Concrete Filled Steel Tubular Arch Bridge K-Shape Node Mechanical Finite Element Research

Concrete filled steel tubular K shape node is an important force of concrete filled steel tube arch bridge. Studying and mastering the mechanical performance of concrete filled steel tubular K node help to deeply understand and research of steel tube concrete arch bridge. According to the force of the K node, when main pipe is under a certain level of axial pressure, the two branch pipes are under axial compression and axial tension, respectively. through the theoretical analysis and finite element numerical simulation analysis of node force performance and failure mode, the main work and conclusions are as follows:(1) Firstly, Studying the basic theory of concrete-filled steel tube arch bridge finite element K shape node, selecting rational steel tube and concrete constitutive relation, put forward the reasonable and effective nodes of the finite element modeling method, compared with the test results data analysis, construct a simulation analysis for the literature of the nodes in the structure, it is concluded that the nodes of the finite element modeling method is scientific and reasonable.(2) Compared analysis the mechanism between K-node and empty steel tube of concrete filled steel tubular arch bridge of K shape node load- displacement curve, main pipe of filling concrete effective constraint and support supervisor has greatly increased the node of the bearing capacity and stiffness; Analyzed the characteristics of the node load-displacement curve, the total stage generally can be divided into the elastic stage, elastic-plastic stage and failure stage three stages, and discusses the stress distribution of the three phase node, node failure mode:node has pressured pipe joint branch the destruction of the local buckling occurred in tension and node branch director rip joint damage.(3) Different structure parameters was established through ANSYS finite element node K shape model of concrete filled steel tube arch bridge, the process of numerical simulation analysis, node structure parameters include:the thick diameter ratio of main pipe and branch pipe, branch pipe thickness ratio and main pipe diameter ratio, branch and director of wall thickness ratio, branch and director of axis Angle, the two tube clearance, director of core concrete grade, axial stress level and zeta node size scaling coefficient, and all the parameter selected was determined when the model was construct. Through research analysis:branch and main geometry pipes are the main factors that influencing the ultimate bearing capacity, other factors partially influence the ultimate bearing capacity, when the main shaft stress level is 0.5～0.6, node peaks a ultimate bearing capacity.(4) Based on the calculation methods of bearing capacity in the basic theory of material mechanics and rectangular concrete-filled steel tube node, putting forward an suggested ultimate bearing capacity calculation equation about the concrete filled steel tubular arch bridge K shape node under different failure modes, compared with calculated value of finite element simulation, the result show that the error is small and safety.