| Steel-concrete composite beams can give full play to the material properties of concrete and steel,and can be widely used in bridge structures.The composite beam connects the two materials and forms a whole through shear joint,which makes full use of the advantages of concrete and steel.But inside the composite beam,the shear force value of the bolt bearing along the beam length direction is different,and the fatigue damage of the bolt is different with the fatigue loading.Different bolt fatigue damage causes the shear force redistribution of composite beam,which leads to the decrease of composite beam stiffness and fatigue failure.For analyzing the fatigue performance of composite beam,the whole process analysis model of composite beam fatigue is established,static load and fatigue test of composite beam with high strength bolt connection are carried out,and finite element analysis is carried out by ABAQUS.The main contents include the following three parts:(1)Considering the reduction of the ultimate bearing capacity of concrete,steel beam and shear connector in composite beam,the deformation,slip and shear value of composite beam are solved by matlab programming based on the discontinuous force transfer model.the formulas for calculating the elastic deflection and the residual deflection of the composite beam at the upper limit of fatigue load are put forward.according to the parameter analysis,the degree of shear connection is an important factor in the deformation of the composite beam and the slip of the interface.Finally,the fatigue failure criterion of composite beam is put forward,which can judge the form of fatigue failure and obtain the fatigue life.(2)A combined beam with high strength bolts is designed for 1/4 span,and static load and fatigue test of the combined beam are carried out.The data of deflection,cross-section strain,residual deflection,residual slip and dynamic load of composite beam were measured.It was found that the 1/4 span deflection with high strength bolt connection decreased faster than the other side in the initial and middle stage of static load test.The section size and loading mode of composite beam are substituted into the fatigue whole process analysis model to further verify the accuracy of the model.(3)The influence of element type and contact relation setting on the model is analyzed by modeling the composite beam with high strength bolt connection in 1/4 span ABAQUS by finite element software,and the accuracy of the finite element model is verified by load deflection curve and relative slip curve.The selection of relative slip value in solid element model is introduced,and the variation of bolt stress with load is analyzed.Finally,the influence of different modeling methods on the stiffness and strength of composite beams is considered. |
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