A prediction of fault displacement and study of seismic response of suspension bridge across fault
Fault dislocation can lead to permanent ground rupture displacement and cause severe damage to bridge structures crossing fault.Accurate prediction of the permanent displacement caused by faults displacement is of great significance for assessing the seismic performance of cross-fault bridge structures.In this study,a high-precision model for predicting fault displacement based on BPNN(backpropagation neural network)was proposed.The model is used to generate artificial earthquake ground motions(referred to as cross-fault ground motions)by combining low-frequency and high-frequency components.The 538 m long-span steel truss suspension bridge crossing an active fault is taken as the research object,and the full-bridge calculation model considering pile-soil interaction was established using the finite element software of ABAQUS.Finally,the influence of fault rupture permanent displacement on the seismic responses of suspension bridges crossing faults was explored by studying the impact of fault location and fault-crossing angle on the seismic responses of the suspension bridge.The research results indicate that the proposed method based on BPNN can accurately predict the fault rupture permanent displacement caused by fault movement.Compared with existing regression formulas,this method has higher accuracy and provides a guarantee for artificially synthesizing fault-crossing ground motions.The relative position of the fault has a significant impact on the seismic response of the bridge structure.Compared with the effect of near-fault seismic motion,the tower base shear,bending moment,relative displacement,and torsional response of the suspension bridge under fault-crossing ground motions increased by 22.79%,154.1%,139.36%,and 265.48%,respectively.In addition,the fault-crossing angle also has a significant impact on the dynamic responses of the suspension bridge.The response is symmetrically distributed with a regular pattern at the crossing angle θ=90°.The maximum longitudinal displacement on the top of tower,tower bottom longitudinal moment,tower base longitudinal shear force,and tower base torsional moment all appear at θ=90°,with values of 0.81 m,282.45 MN∙m,3.96 MN,and 6.14 MN∙m,respectively.The results of this study can provide a simple and reliable method for artificially synthesizing seismic motion for seismic analysis of suspension bridges crossing faults and reveal the effects of fault-crossing angle and fault location on the seismic response of suspension bridges crossing faults.
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