The engineering behind the art

TKTS booth advances structural use of laminated glass
By Chip Fogg
June 9, 2009
COMMERCIAL : COATINGS AND FILMS, PROJECTS

View the TKTS photo gallery
 

Photo by Stephanie Chan, Brooklyn, N.Y.

Designing an all-glass jewel in the heart of New York City meant more than skinning a traditional frame with façade glass. Novel structural design details for the TKTS booth include its use of laminated glass in load-bearing walls and unique glass beams that hold up the 500-person outdoor seating area.

Building weight is carried on perimeter glass walls, internal glass beams and an internal all-glass bearing wall. The outside perimeter walls, including a non-vertical front wall with holes for ticket-selling, are laminated using two layers of ½-inch tempered glass with a 0.06-inch PVB interlayer.

The exterior side panels extend from the ground upward, as tall as 15 feet at the highest end of the structure. At the top, the sidewall glass is capped with a metal rail, and serves as a balustrade for seated or standing spectators. Inside the TKTS structure, about midway along its sloping cross section, is a seven-layer glass wall, laminated using four layers of ½-inch tempered, low-iron glass, assembled with three SentryGlas interlayers, each 0.06 inch.

"Approximately half of the mass is carried on this bearing wall," explains structural engineer Michael Ludvik of Dewhurst Macfarlane, who worked with Perkins Eastman on the project.

According to Ludvik, structural loading calculations were based on occupancy of 1,000 people, or twice the number of people actually expected on the structure at any time. This conservative approach allowed for dancing or other crowd behavior that could impact dynamic loading.

The glass beams carrying loads to the bearing wall are each 30 feet long, which was a particular manufacturing challenge. Dewhurst Macfarlane drew from the ingenuity of glass structural designer guru Tim Macfarlane to come up with a solution that enabled manufacture in multiple sections, which are spliced together in overlapping, staggered lengths through-connected by metal bolts.

Use of SentryGlas interlayers increases the composite strength of the laminates, because of the stronger shear coupling of the interlayer versus PVB. "Without the strength of SentryGlas(r), a feature such as the frameless cantilevered overhead glass above the purchase windows would have been impossible," says Ludvik.

The canopy above the purchase windows keeps weather off the theater patrons waiting to buy tickets. Its red color is added by a separate interlayer, along with the SentryGlas for structural performance. The canopy extends 6 feet beyond its structural supporting wall, with open edges for design elegance, and features special drip edge finishing to help prevent condensation or rain from trickling down onto guests.
 

The author is in charge of marketing communications for energy and construction markets for DuPont Performance Materials. He can be reached at chip.fogg@USA.dupont.com.