Optimal design of single concave sliding bearings for isolated structures considering intermediate isolation degrees

This study describes the optimal properties of single concave sliding bearings employed for the seismic protection of elastic isolated structural systems under artificial earthquake excitations for intermediate values of the isolation degree. A particular nondimensional formulation of the governing equations of motion is employed to evaluate the seismic performance of equivalent two-degree-of-freedom models considering intermediate values of the isolation degree. The structural response is investigated in terms of superstructure displacement, equivalent damping factor and bearing force. Seismic excitations are modelled as time-modulated filtered Gaussian white noise random processes within the power spectral density method. The filter parameters, which control the frequency content of the random excitations, are calibrated to describe stiff, medium and soft soil conditions, respectively. Finally, the optimal values of the friction coefficient that minimize different percentiles of the superstructure displacements as a function of the intermediate values of the isolation degree and of the soil condition are numerically computed