N形方主管圆支管相贯节点受力性能试验研究

对10个N形方主管圆支管相贯节点进行了静力性能试验研究。试验节点包括6个内隐蔽部分不焊接的搭接节点、2个内隐蔽部分焊接的搭接节点和2个零间隙节点。分析了节点的受力性能、破坏模式和承载力，并对内隐蔽部分焊接情况、支管轴力性质、节点两侧主管轴压力、支管搭接情况等对节点承载力的影响进行了研究。结果表明：内隐蔽部分焊接与否对被搭接支管受拉的节点承载力影响较大，焊缝断裂是内隐蔽部分未焊接节点常见的破坏模式；在试验几何参数条件下的内隐蔽部分未焊接搭接节点在被搭接支管受压情况下的节点承载力较被搭接支管受拉时大很多；节点两侧主管均有轴压力时的搭接节点承载力较仅一侧主管有轴压力时要小；被搭接支管受拉的搭接节点承载力远远高于相应的零间隙节点。研究表明：国内外现行规范中的N形方主管圆支管搭接节点承载力计算公式对发生主管局部屈曲破坏模式的情况并不适用，而且公式也未考虑内隐蔽部分焊接与否、支管轴力性质和主管轴力等因素的影响，还有待完善。

Experimental research on mechanical behavior of CHS-to-SHS N-joints

To study the static behavior of CHS-to-SHS N-joints, six partially overlapped specimens with the hidden seam unwelded, two partially overlapped specimens with the hidden seam welded and two relevant gapped specimens were tested under monotonic loading. The mechanical behavior, joint failure modes and joint bearing capacities were presented in this paper. The effects of hidden seam welded or not, loading hierarchy reversal of braces, axial compression in the chord of both sides of the joints and braces overlapped or not were discussed. Test results show that the welding situation of the hidden seam has relatively great effect on partially overlapped CHS-to-SHS N-joint with through brace in tension, and weld crack is a common failure mode of the joints with the hidden seam unwelded. The bearing capacity of joints with through brace in compression is much higher than that with through brace in tension, and the joints with axial compression in one side of the chord obviously have better bearing capacity than that with axial compression in both sides of the chord. Furthermore, the bearing capacity of joints with through brace in tension is much higher than that of relevant gapped specimens. The research indicates that the bearing capacity formulae of CHS-to-SHS partially overlapped N-joints in the current codes are not suitable for the joints under the failure mode of chord plasticity, as well as the effect of hidden seam welded or not. The influence of loading hierarchy reversal of braces and axial compression in the chord of both sides of the joints is not taken into account in the formulae, which still needs to be improved.