Seven tons of glass and steel clad a structural stainless frame on the Western Hemisphere’s tallest building.
Brooklyn-based metal fabrication company Kammetal and DCM Erectors of New Jersey were selected to fabricate and install the crowning beacon atop the spire on 1 World Trade Center. The fabrication team executed SOM’s design for a dynamic and complex adornment to one of the country’s most anticipated buildings, along with the help of engineers at Buro Happold to ensure safety at 1,776 feet.
To craft a 15-ton, 50-foot beacon that accounted for thermal expansion and movement, Kammetal modeled and drew their designs in SolidWorks. The company’s team laser cut 48 triangular 316 stainless steel panels with ¼-inch thickness in a nondirectional finish to clad DCM’s square tubular steel frame. “Before we started the project, we had the structural frame 3D scanned to generate a point cloud,” explained Sam Kusack, president at Kammetal. “Because the structure was so dynamic—it contains zero right angles or reference points—we had to verify the conditions.”Kammetal modeled the beacon in SolidWorks. (courtesy Kammetal)
Once the angles were defined, multiple processes were employed to achieve the gentle curves of the cone. In order to ensure even bumping, or bending on a press break, the fabricators laser-scribed lines at every 1/8-inch along the panels’ interior. And to securely fasten each panel to the complex angles of the frame, Kammetal also devised a proprietary clip system that affixes each panel without obstruction. Clips that fell along certain angles could not be bent safely and had to be welded into place.
To install tempered and laminated heat-soaked glass panels from Oldcastle, Kusack designed a proprietary vacuum panel lifting mechanism to adjust the panels without affecting the edges. “There’s a gap of just 3/8-inches, so it was the only way to handle the panels,” he told AN. The arm required a unique radius and capacity for strength to pick up each panel in a balanced manner and evenly align the gaps. Custom gaskets fabricated in London seal the glass from the elements. Kammetal also realized SOM’s original design for a rainscreen, which serves as a ventilation component. The beacon houses various mechanicals, including FAA lighting, so slots were laser cut to allow for air-cooling.
To install the beacon, DCM Erectors fabricated a series of frames, supports, platforms, and transportation devices to safely place the beacon on top of the spire. “The owner of DCM invented a lot of gear and technology to realize this installation,” Kusack marveled. For example, a holding location was constructed at 1,700 feet to assemble the final interior and exterior components that all had to be raised an additional 70 feet so the apex could be lowered into place.