Study On Durability Of CFRP Reinforced High Strength Concrete Beams Under Load And Hygrothermal Environment

With the rapid progress of economy and technology of China,the application ofhigh-strength concrete structures has become increasingly widespread.Due to environmental aging and other effects,the reinforcement of concrete structures has become increasingly prominent.In recent years,carbon fiber-reinforced composite materials(referred to as CFRP)have been broad application prospects in the field of reinforcement and repair of concrete structures because of their excellent properties.In summer,CFRP-reinforced concrete structures in most parts of China are not only subjected to continuous load but also in hygrothermal environment,which affects the performance of the reinforced structures.Therefore,it is of great theoretical value and practical significance to study the durability of CFRP-reinforced high strength concrete structures under the action of the loaded and moist heat environment.Relying on the National Natural Science Foundation of China(51378089),a total of 16 test beams were produced in this paper.Self-designed load-bearing devices were used to hold the reinforced beams and perform hygrothermal aging tests.The load-carrying grades of the specimens were 0%,30% and 60% of the ultimate bearing capacity of the unreinforced test beams,and the relative humidity of the hygrothermal environment was 95%,and the temperatures were 20℃,35℃ and 50℃ respectively.At the same time,the corresponding theoretical analysis and numerical simulation studies were carried out to study the influence of holding and hygrothermal environment on the performance of CFRP-reinforced high-strength concrete beams.The main conclusions of the study are as follows:Both the continuous load and the hygrothermal environment have an adverse effect on the performance of the reinforced beam.Under the same load level,the higher the temperature of the test beam subjected to the hygrothermal environment,the higher the degree of reduction in the mechanical properties of the ultimate bearing capacity,bending stiffness,etc.,and the higher the carrying level in the same temperature and humidity environment.Deterioration of test beam performance.With the increase of the holding level and the temperature of the hygrothermal environment,the peeling and breaking interface of the reinforcement beam gradually shifts from the concrete protection layer to the resin layer.The main reason for the decrease in the performance of the reinforced beams is due to the negativeinfluence of the carrying load and the hygrothermal environment on the CFRP-concrete bond interface.For the stripping damage caused by bending cracks and flexural-shear cracks in the middle section,a reasonable calculation model of the bearing capacity was selected and revised,and the environmental impact factors for the calculation of the bearing capacity of the reinforced beams were proposed.The finite element software was used to establish the three-dimensional model of the reinforced beam,and the four-point bending test of the reinforced beam subjected to different hygrothermal environments was simulated.The simulation results were compared with the experimental results,and the rationality of the model was verified,and the effect of the hygrothermal environment was concluded.Deterioration of CFRP strengthened beams.