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分析

Progressive collapse analysis of a typical super high-rise concrete frame-core tube structure exposed to extreme fire

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 ＂9 ·11＂event,the progressive collapse of super high-rise structures under incidental loads has been greatly concerned. In this paper,the high performance finite elements and their failure criteria both considering high temperature effects,as well as the elemental deactivation technology are adopt to analyze the progressive collapse of a typical super high-rise concrete frame-core tube structure exposed to extreme fire. It can be found that when the multistorey floor system in the building structure is simultaneously exposed to fire,it performs an overall mechanism similar with Vierendeel action due to the thermal expansion deformation. That leads to the redistribution of the internal forces throughout the structural system not only in the horizontal direction but also in the vertical direction. Thermal expansion and the destruction of the floor system have an important influence on the failure of peripheral columns,which eventually leads to the flexural damage of the columns due to the large second-order effect,triggering the progressive collapse of the structure system.