Experimental Study And Numerical Analysis Of Fatigue Residual Bearing Capacity Of Prestressed Concrete Beam

The prosperity and progress of national economy promotes the rapid development of road and bridge transportation nationwide.In the process of resource aggregation,some vehicles tend to be overloaded.At the same time,some bridges are in the state of fatigue operation as a result of alternating action of heavy and light load.Based on the"research on the key technologies for the reconstruction of heavy-load highway freight passage",a science and technology project of construction by the ministry of transport,this paper studies the fatigue residual bearing capacity of prestressed concrete simple-supported box girder under heavy load.The main work done and the main conclusions obtained are as follows:(1)In the first chapter,the status of overseas and domestic research on highway prestressed concrete bridges is discussed at first,and then the research approaches and contents of are presented in view of the shortcomings found in the current research.(2)In the second chapter,the parameters such as the size,material,reinforcement mode and the strain measuring point of the reduced-scale model girders are presented,and the cracking load and ultimate load of the model girder are calculated based on the static load test results.(3)In this paper,the equal amplitude fatigue load tests are carried out on five model girders to study their fatigue properties and the residual bearing capacity.The first order vertical frequency of the beam body,the strain of the concrete at the upper edge of the mid-span side,the strain of the ordinary reinforcement and the prestressed steel strand at the cross-section of the mid-span and 1/4 cross-section,the crack,the height of the remaining cross-section,and the bending stiffness of the beam body under the fatigue load are analyzed.The results show that the residual bearing capacity of B1?B4 beam after fatigue for 2 million times is 1%?15.2%lower than that of the static load test.The static failure test reaches the limit state when the ordinary tensile steel bars yield and quit working.(4)Based on ABAQUS finite element model,the residual bearing capacity of 4 beams is numerically analyzed,and the results show that the ultimate bearing capacity of the model beam decreases by 20.4%at the maximum after 2 million fatigue cycles,which verified the correctness of the calculation and analysis by comparing with the test values.The simplified fatigue failure analysis method can be effectively applied to the finite element simulation of the residual ultimate bearing capacity of the beam body.