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Re: canopy footing

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I was taught (for better or for worse) a long time ago that if something does not look right, it, most probably, ain't.  What brought my attention to the subject footing that, if drawn to scale, it looks disproportionably small. 
Subsequent analysis proved that the engineer erred - among other things - about 100% on the moment calculation, and even a 5x5 "pole" footing needs to be at least 8 feet deep. Again, drawn to scale, such footing - IMO - looks much more adequate.
Other than that, "There are more things in heaven and earth..."
Thanks, Nels.
Steve Gordin SE
Irvine CA
----- Original Message -----
Sent: Monday, February 13, 2006 9:24 PM
Subject: RE: canopy footing



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