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Re: Nashville, TN area foundation help

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Bill,

I've always used hairpins as part of the load path that goes from column to a-bolts to hairpins to slab reinforcing, with all forces transferred by lap splices. The slab reinforcing, of course, acts as a tie to the column on the other side of the building.

I guess you could leave out the hairpins if you were confident that the bolts wouldn't break out of the side of the slab or that the slab edge wouldn't separate from the main slab reinforcing. But you're right; we have always done it that way and it does work.

Regards,

H. Daryl Richardson

----- Original Message ----- From: "Bill Polhemus" <bill(--nospam--at)polhemus.cc>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, March 31, 2005 10:40 AM
Subject: Re: Nashville, TN area foundation help


Harold Sprague wrote:

Rich,
In a former engineering life, I designed foundations for several PEMB manufacturers.

The first attempt was always to use the turned down slab with the hairpins to take the thrust out of the 3 hinged arch. If the thrust was too great, or you had a feature that precluded you from using the slab as a tension tie, you went to a tie beam and spread footings. In that case it did not much matter what the edge of the slab was like.

The US Army Corps of Engineers lists the frost depth at 22" for Nashville, but you should call the local building official if applicable.

Stepping right in it...

I never got the "hairpin" thing. It always seemed to me to be in the
category of "stuff the old guys did because they always did it that way."

Because My PEMB foundation designs are typically on drilled piers, with
edge beams typically on the order of 30" depth or so, I figure there's
plenty of "oomph" there to resist the thrust without worrying about
hairpins.


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