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Re: Concrete Nails

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Another view:
If the 2x6 posts are structurally ok without been nailed to the concrete
then there is no problem. If the nails are required for the solution to be
structurally acceptable then there is a problem. The critical question would
be the role of the nails in the transfer of load from the posts to the
foundation. It is apparent that the shear resistance of those nails would
come into play. Just a thought.

Carlyle Glean
----- Original Message -----
From: "Gerard Madden, SE" <gmadden(--nospam--at)attbi.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Sunday, May 04, 2003 1:26 PM
Subject: RE: Concrete Nails


> I guess I'm wondering why is there a hearing? I see no mention of what
> the problem was unless I missed something.
>
> If the double 2x6 is sitting/bearing on the foundation, it is
> essentially a post. It will not transfer any load to the stem unless it
> moves. The fastening of the 2x6 to the concrete would limit the unbraced
> length for buckling. If the concrete nails have some withdrawal
> capacity, they could also contribute to unbraced length shortening in
> the other direction.
>
> If the post is only 5 feet long unbraced length, the double 2x6 is good
> for about 15 kips (DF #2), so its way strong for your situation.
>
> The potential problems I could see with this are not using pressure
> treated wood or naturally decay resistant wood in contact with concrete,
> capacity of the footing since you do not have the stem to spread the
> load (unless you are trying to take the load through the concrete nails
> which I previously said would not work if the bot. of the post is
> bearing on concrete). The thickness of the footing may not be enough to
> take the punching shear and check soil bearing. If you are in Canada,
> you have low footings due to frost line and the soil bearing capacity is
> probably close to 3 ksf at that depth, so you should be okay there too.
>
> If you want to force the load through the concrete nails, you would need
> to cut the bottom of the post so it hangs off the stem of the footing.
> Then, as long as the dowel equations work for the specified load, I
> don't see a problem.
>
> HTH,
> -gerard
> Santa Clara, CA
>
> -----Original Message-----
> From: Daryl Richardson [mailto:h.d.richardson(--nospam--at)shaw.ca]
> Sent: Saturday, May 03, 2003 8:32 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Concrete Nails
>
> Fellow engineers,
>
>         A colleague of mine, a registered P.Eng., is facing a discipline
> committee hearing regarding the suitability of one of his structural
> designs.  He has asked me to sit in as an expert witness on his behalf
> and I have agreed to do so.  One of the key issues will be the
> suitability of the use of concrete nails in securing a double 2x6 "post"
> to a concrete foundation wall.  To help me prepare for this role I would
> appreciate any comments you are prepared to send.
>
>         The situation details are the following.
>
>         The hearing date is May 13, but some documents must be filed by
> May 6 (not yours, of course).
>
>         The project is standard residential wood frame construction.
> The house is a single family "split level" located in south/central
> Alberta.  Seismic is virtually zero; wind is fairly high; but neither of
> these are applicable to the case.  Usually a structural engineer is not
> involved with a single family residence in Alberta unless there is some
> special circumstance such as an unusual beam arrangement, a retaining
> wall, or some problem such as the one I am describing develops.
>
>         The floor system is 2x10 floor joists supported on laminated
> wood beams (possibly MicroLam or ParaLam both of which are made op of
> approximately 1/8" laminations with the glue plane vertical and
> totalling 3.5" in width) which are, in turn, supported on columns.
> Normally, there is a pocket cast in the foundation wall to support the
> end beam beam reaction; but on this project the pocket was omitted,
> hence the problem.
>
>         The foundation wall is 8" thick; the strength and age of the
> concrete are unknown.  Normally, concrete strength would be about 2,500
> p.s.i. and it could be normal or sulphate resistant.  One may speculate
> that the concrete age might be from 5 to 15 days.  Below the wall is a
> footing 6" thick and 16" wide.  There is no requirement for reinforcing
> steel in residential concrete basements although some builders place ten
> millimetre or #4 bars horizontally at 15" centres.
>
>         Since the beam pockets were omitted my colleague got involved.
> His solution was to place a 2x6 "on the flat", against the wall and nail
> it to the wall using ten 5" long by 3/16" diameter concrete nails.  He
> then took a second 2x6 and nailed this directly to the first using "an
> appropriate number of ordinary wire nails".  This provides a 3" seat for
> the laminated beam.  The double 2x6 are approximately 5' long or less
> and are also in contact with the wall's strip footing.  The slab on
> grade basement floor is placed directly on top of the wall footing
> encasing the double 2x6 post.  Unless I have been misinformed there has
> been no indication of a failure taking place.
>
>         Please comment on a) the suitability of using concrete nails in
> this way, b) the capacity of such nails, or c) anything else related to
> this situation you want to.  All replies will be appreciated.
>
>         Thank you.
>
> Regards,
>
> H. Daryl Richardson
>
>
>
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