Seismic Design Procedure for Low-Rise Cold-Formed Steel–Special Bolted Moment Frames

Abstract

In 2007, the American Iron and Steel Institute (AISI) established a standard for cold-formed steel–special bolted moment frames (CFS-SBMFs). This structural system is designed to resist seismic forces. The CFS-SBMF system employs double-channel beams and square hollow structural section (HSS) columns that are bolted together to create a sturdy and robust structural frame. However, the CFS-SBMF system is only suitable for constructing one-storey buildings, and ASCE 7 prohibits its use in buildings with a height of over one storey. This study was conducted to expand the use of CFS-SBMFs to the construction of multi-storey low-rise buildings. Firstly, a new moment connection detail is proposed, and a design procedure is proposed to ensure that bolted connections, instead of beams or columns, have the ductility to withstand seismic forces. Secondly, the proposed design procedure for bolted connections was verified through full-scale cyclic testing. Finally, a comprehensive evaluation was undertaken to evaluate the proposed structural system’s performance under seismic excitation. The evaluation included nonlinear dynamic analysis and incremental dynamic analysis (IDA) according to FEMA P695, which provided a detailed understanding of the seismic design factors (SDFs) in multi-storey low-rise CFS-SBMF buildings.