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

6. SUMMARY, CONCLUSIONS AND FUTURE PERSPECTIVES
Subsequently, a new mechanical model of the partial strength beam-to-column
joint has been described. The model, which still relies on experimental data, is
capable of simulating the behaviour of the steel-concrete composite partial strength
joints subjected to monotonic loading. In detail, the model is capable of defining
yielding and failure evolution of different components. The component models of
the slab have indicated clearly that the compressive strut strength of the composite
slab bearing on the column flange depends on the shear stiffness of the column
web panel. Moreover, the activation of diagonal compressive struts on column
sides induced by transversal reinforcing bars is hindered by the direct bearing of
the compressive strut. Some force-displacement relationships provided by the
proposed mechanical model have been compared with analytical formulae and
current European standards.
The principles set forth have then been applied to the design of beam-to-column
joints and columns of a full-scale frame structure that was built and subjected to
pseudo-dynamic tests at the ELSA Laboratory of the Joint Research Centre in
Ispra. The construction of the full-scale structure proved that the construction of
steel-concrete composite structures with partial strength beam-to-column joints and
partially encased columns is highly efficient.
Pseudo-dynamic and cyclic test results confirmed that properly designed and
constructed partial strength beam-to-column joints and partially encased columns
without concrete in column web panels exhibit a favourable behaviour in terms of
energy dissipation, limited strength degradation and ductility.
6.2.3 Seismic behaviour of RC columns embedding steel profiles
This part of the Ph.D. thesis has been written with the intent of underlining the
importance of the studies conducted on Innovative Beam-to-Column Composite
Joints in order to provide the reinforced concrete structures of the necessary
amount of ductility in those critical zones usually strongly affected by the
occurrence of seismic events. The general recommendation is to reinforce some
strategic points of the building, as the joints of the 1 st storey, allowing in this
manner to save the structure from a global collapse due to localised brittle type of
failures. Both the solutions studied, with long and short steel profile encased in the
concrete column, as expected, revealed to be effective in order to greatly improve
the performance of the concrete members in terms of strength and ductility at large
deformations. In fact, it can be stated that also the short steel profile stump is able
to guarantee an adequate amount in terms of resistance and ductility at the joint
critical region, even if some inconveniences occurred in the column length between
the joint and the inflection point. It means that, a not accurate constructive process
248