主管内填充混凝土矩形钢管桁架受力性能试验研究

Experimental research on mechanical behavior of RHS trusses with concrete-filled in chord

为研究主管内填充混凝土对矩形截面钢管桁架受力性能的影响,并考虑节点偏心作用,进行了支主管宽度比β为0.8的空钢管桁架、受压主管内填充混凝土桁架和拉压主管内均填充混凝土桁架的对比试验。试验研究表明:结构破坏均发生在节点部位,主管内填充混凝土改变了节点失效模式,其中空钢管桁架为节点部位的受压主管表面塑性失效和侧壁鼓曲,受压主管内填充混凝土桁架为节点部位的受拉主管表面塑性失效和侧壁鼓曲,拉压主管内均填充混凝土桁架为节点部位的受拉主管表面冲剪失效。主管内填充混凝土不但能协助主管受力,而且能够提高节点强度和刚度,提高桁架的整体承载力。节点相对偏心较大时,由偏心造成的次应力比较明显,对支管的影响要比对主管的影响大。节点试验承载力比按相关规范的计算承载力要高出较多,计算结果偏于安全。

To examine the effect of mechanical behavior on rectangular hollow section （RHS） steel tube truss wltn me concrete-filled in chords, tests on three RHS steel tubular trusses with branch and chord width ratio β= 0. 8 under static point loading at middle span were carried. The first specimen was a RHS truss, the second one was a RHS truss with concrete-filled in the compression chords, and the third one was a RHS truss with concrete-filled in both compression and tension chords. The test results show that the failure of the three truss models are due to the joint failure, however the failure modes are different. The concrete-filled in chord changed the failure mode, the first model is due to the compression chord wall yielding with side wall buckling, the second one is due to the tension chord wall yielding with side wall buckling, and the third one is due to the flange punching failure mode of tensile chord wall which connected with the tensile branch. The deflection and strength of joints dominate the whole truss mechanical behavior. The concrete-filled in chord can not only help reinforced chord members, but also enhance the strength and rigidities of joints, increasing the ultimate bearing capacity of the whole trusses. While the joints eccentricity is larger than the limits of specifications, its effects should be considered, and the effects on members is obviously, with a greater effect on chords than branches. The bearing capacity of test results is lager than the calculation results according to current specifications.