Behaviour of steel-concrete composite columns at elevated temperature

由于2001年9月11日纽约世贸中心两座塔楼倒塌，人们对结构耐火的兴趣有所增加。我们的加拿大国家建筑规范正在成为一个以客观为基础的规范，其中包含规定和基于性能的要求。虽然规范中有一些关于计算火灾下钢筋混凝土柱的强度折减的规定，但对于火灾下钢-混凝土组合柱(混凝土中包裹的型材)的强度折减的规定过于简单化。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镜方法来近似二阶效应。然而，CSA A23.3没有关于确定柱强度的规定，其中包括火灾影响。此外，由申请人为之前的钢筋混凝土和钢-混凝土复合柱研究开发的理论模型和相关计算机软件将扩展到包括火灾影响的研究，并将用于拟议的研究计划。理论模型将与从已发表的文献中收集的物理试验进行比较，然后用于计算机模拟柱的全面参数研究，以评估已发表的设计公式，并检验采用和/或修改弯矩放大器法(CSA A23.3)在计算特定火灾持续时间下的钢筋混凝土和钢-混凝土组合柱的强度的适用性。研究项目的结果和建议将用于准备CSA A23.3的示范条款草案和设计公式，使执业工程师能够直接计算钢筋混凝土和钢-混凝土组合柱在设计荷载(S)和规定持续时间的火灾下的强度。

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.