平面K形圆主管方支管节点承载力试验研究与有限元分析

Experimental research and finite element analysis of bearing capacity of K-joints with circular chord and square braces

对平面K形圆主管方支管节点的承载力进行试验研究,进行了5个空钢管节点和1个主管内灌混凝土节点的静力单调加载试验。介绍了节点试验方案,考察了节点的受力性能、破坏模式和承载力,给出了试件支管的变形曲线以及折算应变曲线,并对支管壁厚、主管内浇灌混凝土对节点承载力、刚度和延性的影响进行了分析。试验结果表明:现行国内外规范中圆钢管和方钢管节点承载力计算值明显低于试验值,已有的计算公式都不能准确计算圆主管方支管节点的承载力;增加支管壁厚改变了节点的破坏模式并明显提高了节点承载力和延性;主管内灌混凝土虽提高了承载力和初始刚度但延性并没有得到显著提高;圆主管方支管节点区域的变形主要源于受拉支管的局部变形。在节点破坏模式、变形曲线、承载力和塑性发展等方面将有限元计算值与试验结果进行比较,结果吻合良好,可以作为进一步分析的基础。

In order to obtain the bearing capacities of K-joints with circular chord and square braces,five specimens of hollow section K-joints and one K-joint with concrete filled steel tubular chord were tested under monotonic loading.The test procedure,mechanical behavior,joint failure mechanism,joint bearing capacities,load-displacement plots of specimens and braces,and strain intensity plots are presented in this paper.The effects of the thickness of braces and concrete in chord on the bearing capacity,stiffness and ductility of joint were also discussed.Results of tests show that： firstly,by comparing the calculated results of the ultimate capacity of tubular joints according to the current codes with those obtained from the tests,it is proved that the available design guideline about tubular K-joints such as the circular and square hollow section K-joints can only poorly predict their bearing capacities,which are obviously lower than the test results.The main reason may be that the thickness of brace changes the joint failure mode and increases the bearing capacities and ductility.Secondly,although the bearing capacities and initial stiffness of joints with concrete filled steel tubular chord are higher than those of the hollow joints,the ductility levels of both joints are very close.Thirdly,the displacement of this kind of joint is mainly caused by the local displacement of the tensile brace.Finally,the joint failure,load-displacement plots,bearing capacities and plastic zone development are investigated numerically by finite element analysis.Compared with the experimental results,it is proved that FEA is reliable and further analysis can be based on the FEA.