The Effects of Near-fault Ground Motions on Optimized Triple Friction Pendulum in Asymmetric Superstructures

Abstract

The effect of near-fault ground motions containing translational and rotational components is investigated by considering the analytic seismic response of a stiff single-story base-isolated asymmetric superstructure with triple friction pendulum bearing (TFPB). Firstly, six asymmetric base-isolated structures instrumented by optimum TFPBs were exposed to translational components of near-fault excitations with wide ranges of pulsive periods. Next, four single objective functions as target responses (including top floor absolute acceleration, maximum inter-story drift, base shear of structure, and isolator displacement), as well as a combined fitness function as a performance function, were determined to consider all the seismic responses simultaneously. Hence, the optimum design variables of TFPBs (including curvature radii, displacement capacity, and friction coefficient) were calculated using the Genetic Algorithm (GA) to minimize the fitness and performance functions separately for each defined eccentricity. Finally, the structural behavior in the presence of mass eccentricity on the optimum selected TFPB under transitional and transitional-rotational components was explored for a more careful comparison. Also, fifteen combinations of translational-rotational components were employed for a comprehensive investigation. The results demonstrate that roof acceleration could be increased by about 7.5% when mass eccentricity and rotational components are present at the same time.