F. Mehri - Department of Civil Engineering, University of Bonab, Bonab, East Azerbaijan, Iran
S. Mollaei - Department of Civil Engineering, University of Bonab, Bonab, East Azerbaijan, Iran
E. Noroozinejad Farsangi - Faculty of Civil and Surveying Engineering, Graduate University of Advanced Technology, Kerman, Iran
M. Babaei - Department of Civil Engineering, University of Bonab, Bonab, East Azerbaijan, Iran
F. Ghahramani - Department of Civil Engineering, Urmia University, Urmia, Iran

Various mechanical and geometrical parameters have different effects on the isolation system's performance. Thus, a sensitivity study of the isolated structures' behavior is an essential matter. In this regard, the isolation systems should be designed using optimization approaches to consider the effects of the different factors. In this study, the optimal design of the lead rubber bearing (LRB) seismic isolation was conducted by considering mass irregularity and near-fault seismic excitation effects. Also, sensitivity analysis of the behavior of the considered isolated buildings was implemented concerning the mechanical parameters of the LRB system. A nonlinear time history dynamic analysis was used here, and the design optimization of the LRB isolator was programmed using the newly introduced grasshopper optimization algorithm (GOA). The main purpose was to investigate the ability of the GOA to optimize the design parameters of the LRB-isolated frames. The results proved the desirable ability of the GOA to solve optimal design problems for isolation systems. Also, the sensitivity analysis of the seismic behavior of LRB base-isolated structures showed that the yield base shear index had the most important effects. Also, the mass irregularity parameter showed a negligible influence.

Lead Rubber Bearing Isolator, optimization, Mass irregularity, Near-fault earthquake