The Study On Carrying Capacity Of Spatial Steel Tubular Truss With Inverted Triangle Section

In recent years, the steel tubular truss which utilizes welded tubular joints has found its wide application in the space and long span structures. Current design theories and methods in the tubular structures are mainly focused on the load-carrying capacity of tubular joints. Traditional truss theory has been used in the design of the truss for checking stability, there are few researh about the overall stability to spatial steel tubular truss.From the loading features of the space truss structure,when the ratio of side is above 1.5,its loading features is single way bearing,not double way bearing.Plane tubular truss and spatial tubular truss are single way bearing,which have bigger in-plane stiffness.But,the out-plane stiffness and stability of the plane truss are poor,which need some lateral bracing.While,the spatial steel tubular truss widen the width of upper chord,increase the stability of the upper chord,and improve the working performance of the structure.But, how much the lateral stability is improved also need to be researched.taking the spatial steel tubular truss as the study object,this article will do the following work:First, the author use the FEM program ANSYS11.0 to analys eigenvalue buckling,and get all buckling modes and buckling loads,then exactly determine the critical load which made the structure unstable through nonlinear analysis,considering initial imperfection,large deformation responses,etc.and follow the post buckling of the structure using the arc-length method.Secondly, the author also analyse the static behavior of the roof system composed by spatial steel tubular truss,according to our engineering practical experience,the parameter of section and the area of the member section are the main factor effecting the stability of the spatial steel truss.Finally, ultimate carrying capacity of the spatial steel tubular truss is caculated.from the caculation,we know there are two remarkble effect factors:the ratio of width to height and the height-to-span ratio,then analyse their effect and the overall effect to the ultimate carrying capacity.