中柱失效下多层框架的连续性倒塌分析与机理研究

Progressive collapse analysis and mechanism study for multi-story frame structures with middle-column demolition

进行抗连续倒塌分析时,常将多层框架结构简化为单层子结构,然后将单层结构的特性用于多层框架的研究,但目前的简化模型不能够完全反映结构整体受力特性,忽略了空腹机制的作用。基于两跨梁模型研究单层框架的抗倒塌机制,提出梁机制和悬链线机制的抗力计算方法,并通过算例验证了所提方法的正确性;为分析空腹机制对多层框架整体受力的影响,建立顶层梁柱模型,引入空腹机制对抗连续倒塌的贡献指标;分析俄亥俄综合大楼拆除四根柱后的抗倒塌机制。结果表明简化模型是合理的,多层框架结构顶层和底层表现出不同的倒塌机制,空腹机制与其它机制共同抵抗不平衡荷载,俄亥俄综合大楼具有较好的抗连续倒塌性能。

Multi-story frame structures are often simplified as single-story substructures to study their progressive collapse resistance, in which a single-story substructure is studied and its behavior is applied to multi-story frame analysis. However, due to ignoring the effect of the vierendeel mechanism, the current simplified model could not fully reflect the mechanical behaviors of the whole structure. Based on a double-span beam model, the collapse mechanism of the single-story substructure was studied, and a resistance calculation method for the beam mechanism and catenary mechanism was proposed, which was then validated by numerical examples. To analyze the effect of the vierendeel mechanism on the overall behavior of multi-story frames, a top-floor substructure model was established, and the contribution index of the vierendeel mechanism against the progressive collapse was introduced. Incorporating with the above models, the process of demolishing four columns of the Ohio Union building was simulated. The results show that the simplified models are reasonable. The top and bottom stories of the multi-story frame show different anti-collapse mechanism, and the vierendeel mechanism together with other mechanisms resist the unbalanced load. At the same time, it is found that the Ohio Union building has good resistance to progressive collapse.