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[SEAOC] Re: [SEAOC] Plywood: sinkers beat common nails?
- To: <seaoc(--nospam--at)power.net>
- Subject: [SEAOC] Re: [SEAOC] Plywood: sinkers beat common nails?
- From: "DW" <wish(--nospam--at)cyberg8t.com>
- Date: Wed, 28 Aug 1996 12:45:41 -0700
My comments are broken down in response to your letter:
Values for Common verses Sinker when used with shear walls is empirical - tested values. The sinker did not do as well in shear as the Common nail. This is obviously due to the increased shank diameter of the Common Nail.
Your contractor may be correct about pull-out since the power driven nail has the advantage of an adhesive built into the plastic ribbon binding the nails. An APA representative once told me that the friction of the nail when delivered into the wood heats the adhesive holding it to the ribbon which then coats the nail and sets after installation. The problem is not with pull-out but with shear.
Your Contractor wrote:
"Everyone uses gun driven nails...you can't pull
these suckers out...they're stronger than common nails...you can't avoid
over-driving, 'cause the wood is uneven..."
The Common nail has a wider head area as well as a thicker shank which provides more area in contact with the plywood - thus minimizing the pull-through of the head from the plywood panel and increasing the shanks shear capacity. When 3/8" panels were tested for common verses sinkers, there was no indication that the nail was over-driven - crushing the plys of the panel. This would reduce the panel's capacity below the rated code value - which destroys his comments about inherent over "over-drilling".
Well, of course, I asserted my authority. By towering up to my full 5'-6"
height, and raising my voice to "shrill", I finally got him to agree to
The bigger they are...... Well you know the rest. Stick to your better engineering judgment.
There's a paper from the '95 SEAOC convention that says the contractor is
right. Seb Ficcadenti and Thomas Castle, principals in a consulting firm;
There has been a follow-up to Ficcadenti's work. The opinions of other engineers that have reviewed the work are:
1. SEAOC should never have published this document without prior review and approval of the relevant committee (Code Committee). The report was submitted late and had not gone through the proper cycle for review and comments. Therefore, it was published sight unseen.
2. The testing was not done under controlled conditions and the methods of testing were questionable. There had not been a procedure established for the test as is generally required before doing testing. This is especially true for the section of the report that deals with the placement of blocking outside of the plane of the double top plate (to be used simply as a stucco mold rather than a shear transfer).
3. Ficcadenti was really attempting to justify prior use of sinkers to limit his liability for designs that did not meet current code criteria.
I have read the same research article in the SEAOC Procedures and was drawn to this report - questioning the adequacy of the code. I contacted a few other engineers who are active with SEAOSC and obtained the above opinions.
Finally, as I have stated to other engineers and building officials (and have had them state to me), the Ficcadenti report is not valid until accepted and the code revised. Until then, I would not consider the report to be anything other than an interesting article.
Dennis S. Wish PE