To study the mechanical behavior of rectangular hollow section (RHS) steel tube joints with concrete filled in chords, mechanical behavior of compression, tension and bending are analyzed in this paper and compared with RHS steel tube joints. The results show that concrete filled in chord can improve the mechanical behavior of joints. It can obviously enhance the ultimate bearing capacity and rigidity of compression joint, and the failure mode of compression joints is local transverse compression failure. It does not have much effect on the ultimate bearing capacity of tension joints, but can enhance the rigidity of joints; and it can change the range of geometric parameters of failure mode; the failure modes of tension joint are punching failure mode, effective width failure mode and flange yield-line failure mode. The bending rigidity and ultimate bending capacity of joints are greater than RHS steel tube joints, and the failure mode of bending joints is considered as tension flange effective width failure mode of branch tube. The bearing capacity formula for three types joint are recommended according to its failure modes.%为研究主管内填混凝土对矩形钢管节点受力性能的影响,探讨主管内填混凝土矩形钢管节点的受力机理,对比分析了主管内填混凝土矩形钢管节点和空钢管节点的受压、受拉和受弯性能,结果表明主管内填混凝土能够改善节点的受力性能,显著提高矩形钢管受压节点的承载力,受压节点的破坏模式转变为横向局部承压破坏;对矩形钢管受拉节点承载力提高不明显,但提高了节点的刚度,改变节点的破坏模式;能够提高受弯节点的刚度和承载力,其破坏模式可采用支管受拉翼缘有效宽度模型.主管内填混凝土后矩形钢管节点的承载力可根据对应的破坏模式来计算.
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