Particularly because curved steel is so often incorporated in exquisite architecture, the demands placed on companies that specialize in bending and rolling steel can be extraordinary. AESS (Architecturally Exposed Structural Steel) becomes the norm with the accompanying stringent quality requirements.
The curving of steel in itself often creates challenges for Bender/Rollers (a term sometimes used to describe specialized subcontractors who specialize in curving structural steel and plate.) The additional challenges of making the steel’s appearance near perfect require extraordinary communication between all the players: the owners, architects, engineers, general contractors, fabricators and Bender/Rollers. And when it comes to purely aesthetic concerns, without communication, there–in fact–could be some arguing about taste
If a picture is worth a thousand words, a mock-up could be worth millions. Almost whatever cost is involved, knowing that all parties are in agreement of what to expect is priceless.
In the case of the Nichols Bridgeway in Chicago designed by internationally renowned architect, Renzo Piano, a mock-up of a section of the bridge with both a welded joint and a bolted joint was brought to the site where it was to connect the Art Institute of Chicago and Millennium Park. The mock-up was inspected by all parties when it was hoisted in the air during the day and again at night with up-lighting. After the inspections, the mock-up was approved with minor welding revisions.
The goal was a surface with no visible weld splices or other surface imperfections. The picture below shows that the goal was achieved.
In the case of the award-winning Norman Y. Mineta San Jose’ International Airport, designed by Fentress Architects, Steinberg Architects, and Gensler, a mockup of a curved wide flange beam which was to occur at one of the most visible areas to the public was rolled to the tightest radius. All the parties involved studied the curved steel sections painted with a particular finish paint texture (satin versus matte). Very little distortion occurred, which was reviewed with the architect to ensure that it was acceptable. Such actions guaranteed that expectations would be met in the finished structure.
Furthermore, the fabricator, Gayle Manufacturing Company, created a detailed spread sheet documenting the precise requirements for each curved structural steel section including whether the member was exposed, partially enclosed, completely enclosed and/or fireproofed.
Agreements were made up-front between the Bender/Roller, fabricator, and erector for the shop drawing presentation and for the tolerances to be maintained. The actual checkpoints were specified on the drawing and then marked on the piece by the Bender/Roller so that the fabricator could verify the dimensions in his shop.
Again, extensive and accurate communication including a mock-up guaranteed that this airport terminal would be a beautifully successful structure.