Multidimensional Seismic Vulnerability Analysis Of High Pier Bridge Considering Pile-soil Interaction

The bridge system is the most vulnerable nodal part of the transportation network to seismic effects,and its damage will cause damage or even paralysis of the whole transportation network,which constrains the post-earthquake repair and reconstruction work.It has been shown that the pile-soil interaction will prolong the self-oscillation period of the bridge system and affect the spectral characteristics of the ground shaking of the input structure,and the nonlinear permanent deformation of the soil will affect the displacement response results of the bridge.A large number of high pier bridges supported by pile foundations have been built in the western region of China,and the effect of pile-soil interaction on the seismic susceptibility of such bridges deserves attention.In order to study the influence of pile-soil interaction on the seismic susceptibility analysis of high pier bridge systems,this paper establishes an analytical model for high pier bridges with different pier-bottom constraints and different input ground shaking,considers the correlation of the response of different components in the bridge system through the Nataf transform and establishes a multidimensional seismic susceptibility curve for high pier bridge systems based on the multidimensional performance limit state function.The main work of this paper is as follows.(1)After studying and learning the previous modeling methods of pile-soil interaction and their advantages and disadvantages,it was decided to use a nonlinear p-y spring to simulate the mutual contact relationship between pile and soil,and to use the semi-infinite space model of site soil established by DEEPSOIL software to treat the selected bedrock ground vibration as the input load,so as to consider the filtering effect and amplification effect of soil on bedrock ground vibration.(2)A numerical model of a high pier bridge considering pile-soil interaction is developed using the OpenSEES platform by considering different pier-bottom restraint methods(pier-bottom consolidation and consideration of pile-soil interaction)and different input ground vibrations(ground vibrations filtered by site soil and ground vibrations not filtered by site soil).(3)The ground shaking loads with different treatments are input to the established high pier bridge model one by one after amplitude adjustment and the horizontal bidirectional nonlinear time response analysis is performed based on the incremental dynamic analysis method(IDA)to obtain the maximum seismic response data.(4)Based on the framework of multidimensional performance limit state theory analysis,the Nataf transform is introduced to consider the correlation between the response of different components of the bridge system,the transcendence probability of the high pier bridge system is solved using the first second order method of moments and the multidimensional seismic susceptibility curve is plotted,and the influence of several typical site conditions on the multidimensional seismic susceptibility analysis of the high pier bridge system is analyzed.The research results can provide a reference for the seismic design as well as construction of high pier bridges under adverse geological conditions in the western region.