Trends in Steel
BRBF systems becoming more popular in seismic areas
Steel prices have leveled since second quarter of ’07; Two of three manufacturers of buckling-restrained brace frames – CoreBrace and Star Seismic – are headquartered in Utah.
(BRB’s) can withstand a moderate- to high-level seismic event and the building would still be safe. A building can go through a high-level earthquake and still have reserve capacity.” – Dorian Adams, Reaveley Engineers + Associates.
Despite a nearly $100 bump per ton in the cost of mill steel prices at the beginning of the second quarter of 2007, steel remains in high demand throughout the Intermountain region as the construction industry remains as busy as it’s ever been in Utah and Idaho.
According to John Cross, vice president of marketing for the American Institute of Steel in Construction (AISC), both scrap prices and mill prices for steel have leveled after prices rose from $660 per ton to $755 per ton from January to April. Cross says that the price increase equates to a 3-4% bump in an overall steel package for a project.
“The price has been pretty stable since scrap prices have leveled, and mill prices have stayed stable,” says Cross, adding that availability hasn’t been a factor in most parts of the country. He anticipates prices to stay where they’re at through 2008, providing demand from foreign countries doesn’t spike in the next six months.
Locally, availability has pinched some projects, and forced steel fabricators and erectors to order steel far enough in advance to ensure timely delivery.
“It’s been an item you’ve had to attend to pretty closely,” says Morgan Humphries, vice president of Business Development for Adams and Smith, a steel fabricator and erector in Orem, Utah. “It’s a fairly tight steel market for availability. You have to plan early and stay involved and schedule ahead. It has hurt projects that architects or owners think they want done in three months.”
Another concern for steel companies is one affecting all construction trades – a lack of skilled, qualified and motivated laborers.
“Everybody is really busy and business is good,” adds Doug Lott, project manager for Mountain States Steel in Provo and current president of the Utah Steel Fabricators Association (USFA). “The flip side is everybody is facing employment problems. Nobody can find enough quality people. We’re working to establish a recruiting effort and trying to set up an apprenticeship program. That’s a big need.”
Lott said USFA recruiting efforts extends to minorities, who seem like a logical target for construction employers. “We need to reach out to more Hispanic and other minority cultures,” says Lott. “It’s one of the solutions to our long-term employment problems.”
“Labor is at a premium,” adds Humphries. “We travel to do a lot of work and we tend to take our full-time people with us and depend on their abilities because we’re familiar with them. Labor is a challenge for everybody.”
Buckling-Restrained Brace Frames
Since its market debut nearly two decades ago in Japan, buckling-restrained brace (BRB) frame systems have become a hot topic among structural engineers and steel fabricators and erectors, particularly those who design projects in seismically-active areas.
Interestingly, there are only three manufacturers world-wide who produce BRBF systems and two are located in Utah – CoreBrace of West Jordan, and Star Seismic of Park City.
Originally created and utilized by Japanese steel titan Nippon Steel on projects in and around the Pacific Rim in the late 1980’s and throughout the 90’s, BRB’s have gained in popularity, primarily because of their excellent seismic performance during rigorous testing and overall cost-effectiveness.
BRB’s are essentially a brace frame that encases a core of high performance steel within a concrete matrix that is confined by a steel tube. Compared to traditional concentric braces, BRB’s exhibit nearly identical properties in tension and compression and have a substantial ability to undergo numerous cycles of inelastic deformations without degradation or fracture. BRBF systems are currently used as primary lateral force resisting elements both in new construction and seismic retrofit projects. The sturdy nature of these systems resulting from the elimination of the buckling mode of the BRB makes these braced frames good candidates for a variety of applications in high seismic regions.
According to testing done by structural engineering experts at places like the University of California-Davis, the University of California-San Diego and the University of Utah, BRBF systems perform so well and predictably in earthquakes that buildings incorporating the BRB system can actually be designed with much smaller columns, beams, and foundations in the braced bays. Unlike the massive gusset plates which are required on the special concentric braced frame (SCBF) projects, the connections for the BRBF system are a fraction of the size, use lighter material, and significantly less welding/bolting.
The first BRBF system was installed in the United States at UC-Davis in January 2000, which was about the same time a group of Utah-based steel executives from SME Industries of West Jordan began looking at BRB’s more closely.
Rival Companies Born
In early 2001, SME Industries, led by James Smelser and others, began the process of developing its own buckling-restrained braces and then set out to conduct rigorous tests at universities in Utah and California. By October of 2001, the first series of half-scale BRB specimens were successfully tested per AISC/SEAOC recommended provisions. In 2002, two more series of BRB specimens were tested at the University of Utah for brace sizes ranging from 65 to 340 kips and by July of that year, CoreBrace, LLC was established as a division of SME Industries.
“We did some exploratory work, to see if we could come up with a better idea for a buckling-restrained brace,” says Smelser. “After we did some preliminary tests at the University of Utah, the tests turned out well, so we made up our mind that we could do it. We ended up doing 40 full-scale tests, and for years all we saw was money going out of here. It’s extremely rewarding when you see things turn around and get some of the investment back. Buckling-restrained brace is probably the most tested structural system out there.”
Prior to CoreBrace’s establishment in July 2002, SME employees Argan Johnson and Steve Powell, who were part of SME’s initial BRB test team in 2001-02, decided to break away and start their own firm utilizing similar technology. Star Seismic was established in May of 2002 in Park City.
“We felt we had a better idea and elected to start our own company,” says Johnson of the decision to break away from SME’s CoreBrace. “The brace performs similarly to established codes – some parts are quite a bit different internally and externally.”
CoreBrace currently has two patents and three other patents pending, while Star Seismic has three patents to date. Nippon’s BRB is called Unbonded Brace.
According to Andy Hinchman, a structural engineer for CoreBrace, the CoreBrace BRB is essentially a steel core that runs through a hollow structural section casing. Between the two, the void is filled with a special concrete grout mixture. A special proprietary interface material separates the grout from the casing, causing it to act independently. The steel core takes all the force and demand of a building during a seismic event. The casing and grout guides the steel core to keep it from buckling.
“CoreBrace has enough durability to sustain four major earthquakes (7.2 magnitude),” says Hinchman. “We’ve done many full-scale frame tests and hundreds of individual tests and they all indicate that the performance will be there.”
Kim Robinson, a structural engineer with Star Seismic, said her firm’s BRB’s function similarly, and have been put through vigorous cost tests to compare possible economic savings versus other traditional steel systems.
Robison says a recent independent cost study done by Dasse Design of San Francisco – which was presented at the 2006 North American Steel Construction Conference – changing from a SCBF system to Star Seismic’s PowerCat Brace system, saved $2.40 per sq. ft. for a model six-story structure. Savings were less dramatic for a three-story structure, but were still considerable.
She adds that Star Seismic has done more than 40 projects to date in six states, with the largest capacity brace manufactured being more than 1,850 kips.
BRB Market Growing
The seismic upgrade of the Wallace F. Bennett Building five years ago, designed by Reaveley Engineers + Associates of Salt Lake City, was the first project in Utah to utilize a BRBF system. Since then, several other significant projects have utilized BRB’s, including the massive Intermountain Medical Center (IMC) in Murray, the Marriott Library Renovation at the University of Utah, and the Utah Valley Medical Center expansion in Provo.
According to Dorian Adams, an associate with Reaveley and project manager on IMC, BRB’s are becoming more respected by the structural engineering community.
“From the beginning we were pushing to go with BRBF on the IMC project,” says Adams. “The concept behind buckling-restrained brace systems is that they are able to withstand high levels of seismic demands with a high level of reliability, based on testing that has been done. There has been a lot of testing done on these systems.”
Adams said all three manufacturers were invited to submit an open bid for the IMC steel package, and that CoreBrace’s BRBF system was selected as part of the complete package offered by SME Steel. Adams said BRBF tests indicate that a building such as IMC could withstand a 7.2 magnitude quake while maintaining its structural integrity.
“One aspect is (BRB’s) can withstand a moderate- to high-level seismic event and the building would still be safe,” says Adams. “A building can go through a high-level earthquake and still have reserve capacity.”
He adds that all three BRB manufacturers seem to have a good product, and that it is indeed interesting that two of the manufacturers are based in Utah.
“For IMC, we had complete confidence in all three manufacturers,” says Adams. “The brace needs to meet specific project criteria – when we specify a project, we ask the supplier to make sure the brace can handle the demands of that project.”
Ralph Spencer, chief estimator for Okland Construction of Salt Lake City, adds that the cost of BRBF systems have dropped significantly the past three years. In 2003 when Okland was doing the initial budget for IMC, Spencer says the cost difference between BRB’s and eccentric brace frame was basically even. By the time the project bid nearly a year later, the cost of BRB’s had dropped well below that of other systems.
“CoreBrace got involved and we were able to drop the price. As time went on, the engineer went to the owner and said this is the only way to go,” says Spencer, who adds by his estimates the owner saved more than a half million dollars over the initial budget by using a BRBF system.
About six months ago Spencer did a budget analysis on the IMC Medical Office Building, a nine-story steel framed office building on the IMC campus. Spencer said BRBF was easily the most cost-effective system. All three BRB manufacturers bid the job, just like the other aspects of IMC, and again CoreBrace was utilized since SME Steel got the bid. Spencer says having three manufacturers instead of just one makes for a much more competitive marketplace.
“Once there was some competition it was amazing how Nippon’s prices dropped,” Spencer says. “All three (BRB manufacturers) are competitive. We’ve seen projects where all three have won (bids). It’s good for the market.”
Ron Dunn, president of Dunn Associates, Inc. of Salt Lake City, adds that today’s building codes favor a structural design utilizing BRB’s, and that they are a potentially economical way to brace a steel structure while maintaining a good level of ductility.
Dunn adds that there is some significance of having two of the three worldwide manufacturers of BRB’s located in the Beehive State. He says the significance is not intellectual, but rather fabricator driven and that the technology is rather simple.
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