100 104 109BS5950: Part 3: 2010

Re-entrant 95 100 104 109

Open trough 77.9 82 85.3 89.4

EC4: Part 1.1: 2004 68.9 75.5 85.5 86.8

nr=1

Notes: Nominal shank diameter = 19mmNominal height = 100mm while as-welded height = 95mm

r

The resistance of shear stud in composite slab determined in EC4 is up to 27% lower than that given in BS 5950.

21

Top-Down Construction

Kingposts (supporting the roof) which are part of the barretteKingposts (supporting the roof) which are part of the barrette piles installed during the foundation stage

22

Installation of a kingpost into the barrette pile

23

KingPost in columng

Excavation for starterExcavation for starter bars

Install starter barsInstall starter bars

24Casting column head

Column Design ApproachCross section resistance (yielding)

Resistance to compressionResistance to compression Resistance to moment Reduced moment resistance under compressive force, i.e.Reduced moment resistance under compressive force, i.e. interaction between compression and bending

Member buckling resistanceMember buckling resistance Axial buckling resistance Reduced moment resistance under compressive force, i.e.Reduced moment resistance under compressive force, i.e. interaction between compression and bending

FF LBA

GNIA

Fcr

GNIATypes of elastic analysis and design

25δe

Simplified Method (EC4 Clause 6.7.3.4)

Design Conceptsg p

Design based on the EC3 buckling curves

χ

Axial compression

EC3 buckling curves(similar to pure steel column)

compressionDesign based on second-orderanalysis with equivalent memberI f ti ( i lifi d th d)

e0

Resistance of

Imperfection (simplified method)

Resistance of member in combined compression

Design based on second orderanalysis with equivalent membercompression

and bending

y qImperfection (simplified method) e0

26

Axial Compression Resistance

Compression resistance of composite column

sdscdcdaRdpl fAfAfAN ++= sdscdcydaRdpl, fAfAfAN ++

= + +

/f /f

steel concrete reinforcement

yk a/f γ ck c/f γ sk s/f γ

27

Axial Buckling Resistance

01Ed ≤N 0.1

Rdpl,

Ed ≤Nχ

The buckling reduction factor (EC3 approach) Plastic resistance( pp )

0.1122≤=

λφφχ a

b

1.0

x Euler buckling -2+ λφφ

( )[ ]22.0-15.0 λλαφ ++=

b

c

Rkpl,

NN

=λλ

0.0 1.0 2.0crN λ

28

Buckling Curve - EC3g

29

Buckling Curve – EC4

Cross-section Limits Axis of b kli

Buckling curvebuckling S235 - S460

Concrete encased sectiony-y bz-z c

Partially concrete encased section

y-y bsection z-z c

Concrete filled circular and rectangular hollow sections

ρs ≤ 3% any a3% < ρ ≤ 6% any brectangular hollow sections 3% < ρs ≤ 6% any b

• For steel column, the buckling curve is related to steel section and steel strength.

• For composite column, the buckling curve is related to the cross-section. The strength of steel has little influence on the buckling curveThe strength of steel has little influence on the buckling curve.

30

Example - Comparison of Design Approach

Design based on EC3 b kli

Design based on second order analysis with NEC3 buckling

curve

order analysis with equivalent member

imperfection

NEd

Buckling curve bMember

imperfection L/200 e0imperfectionResistance of

axial N Rd (χ) = 4320 kN N Rd (e0) = 4108 kN

0

compressionRd (χ) Rd (e0)

Comparison N / N 1.05 NNRd(X) / NRd(e0) NEd

Note: design based on the use of member imperfection e0 leads to a maximum difference of 5% in comparison with design based ona maximum difference of 5% in comparison with design based on the EC3 buckling curve approach.Design data:

31

fy=355N/mm2, fck=25N/mm2, fsk=500N/mm2, Cross-section: 350mm×350mm, steel section: 254×254 UC73.Column length: 5.0m, 4 bars of 20mm diameter

Example - Comparison of Design Approach

Design based on the EC3 Design based on second order analysis buckling curve approach with equivalent member imperfection

approach Rd( )N χ 0Rd (e )N( )χ 0( )

Rd( ) pl,Rd=N Nχ χN0Ed,max Rd(e ) 0=M k N e

Tedious approach !

The maximum resistance can beobtained by:

0.1-

122≤

+=

λφφχ

N

Npl,RdEd,max M pl,RdM Mα μ≤ Tedious approach !

obtained by:φφ

( )[ ]22.0-15.0 λλαφ ++=

0Rd(e ) 0 M pl,Rd =kN e Mα μNRd(e0)

Npm,Rd

cr

Rkpl,

NN

=λ0pl,Rd Rd (e )

pl,Rd pm,Rd

-=

-N NN N

μM

Second order effect factor k: 2

ef,IIff

( )=

EIN

π

Mpl,RdμMpl,Rd

1=1 /

kN N

Easier approach !

32

cr,eff 2cr

NL0Rd(e ) cr,eff1- /N N

Resistance of Members in combined C i d B diCompression and Bending

The EC3 buckling curve approach can be adopted forg pp pcomposite column under axial compression, however, thisapproach is not suitable for composite column subjected topp p jaxial compression and bending moment.

In design of slender RC column, an accidental eccentricity ofthe axial load in the column is introduced to calculate themaximum moment at mid-height of the column.

Similar to slender RC column, equivalent initial bowimperfections (member imperfections) are used in the design of

it l f i lifi ticomposite column for simplification.

33

Bending Moment due to Member Imperfection

For the member imperfection e caused by theNEdFor the member imperfection e0 caused by the design axial load NEd on a composite column, there will be a bending moment of NEde0there will be a bending moment of NEde0.

The design bending moment for the compositel l h id d b h d de0 column length considered both second-order

effects of end moment and imperfection is givenby:by:

0Ed2Ed1Ed.max eNkMkM +=

NEd k1, k2 are the factors of second order effects

β l t d t d t ti

Ed cr,eff

=1- /

kN N

β related to end moment ratio

34

Member Imperfections for Composite Column

Cross-section Axis of buckling

Buckling curve

Member imperfection (e0)p ( 0)

Concrete encased section y-y b L/200

z-z c L/150y

z-z c L/150

Partially concrete encasedSection

y-y b L/200z

yz-z c L/150

Circular and rectangularh ll ti

y-y a L/300z

y

hollow sectionz-z b L/200

Circular hollow section with y y b L/200

zy

Circular hollow section withadditional I-section

y-y b L/200

z-z b L/200zy

Partially encased H sectionwith crossed H section any b L/200y

z

35

z

Improvement in the Design of Column in C bi d C i d B diCombined Compression and Bending

Compared to EC4 (1994), the simplified method forcomposite columns in EC4 (2004) was changed usingcomposite columns in EC4 (2004) was changed usingsecond order analysis and equivalent member (initial bow)imperfection which takes into account the effects of residualpstresses and geometrical imperfections.

Introducing initial bow imperfections into the simplifiedIntroducing initial bow imperfections into the simplifiedmethod for composite columns, the scope of the simplifiedmethod can be extended to sway framesmethod can be extended to sway frames.

36

EdM

Mα≤1 Edk M

Mpl,RdMμ

The influence of imperfection is taken into account indirectly in the interaction curve The factor μ is reduced by acurve. The factor μd is reduced by a relevant amount to account for the moment due to the member

(a) EC4: 1994 imperfection.

Ed, maxM

MM

α≤1 Ed 2 Ed 0k M k N e+M

d pl,RdMμ

The member imperfection can be taken pinto account in the global analysis and hence it is not necessary to allow for th i f ti i th l i f th

37

the imperfection in the analysis of the interaction curve.(b) EC4: 2004

Design of Composite Beam

Nc,f

NNp

Npl a

The concrete slab works best in compression while the steel section

Npl,a

pworks best in tension; hence, a large moment resistance is generated as a force couple.

Resistance mobilization in both the concrete slab and the steel section is limited by the shear connection along the concrete interface.y g

38

Failure Modes of Composite BeamIV

IV

I-I resistance to sagging moment and vertical shearII-II resistance to hogging moment and shear and M-V interactionIII-III shear connection @ the steel – concrete interfaceIV-IV lateral torsional bucklingV V L it di l h f th t flV-V Longitudinal shear of the concrete flange

39

Lateral Torsional Buckling ResistanceIn BS5950-3.1, no equation is provided to calculate the lateral torsional buckling resistance of continuous composite beam under hogging moment over the internal support.When checking LTB, the methods given in BS5950-1(design of steel beam) is supposed to be used(design of steel beam) is supposed to be used.

In EC4 the restraint of slab is taken into account comparedIn EC4, the restraint of slab is taken into account compared with steel beam in EC3.

40

BS5950-3.1 EC4

b b xM p S= RdLTRdb, MM χ=

LT1 1χ = ≤

Where pb is determined by λTB

=n uvλ λ

With:

LT 2LT LT LT

1χφ φ λ

≤+ −

RkM

TB t t=n uvλ λ

0.5⎡ ⎤ Rk

LTcr

MM

λ =

1/2

( ) ( )s

t 2 2s

4 /=

1+ 2 / +0.05 /a h

va h xλ

⎡ ⎤⎢ ⎥⎢ ⎥⎣ ⎦

( ) ( ) 1/22 2cr c 4 a at s a afz/ /M k C L G I k L E Iπ⎡ ⎤= +⎣ ⎦ (EC4)

0.522TI L GIEIπ ⎛ ⎞

cr 1 2 2+w cr Tz

cr z z

I L GIEIM CL I EI

ππ

⎛ ⎞= ⎜ ⎟

⎝ ⎠(EC3)

EC4 EC3 BS5950-3.1 EC4/BSRatio

EC4/EC3Ratio

L t l t i l41

Lateral-torsional buckling 546 kNm 531 kNm 479 kNm 1.14 1.03

Elastic Critical Moment

Inverted- U frame ABCD resisting lateral-torsional buckling

In this approach the elastic critical moment M is determined using theIn this approach, the elastic critical moment Mcr is determined using the so-called “continuous inverted U-frame model”.The model given in EC4 takes into account the lateral displacement of the g pbottom flange causing bending of the steel web and the rotation of the top flange that is resisted by bending of the concrete slab.

( ) ( ) 1/22 2cr c 4 a at s a afz/ /M k C L G I k L E Iπ⎡ ⎤= +⎣ ⎦

42

Composite Slab

TrapezoidalOpen Trough (Trapezoidal)

Re-entrant

Possible modes of failure:Shear failure at end supportShear failure at end supportMoment failure near mid-span regionDebonding within longitudinal shear span along the interface between

f43

concrete slab and decking, i.e. shear bond failure critical

Longitudinal Shear

How can concrete “stick” to profiled sheeting after bending?How can concrete stick to profiled sheeting after bending?

How reliable is the shear bond along the interface between gconcrete and profiled sheeting ?

• Surface bonding due to chemical reaction• Surface bonding due to chemical reaction- non ductile failure, hence not so reliable.

• Mechanical interlocking due to indentations or embossments in the profiled sheeting or end anchorageembossments in the profiled sheeting or end anchorage- ductile failure with rational provision, hence more

reliable.

44

Longitudinal Shear

End slip

CrackingCracking

T t tTest setup

45

m-k Method

• EC4: • BS5950-4:EC4:

p pl Rd

bd mAV k

⎛ ⎞= +⎜ ⎟

S5950

r ps ss r cu1 25

m AB dV k fB L

⎛ ⎞= +⎜ ⎟

⎝ ⎠Concrete strengthl,Rd

vs sbLγ ⎜ ⎟⎝ ⎠ s v1.25 B L⎝ ⎠ strength

m= 163.26

m= 172.45k= 0.2491

m 163.26k= 0.0312

46

k 0.2491

Comparison of Longitudinal Shear

EC4 BS5950-4

Short span Long span Short span Long span

m 172 5 163 3m 172.5 163.3k 0.2491 0.0312

Shear bondShear-bond resistance Vl Rd (kN)

79.3 60.1 74.3 56.2l,Rd ( )

Test Short span 81.2 kN Long span 61.6 kN

BS5950 provides a more conservative value for longitudinal shear resistance

47

Vertical Shear

BS 5950-4 EC4

( )( )1/3100V C k f k b dρ σ= +V b d v= ( )( )v,Rd Rd,c 1 ck 1 pc w p100V C k f k b dρ σ= +

( )v,Rd,min min 1 cp w pV v k b dσ= +

v b s cV b d v=1/3 1/31/4

s cu1000.79 400= A fv⎛ ⎞ ⎛ ⎞⎛ ⎞⎜ ⎟ ⎜ ⎟ ⎜ ⎟

( ), , p pc

m v 25v

b d dγ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠⎝ ⎠ 3/2 1/2

min ck0.035v k f=

BS 5950-4 EC4 Experiment

153.6 kN107.8 kN118.7kN

EC4 provides a more conservative value for vertical shear resistance

48

Punching Shear

BS 5950-4 EC4

( )p s p cCritical perimeter -V D D v= ×

( )p,Rd p p Rd

1/3

V C d v=

1/3 1/31/4s cu

cm v

1000.79 400=25

A fvb d dγ

⎛ ⎞ ⎛ ⎞⎛ ⎞⎜ ⎟ ⎜ ⎟ ⎜ ⎟

⎝ ⎠ ⎝ ⎠⎝ ⎠3/2 1/2

i k0.035v k f=

( )1/3Rd Rd,c 1 ck min100v C k f vρ= ≥

m vγ ⎝ ⎠ ⎝ ⎠⎝ ⎠ min ck0.035v k f

( ) ( )p c p f p f p c2 2 2 2 2 2 2C h b h a h d hπ= + + + + + −( ) ( )s p sCritical perimeter = 4 - +4 +4 length of load areaD D d

BS 5950-4 EC4 Experiment

186 kN139 kN108kN

BS5950-4 provides a more conservative value for vertical shear resistanceBS5950 4 provides a more conservative value for vertical shear resistance

49

Conclusions

1. Composite members with high strength steel and concrete t id th f EC4outside the scope of EC4.

2. Common grades of profiled steel sheeting cannot meet EC3 ductility requirement design strength will have to beEC3 ductility requirement, design strength will have to be downgraded.

3 The resistance of headed stud shear connectors is3. The resistance of headed stud shear connectors is generally lower in EC4 compared to BS5950; Important to note that BC1 adopts EC4 design resistance valuesnote that BC1 adopts EC4 design resistance values.

4. For composite columns, the EC4 buckling curves are different compared to EC3 due to contribution of concretedifferent compared to EC3 due to contribution of concrete. However, unlike EC3, no special consideration for composite column with S460 steel.composite column with S460 steel.

50

Conclusions

5. The simplified design approach using second orderanalysis and equivalent member imperfection without anyneed for member buckling resistance check is much

i f it l i bi d ieasier for composite column in combined compressionand bending moment.

6 EC4 id id f l t l t i l b kli h k6. EC4 provides guidance for lateral-torsional buckling checkfor continuous composite beams taking into account thebeneficial effect provided by the concrete slabbeneficial effect provided by the concrete slab.

7. EC4 also provides clear guidance for prototype testingand development of composite slab system using newand development of composite slab system using newprofiled steel sheeting.

51