The Research On Fatigue Performance Of Small And Medium Span PC Girder Bridge Under Bending And Shear Stress State

In the existing road bridge construction,the number and length of small and medium-span bridges that in prestressed concrete beam bridge based have accounted for a large proportion,due to the tensile strength of concrete is small,and combine with the rapid increasing in traffic and the growth of long large heavy vehicles,under cyclic loading of the vehicle,so that the concrete of bending and shearing force area where do not reach the ultimate tensile strength produce the fatigue inclined cracks in Webs.Therefore,considering principal stress limit values under bending shear stress state and fatigue cracking performance after the deterioration of the concrete member from multiple perspectives is very important.Based on this,the main research contents and results are as follows:1? Refer to the related literature at home and abroad.The research status and the corresponding research results of flexural fatigue and shear fatigue of concrete materials and components and fatigue of steel are summarized.Introduced the theory of concrete fatigue analysis and life prediction method and fatigue of concrete based on nonlinear finite element numerical analysis method and so on.Provide a theoretical basis and inspiration for the idea of follow-up research.2? Based on the existing concrete shear strength test,designed and made by steel reinforced "Z" shaped specimen and loading means;and based on smeared crack model and extended finite element method for nonlinear analysis to predict crack initiation position and the direction of crack propagation theory to verify the feasibility of the specimen.3?Carried out static performance tests and shear fatigue tests of concrete,got the static compression and shear properties and shear fatigue failure characteristics and the S-N curve equation;Analyzed and discussed the development relationship between the shear strain amplitude with the fatigue time,and proposes a method based on the shear stiffness degradation prediction concrete shear fatigue life.4?Starting from the component form,based on the numerical analysis method research the fatigue property of prestressed concrete beam after concrete cracking.First of all,based on the plastic damage model carried out on a prestressed concrete box girder ultimate bearingcapacity simulation to verify its feasibility.Then through the concrete stiffness degradation,residual strength degradation,steel residual strength degradation and the loss of prestress steel parameters such as degradation rule,combined with the simplify analysis method of whole fatigue failure process,the simulation analysis of the fatigue failure of the whole process was carried out.Results show that this method can better simulate the fatigue performance of prestressed concrete structures under bending shear stress state.