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Cantilever Flexible Diaphragms

Cantilever Flexible Diaphragms

Cantilever Flexible Diaphragms

(OP)
What are your limitations when cantilevering a flexible diaphragms?  Theoretically, are you even supposed to do this at all?

Obviously, a little cantilever will be fine, but how much can you push it??

RE: Cantilever Flexible Diaphragms

What is your flexible diaphragm that you are trying to cantilever?  

RE: Cantilever Flexible Diaphragms

At one time, wood framed cantilevered horizontal diaphragms were limited by code to a 25 foot cantilever.  Sorry I don't have time to look it up right now.

RE: Cantilever Flexible Diaphragms

I think it is defined in the IBC- I do remember the limit as 25 feet so long as your diaphragm ratio is 1:1(I think, don't have code in front of me)  Also, cant. wood diaphragms are not allowed to resist lateral forces due to conc. or masonry.

RE: Cantilever Flexible Diaphragms

I recall a backspan limit from somewhere as well - i think the cantilever was limited to a third of the backspan.  

RE: Cantilever Flexible Diaphragms

I recall a 20 X 20 limitation.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Cantilever Flexible Diaphragms

The appropriate section in the 2006 IBC was 2305.2.5 Rigid Diaphragms.  This section has been removed from the 2009 code.  You now have to look in the AF&PA SDPWS section 4.2.5.2.  The limits are the greater of 25' or 2/3 x width.  

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