Optimal single concave sliding device properties for isolated multi-span continuous deck bridges depending on the ground motion characteristics

The present study investigates the analysis of the optimal friction coefficient with respect to the seismic performance of isolated multi-span continuous deck bridges, equipped with single concave friction pendulum (FPS) isolators. A six-degree-of-freedom system is used to model the structural system and the FPS friction property is described by means of a law that considers the dependency on the velocity. The equations of motions have been implemented in nondimensional form by considering the peak ground acceleration-to-velocity ratio (PGA/PGV) and the peak ground acceleration (PGA) as ground motion parameters for two different sets of seismic records: near-fault and far-field inputs. In addition, different bridge models are considered for various parameters (i.e., pier period, deck period, friction coefficient and mass of the structural system). The results show the effectiveness of the PGA/PGV ratio within the proposed nondimensionalization together with the existence of an optimum value of the friction coefficient that minimizes the nondimensional response of the pier. At the end, a linear regression expression is presented with the aim to compute the optimal value of the normalized friction coefficient as a function of the deck period and PGA/PGV ratio, which can be used in the preliminary phase to design the FPS bearings. Additionally, a multivariate non-linear regression expression is also provided to evaluate the pier response.