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Blast-resistant window systems essential for security, says Weidlinger

Over the past decade, all U.S. embassies and many of the federal courthouses designed by major architectural firms follow anti-terrorist guidelines developed, in part, by Weidlinger Associates Consulting Engineers of New York. The company has also worked for the governments of Germany, Italy, Portugal and Saudi Arabia, as well as private corporations such as Chevron Oil Company and Electricité de France.

According to Weidlinger principal, Matthys P. Levy: "Security and protection can and should be incorporated into buildings to act as a passive, non-intrusive shield to random terrorism." Another specialist with the firm, Peter DiMaggio, advocates blast-resistant glass as an important way to protect buildings against bomb blasts, particularly the 'collateral damage' caused by broken windows. Glass manufacturers and structural engineers are testing not only new glass interlayers but also new window systems, including mullions, frames and anchors. New anchor systems, new, thinner laminates and blast resistant curtain walls will soon be on the commercial market, according to DiMaggio.

He told LGN: "The latest window muntin system, developed by the U.S. Department of State (DOS) Bureau of Diplomatic Security, with input from other parties including Weidlinger and DuPont, attempts to make use of a variety of ductile energy-absorbing mechanisms to resist blast loads. The glazing itself is a multi-laminated system comprised of several layers of annealed glass and a tough durable interlayer of DuPont SentryGlas® ionoplast that allows the glass to deform significantly prior to failure. This glazing system is backed up by vertical and horizontal steel tubes, or muntins, which support the glazing unit and prevent it from being propelled into the occupied spaces. The entire system is designed to sustain large inelastic deformations while resisting the blast loading with the intention of providing a safe, cost-effective design solution to the problem of terrorist attacks."

DiMaggio continued: "SentryGlas® seems to be an excellent choice for use in laminated blast resistant glazing due to its ability to sustain significant levels of deformation prior to failure. This type of performance allows for the use of relatively thin glazing and a less expensive glazing unit than would otherwise be required.

"We believe that this muntin system is an optimal method for incorporating the ionoplast interlayer into blast-resistant windows. By installing muntins behind glazing containing SentryGlas®, the ability of the window system to fail by 'pulling out' of the window bite is prohibited. This design will allow for the large deformations associated with a properly designed blast-resistant window with SentryGlas®.

"This excellent blast resistant window system is at its most effective in a structure utilizing very strong façade walls. The reactions imparted to the façade by the muntins tend to be fairly large and must be properly resisted if the windows are to perform as desired."

Established in 1949, Weidlinger Associates has received an Honor Award from the AIA for being "pioneering engineers and structural designers whose innovative solutions and long-standing commitment to research and computer applications have revolutionized building in America."