Optimal DCFP bearing properties and seismic performance assessment in nondimensional form for isolated bridges

The study analyzes the influence of double concave friction pendulum (DCFP) isolator properties on the seismic performance of isolated multispan continuous deck bridges. The behavior of these systems is analyzed by employing an eight-degree-of-freedom model accounting for the pier flexibility in addition to the rigid presence of both abutment and deck, whereas the DCFP isolator behavior is described combining two single FP devices in series. The uncertainty in the seismic input is taken into account by considering a set of nonfrequent natural records with different characteristics. The variation of the statistics of the response parameters relevant to the seismic performance of the isolated bridges is investigated through the proposal of a nondimensionalization of the motion equations, with respect to the seismic intensity, within an extensive parametric study carried out for different isolator and bridge properties. Moreover, two cases related to different ratios between the sliding friction coefficients of the two surfaces of the DCFP devices are analyzed with the aim also to evaluate the corresponding optimal values able to minimize the seismic demand to the pier. In this way, all the presented nondimensional results are useful for the preliminary design or retrofit of multispan continuous deck bridges, isolated with DCFP devices, located in any site and in relation, especially, to the seismic ultimate limit states.