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Re: 3X Plates and Washers on Intermediate Anchors

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Joe, were you attributing the plate splitting failure to the oversized anchor bolt holes?  I've always wondered about the effect of large holes, since there's no way we're going to have snug holes in this situation, even with pre-installed bottom plates (mud sills).  So there's going to be some sliding, unless friction prevents it.  And with the vertical component (not to mention uplift) there's not likely to be much effective friction.

I've always believed that the plate splitting was due to the shear wall plywood wrenching the outer edge of the plate upward, splitting it in cross-grain tension.  I understood that the purpose of the code requirements for larger bearing plates on anchor bolts, and thicker bottom plates, was intended to counteract that splitting. 

After the Loma Prieta eq. I saw an obviously new two-story house that had rolled down to the bottom of the gully behind it (up in the Santa Cruz mountains, near the epicenter), leaving pieces of the bottom plates attached to the intact foundation.  I don't recall seeing any sign of hold-downs.

Ralph Hueston Kratz, S.E.
Richmond CA USA

In a message dated 3/2/06 10:39:17 AM, Jnapd(--nospam--at)aol.com writes:

Holes around sill plates were usually 3/4 -1" while using 1/2" anchor bolts.  This was confirmed after Northridge during site visits by several people..............so new City of LA interim memo.....now code.
 
Also at several apartment projects I and others investigated in the San Fernando Valley found sill plates split lengthwise along the AB line.