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911事件以来,意外荷载作用下超高层结构的连续倒塌问题日益受到关注。该文采用考虑高温作用的高性能有限单元、高温破坏准则及生死单元技术,对极端火灾作用下典型超高层混凝土框架-核心筒结构的连续倒塌进行了分析。研究发现,该结构系统中的多层结构共同承受火灾作用时,由于火灾热膨胀变形的影响,超高层框架-核心筒结构产生类似桁架拱的整体受力机制,使得结构体系内不仅在水平方向发生内力重分布,而且在竖向也发生内力重分布。楼盖系统的热膨胀和破坏失效对外围柱的破坏具有重要影响,最终造成外围柱由于较大的二阶效应而发生受弯破坏,触发了整体结构系统的连续倒塌。
Since the Sept.11 Incident, the problem of continuous collapse of super high-rise structures under the unexpected load has drawn increasing attention. This paper analyzes the continuous collapse of a typical super high-rise concrete frame-core tube structure under the action of extreme fire by using high-performance finite elements, high-temperature failure criteria and life-and-death element technology, which consider the effect of high temperature. It is found that when the multi-layer structure in the structural system is subjected to the fire effect, the whole force mechanism similar to the truss arch in the super-tall frame-core tube structure causes the structural system to not only occur in the horizontal direction Internal force redistribution, but also in the vertical internal force redistribution. Failure of thermal expansion and failure of the floor system has an important influence on the failure of the peripheral columns, eventually resulting in the bending failure of the peripheral columns due to the large second-order effect and triggering the continuous collapse of the whole structural system.