Assume that his example is simpler than we you are questioning for the sake
of argument. Your concerns must certainly be considered but my point is that
he seems to be describing what is conventionally used for his area.
Therefore, the question simplifies to "Is there a better method of designing
a raised structure than on Flagpoles?"
Assuming you can restrain the structure laterally as required by local codes
using a flagpole foundation, then I don't see why it is not feasible. You
must consider the story drift as this is often overlooked. In other words,
design the steel and the foundation for deflection per code requirements.
I think I would be most concerned about the issues that David has brought up
even if you take care of the drift problem. I would rely heavily upon the
advice of your local Geotechnical Engineer to recommend appropriate
foundations for the site as this will also provide a limit to the creativity
and take the responsibility away from you with arguing for a more elaborate
system with your client. If he still wants to do something that the
Geotechnical does not agree with, you have the option to walk away.
Dennis S. Wish, PE
From: David Finley [mailto:pec(--nospam--at)isgroup.net]
Sent: Tuesday, March 13, 2001 8:41 AM
Subject: Re: [AEC-Residential] Beach House Foundation
Are you talking about spread footings? If so, how will you prevent
scour/undermining during storm surges, etc.? Is the slab on grade enough to
protect the footings?
If driven piles are not an option, how about some kind of cast in place
David Finley, P.E.
From: Gary Gill <Gary_Gill(--nospam--at)BKITECH.COM>
To: 'seaint(--nospam--at)seaint.org' <seaint(--nospam--at)seaint.org>
Date: Tuesday, March 13, 2001 11:09 AM
Subject: FW: [AEC-Residential] Beach House Foundation
>From: Gary Gill [mailto:Gary_Gill(--nospam--at)BKITECH.COM]
>Sent: Tuesday, March 13, 2001 10:16 AM
>To: 'aec-residential(--nospam--at)polhemus.cc'; 'sharknes(--nospam--at)watkins.dillingham.com'
>Subject: [AEC-Residential] Beach House Foundation
>Any suggestions on which type of foundation needed for a beach house. The
>house will be elevated about 10 ft above grade and supported by 16"x16" cmu
>piers/columns. The pier are spaced 10 ft apart more or less. There will be
>slab on ground. The client will have the capability of parking vehicles
>under the house. I'm thinking that I will have individual footings for the
>interior/outside piers (the wind load is take by the outside piers) with
>grade beams to tie everything together. The client does not want any brace
>bracing. The outside pier and footing will be design like a flag pole. Any
>suggestions or better ways of designing the foundations. Driven piles is
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