small footing with large pier

[vincentpa]

I run into this problem quite often. I have a small footing say 4'x4' with a large pier say 2'x2'. The pier is centered on the footing. This leaves 1' - 3" = 9" to develop the bottom or top reinforcing steel from the face of the pier. Generally the reinforcement is minimum steel. What do you do in this situation? Would you consider this a "deep beam" kind of situation, i.e. treat the footing as unreinforced for bending, more of a shear problem than a bending problem?

 

[UcfSE]

How thick is your footing? You may not need reinforcing steel for moment if the footing is thick enough, so you wouldn't have to develop the yield strength of the bar. Temperature and shrinkage is not likely to be bad for a 4-foot footing either. Along those lines, I always supply at least minimum steel and don't typically worry about developing it for such short lengths. If you are in a high-seismic zone, I've heard you should probably have 180-degree hooks on your bars.

 

[jike]

Adjust development length by the ratio of As req'd divided by As provided. If I remember correctly the code requires 12" min. embedment so provide 12" + 3" beyond pier or hook the bars.

 

[MichSt]

I think using 180-degree hooks as mentioned by UcfSE is the best way to go. If steel is needed for strength, you may consider using closed stirrups to ensure your bars are developed.

 

[bjb]

I agree with UcfSE. Your footing probably works for bending as plain concrete without rebar. Also agree that even if it works unreinforced, you should have some shrinkage and temperature steel in there.