Earthquake response of seismically isolated bridges

A random vibration approach has earlier been used to perform earthquake response analysis of seismically isolated, multistory shear-type buildings. In this paper the method is modified for application to bridges that may be idealized as a simple beam supported by isolating devices. Response analysis of a seismically isolated structure is a nonlinear problem, where the nonlinear deformations are concentrated at the isolating bearings. Several approximations are needed when applying the random vibration theory. It is therefore considered necessary to compare the results with other methods. A numerical example shows that there is good agreement between the results obtained by the classical time-domain method and the random vibration approach. The random vibration approach is computationally more effective than the time-domain method.