Fire-Exposed Reinforced Concrete Frames: Structural Performance, Progressive Collapse Assessment and Retrofit Strategy

世贸中心（World Trade Center）双塔的倒塌，以及许多有记录的火灾引发的结构故障，引发了人们对公共安全的严重担忧。大多数钢筋混凝土（RC）结构都是使用基于暴露于标准火灾下的RC构件结构测试的规范防火设计方法进行设计的。然而，它们存在着显著的缺陷，包括：结构层面的安全裕度不确定，对渐进倒塌的抵抗能力未知，以及无法考虑复杂自然火灾现象所需的创新成本节约方案。他们也没有提供必要的指导来评估和改造火灾损坏的结构。***通过指定可接受的性能标准或设计目标来实现工程创新，设计标准正在发生革命性变化。这场革命正在导致建筑师和结构工程师之间的消防安全责任平衡发生重大转变，结构工程师需要发展必要的专业知识并配备正确的分析工具。这些工具可以加速设计过程，从而证明与额外工程工作相关的好处。***申请人的研究小组最近开发并验证了简化的方法和工具来分析和设计暴露在标准火灾下的RC框架。这些为研究人员和工程师提供了必要的手段来了解火灾下复杂的结构行为，设计RC框架以满足特定的安全目标，并验证商业计算机程序的分析结果。***拟议的研究将进一步发展申请人的方法和工具，使其适用于自然火灾情况。它们的使用将允许基于性能的新结构设计，并提供考虑到渐进倒塌可能性的评估火灾损坏结构安全性的手段。这样的评估对于在改造之前做出是否需要疏散的关键决定至关重要。应急小组迫切需要这种工具，以便持续监测暴露在火灾中的建筑物的状况，以保证其人员的安全。该研究还将为设计火灾损坏的RC框架的改造技术提供工具，以保证公共安全。***拟议的研究将利用兰姆顿学院消防与公共安全卓越中心独特的消防设施，在西部结构实验室测试之前将RC元件暴露在火中。测试结果将导致上述工具的开发和验证。6名hqp和25名本科生将体验独特的测试程序，包括与Western和Lambton的技术人员互动，并将培养加拿大和全球结构工程专业急需的分析技能。**

The collapse of the towers of the World Trade Center and the many documented fire-initiated structural failures raise grave concerns about public safety. The majority of Reinforced Concrete (RC) structures are designed using prescriptive fire design approaches that are based on structural tests of RC elements exposed to standard fires. However, they possess significant drawbacks including: undefined safety margin at the structure level, unknown resistance to progressive collapse and inapplicability to consider innovative cost-saving solutions demanded by the complex natural fire phenomena. They also fail to provide the needed guidance to evaluate and retrofit fire-damaged structures.***Design standards are being revolutionized by specifying acceptable performance criteria or design objectives to allow for engineering innovations. This revolution is causing a major shift in the balance of responsibility for fire safety between the architect and the structural engineer who needs to develop the necessary expertise and be equipped with the right analytical tools. These tools should expedite the design process allowing for the justification of the benefits associated with the additional engineering work.***The Applicant's research group has recently developed and validated simplified methods and tools to analyze and design RC frames exposed to standard fire. These provide researchers and engineers with the necessary means to understand the complicated structural behaviour under fire exposure, to design RC frames to satisfy specific safety objectives and to validate analysis results from commercial computer programs.***The proposed research will further develop the Applicant's methods and tools to make them suitable for cases of natural fire. Their use will allow for performance-based design of new structures and provide means to assess the safety of fire-damaged structures considering the potential of progressive collapse. Such assessment is essential to make critical decisions about the need for evacuation prior to retrofitting. Emergency response teams are in desperate need of such tools to continuously monitor the condition of fire-exposed structures to guarantee the safety of their personnel. The research will also provide tools to design retrofitting techniques for fire-damaged RC frames that guarantee public safety.***The proposed research will utilize the unique fire facility at Lambton College's Fire & Public Safety Centre of Excellence to expose RC elements to fire before testing them at Western's Structures Lab. Test results will lead to the development and validation of the above-mentioned tools. 6 HQPs and 25 Undergraduate students will experience unique testing procedures involving interaction with technicians from Western and Lambton, and will develop analytical skills that are much needed within the structural engineering profession in Canada and worldwide.**