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“Restrained or Unrestrained?” – AISC & AISI Fund UL Test for Fire Resistance of Unrestrained Assemblies

As a follow up to our July 24, 2013 blog post, and our July 10, 2013 SE University session on Structural Fire Protection, we wanted to bring to your attention a recently published article that looks at unrestrained steel assemblies and beams.

“Restrained or Unrestrained?”, an article in the September 2013 issue of Modern Steel Construction, was written by AISC Vice President and Chief Structural Engineer Charlie Carter, along with Farid Alfawakhiri, a senior engineer for AISI. AISC and AISI recently funded a test on an unrestrained assembly through Underwriter Laboratories, which resulted in UL Design No. D982. The hope is that this will eliminate the questions about whether an assembly is restrained or unrestrained, as now there is a guideline for an unrestrained assembly that is comparable to a restrained assembly.

In this article, the authors note that for most UL tests, a restrained test is performed, and then results for the unrestrained condition are extrapolated from those results. The new test was unique, however, in that it was conducted on an unrestrained specimen, so that direct results for the unrestrained condition could be measured and presented.

Please click on the link to access UL Design No. D982