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RE: canopy footing

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It seems to me that the proportions of the cube should not prevent its use for this application.  Suppose that, by a trial-and-error solution, you found that an 18” wide by 5-ft deep footing did not have adequate capacity by the formulas of 1806.2.  You would have a couple of options for improving the capacity: try deepening the footing or try widening it; either seems to be a reasonable option.  At what width does the increase in width become unreasonable?  What if it took a width of 5 feet to develop the capacity?  That seems O.K. to me.  What if it took 6-ft?  Seem O.K. to me too, but I would probably try to figure out how to take advantage of the gravity-moment-of-stability provided by the weight of the massive footing.  It would take more concrete than a deeper footing, but I think it would comply with the Code.


However, if for some reason, the footing needed to be dug by hand, widening is may be a better option than deepening it; for example, if the OSHA rule is in effect that requires that an excavation that a worker enters must be shored if its depth exceeds 5-ft.


Nels Roselund, SE

South San Gabriel, CA


From: S. Gordin [mailto:mailbox(--nospam--at)]
Sent: Monday, February 13, 2006 10:47 AM
To: Seaint@Seaint. Org
Subject: canopy footing


Good morning,


I am reviewing a "standard" design of a canopy - a steel-framed structure with two cantilevering columns 14' tall supporting a light "low-pitched V" roof measuring 16'x24' with 12' cantilever. 


The engineer used UBC formula 6-2 (Section 1806.8) to justify the adequacy of the footings for the columns - 5'x5'x5' "cubes."  According to the UBC Commentary p. 297, the formulas of UBC 1806.8 are historically applicable to "pole-" or "column-" type footings. 


To me, these "cube" footings do not even look right for the subject application.  Any comments on the situation will be highly appreciated.




Steve Gordin SE
Irvine CA