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Re: Tilt-up connections (UNCLASSIFIED)

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When I was doing tilt-ups, we tied the bottom of the panels into the closure strip.

There were also dowels sticking up out of the footing (18"o.c.)  that would bend down into the closure strip as well. So there was a "load path" that transfered from panel dowels to footing dowels in the closure strip.

When there was uplift, we either tied to adjacent panels together, or had hold-down bars out of the footing, using an angle iron and a block out in the bottom two feet to field weld the embeded bars together....this always was a big headache since they never seemed to align from panel to footing...

-g

On 1/4/07, Jake Watson <jake.watson1(--nospam--at)gmail.com> wrote:
This is really the crux of my problem with slab-only dowels.  An R of 5 assumes energy dissipation somewhere.  If there is no foundation tie, where does it occur?  Is the mass of the wall enough to yield the diaphragm?  I doubt it.  So the diaphragm doesn't yield and now your R is closer to 2 or 3 if your lucky.  Do you have uplift now?  Probably.

Does anyone know where the tilt-up exception in PCA originated?  I haven't heard a strong reason to justify slab-only dowels.  However, as I have mentioned before, we also perform plan reviews and try to be a little more open minded during reviews.  But slab-only dowels really makes me nervous.

Jake Watson, P.E.
Salt Lake City, UT

On 1/4/07, Josh Plummer < josh.plummer(--nospam--at)cox.net> wrote:
I'm not really a tilt-up guy, but this discussion begs the question:
"What happens to the shear once it gets into the slab?"

It seems like you're all missing the final step in the load path.  I suppose
the argument here is that friction between the slab and the soil resists the
shear.  That seems to make some sense.  But, if you throw a vapor barrier
under the slab, do you really feel comfortable relying on slab/soil
friction?  You definitely won't have much passive pressure resistance from
the slab.

It's been awhile since I looked at them, but the Tilt-up guys that I know
(at least the ones that I respect) detail out a closure strip with dowels
that coming in from the slab, the wall and the footing.  Maybe that has more
to do with working in a high seismic region than anything else.  Here in CA
we KNOW that we're going to see loads that are significantly higher than
design loads.  Therefore, we need to be more cautious about detailing out
the load path so that our structures will fail with some ductility.

Sincerely,


Josh Plummer, SE



--
-gm