Research On Evaluation Of Seismic Performance Of Curved Girder Bridge Based On Pushover

Static elastoplastic(Pushover)analysis is one of the most commonly used seismic analysis methods.Its calculation process is simple and accurate.It has been widely used in the evaluation of the seismic performance of bridge structures.Most of the existing studies focus on straight bridges,and the problem of the most unfavorable angle in Pushover analysis of curved bridges needs to be resolved.This paper takes a curved girder bridge in an actual project as the analysis object,defines eight lateral force angles,compares the yield displacement and ultimate displacement of the equivalent double-broken line capacity curve at different angles,and determines the most unfavorable angle of its Pushover analysis.On this basis,the seismic performance evaluation and fragility analysis of the full bridge are carried out.The main research contents and results are as follows:(1)Take the position of the left support of the first span as the starting point,connect to the middle and support positions of each bridge respectively,and obtain 8 different line segments as the longitudinal bridge direction,and the direction perpendicular to each line segment as the horizontal bridge direction.Finally,8 action angles are obtained.Under different action angles,the mode shape participation coefficients of curved beam bridges in various directions will change.When the mode shape lateral force load is adopted,the structural capacity curve will also change accordingly.(2)The equivalent yield displacement and ultimate displacement of the capacity curve of the bridge with five curvature radius under different angles of action are calculated.The study found that the displacement value changes regularly with the change of the angle of action,and reaches the minimum value at a certain angle,at which the bridge enters the failure state first.As the radius of curvature increases,the initial failure angle gradually increases.When the radius of curvature R=70m,120 m,170m,the angle of lateral force has a greater impact on the capacity curve.(3)Calculate the structural performance points under different angles of action through the ability spectrum method.The study found that with the increase of the angle of action,the displacement of the performance point gradually decreases,and the base shear force corresponding to this point gradually increases.When using the non-most unfavorable angle for Pushover analysis,the displacement capacity of the control points of the structure will be overestimated,and the internal force response of the structure under earthquake will be underestimated.The influence of different angles of action on performance points during the E2 earthquake was significantly greater than that during the E1 earthquake.(4)Different methods are used to calculate the seismic response of the structure,and multiple structural incremental capacity curves are drawn for comparison.The study found that for bridges affected by higher-order modes,the MPA method can be used to obtain a complete structural seismic response,and that only a single mode-shaped lateral force analysis will underestimate the response of some structural members.Incremental modal pushover analysis can well estimate the change of structural performance points with the intensity of ground motion,instead of tedious IDA analysis.(5)Fragility analysis is carried out from the angle of the most unfavorable action determined in this paper.The study found that the IDA curve obtained by Pushover analysis is roughly the same as the result under the time history analysis,and can predict the structural collapse point.By comparing the structural fragility curves of the four methods,it is found that the result of the MPA method is similar to the time history analysis.There are errors in the results under the main mode of lateral force and the uniformly distributed lateral force.