Experimental Study On Mechanical Properties Of RC Beams Strengthened With External Prestressing

External prestressed reinforcement technology is widely used in the existing bridge reinforcement engineering practice for its unique advantages.The initial states of external prestressing have a far-reaching influence on the mechanical properties of the reinforcement structures.To determine the reasonable initial states and make full use of external prestressing reinforcement efficiency,this paper combines Research on the Technology and Application of External Prestressed Reinforcement Based on Liumei Bridge,which is the Key Project of Transportation Science and Technology Development in Fujian Province.The mechanical properties of RC beams strengthened with external prestressing are studied,and the main content are as followed:Firstly,three-point loading test of RC beams strengthened with external prestressing was carried out on mechanical testing machine.The main test parameters were tension control stress and height of steel wire to the bottom of RC beam,including six reinforced beams and one non-reinforced beam.The failure mode,load-deflection curves,cable strain and concrete strain were obtained.The experimental results show that external prestressing reinforcement can significantly improve the stiffness and bearing capacity of RC beams.In a certain range,increasing the height of steel wire to the bottom of RC beam and tension control stress is helpful to improve the rigidity of the strengthened beams and improve their mechanical properties.Then a finite element model of RC beams strengthened with external prestressing was established,considering geometric nonlinearity,material nonlinearity and contact nonlinearity.The finite element model was validated by the experimental data in this paper.The results show that the established model can effectively simulate the mechanical properties of RC beams strengthened with external prestressing under three-point load.Thirdly,a reasonable selection of tension control stress and height of steel wire to the bottom of RC beam was proposed.Compared with bearing capacity,deflection,failure mode,stress and strain states of strengthened RC beams under different initial states according to experimental data and finite element calculation results,the basic selection principle of reasonable tension control stress and height of steel wire to the bottom of RC beam was put forward based on this test.Combined with the established finite element model and the theoretical formula derivation,working mechanism of the strengthened RC beams under different initial statess was analyzed,and a comparative study on cracking and ultimate load was carried out.The analysis included failure mode,stress distribution,strain distribution,height changes of steel wire to the bottom of RC beam,crack development and deflection.The mechanical properties of RC beams strengthened with external prestressing were studied in detail.