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

4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS
compared with the analytical prediction obtained from the model are shown. It is
evident that the theoretical and the experimental results do not agree closely. It is
interesting to underline that with a modified model in which the contribution of the
composite section is not taken into account, the analytical prediction agrees quite
well with the experimental results. This means that after the crushing of the
concrete the benefit composite action of the beam is lost and the joint behaves
simply as steel joint. Similar results are obtained for the exterior joint, as depicted
in Figure 4.36; however, different considerations have to be made.
COMPLETE JOINT MOMENT (kNm)
360
300
240
180
120
60
0
-60
-120
-180
-240
-300
Experimental
Analitical Model
-75 -60 -45 -30 -15 0 15 30 45 60 75
ROTATION φ (mrad)
Figure 4.36. Comparison between experimental and
numerical joint response of the CJ-EXT specimen
Under sagging bending moment, the analytical model is capable to predict
correctly the maximum strength of the connections, as shown in Figure 4.37, but it
is not able to predict the loss of strength due to the crushing of the concrete. Under
hogging bending moment the analytical model captures very well the behaviour of
the connection, in term both of stiffness and strength. The combination of the
response under sagging and of the response under hogging bending moment of
the specimen produces a different redistribution of force between connection and
web panel in shear, which the model is not able to reproduce. This fact can
explicate the differences in the global behaviour between experimental and
analytical results.
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