Experiment And Simulation Of Residual Seismic Behavior Of Damaged Reinforced Concrete Columns

In order to study the residual seismic damage performance of a reinforced concrete column(RC column)damaged after bi-directional seismic excitation,a 1:1full-scale RC column specimen was designed,and the multiple usage structural tester of Hunan University(HNU-MUST)was used to load it.The quasi-static test of the seismic damaged specimens is carried out to measure the residual seismic performance after the earthquake,and a numerical simulation method for simulating the residual seismic performance of the seismic damaged column is proposed.The main research contents and conclusions of this paper are as follows:(1)In this paper,a full-scale RC column specimen is designed,and the substructure quasi-dynamic test is performed on the specimen to simulate the irregular earthquake damage.After the column was damaged in the test,a quasi-static low-cycle repeated loading test was designed to measure the residual performance of the earthquake-damaged column on the basis of the unreinforced seismically damaged column.The quasi-static test is kept under the same axial force as before the earthquake.The quasi-static test results of the specimen are analyzed and compared with the seismic performance of the column measured by the substructure quasi-dynamic test.The results show that the damage degree of the column specimen used in this test has reached the seismic loss level II at the end of the substructure quasi-dynamic test,but the subsequent residual performance measurement test of the seismic damaged column proves that it still retains a little seismic resistance.Under the same displacement level,the degradation trend of residual stiffness,residual strength and residual energy dissipation capacity during the post-earthquake loading process is the same as that before the earthquake,but the values are significantly reduced.Each damage index degrades rapidly with the increase of displacement,and when the horizontal displacement does not reach the peak displacement of the substructure pseudo-dynamic test,the damage degree has reached the level I seismic damage.Compared with the method of simulating earthquake damage by gradually increasing the horizontal displacement during the quasi-static test,this paper adopts the method of quasi-static reloading of a damaged column that has been subjected to quasi-dynamic loading of substructures.Through this method,the conclusion that the residual bearing capacity of the RC column is significantly reduced and the residual energy dissipation capacity is accelerated to degrade during the reloading of the RC column is obtained.(2)A new method for numerical simulation of residual seismic performance of components after seismic damage using Open SEES is proposed.After modeling the overall structure in Open SEES,the overall model is loaded with seismic waves.Extract the axial force time history and horizontal displacement time history of a bottom column which is required for the simulation.The axial force time history and horizontal displacement time history of the top of the column are connected in series with the preset post-seismic reloading path and then loaded as a complete path on a single column model to obtain the residual seismic performance of the component after seismic damage.This method can be used to evaluate the residual seismic performance of frame columns after experiencing earthquakes without demolishing the original earthquake-damaged building structures,so as to help assess whether the earthquake-damaged structures need to be reinforced or demolished for reconstruction.(3)Combined with the residual seismic performance test of the damaged column,the effectiveness and accuracy of the new simulation method are verified.This method can easily and accurately obtain the hysteresis curve of the component undergoing reloading after earthquake damage.It can reflect the residual seismic performance of seismically damaged components,so that the pre-earthquake damage can be included in the simulation process of post-earthquake loading.It can obtain more accurate residual seismic performance simulation results without quasi-static test of damaged column.