New Methodology for Blast-Resistant Glass is Designed to Reduce Flying Shards From Explosions

Flying glass from bomb explosions in buildings is a palpable threat in 2002. To reduce glass-related injuries, a task group of ASTM glazing specialists are working with industry to develop standards for blast-resistant window glazing.

The task group is working in ASTM Committee F12 on Security Systems and Equipment, whose scope includes the security of property and life. The committee chairman, Scott Norville, P.E., Ph.D., and its membership secretary, Ed Conrath, P.E., are drafting two standards that will be reviewed by the committee. Norville, who is drafting a standard design method for blast-resistant glazing, is professor of Civil Engineering and director of the Glass Research and Testing Laboratory at Texas Tech University, Lubbock. Conrath, who is revising ASTM F 1642, Standard Test Method for Glazing and Glazing Systems Subject to Air Blast Loadings, is a structural engineer in the Protective Design Center of the U.S. Army Corps of Engineers, Omaha, Neb.

They described why the new methods are needed. “A blast-resistant glaze exists that can be placed on windows in a commercial building that reduces hazard from glass fragmentation,” said Conrath, who has been working with Norville on blast-resistant glazing problems since the middle ’80s. But prior methodology addressed the load force on windows from accidental explosion, not exploding bombs, said Norville: “The point back then wasn’t so much terrorists as it was accidental explosions.”

Norville wrote several research papers on the Oklahoma City bombing, as well on as glass-related injuries. “The problem is, when the bomb goes off, glass designed to resist wind loads with no consideration beyond that, then tends to produce shards that injure and hurt people,” he said.

Committee F12 will propose both design and test standards for ballot within ASTM. The committee includes representatives from engineering firms that specialize in blast-resistant glazing and other glass specialists. With their input, Norville is drafting a method for the design of blast-resistant laminated glass. The method will be based on data from his and Conrath’s paper, “Considerations for Blast-Resistant Glazing Design” that appeared in the Journal of Architectural Engineering (ASCE, September 2001).

The methodology uses a relationship between shard size and equivalent wind loading on laminated glass. A structural sealant is applied to the laminated glass and frame. Like a car windshield, the glass can shatter but won’t throw off pieces. “The frame holds laminated glass in place and the plastic laminate on the interior of the glass holds glass shards to it and holds it together,” explained Norville.

Conrath is drafting a revision of ASTM F 1642, Standard Test Method for Glazing and Glazing Systems Subject to Air Blast Loadings. The revision will explain a blast or shocktube test where users record data and obtain results needed to meet safety requirements. The pass-fail criteria in the existing test method will change. Designers can use the new method to test blast-resistant glazing against a design-threat bomb.

Individuals are welcomed to participate in the development of these standards. For further technical information, contact Professor Scott Norville, Ph.D., Department of Civil Engineering, Texas Tech University, Lubbock, Texas (phone: 806/742-1930), or Edward J. Conrath, Protective Design Center, U.S. Army Corps of Engineers, Omaha, Neb. (phone: 402/221-3152). Committee F12 meets April 16-17 in Pittsburgh, Pa. For meeting or membership details, contact Jim Olshefsky, manager, ASTM technical committees (phone: 610/832-9714). //

Copyright 2002, ASTM