Drilled Pier Cap Design

[BAGW]

Hi,

I have a situation where the steel column directly rests on the drilled pier with a cap. As the column is directly supported off the drilled pier there is no punching shear or one way shear check nor any flexure in the pier cap. Cap for the drilled pier is provided to accommodate the base plate size. In such scenarios how to size the cap thickness as shear and flexure is not limit state for such situation.

Minimum cap thickness will be driven by anchor embedment depth and rebar development length. Any other checks needs to be performed?

 

[jayrod12]

Nope, you've got it. Size it to fit anchors including edge distances etc. Otherwise it's just a axial load transfer element.

Edit: assuming there's no uplift or shear on the connection of course.

 

[BAGW]

How does the design change for the drilled pier cap with uplift. isnt it still the same

 

[jayrod12]

Yes, but you need to make sure the uplift from the anchors has somewhere to go.

If it were compression only and perfectly concentric, you could literally just place a blob of unreinforced concrete down. But once there's uplift, flexure or shear, you need to reinforce it accordingly.

Mainly it will be ensuring the pile and cap are tied together adequately to transfer the uplift from the cap to the pile, and also ensure the cap is reinforced to take the uplift from the anchors to the connection to the pile.

 

[BAGW]

Thanks.

 

[cliff234]

Some suggestions: Extend ties to the top of the cap. Provide additional ties at top of cap per ACI 318. Provide minimum EW, T&B rebar in cap (for crack control). Detail the vertical bars and anchor rods for tension (if net tension is occurring).