Investigation on sheathing effect and failure modes of gypsum sheathed cold-formed steel wall panels subjected to bending

Abstract

Sheathings and external covering becomes an essential part of the structures, especially when the structure is constructed using cold-formed steel (CFS). Conventionally, the contribution of attached sheathing was ignored in the design of the CFS structural members, but in the recent times, the sheathing effect is being incorporated in the design by American Iron and Steel Institute (AISI) specifications to improve the structural economy. A latest report by AISI titled “Sheathing Braced Design of Wall Studs - RP13-1” covers various sheathing configurations such as non-identical sheathings, single-sided sheathing, and fastener spacings. However, the validation of the AISI report for the flexural loading case is not yet carried out. Hence, a comprehensive investigation has been undertaken in the present work to address the effect of sheathing, associated failure modes, and appropriateness of AISI design specifications, when the sheathed CFS panel is subjected to bending. This paper presents the results of 12 full-scale (2400 mm long) CFS sheathed panels subjected to out-of-plane bending followed by design predictions using the current AISI specifications. Three different CFS studs based on global slenderness values (λe) were investigated with 4 different sheathing configurations. The experimental results indicate that the efficacy of sheathing increases with the increase in global slenderness of CFS studs. In addition, numerical studies of sheathed CFS wall panels based on a simple finite element modeling method suggested by the previous researchers is carried out, and the appropriateness of the model is verified. The design prediction results using the AISI specifications indicates that the effect of sheathing is overestimated, thereby leading to unconservative prediction for most of the sheathed CFS wall panel specimens.