Experimental Study And Finite Element Simulation Of Interfacial Bond Behavior Of CFRP-Concrete Under Cyclic Loading

Carbon Fiber Reinforced Polymer has the advantages of fatigue resistance,good durability,light weight and high strength,so it is widely used in structural reinforcement engineering.The CFRP strengthening technology transfers the load through the interface bond stress.Therefore,the interface affects the efficiency of stress transfer between CFRP and concrete to increase the capacity of the structure.Many CFRP strengthened structures not only bear static load during their service,but also under cyclic load for a long time.The failure form of reinforced structure under cyclic load is usually not CFRP sheet being broken,but peeling failure along the interface.There is no obvious sign before failure,and the load during failure is often lower than the ultimate load under static load,which belongs to brittle failure and is difficult to detect,so it is harmful.In this paper,the interfacial bond-slip behavior of CFRP-concrete under cyclic loading is studied.The main research contents and results are as follows:(1)Study on interfacial bond behavior of CFRP-concrete under cyclic loading.Based on the static and fatigue tests of 18 double-sided shear specimens,the interface failure process and bond-slip relationship of CFRP-concrete under cyclic loading are analyzed and discussed.The results show that the interfacial bonding properties decrease with the increase of cyclic load times and stress level,and the peeling phenomenon of CFRP sheet appears earlier,and there is a linear relationship between peeling length and stress level.Changes in end slips occur in two phases: rapid growth stage and stable growth stage.The greater the maximum shear stress in the corresponding bond-slip curve with the higher the stress level.The interfacial residual bearing capacity of specimens under 2,000,000 cyclic loads is lower than that under static loading.The modified formulas of interfacial bond bearing capacity and effective bond length of CFRPconcrete considering the influence of stress level are put forward.(2)The performance degradation law of each component material of CFRP-concrete structure under cyclic load is quantified by formula,and the calculation of cycle times is simplified by the way of "cyclic jump".The method and process of simulating interface fatigue loading of CFRP-concrete are given based on ABAQUS finite element software,which provides a theoretical basis for follow-up finite element research.(3)Finite element analysis of interfacial bond behavior of CFRP-concrete under cyclic loading.The fatigue loading process of CFRP-concrete interface is numerically simulated by ABAQUS.The results show that the results under static load are in good agreement with each other.With the increase of the number of bicycles,the interfacial stress peak gradually develops to the free mass,and the initial crack initiation and interfacial cracking tend to the free end.The higher the stress level is,the closer the peak value of interfacial bond shear stress is to the free end,indicating that the higher the stress level is,the longer the stress transfer length is,and the closer the fatigue damage is to the free end.