ADVANCES IN STEEL CONSTRUCTION give large-scale … · ADVANCES IN STEEL CONSTRUCTION T ... loaded columns and chords for large trusses are common ... cast concrete and tilt-up concrete

www.BDCuniversity.com BUILDING DESIGN+CONSTRUCTION AUGUST 2015 47

high-performance materialsAIA CONTINUING EDUCATION

ADVANCES IN STEEL CONSTRUCTION

T he recent rekindling of structural expressionism—a modern-ist concept rooted deeply in Brutalism, Chicago architecture, and the high-tech architectural movement—has a lot to do

with the latest advances in steel systems. For at least 135 years, industrialized methods of building have made iron and steel much smarter and more adaptable. Now, a quantum leap in material formulations, production techniques, and delivery expertise are mak-ing steel far more sustainable and opening new doors for its use by Building Teams.

BY C.C. SULLIVAN, CONTRIBUTING EDITOR

After reading this article, you should be able to:+ EXPLAIN the difference between high-performance

(70 ksi) steel and other steel grades.+ DISCUSS steel systems that can be used in situations

where concrete systems may be used, such as in multifamily and commercial facilities.

+ LIST potential technical concerns associated with architecturally exposed structural steel (AESS) and possible solutions.

+ DESCRIBE the sustainability benefits of steel construction, notably recycled content and material recovery.

LEARNING OBJECTIVES

Florida Polytechnic University Innovation Science and Technology Build-ing, Lakeland, a national AISC award winner. Santiago Calatrava designed 84 arched pergolas to shade the terraces; 94 operable louvers atop the roof open and close like giant wings. E&H Steel Corp. was the fabricator.

give large-scale projects a big lift

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48 AUGUST 2015 BUILDING DESIGN+CONSTRUCTION www.BDCnetwork.com

“There seems to be a new inter-est in expressed structure where the structural steel is part of the architectural image,” says Greg Otto, Principal with engineering consultant Walter P Moore (www.walterpmoore.com). “With this comes a demand for tighter integration of the primary and secondary structure and the building enclosure.”

With new demands come new benefits—the ability to take advantage of interchangeable prefabricated parts, greater project flexibility, and economy

of construction. Structural steel components can sway the project planning phase. In these instances, exposed structural elements and innovative methods to achieving stability often take center stage. Structural engineers and steel detailers and fabricators share much of the limelight with visionary owners and architects.

Steel is also “a very sustainable material, with high recycled content and a high recovery rate of about 98%, helping give it environmentally a very low carbon footprint on a use basis,” says John Cross, Vice President, American Institute of Steel Construction (www.aisc.org). “Steel lends itself to reuse. In the industrial sector and as shoring and scaffolding, owners are putting up and reusing steel structures, saving even more material.”

AISC’s Cross cites composite construction frames with composite shallow floors and columns (such as by Peikko), girder-slab systems of structural steel and flat plate concrete (including GirderSlab), high-performance steel frame connection technologies (e.g., SidePlate), and chassis-based modular steel building systems (by ConXtech and others).

One unanticipated development in steel is the adoption of recent bridge construction technology for use in large-scale building

projects where increased strength, reduced weight, and fabrication improvements—often with attendant cost reductions—are desired.

The product is commonly called high-strength or high-perfor-mance steel (HPS), but those in the know call it 70 ksi steel, in reference to its yield strength measured in thousands of pounds per square inch (ksi)—roughly 485 megapascals (MPa). The first use of HPS for a building in the U.S. was Chicago’s 150 North Riverside office building, currently under construction.

Designed by architect Goettsch Partners (www.gpchicago.com) and structural engineer Magnusson Klemencic Associates (www.mka.com) for developer O’Donnell Investments, the 1.2 million-sf building has unique core-supported structural elements with a sharply tapered base. It will rise 54 stories on a former railway ease-ment. ArcelorMittal is the steel producer.

MKA Managing Principal Dave Eckman, SE, PE, AIA, says the columns on the 150 North Riverside tower are just a start. “We are proposing it on more projects,” he says. “Grade 70 steel is most ap-propriately used to resist large loads in tension/compression. Heavily loaded columns and chords for large trusses are common applica-tions of the high-strength steel.”

W. Steven Hofmeister, SE, PE, LEED AP, Managing Principal at Thornton Tomasetti (www.thorntontomasetti.com), says, “We an-ticipate utilizing this material in many of our long-span and high-rise projects,” depending on availability and cost.

So, 70 ksi steel has arrived. But why is this high-performance product being adopted for buildings?

HPS sections have been around since 1992, according to Del-bert F. Boring, PE, an engineer who documented the U.S. Navy’s 1994 partnership with the Federal Highway Administration and the American Iron and Steel Institute (AISI). The goal of the alliance was to develop new and improved steels for high-challenge applications, such as wide-spaced bridge piers and situations requiring a reduc-tion in girders for certain spans.

Word spread. “The excellent properties of HPS with higher strength, moderate ductility, higher fracture toughness, better weld-

Lightweight steel mem-bers—castellated purlin-to-beam connections used for architecturally exposed structural steel (inset)—help bring daylight into South Bend (Ind.) Airport’s expansion of Concourse A, designed by Donahue/Her-ceg & Associates (archi-tect) and CE Solutions (SE).

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RESEARCH INSTITUTE’S TOP 5 TRENDS IN STEEL BUILDING DESIGN

1. The use of exposed structures and steel castings2. The substitution of steel for precast and tilt-up con-

crete elements in certain projects (e.g., multifamily)3. The recent adoption of high-strength steel in a small

but growing number of cutting-edge buildings4. Further advances in steel coatings, weathering finishes,

and fire-protection methods5. Improvements in project delivery, thanks to greater

integration between fabricators and detailersSource: American Institute of Steel Construction


ability, and efficient machinability can improve structural performance significantly,” according to Yongjiu Shi, a professor at Tsinghua Uni-versity, Beijing. He notes that the city’s 2008 National Stadium (the so-called “Bird’s Nest”) and the 44-story CCTV Headquarters are both early examples of the use of HPS. Yongjiu says that the “fabri-cation and construction efficiency of steel buildings can be improved remarkably” using a newer grade of structural steel ideal for tall and large-span buildings.

A913 GRADE 70: THE NEW STANDARD FOR U.S. STEEL BUILDING PROJECTSFor U.S. building projects, the standard and grade to use is A913 grade 70, based on ASTM International specification A913, Stan-dard Specification for High-Strength Low-Alloy Steel Shapes of Structural Quality, Produced by Quenching and Self-Tempering Pro-cess (QST). In the spec, a V-notch test must be performed in order to evaluate the steel’s conformance to required tensile properties. According to ArcelorMittal, the shapes meeting A913 are intended for riveted, bolted, or welded construction of buildings, bridges, and other structures.

Codes have allowed the use of ASTM A913 steel for some time now. The International Building Code (IBC) referenced the standard AISC 360-10 Specification for Structural Steel Buildings, for which it gained approval in 1999 when AISC published the Load and Resistance Factor Design Specification for Structural Steel Buildings (better known as LRFD). The AISC’s published seismic provisions call out grades 50 and 65, but HPS grade 70 “can be used at the

engineer’s discretion,” according to ArcelorMittal.Due to its high yield strength, three or four girders of 70 ksi steel

can secure a span that would require five girders of conventional 50 ksi (345 MPa) steel. Columns and piers can also be spaced farther apart, opening up more floor area.

HPS materials are being used for gravity columns in high-rise ap-plications where there are no overriding drift or vibration concerns. This has resulted in typical weight reductions of 10–25%, accord-ing to ArcelorMittal. One World Trade Center in New York and the Shanghai World Financial Center used A913 Grade 65 for gravity columns. In tension members such as the bottom chord of a long-span truss or in compression members with short buckling lengths, A913 Grades 65 or 70 can provide weight reductions of up to 25% as compared to Grade 50 steel.

“The obvious opportunities for high strength are in structures where weight is critical,” says Walter P Moore’s Otto, who has not used HPS thus far. “Care must be given to second-order effects, namely buckling.”

Conventional grades of steel are being used by Building Teams for their resilience, adaptability, and strength. Hollow steel sections (HSS) are one such use. “On the industrial projects we’re involved with, we are seeing structural steel used as a replacement for pre-cast concrete and tilt-up concrete bearing walls,” says JD Taylor, PE, an Associate with CE Solutions Structural Engineers (www.cesolu-tionsinc.com). “This is typically achieved through the use of wide-flange or HSS columns and horizontal channel girts.”

The technique calls to mind the steel-concrete-steel sandwich

ARTIC, the 67,880-sf, LEED Platinum Anaheim (Calif.) Regional Transportation Intermodal Center. Building Team: HOK (primary designer), Parsons Brinckerhoff (prime design consultant), Thornton Tomasetti (SE), Buro Happold (MEP), STV Group (CM), and Clark Construction Group (GC).

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construction that emerged about a decade ago to offer structural efficiency and robustness. The composites employed shear connec-tors extending from plate to plate to create semi-rigid panels. The system offered a precise alternative to reinforced concrete that could accelerate construction and increase project efficiency.

Steel deck flooring and off-site assembly construction have led to

more use of steel in building types that might otherwise use cast-in-place con-crete. Prefabricated components and assemblies offer advantages for urban residential, college residence halls, and hotels, where sound control is also criti-cal. “Some of these projects have used girder-slab systems, which allow about the same floor-to-floor heights as con-crete structures, including hollow-core slabs and planks,” says AISC’s Cross.

With reduced laydown space in constrained project sites, the delivery of complete assemblies can reduce storage needs while also accelerat-ing project schedules and maintaining shop-level quality control.

Steel structure column grids often are easier to work with for mixed-use buildings, where residential floors sit above commercial and parking uses, according to the U.K.-based Steel Construction Institute (www.steel-sci.org). Modular steel construction can also confer economy of scale. “Steel is

also a lightweight construction system which minimizes loads on the foundations, and therefore saves on substructure costs, which can be important on brownfield or infill sites or for building extensions,” says SCI.

In some cases, design teams are using metal systems that work well with steel structures, such as infill walls, floor decking, light-weight roofing, and modular pre-engineered assemblies. CE Solu-tions’ Taylor says his firm has been specifying insulated metal panels in such structures because IMPs provide a durable surface, meet current energy codes, and are “very economical.”

CASTING A WIDE NET — WITH CAST STEELBuilding Teams are beginning to see the advantages of cast steel for certain applications, says MKA’s Eckman. “We see a lot of steel castings in Europe but not nearly as many in the United States, and steel castings can be extremely beneficial for intersections and joints with complex geometries or when a heightened aesthetic is desired,” he says.

More than a decade ago, Hans Schober, Dr-Ing, Senior Engineer/Partner with Germany’s Schlaich Bergermann und Partner (www.sbp.de/en), listed the benefits of cast steel in an influential article in AISC’s Modern Steel Construction. “With cast steel it is possible to create flowing forms without any sharp edges or leaps in the cross-section, thus avoiding stress concentrations and notch effects,” he wrote. “Steel castings possess technical advantages with regard to static and dynamic strength, accessibility of welded seams, simplic-ity of dimensioning, maintenance, and service life.”

UIC Forum, on the south campus of the University of Illinois at Chicago. Designers HOK (architect) and Thornton Tomasetti (SE) created a large open space by using several 36-foot-tall movable partitions, which are hung from two of four 124-foot-span trusses. The partitions allow the 23,700-sf event area to be divided into three 7,900-sf meeting spaces. A 99-foot-tall, four-foot-diameter exposed steel column supports the overhanging trellis-like roof.

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ADVANTAGES OF 65/70 KSI STEEL

While ASTM A913 Grade 50 steel is a common specification, using the improved grade 65 and the high-performance steel (HPS) grade 70 may offer significant advantages for identical load requirements, according to ArcelorMittal. The steel producer performed the follow-ing analysis to illuminate some of the potential benefits of the higher-yield-strength 65 ksi and 70 ksi steel materials:Trusses. When evaluated against Grade 50 material, A913 Grade 70 allowed for a reduction of four footweights: 27% weight savings, 27% cost savings, 41% savings in weld material.Cover-plated columns. For this use, Grade 50 steel requires a cover plate; A913 Grade 70 does not. This results in 23% weight savings and 46% fabrication cost savings.Columns. Compared to Grade 50 steel and based on same design load requirements, A913 Grade 70 allows for a reduction of four foot-weights: 26% weight savings, 26% cost savings.Source: ArcelorMittal


According to Eckman, “Steel castings are not brittle and have vir-tually the same material characteristics as other milled steel shapes.” To encourage structural engineers to give steel castings a chance, Eckman and others are working with the AISC and SFSA to develop a design guide that will illustrate the benefits of cast steel. “The hope is that, in addition to custom castings, ‘standard’ cast connec-tors will be available for circular and square HSS members and will replace expensive fish-mouth and clunky gusset plate connections,” says Eckman.

Much of the interest in cast steel can be attributed to aesthet-ics and new possibilities for structural expression. “The use of cast connections is very specialized, yet they look beautiful and perform well,” says AISC’s Cross. The applications of cast steel have helped elevate structural expression in novel ways, leading to such land-mark building projects as the I.M. Pei-designed courtyard roof of the Zeughaus in Berlin and the more recent cable-net-walled AOL Time Warner Building in New York.

HOW TO USE ARCHITECTURALLY EXPOSED STRUCTURAL STEEL MOST EFFECTIVELY Another trend in steel building design has been the use of architectur-ally exposed structural steel, or AESS. By definition, AESS is specified to be sufficient as a primary support for the building or its elements, such as a canopy or roof system. The steel is “exposed to view, and therefore a significant part of the architectural language of the build-ing,” according to an article by Terri Meyer Boake and Vincent Hui for the Canadian Institute of Steel Construction’s Steel Structures Educa-tion Foundation (www.ssef-ffca.ca). “The design, detailing, and finish requirements of AESS will typically exceed that of standard structural steel that is normally concealed by other finishes.”

The choice of AESS demands tighter integration of the primary and secondary structure and building enclosure, says Walter P Moore’s Otto. The project may have very exacting dimensional toler-ances, or unique fabrication details for exposed connections. Or it may require preparing and finishing the connections, such as spe-cialized welds, grinding, and filling to achieve smooth finish surfaces.

Experienced engineers suggest adding requirements for the grind-ing of welds, specific handling of AESS during erection, and removal of the manufacturer’s identification marks. These factors can impact costs. But the results can be impressive. “Europe has been going this way for some time, and it is good to see this momentum in the United States,” says Otto.

AESS can also be used in cast-steel connections, advises AISC’s Cross. “The challenge becomes a matching of expectations. Will the Building Team achieve a perfectly smooth, mirror finish? Probably not, but the structural steel can meet rigorous expectations that are well understood in advance.”

AESS has been used in such classic high-tech projects as the 1977 Sainsbury Center for Visual Arts, designed by Foster+Partners and structural engineer Anthony Hunt Associates, and in Helmut Jahn’s United Airlines terminal at O’Hare International Airport (1988).

Building Teams need to work closely with the steel suppliers and


elevated experience: CHICAGO’S NEW TRAIN STATION, IN STEEL

Steel construction is on display at the Chicago Transit Authority’s $50 million Cermak Elevated Green Line Station. The station, which opened last February, is part of $4 billion in transit investments designed to add much-needed access to rapid transit for the city’s Near South Side residents and businesses. It is a showplace for the use of exposed galvanized steel.

“Bolted field connections were needed to limit the amount of mask-ing, grinding, and touching up of the galvanized coating needed to field weld in areas with exposed steel, such as the cantilever canopy,” says Anna Dukes, PE, SE, Senior Associate/Senior Engineer with T.Y. Lin International, the structural engineer and consultant to station designer Ross Barney Architects. “It was a challenge to make as many of the connections as possible in the shop while still maintain-ing a piece that was small enough to hot-dip galvanize and ship to the project site.”

The project combines steel elements that are both painted and gal-vanized, says Dukes. The client and owner preferred galvanized steel to keep down future maintenance costs. But there were difficulties associated with utilizing bolted connections while still trying to maintain the architect’s design intent, says Dukes.

The solution: Make as many of the connections as possible in the shop while still maintaining a piece that was small enough to hot-dip galvanize and ship to the project site, says Dukes.

For a tube-shaped windbreak structure, field bolting would have disrupted the smooth arc appearance, says Dukes. This element was painted in order to utilize field-welded connections, which were ground smooth and painted over. “They all but disappear,” says Dukes. “A three-coat system was specified to obtain long-term corrosion protec-tion for the painted elements.”

Steel structural projects like this one can benefit from knowledge of likely suppliers. “Being aware of the fabricator’s and local supplier’s capabilities helped us to design and detail in a cost-effective manner,” says Dukes. Much of the steel was specified as galvanized, which added another process that had to be accounted for in the construction schedule. “Working closely with the general contractor and the fabrica-tor allowed proper planning of steel delivery to keep the erection work on schedule,” she says.

Early coordination and regular communication with the steel fabrica-tor and detailer were essential to keeping the project on an expedited schedule. Weekly meetings were held with the fabricator and the detailer to go over any questions and to review the progress of shop drawings, says Dukes. That allowed the team time to prioritize when problems had to be resolve or shop drawings had to be made in order to keep up with the fabricator’s production schedule.


fabricators, especially because existing codes and standards may not provide enough sufficient guidance on design, detailing, fabrica-tion, and construction of exposed steel structures. “The greatest challenge is specifying the AESS parameters in such a way that all interested parties have the same understanding of the end-product’s appearance,” including dimensional tolerances and the smoothness of finished surfaces, says Magnusson Klemencic’s Eckman.

Building Teams should require clear parameters in the project doc-umentation as well as mockups of the finished products. “Mockups should be viewed from a distance that represents the actual in-place viewing distance,” advises Eckman. Mockups can be extremely help-ful for review, dialogue, and eventual agreement on the acceptance of the finished product’s appearance, he says.

It is extremely important to understand the viewing distance, say seasoned project leaders. “Attention must be given to what is actually desired in terms of finish and appearance,” says Walter P Moore’s Otto. “This will vary and should be specified in ranges based upon whether the steel is to be touched, or what constitutes the viewing distance, or both.” Otto offers a basic description of the AESS specification requirements as:

n Within touchn Less than 15 feet awayn 15 to 30 feet awayn More than 30 feet awayEven with these graduated requirements, consider that a section

of coated, exposed steel that is 100 feet overhead does not need to meet the same criteria as an AESS column at eye level in a corridor. Common sense helps reduce costs and unnecessarily restrictive specifications. Some Building Teams also substitute their own specs for the AESS’s, says Otto; for example, by describing requirements more exacting than a typical steel specification but below the AESS specifications for steel beyond the 15- to 20-foot viewing parameter.

CE Solutions’ Taylor says it’s wise to set expectations early in or-

der to avoid unnecessary change orders. “AESS is often valued-engineered out of the project due to a failure to account for it in the initial cost estimate,” he says. “Care must also be taken when preparing specifications so that expectations can clearly be defined to the contractor and steel fabricator”—how smooth the welds need to be ground, surface preparation, coatings requirements, and the like.

Building Teams must plan AESS projects very carefully. The primary refer-ence is the AISC’s Code of Standard Practice for Structural Steel Buildings and Bridges. The Steel Liaison Committee of the Structural Engineers Association of Colorado and the Rocky Mountain Steel Construction Association has also published AESS specification guidelines

(see http://bit.ly/1IzhWog). “This white paper is a great help,” says Thornton Tomasetti’s Hofmeister. “The most important thing related to the successful contracting for AESS is to clearly define the goals and criteria for AESS in the project.”

The guidelines recommend the use of the following:Sample board – Create a display with small pieces of processed

structural steel, indicating the range of finish surfaces that can be expected from the fabricator. Samples are intended to help designers see how various fabrication techniques affect the final product.

Cost matrix – Provide an organized presentation of the cost pre-miums (which can vary from fabricator to fabricator) associated with specifying the desired techniques to achieve the final appearance of an AESS project.

Specifications – Use the guidelines to provide a consistent mech-anism to define appearance quality based on the pieces selected and shown on the sample board and budgeted in the cost matrix.

Project case studies – For more specific ideas about the finished product, show representative photos and information to all team members. These images should show how various fabrication tech-niques appear in finished structures and allow the designer to view AESS in different lighting conditions with varying connection details, finish coat appearances, and the like.

Depending on how the steel is prepared and finished, “there is sig-nificant cost difference, so the clients money should be spent wisely,” says Hofmeister. At less than 10 feet, where occupants can interact with the structure, “we have seen much more explicit and strict requirements than for the exposed steel that is at a greater distance from the occupants.”

QUALITY IMPROVEMENTS, COST REDUCTIONS BEING MADE IN SPECIALTY STEEL COATINGS According to AISC’s Cross, there has been a decrease in the use of untreated weathering steel, such as exposed Cor-Ten–type materi-

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The steel trellis canopy designed by Thornton Tomasetti (SE) at The Commonground entry pavilion, Eskanazi Hospital, Indianapolis. Also on the Building Team: Diller Scofidio + Renfro (architect), The Olin Studio and Land Collective (landscape architects), and Gibraltar Construction (GC).


als. The use of bare galvanized steel remains robust for steel-framed parking structures and industrial facilities.

There’s a whole new generation of coatings for steel. Many new, high-performance finishes apply and cure more rapidly than previous formulations, thereby extending the life of steel assemblies. Fast-drying primer formulations are widely available. Some new products are better at resisting the effects of coastal air, corrosive environ-ments, and the abrasion or wear that can affect some exposed steel members.

Intumescent coatings—the passive fire-protection materials employed to insulate steel structures from high temperatures and fire—are becoming more popular. Two basic approaches to steel fire protection are available: nonreactive products, such as boards and sprays; and reactive materials, such as thin-film intumescent coatings that are applied in the shop or at the job site. The products apply like paint but at temperatures of 200–250°C a chemical reac-tion occurs and the coatings swell and char, to present an expanded protective layer.

The cost of intumescent coatings is starting to come down, says

AISC’s Cross. However, multiple coats are required, and there are limitations on how thick those coats can be. “The manufacturers are working on thicker coats so that the steel can be finished in one or two coats rather than three to four coats,” he says. Intumescent products do well against low-density, spray-applied protections or troweled-on cementitious materials for exposed-steel applications. But if the steel is not exposed to view, there’s no reason to use the more expensive finishes, says Cross.

With innovative systems like high-performance steel, architec-turally exposed structural steel, composite construction frames, girder-slab systems, and chassis-based modular assemblies, steel is proving to be more robust than ever.


1. Steel may be considered a sustainable, low-carbon-footprint material because it can be reused and has high recycled con-tent and material recovery rates of about:

A. 58% C. 88% B. 78% D. 98%

2. The flowing forms of cast steel connections eliminate sharp edges and leaps in the cross-section, which:

A. Helps avoid stress concentrations and notch effects B. Reduces static and dynamic strength C. Makes it difficult to access welded seams D. Adds to maintenance demands

3. Grade 70 high-performance steel (HPS) is recommended for use to resist:

A. Large tension forces in columns only B. Large loads in tension and compression C. Large loads in chords only D. Large loads on long spans (such as bridges) only

4. For building projects, the high yield strength of 70 ksi steel can open up some advantages for Building Teams when compared to equivalent designs using 50 ksi steel, including:

A. Fewer structural members C. Reduced weight B. Greater spacing of columns and piers D. All of the above

5. By using wide flange or columns of hollow steel sections (HSS) with horizontal channel girts, some engineers are using struc-tural steel products to replace:

A. Exterior window wall systems B. Precast concrete and tilt-up concrete bearing walls C. Unit masonry wall construction D. None of the above

6. Structural products called high-strength or high-performance steel (HPS) are known by their yield strength, commonly given as:

A. 50 ksi steel C. 70 ksi steel B. 50 megapascal steel D. 70 megapascal steel

7. For mixed-use projects and multistory residential buildings, steel framing has been shown to:

A. Require higher floor-to-floor spans as compared to concrete structures B. Limit flexibility of the column grid, from floor to floor C. Minimize loads on foundations, reducing substructure costs D. Require hybrid systems for infill sites

8. Working with architecturally exposed structural steel (AESS) integrates closely the primary and secondary structure and building enclosure, leading to such challenges as:

A. Exacting dimensional tolerances B. Unique fabrication details for exposed connections C. Specialized welds, grinding, and filling D. All of the above

9. An important aspect of planning projects using AESS include discussions of finish quality and the use of physical mock-ups to determine the suitable ___________ for each typical exposed steel condition.

A. Viewing distance C. Cross section B. Yield strength D. None of the above

10. For steel structures, thin-film intumescent coatings are the passive fire-protection materials that insulate steel structures from the effects of the high temperatures and fire. These may be applied as:

A. Nonreactive spray-applied material C. Nonreactive boards B. Reactive coatings D. All of the above

> EDITOR’S NOTEThis completes the required reading for this course. To earn 1.0 AIA CES HSW learning units, study the article carefully and take the exam posted at: www.BDCnetwork.com/SteelAdvances.

STEEL ADVANCES Take the exam online to earn 1.0 AIA HSW Learning Units

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ADVANCES IN STEEL CONSTRUCTION give large-scale … · ADVANCES IN STEEL CONSTRUCTION T ... loaded columns and chords for large trusses are common ... cast concrete and tilt-up concrete