Minimum steel in pier

[llamallama]

I was asked to review a reinforced concrete footing/pier which supports a steel canopy. After review the footing meets code and is more than adequate, but the pier has less than the code required long. steel for columns (<0.3%). The pier meets the criteria for mass concrete dimensionally, but with anticipated lateral loads, the resultant is outside the middle third.

The issue is it is already constructed including final paving above. I am leaning toward saying to excavate and place mass concrete around the pier.

Any thoughts? Thanks in advance.

 

[rscassar]

what are the dimensions of the pier?

 

[llamallama]

Sorry, the pier is 16"x16" and 24" high with a 5kip lateral load. the reinforcing is four #4 bars.

A second pier is slightly larger at 20"x20" and 24" high. with the same reinforcing and load.

 

[steellion]

I don't believe that you need to meet minimum column reinforcement requirements (1%) for piers, but you do neet to meet requirements for pedestal reinforcement dowels into the footing (0.5%) - ACI 15.8.2.1.

That's just my interpretation.

 

[nutte]

but the pier has less than the code required long. steel for columns (<0.3%)

Where is this code provision contained? ACI 318 says, in section 1.1.5, that it does not apply to portions of drilled piers embedded in the ground (except for certain seismic situations).

I'm not saying the design isn't suspect; rather, the minimum requirement you're referencing may not apply.

 

[llamallama]

Thanks for the replies. This was an excavated/formed pier, so I didn't think section 1.1.5 applied. I've always assumed that was for earth-formed piers (i.e. augered holes w/ rebar cage) and not formed piers.

 

[Teguci]

Not a foundation pier - use ACI 318 - Compression member design - Minimum steel = 0.5% for oversized column. Bad day for somebody.

 

[DaveAtkins]

My interpretation is that this pier does not have the minimum required area of steel (0.5%), and should therefore be checked as an unreinforced pier.

Phi*Mn for the 16" X 16" pier = 10.8 KF (assuming f'c = 4,000 psi), so if the 5 kip lateral load is an ultimate load, you are OK (Mu = 10 KF).

DaveAtkins