Building and Construction - Shear Walls: common vs. galvanized box nails

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Shear Walls: common vs. galvanized box nails

Wayne Whitney

2006-04-15, 3:21 pm

Hello,

I'm looking at the APA table of shear wall strength for various
configurations, as printed in their publication X-305, "Introduction
to Lateral Design." I notice that for nail size the table says
"common or galvanized box".

Now my understanding is that in such a plywood shear wall assembly,
the limiting strength factor is the nailing. And that the shear
strength of a nailed plywood to lumber connection is a function of the
shank diameter of the nail. So why does this table not distinguish
between bright common and galvanized box nails? Box nails are smaller
in shank diameter (e.g. 8d common is 0.134" and 8d box is 0.120"); is
the galvanization really enough to make up the difference?

Thanks, Wayne

Bobk207

2006-04-16, 12:21 am

Wayne Whitney wrote:
> Hello,
>
> I'm looking at the APA table of shear wall strength for various
> configurations, as printed in their publication X-305, "Introduction
> to Lateral Design." I notice that for nail size the table says
> "common or galvanized box".
>
> Now my understanding is that in such a plywood shear wall assembly,
> the limiting strength factor is the nailing. And that the shear
> strength of a nailed plywood to lumber connection is a function of the
> shank diameter of the nail. So why does this table not distinguish
> between bright common and galvanized box nails? Box nails are smaller
> in shank diameter (e.g. 8d common is 0.134" and 8d box is 0.120"); is
> the galvanization really enough to make up the difference?
>
> Thanks, Wayne

Wayne-

You are just too smart for this whole business!

> strength of a nailed plywood to lumber connection is a function of the
> shank diameter of the nail.<<

as as first approximation, but plywood thickness & nail head diameter
& thinkness also figure in.

WAY back when, when the tables were developed for some reason they
(code writers) gave common nails & hot dipped galv box the nails the
same values.

I really strecthing my memory but I think someone at APA told me (about
10 years ago) that the code nail values were based on nail slip tests
nailing 1x onto a 2x (but don't quote me)

Anyway I suggest you go to the APA & look at their tech papers
section

they actually have a paper comparing exacting what you're asking about

Technical Topics:

Shear Wall Test Results Comparing 8d Common and 8d Box Nails

they have tons of other tech info, just register & you can download
the PDF files
APA is an amazing resource

take a look at Report 158 Shear Walls Under Cyclic (Reversed) Loading

it (report 158) was some of the first cyclic work done by APA, they
have done lots since.

I don't remember the results of their tests (8d Common and 8d Box
Nails) but back in 1997 in the SEAOC Anniula Meeting Proceedings we had
paper publsihed comparing similar nail situations.

I doublt I have an electronic copy any more but recollection was that
the acutal preformace didn't vary all that much. I thought that the HD
galv box would perform best, it did not. Actually I think the 8d 8d
gun box close. The HD galv box exhibited somewhat earlier failure than
the common or the electro galv. The commons we used were hand driven
commons & they had thick nasty heads & the shearwalls had 3/8". Which
is so thin that the thick heads can punch through the face ply.

As Bob M. will agree, spec'ing nail size by penny size (d) is a good
way to NOT get what you want.............any more it's got the be shank
dia & length

for example 8d nails

common .131
HD galv .120
gun box nail .113

A further problem with modern gun driven nails is the head diameter is
dictated by the requirements of the gun mfr!

Such that from 8d sinker all the way to 16d "shorts", the heads are all
the same diameter.

as the nail shank gets bigger in diameter & longer the holding capacity
in the framing member becomes large enough such that the nail head will
be more likely to pull throuhg the plywood in a seismic event.
Additionally there is only so much trauma the framing members can
handle (shearwall nail size & spacing)

10d common is .148 x 3"
10d plywood short is .148 x 2 1/2"?
10d box (gun) is 131 x 3"
8d commom is .131 x 2 1/2" (diffrent form 10d box by length)
8d box (gun) is .113 x 2 3/8"

these diamters might differ slightly from what info is listed on the
web but to my best recollection these are the diameters that one gets
when one buys nails

Bulk nails (nails to be driven by hand, non-collated) might have
slightly different dimensions but they are of little consequence since
nearly all shearwall nailing is done by gun nailing.

so unless the engineer really nails down (ha, ha, ha) the nail spec, he
could get just about anything in nail diameter

Personally I like the 8d common, not too big to traumatize the wood
(esp important w/ old dry wood) & not too small in diameter & you still
get a decent head to shank diameter ratio.

Actuallly .131", .120" and all the way down to .113 make pretty
decent shearwall nails. I'm not a huge fan of the .148 nail, shank is
a little big (esp if nail spacing is tight & the tiimber is old) and
the gun head is no bigger than an 8d

cheers
Bob

Wayne Whitney

2006-04-16, 3:21 am

On 2006-04-16, Bobk207 <rkazanjy@gmail.com> wrote:

> 10d box is 0.131 x 3"
> 8d common is 0.131 x 2 1/2" (different from 10d box by length)

So the APA tables give a shear wall assembly using 10d box nails a
higher rating than one using 8d common nails. Does the extra 1/2"
embedment really make a difference? If so, it seems like 10d box is
the way to go.

Cheers, Wayne

Bobk207

2006-04-16, 1:21 pm

Wayne-

I do not know why a 10d box (.131 x 3) would give a higher value than
an 8d common (.131 x 2.5"). Both with same sheathing thickness?

Sometimes strange anomolies exist in the code tables; codes are
consensus documents that a committe must agree upon. They're not
perfect, they're the best that the could be at the time for whatever
reason.

For example (not sure f still true) 3/8 ply gives the best code
strength value/$. That is, the stregth increase allowed by code from
3/8 to 1/2 is not relative to the $ incresae from 3/8 to
1/2...................and everyone wonders ........."why doesn everyone
use 3/8 instead of 1/2 ?".

I don't that extra 1/2" nail embed would make much difference for a
..131 nail.

Maybe Bob M has an idea about

I DID test 10d plywood shorts (.148 x 2.5"?) and they had a very
interesting behavior, At large forces & wall displacments the nails
slowly withdrew from the framing. So that I know that 2.5" embed for a
..148 nail with 1/2 plywood in not enough., But never saw lots of 8
commoms withdraw.

I think that dat was included in APA 158

Does the APA table callout the actual nail size (length & diameter) or
are
they stuck back on the old HD Galv box thing?

can you send me a link or copy of the APA table?

cheers
Bob

Bobk207

2006-04-16, 1:21 pm

Wayne-

I do not know why a 10d box (.131 x 3) would give a higher value than
an 8d common (.131 x 2.5"). Both with same sheathing thickness?

Sometimes strange anomolies exist in the code tables; codes are
consensus documents that a committe must agree upon. They're not
perfect, they're the best that the could be at the time for whatever
reason.

For example (not sure f still true) 3/8 ply gives the best code
strength value/$. That is, the stregth increase allowed by code from
3/8 to 1/2 is not relative to the $ incresae from 3/8 to
1/2...................and everyone wonders ........."why doesn everyone
use 3/8 instead of 1/2 ?".

I don't think that extra 1/2" nail embed would make much difference for
a .131 nail.

Maybe Bob M has an idea about why the difference in code values?

I DID test 10d plywood shorts (.148 x 2.5"?) and they had a very
interesting behavior, At large forces & wall displacments the nails
slowly withdrew from the framing. So that I know that 2.5" embed for a
..148 nail with 1/2 plywood in not enough., But never saw lots of 8d
commoms withdraw.

I think that the 10d plwood short was included in APA 158

Does the APA table callout the actual nail size (length & diameter) or
are
they stuck back on the old HD Galv box thing?

can you send me a link or copy of the APA table?

cheers
Bob

Wayne Whitney

2006-04-16, 2:21 pm

On 2006-04-16, Bobk207 <rkazanjy@gmail.com> wrote:

> Does the APA table callout the actual nail size (length & diameter)
> or are they stuck back on the old HD Galv box thing?

No, they are stuck on the "10d common or galvanized box" thing, that
is what started this thread. As for the table, it's page 13 of APA
X-305, "Introduction to Lateral Design", which Bob M. suggested. I'll
email you the pdf.

Cheers, Wayne

Bob Morrison

2006-04-17, 12:21 pm

In a previous post Wayne Whitney wrote...
> o the APA tables give a shear wall assembly using 10d box nails a
> higher rating than one using 8d common nails. Does the extra 1/2"
> embedment really make a difference? If so, it seems like 10d box is
> the way to go.
>
> Cheers, Wayne
>

Wayne:

The tables you want to pay attention to are the ones published in IBC2003.
They vary slightly from the NDS tables. Mostly in that NDS publishes
separate values for Wind and Seismic, whereas, IBC uses only the seismic
values.

Table values in both documents use the same value for "commons or
galvanized box"and are for Douglas-Fir Larch framing. Any other nail size
or wood species requires an adjustment of the table values.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

Bob Morrison

2006-04-17, 12:21 pm

In a previous post Bobk207 wrote...
> I do not know why a 10d box (.131 x 3) would give a higher value than
> an 8d common (.131 x 2.5"). Both with same sheathing thickness?
>

I don't see where you guys are getting table values for a 10d "box" nail.
The table calls for "galvanized" box nails.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

Bob Morrison

2006-04-17, 12:21 pm

In a previous post Wayne Whitney wrote...
> No, they are stuck on the "10d common or galvanized box" thing, that
> is what started this thread. As for the table, it's page 13 of APA
> X-305, "Introduction to Lateral Design", which Bob M. suggested. I'll
> email you the pdf.
>

Two things:

1. As Bob K pointed out earlier, a galvanized nail has higher withdrawal
value than a plain nail. However, this is generally not what determines
the shear capacity. Remember, the code allows you to compute the capacity
of a shear wall using principles of mechanics and published fastener
values. So if you wanted to fasten your plywood with wood pegs and use it
for a shearwall you do so. This is a somewhat extreme example, but I
think you get the idea.

2. A 10d galvanized box nail and a 10d common have approximately the same
diameter. And, yes the galvanizing has sufficient thickness to qualify.
A 10d plain box nail is smaller in diameter than an 8d common. Just add
confusion think about "sinkers" which are probably the most common job
site nail. A 16d sinker and a 10d common have the same diameter and in
the shear wall tables would have the same capacity.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

Wayne Whitney

2006-04-17, 2:21 pm

On 2006-04-17, Bob Morrison <SpamFighter@junk.com> wrote:

> I don't see where you guys are getting table values for a 10d "box" nail.
> The table calls for "galvanized" box nails.

I guess I didn't realize that the galvanization, even when hot-dipped,
is that thick. The difference in shank diameter between a 10d bright
box (0.128") and a 10d bright common (0.148") is 20 mils. I can't
find online any tables for diameters of bulk hd galvanized box
nails--the ones I do find show the same shank diameter as bright box
nails, so that must be the shank diameter before galvanization.

Anyway, in converting diameters of gun nails to penny sizes for shear
wall construction, I'll just use the diameter of bright common nails.

Thanks, Wayne

Bobk207

2006-04-17, 3:21 pm

Bob Morrison wrote:
> In a previous post Bobk207 wrote...
>
> I don't see where you guys are getting table values for a 10d "box" nail.
> The table calls for "galvanized" box nails.
>
>
> --
> Bob Morrison, PE, SE
> R L Morrison Engineering Co
> Structural & Civil Engineering
> Poulsbo WA
> bob at rlmorrisonengr dot com

Sorry about that Bob M, I was just using the info Wayne posted & I
was sloppy about not quailfying the box nails with HD galv.

Wayne, in the the tables they equate common nails & HD Galv box (not
bright box or electro galv box, only HD Galv box are equivavlent to
common; at least in the code tables.)

just to muddy the waters here are some gun nails that are HD Galv box
for use in a framing nailer

http://store.yahoo.com/bostonindustrial/hs10dhd.html

HS10DHD 3" Hot-Dipped Galv. Plastic Strip

3" Hot-Dipped Galv. Plastic Strip

Description: 3" x .120 Hot-Dipped Galv. Plastic Strip
Case Qty: 4000
Nail Size: 3" x .120 (10D)
Angle: 21=B0
Head: Full Round

Fits the following Nail Guns:
Bostich N95RHN, N88RH, N79RH
Hitachi NR83A, NR83A-2, NR90AC, NR90AC-2
Duofast CN350B, CN137, NS-350F1
SpotNail NPR90, YPR90
Senco SN60, SN65, FRAMEPRO, 602/652
Makita AN8300, AN922
Porter Cable FR350
MAX SN80, SN90
DeWalt D51844, D51845

* These are High Quality Hot Dipped Galvanized that Conform to ASTM
A153 Class D
* For use with all ACQ Pressure Treated Lumber

Wayne Whitney

2006-04-17, 4:21 pm

On 2006-04-17, Bobk207 <rkazanjy@gmail.com> wrote:

> just to muddy the waters here are some gun nails that are HD Galv box
> for use in a framing nailer

>
> HS10DHD 3" Hot-Dipped Galv. Plastic Strip
> 3" Hot-Dipped Galv. Plastic Strip
> Description: 3" x .120 Hot-Dipped Galv. Plastic Strip

So I would think that the 0.120" shank diameter is the actual
diameter, and that therefore you'd have to treat it as an 8d nail in
the shear wall table. Yes?

Cheers, Wayne

Bob Morrison

2006-04-17, 6:21 pm

In a previous post Bobk207 wrote...
> HS10DHD 3" Hot-Dipped Galv. Plastic Strip
>
> 3" Hot-Dipped Galv. Plastic Strip
>
> Description: 3" x .120 Hot-Dipped Galv. Plastic Strip
> Case Qty: 4000
> Nail Size: 3" x .120 (10D)
> Angle: 21=B0
> Head: Full Round
>

The diameter of 0.120" makes these the equivalent of a 10d sinker but
smaller than an 8d common. For the equivalent of 8d commons, one would
have to adjust the spacing by a factor of 0.120/0.131 = 0.92. If you use
hem-fir framing there is a second adjustment for species of 0.82.

My Shear Wall tables typically specify nails like this:
"0.131" x 2-1/2" (8d Common)"

I don't care what nail the framer uses as long at it meets the diameter
and length requirement. I have been asked to recalculate the nail spacing
based on a nail size that fits the gun used by the framer.

As an example, to to replace 8d @ 6" o/c in DF-L framing with the above
nails and Hem-fir: 0.92*0.82*6" o/c = 4-1/2" o/c

BTW, on an earlier topic: nail length doesn't have much effect on shear
value once the point has penetrated beyond 10 nail diameters. Refer to
the footnotes in Table 11N of NDS2001.

This can come up if you are nailing 1/2" sheathing over 2x T&G decking. I
once ran a calc using 16d x 1-1/2 "shorts", which allows full diaphragm
value with a 5-inch edge spacing. However, the diaphragm "boundary" nails
must have sufficient penetration to transfer the full diaphragm edge shear
to the boundary members (usually shear walls).

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

Wayne Whitney

2006-04-17, 6:21 pm

On 2006-04-17, Bob Morrison <SpamFighter@junk.com> wrote:

> The diameter of 0.120" makes these the equivalent of a 10d sinker but
> smaller than an 8d common. For the equivalent of 8d commons, one would
> have to adjust the spacing by a factor of 0.120/0.131 = 0.92.

Shear strength of a nail varies linearly with shank diameter, not with
shank cross-sectional area?

> BTW, on an earlier topic: nail length doesn't have much effect on shear
> value once the point has penetrated beyond 10 nail diameters. Refer to
> the footnotes in Table 11N of NDS2001.

Ah, this makes a lot of the sense: the original APA table I referenced
specifies a minimum embedment of 1.325" for 8d commons (0.131"
diameter) and of 1.5" for 10d commons (0.148" diameter).

Thanks, Wayne

Bob Morrison

2006-04-17, 8:21 pm

In a previous post Wayne Whitney wrote...
>
> Shear strength of a nail varies linearly with shank diameter, not with
> shank cross-sectional area?
>

Think bearing stress on the area of the nail projected against the wood.
This comes from dowel bearing strength. The same principles apply for
nails, bolts, screws or any other bearing type connectors including wood
dowels.

So using this method one might assume that the strength of a nailed
connection in 3/4" plywood is 1.5X as strong as one in 1/2" plywood.

However, this is not true because you could get a different failure mode
for the thicker material. It is, however, true for the same material
thickness: capacity is linearly related to the diameter of the fastener.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

2006-04-20, 12:21 am

The most important thing in this exercise is the nailing schedule, something
like four inches on the edges and six inches in the field.

"Bob Morrison" <SpamFighter@junk.com> wrote in message
news:MPG.1ead49ff373678d0989aea@news.west.earthlink.net...
> In a previous post Wayne Whitney wrote...
>
> Wayne:
>
> The tables you want to pay attention to are the ones published in IBC2003.
> They vary slightly from the NDS tables. Mostly in that NDS publishes
> separate values for Wind and Seismic, whereas, IBC uses only the seismic
> values.
>
> Table values in both documents use the same value for "commons or
> galvanized box"and are for Douglas-Fir Larch framing. Any other nail size
> or wood species requires an adjustment of the table values.
>
> --
> Bob Morrison, PE, SE
> R L Morrison Engineering Co
> Structural & Civil Engineering
> Poulsbo WA
> bob at rlmorrisonengr dot com

Bob Morrison

2006-04-20, 1:21 am

In a previous post Ed wrote...
> The most important thing in this exercise is the nailing schedule, something
> like four inches on the edges and six inches in the field.
>

Ed:

You are correct that following the nailing schedule is important. The
question these days is what nail do you use. An 8d nail comes in common,
box, sinker, hot-dipped galvanized, plated, and various gun nails.

That's why I now spec a minimum diameter and length in my nailing
schedules and leave the rest to the framer.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

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