en1994 5 hicks composite slab
TRANSCRIPT
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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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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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EUROCODESBackground and Applications
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:
Design moment resistance of the composite slab in sagging bending
MRd = Nc,fz + Mpr
p
c,fN
M
f
f
f
yp,d
yp,d
cd0.85
+
+
+
- --
e e
Centroidal axis of the profiled steel sheeting
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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EUROCODESBackground and Applications
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:
Design moment resistance of the composite slab in sagging bending
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
Centroidal axis of the profiled steel sheeting
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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EUROCODESBackground and Applications
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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Background and Applications
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.
EUROCODESBackground and Applications
Effective width for slabs with concentrated loads
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Background and Applications
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
EUROCODESBackground and Applications
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
EUROCODESBackground and Applications
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.
EUROCODESBackground and Applications
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.
EUROCODESBackground and Applications
Standard push test
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150
250
250
150 150260
Cover 15
P
PRk
Load
perstudP
(kN)
Slip (mm)u
6 mm
EUROCODESBackground and Applications
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
EUROCODESBackground and Applications
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
EUROCODESBackground and Applications
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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http://www.access-steel.com/