Reinforcement Schemes for Cold-Formed Steel Joists with a Large Web Opening in Flexural Zone - An Experimental Investigation

Abstract

The objective of this investigation is to develop an economical and an efficient reinforcement scheme for large web openings in cold-formed steel (CFS) joists in flexural zones that would restore the original moment resistance of the section. This investigation considered commonly used floor joists in North American CFS construction. Tests on joists webs with no openings and with large circular and square openings located at the mid-depth revealed that large openings may reduce the flexural strength by 23%. A reinforcement scheme consisting of screw fastening of 31.75 mm x 12.7 mm (1-1/2”x1/2”) bridging channels having matching thickness as of the receiving joist, along the compression and the tensile edges of the opening utilizing a screw spacing of 31.75 mm was established. Three identical tests utilizing the proposed reinforcement scheme restored the corresponding flexural strengths of the CFS section under consideration, and the failure locations were outside the reinforced opening regions.