Behavior of built-up cold-formed steel I-section wall studs

An experimental investigation was conducted to study the behavior of built-up cold-formed steel studs and to determine if the modified slenderness ratio in the AISI specification is valid for cold-formed steel members. The study focused on the capacities of built-up I-sections commonly found in the metal building industry and the light-steel framing industry. Typical applications include framing for windows, doorways, shear walls, ends of walls, and multi-story cold-formed steel framed buildings in which the lower floor utilizes built-up studs to carry the load. The built-up studs consisted of two C-sections oriented back-to-back forming an I-shaped cross section. For each specimen, the studs were connected to each other with two self-drilling screws spaced at a set distance. A track was connected running perpendicular to each end with a single self-drilling screw through each flange of the C- sections. The purpose of the track is to keep the ends of the studs together and represents a common end attachment. As a result of the investigation, the current design requirements were found to be conservative in predicting the ultimate capacity of built-up studs. Test results indicated that the modified slenderness ratio is not necessary for thicker materials (0.045 inches and 0.054 inches). However, it needs to be adjusted in order to be used with thinner materials (thinner than 0.045 inches) --Abstract, page ii