Test And Analysis Of Seismic Performance Of Railway Gravity Pier

At present,railway gravity piers are widely used in existing railway lines and railway lines under construction.The seismic design method for railway gravity pier is a hot spot and important direction.The reinforcement ratio of railway gravity piers is less than 0.5%,and their seismic performance may be different from that of reinforced concrete piers with enough longitudinal reinforcement.This study can provide a theoretical basis for the accurate analysis and rational design of railway reinforced concrete gravity piers in earthquake regions.In this paper,the quasi-static test of railway gravity pier is carried out,and the seismic performance of railway gravity piers under different longitudinal bar ratios and axial pressure ratios are studied by combining numerical simulation.The research in this paper was funded by the national natural science foundation of China(51768036)and the main research work is as follows:(1)Taking the gravity pier of railway simply supported beam with pier height of 10 m as the prototype,4 scale model with similarity ratio of 1/8 were designed,with longitudinal reinforcement ratio of 0.2% and 0.5%,and axial compression ratio of 0.04 and 0.06,respectively.The quasi-static test schemes of the pier specimen are formulated,including the axial pressure and horizontal load loading scheme of the pier top,the data acquisition scheme of the horizontal force and displacement of the pier top and the test flow.Then the specimens are made and cured,and the test is carried out after reaching the predetermined curing period.(2)In the test,the test data of different longitudinal bar ratios and different coaxial pressure ratios were collected and the test phenomena were recorded.According to the test phenomenon and data,the failure phenomenon and the change rule of seismic capacity with longitudinal reinforcement ratio and axial compression ratio are analyzed.The failure characteristics,seismic performance,ductile seismic checking index and practical seismic measures of railway gravity piers are summarized.The results show that with the increase of the longitudinal reinforcement ratio,the failure form of the pier specimen changes from the brittle bending failure to the bending failure with certain ductility characteristics.The results show that the length of plastic deformation zone of pier bottom increases and the cracking height of pier body increases.For the railway gravity pier,the change of reinforcement ratio and axial compression ratio has an influence on its seismic performance,and the increase of reinforcement ratio is more obvious to its seismic performance.The horizontal bearing capacity,lateral stiffness,displacement ductility coefficient and energy dissipation capacity of the pier specimens are significantly increased with the increase of the longitudinal reinforcement ratio,while the residual displacement index is significantly reduced.Increasing the axial compression ratio only contributes to the horizontal bearing capacity and lateralstiffness of the specimen.The ductility coefficient of allowable displacement of pier is 4 and the allowable displacement ductility coefficient of a pier with a longitudinal reinforcement ratio of 0.5% is suggested to be 4.8.The allowable displacement ductility coefficient of a pier with a longitudinal reinforcement ratio of 0.2% to 0.5% can be interpolated between the allowable displacement ductility coefficient of a pier with a longitudinal reinforcement ratio of 0.2% and a longitudinal reinforcement ratio of 0.5%.(3)Based on the OpenSEES finite element software,the numerical model of railway gravity pier specimens is established by using the fiber beam-column element.The results show that the numerical model can correctly simulate the displacement ductility and peak bearing capacity of the specimens.On this basis,using the correct finite element model,the longitudinal bar ratio and shear span ratio of the railway bridge pier specimens are analyzed.The results show that increasing the longitudinal reinforcement ratio,displacement ductility coefficient and horizontal bearing capacity of the model are all improved,which is beneficial to the seismic resistance of the pier.But the high longitudinal reinforcement ratio has little effect on improving the seismic performance of the pier.The pier model with shear span ratio?3 has the characteristics of ductility failure,and appropriate increase of shear span ratio is beneficial to ductility seismic resistance.However,when the shear span ratio is greater than 4,the horizontal bearing capacity of the pier decreases greatly and the displacement ductility coefficient does not increase significantly.