Experimental Study And Numerical Simulation On Damage Behavior Of Concrete Short Columns Strengthened With HDC Under Small Eccentric Compression

As a new type of concrete material,high ductile concrete(HDC)has the most obvious advantages of high strength and good ductility,and has high corrosion resistance and damage resistance in a variety of external environments.It can improve the strength,stiffness and seismic performance of concrete structures.In many places in China,buildings are damaged to a certain extent due to earthquake effects and aging of concrete.Not only do various damaged buildings need to be repaired urgently,but they also need to be repaired and reinforced due to their service life and other problems,so in recent years there has been an increasing interest in the repair and reinforcement of damaged composite structures and durability.For the small eccentric compression members with obvious brittle characteristics,the damaged small eccentric concrete short columns are strengthened by increasing the section method by using the good ductility characteristics of HDC,and the effect after reinforcement is analyzed and studied.This paper mainly analyzes and studies the data of small eccentric compression columns through test proof and parameter simulation,puts forward the calculation method of foundation bearing capacity on the basis of analysis,and compares the simulation results with the test results.The latest research results are as follows:(1)In the test on HDC reinforced damaged small eccentric compressed concrete short columns,nine test columns were mainly designed to analyze the morphology,magnitude of com pressive bearing capacity and ductile deformation capacity of the specimens at the time of damage in terms of eccentricity distance and thickness of reinforcement layer,respectively.The test results showed that the eccentrically stressed columns reinforced with HDC materials had better ductility during damage.Compared with the unreinforced columns,the peak load is increased by 19%～63%,the displacement corresponding to the peak load is increased by 11%～44%,and the ultimate displacement is increased by 28%～71%;With the increase of the thickness of the reinforcement layer,the bearing capacity of the members is also increasing,and the mutual deformation coordination ability of the reinforcement,concrete and HDC of each column is better.(2)In this paper,the finite element numerical analysis software ABAQUS is applied to the small eccentric stress test after reinforcement.The results show that ABAQUS can better simulate the crack development and stress distribution of the reinforced specimen,and the derived data curve is similar to the test.On the basis of finite element analysis,the influence of each factor on the compression bearing capacity of the normal section of the member is judged by changing the original section size,concrete strength and eccentricity.Based on the original simulation,the influence of each factor on the compression bearing capacity of the normal section of the member is judged by changing the original section size,concrete strength and eccentricity.The results show and with the increase of the cross section,the concrete bearing capacity increases,when the concrete strength increases,the concrete short column peak load is also in the corresponding increase,the ductility has decreased.When the eccentric distance increases,the peak bearing capacity decreases significantly,and the deformation of the member when it is damaged increases significantly.When the eccentricity continues to increase,the phenomenon of bearing capacity reduction is more obvious.(3)In the calculation of small eccentric compression bearing capacity,considering the circumferential restraint effect of high ductility concrete wrapped in the outer layer on the concrete in the inner core area and the utilization rate of HDC reinforcement layer,a method of calculating the bearing capacity of HDC reinforced eccentric compression members is proposed,and the calculated results are compared with the test,and the calculated results are in better agreement with the test.(4)In this paper,ultrasonic detection technology is applied to detect the damage of concrete,and the damage model of concrete column is derived by calculating the sound velocity anomaly through the probability method,and the damage degree of concrete column is judged by calculating the accumulated damage value,and the calculation is basically consistent with the test.