EARTHQUAKE RESPONSE OF SEISMICALLY ISOLATED BRIDGES

Response of seismically isolated bridge system under near-fault motions is investigated. The forcedeformation behaviour of the isolation system is idealised as bi-linear. The seismic response of isolated bridge system to normal components of two recorded near-fault motions in longitudinal direction is obtained by solving the governing equations of motion in the incremental form using step-by-step method. In order to study the effectiveness of seismic isolation, the seismic response of isolated bridge is compared with the corresponding response of non-isolated bridge (i.e. bridge without isolation devices). A parametric study is also conducted to investigate the effects of isolator parameters (such as stiffness and characteristics strength) on the effectiveness of seismic isolation for bridges. It is shown that the isolators are very effective in reducing the earthquake response of bridges. Further, the effectiveness of the isolation systems is significantly influenced by its stiffness and characteristics strength.