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RE: cantilevered columns

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Michael,
I would suspect that the uplift from the wind might make for a pretty hefty
deadman foundation. I have done similar, but virtually always extend steel
columns through a grade beam and onto an erection pad. Before the latest
code I always assumed the worst case lateral load of at least 30% base shear
of the roof structure (and designed uplift for wind). Lately with an R of
2.2 in my area, I'd be designing closer to 46% of base shear.

I designed a simple trellis structure for a Starbucks in my area and treated
it the same way. The difference was that the weight was so small and the
trellis an open structure that I was able to use pad footings to resist both
moment and wind. In fact, in this case, the architect demanded that the
exposed portions of the columns above the plaster columns be rough sawn
lumber. To accomplish this, I created the moment connection with a tube
steel sleeve embedded into a post hole foundation and slipped the wood
column into the sleeve. I extended the sleeve approximately 36" above the
top of footing so that almost 6' of the column (3' below top of find and 3'
above) was encased in steel. Machine bolts were installed to hold the
columns in place for possible wind uplift.
I did this so that the columns could be replaced easily if ever damaged
(cars hitting the columns etc).

Sorry, I know it was a long answer to a short questions. Hope it helped.

Regards,
Dennis S. Wish, PE

-----Original Message-----
From: Michael Zaitz [mailto:zmanpe(--nospam--at)bellsouth.net]
Sent: Wednesday, April 19, 2000 6:28 PM
To: seaint(--nospam--at)seaint.org
Subject: cantilevered columns


Is there any standard practice for the lateral support of drive thru's at
banks for wind or earthquake?  I am doing a new bank that is being slightly
copied from an existing.  The original engineer used moment connections on
the beam to column connections for lateral stability.  I am thinking of
using a cantilevered column with a spread footing to take the moment.  Is
there any pitfalls with this?  Any other ideas (bank is wood framed with
wood trusses for the most part, steel where needed.)

thanks,

Mike