Volume 41, Issue 7 - July 2006

Clear Out of the Park
Glass Railings Have an Increasing Presence in Sports Arenas
by Charles Cumpston

Sports, be it baseball, hockey or football (to name just a few), are big forms of entertainment. And like other entertainment venues with which sporting events are competing, their facilities have to be user-friendly. After all, many movie theatres now have stadium seating to afford unobstructed viewing; sports facilities can and do offer the same.

That’s where the glass railings come in.

“Glass railings have been installed in sports arenas for years,” points out Valerie Block, senior marketing specialist with DuPont Building Innovations in Wilmington, Del. “The new trend is for glass railings that are only supported on the edge of the glass without supports on the sides or top of the glass. This allows for a truly unobstructed view of the action below,” she adds. Block explains that glass railings are used to keep spectators safe from accidental impact and falls, as well as from fly balls that reach the upper decks of baseball stadiums. 

Julie Schimmelpenningh, architectural technical applications manager for Solutia Inc., Performance Films in Springfield, Mass., agrees. 

“The use of glass railings in sports arenas has likely been driven by the desire to have as many unobstructed views as possible and a sense of openness. I don’t have any stats on this particular application, but we are getting many more inquiries for this application than we did even three years ago.” 

She also points out that the use of glass in these applications is contemporary in design. 

Design Challenges

While all railings are required to be durable, Block says, glass railings in sports stadiums must be especially so because of the large crowds of people that are assembled and the possibility that fly balls or hockey pucks could hit the glass and cause damage. “Spectators are sitting up close to the glass railings in sports venues, often with their faces close to the glass. Safety is an issue if the glass breaks.”

Schimmelpenningh agrees that all glass railings have challenges, but says there are some unique considerations: masses of people may be pushing against a rail at a sports stadium where they may not be in more “traditional” railing applications. 

“There seems to be a desire to do one-sided support glazing and this sometimes gets designed as sinking glass into concrete as [contractors] are used to doing with other materials,” Schimmelpenningh explains. “This should be avoided without protecting the glass from thermally-induced breakage and incompatibility.”

Block says that in order to use laminated glass in this one-sided application, the interlayer must be able to provide stiffness and strength beyond that of the traditional laminated glass interlayer. 

Need to Know 

Given the growing popularity of glass railings for this application and these challenges, how can the glass industry better educate the architectural community on glass railings in sports arenas?

“They [architects] need to be sure that [glass railings] are specified with the proper safety considerations in place and that they meet any code requirements for top rails, anchoring and load capability,” says Schimmelpenningh.

“Architects need to know about the glass retention benefits of laminated glass in railings,” Block adds. “This is especially important in sports arenas where large crowds are present. If the glass in the railing breaks, it will remain in place until replacement can be made. While monolithic tempered glass is widely used in railings and as a safety glazing product in general, it cannot provide glass retention once broken.” 

According to Block architects also need to know the differences in laminated glass interlayers. “PVB is a traditional interlayer used in laminated glass for safety, security, impact resistance and sound control. A stiffer interlayer may be required if the edges of the glass are exposed or the glass is only supported on one edge,” she states. “Architects need to know about edge finish. Edgework on tempered glass is done prior to tempering. Once the glass is laminated, further polishing is not recommended. Thus, there will be a more visible layering effect than on laminates where polishing is done after lamination. Architects need to work with the installer to understand the glazing system requirements, including the proper edge bite, cushioning of the glass and the compatibility of sealants.”

Setting Standards
 
The ASTM International Subcommittee Performance of Railing Systems and Rails for Buildings (E06.56) to ASTM E 06 on Performance of Buildings, and task group 08 is working to develop a test method and specification for glass railing systems and rails for buildings.

The test method describes procedures for assessing the static strength, impact performance and post breakage retention characteristics of railing systems, guards and balustrades. It applies to systems having glass as the major structural component or the infill panel(s) in one-, two-, three- and four-side support systems as used in various applications. 

The test methods are limited to concentrated and linear loads with additional impact testing similar to CPSC 16 CFR part 1201. Designations of the systems are separated by glass; in-fill panels versus structural panels. The location of load placement is the first test performed on the railing system. The impact procedures follow, and the test method is completed by providing directions on interpretation of the results. These test methods address the capability of glass railing systems to continue functioning as a barrier that provides a mechanism to account for potential fall-through after impact or glass breakage. 

The complementary document to the test method is the ASTM E 2358 Standard Specification for the Performance of Glass in Permanent Glass Railing Systems, Guards and Balustrades. As with the test method, this specification is essentially derived from the metal railings specification with modifications that make it applicable to glass. While the criteria provides for normal and anticipated building uses, it does not account for abuses to the systems. 

Design requirements are outlined in the specification that describe railing heights and resistance to penetration, hand rail design and offset limits. It should be noted that these are the basic height requirements only; several exceptions and exemptions exist and the specifier should reference and ensure compliance with the building code prior to installation.

Classifications of system type and performance level are also outlined in the specification. Level one relates to basic, level two relates to safety and level three and four relate to enhanced performance. 

The overall pass/fail criterion for structural performance requires glazing retention to occur and the glass to be unbroken at the completion of each test. For the shot bag and pendulum impact, the criteria requires the system to be retained after impact in the framing system such that a 75-mm (3 inches) solid steel sphere will not pass through any part of the system using a force applied horizontally of 18 N (4.0 pounds). 

The products evaluated by this specification have the potential to be subjected to a wide variety of forces and impacts that could cause breakage and lead to the possible fall-through hazards if the glazing vacates the frame. This specification outlines a test methodology that takes into account various impacts ranging from a sharp blow of a knee to a blunt object impact to a full-body impact. Although not every form of impact or force can be accounted for in a standard document, this specification provides a means of establishing a level of retention that may help glazing in railing systems perform its intended function of protection and fall-through prevention. Once a system has been tested successfully, there are permissible variations and substitutions of glazing products outlined in the specification that provide flexibility for manufacturers.

USG
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