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FIRE-INDUCED PROGRESSIVE COLLAPSE OF BRACED STEEL STRUCTURES

机译:钢筋钢结构的火灾引起的渐进倒塌

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This paper investigates progressive collapse mechanisms of braced steel frames subjected to ground floor fire scenarios using OpenSees, an open-source object-oriented software developed at UC Berkeley.The OpenSees framework has been recently extended to deal with structural behavior under fire conditions by authors.The study considers two types of bracing systems (vertical and hat bracing) The thermal expansion of heated beams at early heating stage and their catenary action at high temperature have great influences on the collapse mechanisms.The vertical bracing systems has positive effects on increasing the lateral restraint of the frame against local or global drift, while when arranged at Edge Bays of frames they negatively contributes to the spreading of a local damage to a global collapse in the form of sequential buckling of adjacent columns through load-transfer mechanisms.Instead, using hat bracing can effectively optimize the load-transfer path through a more uniform redistribution of loads in columns and enhance the resistance of structures against progressive collapse.The application of vertical bracing systems alone on the steel frames to resist progressive collapse is proved to be unsafe and a combined vertical and hat bracing system is recommended in the practical.
机译:本文使用加州大学伯克利分校开发的开源面向对象软件OpenSees,研究了发生地下火灾的支撑钢框架的渐进倒塌机制。作者最近扩展了OpenSees框架,以处理火灾条件下的结构行为。研究考虑了两种类型的支撑系统(垂直支撑和帽子支撑):受热梁在早期加热阶段的热膨胀及其在高温下的悬链作用对坍塌机理有很大影响。垂直支撑系统对增加侧向支撑有积极作用限制框架不受局部或全局漂移的影响,当布置在框架的边缘湾时,它们会通过载荷传递机制以相邻柱的顺序屈曲的形式,不利于局部破坏的蔓延,从而破坏全局崩溃。帽子支撑可以通过更均匀的重新分配有效地优化载荷传递路径立柱中的荷载支撑并增强结构抵​​抗渐进倒塌的能力。事实证明,在钢框架上单独使用竖向支撑系统抵抗渐进倒塌是不安全的,因此在实践中建议将竖向和帽子支撑组合使用。

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