中空夹层钢管混凝土-钢管K形搭接节点抗震性能试验研究

Experimental research on seismic behavior of overlapped K-joints connecting concrete-filled double skin steel tube and steel tube

主管为中空夹层钢管混凝土,支管为空钢管的K形搭接节点,按主圆支圆和主方支圆两种形式加工制作了4个节点,对节点两个支管通过同步往复加载,研究主管通过夹层混凝土加强的K形节点破坏模式、承载力、耗能性能等。分析了试件的滞回曲线、骨架曲线、承载力、延性系数、能量耗散系数等抗震性能指标。结果表明:未加强节点的破坏模式为主管表面塑性破坏,主管夹层灌混凝土的加强节点为支管拉裂破坏;主管夹层灌混凝土提高了节点的刚度和承载力,对于方管尤为显著,但对节点的延性影响不大;相比主圆支圆的未加强试件,夹层灌普通混凝土和粉煤灰混凝土的试件承载力分别提高了43.7%和52.1%,节点累积耗能分别提高了57.6%和64.0%;相比主方支圆未加强试件,夹层灌普通混凝土和粉煤灰混凝土的试件承载力分别提高了66.7%和64.7%,节点累积耗能分别提高了39.8%和21.7%,但主管夹层灌普通混凝土和灌粉煤灰混凝土对节点的加强效果区别不大。利用ANSYS软件对试验试件进行有限元分析,分析结果与试验结果吻合良好,并选用主管空心率、支主管直径比及支管径厚比进行参数分析。分析表明:随主管空心率的增大,节点耗能能力和承载力有所减小;随支主管直径比的增大,节点滞回曲线趋于饱满,耗能能力和承载力提高;随支管径厚比的增加,节点的滞回曲线的饱满度降低,节点承载力和耗能能力均呈下降趋势。

The overlapped K-joints are composed of the chord with concrete-filled double skin steel tubes and the empty braces.A total of four joints were fabricated into two forms:circular chord and circular braces,square chord and circular braces.By loading the braces with collaborative cyclic load,the overlapped K-joints with chord strengthened by concrete-filled double skin were tested to investigate the failure mode,bearing capacity,energy consumption performance etc.The hysteresis curve,skeleton curve,bearing capacity,ductility coefficient and energy dissipation coefficient of the specimens were analyzed.The results show that the failure mode of the unstrengthened joints are the plastic deformation of the chord surface,but the strengthened joints with concrete-filled double skin steel tubes fail into the tensile damage of the braces.The concrete-filled double skin enhances the stiffness and bearing capacity of the joints,especially for the joints with square chord and circular braces,but has little effect on the ductility of joints.Compared with the unreinforced specimens with circular chord and brace,the bearing capacity of the specimens with grouted sandwich filled with ordinary concrete and fly ash concrete increases by 43.7%and52.1%respectively,and the cumulative energy consumption of joints increases by 57.6%and 64.0%respectively.Compared with the unreinforced specimens with circular chord and brace,the bearing capacity of the specimens with grouted sandwich filled with ordinary concrete and fly ash concrete increases by 66.7% and 64.7% respectively,and the cumulative energy consumption of joints increases by 39.8% and 21.7% respectively.However,there is little difference between the strengthening effect of the joints strengthened by the ordinary concrete and the joints strengthened by the fly ash concrete.The ANSYS software was used to analyze the hysteretic behavior of test specimens.The results of analysis were in good agreement with the test results.The parameters of hollow ratio,diameter ratio of brace and chord,diameter-thickness ratio of brace were selected for parametric analysis.It is shown that with the increase of hollow ratio,the energy dissipation capacity and bearing capacity of the joints decrease.With the increase of diameter ratio of brace and chord,the hysteretic curve of the joints tends to be full,the energy dissipation capacity and the bearing capacity increase.With the increase of diameter-thickness ratio of brace,the saturation of the hysteretic curve of the joints decreases,and the bearing capacity and the energy dissipation capacity of the joints decrease.