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Re: Eccentric Load on Drilled Pier

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> From: "Rich Lewis" <seaint04(--nospam--at)lewisengineering.com>

> I'm designing a foundation for a pre-engineered metal building with 75 ton
> overhead crane.  The overhead crane has independent columns for vertical

> I'm looking at 2 design solutions.  The first is a spread footing.  It works
> out to about 17'x13'x2'.  The contractor would like to look at a drilled
> pier option.  He thinks it may be cheaper.  I was initially looking at

I'm curious:
Can drilled piers be installed at an angle (soil dependent)?
How deep is practical?
How big (dia) is practical?

17x13x2/27 = 16.4 cu yds
vs
2x(1.5^2)/4xpix10/27 = 1.3 cu yds / 10 ft
+
8'x3'x2'/27 = 1.7 cu yds cap

Looks like your budget is equivalent to about 10-13 cu yds of concrete
per location. Based on these numbers, and some of the install numbers
that have been quoted, you could put several drilled piers (e.g. 4).
Less concern for moment and eccentricities.

> concrete slab between the PEMB rigid frames to work with.  I can have a
> tension tie between the columns.  They tell me they will never cut the slab

Check the axial deformation between columns with the tension tie option.
This is a big crane and the consequences of unintended deformations can
be serious. 

Regards
Paul

-- 
R. Paul Ransom, P. Eng.
Civil/Structural/Project/International
Burlington, Ontario, Canada
<mailto:ado26(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>

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