Experimental Study On Reinforced Concrete Beams Strengthened With Prestressed CFRP Sheets

Externally bonded CFRP sheet is a new reinforcement technology for reinforced concrete structures.It has the advantages of light weight,high strength,good durability and easy construction and has been widely applied in various countries including China.However,due to the relatively late work of CFRP sheet,the high strength performance can not be effectively utilized and the utilization rate is relatively low.At the same time,only when cracks start to develop,CFRP sheets begin to be gradually stressed,and their service performance of reinforced components is limited.In the existing reinforcement,CFRP sheets is usually pasted with epoxy resin without reliable anchorage,resulting in easy peel failure of CFRP sheets.In the light of the characteristics of CFRP sheet material,this project has designed a set of CFRP tension device and anchorage device,and put forward the corresponding construction technology and method.The tension device consists of a set of tension steel plates,screws,nuts,jack,pressure sensors.The anchoring device comprises a fixed anchorage device,a steering device,a tension anchor device and a steel bar.Through the test,it is proved that the device and the construction technology can solve the problem that the CFRP sheet is easily stripped,and the good bonding effect of CFRP and concrete beams is realized during the tensioning process.In the article,the main research work are as follows:1.The anchoring effect of viscose anchorage on prestressed CFRP cloth was explored.The reliability of anchorage was varified.The feasibility of applying the tensioning anchorage device and strengthening construction technology to CFRP prestressing was studied through experiments.2.The loading test of reinforced beam was carried out,and the variation rule of strain value of CFRP cloth during the test was analyzed,The utilization ratio of the strength was explored,and the corresponding strain rules of stirrups were also studied.The effects of prestressed CFRP sheets on ductility,service performance and ultimate bearing capacity of reinforced beams were studied.3.The influence of variables such as the prestress level of CFRP sheet on the mechanical behavior of reinforced concrete beams was analyzed.The interaction between CFRP sheet,stirrps and concrete in CFRP reinforced beams was discussed when reinforced concrete beams were reinforced in shear by CFRP cloth.The failure modes of beams strengthened with CFRP sheet were also discussed.According to the discussion results,in order to ensure the CFRP cloth to give full play to its high strength characteristics and achieve the best reinforcement effect,the control range of the prestress value of CFRP cloth was given.4.The shear failure mechanism of reinforced concrete beams strengthened with CFRP sheet was discussed based on the relevant codes and research results at home and abroad.Based on the reasonable failure mode of CFRP reinforced concrete beams,the concept and calculation of average effective stress were put forward,and the calculation method of ultimate bearing capacity of FRP shear strengthened concrete beams introduced.Employing the formula,the prestressed concrete beams strengthened with CFRP sheet were calculated and compared with the experimental values.