Ah, the city of Boston … home of the Celtics, the Red Sox, a famous tea party and Paul Revere’s ride. This week it’s home to the AIA Show, where I’m sure many glass folks are right now—and with good reason, too. It’s a great place to launch new products and innovations, and to really get those great ideas in front of architects, specifiers and designers.
Like many of the products on display inside the walls of the Boston Convention Center, the building itself is also a great display of glass and metal (check out the cover of the January 2005 USGlass by clicking here: http://www.usglassmag.com/USGlass/usgtoc/2005/Jan2005.html).
Architect for the job was HNTB/Rafael Viñoly and the contract glazier was the Canadian firm Ferguson-Neudorf Glass Inc. The job features a unitized curtainwall system, dry joint 1/8-inch plate panel system, a structural glass wall, as well as all glass revolving doors and entrance systems.
Architect for the job was HNTB/Rafael Viñoly and the contract glazier was the Canadian firm Ferguson-Neudorf Glass Inc. The job features a unitized curtainwall system, dry joint 1/8-inch plate panel system, a structural glass wall, as well as all glass revolving doors and entrance systems.
Boston definitely has a lot to offer when it comes to glass. Take the famous Hancock Tower for instance (thanks to www.freefoto.com for the image shown here). The tower is known for one of the most famous cases of glass breakage. For years it was a mystery … what caused all of those lites to break … windowpanes that plummeted hundreds of feet to the ground below? An article in the February 2001 USGlass written by Thomas A. Schwartz, P.E., principal investigator of the Hancock Tower glass breakage, says, “A gag order imposed on the parties to the resulting legal dispute prevented the release of the facts regarding the cause of the breakage—giving rise to many theories and myths, some of which exist to this day. Initially, many design professionals thought the reason for the breakage lay in the fact that the tower swayed excessively in the wind. Although it was indeed swaying substantially, this was not the reason for the glass breakage. Another hypothesis was that wind forces at hot spots, which resulted from the rhomboid shape of the tower, caused overstressing of the glass. Substantial hot spots did exist, but only a small percentage of the glass was subject to anything near the load for which it had been designed. Still another myth was that the windows broke because of the stress they endured from the settlement of the tower’s foundation.” Click here to read the entire article: http://www.usglassmag.com/USGlass/2001/0102/bad.html.
So what was the cause? It was the IG.
“The insulating glass units that made up the façade were fabricated with a thin lead tape spacer to separate the two [lites] of glass. The tape was soldered to the glass after the edge of the glass was coated with a film of copper to make it more receptive to the solder. This created a tenacious bond between the spacer and the glass, which constituted the product’s greater strength as well as the source of it demise.” The article goes on to explain that by the late 1960s, large-size glass with tints and reflective coatings were architecturally popular. “The large sizes and increased thermal loads associated with the tints and coatings caused substantial differential movement and increased stress along the glass-to-tape bond,” eventually causing the bond to separate. In some areas the bond was so strong that the tape ripped tiny pieces of glass from the surface.
So there you have it--the story of that famous glass breakage. While you’re in Boston, if you have time to take a walk, maybe you can see the Hancock Tower yourself and share this history tid-bit with some of the tourists passing by.
2 comments:
You've told us the problem. What was the solution?
According to Michael Flynn, a partner with Pei Cobb Freed & Partners, the architectural firm that designed the Hancock Tower, the glass was replaced with 1/2-inch, fully tempered, monolithic glass that has a neutral metallic coating on the inboard surface(LOF 1-114).
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