Seismic reliability-based robustness assessment of three-dimensional reinforced concrete systems equipped with single-concave sliding devices

The aim of the study consists of evaluating the seismic robustness of a three-dimensional (3D) reinforced concrete (r.c.) structure equipped with single-concave friction pendulum system (FPS) devices by estimating the seismic reliability in its design life (50 years) of different models related to different malfunction scenarios of the seismic isolators. Among the uncertainties, the elastic response pseudo-acceleration corresponding to the isolated period is assumed as the relevant random variable and, by means of the Latin Hypercube Sampling technique, the input data have been defined in order to develop 3D inelastic time-history analyses. In this way, bivariate structural performance curves at each level of the r.c. structural system as well as seismic reliability-based design abacuses for the FP devices have been computed and compared to evaluate the robustness of the r.c. system considering different models related to the different failure scenarios analysed. Contextually, the seismic robustness of the abovementioned r.c. structural system has also been examined by considering both a configuration equipped with beams connecting the substructure columns and a configuration without these connecting beams in order to demonstrate their effectiveness in improving the seismic robustness in the scenario of a malfunction of a seismic device and provide very useful design recommendations for base-isolated structures equipped with FPS.