Behaviour of steel-concrete composite columns at elevated temperature

由于2001年9月11日纽约两座世界贸易中心大楼的倒塌，人们对结构耐火性的兴趣增加了。 我们的《加拿大国家建筑规范》正在成为一项基于目标的规范，其中既有规范性要求，也有基于性能的要求。 规范对火灾下钢筋混凝土柱强度折减的计算有一定的规定，但对钢-混凝土组合柱（外包混凝土的型钢）火灾下强度折减的规定过于简单。 加拿大标准协会混凝土结构设计标准CSA A23.3允许设计工程师在确定框架中细长组合柱的强度时使用弯矩放大系数法来近似二阶效应。 但是，CSA A23.3没有规定确定柱强度，包括暴露于火灾的影响。 由申请人为先前的钢筋混凝土和钢-混凝土组合柱研究开发的理论模型和相关计算机软件将被扩展以包括火灾的影响，并将用于所提出的研究方案。理论模型将进行比较的物理测试，收集从出版的文献，然后被用于计算机模拟列的综合参数研究，以评估出版的设计方程，并检查采用和/或修改的力矩放大器的方法（CSA A23.3）的适用性计算强度的钢筋混凝土和复合钢-混凝土柱受到指定的火灾持续时间。研究项目的结果和建议将用于为CSA A23.3准备草案模型条款和设计方程，以允许执业工程师直接计算承受设计荷载和规定持续时间火灾的钢筋混凝土和钢-混凝土组合柱的强度。

Interest in fire resistance of structures has increased as a result of the collapse of the two World Trade Centre towers in New York, September 11, 2001.  Our Canadian National Building Code is in the process of becoming an objective-based code containing a mixture of both prescriptive and performance based requirements.  The Code has some provisions for computing the strength reduction of reinforced concrete columns exposed to fire, however, the provisions for the strength reduction of composite steel-concrete columns (steel shapes encased in concrete) exposed to fire are overly simplistic.  The Canadian Standards Association Standard for the Design of Concrete Structures, CSA A23.3, permits design engineers to use the moment magnifier approach to approximate the second-order effects in determining the strength of slender composite columns in frames.  The CSA A23.3, however, does not have provisions for determining column strength that includes for the effects of exposure to fire.      A theoretical model and related computer software, developed by the applicant for previous reinforced concrete and composite steel-concrete column research, will be extended to include for the effects of fire and will be used in the proposed research program. The theoretical model will be compared to physical tests, gathered from published literature, and then be used in a comprehensive parametric study of computer simulated columns to evaluate published design equations and examine the applicability of adopting and/or modifying the moment magnifier approach (CSA A23.3) for computing the strength of reinforced concrete and composite steel-concrete columns subjected to a specified fire duration. The results and recommendations from the research program will be used to prepare draft model clauses and design equations for CSA A23.3 to allow practicing engineers to directly compute the strength of reinforced concrete and composite steel-concrete columns subjected design load(s) and a  fire of prescribed duration.