Influence of Near Fault Records on the Optimal Performance of Isolated Continuous Bridges

This study aims at evaluating the optimal value of the friction coefficient in case of multi-span continuous deck bridges equipped with single concave friction pendulum devices. The bridge is modelled with a six-degree-of-freedom system considering the presence of the isolator on top of both the abutment and the pier. The friction pendulum device behaviour is modelled by including the dependency of the friction coefficient on the velocity. The equation of motions have been solved by adopting a nondimensionalization with respect to the peak ground acceleration-to-velocity ratio, which is a measure for the ground motion period. A parametric analysis has been performed by using different values for the friction coefficient, for the pier and deck periods and the masses of the deck and of the pier. The uncertainty in the seismic input is included by considering 40 near fault records. Finally, an optimal value for the friction coefficient able to minimize the substructure peak response is calculated as function of the peak ground acceleration-to-velocity ratio and the period of the deck.