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Re: Uplift resistance

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Seth,

        There have been some good suggestions mentioned but none have
suggested drilled and grouted anchors.  These are fairly common in
underground parkades when the parkade is also below the water table.
There is a German company called Dywidag which does this sort of thing
(the same people who make concrete reinforcing and prestressing bars
with screw thread type deformation patterns) and is active in Calgary.
They are probably also active in a city near you.

        If you are considering piles you might also consider screw
piles.

Regards,

H. daryl Richardson

Clifford Schwinger wrote:

> There are a lot of options for solving your uplift
> problem, but its kind of hard to tell which is best
> without seeing your drawings.  In addition to the
> suggestions noted by others, here are a couple more:
>
> If footing with net uplift is near some adjacent
> footings you run a grade beam between the footings
> immediately to the left and right of the one with the
> uplift ?problem? and use the dead load on the adjacent
> footings to hold down one with uplift.  This is
> usually most efficient for when you have really big
> uplift forces.  Your uplift forces are probably not
> high enough to justify this solution.
>
> If the uplift is occurring on a column that?s in a
> braced frame, you could place both of the braced frame
> columns on a common rectangular footing and stretch
> the length of the footing as needed to keep your soil
> pressure at or below the allowable pressure and to
> maintain your safety factor against overturning.
>
> You could jog the bracing around as you go down the
> building to distribute the uplift forces around to
> multiple columns.  If the uplift is occurring from a
> braced frame that?s comprised of two columns with
> diagonal bracing between them from roof to foundation,
> try shifting the bracing over a bay for one or two
> floors to spread the load over three columns instead
> of two.
>
> Add another braced frame to take some of the load off
> the one that has too much uplift.
>
> All of the above solutions have one thing in common ?
> they make use of the dead loads in adjacent columns to
> help resist overturning moments and minimize the need
> to add blobs of concrete solely for the purpose of
> providing an ?anchor? ? however in some cases this
> might be the most economical solution (especially for
> fairly small uplift forces)!
>
> Adding tension piles sounds kind of expensive ?
> especially if there are no other piles on the project
> (which I?m assuming there are not.)
>
> Hope this helps.
>
> Cliff Schwinger
>
> --- "Seth W. Cutler" <seth(--nospam--at)rlmorrisonengr.com> wrote:
> > I'm working on a steel building which has uplift
> > forces in the order of
> > 50-170 kips in isolated locations.  The foundation
> > design is spread footings.
> >
> > Any suggestions?  Do I have to go to piles to
> > accomplish this?
> >
> > Thanks,
> >
> > Seth W. Cutler
> > R. L. Morrison Engineering Co.
>
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