Box-beam headers are commonly used in walls framed with cold-formed steel studs to span openings in bearing walls. Based on the results of previous experimental studies, it has been shown that box-beam headers subjected to interior one flange (IOF) loading have been conservatively designed. This paper presents the results of an ongoing experimental study conducted at the University of Missouri-Rolla to establish the web crippling strength of box-beam headers for an IOF loading condition. Box-beam header specimens were tested as a system consisting of two C-sections together with top and bottom track sections. The header configuration used in this study is defined in the AISI publication Standard for Cold-Formed Steel Framing ― Header Design (2000). Tested as a system, it was found that the web crippling strength was greater than that for two independent, single web C-sections. Based on the results of this study, an adjustment factor was developed to modify the web crippling strength determined using the AISI Specification for single web C-sections. An interaction equation was also derived for combined bending and web crippling.
展开▼
