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
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS<br />
When analysing <strong>the</strong> possible structural solutions, it becomes immediately evident<br />
that <strong>the</strong> use <strong>of</strong> composite columns <strong>and</strong> beams, by stiffening <strong>the</strong> structural elements<br />
<strong>and</strong> <strong>the</strong>refore significantly limiting second-order effects, can allow <strong>the</strong> erection <strong>of</strong><br />
buildings <strong>of</strong> considerable height without <strong>the</strong> need to use bracings. This advantage,<br />
combined with <strong>the</strong> introduction <strong>of</strong> partial strength joints, guarantees <strong>the</strong> formation<br />
<strong>of</strong> global dissipative frame mechanisms for <strong>seismic</strong> loadings, <strong>and</strong> it avoids<br />
unwanted storey or local mechanisms. If associated to suitable constructional<br />
solutions, such structural types can undoubtedly provide significant advantages in<br />
terms <strong>of</strong> both economy <strong>and</strong> performances (Braconi et al., 2003).<br />
Clearly, <strong>the</strong> choice <strong>of</strong> such structural systems in current design practice cannot<br />
leave out <strong>the</strong> preliminary evaluation <strong>and</strong> mechanical definition <strong>of</strong> <strong>the</strong> different<br />
possible connection types <strong>and</strong> <strong>the</strong> associated structural details.<br />
The present study illustrates <strong>the</strong> results <strong>of</strong> a European research (Ecoleader-ECSC<br />
joint Project) aimed at evaluating <strong>the</strong> rotational <strong>and</strong> dissipative capacities <strong>of</strong> a<br />
particular type <strong>of</strong> connection between a concrete partially encased column <strong>and</strong> a<br />
steel-concrete composite beam. The design <strong>of</strong> <strong>the</strong> connection, successively<br />
verified on <strong>the</strong> basis <strong>of</strong> experimental substructure tests, has been conducted by<br />
extending to <strong>the</strong> inelastic range <strong>the</strong> method described in Section 8 <strong>of</strong> Eurocode 4<br />
(Bursi et al, 2003). From <strong>the</strong> obtained knowledge on connection <strong>and</strong> member<br />
response, a numerical model <strong>of</strong> <strong>the</strong> prototype structure has been developed to<br />
examine its <strong>seismic</strong> <strong>behaviour</strong> through non-linear static (push-over) <strong>and</strong> dynamic<br />
analyses. Simulated ground motion time histories that match <strong>the</strong> design response<br />
spectrum were used in <strong>the</strong> dynamic analyses. This analytical work permitted to<br />
predict <strong>the</strong> performance <strong>of</strong> <strong>the</strong> frame <strong>and</strong> to propose an appropriate magnitude<br />
level <strong>of</strong> ground motion for <strong>the</strong> pseudo-dynamic tests on a full-scale model <strong>of</strong> a<br />
frame building expressly designed using <strong>the</strong> connections <strong>and</strong> structural details<br />
suggested by <strong>the</strong> results <strong>of</strong> <strong>the</strong> analyses.<br />
4.2 The Ecoleader-ECSC joint project<br />
The objective <strong>of</strong> <strong>the</strong> Ecoleader-ECSC joint project is to develop an experimental<br />
database on <strong>the</strong> <strong>behaviour</strong> <strong>of</strong> low-rise steel-concrete composite structures with<br />
partial strength semi-rigid connections subjected to gravity <strong>and</strong> lateral loads. In<br />
particular, information was needed on <strong>the</strong> <strong>behaviour</strong> <strong>of</strong> <strong>the</strong> beam-to-column joints<br />
<strong>and</strong> <strong>the</strong> structural overstrength exhibited by composite frames. Moreover, in order<br />
to evaluate <strong>the</strong> feasibility <strong>and</strong> effectiveness <strong>of</strong> <strong>the</strong> composite construction with<br />
101