Accelerated Test And Damage Mechanism Of RC Beams Strengthened By CFRP Under Coupled Loading And Hydrothermal Environment

With the widely apply of carbon fiber reinforced polymer(CFRP)in strengthening technology in civil engineering,the durability of CFRP reinforcement structure in service has encountered severe environment problem,especially the interface of CFRP and concrete bonding performance under hydrothermal environment drawing wide attention from scholars at home and abroad.And the CFRP strengthening RC beam performance has significance and engineering application value.Based on the Major National Natural Science Foundation for Research Instrument Development of China(Grant No.11627802),this essay explored the RC beam strengthened by CFRP under the coupling of hydrothermal environment and load with the accelerate test methods,and revealed the damp and hot erosion damage mechanism of CFRP and concrete interface,coupled loading and hydrothermal environment analysis influence law of RC structural behavior of reinforce in CFRP.The main research contents and conclusions are shown as follows:The natural environment of Chongqing area and survey of the corresponding hydrothermal environment spectrum,determine the value of the temperature and humidity in the accelerated test,using the equivalent relation to hydrothermal environment spectrum parameters are reduced,it is concluded that the acceleration test21.66 day is equal to the natural erosion under hydrothermal environment 1 year the equivalent relationship,and make the load coupling CFRP strengthening RC beams under the action of hydrothermal environment accelerated test methods.Through the accelerated test in hydrothermal environment,it is found that the failure mode of CFRP positive tensile bond strength test blocks after hydrothermal erosion gradually changes from the cohesive failure of concrete to the adhesion failure between the adhesive layer and concrete,and the positive tensile bond strength decreases linearly with the increase of erosion time.CFRP strengthened RC beams with the increase of the length of the coupled loading and hydrothermal environment will form by central stripping,stripping to end interface and damage will speed up the test and natural exposure test,accelerated test and natural exposure test damage equivalence relation,the damage to the relationship and the equivalent accelerated test results,the reliability of the accelerated testing proves that the equivalent relationship.The hydrothermal environment is the main reason of the CFRP strengthening RC structural behavior to reduce the CFRP and concrete interface layer under the action of hydrothermal,occurred hot oxygen aging and hydrolysis aging,the interface of CFRP and concrete bonding ability is abate,CFRP can effectively participate in force,and the load coupling will accelerate interface performance degradation,the CFRP strengthening RC structural behavior is further reduced.A finite element model was established to simulate the interface performance degradation of CFRP and concrete under hydrothermal environment,the load and displacement curves of the finite element simulation results were similar to those of the test results,and the maximum error of ultimate bearing capacity was 5.2%.According to the damage degree of CFRP and concrete interface,the interfacial tangential yield stress and other related parameters in the finite element are changed,and the reinforcement effect of CFRP and concrete interface under different damage degree is simulated,so as to achieve the purpose of predicting the life of RC beam strengthened by CFRP.