Cantrilever Diaphragm Limitations
Cantrilever Diaphragm Limitations
(OP)
In older IBC and UBC codes, there used to be restrictions on the size of a wood horizontal diaphragm that could be cantilevered from a structure. Very applicable to deck or roof canopy construction where it is attached to a much larger structure with shear walls.
I cannot find any such limitation in the 2009 IBC, area or otherwise, other than the allusion in Figures 2308.12.6(3) and (4) where the 6 foot dimension is given. Other than that Sections 2308.1.1 and 2308.4 seem to say if it is engineered, it is OK.
Any other insight?
I cannot find any such limitation in the 2009 IBC, area or otherwise, other than the allusion in Figures 2308.12.6(3) and (4) where the 6 foot dimension is given. Other than that Sections 2308.1.1 and 2308.4 seem to say if it is engineered, it is OK.
Any other insight?
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com






RE: Cantrilever Diaphragm Limitations
I think that it is found in the Special Design Provisions for Wind & Seismic section of the NDS (published by the American Wood Council). The limitation for cantilevered diaphragms, which must be rigid for open front buildings, shall be permitted to cantilever past the outermost supporting shearwall a distance, Lc, of not more than 25' or two thirds of the diaphragm width W, whichever is smaller. It is shown in Figure 4.2.5.2 of my version of the NDS.
I hope that this helps.
RE: Cantrilever Diaphragm Limitations
I just woindered if the thinking has changed here, or am I missing something?
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Cantrilever Diaphragm Limitations
But, if you go to www.awc.org/pdf/2008 WindSeismic.pdf you can view a read only version of the SDPWS for free.
RE: Cantrilever Diaphragm Limitations
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Cantrilever Diaphragm Limitations
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Cantrilever Diaphragm Limitations
Thanks for the correction. I never could type worth a damn.
RE: Cantrilever Diaphragm Limitations
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com