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New Footing Next to Retaining/Foundation Wall 2

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RareBugTX

Structural
Joined
Aug 31, 2004
Messages
214
Location
US
Hello:

I am designing at footing next (on the unexcavated side) to a retaining masonry foundation wall. New footing will support a three story steel porch structure. Question is,

The reinforced pedestal is 36"x24" rectangular in plan and 7'-0" high and it will be beneath the earth right next to the existing foundation wall. do you consider such high pedestal a column?, what do you use for "K". Once construction is finished it will be completely surrounded by compacted earth. Your comments are appreciated.
 
Aspect ratio doesn't lend itself to buckling so I wouldn't consider it a column. Just a spacer!
 
I don't see this a particularly worrying situation from the buckling viewpoint. Once surrounded most would accept no buckling is viable (even if maybe towards the wall is feasible). For construction time what K to take is more a matter of the condition of braced or unbraced of such pedestal, it could go over 1 if part of a sway frame. Anyway a thick and not too tall member so buckling effects must be scarce.

A more proper establishment of one equivalent K for stability issues will be difficult, particularly because of the indeterminacy of the buried condition ... earth may be causing spreading forces against the pedestal that won't be being counteracted because of the jointing material -buckling of one in-length laterally loaded member- what normally will remain an unknown. It would be wise make some allowance for such actions.
 
Thanks Ron and Ishvaaag! for your valuable input.
 
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