Static Shear Performance And Residual Axial Capacity Of RC Bridge Piers Under Near-ground Lateral Loads

At present,the mileage of bridges and highways in our country,the number of vehicles,and the carrying tonnage are increasing,and the risk of cross-road reinforced concrete（RC）bridge piers being hit by vehicles and other impacts is increasing.Since the vehicle impact point is generally close to the bottom of the pier（ground）,the RC pier is prone to bottom shear damage.In recent years,a group of scholars have conducted a series of experimental studies on the resistance of RC bridge piers to vehicle impact,including real vehicle crash tests and indoor impact tests.However,these dynamic tests are costly,and it is difficult to obtain a large amount of structural damage data in one test.On the other hand,the pseudo-static test commonly used in the field of structural seismic resistance is mainly low-cycle reciprocating loading.The loading point is often located at the top of the column and the shear span is relatively large.This is quite different from the above-mentioned near-ground loading conditions of RC piers.In view of this,this paper conducted lateral static loading tests on the near-earth ends of 6 scaled RC model columns,aiming to study the characteristics of shear damage and the residual axial load-bearing capacity;and a series of experiments were carried out on this basis.Finite element analysis investigated the influence of parameters such as axial compression ratio,stirrup ratio,concrete strength and longitudinal reinforcement ratio on the failure mode,force and displacement relationship,cross-sectional deformation and crack width of RC columns.The test results show that:the test columns all have a clear main oblique crack at the bottom with an angle of about 30 degrees with the axis,and they will eventually slide along the main oblique crack under the action of axial pressure and fail;with the decrease of the hoop ratio With the increase of the initial axial pressure,the number of cracks in the specimen will gradually decrease,that is,increasing the hoop ratio can improve the resistance to shear cracking of the specimen.Increasing the hoop ratio and axial pressure can increase the shear bearing capacity of the column to a certain extent;the increase in the hoop ratio will significantly improve its shear deformation capacity and shear crack resistance,but the increase in axial pressure will reduce its shear capacity.Cut deformation ability.On the basis of the test,the applicability of the AASHTO model,the UCSD修正model and the Biskinis model to calculate the shear bearing capacity of the near-earth end laterally loaded specimens is discussed,and it is found that these three models are not applicable to this kind of working conditions.That’s great.In addition,the axial bearing capacity model of the RC column after shear damage has been revised,and the revised model calculation results are in good agreement with the test.The simulation results show that the finite element model can better simulate the force-displacement relationship and shear damage mode of the RC column;increasing the axial compression ratio,stirrup ratio,longitudinal reinforcement ratio and concrete strength can be improved to varying degrees The horizontal bearing capacity of the test piece.However,the model in this paper fails to accurately simulate the shear sliding of the RC column under axial pressure in the later stage,so the simulation of the residual axial bearing capacity is not accurate enough,and further corrections are needed in the future.In this paper,the horizontal shear performance and residual axial bearing capacity of RC columns with small shear span ratios are studied through static loading tests and finite element analysis,which will be used for subsequent damage assessment and performance-based design of RC columns under near-ground end loads.Lay a certain foundation.