钢管混凝土柱巨型交叉节点受力性能研究

在一超高层结构工程中，外框架采用了焊接钢管混凝土边柱和夹角为12°的斜柱交叉形成高达6层且与6层楼面梁相接的巨型交叉节点，该节点构造复杂。节点边柱的轴向荷载不平衡在节点处产生剪力，同时，由于斜柱承受的轴向荷载巨大，该巨型节点受力复杂。为研究该节点的受力性能，对其进行了大比例模型加载试验。试验在最不利工况（1.2×重力荷载+1.3×设防地震作用）下： 1) 在设计荷载作用下节点试件整体仍然处于弹性工作状态； 2) 增大边柱不平衡力，对节点试件的平面内侧移有一定的影响，而对平面外变形基本没影响； 3) 对斜柱轴向荷载进行卸载，将节点由压剪转换至更不利的拉剪受力状态，节点未破坏； 4) 施加斜柱轴向荷载超过设计承载力的2倍，节点试件最终在斜柱两端出现局部鼓起而发生破坏，说明该交叉节点的设计符合我国规范“强节点弱构件”的设计原则。在整个加载过程中，节点区域并未产生剪切破坏面，钢管内部设置的纵向内隔板和加劲环板使得钢管与混凝土协同工作，节点构造合理。通过合理的简化，对该节点试件进行了三维非线性有限元分析，其荷载 变形曲线以及破坏模式与试验结果吻合良好。

Mechanical behavior of huge crossover joint between twoconcrete-filled steel tubular columns

In the exterior frame of a super high-rise building, an inclined column and a side column, both being concrete-filled steel tubular columns, intersect with a small angle of 12° to form a huge joint with a height over six stories, and the joint is also connected with six floor beams. Unbalanced axial force exists in the side column over the joint, resulting in unfavorable shear load along the crossover joint. The inclined column is subjected to extremely large axial force. In order to validate its load transfer mechanism, a large-scale test on the joint was conducted in four stages considering the most unfavorable load combination of 1.2 times gravity load and 1.3 times design earthquake action. The test result shows that: in the first stage with design load, the specimen remains in elastic state; secondly, a large increase of unbalanced axial force in the side column has some influence on in-plane lateral displacement and little effect on out-of-plane lateral displacement; thirdly, the specimen remains safe during transition from compression-shear load to tension-shear load through unloading the axial load on the inclined column; lastly the specimen reaches its load carrying capacity which is over twice the design load, and the failure mode exhibits local bulge at both ends of the inclined column due to buckling under compression. There is no obvious deformation within the joint region up to failure, indicating that the design of the crossover joint satisfies the ‘strong-joint-weak-member’ requirement of Chinese design code. Interior vertical stiffeners and interior steel rings make the steel tubes and concrete work together, preventing obvious shear failure in the joint in the whole process. A 3-D nonlinear finite element model was developed to simulate the mechanical behavior of the crossover joint. The load-deformation curves and failure mode predicted by finite element analyses show good agreement with those of the experiment.