Study On Seismic Damage Mechanism And Seismic Design For Highway Skewed Girder Bridges

So far,domestic and foreign scholars made a series of achievements in skew girder bridge,seismic response,seismic damage mechanism,seismic performance and other aspects through theoretical analysis,numerical simulation analysis and model test.However,there are still a lot of problems in the study of the seismic damage mechanism and the design of the skew bridge.On the basis of previous studies,taking the two span continuous skew bridge as the research object,comprehensive application of seismic simulation shaking table model test,based on the orthogonal test of SPSS program analysis method,based on OpenSees simulation analysis,and the seismic demand model establishment based on MATLAB2014.The seismic damage mechanism and seismic response of the skew bridge are studied deeply based on the above analysis method.The main contents are as follows:1.Experimental study on earthquake simulation shaking table model of skew bridge:Through the collection of skew bridge engineering examples,statistical analysis of the assignment rang of the main design parameters,and then the model of two span continuous skew beam bridges were designed.On the basis of Fuzhou University simulated earthquake shaking table system,packet making full bridge testing model and developing a series of experimental study about skew angle,axial compression ratio,slenderness ratio and reinforcement ratio and other parameters.Through this test,it would lay a solid foundation for the further understanding of the mechanism of the earthquake damage of the skew bridge.2.Research on finite element model of skew bridgeBased on the seismic response of the orthogonal test,the finite element model about the model test was established by using the finite element analysis software OpenSees,and the main beam and support the reasonable modeling method were discussed.Finally,an improved finite element model was proposed.The structural seismic response rules was obtained by the improved finite element model which was inputted three dimension ground motion.The finite element analysis results were compared with the experimental results,and the establishment of the accurate finite element model was verified.3.Study on seismic damage mechanism of skew beam bridgeThe OpenSees finite element model of single span simply supported skew bridge and two equal span continuous skew girder bridge were established respectively by using the improved finite element modeling method.The model considers the pounding effect.Studying the skewed girder bridge's seismic response about the effect of the expansion joints collision(longitudinal collision)and longitudinal impact combined with transverse block collision(bidirectional collision)with different parameters,such as earthquake ground motions,skew angle and height of piers.At the same time the damage mechanism of the bridge piers of skew beam bridge was studied.In the end the construction measures for the seismic resistance of skew beam bridge were established.4.Establish the multi phase seismic demand model of skew girder bridgeBased on the OpenSees finite element model of built in the fourth chapter,the probabilistic seismic demands of the single span skew bridge sample was calculated using the increment dynamic analysis(IDA)method by selecting 80 earthquake records at III site conditions.These demands were expressed in terms of four engineering demand parameters(EDPs),i.e.,skew girder bridge panel lateral displacement rate,longitudinal lateral displacement rate and block collision effect coefficient.The probability distributions of the EDPs were established at different IM levels.These studies provide reference for seismic response evaluation of skew bridge.