Seismic response of RC frames with HSTC beams endowed with friction damper devices

Abstract

The aim of this work is to compare the seismic response of RC frames built using Hybrid Steel-Trussed Concrete Beams (HSTCBs) whether or not equipped with friction damper devices installed at the beam-to-column joints. Due to their small depth-to-span ratios, HSTCBs usually lead to a large amount of rebar within the beam-column joint, potentially reducing its cyclic performance. Therefore, the adoption of a friction system at the beam-tocolumn joint provides two main advantages, i.e. limiting the shear forces, and thus the potential damage, in the panel zone thanks to the increasing of the bending moment lever arm, and assigning to the device the task of dissipating the incoming seismic energy, thus preventing damage to the end sections of the beams. The seismic response of traditional and innovative r.c. frames is computed by means of non-linear time history analysis, taking into account the degrading phenomena, both in terms of stiffness and strength, which are observed in beam-column joints when subjected to cyclic actions. The cyclic behaviour of the beam-column joint of the traditional frame is tuned on the results of cyclic test on a full scale beam-column joint subassembly. The results highlight that RC frame endowed with friction devices provide structural performance consistent with design forecasts, i.e. beam end sections with a nearly-elastic behaviour, panel zones which experience negligible level of damage, comparable values of both maximum interstorey drift ratio and amount of energy dissipated with respect to traditional frame.