Unseating Damages In Multi-span Simply Supported Bridges Under Canyon Topography

Many reasons and methods account for girders falling down in simply supportedbridges. While uniform excitation is much easier to use especially in the analysis ofshort-span bridges without regard to soil-bridge interaction. In this paper, dynamicresponses and seismic damage of girders falling down in multi-span simply supportedbridges under canyon topography are studied with finite element analysis softwareAbaqus.The total length of the bridge in this paper is100meters, therefore traveling waveeffect can be neglected. Soil-bridge interaction is considered. Principal work is donefollow(1i)n gT:aking Gaoyuan Bridge as an example, dynamic responses of multi-span simplysupported bridge under canyon topography are studied with seismic wave input of El-Centro,Ninghe and Qingping.(2) Unseating of Gaoyuan Bridge girders is studied based on the unseatingphenomenon during Wenchuan earthquake. This paper explains girders falling down froma new perspective that the soil behind Gaoyuan abutment is seriously damaged duringearthquake. Without the support of soil, the abutment breast wall is sundered during thepounding and then is pushed into the soil. This causes a larger relative displacement of thebridge girders to the piers and causes unseating damage of girders in the end.(3) Have studied the influence of girders falling down when coherent factors arechanged such as shear wave velocity of soil, friction coefficient of support, height ofgirders and so on. It shows that friction coefficient of support, stiffness of piers and shearwave velocity of soil influence girders falling down a lot, while height of girders, Elasticmodulus of girders and piers influence little.