Cold forming is a method used in stainless steel manufacturing that doesn’t require heat. Cold-formed steel is popular in the building industry due to its light weight, high strength and stiffness, and ease of installation. In many instances, cold-formed steel is produced with openings or perforations that accommodate building services (e.g., plumbing, electrical, and heating systems). While this maximizes clearance it also causes a degradation in both the buckling capacity and the strength of perforated members in compression, shear, or flexure. Current standards and specifications limit the newly developed direct strength method of design to perforated members in compression and bending.
Researchers sought solutions to allow DSM design of perforated cold-formed members to be used for shear. The paper in the Journal of Structural Engineering by Duy Khanh Pham, Song Hong Pham, Viet Binh Pham, Cao Hung Pham, and Gregory J. Hancock, “Direct Strength Design of Cold-Formed Channels with Web Openings in Shear,” offers two SDSM proposals for perforated cold-formed channels with different web opening shapes. Learn more about their research at https://doi.org/10.1061/JSENDH.STENG-11793. The abstract is below.
Abstract
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.
Learn more about using perforated cold-formed steel members when designing structures for shear in the paper in the ASCE Library: https://doi.org/10.1061/JSENDH.STENG-11793.
