Impact of Fastener Spacing on the Behavior of Cold-Formed Steel Shear Walls Sheathed with Fiber Cement Board
As cold-formed steel (CFS) is progressively used in high seismic regions as part of the designated lateral force resisting system, it is necessary to explore higher capacity systems. Furthermore, these systems must be fully enabled within relevant design specifications. The objective of this work is to provide design guidelines and performance benchmarks for cold-formed steel shear walls sheathed with fiber cement board (FCB). High-fidelity three-dimensional finite element modeling is introduced by investigating wall aspect ratio, and fastener spacing pattern. Herein, fasteners, which represent the critical load path in CFS shear walls, are modelled via experimentally-derived phenomenological models. An experimental program of monotonic and cyclic connection testing is conducted aiming to shed light on the response of cold-formed steel to fiber cement board sheathing connections. Connection backbone parameters are extracted from the experimental results and are implemented in the finite element model. As fastener spacing is decreased, failure mode shifts from fastener-dominant to the steel framing itself. This work aims to characterize this change in limit state and provide recommendations for design. Updates to AISI S400 are proposed, specifically in providing prescriptive design aids for the practicing engineer. Furthermore, the high-fidelity modeling approach expanded upon herein provides an analytical approach to explore the impact of detailing on wall performance. Fiber cement board-sheathed shear walls represent a wealth of design potential in increasing the lateral capacity available in cold-formed steel shear wall systems. This work provides the fundamental behavioral and limit state analysis towards eventual enabling within national specifications.