Effect of System Parameter Uncertainties in Response Mitigation of SMA-FPS Isolated Building Under Seismic Excitation

The performance of base isolated structures under seismic excitation is mostly studied considering deterministic system parameters. Neglecting the uncertainties in system parameters can result in the underestimation of the responses which may lead to unsafe design of the isolation system. In this study, the response of isolated building using shape memory alloy with friction pendulum system (SMA-FPS) is optimized considering random system parameter uncertainties under stochastic seismic excitations. The system parameters such as stiffness, damping ratio of the superstructure, frictional coefficient of the isolator, stiffness of FPS, SMA and seismic excitation properties are considered as random variables. Sensitivity analysis is carried out to determine the influence of each uncertain system parameters. Frictional coefficient and transformation strength of SMA are the critical design parameters that affect the SMA-FPS isolation system. Further, these parameters are taken as design variables in the optimization study, accounting for uncertainties to show the impact of the behaviour of SMA-FPS isolation system. A five-storey building with the SMA-FPS as the base isolator is taken for the analysis and the optimization is performed using genetic algorithm considering root mean square acceleration (RMSA) as objective function. The result shows that the SMA-FPS isolated system undergoes a noticeable increase in unconditional response in terms of top storey RMSA, top storey root mean square displacement (RMSD) and RMSD of isolator due to uncertainties in system parameters than deterministic responses.