STEEL FRAMING ALLIANCE | FRAMEWORK ONLINE
May 6, 2009
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Steel Framing: Where we’ve been and where we’re growing.

Jay H. Crandell, P.E.*
ARES Consulting

When you’re finished changing, you’re finished – Benjamin Franklin.
More famous as a statesman and inventor, Benjamin Franklin also offered great words of wisdom applicable to our lives and businesses today. Following Franklin’s advice in the quote above, one goal of the SFA is to continually find out what needs to be changed and then to change it for the benefit of the cold formed framing industry.

In 2006, the Steel Framing Alliance commissioned a comprehensive study to identify major building-code-related challenges affecting the competitiveness of cold formed steel framing. The study described its aim as follows:

“Because cold-formed steel and wood materials represent two major structural material competitors in the light-frame construction market, it is important to periodically assess the “state-of-the-art” of these materials as addressed in relevant building codes and standards…”

The Steel Framing Alliance retained ARES of West River Maryland for this study, under the direction of Jay Crandell, PE. Relevant building codes and standards were carefully scrutinized by ARES to identify strategic opportunities for improving the competitiveness of steel framing. As a result, 58 actionable items were identified and categorized according to five levels of strategic importance or value.

While the study and its findings were completed just over 2 years ago, SFA and allied organizations have responded to a number of these items in various ways. Below are some examples of the work initiated to address significant challenges and opportunities to make steel framing more competitive:

Alternatives to In-Line Framing: This item represents a long-felt need and primarily deals with alternatives to traditional, non-load bearing top tracks. Load-bearing top tracks permit point loads from floor joists or trusses to be supported without requiring alignment over studs. This issue has been address through the addition of commentary language in the AISI S230-07 standard, including reference to two research reports by the NAHB Research Center, Inc. and the University of New Brunswick. In addition, CFSEI is developing a tech note giving practical guidance on methods to design and construct load-bearing top tracks that provide a means to avoid the constraints of in-line framing.

Three-story Prescriptive Steel Framing: While steel studs can be easily engineered to support multi-story construction, prescriptive construction requirements for steel framing were limited to two story structures. Now, the scope of AISI’s S230-07 standard has been expanded to include three story structures, matching the limits of prescriptive wood framing provisions and leveling the competitive playing field.

Prescriptive Steel Framing for High Wind Regions: The AISI S230-07 standard now includes provisions to address design wind speeds up to 150 mph. This advancement allows prescriptive steel-frame construction to be used by builders, designers, and code officials in all wind conditions of the United States. Based on advocacy of AISI code staff, these provisions are also referenced in the International Code Council’s latest wind-resistant construction standard, ICC 600, recognized in the 2009 International Building Code and International Residential Code.

Tall Exterior Wall Studs: The AISI S230-07 standard for prescriptive steel framing was expanded to include gable end wall studs up to 22 feet in height. This addition matches similar provisions for wood framing and allows balloon framing of gable end walls for improved wind resistance or to accommodate cathedral ceilings commonly found in modern homes with great rooms.

Cost-Effective Energy Code Compliance: The 2009 IECC has been modified to allow exterior insulating sheathing to be used as the sole means of insulating cold-formed steel walls. In doing so, cavity insulation is completely traded-off for modestly increased R-value of exterior insulation. Thus, the added cost of a “dual” insulation approach can be avoided. This is a particularly appealing option in hot-humid climates in the southern United States.

Sheathing Braced Design: It is well known that light-frame walls resist loads as a system of components that, as a whole, perform better than the sum of the individual parts. To enable system-based design, however, requires a greater burden of justification than simple, element-based analyses. Thus, AISI and SSMA have co-funded a three year project at The Johns Hopkins University to provide a means to produce data justifying efficient, system-based design principles for cold-formed steel stud wall assemblies. Wood frame walls are currently designed using repetitive member factors that account for system effects. Expect more to come in the future to level the playing field for cold-formed steel wall assemblies.

Steel Diaphragms Supporting Masonry/Concrete Walls: Provisions have been added to AISI 213-07 to enable steel-framed floor and roof diaphragms to support out-of-plane loads from masonry and concrete walls due to earthquake forces. These provisions match similar requirements for wood-framed diaphragms.

Other competitive advancements for cold-formed steel framing have been achieved or are being pursued. While some have higher or lower priority than others, each serves to build-up the competitive position and capitalize on the benefits of cold-formed steel framing. Although the scope of this article does not permit a detailed accounting of all of the achievements to date or those expected to come in the future, rest assured that SFA will continue to support code changes, standards development and research on your behalf. Based on positive early achievements, it can be said that “steel framing is not just here to stay, but here to grow!”

*The author wishes to thank Jay Larson of the American Iron and Steel Institute and Mark Nowak of SFA for their help in tracking progress on the issues discussed in this article and for contributions to the text.

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May 7, 2009
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May 20-21, 2009
California Steel Framing Forum and 2009 CFSEI Annual Conference Anaheim, CA More

 
 

June 1, 2009
Cold-Formed Steel Shear Wall Assemblies
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