RELIABILITY ANALYSIS OF BRIDGE MODELS WITH ELASTOMERIC BEARINGS AND SEISMIC STOPPERS UNDER STOCHASTIC EARTHQUAKE EXCITATIONS

This work investigates the dynamics and reliability of bridge systems with decks supported on columns through elastomeric bearings, while seismic stoppers are used to re- strain the motion of the deck during moderate to strong earthquakes. The dynamics of these systems during earthquake shaking can be simulated using models with piecewise linear elas- tic stiffness elements arising from the motion restrains between the deck and the columns due to the seismic stoppers. These bridge systems also involve strong inelastic behavior due to yielding of the columns under strong earthquakes. In order to gain useful insight into the be- havior of these systems, one degree of freedom systems with piecewise linear elastic stiffness characteristics are first analyzed and their behavior to earthquake-like excitations is investi- gated. The analysis is then extended to nonlinear systems with combined elements having piecewise linear elastic stiffness and inelastic force displacement behavior. Stochastic earth- quake excitation models are considered that simulate the strong pulse characteristics of near fault ground motions. The analysis is concentrated on probabilistic response spectra charac- teristics and the estimation of the sensitivity of these spectra to the values of system and load- ing parameters, such as initial modal frequency, size of gaps, excitation strength, duration and dominant frequency. The subset simulation method is used to efficiently estimate the probabilistic response spectra. In particular, the sensitivity of the probabilistic response spec- tra to the size of gaps between decks and seismic stoppers, affecting the behavior of the bridge, is explored and the performance of the bridge system is evaluated.