Glass Pros Discuss Hurricane Glazing Changes in 2012 IBC
June 27, 2011
Among the changes incorporated into the updated International Building Code (IBC) that will impact the glass industry is a change to the American Society of Civil Engineers (ASCE) standard 7-10, Minimum Design Loads of Buildings and Other Structures that is referenced in the IBC. The 2012 IBC was released in June and although not likely to be immediately adopted by states and localities, it has been a source of discussion in the industry of late.
Michael Stremmel, P.E., senior project engineer for Architectural Testing Inc. in York, Pa., says, "The method that is used within ASCE 7-10 to determine design pressure was changed when compared to ASCE 7-05." Stremmel says in the grand scheme this is a small change, but even small change may mean adopting something new. "The end result of this change is minor when comparing the design pressure when calculated with ASCE 7-10 when compared with ASCE 7-05, but there will most certainly be confusion about proper interpretation of the changes," he says.
Alan Carr, S.E., Code and Standards, International Code Council (ICC) in Bellevue, Wash., explains.
"The good news is the technical requirements in the code under protective openings, specifically glazed openings, really haven't undergone any changes in this cycle. But where there's sort of a hidden change in there is that the new wind speed maps have been revised based on a new procedure that was promoted in the latest edition of the ASCE 7 load standard. What's happening is the new IBC will now have, instead of a single wind speed map, three maps. So the map wind speeds that you get vary based on what's now called the 'risk category,' what used to be the occupancy category of the building," he says.
"How that impacts opening protection is that the definition of wind-borne debris region has been updated to reflect the new mapping wind speed. ... By having the different maps based on risk category, a wind contour that defines the wind-borne debris location might be in a different location from where it was previously, particularly if you're in the highest risk category-'essential facilities,'" Carr continues.
Carr aims to put manufacturers and installers at ease by adding, "There could be some confusion surrounding this in the sense that the [ASTM standard for missile tests] was written for the old wind measure and hasn't been updated to the new wind speed measure, but the IBC contains a section under the opening protection section that says 'when you're using the ASTM E standard for missile impact you have to reword it so you use these wind speeds.' And ASCE 7 has a user note that says 'the wind zones that are specified in ASTM E1996 for use in determining the appropriate missile size for the impact test have to be adjusted for use with the wind speeds of ASCE 7-10 and the corresponding wind-borne debris regions.' Then it refers you to the commentary to see what the adjustments need to be."
Click here for a related story on the start of hurricane season.
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