CompositesWorld
Issue link: https://cw.epubxp.com/i/517026
JUNE 2015 46 CompositesWorld INSIDE MANUFACTURING p. 49) not only ofered the highest grade of weatherproof wall for this high rise, but also signifcantly streamlined the construction process. "Te whole façade was put up under one subcontractor," says Kreysler, adding, "Even though our system enabled the elimi- nation of 1 million lb of steel, it turns out cutting three passes around the building was worth more." FRP's moldability also was important. Typically, unitized panel systems — a modernized, computer-modeled update to traditional curtainwalls — feature glass or metal panels, each enclosed, typi- cally, by a 203-mm thick aluminum frame. Frames lock together with gaskets to tolerances within 1.6 mm to form the building's weatherproof exterior barrier with an integrated aesthetic surface. "Tey are great, and work well for a fat wall," says Kreysler, "but not so much with complex, curved geometry." So each contoured SFMOMA FRP rain screen panel would be attached to a fat backing structure — a unitized wall panel that includes a vapor barrier, insu- lation and weather barrier for the building. Te unitized wall system fabricator, Enclos (Eagan, MN, US), also a key player in the design- assist process, worked with Kreysler & Associates to fnalize specifcs 1 The FRP panel production program was driven by digital fabrication tools. This required careful management of the 3D computer models that governed panel geometry and coordination of those models between the Kreysler and Enclos façade fabrication teams. 2 Molds were CNC-machined from EPS foam. 3 After applying the mold release, Kreysler technicians sprayed on the Fireshield 285 coating. 4 An impregnator was used to wet out three plies of glass fber woven roving for each panel, which were then applied to and rolled out on the molds by hand. Typically made in panels, this aesthetic veneer was the focus of Kreysler & Associates' design-assist contract for the SFMOMA expansion. Snøhetta's striking design of a white undulating surface, reminiscent of rippling waters in nearby San Francisco Bay, originally called for glass fber-reinforced concrete (GFRC). "But we suggested an alternative: lightweight FRP panels," Kreysler recounts. "At a fraction of the weight," he notes, "they opened up another interesting option for construction." A project's main contractor always prefers to minimize the number of subcon- tractors, particularly on a part of the building that is latent with liability, such as the exterior wall, he explains. But in the design as conceived, one subcontractor would be required to install the gypsum board, another would follow with the rubber facing, then yet another would anchor a secondary steel frame required to support the heavy GFRC rain-screen panels, which would be installed by a fourth subcontractor. "However, our panels were light enough to be mounted onto unitized wall panels, pre-assembled of site and delivered as needed for installation." A unitized wall system (see "Learn More,"