Practical Design Method For Overall Stability Of Steel Tubular Truss

Because of beautiful appearance and good geometric characteristics of the section,steel tubular truss structure is widely used in industrial and civil buildings.With the increase of the span of structure,the global stability of steel tube truss has been an increasing concern.How to determine the overall stability bearing capacity of steel tubular truss is still a problem that needs to be solved urgently in the engineering design.In this paper,the overall stability of planar steel pipe truss and spatial steel pipe truss with rectangular cross section have been deeply studied,which depend on the lateral stability of upper chord member.Take the upper chord member as axially compression member to have the stability calculation to determine the overall stability bearing capacity.On this basis a convenient and practical method has been proposed.For planar tubular truss,under the assumption of hinged joint,the upper chord member was simplified as compressed member without lateral support.The influence of the position of the load and the change of the axial force on the lateral stability bearing capacity was analyzed.Compared with the results of finite element analysis,the correctness of theoretical analysis was verified.And then through a large number of parametric analysis,the parameter regression formula of bearing capacity increasing coefficient k considering the stiffness of the joint was fitted.For spatial tubular truss with rectangular cross section,firstly,through a large number of nonlinear finite element analysis,influence factors of overall stability were determined.Referring to the analysis method of planar truss,the effect of loading position on the overall stability of the truss without diaphragm was studied.Then with lots of numerical analysis,proved that when the load was on the top chord member,the truss with diaphragm could be directly equivalent to lattice axial compression member to have the calculation on global stability of virtual axis.Finally,for the truss with diagonal bar set between the lower chord member,through much parametric analysis,a parametric regression formula of improved bearing capacity coefficient ?considering the lower effective stiffness was fitted.The practical design method is in good agreement with the finite element results,which verifies the applicability and reliability of the design method.