Study Of Ultimate Bearing Capacity On Large Span Steel-Concrete Composite Truss Joint

As a new type of structure, steel-concrete composite truss bridge has a broad application prospect in the overloaded, large span railway bridge, with the advantages of light weight, stiffness,superior overall performance, high capacity and low cost. The winding end joint will withstand unbalanced horizontal thrust under loads, due to the mechanical properties difference between steel and concrete, the joint combination parts are complex, so it has an important meaning and value that how to ensure a common force and coordination deformation, make the joint and truss a high bearing capacity. Based on the experimental results, the bearing capacity of two kind of combination truss bridge is analyzed with finite element analysis in the paper, and the main research contents are listed as follows:Firstly, the composite truss nonlinear analysis method is discussed. The ABAQUS non-linear analysis of the process is introduced at the beginning to lay the foundation for the subsequent numerical analysis. Then the composite truss mechanism of shear capacity is discussed, the shear capacity of the composition parts and each part is analyzed, and the calculation formula for bearing capacity of each part of shear is obtained.Secondly, the composite truss transfer mechanism is analyzed, the whole stressing process of external joint and ear plate joint in the horizontal loads is simulated by nonlinear finite element analysis software ABAQUS. Load transfer path in the joint internal is analyzed under horizontal thrust after the typical joint is selected, and then the stress magnitude and distribution of laws of the chord, steel plate and the web member is found; the law of the shear distribution on each PBL shear connector is obtained after calculating the situations whether the steel plate and the concrete bond or not. The results show that the PBL connector has a good ability of shearing resistance.Thirdly, the constitution of composite truss joint limit bearing capacity is studied. Using each component as the research object, the limit bearing capacity of each component is analyzed one by one on the basis of clearing the joint power transmission mechanism. Then the loading capacity magnitude of each component is obtained according the principle that the final joint limit bearing capacity is equal to the lowest bearing capacity of the single component, and then the destruction order of the joint can be deduced. Finally, the factors which affects the composite truss joint limit bearing capacity are analyzed, the results shows the board thickness is a major factor in external joint, while the web member thickness is a major factor in ear plate joint.