Concrete Clear Cover

[masterz]

I'm designing a foundation for a pier. It's huge. It is 12x48 and has 22.25" of clear cover from the edge of the rebar to concrete edge. Does anyone see a problem with that much clear cover? It has been designed this way because of some deflection requirements. What strength will 22.25" of concrete provide. I must provide something because it meets the deflection requirement but I'm worried about issues with no reinforcement in that area.

 

[hokie66]

I see a problem, but you have not well defined your problem. What do you mean by "deflection requirements"? 12x48 what? Feet? Plan dimensions?

 

[dik]

Can you post a sketch? show pier, footing and rebar location with dimensions?

Dik

 

[jayrod12]

If your pier is in bending you can check your cracking control. I don't know where you will find it in the US codes but in the CSA 23.3 it's clause 10.6.1

 

[masterz]

Ok, sorry I didn't give you many details. I was in a rush to get a post. Here are more details. I have a concrete pier with an bolt circle diameter of of 97.25". It consists of 48 #18 bar (2.25" 75KSI STEEL). The foundation size is 12 ft x 48 ft. These are FULL length anchor bolt cages that are to have the reinforcing cage tied to it. The reinforcing cage isn't separate but I can make it that way if I can get your opinion. My problem is that the foundation is sized 12' in diameter and that provides 22.25" of clear cover with no reinforcement in that area. Does ACI code specify if you can have a ton of clear cover with no reinforcement in it or would it be prudent to add reinforcement in that area? I know they specify a min (3" to earth). I'm currently thinking of designing a separate cage that goes into that area but provides enough room for flow ability. Please share you thoughts. Thanks.

 

[dik]

How thick is the footing? If overhang is 2' approx and footing is 2' thick approx, then not likely an issue...

Dik

 

[jayrod12]

If I'm understanding his description correctly dik I'm fairly sure he's actually got a giant caisson that is 12ft in diameter and 48 feet deep

 

[AELLC]

#4 at 12 each way.

The definition of a structural engineer: overdesign by a factor of 1.999, instead of the usual 2.

 

[Ron]

What diameter do you need for the loading? If only 8' + cover required for loading, then not really an issue except a waste of concrete. If you need something beyond for load purposes, increase the reinforcing cage diameter but not so much as to lose the influence for the anchor bolt cage needs.

 

[hokie66]

"some deflection requirements" has still not been explained. If the size is required because of bending deflection requirements, it needs to be reinforced. If just in compression, maybe not.

 

[dik]

jayrod... I'm trying to find out the thickness of the slab overhanging it if the primary support is 12' dia...

Dik

 

[WiQi]

what is the purpose of this foundation or what is the structure to be built on this support?