N形方主管圆支管搭接节点有限元分析与承载力计算

基于N形方主管圆支管搭接节点的试验，从节点破坏模式、变形过程和承载力等方面对N形方主管圆支管搭接节点的非线性有限元模型进行了校验。采用验证的有限元分析模型，分析了被搭接支管受拉且内隐蔽部分焊接的搭接节点的应力分布、塑性区扩展和破坏模式，以及几何参数、内隐蔽部分焊接与否、支管轴力性质、主管轴力等因素对节点性能的影响。分析结果表明：支主管径宽比、主管宽厚比、支主管壁厚比是影响N形方主管圆支管搭接节点破坏模式和承载性能的主要因素；内隐蔽部分未焊接对被搭接支管受压的节点承载力影响较小，但对被搭接支管受拉的节点承载力影响较大；支管轴力性质、主管轴压力对N形方主管圆支管搭接节点承载力的影响不可忽视。应用多元线性回归方法，在GB 50017-2003《钢结构设计规范》现有承载力计算公式基础上，拟合出了考虑相关影响系数的修正计算式；按修正计算式计算得到的承载力与试验结果吻合良好，且具有较好的适用性。

Parametric analysis and design equation of bearing capacity for overlapped CHS-to-SHS N-joints

Based on the experimental results of overlapped CHS-to-SHS N-joints, a finite element model was generated and validated by comparing the failure mode, deformation process, and bearing capacity between FEA results and experimental results. Using this model, the stress distribution, propagation of plasticity and the failure modes of overlapped joints with through-brace-in-tension and welded hidden seam were studied. The effects of geometric parameters, with or without hidden weld, loading hierarchy reversal of braces and chord force on the bearing capacity of the joints were also studied. The results of FEA indicate that brace-to-chord width ratio, chord width-to-thickness ratio and brace-to-chord thickness ratio, have great effect on the failure mechanism and bearing capacity of overlapped CHS-to-SHS N-joints. And the absence of hidden welds has less influence on the bearing capacity of the through-brace-in compression joint than on that of through-brace-in-tension joint. Furthermore, the effect of loading hierarchy reversal of braces and chord force on the bearing capacity of the joints can not be neglected. Based on the design equation in the code, a formula predicting the bearing capacity of overlapped CHS-to-SHS N-joints was proposed by applying multivariate regression analysis. Results calculated using the recommended design equation agree well with experimental results.