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RE: Nashville, TN area foundation help

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Rich,
I don't believe there is an ISBN. The book was developed for Butler and their sub consultants.

The tension ties that I have done are either the hairpin that loops around the anchor bolts and laps onto the WWR transferring the tension into the WWR. The WWR in the slab then serves as a tension element. The tension tie is in the form of a V shaped rebar that extends out into the slab to engage the WWR.

Another tension tie is to embed a rod with a headed end in the slab to a point beyond the anchor bolt group. The rod can be joined using a coupler.

A third tension tie is to use reinforcing steel that has U bars around the anchor bolt group. The reinforcing steel is then connected with mechanical couplers. The entire reinforcing steel group is then encased in concrete to form the tension tie.

Regards,
Harold Sprague




From: "Rich Lewis" <sea(--nospam--at)lewisengineering.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Nashville, TN area foundation help
Date: Fri, 1 Apr 2005 12:31:03 -0600

Harold,

I guess I look like an old guy.  I went into Wendy's early in the week and
got a discount on my meal.  When I asked why she said "senior citizen".  I
asked if I looked that old and she wouldn't give me a straight answer. This
is my first senior discount.

Can you clarify your third paragraph? You gave two conditions for a tension
tie.  Did you mean for the first to be hairpin?

When I use a tension tie I detail a 'U' shaped bar to wrap the anchor bolts. Is that what most people use as a tension tie. I should also say that for a
hairpin I detail a 'V' with a flat bottom to wrap the anchor bolts.

Also, can you give the ISBN for the text "Foundation Design and Construction
Manual"?

Thanks.


Rich Lewis




-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com]
Sent: Thursday, March 31, 2005 1:56 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Nashville, TN area foundation help

Bill,

OK... I am an old guy.

For smaller (30 to 40' span) PEMB's with just spread footings, hairpins are
very efficient in transferring the lateral thrust from the anchor bolts into

the slab and the slab WWR forms a tension tie. For longer spans you need to

put in a tension tie in the form of a rod or rebar in a tie beam.  If you
have drilled piers, you are correct, they can take a lot of lateral thrust
depending on the soil.

The best resource for PEMB foundations is Foundation Design and Construction

Manual by Buettner, Fisher, and Manske (Computerized Structural Design,
Inc.).  It was written for Butler Manufacturing.

My own practice is to use a tension tie until you get beyond a 15.2 k
service thrust load.  Beyond that I use a tension tie.  Again, if the soil
requires them for gravity loads, I may use a drilled pier.  The only
potential problem is that you have to calculate the long term lateral
movement of the top of the drilled pier.  It is not a huge problem, but it
has to be considered.

If you use a turned down edge of a slab in bearing, you generally have to
discount the top 18" (no overburden to facilitate passive)  which puts
moment into the slab, and again, the passive pressure is allowed, but there
is the potential for sideways settlement in some soil types.  It is doable,
but it adds some considerations.

The Foundation Design and Construction Manual also has some good information

on using horizontal soil resistance.

Regards,
Harold Sprague




>From: Bill Polhemus <bill(--nospam--at)polhemus.cc>
>Reply-To: <seaint(--nospam--at)seaint.org>
>To: seaint(--nospam--at)seaint.org
>Subject: Re: Nashville, TN area foundation help
>Date: Thu, 31 Mar 2005 11:40:44 -0600
>
>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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