Deflection Limits Proposals Fail During ICC Hearings

May 7th, 2012 by DWM Magazine

Two International Building Code (IBC) code change proposals, S175 – 12, submitted by the Glazing Industry Code Committee, and S339–12 by the American Architectural Manufacturers Association (AAMA), were disapproved over the weekend during the International Code Council hearings, which are taking place in Dallas. Both proposals, which were essentially the same, were also supported by the Aluminum Extruders Council.

According to the proposal, which concerned exterior doors and windows, “products in Risk Category I and II buildings tested and labeled as conforming to AAMA/WDMA/CSA 101/I.S.2/A440 shall not be subject to the requirements of Sections 2403.2 and 2403.3 provided one of the following is met:

• The required design pressure for the fenestration product does not exceed 60 psf or

• All glass in the fenestration product is tempered or laminated.

The GICC proposal states points out that both Chapter 24 and ASTM E1300 require glazing to be firmly supported to prevent breakage under the design load by establishing maximum framing deflection limits. “The glass strength calculations in ASTM E1300 use this as a basis to establish a probability of glass breakage less than 8 in 1000. However, Section 1710.5.1 currently exempts certain residential and light commercial products from this requirement if they are labeled to the AAMA/WDMA/CSA 101/I.S.2/A440 standard. While this may be appropriate when these products are used in applications with lower design loads and/or lower risk building types, allowing this exception for all product types in all occupancies is far too broad.”

As the proposal states, it sought to “correct this overbreadth by ensuring that products used in higher risk situations be firmly supported and meet the frame deflection limit to restore an appropriate safety margin consistent with ASTM E1300.” Specifically, it proposed limiting the exception to risk category I and II buildings, and added that products used in higher risk category buildings would meet the Chapter 24 requirement for firmly supported glazing. It also maintained the exception for lower design pressures less than 60 psf, and also where tempered or laminated glass is used as an alternative method.

 

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