Structural Silicone Glazed Guardrails Re-Define the University of Tennessee’s Basketball Arena

A comment such as “What glass?” isn’t always what a project’s architect wants to hear, especially when glass is the dominant design element. But for Bill Blankenship, president of architectural firm Blankenship & Partners LLC in Knoxville, Tenn., there was no better compliment than “what glass?” when it came to renovations at Knoxville’s Thompson-Boling Arena, home to the University of Tennessee’s basketball team. After 20 years of complaints about metal handrails that obstructed the views of those watching the games or other arena events, the University of Tennessee decided a new view was in order.”The University of Tennessee really wanted an improvement to the old metal rails so they went in the complete opposite direction by creating an all-glass rail. This allowed us to remove all of the vertical posts and horizontal lines from people’s views,” says Blankenship.

Because people would be looking through the glass to watch the event below, glass selection was critical. Blankenship had previously worked with glazing consultant Hank Chamberlain with Allied Glass Experts in Kansas City, Kan., on the skyboxes at Neyland Stadium, the University of Tennessee’s football stadium, and his past recommendation seemed on target.

“We’d used a Schott glass with the Amiran (anti-reflective) coating,” Blankenship says. “Now, we had another application in another sporting arena where we could see there could problems with the glare and how it could be distracting.”

Because optical performance was critical, the glass used had to provide clear views.

“Heat-treated glass looks good in [monolithic] applications, but when you laminate multiple lites–and in this case it was necessary to have at least three lites–it becomes difficult to maintain good optical performance,” Chamberlain says. The make-up consisted of 1 1/8-inch thick, low-iron, annealed, triple-laminated glass that has the Schott anti-reflective coating on both surfaces.

In addition, the glass also features a black opacifier on the bottom part that was added by GlassKote USA in Bridgeport, Conn. Because the guardrails are a structurally glazed system the opacifier was used to hide all of the mechanics and attachments.

“The design of this project called for [our product] to be used to coat the bottom section of each glass panel in order to hide the building infrastructure behind it,” explains Warren Belkin a principal with GlassKote USA. “A special metal extrusion was siliconed behind our coating to hold each glass panel in place, preventing it from falling out and landing on the spectators below. This application involved very serious structural considerations in the bond holding the metal extrusion to the glass. It also represented a completely new aesthetic design that was not attempted in the United States prior to this project.”

Being such a unique application, Belkin says his company encountered a few challenges.

“We had to verify that the GlassKote product would perform properly in this application. Also, the coating requirements were very stringent, requiring some specialized processes. For example, we applied an opacified section to each piece of glass and held the dividing line to within 1/16-inch tolerance across and 11-foot long piece of glass.”

Being a structural silicone system, the design was unique.

“To the best of our knowledge this was the first and possibly only silicone structural guardrail/balustrade application in North America,” says Chamberlain. “That doesn’t require as much courage as one might think, especially in an indoor application because it’s not exposed to weathering,” he says, adding that Momentive Performance Materials, formerly GE Silicones, was the supplier of the silicone adhesives. “The support is uniform linearly and there is nothing involved that increases stresses on the glass.”

Before the system could be constructed, though, there were a number of considerations.
“[We had to design for] both the height of the guardrail to keep people from falling and also the structural impact loads that they have to withstand,” Blankenship says.

As the popularity of glass handrails and balustrades for sporting venues continues to accelerate, there are several considerations to take into account.

“Qualify contractors carefully before you entrust someone to do a silicone structural guard balustrade or similar application,” says Chamberlain. “Before you hang glass out over the heads of a crowd and before you rely on it to keep people from falling off the edge of a walking surface be sure that those who are going to execute that design are capable of executing it properly. Be sure that those who are engineering it have a lot of experience in what they are doing in not only glass and glass mechanical properties, but in adhesives and their designs.”

Watch for the September-October issue of the Architects’ Guide to Glass & Metal for a more in-depth look at the Thompson-Boling Arena project.