[Study On The Mechanical Properties Of Steel Structure Flexural Members Reinforced By Frp Under Load]

In recent years, due to the extensive research of scholars at home and abroad, the carbon fiber composite material is more widely used in practical engineering, it is more common in engineering that using carbon fiber sheet for beam and plate structures strengthening member. Although domestic and foreign scholars study deeply on the mechanical properties that carbon fiber reinforced bending, however, most of the test is confined to the reinforcement of damaged members or strengthening research after unloading, and the actual stress state of steel structure has a certain gap with that in engineering. Therefore, it makes a more systematic study on bending performance of H type steel beam under load.This test designed a total of eight specimens, specimen cross-sectional dimensions are125mm×125mm×6.5mm×9mm, beam length are2m, including a comparison of the beam, the rest are holding carrier beam, in order to prevent the local destruction and adding welding stiffener in the concentrated load. The main change parameter in test are sustained load level, reinforcement layers, reinforcement length and end anchorage conditions etc. During the test, need collecting the specimen deformation, strain and the steel beams, and deflection of the beam. Experimental results show that the failure mode of reinforced beam is mainly divided into three types:the first is that CFRP cloth is pulled off; the second is the test beam reaches the ultimate deflection and bending failure; the third is CFRP cloth ends peeling damage. Compared with contrast beam, yield load, ultimate load and failure load of CFRP reinforced steel has a different degree of increase under different experimental parameters, the yield load and ultimate load and sustained load level hold down the level of approximation to the opening of secondary curvilinear relationship. For beam of different design parameters such as length of reinforcement, layers of reinforcement, with increase of the reinforcement amount, the feature load has a different degree increase, but with the improvement of reinforcement quantity, its increase fall.The beam remains approximately in line with the flat section assumption whether or not holding load. With the increase of amount of reinforcement, the test beam rigidity is improved to different degrees. Stress on flange of steel beam and CFRP along the axis of the test were analyzed, it can be seen that at the ends of CFRP additional U-shaped hoop can effectively reduce the degree of CFRP cloth ends of stress concentration.Based on previous research, according to the principles of strengthening steel structure, the paper systematically analyzes the influence between lag strain and load state, and put forward the corresponding calculation method of strain lag. Considering the nonlinear constitutive relations of materials, using the relationship that the strengthened beam bending moment and curvature of section under load, and further on analysis of the whole process of deformation force of steel beams under sustained load. Combined with steel beams holding the whole process under load stress analysis and test, and obtain the yield load and ultimate load calculation formulas. To analyze the interface stress of reinforcing steel, and analyze the bonding shear stress and peel stress respectively, the bonding shear stress equation and peel stress equation is obtained and provide reference for engineering.Based on the experimental and theoretical basis, using ABAQUS software to establish a finite element model of the steel beam under different design parameters, the following conclusions were obtained:the establishment of finite element model, simulation results of its capacity, with the experimental values were compared, a difference of less than5%, in good agreement. Under different load levels from reinforced steel beams holding the load-deflection curve can be drawn that failure load of parts will decline with the increased loading level, which is the actual project to determine whether it is necessary to have a structural reinforcement reference. Reinforced by the different layers of reinforcing steel beam load-displacement curve can be drawn:bearing capacity increases with increase of reinforcement layers, but when the reinforcement layer increases to a certain degree, the bearing capacity is in a flat or declining trend. By changing the effective bond length of the load deflection curve can be drawn, with the increase of sticking CFRP cloth length, the bearing capacity is improved correspondingly, in good agreement with the test results.