Optimum Study of Friction Pendulum Isolated Building in Response Mitigation under Near Fault Excitation

Typically, near fault excitations are identified as large amplitude pulses with low frequency and short duration, showing the potential of damage in existing structures. The primary consequences of near fault excitations are fling step and forward directivity, which can impose unforeseen seismic demands on isolated structures. In this study, the behaviour of a five-storey building implemented with a friction pendulum system considering directivity and fling motions, is investigated. The governing equation of motions is derived and solved using Newmark beta method. Parametric studies and optimal analysis are performed for the base isolated building for different structural parameters under far fault, forward directivity and fling step motions. Moreover, the behaviour of base isolated building under seismic excitations with directivity and fling step pulses are significantly amplified when compared with far fault excitations. The gradient-based optimization technique is used to acquire optimal parameter of friction pendulum system. The frictional coefficient is considered as design variable to minimize the acceleration at the top storey. The study reveals that the near fault excitation with fling step motions results in larger demands than forward directivity pulses.