Optimal performance of base isolated building considering limitation on excessive isolator displacement

The past studies on optimisation of isolation bearings emphasise on the allowable limit on the isolator displacement without incorporating it in the optimisation process. Large bearing displacement of the isolator during strong motion is often linked to isolator damage and pounding to adjacent units. The present study addresses the limitation on the excessive isolator displacement in the optimisation process of the isolator. It is intended not only to assure optimal performance in terms of vibration mitigation, but also to reveal the importance of constraining excessive isolator displacements. The stochastic response required for the optimisation study is evaluated through nonlinear random vibration analysis. The consistency of the optimal response behaviour obtained through stochastic optimisation is validated for recorded earthquake ground motions. A Lead Rubber Bearing (LRB), isolating a multi-story shear building is used to elucidate the effect of this constraint on the optimum parameters and system performance. The results clearly indicate the existence of significant disparities among the conventional unconstrained and the proposed constrained optimisation approach.