Duy Khanh Pham; Song Hong Pham, Viet Binh Pham, Cao Hung Pham



In the current standards/specifications for cold-formed steel structures, the direct strength method (DSM) has not been developed for the shear strengths of perforated members, which is currently based on an empirical design approach using a qs factor.

To extend the DSM design to members in shear with various hole shapes and sizes, new design procedures have been developed to determine shear loads including the elastic shear buckling load (Vcrh), shear yield load (Vyh), and ultimate shear strength (Vn). Vcrh can be calculated via a linear approximation for buckling coefficients (kv) based on the hole and section dimensions.

Vyh can be computed based on a theoretical Vierendeel mechanism or a proposed alternative simplified model to permit an easier implementation in design checks. Vn can be determined using proposed DSM shear curves for members with and without full-transversely stiffened webs.

To validate the new DSM approach, a collection of reliable historical experiments in perforated sections under shear was used for strength comparison. The experimental shear strengths were also further used for the calibration of the DSM-based proposal to determine the resistance factor (ϕ) for shear design, which is traditionally based on the LRFD methodology.