正交X形圆钢管相贯节点焊缝断裂的试验与机理分析

Experiment and mechanism analysis of weld fracture of orthogonal CHS-CHS X-joint

圆钢管相贯节点焊缝处应力分布难以避免不均匀性,而现行设计规范计算圆钢管相贯节点焊缝强度时未考虑这种不均匀性的影响。通过设计6个X形圆钢管相贯节点试件的支管受拉试验,研究了节点的破坏形态,分析了应力分布的不均匀性对节点焊缝强度的影响。试验结果表明：所设计的相贯节点实现了预期的焊缝断裂破坏模式;焊缝的断裂通常始于鞍点位置;节点应力分布的不均匀性对焊缝强度的影响很大;主管管壁刚度的大小对应力分布的均匀性起着关键作用,当节点外形尺寸保持一致时,主管管壁刚度越小,节点应力分布的不均匀程度越大,焊缝的强度越低;试验中主管管壁刚度最小的节点,其平均焊缝强度尚未达到刚性节点的40.3%;现行设计规范中未考虑圆钢管相贯节点应力分布不均匀性影响的计算方法会导致计算结果偏于不安全。

The non-uniform stress distribution in circular hollow section （CHS） joint near the weld is unavoidable, which, however, is not taken into account in the computation of weld strength of CHS joint in the current design code.＂ Six X-type CHS-CHS joint specimens under tension were designed in this research, in order to experimentally study the failure mode of the joints and analyze the influence of non-uniform stress distribution in joint on the weld strength. The test results show that： the predicted failure mode of fracture in the weld is obtained during the test; fracture always initiates at the saddle points; the non-uniform stress distribution has a great impact on the weld strength of the joint; the local chord stiffness is the key factor to determine the stress distribution： for the joints with the same profile, the lower local chord stiffness shall lead to a severe stress non-uniform distribution, and thus a lower weld strength ; in this test, the average weld strength of the joints with the lowest chord wall stiffness has not yet reached 40.3% of that of the rigid joint; the formula in current design code may be unsafe because the influence of the non-uniform stress distribution is ignored.