Before designing the Gerald Ratner Athletic Center at the University of Chicago (EAE National Winner 2004), the architect, Cesar Pelli concluded that “Everyone we spoke to at the University wanted a place that would be not just functional, but exciting – exciting on the inside and from the outside.”
Aesthetic Appeal. His solution of a cable-stayed waved roof with soaring masts makes the building instantly recognizable and exciting, and provides a conceptual link to the Gothic architecture of many of the university’s early buildings.
Curved Steel. Early in the project, OWP&P, the architect of record, contacted an AISC Associate Member Bender-Roller to ask if it was possible to create an S-curve within one beam with no splicing. The project manager and the machine operators agreed that the company could indeed roll the eight pieces of W33 x 169 x 93ft. long beams each to an 85ft. radius (14ft. arc) followed by a 22ft. straight tangent followed by a 146ft. radius bend (reverse) (12ft. arc). (Please see photo of S-beams being installed.)
The Bender-Roller proceeded to roll-curve this steel as well as W21 x 93, W18 x 76, W14 x 48, W14 x 30 and W14 x 22 for a total of 310 tons of beams cold bent about the strong axis to complete the flattened-S-curved roof. Picking the best of 60 specialized machines for each application, the company maintained AESS quality. The architects, engineers, general contractor, and fabricator all visited the shop to witness the bending.
Cost. By creating one-piece reverse curves, the Bender-Roller eliminated 16 weld splices costing at least $1,500 each, thereby reducing the cost of the project by $24,000.
Versatility. Steel cables from three tall masts over the pool, two tall masts over the gym, and 15 smaller masts support these roof girders (See Modern Steel Construction, March 2004, “Design Considerations in Cable-Stayed Roof Structures.”). The roof’s shape was then “tuned” by the cables until it met the desired shape.
With the masts doing the heavy lifting, only thin beams were needed to span large, column-free areas. With the east wall being all glass, and with a band of glass just under the sinuous roof line, the roof floats like a magic carpet.
Success. Pelli explains that “the Gothic arch developed as the most daring use of stone construction. The flying buttress is perhaps the most recognizable element which takes the structure from the interior to the exterior and expresses it as flying through air.” At the Ratner Center not stone but steel creates a supporting structure external to the body of the building. Pelli’s combination of curved beams, masts, and cables all attest to the beauty, economy and versatility of steel in construction.