Flexural Strength of Cold-Formed Steel Members with Edge-Stiffened Slotted Web Openings

Slotted holes or circular utility holes are commonly found in the web of cold-formed steel joists (CFS). These holes are used for piping, plumbing, or electrical wiring. Usually, these utility holes are unstiffened. Cold-formed steel has recently been considered as the best material for low-rise building construction as well as for roof and floor systems based on performance, cost, safety, and ultimately sustainability considerations. The current North American Specification for the Design of Cold-Formed Steel Structural Members does not provide the design provision for the stiffened holes. This paper will present the finite element analysis of CFS members with circular, slotted, and tri-slotted holes with edge stiffening to study the effect of stiffened holes on the stability of the member when subjected to flexural loading. The optimized profile of the stiffened holes is obtained using the elastic buckling analysis. The post buckling finite element analysis is used to determine member flexural strength as affected by the hole dimensions and web depth. The finite element analysis shows that the stiffened holes can significantly improve the flexural strength of the CFS joist. New design provisions are proposed to predict the flexural strength of such joists with the presence of slotted holes.