K形、KK形钢管混凝土相贯节点力学性能研究

Mechanical behavior of concrete-filled K- and KK-type CHS connections

为研究K形和KK形钢管混凝土相贯节点的力学性能,设计3个足尺钢管混凝土相贯节点试件,并通过对节点支管进行轴向拉压试验,获得试件的破坏模式、荷载-位移曲线和极限荷载等。试验结果表明:K形和KK形薄壁钢管混凝土相贯节点在支管轴向拉压力作用下的破坏模式均为主管冲剪失效,且在支管受拉侧和受压侧,主管最大位移与主管直径之比分别为1.75%和0.25%,均小于CIDECT-1中确定值(3%)。在试验研究基础上建立节点有限元模型,基于节点试件的荷载-位移曲线及冲剪承载力,验证有限元模型建立及分析过程的准确性,并进一步开展K形和KK形节点的冲剪破坏面的应力分布分析以及KK形节点支管作用对剪应力分布及冲剪承载力的影响分析。研究结果表明:K形节点冲剪破坏面剪应力对称分布,而KK形节点剪应力分布不再对称;KK形节点中K形支管的几何形状及荷载均对冲剪承载力及剪应力分布有影响。最后,将CIDECT-1、EC 3、AISC 360-16和GB 50017—2017等规范中的空钢管相贯节点的承载力计算公式及现有的T形和Y形钢管混凝土相贯节点的冲剪承载力计算公式的计算值与试验值、有限元模拟值进行对比分析,提出适用于K形和KK形钢管混凝土相贯节点在支管轴向拉压力作用下的冲剪承载力计算式。

The mechanical behavior of concrete-filled K-and KK-type circle hollow section(CHS)connections were investigated in this paper.Three large-scale K-and KK-type CHS connections were tested to failure subject to braces and chord axial loading.The failure mode,load-displacement curve and failure load were obtained.It is shown that the chord-wall punching shear failure is the main failure mode.The chord-wall maximum deformation on the tensile and compressive side are 1.75%and 0.25%of the chord outer diameter,respectively,which are less than 3%as suggested by the CIDECT-1.Furthermore,the validity of the finite element(FE)models was verified by the experimental results,including load-displacement curve and failure load.The validated FE models were used to qualitatively analyze the punching shear stress distribution and the interaction of two K-brace pairs on the failure mode and ultimate strength.The results show that the shear stress distributions on the punching shear failure surface of K-and KK-type connections are symmetrical and asymmetrical,respectively.The geometric profile and load conditions of the K-brace in KK-type connections have an influence on the punching shear load and shear stress distribution.Last but not least,according to the design equation of current code specification for K-and KK-type CHS connections and the punching shear strength design equation for T-and Y-type concrete-filled CHS connections,an ultimate strength formula to predict the punching shear strength for concrete-filled K-and KK-type CHS connections subject to braces and chord axial loading was proposed.