LAUSR

This paper presents a model for analyzing the seismic response of long-span bridges under oblique P-wave incidence. The model considers local topographical effects, soil nonlinearity and soil–structure interaction. Development of the model involves in application of the equivalent linear method to derive two-dimensional nonlinear free field site response, application of the equivalent load method for seismic wave input through viscous-spring artificial boundaries, and formulation of the dynamic response equation for the soil–bridge system. The two-dimensional nonlinear free field site response under oblique wave incidence is verified using a numerical example. The verification shows that the model is reliable and with high accuracy. The model is implemented into commercial software ANSYS for seismic analysis of a long-span bridge. The effects of angle of incidence, soil stiffness, local topography, and soil nonlinearity are explored by performing parametric studies. The parametric studies show that these factors may have significant impacts on structure response during earthquakes and shall be considered during seismic design of long-span bridges.