Development of Design Guidelines for Steel Cantilever Beams in Canada

在北美，许多平面面积较大的轻型单层钢结构建筑，如超市或大卖场，其屋顶都是用“Gerber体系”建造的，以抵抗重力荷载。Gerber体系由支撑在柱顶的悬臂梁和沿柱线沿一个方向的间隙插入式梁段组成，通常在垂直方向上由空腹钢托梁构成次要框架。这种体系倾向于通过利用柱支撑处的梁的负弯矩能力来减小梁的尺寸，同时保持与简支框架结构相似的成本。在这类系统中，大梁的设计往往受其稳定性的制约。 现行的加拿大钢结构建筑设计标准CSA S16提供的与Gerber体系相关的信息非常有限，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，被广泛使用的教科书和指南可能不能充分描述这种体系的行为和阻力，这一点引起了几位领先的行业专家的担忧。该研究项目旨在开发钢Gerber系统的设计方法，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实验计划来评估此类梁的稳定性响应；3)开发Gerber系统和其他悬臂的设计方法，并在加拿大钢设计标准的框架内提出稳定性设计要求；以及4)进行全面的可靠性分析。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来实现该项目的目标。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，使结构更安全。从本文提出的试验测试程序中获得的数据将补充现有的研究，以增强对悬臂梁设计公式的有效性的信心。

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.