EN1994 5 Hicks Composite Slab

7/28/2019 EN1994 5 Hicks Composite Slab

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Brussels, 18-20 February 2008 Dissemination of information workshop 1

Background and ApplicationsEUROCODES

EN 1994 - Eurocode 4: Design of composite steel andconcrete structures

Composite Slabs

Stephen Hicks


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EUROCODESBackground and Applications Composite slabs

Concrete cast in situWelded mesh reinforcement for crackcontrol, transverse load distribution and

fire resistance

Headed stud connectors for shear

connection to the composite beam and,when required, end anchorage to the slab


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EUROCODESBackground and Applications

Through-deck welding of headed stud shear connectors


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Conventional composite construction


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EUROCODESBackground and Applications Benefits of composite beams

Bending resistance increased by a factor of1.5 to 2.5

Stiffness increased by a factor of 3 to 4.5

Steel weight reduced by typically 30 to 50%

Reduction in beam depth (span:depth 25)

Lightweight construction


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EUROCODESBackground and Applications Benefits of composite slabs

Profiled steel sheeting acts as a safeworking platform and permanent formwork.

Unpropped construction may be achieved.

Sheeting can stabilise beams duringconstruction.

Sheeting can provide all, or part, of the maintension reinforcement to the slab.


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EUROCODESBackground and Applications Examples of composite construction in UK

Commercial sector Residential sector


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EUROCODESBackground and Applications Examples of composite construction in UK

Health sector


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Types of profiled steel sheeting defined in EN 1994-1-1

Re-entrant profiled steel

sheet

Open trough profiled steel

sheet


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Practical examples of open trough and re-entrant profiled steel

sheets used for composite slabs

Cover width: 1000

Multideck 60

323 mm

9 mm

60 mm

15 mm

Cover width: 600300 mm

60 mmComFlor 60

207 mm

58 mmConfraplus 60

Cover width: 1035

183 mm

73 mm Cofrastra 70

Cover width: 732

Cover width: 900

Multideck 80

300 mm

9 mm

80.5 mm

15 mm

80 mm

180 mm 120 mm

145 mm

70 mm ComFlor 80

Cover width: 600

Cover width: 750

Cofrastra 40

150 mm

0 mm

152.5 mm

51 mm

Cover width : 610

Super Holorib 51


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Composite construction with services passed under

structural zone


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EUROCODESBackground and Applications Examples of fixings for ceilings and services

Wedge attachment Clip attachment

Alternative wedge attachment


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EUROCODESBackground and Applications EN 1994-1-1 detailing requirements

Scope limited to sheets with narrowlyspaced ribs : br/ bs 0,6

Slab thicknessWhen slab is acting compositely withbeam or is used as a diaphragm:h 90 mm & hc 90 mm

When slab is not acting compositelywith beam or has no stabilizing

function:h 80 mm & hc 40 mm

Reinforcement 80 mm/m in bothdirections

Spacing of reinforcement barss 2h & 350 mm

Maximum aggregate sizedg 0,4 hc, b0/ 3 and 31,5 mm

o

o

b br

r

b

b

s

s

Re-entrant trough profile

b

b

bb

b

b

p

p

p

h

h

h

h

h

h

c

c

h1/2

Open trough profile


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EN 1994-1-1 composite slab bearing requirements

The bearing length shall be such that damage to the slab and the bearing is avoided;

that fastening of the sheet to the bearing can be achieved without damage to the

bearing and that collapse cannot occur as a result of accidental displacement during

erection.

For bearing on steel or concrete: lbc = 75 mm and lbs = 50 mm

For bearing on other materials: lbc = 100 mm and lbs = 70 mm

bs bs bs

bc

bc

(a) (b)

bs bs

(c)


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Actions and action effects on profiled steel sheeting

a) Imposed load on a 3 m 3 mworking area (or the length of

the span if less), with an

intensity of 10% of the self-weight of the concrete but

1,5kN/m and 0,75 kN/m

b) Imposed load of 0,75 kN/m

c) Self weight loadcorresponding to the design

thickness of the slab plus

ponding effects if > h/ 10

b b b b

3000 3000

a ac c


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Analysis for internal forces and moments - set-up for double

span tests on profiled steel sheeting

Combined bending andcrushing at internal

support


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Typical forms of shear connection in composite slabs

(a) (c)

(b) (d)

a) Mechanical interlock through the provision of indentations orembossments rolled into the profile.b) Frictional interlock for re-entrant profiles.c) End anchorage from through-deck welded stud connectors or other

local connection.d) End anchorage from deformation of the ends of the ribs at the end of the

sheeting.


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EUROCODESBackground and Applications Longitudinal shear resistance

Test set-up from EN 1994-1-1, Annex B

EUROCODES


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EUROCODESBackground and Applications Classification of ductile or brittle behaviour

1. Brittle behaviouro m-k method

2. Ductile behaviour - failure load exceeds the load causing a

recorded end slip of 0,1 mm by more than 10%o Partial connection methodo m-k method

LoadP(kN)

50

40

30

20

10

Slip atfirst end

Slip atsecond end

10 20 30 40 50

P/2 P/2

Deflection (mm)

1

2

Load

F

(kN)

F/2 F/2

EUROCODES D t i ti f l it di l h i t ith t d


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Mean value for the ultimate shear stress withadditional longitudinal shear resistancecaused by the support reaction:

Determination of longitudinal shear resistance without end

anchorage for the partial connection method

-

-

-

-

+

+

+

f

f

f

f

f

yp

yp

yp

cm

cm

N

N

cf

cf

c

A

B

C

1.0

p,Rm

p,Rm

MM

test

test test

M

M

=

cN

N

F2

F2

L Lo s

M

M

Mean value for the ultimate shear stress:

( )os

cftestu

LLb

N

+

=

( )os

tcftestu

LLb

VN

+

=

EUROCODES D t i ti f d i l f f t t


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Determination of design value foru,Rd from tests

For each variable investigated:

3 test specimens with the shear span Ls as long as possible,

whilst still providing failure in longitudinal shear.

1 test specimen with the shear span Ls as short as possible(but not less than 3 overall slab thickness), whilst still

providing failure in longitudinal shear to classify thebehaviour

Characteristic value of the longitudinal shear strength u,Rkcalculated from the test values as the 5% fractile from EN1990,Annex D

u,Rk is divided by the partial safety factorVS to obtain a designvalue u,Rd

EUROCODES Neutral axis above the sheeting and full shear connection ( = 1)


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Neutral axis above the sheeting and full shear connection ( = 1)

Design compressive normal force in the concrete flange:Nc,f= Np =Ape fyp,d

Depth of the concrete in compressionxpl = Nc,f / (0,85 fcd b) hc

Design moment resistance of the composite slab in sagging bending

MRd = Nc,f (dp - 0,5 xpl)

dp

xpl

z

c,f

p

N

N

M pl,Rd

f

f

yp,d

cd0.85

+

-

Centroidal axis of the profiled steel sheeting

EUROCODES Neutral axis within the sheeting and full shear connection ( = 1)


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Neutral axis within the sheeting and full shear connection ( = 1)

Design compressive normal force in the concrete flange: Nc,f= 0,85 fcd b hc

Reduced plastic moment resistance of the sheeting:

Lever arm:


MRd = Nc,fz + Mpr

p

c,fN

M

f

f

f

yp,d

yp,d

cd0.85

+

+

+

- --

e e


Plastic neutral axis of the profiled steel sheeting

hc

prz

+=

=

dyp,pe

cfpapr 125,1

fA

NMM

( )dyp,pe

cfppc5,0

fA

Neeehhz +=

EUROCODES Partial shear connection (0 < < 1)


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Partial shear connection (0 < < 1)

Design compressive normal force in the concrete flange: Nc = u,Rd b Lx Nc,f

Reduced plastic moment resistance of the sheeting:

Lever arm:


MRd = Nc z + Mpr

=

dyp,pe

cpapr 125,1

fA

NMM

( )dyp,pe

cppc5,0

fA

Neeehhz +=

p

N

M

f

f

f

yp,d

yp,d

cd0.85

+

+

+

- -

--

e e


Plastic neutral axis of the profiled steel sheeting

hc

pr

+=

c

z

EUROCODES End anchorage


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EUROCODESBackground and Applications End anchorage

According to EN 1994-1-1, design resistance of a headed stud welded through the steelsheet used for end anchorage should be taken as the lesser of:

PRd kt

or

Ppb,Rd = k ddo t fyp,d

where PRd is the design resistance of a headed stud embedded in concrete, kt is areduction factor for deck shape, ddo is the diameter of the weld collar (which may betaken as 1,1 times the shank diameter), tis the sheet thickness and k = 1 + a/ ddo 6,0

d

f

f

yp

yp

/2

/2

d0

1.5 d0a d

Stud

EUROCODES Variation of bending resistance along a span: uniform distributed


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Variation of bending resistance along a span: uniform distributed

load

M

M

pl,Rd

pl,p,RdM

Ve,Rdb u,Rd

L LLsf x

M Ed

L

q

L x

MRd with end anchorage

MRd without end anchorage

MRd

Mpa

MEd

Rdu,

Rdpb,

b

P

b

kP

Rdu,

tRd

or whichever is the lesser

EUROCODES Variation of bending resistance along a span: Point load


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Background and Applications

g g p

M

M

pl,Rd

pl,p,Rd

L LLsf x

M Ed

L

L x

M

FMRd without end anchorage

MEd

Mpa

MRd

EUROCODES Classification of ductile or brittle behaviour


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Background and Applications Classification of ductile or brittle behaviour

1. Brittle behaviouro m-k method

2. Ductile behaviour - failure load exceeds the load causing arecorded end slip of 0,1 mm by more than 10%o Partial connection methodo m-k method

LoadP(kN)

50

40

30

20

10

Slip atfirst end

Slip atsecond end

10 20 30 40 50

P/2 P/2

Deflection (mm)

1

2

Load

F

(kN)

F/2 F/2

EUROCODES Determination of m-k values from tests


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Background and Applications Determination ofm kvalues from tests

For each variable investigated:

3 test specimens with the shear span Ls as long as possible, whilst still providing failurein longitudinal shear.

3 test specimens with the shear span Ls as short as possible (but not less than 3 overallslab thickness), whilst still providing failure in longitudinal shear to classify the behaviour

If behaviour brittle, Vt = 0,8 (F/ 2)

m

Vertical shear

Longitudinal shear1

2

Vb.d

t

p

k

Flexural

Ab L

L

p

s

s s

sLong Short

L L

F/2 F/2

EUROCODESBackground and Applications Determination of m-k values from tests


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Characteristic regression line

calculated from the test values

as the 5% fractile

Determination ofm kvalues from tests

Design shear resistance

m

Vertical shear

Longitudinal shear1

2

Vb.d

t

p

k

Flexural

Ab L

L

p

s

s s

sLong Short

L L

Mean value

+= kbL

mAbd

Vs

p

VS

p

Rdl,

F/2 F/2

EUROCODESBackground and Applications Disadvantages ofm-kmethod


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Background and Applications sad a tages o et od

The results contain all the influencing parameters, but are

impossible to separate from one another.

Methodology is not based on a mechanical model and istherefore less flexible than the partial connection approach

(contribution from end anchorage and reinforcement need tobe evaluated from additional tests).

Other loading arrangements that differ from the test loading

can be problematical.


Effective width for slabs with concentrated loads


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Forhp/ h 0,6

For bending and longitudinal shear:i) for simple spans and exterior spans ofcontinuous slabs

ii) for interior spans of continuous slabs

For vertical shear

Width of slab over which load is distributed

bm = bp + 2 (hc + hf)

Case c Concentrated loads applied parallelto the spanCase d Concentrated loads appliedperpendicular to the span

bp

Finishes Reinforcement

b

b

hc

m

cm

h

h f

p

L

b

bp

Lp

b bp

1

2

bL

L

Lbbp

+= 12pmem

bL

LLbb

p

+= 133,1 pmem

bL

LLbb

p

+= 1pmev


Transverse reinforcement for concentrated loads


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g pp

If the characteristic imposed loads do not exceed the values given below, a nominaltransverse reinforcement of not less than 0,2% of the area of concrete above the ribs ofthe sheet (which extends the minimum anchorage length beyond bem), may beprovided without any further calculation:

concentrated load: 7,5 kN; distributed load: 5,0 kN/m.

For characteristic imposed loads greater than these values, the distribution of bendingmoments and the appropriate amount of transverse reinforcement should be evaluatedaccording to EN 1992-1-1.

bp

Finishes Reinforcement

b

b

hc

m

cm

h

h f

p


Vertical shear resistance of composite slabs


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Vv,Rd should be determined using EN 1992-1-1, 6.2.2 which gives the following:

Vv,Rd = [CRd,c k(100l fck)1/3 + k1 cp] bsd (6.2a)

with a minimum of

Vv,Rd = (vmin + k1 cp) bsd (6.2b)

wherel =Asl / bs d,Asl is the area of the tensile reinforcement which extends (lbd + d)beyond the section considered and other symbols are defined in EN1992-1-1.

For normal loading conditions, and the fact that the sheeting is unlikely to be fullyanchored, the vertical shear resistance will commonly be based on Eq (6.2b).

For heavily loaded slabs, additional reinforcement bars may be required at the supportand the vertical shear resistance based on Eq (6.2a). According to the ENV version ofEN 1994-1-1, it is permitted to assume that the sheeting contributes toAsl provided thatit is fully anchored beyond the section considered.


Punching shear resistance


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c

c

c c

p

p

p

p p

Section A - A

d

d

AA

p

p

p

d

Loaded area ofdimensions a x b

h f

h

hh

h

Criticalperimeter

b + 2hp f

f

b

a +2h a

The punching shear resistance Vp,Rdshould be calculated according to EN

1992-1-1. For a loaded area ap bp, which

is applied to a screed with a thickness hf,

the critical perimeter is given by:

cp = 2hc+ 2(bp+ 2hf) + 2(ap+ 2hf+ 2dp2hc)

EUROCODESBackground and Applications Serviceability limit states for composite slabs


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Crack widthsFor continuous slabs that are designed as simply-supported, the minimum cross-sectional area ofthe anti-crack reinforcement within the depth hc should be:

0,2% of the cross-sectional area of the concrete above the ribs for unpropped construction 0,4% of the cross-sectional area of the concrete above the ribs for propped construction.

The above amounts do not automatically ensure that wmax 0,3 mm as given in EN1992-1-1 forcertain exposure classes.

If cracking needs to be controlled, the slab should be designed as continuous, and the crack widthsin hogging moment regions evaluated according to EN 1992-1-1, 7.3.

Deflection

Deflections due to loading applied to the composite member should be calculated using elasticanalysis, neglecting the effects of shrinkage.

For an internal span of a continuous slab, the deflection may be estimated using the followingapproximation: the average value of the cracked and uncracked second moment of area may be taken.

for the concrete, an average value of the modular ratio for long-term and short-term effects maybe used.

For external, or simply supported spans, calculations of the deflection of the composite slab may beomitted if:

the span/depth ratio of the slab does not exceed 20 for a simply-supported span and 26 for anexternal span of a continuous slab (corresponding to the lightly stressed concrete limits given

in EN 1992-1-1; and the load causing an end slip of 0,5 mm in the tests on composite slabs exceeds 1,2 times the

design service load.


Standard push test


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150

250

250

150 150260

Cover 15

P

PRk

Load

perstudP

(kN)

Slip (mm)u

6 mm


Position of studs in open trough sheeting and reduction factor

formula according to EN 1994-1-1


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formula according to EN 1994 1 1

bEdge ofbeam

p,g p,nh hh

e

sc

o

Compressionin slab

Force from stud

(a) Central (b) Favourable (c) Unfavourable

kt = 0.85 / nr(b0/ hp) {(hsc/ hp) 1} kt,max

Number of stud

connectors per rib

Thickness t of

sheet

(mm)

Studs not

exceeding 20 mm

in diameter and

welded through

profiled steel

sheeting

Profiled steel

sheeting with

holes and studs

19 mm or 22 mm

in diameter

nr= 1 1,0> 1,0

0,85

1,00

0,75

0,75

nr= 2 1,0> 1,0

0,70

0,80

0,60

0,60


Stud ductility demonstrated in full-scale composite beam tests

with studs through-deck welded in open trough sheeting


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with studs through deck welded in open trough sheeting

0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25 30

Slip (mm)

Axialforce(kN)

7th pair 6th pair

Point at which maximum

moment was applied

in Cycle 5

Point at which deck

delamination was

observed

-40

-20

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30

Slip (mm)

Axialfo

rce(kN)

Strong Central Weak

EUROCODESBackground and Applications Load-slip curves for push tests cf. beam tests


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0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25 30

Slip (mm)

Loadperstud(kN)

Push test Beam test

-40

-20

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30

Slip (mm)

Loadpe

rstud(kN)

Push test Beam test

nr= 1

nr= 2


Recommended detailing to push test with open trough

profiled steel sheeting


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profiled steel sheeting

Back-breaking failure

150 150260

Bedded in mortar or gypsum

4d minimum 750

250250250

P

Steel section:

254 x 254 89 UCor HE 260 B

30 recessoptional

A

T C

EUROCODESBackground and Applications Where can I get further information?


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[email protected]

http://www.access-steel.com/

Documents

EN1994 5 Hicks Composite Slab