Engineering duo publishes a report on cold-formed steel and how it can be used to make buildings more resistant to the external blast from a terrorist attack.
By Richard Massey
The Cold-Formed Steel Engineers Institute recently released a technical note that should make it easier to design and build structures with exterior blast protection against terrorist attacks, and the information is good for both the public and private sectors.
The technical note, Antiterrorism Design Requirements for Cold-Formed Steel Framing, was co-authored by Nabil Rahman of the Steel Network Inc., and Casey O’Laughlin of Jacobs Technology, and comes at a time when terrorism is increasingly seen as a fact of life, not a fleeting aberration.
Eighteen months in the making, the technical note also comes as engineers, contractors, and developers are searching for ways to make structures more durable in an uncertain age. Evan as he developed the technical paper, Rahman conducted multiple seminars on cold-formed steel and blast protection.
“This technical note guides engineers on where they need to go,” Rahman says. “I wanted to share this information and not keep it for myself.”
The report focuses on external blast, standoff distances, controlled perimeters, windows, static and dynamic design, stud framing, Unified Facilities Criteria 4-010-01, and basic equations that determine building specifications.
In the introduction, Rahman and O’Laughlin spell out why they wrote the report.
“Understanding and implementing antiterrorism requirements into cold-formed steel framing design can be a daunting task for a designer,” they write. “The building can be subject to different AT requirements depending on whether it is owned by the Federal Government or by the private sector. In recent years, the DoD Unified Facilities Criteria program has developed documents to help walk a designer through the process; however, a considerable confusion still exists.”
Pat Ford, technical director at the Steel Framing Industry Association and principal at Matsen Ford Design Associates in Wisconsin, says blast standards for cold-formed steel are still relatively knew, as are antiterrorism design and construction guidelines in general.
That being the case, a technical note like the one created by Rahman and O’Laughlin is important because, as Ford says, “Not many people [builders and designers] know how to do it.”
While there’s currently not much of a demand for blast-
resistant construction in the private sector, that could change.
“There’s nowhere to go but up,” Ford says.
Made by rolling or pressing steel into semi-finished or finished goods at relatively low temperatures, cold-formed steel is affordable, easy to use, and can be erected much quicker than masonry or concrete. The material is straighter than wood, and is resistant to termites and fire. While there are many applications for cold-formed steel, its primary use is in construction for curtain walls and partitions. According to Rahman, it can be used as the primary structural system for buildings as tall as seven or eight stories.
Pulling together expert information from a dozen sources, the technical note is touted as an authoritative resource on cold-formed steel and its application to blast protection of building envelopes, specifically exterior walls. Peer reviewers were Farid Alfawakhiri of the American Iron and Steel Institute, Kelvin Chan of the U.S. Army Corps of Engineers, and Ady Aviram of Simpson Gumpertz & Heger (Hot Firm #82 for 2016).
Aviram, a Ph.D. in structural engineering, says blast regulations are mandated for U.S. military structures. But the information highlighted in the technical note, she says, is also meant for private sector use. In particular, those who are interested in low-level protection, not battlefield-grade bunkers, should find the report illuminating.
“It provides the basic steps on how to approach the problem,” says Aviram. “This is a good place to start [for the private sector].”
The information in the technical note is vetted by experts, consolidated in one place, and is easy to purchase and digest. Though the technical note might intimidate those who are not in the industry, for those who are, the formulas are easy.
“If you were a structural engineer, you would say, ‘Oh, I can do this,’” Aviram says.
She referenced the Boston Marathon bombing of April 2013, when two pressure cooker devices exploded, killing three and injuring more than 260. Detonated on a city street, far from a military installation, the Boston bombs highlighted the fact that a terrorist attack can take place anywhere and at anytime, and that blast standards can have great currency in the civilian world.
“You don’t need much to come up with a design to save people,” Aviram says.