Iano's backfill

State of the Art Glass Engineering

As Unbreakable as ... Glass? (www.nytimes.com, July 6, 2009) discusses developments in the manufacture and use of glass as a structural material.

Interesting supplemental material accompanying the article includes a video and graphic illustrations of the glass booths' construction, a slide show of noteworthy applications of structural glass in architecture, and a graphic explanation of the processes for thermal and chemical tempering of glass.

A link to a video clip on youtube.com, illustrating Prince Rupert's Drop, a simple and intriguing demonstration of heat strengthening of glass in action is also worth a look.

Developments In Safety Glazing

Glazing, as per code: fireproof and wire-free, Architecture, April 2004, reports on changes in building code requirements for safety glazing in fire-rated applications. With the International Building Code (IBC), wire glass is no longer a permitted option for use in hazardous locations such as doors, sidelites, and areas close to the floor in fire-rated assemblies. It has long been recognized in the industry that wire glass does not fully meet impact requirements for use in hazardous locations, but until recently codes have included wire glass as an exception since there were few if any alternative glass products that had some degree of resistance to both impact and fire exposure. With new affordable, fire-resistant and impact-resistant glass products available, this is no longer the case and the exception for wire glass in these applications has been deleted.

Acceptable glazing products for fire-rated, hazardous locations include transpartnt glass ceramic and intumescent glass. Glass ceramic are single glazed products that meet both impact resistance requirements and provide up to a 3-hour fire resistance rating. Glass ceramic can also be provided in double-glazed assemblies for improved thermal or acoustical performance.

Intumescent glass are double-glazed products with an inner layer of transparent sodium silicate that, when exposed to high temperature, turns opaque and forms an insulating layer that can provide up to a 2-hour fire resistance rating. Unlike glass-ceramic, intumescent glass becomes insulating when exposed to fire. This property allows this product to meet the more strict fire test requirements for true fire-rated wall assemblies, not just for rated doors and windows. Thus intumescent glass products can be used over larger areas and offer potentially greater design flexibility. Intumescent glass is also more expensive than glass ceramic.

More Information
TGP Fire Rated Glass and Framing
Vetrotech
Pilkington

Developments in Glass Technology

Building Design & Construction, 03-04, includes a number of articles on new developments in glass technology.

Testing curtainwall glazing in situ
Keeping Glazed Walls Healthy discusses techniques for in-place verification of the condition of curtainwall glazing units. The article notes that glass units frequently do not last the life of other major curtainwall components, and their evaluation can be important as the building ages, or as part of due-diligance evaluation during building sales.

Test ASTM E576 "Standard Test Method for Frost Point of Sealed Insulating Glass Units in Vertical Position" specifies a method for determining the moisture content of air within sealed glass units and can be used to predict future fogging of units due to internal moisture condensation.

A second ASTM test, identified in the article as E1392, is described as a relatively new and not well known test for non-destructive testing of structural-glazed installations. In these installations glazing is attached to the curtainwall system only with silicone adhesive and without any mechanical attachment. It appears to this author that the ASTM reference provided in the article is incorrect--and should be ASTM C1394 "Standard Guide for In-Situ Structural Silicone Glazing Evaluation".

On a separate topic, the article also discusses the occasional spontaneous breakage of fully tempered glass due to the unpredictable pressence of nickle sulfide inclusions in these glass products. To avoid risks to occupants, some glass manufacturers recommend against the use of fully tempered glass in vertical curtainwall glazing or in other locations where falling glass could pose a threat to building occupants or passers-by.

New Low-E High-Transparency Coating
Pyrolytic glass coating debuts discusses Pilkington's new Eclipse Advantage coating that provides higher transparency and lower reflectivance than Pilkington's current Eclipse product that it replaces. The low-e coating is also noteworthy for being applied in a pyrolytic "hard coat" process that is more durable than competing sputter applied "soft coat" products. The hard coat product is claimed to be less subject to damage during secondary operations such as laminating, cutting, heat treatment, etc.

Product Updates
Products Glass provides several pages of annoucments on glass products related to sound control, fire control, low-e glass, high-efficiency clear glass, protective glass films, safety glass, wire glass, and more.

Blast-Resistant Glazing

Building security continues to figure prominently in articles on design and construction. Shatter-Proof, Building Design & Construction, 01.04, dicusses design of windows and glazing for blast-resistance. Referring back to the 1995 Murrah Federal Building bombing, the article notes that 60% of the nonlethal injuries sustained in that event were due to shattered glass, and shattered glass was found as far as one mile from the blast site.

For designers dealing with this issue, this article provides useful information on glazing protection levels established by the GSA for protecting buildings at risk. The GSA standard defines performance conditions based on the response of glazing to a specified blast event, and the level of protection provided by the glazing system. See the following table:

Performance Criteria	Protection Level	Hazard Level	Description of Window Glazing Response
1	Safe	None	Glazing does not break. No visible damage to glazing or frame.
2	Very High	None	Glazing cracks but is retained by the frame. Dusting or very small fragments near sill or on floor acceptable.
3a	High	Very Low	Glazing cracks. Fragments enter space and land on floor no further than 3.3 ft. from the window.
3b	High	Low	Glazing crack. Fragments enter space and land on floor no further than 10 ft. from the window.
4	Medium	Medium	Glazing cracks. Fragments enter space and land on floor and impact a vertical witness panel at a distance of no more than 10 ft. from the window at a height no greater than 2 ft. above the floor.
5	Low	High	Glazing cracks and window system fails catastrophically. Fragments enter space impacting a vertical witness panel at a distance of no more than 10 ft. from the window at a height greater than 2 ft. above the floor.

For more Information
More information on GSA Performance Requirements, see GSA's Facilities Standards Overview and 2003 Facilities Standards (P100).

Plastic Wrap for Buildings?

The Cleverest Building Material Around, The Sustainable Metropolis, describes SmartWrap, a thin, plastic membrane material under development for use as a complete building cladding system. Product developers James Timberlake and Stephen Kieren of KierenTimberlake Associates claim the material has the ability to change color and appearance, perform the functions of shelter and control of interior climate, and provide light and electricity. The membrane's heating, lighting, information display, and energy collection and storage capabilities can all be controlled by computer, either on- or off-site.

Finally, in an apparant hat trick, the material is claimed to be 100% recyclable.

What Really Happened To The John Hancock Tower

With the expiration of a 17-year gag order on the legal settlement surrounding the massive curtainwall failure of Boston's John Hancock Tower, forensic engineers Simpson Gumpertz & Heger can finally tell what was the source of failure that led to the replacement of over 10,000 sheets of glass.

Loadbearing Glass

Schott Corporation reports on the development of loadbearing glass cylinders used in Norman Foster & Partners' Tower Place project. The 4-meter long laminated glass cylinders are prestressed with internal steel wire cables, and are used to brace the building's stressed glass facade system.

17 - Glass and Glazing Links

This article contains external links to resources on the Web relevant to Chapter 17 Glass and Glazing.

Nathan Allan Glass Studios

Specialty and architectural glass products

PPG Technical Library

A good selection of product information, technical data, and engineering design guides for architectural glass.

Pilkington Glass

Architectural, self-cleaning, fire-resistant, structural, and other glass products

TGP

Fire-rated glass and framing systems