SEISMIC DESIGN OF HYSTERETIC DEVICES FOR RETROFITTING EXISTING RC STRUCTURES

Passive control systems through hysteretic devices represents one of the best technique for retrofitting, or upgrading, the numerous existing reinforced concrete framed buildings, located in Italy in areas with high seismic hazard and designed without an appropriate seismic detailing. These systems absorb the inertial actions in combination with the existing structure, increasing the stiffness of the frame and providing an additional dissipation of the energy by means of their ductility capacities to exhibit large inelastic deformations. The thesis deals with the design of dissipative buckling restrained braces (BRBs), in order to upgrade an existing building in L’Aquila. Specifically, it is used a procedure based on the results from pushover analysis considering as design parameter the maximum inter-storey drift properly chosen in order to avoid an excessive damage of the main structure. After the design procedure, the model of the building equipped with the BRBs is tested to verify the respect of the seismic performance. The behaviour of the upgraded structure is studied both through static nonlinear (pushover) analyses and nonlinear dynamic (time history) analyses using a set of several ground motion records compatible in average with the elastic design spectrum. Another important aspect that is taken into account is the influence of the infills on the design of the BRBs, comparing the response of the upgraded building with and without the presence of non-structural elements.