Building with steel

August 11, 2010

Building with Steel

(Continued from p. 74 of the May 2008 issue of BD+C)



Adoption and use of CIS/2 has matured quickly. BIM is taking off at a somewhat slower rate. The two tools, says RTKL’s Knight, “are enhancing the delivery process on select projects, but not on the majority. These tools will lead to more streamlined delivery processes, but their full benefit is still in the future for most projects.”



                  
Once you've read this special report, take the AIA Exam to earn 1 AIA HSW learning unit. (one-time registration required)

 


Reed Business Information is a Registered Provider with the American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request.
       This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. 

 

Different groups of building professionals are adopting the tools at varying rates, and with differing motivations. “At this point, most of the larger structural engineering practices have made the investment in the necessary software, hardware, and personnel training costs, but many are yet to produce their first project in BIM technology and are very much still on the learning curve,” Hamburger says. “My guess is that in two years, use of these technologies will be routine for the larger players, and most smaller players will be coming on board as well.”

Coffman Engineers’ Hussain also sees BIM becoming more effective as time goes on. “With the integration of the design, bidding, and construction management processes with the procurement process in BIM, it seems that proper coordination and delivery of steel would be smoother, much more automated, and better coordinated,” he says. However, “The issues related to authorship, ownership, and ultimate responsibility of the information content and processing of the BIM model remain somewhat murky and potentially thorny.”

Electronic data interchange. At the heart of such intellectual property concerns are the transfer and sharing of digital design data among project team members and the transfer of data to the owner. In general, advocates of electronic data interchange (EDI) are convinced that standardizing and using EDI will streamline existing work processes, “allowing owners to receive more value for their construction dollar,” says Mark Holland, P.E., chief engineer, Paxton & Vierling Steel Co., Omaha, and co-chair of AISC’s EDI review team. “The use of EDI is the next logical step in the evolution of the construction process. Implementation of CIS/2 and standardizing the electronic exchange of structural steel project information will pave the way in realizing a quantum leap in the construction process.”

Similarly, AISC EDI review team co-chair P. Bradford Vaughan, P.E., power operations manager at Black & Veatch, LLP, Overland Park, Kan., contends that adopting accepted protocols for electronic data exchange will provide horizontal integration—exchanges between software performing similar functions—as well as vertical integration, the delivery of results from one product as inputs for another. This means that data transfers are possible throughout the steel construction process, from engineering, bidding, and procurement to detailing, fabrication, transportation, and erection, “creating efficiencies that will help lower the installed cost of structural steel construction,” says Vaughan.

For example, for a 2003 addition to Baptist West Hospital in Knoxville, Tenn., CIS/2 EDI was used to transfer structural information from the engineer to the detailer, shaving the schedule. “Instead of the typical six- or seven-week time period that it might take for fabricators to submit shop drawings on a project of this magnitude, the detailer was able to send checked shop drawings for the first 500-ton sequence of the project only two-and-a-half weeks after being awarded the project,” says Joele Fowler, P.E., S.E., principal and structural engineer for Carpenter Wright Engineers, Knoxville.

STEELING FOR A SUSTAINABLE FUTURE
Another global trend that has played to the advantage of structural steel has been to drive for more environmentally friendly built works. Steel industry organizations have long billed their product as “the world’s most recycled material,” basing their claim on the fact that about 88% of all steel products in North America—and nearly 100% of structural steel beams and plates used in construction—are recycled into new products. In fact, AISC states that in 2006, close to 73 million tons of steel were recycled or exported for recycling in the U.S. The Canadian Sheet Steel Building Institute concurs, adding, “Once iron ore is extracted and refined into steel, its life never ends. This makes steel an ideal material to deploy in sustainable strategies for the construction industry.”

Looking at the criteria for rating green buildings and the properties of steel as a material, other project life cycle benefits become obvious. Building Teams can minimize job-site waste by manufacturing structural members to exact specifications for erection. During demolition, the material’s magnetic properties facilitate its separation from other materials for easier materials segregation and recycling.

“Because steel systems are fabricated in the shop and not in the field, there is virtually no waste,” says AISC’s Erika Winters Downey, an advisor to the AISC’s Steel Solutions Center. “Any small amount of scrap that is produced on the site will be recycled. In addition, most steel systems do not use shoring—a major source of waste in concrete projects.” 

Another common sustainable strategy is the use of mechanical connections to allow for easier disassembly and reuse. “Mechanical connections, principally bolted connections, have always been popular in steel construction,” says Hamburger. “They not only disassemble quickly and easily, they also assemble quickly and easily, reducing construction cost.” Hamburger acknowledges, however, that unless you are planning to build the same structure in another location, the ability to unbolt and rebolt may not prove to be a real advantage. “In most cases, you will have to change the length of the various pieces and make new attachments to them before using steel in a new building,” he says.

Even so, says architect Michael McLane, “Steel by its very nature can be recycled relatively easily by melting it to make new steel members or other essential building commodities.”

EXPOSING BEAUTY WITH AESS
Another trend pushing the use of steel today is the use of architecturally exposed structural steel, also called AESS. This recent design trend has been driven by such splashy facilities as Helmut Jahn’s United Airlines concourse at Chicago’s O’Hare International Airport, McCarran International Airport’s Terminal D gate concourse in Las Vegas by Tate Snyder Kimsey Architects, and the Seattle Public Library by OMA and LMN Architects. “Exposed architectural steel continues to be popular for many building types and appears to be increasing in popularity,” says RTKL’s Knight.

One reason for this trend toward greater use of architecturally exposed structural steel is an improved understanding of steel’s performance in fires. “Architecturally exposed steel will continue to remain popular, particularly as performance-based approaches to fire safety engineering gain prominence and acceptance, permitting engineers to demonstrate that exposed structural steel can be safe as well as functional,” says Hamburger.

Another factor in favor of AESS is the ability to fabricate unusual shapes for visual interest, as seen in projects like Disney Concert Hall in Los Angeles, designed by Gehry Partners. However, Hamburger points out that AESS fabrication comes at a cost premium, and cutting intricate shapes is even more costly.

Industry professionals also point out that existing codes and standards lack guidance for the design, detailing, fabrication, and construction of AESS. Furthermore, the division of responsibility for AESS’s design and construction among the architect, engineer, and contractor can further complicate the project and add to the potential for conflict. In response, the Steel Liaison Committee of the Structural Engineers Association (SEA) of Colorado and the Rocky Mountain Steel Construction Association recently teamed up to develop AESS specification guidelines to ease the process. The guidelines consist of a sample board, cost matrix, specifications, and library of photos to assist the AESS design team.

FIRE PROTECTION CONSIDERATIONS
One well-appreciated benefit of steel is that it performs well in fires. Yet there are popular misconceptions about what this means. Steel is considered fire resistant because most building fires are not hot enough to melt or ignite steel. However, like any metal, steel is a very efficient conductor of heat. Consequently, protecting steel with paints, coatings, or other methods is common.

“Despite its strength and permanence, fire can be the Achilles heel of steel if it is not adequately fireproofed with conventional sprayed-on fireproofing or more expensive intumescent coatings,” says Taylor’s McLane. “Intumescent coatings” refers to the class of coatings that expand or swell when exposed to sufficient heat, instantly creating a more robust fire barrier. Fireproofing is not particularly difficult to specify and apply, he adds, “but it does require good communication and coordination on the contractor’s part. Knowing the right time to fireproof so that there is no interruption into construction activity flow is critical.”

Structural engineers must also be concerned that designs account for the possible loss of stability due to fire and heat. “Like all construction materials, including concrete, when structural steel heats, it loses strength and stiffness—two critically important properties for structural safety,” says Hamburger. “As a result, it is usually necessary to protect steel from direct impingement of heat.” Common protective measures include spray-applied fire-resistive materials (SFRM), intumescent coatings, gypsum-board enclosure, and the classic hybrid using concrete encasement or filling, or both.

Sprinklers, foggers, and water sprays are also crucial in all commercial and institutional buildings, Hamburger notes. Other safety measures include limiting the amount of combustible materials present in a structure and providing sufficient space and ventilation to limit the heat effects.

Fire protection engineers Nestor R. Iwankiw and Richard G. Gewain, with Baltimore-based Hughes Associates, note that sprayed fire-resistive materials (SFRM) include intumescent coatings, which, when exposed to a fire, will char, foam, and expand significantly in thickness, creating a protective layer around the steel. “Most SFRMs either utilize mineral fiber or cementitious materials to insulate steel from the heat of a fire,” say Iwankiw and Gewain. “Mineral fiber and vermiculite acoustical plaster on metal lath are two of the frequently used SFRMs for use on steel columns, beams, and joists.”

Iwankiw and Gewain remind building professionals that, in choosing the best strategy for protecting steel, the suitability of a fire-protection product for any specific application depends on several factors, including:
• Required fire-resistance rating
• Expected service conditions
   * Exposure to weathering effects
   * Vibration
   * Accidental impact
   * Other significant occupancy factors
• Compatibility with corrosion protection requirements (if any)
• Aesthetics
• Economic considerations

Testing standards. According to Iwankiw and Gewain, testing standards offer the most useful and credible performance criteria to determine a material’s actual level of fire resistance. The most common standard for steel building components is ASTM E119, which tests the performance of various steel components when exposed to fire and assigns a fire-resistance rating of from 1 hour to 4 hours, based upon observed and measured performance. 

Beyond ASTM, Hussain has seen lots of industry development in the realm of fireproofing standards, requirements, and products. “Spurred strongly by the 9/11 experience, fireproofing of steel continues to improve and advance in terms of better codes, improved specifications and fireproofing products and most important of all, greatly improved quality assurance, quality control, maintenance requirements, and practices,” he says.

MANAGING COST VOLATILITY
Building Teams need to keep in mind the upward trend in the cost of construction materials, in particular, steel, which has been experiencing volatility in the last few years.

The turbulence in the price of steel has not been due entirely to domestic demand. In the December 2007 issue of Purchasing magazine, editor Tom Stundza noted that steel use actually declined 3% in 2007: “In all likelihood,” he wrote, “the steel economy is going to encounter another six to nine months of tough sledding, with metalworking and metal-producing companies experiencing further profit disappointments, consumers cutting back on end-product purchases, industrial job growth weakening, and possible slowdowns in capital spending.” Charles Bradford, an analyst at Bradford Research, New York, echoed this sentiment, stating that while “world steel usage has been quite strong all year, that is not the case in the U.S., where major markets for steel have been flat to down—and lately largely weak.”

In the steel construction market, however, AISC’s Cross reports that “structural steel experienced a rapid run-up of prices in early 2004, relative stability—including a dip in the summer of 2005—through the end of 2006, only to see another increase in early 2007, followed by a plateau and then another increase in early 2008.”

In terms of understanding where volatility is coming from, Cross explains, “burgeoning demand in China for construction materials, a weakened U.S. dollar, growing global production, escalating shipping costs, future growth expectations in India, increased competition for raw materials, and a domestic policy favoring free trade have created the context for continuing volatility in all types of construction materials.”

Consequently, it is essential for Building Team members to employ certain strategies in order to minimize the effects of rising construction material prices on their projects. AISC’s Cross provides the following suggestions:
• Bring the steel fabricator in early to convey current market information and identify cost-saving approaches to project design and construction.
• When comparing costs for alternate structural systems, be sure to base estimates on current costs, not prior data.
• Produce clear bid documents specifying which party is to assume the risk of a change in material prices.
• Rapidly process bids and issue a notice to proceed to the selected fabricator to lock in prices.
• Encourage your fabricator to purchase mill material early by reimbursing the fabricator for the cost of material and storage at the time of purchase.

Cross further emphasizes the importance of project team communication, continuing to search for improved design and construction practices, and not “irrationally reacting to press reports regarding the cost and availability of steel and assuming that structural steel is exhibiting the same marketplace characteristics as other steel products.”

STEEL YOUR NERVES
Despite its price volatility, steel has remained competitive, and its numerous design and construction benefits still rank it as a premier building material.

AISC’s Cross argues that the performance of structural steel is reliable and predictable: “It’s produced to precise tolerances in size and strength and this makes steel easier to design and use. Also, because it’s at full strength as soon as it’s erected, project schedules are predictably shorter.” 

According to RTKL’s Knight, “Steel’s advantages include lighter-weight construction and corresponding savings in columns and foundations and flexibility for making changes, both during design and construction as well as in the future.”

It’s precisely this ease of construction, high recyclability, and flexibility that will make structural steel construction a serious consideration for any Building Team’s projects.

About the authors

C.C. Sullivan is a communications consultant and author specializing in architecture and construction. Barbara Horwitz-Bennett is a writer and contributor to construction industry publications.



















































































Take the AIA Exam  (one-time registration required)

This BD+C continuing education program qualifies for 1 AIA HSW learning unit.

Reed Business Information is a Registered Provider with the American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request.
       This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.


         
 

Comments on: "Building with steel "