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Strut connection details at Calgary International Airport. 70-foot-tall architecturally exposed steel "delta frames" at the Queen Richmond Centre West, Toronto, ON. A PR IL 2016 | 35 Structural Steel PHOTOGRAPHY COURTESY CAST CONNEX; SUPERMÉTAL/TERRI MEYER BOAKE Steel Buoyant A s long as honesty and integrity of design are valued and structural steel con- struction methods remain in use, architecturally exposed structural steel (AESS) seems poised to remain a significant part of the modern built envi- ronment. AESS, in turn, supported by new technologies, smarter engineering and the latest and best design esthetics, in addition to adding lustre and elegance to projects, will surely continue to burnish the allure of structural steel construc- tion in general. To judge by some of the responses it has been getting, a new guide for specify- ing AESS, intended primarily for architects, appears to be making AESS an eas- ier proposition for all stakeholders involved. Issued by the Canadian Institute of Steel Construction (CISC) a few years ago, the Guide for Specifying Architecturally Exposed Structural Steel was developed to facilitate better communication among architects, engineers and fabricators. "It was felt that visual references would help all parties understand the intent of the new AESS documents as applied to the design of structures," the guide says. The new guide might not only give AESS a boost, but, by extension, much of the structural steel sector across the country. It was, apparently, very helpful on a recent project at Toronto's Pearson Airport. "The architect has definitive guide- lines and the owner can see clearly what he is buying. Everyone can see exactly what the AESS levels, whether one, two, three or four, will look like," says Stephen Benson, president of Benson Steel Limited. Structural steel's advantages include its strength, lightness and suitability for long spans. Frequently updated software over the last two decades has helped the design community make good use of these advantages, Benson says. He makes the point that electronic storage of designs and the rapid sharing of information among architects, engineers and fabricators, greatly facilitate the appropriate design for upgrades, renovations and building additions. A project that his firm is providing structural steel for involves a 60-year-old building whose first 30 floors are being renovated and to which another 15 floors are being added. "The original is steel and concrete. There's a lot of existing steel that's being reinforced. The additional 15 floors are steel framed, not concrete. The relative light weight of steel makes it an optimal choice of structural design solu- tions," Benson says. When the splice or connection of a truss is exposed, the architect's involvement is crucial and compromises are generally necessary, says Sylvie Boulanger, VP of technical marketing at Supermetal Structures Inc. "This may involve beautifying the bolted connection, converting a welded connection into a discrete bolted one or making the field-welded connection more practical. The CISC guide for specifying AESS is a good reference," she says. A crucial component of the guide is the categories matrix. It encompasses four levels, AESS 1 through to AESS 4, which are cumulative. For example, if AESS 2 is specified, the finished work includes all attributes of the preceding level(s), AESS 1 in this example, as well as those of the one specified. "People are getting more com- fortable with the categories, but they're not for each individual steel member. People should think in terms of the category for a particular area or set of components of structural steel," Boulanger says. A feature of the system is that as soon as any level of the four categories is speci- fied, fabricators know that weld spatter must be avoided. As levels ascend, require- ments increase, up to AESS 4, where they are the highest – and typically the most costly. The CISC guide's categories matrix identifies in general terms the cost pre- mium as specifications escalate through AESS levels. The categories are on all drawings. As a result, all fabricators that bid on a project, if using the new guide for specifying AESS, know right away whether upper truss connections require grind- ing or not. On a recent project at Calgary International Airport, various components of trusses were specified referencing AESS categories. Describing some of the crite- ria that drove the selection of AESS categories, Boulanger says, "As the roof trusses are typically well above a six-metre viewing distance, the quality of the truss con- nections and fabrication was set at AESS 2 category. It was decided that the column struts to trusses would require a higher treatment, as they are closer to view, so this section was set at AESS 3." She adds, "It was the first time for all parties that these categories had been explicitly specified during the bid process and applied throughout. The result was better overall collaboration. This was especially evidenced during inspection of the truss pieces by the owner, general contractor, architect and structural engineer at Supermetal's fabrication plant in Quebec City." AESS seems to be catching on across the country. "More architects are exposing steel structures. It can be seen as truth in architecture – let the people see how it's built. The TELUS Garden in Vancouver is a great example of exposed steel. Exposed steel is a trend I'm happy to see. Vancouver International Airport is a great steel and glass job," says Rob Third, president of George Third & Son. A retreat in Whistler built for Third and his family, and nicknamed the "man of steel cabin" because of its all-steel frame, stairs, rails, even beds, and perhaps the fact that the firm has been around for more than 100 years, has sparked a new busi- ness sideline. "Each month, we're seeing steel for a house go through the plant," Third says. Structural steel's versatility gives architects the freedom to achieve their most ambitious visions by GODFREY BUDD

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