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