Arched Marvel
Crews install dramatic curved atrium skylight,
a centerpiece of the Gilman renovation

By Greg Rienzi, Photos by Will Kirk
October 15, 2009

Look up in the sky: It's a bird, it's a plane, it's...an atrium roof!

Crews recently put in place the steel grid frame for the 60-foot by 60-foot glass skylight that will top Gilman Hall's new atrium space. Designed, fabricated, and installed by Novum Structures, the skylight will comprise 154 square glass panels and two vertical glass walls at each end, and it will span the entire courtyard without intermediate support.
           
Novum gave the skylight a barrel vault roof design and used an innovative "block node" structural system. The company's corner-clamped glass glazing system uses custom stainless steel clamps to support the panels at the four corners only. The result is a one-of-a-kind atrium roof.
           
"This is not something you're likely to find anywhere else, and I would guess that there are very few skylights of this general design type in the United States," says Bob Gray, project manager for Novum Structures.
           
The arched structure, a precisely engineered combination of compression members and tension cables, will be less than 10 inches thick.
           
Work on the skylight began Sept. 28 and has moved relatively swiftly. Its four 8,000-pound framing ladders (or ribs) were assembled on the ground and then lifted individually by a massive 200-foot, 200-ton crane, and then fastened into place by hand. Crew managers say the process went "smoothly," aided by a string of good weather.
           
Later this month, the double-insulated, 1.5-inch thick glass panes—each 5 feet square and weighing 500 pounds—will be fitted into the blocks and clamped down, then finished off with a waterproof joint. Next comes the installation of two vertical glass walls at each end of the skylight. Stainless steel tension cables will be strung underneath the structure in a criss-cross pattern to provide additional support and prevent any movement.
           
David Miller, project architect with Kliment Halsband Architects, says Gilman's skylight will be relatively thin, but sturdy enough to keep out the elements and stand the test of time. People sipping coffee or strolling in the courtyard below, he says, will feel as if they are in an immense greenhouse.
           
Miller says the decision to incorporate a skylight into the design came down to the desire for sunshine and a touch of the dramatic.
           
"We wanted to create a large room that was open to the outside, rather than put in a ceiling that might give you the sense you were in a large theater," Miller says. "We also wanted to maintain the character of the building and preserve the feeling of being in an open courtyard. You'll have a great view of the sun and clouds during the day and the stars at night."
           
Before the renovation began, the atrium was an unused exterior light well. Its original purpose was to let natural light—and a cool breeze on a warm day—filter into the building's interior offices. Miller says the skylight will once again allow light to flood into the offices and classroom space that ring the atrium. Thanks to air conditioning, those breezes are no longer needed.

Officials expect the skylight to be completed later this fall, allowing work in the atrium below to continue undeterred by the cold and snow of winter.