The Eastern United States Withstood Wind Speeds Escalating to 90 mph

The Eastern United States withstood wind speeds escalating to 90 mph from Hurricane Sandy's destructive presence, according to the National Weather Service. The wake of the recent devastation could serve as a reminder to glazing contractors of the importance of complying with impact glazing codes in preparation for the uncontrollable. ASTM standards, for example, are crucial to many aspects of natural disaster preparation. ASTM E06.51, an E06 subcommittee on performance of windows, doors, skylights and curtainwalls, has developed standards that can test the performance of windows during hurricanes and other severe weather-related situations. These standards include ASTM E1886 and ASTM E1996, both of which concern the performance of exterior windows, curtainwalls, doors and impact protective systems during hurricanes. In order for glass to withstand massive increments of wind pressure there needs to be a sufficient glass bite or penetration of the glass into the glazing pocket to support the large deflections, according to Rick De La Guardia, president of DLG Engineering Inc. Sustaining high winds, however, are not the only concern. "I would venture to guess that most glazing products are designed to sustain hurricane force winds, in areas where required (hurricane-prone regions), but very few are designed to sustain windborne debris, " says De La Guardia. "The real question, is, are these products being installed properly? I suspect that, similar to what happened in Florida after Hurricane Andrew, all the municipalities affected by Hurricane Sandy will be performing a thorough review of their building codes, installation and inspection procedures. " De La Guardia goes on to define the difference between wind speed and windload. He points out that wind speed is just one factor that determines the windload, which is the actual pressure that will be imposed on the glass. Another factor is the height of the glazing product above ground level. "For example, using the same wind speed, say 75 mph (hurricane-strength wind speed), the windload applied to the glass will be greater on a glazing product installed at 30 feet of elevation than on a glazing product installed at 15 feet of elevation, " says De La Guardia. "Let's focus on the windload, say 60 pounds per square foot (psf). Glass is very strong under uniform load (wind alone); the issues to consider for such high pressures are the deflection of the glass and the building substrate. " As for deflection, De La Guardia says the glass itself may not have a problem sustaining the loads, but the deflections could be such that it can pop out of the frame without a proper glass bite. With respect to glazing products, the glass and deflection may not be an issue, but the entire glazing product has the potential to be ripped out of the building due to poor installation. Source: usgnn