Direct stiffness-strength method: An alternative design approach to aisi for sheathed cold-formed steel z-section structural members subjected to bending

This paper presents a design approach, the direct stiffness-strength method (DSSM), for the strength prediction of sheathed cold-formed steel (CFS) structural members. The DSSM considers each sheathing-fastener connection as a bracing point and incorporates its stiffness and strength in the CFS wall panel design. The DSSM is formulated and validated based on large experimental test results. The motivation for this work is to address research gaps in the latest American Iron and Steel Institute (AISI) standards for the sheathing braced design of CFS structural members. A total of 41 individual sheathing-fastener connection tests were carried out, including parameters such as four different sheathing board types (to account for the performance of different sheathing) and seven different dimensions of the CFS Z-sections (to account for the slenderness). A new set of expressions was formulated to predict the stiffness and strength of the individual sheathing-fastener connections (bracing points) based on the observations from tests. A design-oriented assessment (comparing the design results with full-scale wall panel test results) indicated that the expressions formulated for DSSM are appropriate for the use of sheathed CFS Z-section member design. Further, this study used a design example to demonstrate the appropriateness of the DSSM approach.