Analysis and modelling of the seismic behaviour of high ... - Ingegneria

4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS
F = f ⋅t ⋅ b
( 4.5 )
Rd1 cd slab c
where fcd is the strength of the concrete in compression, tslab is the thickness of the
concrete slab and bc is the column width. FRd1 is a rather concentrated force, which
is spread through the width of the slab and induces a transverse tension force Ft1,
which requires transverse anti bursting reinforcements. The spreading of this force
approximately takes place on a distance equal to the half effective width beff of the
slab and generates a transverse tension force Ft1, which can be computed explicitly
if beff is defined. Under seismic action l0 =0.7 is a reasonable estimate for the
length l0 of the beam between two points of moment reversal. Then according to
Eurocode 4 we obtain:
b = 2 ⋅ b = 2 ⋅ (0.7 )/ 8 = 0.175
( 4.6 )
eff e
The section of the steel needed for Ft1 should be realized with several re-bars
spread in a zone width equal to 0.6beff, starting at a distance hc of the column
flange, as illustrated in Figure 4.10. Normally, the amount of the required re-bars is
low and effectively already covered by the reinforcements needed for the gravity
and live load resistance.
Figure 4.10. The spreading of FRd1 and re-
bars As1 required by mechanism 1
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