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[SEAOC] Re: [SEAOC] Re: [SEAOC] Plywood: sinkers beat common nails?

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Some additional comments:

1)  APA Research Report 105 on plywood shear wall tests (monotonic) had some matched test specimens in which plywood siding was fastened with common and galvanized (hot-dipped or tumbled) box nails.  The specimens with box nails had equivalent maximum shear strength as those fastened with common nails.  However, because of the thinner nail shank of box nails, slightly more displacement was recorded with the box nailed specimens than with the common nailed specimens.  That was the basis for the UBC shear wall tables which permit common or galvanized box nails.  APA doesn't consider that galvanized nails means electro-galvanized nails, until proven otherwise.  Electro-galvanized nails shouldn't be used for siding installation as a general rule, because of lower corrosion resistance.  There are some electro-galvanized or mechanically-plated nails on the market that have a yellow chromate coating over the galvanizing, therefore providing apparently adequate corrosion protection.  APA Research Report 105 is now out of print, but test data is summarized in APA Research Report 154 (except no data on wall displacement is reported - only maximum shear strength is reported).

2) Ficcadenti et. al. cyclic load testing on shear walls has been criticized by some for reasons noted by DW.  Certainly more testing is needed to confirm the observations from these tests. The test method was different than advocated by the SEAOSC committee (tests were done more than a year before the SEAOSC test method was finalized). The load-displacement protocol in cyclic load testing may have an influence on the results obtained.  Fastener load-slip tests are needed to confirm or modify the findings.  The established design values for nails (UBC, NDS) are based more on slip than on maximum shear load capacity, whereas in shear walls and diaphragms, maximum shear load capacity is also a consideration, along with displacement.  As refined methods for testing and analysis continue to be developed, these issues will be addressed.  This is a state-of-the-art process; don't be surprised if new data modifies some of the time-honored assumptions.

3) One nail manufacturer told me that the nail head size in Fed. Spec. FF-N-105 is too large, and nail forming processes to produce such a nail head would result a thin head that could easily "pop off" the shank.  Therefore, nail manufacturers (especially for pneumatically-driven nails) often use a smaller diameter but thicker nail head.  Full-size round-head pneumatically-driven nails are available from several sources. ISANTA (NER-272) has sponsored research on the effect of nail head configuration (full size vs. clipped head) and other aspects of nail size, as it relates to pull-through resistance.  In Ficcadenti's research, it was reasoned that the smaller shank diameter provided more net area under the head of the nail, thus improving the pull-through resistance of the nail as compared to common nails with a larger shank diameter.  This observation seems reasonable but needs further study; the nail size and panel thickness also have a bearing on this characteristic.

John Rose/APA, Tacoma, WA 

____
>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
>re-nail. 
>
>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.
>
>Sincerely,
>Dennis S. Wish PE
><html><head></head><BODY bgcolor="#FFFFFF"><p><font size=2 color="#000000" face="Arial">My comments are broken down in response to your letter:<br>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.<br>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.<br><b><u>Your Contractor wrote:<br></u></b><font size=2>&quot;Everyone uses gun driven nails...you can't pull<br>these suckers out...they're stronger than common nails...you can't avoid<br>over-driving, 'cause the wood is uneven...&quot;<font size=2><br>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&quot; 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 &quot;over-drilling&quot;.<br><br><font size=2><b><i><u>Well, of course, I asserted my authority. &nbsp;By towering up to my full 5'-6&quot;<br>height, and raising my voice to &quot;shrill&quot;, I finally got him to agree to<br>re-nail. <br></b><br></u></i>The bigger they are...... Well you know the rest. Stick to your better engineering judgment.<br><br><b><i><u>There's a paper from the '95 SEAOC convention that says the contractor is<br>right. Seb Ficcadenti and Thomas Castle, principals in a consulting firm;<br></b><font size=2><br></u></i>There has been a follow-up to Ficcadenti's work. The opinions of other engineers that have reviewed the work are:<br>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.<br>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).<br>3. Ficcadenti was really attempting to justify prior use of sinkers to limit his liability for designs that did not meet current code criteria. <br><br>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. <br>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.<br><br>Sincerely,<br>Dennis S. Wish PE<br><i><u><br></p>
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