By Lucy Perry
AESS: Sophisticated but Complicated Sometimes misunderstood, exposed steel projects can drive up costs
Photo credit Ryan Dravitz Photography
tructural steel projects aren’t always run-of-the-mill. When exposed steel is involved, fabrication can get complicated. Architecturally Exposed Structural Steel (AESS) is a complex design process that can drive up project costs and create headaches for the project owner, the fabricator, the steel erector, and the architect. AISC has created a standard for AESS design, fabrication, and erection, but it’s not always fully understood by the design team, or used as it was intended. “When left exposed, structural steel can express form, integrity, and beauty in buildings while simultaneously demonstrating function and strength,” states AISC. “Today, many buildings showcase AESS to provide an identity and even create iconic structures. AESS elements feature higher degree of finish and are handled with a higher level of care during fabrication and erection. Beautiful and creative expression can be achieved in the broad range of shapes, tapered forms, curves, colors, glossy or matte finishes, as well as seamless or tectonic expression.”
No easy feat The Denver International Airport’s public transit center offers a stunning example Lucy Perry operates WordSkills Editorial Services in Kansas City, Mo. She has spent 20 years following the North American construction industry. She can be reached at email@example.com.
of AESS-integrated building design. A 2016 SEAA Project of the Year Award winner, the project features a steel diagrid, “a highly efficient and aesthetic triangulated truss system that employs a diagonal grid of steel support beams,” reads a description of the project in the Winter 2016 issue of Connector The diagrid system required less structural steel than a conventional steel frame, saving approximately 20% of the weight, but the construction was extremely challenging. It demanded precision, since the joints are more complex than conventional orthogonal structures. Some of the walls of the girders are 2” thick, and each connection was full-penetration welded to create a rectangular tube. “To achieve the precise geometry of the diagrid, the box members were rolled, twisted, and skewed, closely following AESS standards,” according to the Winter 2016 article. Though aesthetically pleasing, AESS-integrated building designs throw up a red flag for fabricators in figuring cost estimates, because it means they’ll have to spend more time on the cosmetic look of the steel component in addition to ensuring structural integrity, says Chris Legnon of Cooper Steel. The process involves removing blemishes from raw steel, and smoothing out weld marks. “It increases the time you have to spend and the care you have to put into each piece you fabricate, so it becomes a higher-cost item on the front end,” says Legnon, vice president of preconstruction for the Shelbyville, Tenn., company.
18 | THE STEEL ERECTORS ASSOCIATION OF AMERICA
In its 2016 Code of Standard Practice, the AISC has outlined a method for specifying AESS by creating five categories that define levels of exposed steel fabrication and erection, essentially based on the visual distance between the public and the steel element. The categories are labeled AESS 1, 2, 3, 4, and C for custom. For the numerical categories the higher the category, the more complicated the design, which means the more time and cost involved at the fabrication and erection stages. However, to avoid pigeonholing the design teams into one of those four categories, the Custom category is identified to allow only specific items which are of an aesthetic nature to be qualified, in hopes that this hybrid, for lack of a better work, will provide the value of the desired AESS components without the unnecessary cost of default conditions which may otherwise be carried by one of the numerical categories. While the code creates a common design standard whereby everyone involved in the project understands what’s being asked, what’s expected to be fabricated, and how that structural steel member is to be erected, when the term AESS is thrown into a project without being fully understood by the design team, the result can be confusion and even result in negative financial and schedule impacts to the project which otherwise may have been avoided. “A lot of times an architect will call for ‘AESS,’ but won’t indicate what level, so you
In this issue: Communication Key to Bidding AESS; Eliminate Wire Feeding Issues; 2018 Convention Review