Pseudo-Static Test Of Gravity-Type Piers Digging Foundation For Railway Bridges

In recent years,China’s high-speed railway bridge construction has developed rapidly,and the well-dug foundation piers have been used more and more in railway Bridges.Digging foundation is a kind of bridge foundation structure which is made of concrete directly after excavation of foundation pit by artificial or mechanical straight wall excavation.In this paper,the structural characteristics of the well-digging foundation and the seismic damage characteristics of the rigid foundation are summarized through the literature review of the existing well-digging foundation application.At the same time,the model is designed and made according to the structural characteristics of the foundation piers for digging well of railway bridge.Based on the pseudo-static test and finite element analysis,the seismic performance indexes such as hysteresis curve,skeleton curve,energy dissipation capacity and stiffness degradation of the model of the excavated foundation piers with a depth-to-width ratio of 1:0.67 were studied,and the seismic performance of the excavated foundation piers under the influence of different parameters was studied by finite element analysis.The main research work of this paper is as follows:(1)The development and current situation of seismic research on bridge foundations at home and abroad are summarized through reading relevant literatures.In the seismic research at home and abroad,more emphasis is placed on the experimental study of the seismic performance of concrete structures.The research on the relationship between structure and soil mainly focuses on the analysis of pile group effect.The research literature on the basis of digging well is relatively long.(2)Through consulting the literature on the practical application of the well-digging foundation,we found and summarized the shortcomings of the research on the existing well-digging foundation pier.There are seismic damage records about the well-digging foundation in many seismic data,but for the research on this structure,many literatures only introduce its application in practical engineering,and the research on the seismic performance of the well-digging foundation lags behind relatively.(3)In this paper,a test model of a gravimetric foundation for a railway bridge pier is designed and made to study its seismic performance.According to the field conditions in the laboratory,the scale ratio of the model is 1:8,and the depth-width ratio of the foundation is1:0.67.(4)Pseudo-static tests were carried out on the piers model of the excavated foundation to record the failure phenomenon of the piers model during the tests.After processing and analyzing the test data such as hysteresis and skeleton curve,the seismic capacity indexes such as energy dissipation capacity and stiffness of the piers model of the excavated foundation are obtained.(5)The finite element software ABAQUS was used for modeling calculation to obtain the seismic response of the well-excavated foundation piers under the same loading system as the test.The obtained calculation results were compared with the results of the pseudo-static test,so as to verify whether the calculation results of the model were reasonable and accurate.At the same time,the correct numerical model is used to analyze the four parameters,including pier height,foundation depth-width ratio,reinforcement ratio and superstructure mass,for the digging foundation model of railway gravity bridge piers.At the same time,the numerical model of pile foundation piers under the same site conditions is established to compare the seismic performance of the excavated foundation and pile foundation piers under the same loading system.