方管搭接支杆平面内计算长度有限元分析

为了得到方管桁架中搭接支杆平面内计算长度及其随几何参数的变化规律,采用钢结构稳定理论建立了两端弹性转动约束轴心受压构件的屈曲方程.分析得到了搭接支杆平面内计算长度系数的主要影响参数为:受压杆件的长细比λ、支弦杆的宽度比β,支弦杆的厚度比τ、弦杆的宽厚比γ、搭接率ov及支弦杆夹角.θ采用考虑几何非线性和材料非线性的有限元方法,对方管桁架中端部为K型搭接节点的受压支杆的计算长度进行了分析,得到了支杆计算长度系数随主要影响参数的变化规律.从分析结果可知,桁架支杆发生弯曲破坏,计算长度系数在0.55~0.9变化,受几何参数变化影响很大.因此采用理想铰接条件进行桁架杆件的稳定设计是很保守的.

Finite element analysis on in-plane effective length of overlap brace in SHS truss

In order to obtain in-plane effective length of overlap brace in RHS-truss and the relationship between effective length and geometric parameters,the stability equilibrium equation of axially compressed column with rotational spring constraints at two ends was derived by using the elastic stability theory of steel structures.Theoretical analysis results show that the slenderness ratio of brace λ,width ratio of brace to chord β,wall thickness ratio of brace to chord τ,width-to-thickness ratio of chord γ,overlap ratio ov and angle between brace and chord θ are main parameters which affect in-plane effective length of overlap brace.In-plane effective length of the compressed braces with K-type overlap joints at its two ends was analyzed by finite element method considering the geometrical and material nonlinearity.The variation of the effective length of overlap brace with main geometric parameters was obtained.A conclusion was drawn from analysis results that the effective length factors of brace affected greatly by geometric parameters vary between 0.55 and 0.9,and the flexural buckling is the main failure mode of the compressed braces in RHS-truss.So it was conservative to suppose that the boundary condition of compressed braces is ideally pinned in the design of RHS truss.