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

4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS
account inelastic phenomena. The design is such that the joint behaviour is
governed by ductile components: the end plate and column flange under bending;
the column web panel under shear; and the concrete-slab rebars under tension.
More specifically, in the case of hogging moment, the connection is governed by
the rebars under tension. In this case, the bond between rebars and concrete limits
the yielding between the cracks, so that the total elongation can be evaluated as
the sum of the strains of the rebars near the cracks (ECCS-109, 1999). Therefore,
the joint rotation results to be
∆
φU
=
D + D
U, S, Tot
S R
( 4.24 )
where ∆U,S,Tot is the total elongation capacity of the rebars, Ds is the height of the
steel profile and DR the distance between the edge of the upper flange and the
centroid of the steel reinforcements.
Conversely, in the case of sagging moment, the rotation of the joint is determined
by the capacities of the column flange and of the end plate on an experimental
basis (Bursi et al., 2002). As a result, the total rotation of the joint reads
∆U,
S
φU
=
D + D
S C
( 4.25 )
where ∆U,S is the total displacement of the T-stubs, Ds the height of the steel profile
and DC the distance between the edge of the upper flange of the steel profile and
the centroid of the concrete slab. The joint response is also governed by the
deformational capacity of the web panel under shear forces. Thus, in applying the
component method in order to account for such rotational capacity, we limited the
maximum rotation to 30 mrad.
0.5L
δ
0.5L
Figure 4.14. Deformed configuration of a sub-frame
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