Study On Bending Performance Of Reinforced Concrete Beams Damaged By Hdc Reinforcement Under Sulfate Environment

High ductile concrete(HDC)is widely used in the reinforcement and repair of damaged parts of building structures and hydraulic structures due to its superior tensile strength,crack resistance and high durability.Buildings in coastal areas and saline areas in China will be corroded by sulfate,which affects the strength of concrete structures.Therefore,studying the bending properties of reinforced concrete beams damaged by HDC reinforcement in the sulfate corrosion environment is of practical significance for the practical application of HDC materials.In this paper,one RC beam and three HDC-strengthened damaged reinforced concrete beams with different reinforcement thicknesses were placed in 15%sodium sulfate solution for a long-term immersion for 240 days to carry out the flexural performance test,and the uncorroded RC beam was set as the control beam.By studying the damage pattern,bearing capacity and deformation capacity of five specimens;at the same time,the ultrasonic plane measurement method was used to carry out non-destructive testing on the test beams corroded by sulfate;and on the basis of the test,ABAQUS is used to establish the corresponding finite element calculation model for nonlinear analysis.The main research content and results are as follows:(1)Through the four-point bending static loading test,the effects of different reinforcement thicknesses(10mm,15mm and 20mm)on the failure morphology,bearing capacity,deformation capacity,steel bar and concrete strain of reinforced concrete beams damaged by HDC reinforcement were studied.The test results show that:in sulfate environment,the bearing capacity and deformation capacity of the test beams strengthened with HDC are significantly improved compared with the unstrengthened test beams,and the bearing capacity and deformation capacity of the test beams strengthened with the increase of the reinforced thickness are also increased.Due to the bridging effect of the fibers and the ferrule effect of the HDC layer,the use of HDC reinforcement can make full use of the longitudinal ribs.(2)Through the ultrasonic flat measurement method,the measured ultrasonic acoustic time regression analysis was carried out,the corrosion damage layer thickness of each test beam at different corrosion ages was calculated,and the change of damage layer thickness of HDC reinforced beam in sulfate environment was studied,the results show that:at the same corrosion age,the thickness of the damaged layer of the HDC-strengthened beam decreases with the increase of the reinforcement thickness,the thickness of the damaged layer of the RC beam is greater than that of the HDC-strengthened beam,and HDC shows good resistance to sulfate erosion;according to the test results,the establishment Prediction model of concrete damaged layer thickness considering the effect of HDC reinforcement thickness under long-term sulfate corrosion.(3)On the basis of the experimental research,the corroded HDC material constitutive was selected through the finite element analysis software,and the calculation model of the damaged reinforced concrete beam strengthened by HDC in the sulfate environment was established,and the calculated load-displacement curve,deformation of the test beam and The damage cloud image is compared with the test results to verify the rationality of the established model.On this basis,the influence of HDC reinforcement thickness on bending performance is extended,and it can be seen from the comparison of load-displacement curves that with the increase of reinforcement thickness,the bending bearing capacity of the test beam is significantly increased,but the ductility will decrease.