Nonlinear Dynamic Analysis And Fragility Assessment Of Base-isolated Structure Supported On Rubber Bearing

Base-isolated structures are widely used in engineering.Less earthquake energy transmits into superstructure so that structure will experience less structural damages.Despite the extensive research conducted on base-isolated structures,limited research has been conducted on seismic fragility of isolated structures supported on rubber bearing.In order to assess seismic performance of isolated structures,a three-dimensional nonlinear finite element model is modeled after a typical multi-story building using OpenSEES program.Nonlinear dynamic response of base isolated structures supported on rubber bearing was discussed.Based on Incremental Dynamic Analysis,fragility curves are obtained.Seismic performance of isolated structures was assessed by fragility curves.The results indicate that:(1)Isolated structure shows lower structural acceleration and story drift ratio compared to fixed-base structure,but considerable amplification of structural displacement is observed.additionally,larger isolator displacements and story drifts are observed under near-fault earthquake excitations.(2)Isolated structures are expected to perform well under near-fault earthquake excitations,but bearing damage on isolated structure should be concerned.Hence there is a limit to only using story drift as a damage measure.(3)There is a difference between fragility curves obtained by Probabilistic Seismic Demand Analysis and Engineering Demand Parameter.Fragility curves obtained by PSDA may overestimate damage probability,which leads to waste in engineering.