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Volume 23, Issue 5 - September/October 2009

Now You See It,
Now You Don’t

Structural Silicone Glazed Guardrails Help Re-Define the University of Tennessee’s Basketball Arena
by Ellen Rogers

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.

While the use of glass handrails and balustrades in arenas and stadiums is not uncommon, those involved in this project say it was unique.

“It’s my understanding that this was one of the first applications like this in the United States where the glass has no mechanical fasteners; it’s all structurally adhered to the base plate and the floor slab itself,” explains Tim Copeland, senior superintendent with contract glazing firm ASI Limited in Whitestown, Ind. floor slab itself,” explains Tim Copeland, senior superintendent with contract glazing firm ASI Limited in Whitestown, Ind.

Copeland, who has been a basketball fan all his life, says the opportunity to work on the renovation of the arena was a big thrill.

“It was a little leery at first, especially during the first home game when the crowd started singing ‘Rocky Top,’ and everybody was pounding their feet,” admits Copeland, who headed the project team responsible for hanging each glass lite, one at a time. “I was downstairs just looking up and watching how the glass responded. But it went well.”

And thrilling as it was, working on a project such as one that involved suspending massive glass lites over the heads of people in the stadium, required significant planning, coordination and communication of many, including the architect, glazing consultant, contract glazier and suppliers.

A New View
For Blankenship, whose firm, along with Studio Four Design, was selected by the University of Tennessee to renovate the arena, glass was the key to a successful design.

“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.

In addition to adding the glass railing system to the existing seating area, two levels of luxury suites were also added.

“It was like adding a building inside another building,” says Blankenship. “So we not only used the glass railing on the [existing]
level, but we also used it on the front of the new luxury suites.”

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 we believe 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 an 11-foot long piece of glass.”

Blankenship adds, “If you walk in and look at [the application], it looks extremely simple, but it’s the opposite—it’s deceptively simple looking. When it opened I had expected there would be a lot of ‘oohs’ and ‘ahhs’ about the glass, but I heard almost nothing. It was as if there was nothing in front of the people and there was no problem anymore.”

“If you walk in and look at [the application], it looks extremely simple,
but it’s the opposite—it’s deceptively simple looking.”
—Bill Blankenship, Blankenship & Partners LLC

Safety First
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. Life safety was first and foremost, says Blankenship.

“[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,” he says.

Chamberlain agrees, “This type of installation has to be done very carefully, because we are talking about hundreds of pounds of heavy laminates suspended out over the crowds below.” He continues, “My concern is that someone will think it’s a pretty application and then try and duplicate it with monolithic tempered glass or improperly annealed laminates and doesn’t get it right. We certainly don’t want to be an enticement for a less well-done attempt at this.”

One Lite at a Time
The job of installing the system was awarded to ASI Limited. Paul Resch, ASI project manager, says while his firm had a lot of experience working with handrail installations, far more was involved with the Thompson-Boling Arena project compared to others.

For example, because the glass was being manufactured in Schott’s facility in Germany and then shipped to the United States, coordination was essential.

“You have to get everyone on the same page,” says Resch. “Trying to estimate when Germany is going to get the glass out and how it’s going to be traveling on the boat, what to do if there are damages or breakage, because it’s not a situation where you can get a replacement the [next day], so there were a lot of challenges.”

The application of the opacifier also was an important step.

“Communication was critical,” says Resch. “I did two site visits up to GlassKote because this was the first time it had been used in this type of application.”

Speaking of the entire application, Resch adds, “When you have a project that’s never been done in North America you’re pretty excited about being on the cutting edge of something new.”

In addition to the unique design, the size of the glass was also significant: panel weight ranged from 650 to 950 pounds.

“Every piece of glass, more than 340 panels, was set by crane with power cup, and there was very little on-site breakage,” says Copeland, who recalls the day he placed the final lite.

“The brand new floor had just been installed and I had to bring my crane in and put the last piece of glass in, which was the biggest piece on the job—146 inches long and 58 inches tall. This was three days before the first game and when I put the last piece of glass in, everyone was on edge and watching me below, and as soon as I disconnected the power cup from that piece of glass they all started rooting and cheering because it was the one piece of glass that solidified everything; it was the very center suite.”

Proceed with Caution
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.”

Chamberlain also advises to look for the “real loads—true, potential loads.”

“Don’t just rely on the code loads; code compliance is a checklist item and should be verified just to be sure that your design exceeds the legal minimum compliance. It does not guarantee that the design is sufficient, appropriate or even adequate. Look for loads that can be realistically applied in your application and engineer for those and then be sure that they exceed code,” Chamberlain says.

And those involved with this project say it was definitely a learning experience; one that they will be able to apply to future jobs.

“I think that with this being our first application like this we’ll be able to step out and help on other projects looking to do something similar,” says Resch. “Others may not be aware of this type of project so we will also be able to share our knowledge from this.” AG

Ellen Rogers is the editor of the Architects’ Guide to Glass and Metal.