||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 wasnt 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 Conraths 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 wont 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
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