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Originally published in Interiors & Sources

01/19/2007

The Scoop on Structural Steel

Need-to-know information on structural steel helps debunk industry myths

 

What’s New in Seismic Design

Steel has long been the gold standard for seismic design. The Washington, D.C.-based Federal Emergency Management Agency’s $12 million investment in the SAC Steel Project yielded an array of high-performance steel moment frame solutions. The American Institute of Steel Construction has incorporated this work into the 2005 Seismic Provisions and 2005 Prequalified Moment Connections Standard. In addition, the Seismic Provisions included two new solutions for designers in high-seismic areas:

1. Steel Plate Shear Walls. A superior solution for shear wall systems, this steel design offers substantial advantages in terms of cost, performance, and ease of design.

2. Buckling Restrained Braced Frames. While braces are usually stronger in tension and weaker in compression, this economical new system is much more robust and designed to eliminate buckling in compression.

For more information, visit (www.aisc.org).

A little more than half of all buildings built in the United States last year utilized a structural-steel frame. But, despite an almost 2:1 advantage over the next most-common framing material, building owners still have a lot of questions.

1. Is the price of steel skyrocketing?
No. Fortunately, the major price increases are now behind us, though minor fluctuations up and down are expected to continue. However, severe price inflation during the past 3 years affected almost every major building material - from concrete to plywood to gypsum products. Additionally, remember that you’re not buying steel beams; rather, you’re buying steel fabricated and erected. Typically, the raw material is only about one-third or less of the total steel package. As a result, the price of steel to a building developer still climbed substantially in the past 3 years - by a more reasonable 13 to 15 percent rather than the 40 percent widely reported.

2. Is there a steel shortage?
No. While inflationary prices are often the result of supply issues, this was not the case with structural steel. Instead, the run-up in prices was primarily the result of higher raw material costs plus rapidly climbing energy charges. While lead times from mills for wide-flange shapes are around 12 to 14 weeks (and, for structural tube [HSS], about 4 to 6 weeks), steel warehouses (also known as steel service centers) around the country have nearly 1 million tons of structural steel in stock and can deliver most sizes within days of receiving an order. Today, nearly 70 percent of the steel used in building projects is purchased from these warehouses. The exception is typically the “mega-project,” but these large-scale projects are always years in the planning.

3. Is steel a “green” material?
Yes. By weight, steel is the most recycled material in the world. In fact, if you purchase a wide-flange beam or column in the United States today, you’re getting a product produced from about 95-percent scrap material. In addition, because of the high value of steel scrap, old steel almost never ends up in a landfill; instead, it’s recycled into new steel products. If you’re considering LEED certification, a steel-framed building almost always receives a credit for recycled content. With most fabricators located within 500 miles of a jobsite, steel-framed buildings are typically eligible to receive an additional LEED credit.

4. Is steel a blast-resistant material?
Yes. Since 9/11, owners have been increasingly concerned about building safety. While a properly designed building using either steel or concrete is safe, structural steel’s inherent ductility and strength make it the preferred blast-resistant structural material. In fact, a recent full-scale test modeled the response of a steel column to the same blast that caused the collapse of the Murrah Building in Oklahoma City. It demonstrated that a comparable steel column subjected to the blast would not fail and would retain enough structural integrity to support the building after the blast. Steel’s phenomenal ductility makes it inherently blast resistant; it’s also the strongest building material.

Scott Melnick is vice president of communications at the American Institute of Steel Construction Inc. (www.aisc.org), Chicago.

 

 
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