隔板贯通式箱型柱-H型钢梁节点循环加载试验和破坏机理分析

REVERSED LOADING TESTS AND FRACTURE MECHANISM OF JOINTS CONNECTING A STEEL BOX COLUMN AND H-SECTION STEEL BEAM WITH THROUGH DIAPHRAGMS

对4个双折线隔板贯通式箱型中柱-H型钢梁节点和1个常规节点进行了低周往复循环加载试验,基于考虑焊接缺陷和焊接残余应力的结构钢椭球面断裂模型及偶联的椭球面屈服模型的断裂机理分析,对比研究了双折线扩大头构造对隔板贯通式箱型中柱-H型钢梁节点破坏模式、延性、承载力、刚度退化和耗能性能的影响,揭示了隔板贯通式箱型中柱-H型钢梁节点在强震时断裂和屈服的演化规律。结果显示,常规节点在几何不连续的梁翼缘对接焊缝侧边脆断,节点塑性转角约为0.02rad,达不到FEMA要求的0.03rad。双折线扩大头型节点在隔板折线段内形成塑性铰,节点塑性转角达到0.03rad,承载力和耗能性能较常规节点分别提高10.1%~27.7%和65.5%~123.6%。双折线扩大头构造和梁翼缘对接焊缝移至远离节点区的措施,减缓了节点区的几何突变和应力集中,规避了节点区焊缝过于密集和焊接热影响区的交叉影响,防止了节点过早脆断。该文给出了双折线扩大头节点的构造设计建议。

Low-reversed loading tests and fracture mechanism analysis were performed on the joints connecting a steel box column and H-section steel beam with through diaphragms, testing four joints with double linear enlarged junctures and one conventional joint, based on an elliptical fracture model coupled with an elliptical yield model taking into account welding defects and residual stress for constructional steel. The effects of double linear enlarged junctures on failure mode, ductility, load bearing capacity, rigidity degradation, and energy dissipation of the joints connecting a steel box column and H-section steel beam with through diaphragms were comparative studied. The evolution law of fracture and yield index near the joint panel zone were developed. The results of tests and numerical analysis show that the conventional joint undergoes brittle fracture at the edges of butt weld between beam flange and through diaphragm, where the geometry is discontinuous, while the plastic rotation is roughly 0.02 rad, which does not meet the minimum requirement(0.03rad) in FEMA. For the joints with double linear enlarged junctures, the plastic hinge forms at the linear enlarged section of diaphragm, the plastic rotation reaches 0.03 rad, and the load bearing capacity and the energy dissipation capacity increase by 10.1%~27.7% and 65.5%~123.6%, respectively, compared with those of the conventional joints. Drastic changes in geometry and stress concentration in the connection zone are mitigated by the use of double linear enlarged junctures, and the overlap and interaction of welds are avoided by moving the butt weld between beam flange and diaphragm to a section far away from the panel zone.