Overview of the Standard for Seismic Design of Cold-Formed Steel Structural Systems — Special Bolted Moment Frames

Abstract

Cold-formed steel has been widely used for components and main force resisting systems in commercial, industrial, and residential buildings. Coldformed steel structural members are designed using AISI S100, North American Specification for the Design of Cold-Formed structures Members [AISI, 2007a]. For applications in high seismic regions, additional requirements may be needed. In fact, cold-formed steel design standards have been developed for applications in high seismic regions for both rack structures [RMI, 2004] and cold-formed steel light frame construction [AISI, 2007c]. In 2003, the American Iron and Steel Institute (AISI) established a seismic design committee. Composed of suppliers, manufacturers, engineers, researchers and professors, the committee is responsible for developing design standards applicable to cold-formed steel structural systems located in seismic regions. The first edition of the Standard for Seismic Design of Cold-Formed Steel Structural Systems – Special Bolted Moment Frames [AISI, 2007b] (hereinafter referred as the Standard) was finished in 2007. The Standard has also been approved by ANSI and an American National Standard. As the title indicates, this edition of the Standard focuses on the design of the seismic force resisting system for special bolted moment frames, which consist of tubular columns, cold-formed channel beams and bolted moment connections. A typical connection of a cold-formed steel special bolted moment frame (CFS-SBMF) is illustrated in Figure 1. This type of special bolted moment frame is widely used in industrial platform mezzanines such as the one shown in Figure 2. The 2007 edition of the Standard is based on the 2005 edition of the ANSI/AISC 341, Seismic Provisions for Structural Steel Buildings, [AISC, 2007] and research work [Sato and Uang, 2007] on cold-formed steel special bolted 1 Senior Engineer at the American Iron and Steel Institute, Washington, DC, hchen@steel.org 2 Professor of Civil Engineering at University of California – San Diego, La Jolla, CA, cuang@ucsd.edu 3 President of The Bjorhovde Group, Tucson, AZ, rbj@bjorhovde.com 4 Regional Director at the American Iron and Steel Institute, Construction Codes and Standards, Washington, DC, bmanley@steel.org