【作者】 秦绪福；

【导师】 武振宇；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2007， 硕士

【摘要】 采用直接焊接连接的空心管桁架中,受压腹杆一般都有相当大的端部约束,一般情况下其计算长度系数μ均小于1.0。欧洲标准Eurocode3规定对直接焊接空心管桁架腹杆,计算长度系数取0.75。而我国规范并没有对此进行规定,工程中一般按铰接体系进行设计,计算长度取其几何长度,取值很保守,所以很有必要进行这方面的研究。本文利用有限元程序ANSYS对采用K型间隙节点的方钢管桁架腹杆平面外计算长度系数进行了大规模的参数分析。首先,将桁架支杆简化为两端受弹性转动约束的轴心受压构件,根据钢结构稳定理论,建立构件平衡微分方程,推导出杆件稳定承载力公式。当杆件两端转动刚度为已知时,便可以求得支杆稳定承载力。根据欧拉公式便可以反推出支杆计算长度系数μ。其次,建立节点有限元模型,计算出节点平面外转动刚度。考虑支弦杆宽度比β、弦杆宽厚比γ、支弦杆厚度比τ、支杆高度与弦杆宽度比η、节点间隙g、支弦杆夹角θ、整体尺寸比C等参数的影响,对节点平面外转动刚度进行大规模参数分析。通过300多个节点算例分析得出节点平面外转动刚度随节点参数的变化规律。根据有限元计算结果,对节点平面外转动刚度进行多元回归分析,得出节点转动刚度的计算公式。将回归公式计算出来的结果与有限元计算结果进行对比,两者符合较好,回归效果良好。根据本文推导出的弹性转动约束下压杆稳定承载力公式,结合求得的支杆两端节点转动刚度,计算出受压支杆平面外计算长度系数μ,并分析计算长度系数μ随节点几何参数的变化规律。通过多元回归分析,推导出计算长度系数的计算公式。更多还原

【Abstract】 In HSS (Hollow Structural Sections) truss, the chords provide great restraints on the braces. So the effective length factor of braceμis less than 1.0. According to the Eurocode3, The effective length factor of brace of directly welded HSS truss is 0.75. However, the effective length factor of HSS truss is not specified in Chinese Code. In practice, HSS truss is supposed to be pinned. So it is necessary to do some research on the effective length factor of HSS truss. In this paper, a systematic parametric research on effective length factor of compression brace is carried out by ANSYS.Firstly, the compression brace is simplified as an axial compression member with elastic rotational restraints. According to stability theory of steel structures, the equilibrium differential equation is established. From the equation, the stability formula of compression brace is obtained. Then, the effective length factor of brace is obtained by stability formula and the Euler formula when the rotational stiffness is available.Secondly, the FE model of gapped K-joint is established. Then the out-of-plane rotational stiffness of the joint is calculated. Extensive FE analysis for out-of-plane rotational stiffness of the joint is conducted. Considering the parameters such asβ,γ,τ, g,η,θ, C, more than 300 joints are analyzed and the variation of rotational stiffness of the joint with geometrical parameters are available.Through the multi-parameter regressive analysis, equations calculating out-of-plane rotational stiffness of the joint are acquired. The out-of-plane rotational stiffness of the joint calculated from the equations coincide with the results that are obtained by finite element analysis.According to the stability formula of brace and the rotational stiffness of the joint, the effective length factor is calculated. The variation of effective length factor with the geometrical parameters is obtained. The equation calculating the effective length factor is acquired through multi-parameter regressive analysis.更多还原