Need a book? Engineering books recommendations...
[SEAOC] Plywood: sinkers beat common nails?[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc(--nospam--at)seaoc.org
- Subject: [SEAOC] Plywood: sinkers beat common nails?
- From: jwarne(--nospam--at)direct.ca (jim warne)
- Date: Wed, 28 Aug 1996 09:38:36 -0700
Say it isn't so! Someone has to reassure me. I've just lectured a poor framer about the thin gun-nails he used in the shear walls, when I had asked for Common Nails in the drawing notes. It now seems that he may have been right, after all. He said (as they all do), "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..." 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. When I got home, I looked for something in my SEAOC literature to back my claims up. I was sure I'd read that thin "sinker" nails were weaker. Also, "everyone" knows that over-driving the nails spoils the shear strength. 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; and Deborah Sandercock and Robert Kazanjy, from the University of California at Irvine; built some model 3/8" plywood shear wall panels with a variety of nailing arrangements and tested them under simulated earthquake shear loading. Some had common, some had sinker (or "box") nails, and some had 20%, or 50%, or 80% of the nails driven 1/16" or more into the sheathing. Their conclusion was that...The 3/8" thick plywood panels with box nails were as strong or stronger than those built with common nails...overdriving the nails adversely affects the strength, but not below that of the comparable common nail panels... the box nail panels have a greater residual integrity after the test than common nail panels. The rationalle presented in the report, to explain the poorer performance of common nails, is that the box nails they used had larger diameter heads. The common nails they used also had a conical shaped head (the underside was tapered, something like a countersunk screw's head shape). That was why, they surmised, that the common nails pulled through the plywood more often than the box nails. The box nails usually pulled only part way out, and dissipated more energy. I think I was still right about the nailing I rejected on my project, because the Senco gun nails "my" framer used were even thinner, and had smaller heads. Those heads also had "cookie bites" out of one edge, to fit tighter in the nail strip. These sharp edges enhanced the tendency of the nails to cut through the top veneer. I also don't think I've seen conical heads on our common nails. I think they all have a flat underside. I believe they would resist pull-out better than the nails used in the UCLA Irvine test. Here are my two questions: 1. Are there any other reports of testing of plywood shear wall or diaphragm panels, comparing common nail performance with thinner "sinker" or "box" nails? 2. What evidence is there that "overdriving", that is, driving nail heads into the plywood deep enough to cut the top veneer, weakens shear resistance? I had a few more questions, like, how to get contractors to believe we REALLY MEAN the notes on our drawings; and how to get them to treat me with respect; but I'll save those for another time. Jim Warne ...
- Prev by Subject: [SEAOC] Plywood Shear Walls on Metal Studs and lightweight metal roof trusses
- Next by Subject: [SEAOC] Plywood: sinkers beat common nails?
- Previous by thread: [SEAOC] Re: [SEAOC] Help!!
- Next by thread: [SEAOC] Plywood: sinkers beat common nails?