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A stainless star spangled banner

10月 23, 2013    

Problem: lightweight fabrication

To design and fabricate a large replica—in steel and polymer—of the flag that inspired the United States’ National Anthem for an exhibit at the Smithsonian’s National Museum of American History. And to make the fabricated sculpture appear to be a “waving” flag.


Solution: LDX 2101® for strength and stability

Lean duplex stainless steel LDX 2101® in round bar from Outokumpu, provided the high yield strength, welding stability, and superior machining properties to create an elaborate framing system for the 38 ft. long and 19 ft. tall flag.

The frame of the sculpture’s stainless steel support system is mounted to the wall of the museum in Washington D.C. at only one location, with almost all of the flag’s weight supported on what appears to be its flagpole side from which four undulating arms splay out, then taper at their endpoints. To create the impression of a massive waving flag, the entire structure had to be rigid enough to hold the horizontal supports. Some 900 glistening polymer pixels are mounted on the stainless surface of the sculpture, forming the flag’s stars and stripes.

The high yield strength of Outokumpu’s lean duplex, LDX 2101, allowed the structural designers to use less material for the frame, thus creating a more discrete and visually light-weight sculpture. The round bar for the frame was ground to a mirror finish, revealing the superior machining properties of LDX 2101. And with the stability of welding that LDX 2101 provides, the sculpture – which was intended to look like a single rolled piece with sections interconnecting at precise locations – had to achieve tolerances of only fractions of an inch. The result of the fabrication with LDX 2101 was that no point on the flag is out of its proper location (tolerance) by more than 1/16th of an inch over the entire 38-foot by 19-foot installation.

Structural engineers for the project were Robert Silman Associates; the engineers/fabricators were TriPyramid Structures, Inc.; and the designers were Skidmore, Owing & Merrill.

Photo courtesy of Fabricator: TriPyramid Structures, Inc.  ​