AGG

Volume 27, Issue 3 - May/June 2013

Glass Tech

Unconventional Concepts
Rails, Stairs and Floors Offer Intriguing Designs by Ashley M. Charest
by Ashley M. Charest

he number one question we receive at the Glass Association of North America (GANA) is not directly about design, but instead is about mechanics. “What is the weight of glass?” The answer is “it depends” but one sample would be approximately 6.4 lb/ft2 (31.2 kg/m2) for half-inch glass. That being said, the more intriguing questions we receive are about how our members’ products can be used in “unconventional” ways.

Floors, rails and stairs typically are thought of as wood and metal products, and historically that assumption is correct. However, more and more individuals in the design community are making glass a “typical” choice when they are designing these three building features. With these features becoming increasingly more common, we have created a series of bulletins on the subjects, along with a variety of others.

The text below is an excerpt taken from a recently updated document, LD 06-0413 Glass Floors and Stairs.

Choosing the Glazing
Several types of glass products are used in floors and stair treads, including laminated glass and glass block systems. A description of these glass types follows:
Laminated glass - two or more pieces of glass bonded together with an interlayer.
The glass may be annealed, heat- or chemically-strengthened or fully tempered.
Glass block - a decorative hollow glass building block that is set in an aluminum or concrete framework and sealed against moisture.

Providing Slip Resistance
Slip resistance of a walking surface is an important safety consideration. The Occupational Safety and Health Administration (OSHA) requires a minimum slip resistance, expressed as a static coefficient of friction of 0.50. However, special activities, such as dancing, may require a different level of slip resistance. Glass floors used near entrances that may get wet require special consideration.
There are a variety of ASTM test methods that measure slip resistance using specific test equipment under dry or wet conditions. These are:
• F 609 - Standard Test Method for Static Slip Resistance of Footwear, Sole, Heel, or Related Materials by Horizontal Pull Slipmeter (HPS);
• F 1677 - Standard Test Method for Using a Portable Inclinable Articulated Strut Tester (PIAST);
• F 1679 – Standard Test Method for Using a Variable Incidence Tribometer (VIT); and
• D 2047 - Standard Test Method for Static Coefficient of Friction of Polish-Coated Flooring Surfaces as Measured by the James Machine.

Other industry standards, such as ASTM F 1637 - Standard Practice for Safe Walking Surfaces, ASTM F 1646 - Standard Terminology Relating to Safety and Traction for Footwear and Underwriters Laboratory (UL) UL 410 – Slip Resistance of Floor Surface Materials, address the safety issues of walkway surfaces from a more general point of view.

Processes designed to roughen the top surface of the glass to provide slip resistance include sandblasting, acid-etching, ceramic frit and embossing. It is important to note that sandblasting may reduce the strength of the glass by as much as 50 percent; therefore, glass flooring should never be sandblasted in the field without a complete engineering analysis.

Considering Modesty
Modesty becomes an issue when glass floors are found on upper levels and inappropriate lines of sight are created from spaces below. It may be necessary to incorporate a decorated or translucent interlayer in the glass.

Testing
Glass floors can be tested for strength or impact resistance. Test methods that are used include:
• ASTM E 72 - Standard Test Methods of Conducting Strength Tests of Panels for Building Construction;
• ASTM E 695 - Standard Method for Measuring Relative Resistance of Wall, Floor, and Roof Construction to Impact Loading; and
• ASTM E 2322 - Standard Test Method for Conducting Traverse and Concentrated Tests on Panels Used in Floor and Roof Construction.
Below is an excerpt from LD 09-0513 Use of Laminated Glass in Glass Railing Systems.

Building Code Requirements
Chapter 24 of the International Building Code (IBC) addresses glass used in handrails and guards. It states that glass used as a handrail assembly or guard section is to be a minimum thickness of ¼ inch (6 mm) monolithic tempered glass, laminated tempered glass or laminated heat strengthened glass. Glazing in railing in-fill panels is required to conform to Category II impact requirements of the Consumer Product Safety Commission (CPSC) 16 CFR 1201 or Class A of ANSI Z97.1.

Two new provisions were added to the 2009 IBC. The first is an exception to the requirement of a minimum of three glass balusters supporting each handrail or guard section. The code requires attached handrails or guards, except where the glass balusters are laminated with two or more glass plies of equal thickness and the same glass type when approved by the building official.

The second provision addresses glass installed in exterior railing in-fill panels or balusters in wind-borne debris regions. It says the glass is to be laminated glass complying with safety glazing impact requirements. When the top rail is supported by glass, large or small impact testing is required.

Glass Railing Standards
Glass railing system testing is done according to ASTM E 2353-06 Standard Test Methods for Performance of Glass in Permanent Glass Railing Systems, Guards & Balustrades. The standard evaluates static strength, impact resistance and post-break retention. Railing systems are specified according to ASTM E 2358-04, Standard Specification for the Performance of Glass in Permanent Glass Railing Systems, Guards, and Balustrades. These systems include glazing infill, as well as structural glass railing types.

 

Architects' Guide to Glass & Metal
2012
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