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Re: 3X Plates and Washers on Intermediate Anchors

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Yes I would agree with those results in a direct shear test (BTDT) but what were the loads involved?  I've done test were shot pins generated ~3000 lbf/pin, how likely will shot pins see this load? not very

I'd be willing to bet that the ultimate loads in the direct shear test you mention were MUCH higher than the typical SLS that a shear wall can deliver to a sill (esp if sturdy HD is used)

The direct shear tests can be interesting for seeing how CIP anchors & chemical anchors perform on a relative basis................but IMO the sills will never see loads anywhere near that high, so it it an unrealistic failure mode.

cheers
Bob

On 3/3/06, coengineer(--nospam--at)aol.com <coengineer(--nospam--at)aol.com > wrote:
 I have seen testing where a shear load was applied directly to a sill plate bolted to the concrete using plate washers v. standard cut washers.  In the case of the cut washers, the anchors bent over and the washer embeded into the plate at pretty low loads.  In the case of the plate washer, the load was distributed over the area of the larger washer and did not embed itself into the wood.  This resulted in the plate taking a higher shear load and less deformation.
 
Howard Silverman, PE
Covert Operations/USP Structural Connectors
hsilverman(--nospam--at)uspconnectors.com
 
-----Original Message-----
From: Bill Allen < T.W.Allen(--nospam--at)cox.net>
To: seaint(--nospam--at)seaint.org
Sent: Thu, 2 Mar 2006 09:01:46 -0800
Subject: 3X Plates and Washers on Intermediate Anchors

So, as I understand it, the requirements for 3X sill plates for shear walls with Fv > 350 PLF (CBC Table 23-II-I-1, footnote 3) and square plate washers (CBC Section 1806.6.1) on intermediate anchors are a result of observations that, when wood shear walls lift (due to lack of restraint at the hold downs), the sill plate will tend to split. The square washer distributes the load better and the thicker 3X sill plate will provide a better section to resist flexure. O.K., I understand that.
 
Maybe these are two separate issues.
 
What about another solution? What if the nuts (and washers) were left off entirely? It certainly seems to me that would eliminate the requirement for the square plate washers (if none were required in the first place). I?m not sure if this would be a remedy for the 3X sill plates. I understand the requirement for 3X members at abutting panel edges to reduce splitting, but I?m guessing the 3X sill plate requirement is to reduce flexural failure. I?m sure I will be corrected if I?m mistaken.
 
All code references are to the 2001 CBC (sorry).
 
Just a thought. Comments are welcome.
 
T. William (Bill) Allen, S.E.
Consulting Structural Engineers
 
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