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

5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES
Summarizing, we can say that the tests conducted on specimens COT9 and
COT10 confirm to have a very similar behaviour regardless of the presence of the
continuity plates. Both samples reached or nearly reached the conventional end of
test. The important piece of information for COT11 and COT12 mostly concerns
the type of failures occurred to these specimens. Hence, we have to judge whether
the displacement level reached for the specimens belonging to the C3
configuration (normally 8ey) establish a sufficient amount of ductility or it simply
shift the problem from the joint to another cross column section (the weakest one).
In fact, the connection panel with short profile encased, showed a good resistance.
Nonetheless, it may cause the brittle failure of the column before the requested
time, necessary to resist a seismic event.
5.7 Numerical analyses and validation of the mechanisms
In this section, the inelastic finite element (FE) analyses carried out by means of
the ABAQUS code (2003) are discussed. Thereby, the FE models were calibrated
and the stress and strain state of the aforementioned joints was simulated in the
monotonic displacement regime. Finally, by means of the analysis results a
validation of the proposed analytical formulas have been determined. The
modification in the dimension of some geometrical and mechanical parameters,
obtained through the elaboration of the numerical evidences, has permitted to
match better the experimental resistance of the joint subjected to shear loads.
5.7.1 FE Model of the specimens
Non-linear FE analyses of the tested specimens were carried out in a monotonic
loading regime. The analyses have been developed with 3D FE models. The used
model is reported in Figure 5.39 and represents the specimen COT9, endowed
with an HEB 140 steel profile. It is characterized by reduced integration eight-node
solid elements (C3D8R in the ABAQUS library). The FE analyses account for
material non-linearities through classical plasticity based on the Von Mises yield
criterion. Isotropic hardening is assumed for the analyses. The new model
Concrete in ABAQUS code has been used. This model permits to define the
correct strain-stress curve of the concrete both in tension and in the compression.
Moreover, for cyclic loading history, it is possible to define a degradation law for the
stiffness characteristics. The measured stress-strain properties of the different
materials (column flange, column web, stiffeners, rebars in the beam and in the
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