Research On The Seismic Performance Of Thin-walled Hollow Piers Based On Vulnerability Analysis

In recent years,In recent years,hollow thin-walled bridge piers have been widely used in the southwest of China due to their light weight,material saving and superior seismic performance.How to ensure that bridge structures can operate reliably and safely after earthquakes and better perform their functions has become a key concern for the engineering community.The research on the seismic performance of hollow thin-walled piers with different hollow coefficients of cross-section is of great significance in reducing the direct damage caused by earthquakes and the secondary disasters caused by the paralysis of the bridge road network,as well as reducing the economic losses caused by earthquake disasters.Through literature research,the current status of research on seismic resistance and vulnerability analysis of bridges at home and abroad is summarised,and research progress on seismic research methods,damage assessment guidelines and damage parameter indicators of bridge structures is briefly introduced.In order to investigate the influence of height to width ratio,reinforcement ratio and hollow section factors on their seismic performance,section hollow coefficients are introduced to describe the influence of the hollow part of the section,and four sets of hollow pier models with different section hollow coefficients are established using the finite element software Open Sees for numerical simulation and analysis.The main research content of the thesis includes the following aspects.(1)A brief introduction to the modelling method and material model,the solid rectangular pier of reinforced concrete was established according to the data published by the structural tests of the pier and column of Tsinghua University,and the low circumferential reciprocal numerical simulation analysis was carried out.The numerical simulation results are compared with the experimental results to verify the applicability of the Open Sees modelling method and material model.By comparing the hysteresis curves of different cell types and cell division numbers,it is verified that the multi-unit stiffness method can effectively fit the hysteresis performance of the pier structure.This provides a theoretical basis for the subsequent modelling analysis of hollow thin-walled piers.(2)The Pushover analysis method is used to obtain four sets of basal shear-displacement curves for rectangular hollow piers with section hollow coefficients ranging from 0.2 to 0.8 respectively,and to investigate the effects of section hollow coefficient,pier height,section hollow type and longitudinal reinforcement rate on their seismic performance.The study shows that in the study of the seismic performance of thin-walled hollow piers,not only the effects of pier height and longitudinal reinforcement ratio should be considered,but also the effects of section hollow coefficient and section hollow type should be taken into account.Comprehensive hollow piers deformation performance and load-bearing capacity,the proposed interval of section hollow coefficient.(3)The hollow thin-walled piers that meet the recommended range of hollow section coefficients are selected for incremental dynamic analysis(IDA,Incremental Dynamic Analysis),and IDA curves are used to describe the relationship between peak displacement and ground shaking intensity.By comparing the IDA curves under different ground shaking effects,the seismic performance of hollow thin-walled piers with different hollow section coefficients and different hollow section forms is further analysed.It is found that the hollow section coefficient has a greater influence on the seismic performance of hollow piers.(4)Based on the numerical simulation results of Pushover and IDA analysis,a new composite damage index that takes into account the influence of section hollow coefficient on the seismic performance of hollow piers is proposed,and hollow thin-walled piers with reasonable section hollow coefficients are selected for vulnerability analysis and vulnerability curves are drawn.By comparing the single damage parameter index considering only the displacement of the top of the pier,the applicability and feasibility of the composite damage parameter index of hollow piers combined with the hollow coefficient of the section are judged.