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结合某超高层钢结构工程,针对该项目中拟采用的中厚壁、大直径钢管混凝土节点可能存在的层状撕裂问题进行试验研究。依据CECS28:90规范设计了两种不同构造的内置加劲环节点,对其进行的加载试验表明:该节点具有较高的承载力和变形能力,塑性铰出现在梁柱交接处,若焊接稍有缺陷则很有可能发生层状撕裂现象。在此基础上,提出了对梁端翼缘进行变截面扩展处理的改进型节点,并重新进行试验及相应的有限元分析。研究表明:改进型节点塑性铰位置明显偏离了节点区域,有效改善了节点的受力状况。按弹塑性非线性有限元分析得到的节点破坏形态、应力分布状况和极限承载力与试验实测结果基本吻合,证明工程设计所采用的分析理论符合节点的实际工作状况,所提出的变截面坡度为1∶1的小扩展形式构造措施可以避免层状撕裂的发生。
Combined with a super high-rise steel structure project, a study on the possible layered tear problem of medium-thick-walled and large-diameter concrete filled steel tubular nodes to be used in the project is conducted. According to the CECS28: 90 standard, two different built-in stiffener joints are designed. The loading tests show that the joint has high bearing capacity and deformation capacity, plastic hinge appears at the junction of beam and column, Defects are most likely to have lamellar tearing. On this basis, an improved node with variable section expansion of the beam end flange is proposed, and the experiment and the corresponding finite element analysis are carried out again. The results show that the position of the plastic hinges in the improved joints deviates obviously from the node area, which effectively improves the stress state of the joints. According to the elasto-plastic nonlinear finite element analysis, the failure morphology, the stress distribution and the ultimate bearing capacity of the joints are in good agreement with the experimental results. It proves that the analytical theory adopted in engineering design conforms to the actual working conditions of the joints. The proposed slope gradient is A 1: 1 extension of the small form of construction measures to avoid the occurrence of lamellar tearing.