Research On Seismic Performance Of Railway Gravity Piers With Low Longitudinal Reinforcement Ratio On Shaking Table Test

With the rapid development of China's railway construction,the construction mode of "replacing road with bridge" has been widely used in railway engineering construction over the last few years.As an important component of the existing railway bridge,railway gravity piers with low longitudinal reinforcement ratio has many advantages,such as high stiffness and high weight,which can ensure the stability of the train in the high-speed driving process.Once the structure is damaged in the earthquake,it will bring unpredictable consequences.The current 06 edition of code for seismic design of railway engineering is mainly used for reinforced concrete piers with longitudinal reinforcement ratio higher than 0.5%,which lacks the guiding theory for seismic design of low longitudinal reinforcement ratio piers.In addition,for the study of seismic performance of less reinforced concrete gravity bridge piers,most scholars mainly use the quasi-static test or numerical simulation method,while the results of dynamic response of the structure in the actual earthquake are quite different from quasi-static test's.In order to ensure the applicability of railway gravity piers with low longitudinal reinforcement ratio in different seismic intensity areas,this paper discusses the seismic performance of piers with different reinforcement ratio on the shaking table test.The main research contents and conclusions are as follows:(1)Two bridge pier scale models with reinforcement ratio of 0.2% and 0.5% are designed and made which was designed according to the dynamic similitude law,was tested on theshaking table with unidirectional horizontal earthquake motion to analyze the response results of seismic parameters and observe the damage of the structure.The test results show that the structure has good seismic performance under the action of 7-degree rare earthquake,and the specimens with reinforcement ratio of 0.5% can withstand the action of 8-degree rare earthquake and maintain repairable state,which meets the requirements of the third-level seismic fortification in China.The specimens with reinforcement ratio of 0.2% show partial ductility after damage,and a through crack appears at the bottom of pier when they are finally damaged;the specimens with reinforcement ratio of 0.5% have better ductility,multiple cracks develop in the pier body when they are damaged,and the pier has obvious plastic hinge area.(2)The three-dimensional experimental model is established by OpenSees,and the numerical simulation results are coMPared with the experimental results.The numerical simulation results are close to the test results,and the error is within the acceptable range,which verifies the feasibility of the numerical simulation calculation for railway gravity piers with low longitudinal reinforcement ratio.(3)Four models with reinforcement ratio of 0.2%,0.3%,0.4% and 0.5% are designed.IDA method is used to draw the IDA curve of relevant parameters to study the whole process of structural damage in earthquake,the results show that the ductility coefficient increases linearly with the increase of reinforcement ratio.The performance level of pier structure with different reinforcement ratio is divided,and the performance level of structure is quantified based on displacement ductility coefficient.