Mechanical Behavior Of Large-scale Prestressed H-Steel Concrete Composite Beams Considering Core Constraints

Prestressed steel-concrete structure is a kind of composite structure formed by applying prestressing technology to steel-concrete structure.The beams of this structural form have their own excellent characteristics of steel-concrete beams and pre-stressed concrete beams.Namely,the use of prestressing technology improves the crack resistance of beams under normal service conditions and the deformation resistance of members;the use of steel-concrete technology improves the ultimate bearing capacity of members,and raises the ductility and energy dissipation capacity of beams.Prestressed steel-concrete structure is a technological innovation of traditional prestressing concrete structure and steel-concrete structure.It has high bearing capacity,good service performance,and is easy to achieve long-span and heavy load.In recent years,scholars at home and abroad have carried out a series of research work on prestressed H-steel concrete beams,and achieved some scientific research results.However,there are relatively few studies on large-scale prestressed H-steel concrete beams.In this paper,the bearing capacity,deformation performance of large-scale prestressed H-steel concrete simply supported beams and plastic internal force redistribution performance of large-scale prestressed H-steel concrete continuous beams are studied by numerical simulation.The main work is as follows:(1)In order to study the flexural behavior of large-scale prestressed H-steel concrete beams,considering the restraint effect of steel flange on concrete,a beam-member model considering the core restraint effect was established to simulate the existing experimental prestressed H-steel concrete beams,and to verify the reliability of the modeling and analysis.On this basis,seven large-scale H-steel concrete beams are designed,and a beam-member model considering the core restraint effect is established.The mechanical properties and failure modes of the prestressed H-steel concrete beams during loading are analyzed with the comprehensive reinforcement ratio,steel content and concrete strength grade as the parameter variables,and the influence of each parameter variable on the bearing capacity of the beams is discussed.(2)In order to study the deformation behavior of large-scale prestressing H-steel concrete beam members,a beam-member model considering core restraint was established for existing test members.The deflection of the simulated steel bars at yield,the deflection of the lower flange of the H-steel at yield and the deflection of the ultimate load were compared with the test beams.In the case of high coincidence between test results and simulation results,the deformation behavior of large-scale prestressed H-steel concrete beams is studied,and steel content of section steel,prestress degree,concrete strength grade and other parameters on the deformation performance of the simulated beam are discussed.The results of numerical analysis show that the steel content of section steel and prestress degree can effectively improve the deformation resistance of members.(3)In order to study the stress performance and moment redistribution of prestressed H-steel concrete continuous composite beams,considering the restraint effect of section steel flange on concrete,a numerical analysis model of prestressed H-steel concrete continuous composite beams considering the core restraint effect was established,and the simulation analysis of two-span prestressed H-steel concrete continuous composite beams was carried out.Based on the high coincidence between simulation results and test results,the expansion parameters of this kind of continuous beam members are analyzed.The effects of prestressing degree,steel content of section steel and ratio of section height to total section height on plastic internal force redistribution are discussed.The analysis results show that the formula for calculating the equivalent length of plastic hinge zone is obtained by analysis and fitting,and the design method of moment modulation is proposed.(4)Seven large-scale prestressed H-steel concrete continuous composite beams are designed and the numerical simulation model is established.The coordinate distribution of moment amplitude modulation coefficient of large-scale prestressed H-steel concrete continuous composite beams is in good agreement with the simulation curve.It is proved that the proposed formula of moment modulation factor is still applicable to large-scale prestressing H-section steel-concrete continuous composite beams.It can be used for moment modulation design according to the formula of moment modulation factor.