Study On The Seismic Performance Of Railway Gravity Pier Reinforced By Construction Joint

With the rapid development of railway construction in China,the seismic resistance of existing railway bridges can′t meet the current fortification standards.In the pouring process of the existed railway gravity piers,due to their large volume and immature construction technology,they often can′t be poured at one time,resulting in the formation of construction joint at the contact surface that has been poured successively.The existed seismic damage shows that the construction joint often becomes the weak surface of the pier,so the reinforcement of existed railway gravity piers with construction joint is of great practical value to reduce the seismic problems caused by construction joint.In this paper,the method of using basalt fiber reinforced polymer(BFRP)strengthens the existed railway gravity piers with construction joints is proposed,and the seismic performance of railway gravity piers with construction joint before and after reinforcement is studied by quasi-static test and numerical analysis.The main research contents of the paper are as follows:(1)The formation reasons of railway gravity piers with construction joint and the seismic damage characteristics of structures with construction joint are introduced.The seismic reinforcement methods of bridge piers and the research status of structures with construction joint at home and abroad are summarized,and the shortcomings of traditional reinforcement methods are described.According to the above reasons,the preventive seismic reinforcement method of the construction joint of piers by BFRP is proposed.(2)According to the reinforcement method of pier construction joint strengthened by BFRP,the quasi-static test is used to compare and analyze the failure characteristics,hysteresis curve,skeleton curve,horizontal bearing capacity,stiffness degradation and cumulative energy dissipation of railway gravity piers with construction joint,and the seismic performance of piers before and after construction joint reinforcement was evaluated.The results show that using BFRP strengthens construction joint of bridge piers can not only reduce the damage to the existed piers,but also effectively improve the seismic performance of the bridge piers.(3)The finite element model of pier before and after reinforcement was established by ABAQUS finite element analysis software.The material constitutive model,construction joint interface setting,meshing,element type,boundary conditions and load application method of the model are introduced.Besides,the numerical analysis results are compared with the quasi-static test results.The results show that the numerical model of pier can well simulate the force behavior of the piers under low cycle reciprocating load.(4)Based on ABAQUS finite element analysis software,the nonlinear finite element models of the reinforced front and rear piers under different parameter compression ratios and reinforcement ratios was established.The seismic performance of reinforced front and rear piers was studied by comparing the construction joint cracking displacement and cracking load,horizontal bearing capacity,peak load and peak displacement(horizontal displacement of the pier roof corresponding to the peak load)under different parameters.The results show that with the continuous increase of axial compression ratio and reinforcement ratio of pier models,The seismic performance indexes,such as peak load,peak displacement and cumulative energy dissipation,are gradually approaching before and after reinforcement,and the influence of construction joints on the seismic performance of piers is gradually reduced.(5)The Pushover analysis method was used to evaluate the seismic performance of the gravity prototype pier of railway with construction joint before and after construction joint reinforcement.According to the relevant calculation principles and steps of the Pushover method and the solution principle of the ability spectrum method,the capability spectrum curve of the prototype pier and the demand spectrum curve of the 7 degree zone and 8 degree zone under the design of earthquake are constructed.The results of capacity spectroscopy analysis show that the seismic performance of railway gravity pier with construction joint can be effectively improved by BFRP reinforcement.