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RE: Masonry on wood

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I cannot help you with the IBC sections at the moment (I have yet to be a good boy and acquire a 2006 IBC for myself), but I can comment on the deflection stuff the MSC.
 
Keep in mind that the L/600 or 0.3" limit in section 1.10 is strictly for elements (could be a steel beam, concrete beam, masrony beam, or something else) that support unreinforced masonry.  The idea is that since the masonry above is unreinforced, it has no rebar to help hold together cracks.  As such, an element that supports that masonry that deflects excessively could result in too much cracking of the unreinforced masonry, which then could create structural as well as just performance (i.e. weather sealant) issues.
 
Beyond that, the MSJC does not really address deflection issues.  You would have to either resort of deflection limits in ASCE 7/IBC loading sections or other information.  As a result, you will generally see differing recommendations for deflections of walls.  There are some that recommend H/600, but I have seen some recommendations as high as H/1200.
 
Regards,
 
Scott
Adrian, MI
-----Original Message-----
From: Gordon Goodell [mailto:GordonGoodell(--nospam--at)harmonydesigninc.com]
Sent: Tuesday, August 19, 2008 5:43 PM
To: seaint(--nospam--at)seaint.org
Subject: Masonry on wood

I suppose I should flip through the IBC and read everything with a heavy black line beside the week the new code comes out.  As it is, though, I find these things gradually (and often with the help of this listthanks).

My understanding of IBC 2104.1.6 and the new IBC 2304.12 (which now seem to contradict each other for the most part) is that a lot of stuff that was not previously allowed now is, if you use a duration factor of 0.9 for wood supporting members.  For example, you could have a hollow-core concrete floor in a light-framed building.  Interesting.  Am I reading this right?  Why in the masonry section do they not get more explicit with deflection limits, the way they do in the glazing section, if this is so?  It defaults to ACI 530, 1.10, which I take to mean DL+LL defl < l/600 or 0.3 as a max, but otherwise reduced to the actual calculated deflection of the masonry above.


thanks,

Gordon Goodell


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