This page provides information relating to UL Designs and the questions that have been raised about load restriction requirements in the US marketplace. Following is the first article that addresses this topic:
Restrained or Unrestrained?
This article appeared in the September 2013 issue of AISC's Modern Steel Construction magazine.
UL Design Considerations
This article appeared in the October 2015 issue of AISC's Modern Steel Construction magazine. It also was included in the special advertising section of the September 21, 2015 issue of Engineering News Record magazine.
- 11/09/2015 update: Further to the foregoing information three more new unrestricted UL Designs are now available: E701, E702, and S812.
- 10/23/2015 update: In addition to the UL Designs listed in Table 1 in the above article three new unrestricted UL Designs are now available: D988, D799 and S751.
Proper Application of Steel Beam Load Restriction Factors to UL Designs
This article appeared in the February 2016 issue of AISC's Modern Steel Construction magazine. It contains significant additional information that updates the October 2015 article and related information, and has been published jointly by Underwriters Laboratories, the American Iron and Steel Institute, and the American Institute of Steel Construction.
Fire-Rated Design Bulletin
The Underwriters Laboratories (UL) bulletin distributed to its members, was jointly drafted by UL, the American Iron and Steel Institute (AISI) and AISC. It Is meant to inform the industry of updates to UL fire-rated designs that specify a "Restricted Load Condition."
This article appeared in the January 2017 issue of AISC's Modern Steel Construction magazine. It covers new revisions to UL Design No. D982, extending it to be useful for two-hour restrained and two-hour unrestrained assemblies, composite and non-composite designs, normal-weight concrete and lightweight concrete, any welded wire fabric placement location in the concrete slab, and metal deck thicknesses from 1 1/2 in to 3 in., inclusive.
This article appeared in the June 2017 issue of AISC's Modern Steel Construction magazine. It provides five clear, simple and technically sound bases by which you can properly classify structural steel floor and roof construction as restrained or unrestrained for fire-protection design. If you are the responsible design professional, it provides the basis you need to satisfy the requirement that IBC Section 703.2.3 places upon you as you specify a restrained classification on the design drawings. If you are the building official, it also provides a basis upon which you can accept a restrained classification. It makes it clear that a restrained classification is almost always the correct classification and that the exceptions that require an unrestrained classification also are well defined.
Additionally, the following reference is specifically noted in the foregoing article: "Restrained Fire Resistance Ratings in Structural Steel Buildings," from the Second Quarter 2001 issue of the AISC Engineering Journal. It is available here.
As before, AISC, AISI and UL continue to work on solutions beyond what is included in the aforementioned articles. As those become available, they will be made known in AISC's Modern Steel Construction magazine and also posted here.