Experimental Study On Fatigue Behavior Of Prestressed RPC Beams After Creep

With the continuous development of the social economy,the traffic volume is also constantly increasing.Some existing bridges cannot meet the status quo,and the conditions of use cannot meet the requirements.Reactive Powder Concrete is gradually favored by researchers for its high strength,light weight,fatigue resistance and durability.Since the development in the 1990 s,researchers at home and abroad have conducted a lot of research on their mix ratio,curing conditions,durability,etc.,and also conducted in-depth research on reactive powder concrete components,but the research on fatigue properties of reactive powder concrete members is relatively There are few reports on the fatigue performance of reactive powder concrete members after creep at home and abroad.During the actual engineering service,the components may experience a creep history and withstand fatigue loads.At the same time,the stress distribution and failure mode of the ordinary concrete members are quite different from those of the reactive powder concrete members.For the above reasons,in order to promote the use of RPC materials in actual engineering projects.In this paper,the static and fatigue properties of RPC beams with unbonded and unbonded prestressed materials after creep are tested.The creep loading history of prestressed RPC beams and the effect of loading stress on their fatigue properties were investigated.The specific completion is as follows::(1)Comprehensively introduces the current research status of reactive powder concrete.The system summarizes some research developments and conclusions about RPC,and puts forward the key work required for this paper.(2)The mechanical properties of the material were tested to obtain the compressive strength and elastic modulus.The static load and fatigue tests of the prestressed RPC beam before and after the creep were carried out and the test phenomena were described.The results of static test of the two test beams and material performance test data are given.The test results of prestressed RPC beams and unconformed prestressed RPC beams after creeping are compared.The variation of crack width,deflection and deformation of compression zone with increasing cycle number during fatigue test is also described.Based on the existing research results of prestressed steel bars and ordinary steel bars,the fatigue degradation mechanism of two kinds of steel bars was explored.(3)Based on the existing research results of prestressed steel bars and ordinary steel bars,the fatigue degradation mechanism of two kinds of steel bars was explored.(4)Combined with the fatigue test results,verify the fatigue degradation model suitable for reactive powder concrete.At the same time,the experimental parameters of the fatigue total strain and residual strain of the concrete with the change of the number of fatigue cycles are obtained.The model of RPC deformation modulus degradation is deduced by considering the residual plastic deformation development model of creep coefficient.And the residual strain development curve of steel bars is fitted.(5)Based on the basic assumptions of conventional concrete fatigue calculation analysis,combined with the RPC test results,the basic assumptions of fatigue nonlinear calculation analysis of prestressed active powder concrete beams after creep are proposed.Based on this,a simplified calculation method for the most unfavorable section fatigue stress analysis of prestressed RPC beams considering creep coefficient is derived.The calculation results show that the theoretical calculation results of this method are in good agreement with the results obtained by the test.