Development of Design Guidelines for Steel Cantilever Beams in Canada

北美许多平面面积较大的轻型单层钢结构建筑，如超市或大型箱式商店的屋顶，都是使用“格伯系统”来抵抗重力荷载。Gerber系统由支撑在柱顶部的悬臂梁和沿柱线沿着一个方向的间隙式插入梁段组成，通常在垂直方向上由空腹钢托梁构成次级框架。该系统倾向于通过利用柱支撑处主梁的负弯矩能力来减小主梁尺寸，同时保持与简支框架结构相似的成本。在这种系统中，主梁的设计通常取决于其稳定性。现行的加拿大钢结构建筑设计标准CSA S16提供的Gerber系统相关信息非常有限，因此结构工程师有责任制定合理的设计方法。值得注意的是，一些主要的行业专家担心，广泛使用的教科书和指南可能没有充分描述这种系统的行为和阻力。本研究计划旨在发展钢格伯系统的设计方法，并有四个具体目标：1）确定与悬臂梁稳定性有关的影响参数; 2）通过数值模拟和全尺寸试验程序评估此类梁的稳定性响应; 3）为Gerber系统和其他吊杆开发设计方法，并在加拿大钢结构设计标准的框架内提出稳定性设计要求;（4）进行可靠性分析。研究小组将进行全面的实验室实验，并采用先进的数值模拟技术，以实现这一项目的目标。研究结果将为结构工程师提供改进的设计工具，用于日常实践，从而在降低建筑成本的同时实现更安全的结构。从这里提出的实验测试程序获得的数据将补充现有的研究，以灌输更大的信心，悬臂梁的设计方程的有效性规定。

The roofs of many light single-storey steel buildings in North America that are large in plan area, such as supermarkets or big box stores, are built using the "Gerber system" to resist gravity loads. The Gerber system consists of cantilever girders that are supported atop the columns and interstitial drop-in girder segments along the column line in one direction, typically with open-web steel joists constituting the secondary framing in the perpendicular direction. This system tends to reduce girder sizes by taking advantage of the negative moment capacity of the girders at the column supports, while maintaining a cost similar to that of a simply-supported frame structure. The design of girders in such systems is often governed by their stability. The current Canadian standard for design of steel buildings, CSA S16, provides very limited information related to the Gerber system and it is therefore the responsibility of the structural engineer to develop a rational design method. Remarkably, and of concern to several leading industry experts, widely-used textbooks and guidelines may not adequately describe the behaviour and resistance of such system. This research project aims to develop design methods for steel Gerber systems and has four specific objectives: 1) to identify the influential parameters pertaining to the stability of cantilever girders; 2) to assess, by means of numerical simulations and a full-scale experimental program, the stability response of such girders; 3) to develop design methods for Gerber systems and other cantilevers, and propose stability design requirements within the framework of the Canadian steel design standard; and 4) to perform a thorough reliability analysis. The research team will perform full-scale laboratory experiments and employ advanced numerical modelling techniques to achieve the objectives of this project. The results will provide improved design tools to structural engineers for use in day-to-day practice, resulting in safer structures while reducing construction costs. The data obtained from the experimental test program proposed here will supplement existing studies to instill greater confidence in the validity of the design equations prescribed for cantilever girders.