Axial Strength Determination for Gypsum-Sheathed, Cold-Formed Steel Wall Stud Composite Panels

Abstract

Composite panels in this study consist of C-section steel wall studs with gypsum wallboard attached to both flanges of the stud with screws at regular intervals. Axial load is assumed to be applied to the centroid of the gross cross section for each stud. Bracing from the wallboard, connected by screws, is represented by elastic springs in the analysis. The panel is subject to both flexural and torsional-flexural buckling modes. Using the differential equation of equilibrium, the flexural and torsional-flexural buckling loads are evaluated for typical end-conditions. Local buckling effects and nominal buckling stress are determined according to the 1986 and 1996 AISI specifications. Predictions and observed strengths from the limited experimental database are in good agreement. The predictions accurately represent the overall torsional-flexural buckling observed for the gypsum board-braced, steel wall studs. The strength is independent of study spacing, reflecting the localized nature of the wallboard deformations, rather than the shear diaphragm behavior assumed in the current AISI specification.