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Re: OOP Wall Anchorage - min. size of wood framing member

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If you are refering to a ledger type connection then the recommendation is to use a minimum 3x member regardless of whether it still specifically exists in the code or not (I have not checked the new code to see). The depth of the top flange of the hanger generally governs the ability to use a 2x or 3x min ledger connector. Originally, the concern was in cross-grain tension failures caused by top flange hangers that pull against the top of a wood ledger creating a bending failure parallel to grain - but this was generally a concern where the mass of the wall exceeded a wood stud wall such as in tilt-up, masonry or concrete buildings with wood ledgered walls. Still, the problem was not resolved by simply using a 3x minimum ledger, but by making sure that the framing was concentrically connected to the masonry or concrete wall directly through the purlin, or sub-purlin and not using the ledger for a tension connection. 
If you are only concerned with wood framing on wood stud walls, I would still recommend a minimum 3x connection because of the available length of embedment of the 10d or 16d nailing. You can order a Simpson N10 nail that is 1-1/2" long but conventional nails are somewhat longer and withdrawl on the nail is related to depth of embedment which means that you will take a loss if using a shorter embedment length of the nails.
So to answer you directly, I am not sure what the code requires since I have not gotten that far in the new code, but I would still recommend a 3x or 4x ledger for all connections of wood against wood and especially so if you use a top flange hanger.
 
Dennis
 
Dennis S. Wish, PE
California Professional Engineer
Structural Engineering Consultant


----- Original Message ----
From: "sutej(--nospam--at)ca.rr.com" <sutej(--nospam--at)ca.rr.com>
To: seaint(--nospam--at)seaint.org
Sent: Monday, November 26, 2007 12:45:52 PM
Subject: OOP Wall Anchorage - min. size of wood framing member

1997 UBC Section 1633.2.8.1 required the wood framing member of the wall anchorage assembly in seismic zones 3 and 4 to have a minimum net thickness of 2 1/2".  I do not find this requirement in the 2006 IBC, 2007 CBC, nor in ASCE7-05.  Is this no longer required and, therefore, a 2x member could be used?



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