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Re: 3x min for conc/mas wall anch to flex diaph?

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I'm sure the gang-nail truss people got that one ex-nayed...

The reason it's in the code was for 2x4 and 2x6's mainly. Nailed from above (roof nailing) and the side caused splitting.

I was okay using A35's for 2x10 and 2x12's on a masonry wall top where the rafters sit on a nailer, but even sometimes on those I would sister on a block to get (2) 2x's if they were at 24" o.c. Most plan checkers were okay with this when I explained the intent of the 3x provision.

For HD's, PHD's and whatever the new simpson hold-down is called, those are tabulated in DBL 2x's min, so I could easily and rightfully see a plan checker dis-allowing those if used on a single 2x (maybe the HD if someone did the bolt-calc).

I think clips with low forces, you're okay anchoring a 2x8 or deeper, but I would strive for 3x's and double 2x's at a minimum for anchor spacings greater than 2ft. or when using 2x6's or shallower

-gm

On Fri, Apr 11, 2008 at 1:39 PM, Gould, Diane <Diane.Gould(--nospam--at)dgs.ca.gov> wrote:

The 1997 UBC Section 1633.2.8.1 item 5 required that wood "elements of anchorage" have the strength to take 0.85 x Fanch and have a minimum net thickness of 2.5 inches.  I am at a loss to find where this requirement is included in the new code.   ASCE 7-05 Section 12.11.2 addresses anchorage of concrete & masonry walls, but the 3x min requirement seems to have been dropped. 

 

I think you would have a hard time finding hardware to fit/work with members smaller than 3x anyway and I plan to continue detailing with 3x minimum.  Just curious if anyone else had noticed this or might have some background on possible reasons for this apparent omission.

 

Regards, 

 

 

Diane C. Gould, S.E.

Senior Structural Engineer

DGS-RESD-PSB

Design Services Section

707 Third Street, Suite 4-105

West Sacramento, CA 95605

(916) 375-4219 phone

(916) 375-4916 fax

diane.gould(--nospam--at)dgs.ca.gov




--
-gm