Cold-Formed Steel Back-to-Back Header Assembly Tests

Authors: NAHB Research Center Inc.    

The purpose of this test program was to investigate the structural capacity and performance of built-up headers typically used in cold-formed steel framing. The configuration of the headers tested was limited to doubled, back-to-back C-sections assembled in accordance with the Prescriptive Method for Residential Cold-Formed Steel Framing (Prescriptive Method). Currently, allowable spans of header assemblies are typically determined by doubling the allowable capacity of a single C-section (one of the two member built-up header assembly) as calculated in accordance with the Specification for the Design of Cold-Formed Steel Structural Members (AISI Design Specification). This conservative assumption and simplified design approach under-estimates the actual performance of the header assembly resulting in an uneconomical design and unnecessarily short header spans, particularly with thin deep sections. The findings of this study demonstrate that much greater header spans are possible with improved design rules.

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