Optimal design of the seismic protection system for isolated bridges

Aim of the paper is the definition of optimal design parameters characterizing the isolation system of a bridge, both in the case of elastomeric (VI) and sliding bearings (SI), having viscoelastic or rigid-plastic behavior, respectively, installed between the piers and the deck. The problem is treated by means of an analytical approach. Using the frequency response analysis, a simple procedure is proposed to determine the optimal value of the viscous coefficient or the yield displacement of the isolators. The adequacy of the proposed procedure is finally verified through time-history analyses performed on a practical case under natural earthquakes.