Serviceability limit state - Eurocodes

Control of cracking due to direct loading –
Verification by limiting bar spacing or bar diameter
G. Hanswille
Univ.-Prof. Dr.-Ing.
Institute for Steel and
Composite Structures
University of Wuppertal-Germany
A c
fully cracked tension stiffening
N s,2
-z st,s
-M s,2 -M s
ΔN ts
N s
z st
z st,a
a
-M a,2
+ =
ΔN ts
a
-M a
-M Ed
A s
A a
z a
-N a,2 -ΔN ts
-N a
The calculation of stresses is
based on the mean strain in the
concrete slab. The factor β
results from the mean value of
crack spacing. With s rm ≈ 2/3
s r,max results β ≈2/3 ·0,6 = 0,4
stresses in reinforcement
taking into account tension
stiffening for the bending
moment M Ed
of the quasi
permanent combination:
A
ρ
s
s = β =0,4
A
c
σ
σ
s
s
= σ
=
M
α
s,2
J
st
Ed
2
+
z
A
=
A
2
a
Δσ
st,s
J
J
2
a
ts
+
β
f
ρ
ct,eff
s
α
st
The bar diameter or the bar spacing has to be limited
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