Seismic loads and response for continuous bridges

A number of highway bridges in the Tokyo and Osaka areas have been constructed on soft ground. If the stiffness of piers is increased then their weight also increases and this may cause some foundation problems. Bridges with some seismic-isolation devices can easily absorb earthquake forces. Therefore, in the seismic design it is very important to consider the reduction of interaction between the superstructure and substructure. The aim of this study is to investigate the seismic response of an existing three-span continuous bridge supported by thin-walled steel box piers. The problem is solved by the finite element method, using the Updated Lagrangian formulation in consideration of an elastic-plastic large displacement of steel piers and nonlinear characteristics of foundation. To increase seismic resistance, the steel bearings are replaced with rubber or seismic-isolation bearings. Also considered is the effect of the earthquake ground motion on the seismic response of the bridge structure.