concrete friction

[struct_eeyore]

Hi all,

I have recently been asked to verify a generator footing - it was designed/poured without engineering and county rejected it. Unfortunately, the footing was not sized for overturning - need 37k-ft for 1.6 factor, and deadload of generator and footing only provide 18k-ft. However, the footing actually rests on an existing 6" concrete slab and poured adjacent to another pad. So this might be far-fetched, but I am wondering if it is legitimate to assume that on the end of the footing that is poured tight, assuming there is no sliding, a couple is formed to prevent overturning (as in a piece of concrete would have to be sheared off to allow the vertical edge to lift up past another vertical edge, or alternatively, get crushed to go the other way. And as gravy on top, I am also wondering if I could use some values for concrete adhesion to provide some tension to the free edge of footing.

Thanks
-G.S.

 

[SlideRuleEra]

So this might be far-fetched...

Agreed. Stop right there.

Suggest developing a solution to properly anchor the generator, not trying to justify an inadequate as-built installation. Generators are dynamic equipment, there can be (and have been) times where a 1.6 factor is no where close to enough to prevent destruction.

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[struct_eeyore]

Ok then! I just want to be able to tell the contractor I am not the only one who thinks that work need to be done...

 

[SlideRuleEra]

...need 37k-ft for 1.6 factor, and deadload of generator and footing only provide 18k-ft.

structee - Here are some numbers to help substantiate your report:

23.1 k-ft are needed (factor of 1.0) to prevent overturning (37 / 1.6 = 23.1)
18 k-ft are available...
Before any (theoretical) friction comes into play, the generator will have overturned.

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