The seismic responses of the site with about 300-meter deposit are computed for Sutong Bridge in preliminary design phase.SR2D software package is used as the computational tool that is developed by our team.Traditional method analyzing the problem is one dimensional wave theory.Because the site on the Sutong Bridge is very complex and the span of the bridge is very long

the one-dimensional method cannot fully reflect the seismic response character of the site.The site seismic responses at eight bridge piers are found under the excitation of three seismic waves input at the bedrock for different cases.The effect of the seismic waves traveling along the bedrock surface is considered in the analysis.Some results of absolute accelerations and displacements at the site surface are listed in this paper.Furthermore

by using the response spectrum theory

the response spectra of seismic waves inputted is researched.Comparisons between the response spectra of seismic waves inputted and response spectra at bridge piers show that the peak values of response spectra become increasingly larger filtered by soil layer.From the computational results

it can be seen that the following factors have important effects on the site seismic responses: computational model of soil layer

geological and topographic condition of soil layer and traveling velocity of wave.If there is sloping river valley

the results are obtained from the simple model in which the site is simulated by horizontal layered uniform soil layer with coincident excitation are different obviously from the ones obtained from the precise model of the site.The seismic responses at some bridge piers are larger and others are smaller.As the effect of seismic wave traveling along the surface of bedrock has important influence on the ground motion at surface of site

for long-span structure

such as long-span bridge or giant gymnasium

it is essential to consider multi-supported excitation to get accurate seismic response.