Earthquake-resilient RC buildings with steel-concrete trussed beams and friction dampers

This study investigates the effects of friction damping devices in the structural joints of RC buildings endowed with semi-prefabricated hybrid beams and traditional RC columns. The beams are made with a steel trussed skeleton welded to a bottom thin plate, which is finally completed on-site by casting a concrete core. These beams have been widely adopted in both civil and industrial buildings also in seismic areas for several decades. Therefore, it is essential to approach new design strategies for the mitigation of the seismic effects. To this scope, the adoption of friction damping devices is discussed here; their effects are analysed when dampers are placed at Beam-to-Column Connections (BCCs) and Column-Base Connections (CBCs). With reference to the friction devices placed at BCCs, the efficacy of two different proposed solutions is shown. The first solution is characterized by a friction device with curved slotted holes, while the second solution consists in the adoption of curved slotted holes again, in presence of added perfobond connectors. Then, a CBC are studied, namely a self-centering system with friction pads and preloaded bolts. The analyses are conducted by modelling the structure using the Finite Element Method (FEM). FEM models are created first to simulate the monotonic and cyclic response of the damping devices at the joints. Then, the seismic response of an ideal 2-storey RC frame is simulated by means of pushover analyses and non-linear time history analyses. The main results show that, for BCCs, the solution with curved holes and perfobond connectors is the most effective in preventing beam, column and joint from damage and it is suitable for exhibiting adequate dissipative capacity ensured by flexural behaviour dominated by wide and stable hysteresis loops. On the other hand, for CBC, the results show that the self-centering friction devices effectively limit both peak and residual drifts, avoiding column-base plasticisation. Finally, experimental tests are conducted for the characterization of a friction material, and a BCC is tested under cyclic loading, showing promising performance in providing low-damage behaviour and good dissipation capacity.