SEISMIC RELIABILITY ANALYSIS OF 3D NON-LINEAR BASE-ISOLATED STRUCTURES WITH FPS

The aim of the study consists in evaluating the seismic reliability and life-cycle costs of a reinforced concrete 3D system isolated by FPS bearings with different isolated periods in order to evaluate the potential benefits provided by increasing values of the isolation degree. Assuming the elastic response pseudo-acceleration related to each isolated period and the coefficient of friction as random variables relevant to the problem characterized by appropriate probability density functions, the Latin Hypercube Sampling method has been adopted as random sampling technique in order to define the input data. Several 3D non-linear dynamic analyses have been performed considering both the vertical and horizontal components of each seismic excitation in order to evaluate the system performance. Thus, bivariate structural performance curves for each story of the superstructure and for the substructure as well as seismic reliability-based design (SRBD) curves for the isolation level have been defined for the different values of the isolation degree. Finally, the life-cycle cost analysis of the isolated system with different curvature radius of the FP bearings has been accomplished taking into account both the initial costs and the expected loss costs, due to future earthquakes, of the overall system during its design life (50 years) in order to evaluate the influence of the isolation degree on both the seismic performance and the total costs.