Study On Fatigue Performance Test And Theoretical Of Unbonded Partially Prestressed Beams RPC

Reactive Powder Concrete(Reactive Powder Concrete,hereinafter referred to as RPC)has been gradually brought into researchers focus with its excellent performance.It's many properties have been widely studied by domestic and foreign scholars such as the material mix ratio ? component of the static performance ?corrosion resistance and so on,but its fatigue characteristics has been rarely involved.While in actual life,the components are likely to bear the fatigue load in most cases.At the same time,the stress distribution and damage form of RPC component are different from those of ordinary concrete.In order to make the RPC material popularize and make full use of its high strength characteristics,this paper has carried out static and fatigue performance test and theoretical analysis on the RPC beams with unbonded prestressing.The details are as follows:(1)This paper summarized the current research on RPC and some of the conclusions that had been drawn.And the key contents of our work were proposed according to the issues that will be encountered but rarely involved in other researchs.(2)The mechanical properties of the basic materials used in the theoretical analysis process were tested.The tensile strength,compressive strength and elastic modulus of RPC were obtained.And the static load and fatigue performance of the unbonded prestressed RPC beam were tested.The whole process from the force to the destruction of the beam under static load was described.The variation law of the crack width,the deflection and the edge strain of the RPC compression zone were compared between the general reinforced RPC beam and the unbonded prestressed RPC beam with the loading times during the process of fatigue load cycle.(3)According to the characteristics of high tensile strength of RPC material,the calculation formula of the cracking moment,of the bearing capacity and of the cross-section deflection were deduced.The stress increment was calculated based on the relationships between increment and deflection of the stress of the unbonded prestressed tendons,and the calculated value was close to the measured value.(4)Combining with the fatigue test results of unbonded prestressed RPC beams,the expression of damage variable was obtained by nonlinear fitting.On the other hand,the total strain and residual strain development model with the number of fatigue load cycles were obtained.And the RPC elastic modulus degradation model was deduced by the residual strainmodel.Based on the definition of damage variables,the fatigue damage model of steel bars was deduced by the degradation of elastic modulus.(5)Based on the basic assumptions used in the process of ordinary concrete fatigue analysis and on the specific force characteristics of RPC,the basic assumptions used in fatigue analysis of unbonded prestressed RPC beams were proposed.The fatigue nonlinear analysis process was replaced by piecewise linearity,and the simplified method of fatigue analysis of unbonded prestressed RPC beams was deduced,it's results are close to the actual test results.