Comparative Study Of Elasto-plastic Seismic Analysis Methods For Bridges

Due to the suggestion of ductile seismic design method,structural elasto-plastic seismic analysis has been in extensive attention.Structural elastoplastic seismic analysis methods mainly include dynamic time history method and equivalent linear elastic analysis method.The dynamic time history method is a relatively accurate calculation method.But because its calculation is relatively complex and timeconsuming,the calculation accuracy depends largely on the selection of seismic wave and damping parameters.At the same time,each calculation can only get a sample of the random seismic response of the structure,affecting the practicability of the method.Therefore,for a long time,a lot of research has been carried out on the method of equivalent elastic analysis for researchers at home and abroad,in order to get more simple and convenient analysis methods.The equivalent linear elastic analysis method is based on the equal displacement principle and equal energy principle in structural dynamics.It corrects the elastic seismic displacement response of the structure to represent the nonlinear seismic displacement response of the structure.The method is simple and easy for engineers to master.However,the application of the equivalent linear elastic analysis method in the seismic analysis of bridges is not enough,especially the domestic research work in this area is very few.The equivalent linear elastic analysis method including single mode response spectrum method and multi-mode response spectrum method.The seismic design code for bridges in China and abroad for the bridge could satisfy certain conditions and relatively simple rules,which is defined as regular bridge and its seismic response is mainly controlled by the first mode.The Guidelines for Seismic Design of Highway Bridges(JTG/T B02-01 2008)reference to the relevant codes abroad,defining the regular bridges.According to the certain code,for the regular bridge,we can use seismic spectrum analysis of single mode response and other bridges should be on nonlinear dynamic time history method.In the revision of the Guidelines for Seismic Design of Highway Bridges(JTG/T B02-01 2008),we hope to expand the application scope of the equivalent linear elastic analysis method,and expand the multimodal response spectrum method to the seismic analysis of irregular bridges,so that we need to study its applicability.This paper,taking the opportunity of revising the new code,makes a preliminary study of some of the contents of the revision.The main research work of this paper is as follows:(1)The calculation thinking and calculation steps of the pier column displacement ductility coefficient are combed,and the concrete calculation method and attention of the displacement ductility coefficient of the pier column are explained with the engineering example,which provides a reference for the revision of the new standard and the engineering personnel.(2)Combined with the engineering example,the equivalent linear elastic analysis method of conventional bridges is studied.The results show that most of the conventional bridges in China are basically consistent with the principle of equal displacement,that is,the seismic displacement considering the elastoplastic effect in the equivalent linear elastic analysis method does not need correction,only a few cases need to be corrected,and the correction is very small.(3)The applicability of the equivalent linear elastic analysis method(single-mode response spectrum method and multi-mode response spectrum method)is studied.in accordance with the requirements of the standard revision.The study shows that the equivalent linear elastic analysis method is applicable for most of the conventional bridges in China,and the single vibration response spectrum method is suitable for the calculation of seismic response of regular bridges,and the multi vibration response spectrum method is applicable to the calculation of seismic response of regular bridges and irregular bridges.(4)Taking a continuous rigid frame bridge in Southwest China as an example,the concrete calculation steps of the equivalent linear elastic calculation method proposed in the new specification are explained,and the strength checking of the bridge under the E1 earthquake action and the deformation checking calculation under the action of E2 earthquake are carried out in combination with the new regulation and batch manuscript.