big concrete pier
big concrete pier
(OP)
I am designing a very large concrete pier - 4' deep by 7' wide by 7' wide that has a small column load at the center and is bearing on soil. Does anyone know of any good reading material of steel reinforcement guidelines to go by? I originally reinforced it based off of standard pier guidelines (aka 1/2% steel)and concrete column tie guidelines, but the contractor is not happy about how much reinforcement that is. I would appreciate any help you could give me. Thank you.






RE: big concrete pier
You can treat it like this even if it has some reinforcement.
csd
RE: big concrete pier
There are also provisions in ACI-318 for unreinforced concrete- you might look into that, figuring that if the design is adequate with zero reinforcing, then you can put whatever you want in it- not sure if that's kosher or not.
RE: big concrete pier
RE: big concrete pier
RE: big concrete pier
RE: big concrete pier
RE: big concrete pier
Second, As I recall ACI, it is 1/8 square inch per foot of concrete surface for temperature but in no case less than #blanks as 18".
Regards,
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RE: big concrete pier
RE: big concrete pier
RE: big concrete pier
RE: big concrete pier
RE: big concrete pier
RE: big concrete pier
RE: big concrete pier
Note: Why is it 7x7? One should be able to excavate a much smaller pier.
RE: big concrete pier
We do this kind of footing all the time, where the footings are trench footings down to frost depth under the walls of the building, and then widen out at columns. It is pretty much standard in the midwest. Very rarely are shallow footings formed around here. Cheaper for the contractor to waste the concrete than to spend time forming them up.
Personally, for a 7'x7' footing, I would design the footing as a 7'x7'x1'-0" thick footing. Figure out area of steel required, put that in the bottom of the column footing, run the trench beam reinforcement trough the footing, and call it good. The extra 3 feet of concrete at the column footing is just backfill for the excavation.
RE: big concrete pier
"Members that are continuously supported by soil or supported be other structural members capable of providing continuous vertical support."
Given small magnitude of the load compared to the size of footing, I believe the above requirement is satisfied and hence the footing can be unreinforced.
But as DRC1 has mentioned, the concrete may not be of very best quality, so providing #4 rebars at 12" on center near top and bottom should be sufficient.
RE: big concrete pier