支管轴压下高强钢圆管X形节点的承载力计算公式

Bearing Capacity Formula of High-strength Steel CHS X-joints Under Axial Compression

摘要:

研究了支管受压的Q460、Q690、Q960高强钢圆管X形节点的静力性能。采用经试验数据验证的有限元模型进行节点有限元参数分析，研究高强钢牌号、支管与主管外径之比（β）、主管外径与其管壁厚度之比（2γ）、主管轴向应力比（n）对节点性能的影响；与有限元参数分析和文献中试验结果对比，评价我国钢结构设计标准计算公式的适用性。结果表明，节点发生主管塑性破坏，节点承载力多由主管局部变形限值（3%主管外径）确定；多数情况下钢结构设计标准计算公式高估了高强钢圆管X形节点的承载力；主管受到压力或较大拉力时均会降低节点承载力。最后，针对不同钢材牌号的圆管X形节点给出了建议的2γ范围。基于主管塑性破坏，提出了考虑高强钢屈服强度、主管拉压效应的圆管X形节点承载力计算公式。

Abstract:

The static performance of circular hollow section （CHS） X-joints using Q460， Q690， Q960 high-strength steel under axial compression was investigated. Using the finite element （FE） model verified by experimental results， extensive FE parametric analyses of joints were carried out. The effects of high-strength steel grades， brace-to-chord diameter ratios （β）， chord diameter-to-wall thickness ratios （2γ）， and chord axial stress ratios （n） on the structural behavior of joints were studied. Then， the suitability of the bearing capacity formula adopted by Chinese Standard GB 50017―2017 was evaluated against the results obtained from FE parametric analyses and literature test results. The conclusions can be drawn that the failure mode of joints is chord plastification， and the joint bearing capacity is often determined by the chord indentation limit， i.e.， 3% of chord diameter； the bearing capacities of high-strength steel CHS X-joints are overestimated by the formula of Chinese Standard GB 50017―2017 in most cases； the chord subjected to pressure or larger tensile forces will reduce the joint bearing capacity. Finally， the ranges of 2γ for different steel grades are recommended. Based on the plastic failure of the chord， the bearing capacity formula of CHS X-joints is proposed， considering the yield strengths of high-strength steel and the chord preload effect.