Research On Hysteretic Behavior Of Nodes In Intersecting Truss Grid Structures Considering Damage Accumulation Effect

Circular steel tubular joints are widely used in various large span spatial structures due to their excellent mechanical properties.Ductile fracture of circular steel tubular joints under strong earthquake is a common failure mode.However,in the current finite element analysis,the research and analysis of hysteretic behavior of intersecting joints rarely consider the influence of damage fracture,which makes the seismic performance evaluation of intersecting joints insufficient.In this paper,based on the previous experiments,the finite element analysis model of node entity is established to verify the accuracy of the finite element analysis method.Then,the influence of geometric parameters on the hysteretic behavior of X-type tubular joints was studied through parameter analysis,and the cracking load of X-type tubular joints was predicted by using the microscopic damage and fracture model CVGM under ultra-low cyclic loading.Finally,through regression analysis,the hysteretic model of X-type tubular joints subjected to axial cyclic reciprocating load with certain accuracy and applicability is fitted.The results show that:(1)When the wall thickness of the main pipe is constant,the smaller the wall thickness ratio of the branch pipe is,the smaller the thickness of the branch pipe is,the earlier the cracking time of the node is,the smaller the load is,and the worse the hysteresis performance is.(2)When the diameter of the main pipe is constant,the larger the diameter ratio of the branch pipe,the larger the diameter of the branch pipe,the delay of the joint cracking time,the increase of the cracking load and the better the hysteresis performance.(3)Appropriately increasing the weld size can effectively delay the cracking time of the joint.The load at cracking increases,and the hysteretic performance of the joint is better.(4)When the diameter of the main pipe is fixed,the larger the diameter-thickness ratio of the main pipe,the smaller the wall thickness of the main pipe,the hysteretic performance of the node is reduced,the cracking time is advanced,and the cracking load is reduced.(5)With the increase of the diameter of the main pipe,the hysteretic performance of the joint decreases,the cracking time of the joint advances,and the cracking load decreases.(6)Through orthogonal design and multiple linear regression analysis,the hysteretic model of X-shaped tubular joints with certain accuracy under axial cyclic loading is fitted.