Insufficient depth of pilecap thickness 1

[wraymy]

Out of my curiousity, what if the pilecap which has been casted is found underdesigned in terms of insufficient pilecap thickness?
is there anyway to rectify the pilecap other than enlarging the column? if the column is designed to be pinned at bottom (which by means the column does not transfer moment to the pilecap), would drilling 12D into the pilecap will be sufficient?

 

[MIStructE_IRE]

Hi,

Forgetting about the column for a moment, does the cap itself still work in terms of strut and tie action (assuming you’re using that analysis method?). Does pile punching still work?

Assuming the column above has not been poured, have you sufficient depth to pour a spreader beam on top of the cap?

 

[KootK]

This smacks of insufficient punching shear capacity to me.

if the column is designed to be pinned at bottom (which by means the column does not transfer moment to the pilecap), would drilling 12D into the pilecap will be sufficient?

I'm afraid not. Those bars would still be delivering their compression to the same frustum of concrete that would be failing in punching shear. You might solve a bearing stress issue at the joint but not punching shear.

Out of my curiousity, what if the pilecap which has been casted is found underdesigned in terms of insufficient pilecap thickness?

In addition to the fine spreader beam idea:

1) Hang your hat on 56 day concrete strength if that's enough to get you through. Diminishing returns owing to f'c being under the root.

2) If your piles are within, say 2 x cap depth of your applied load, you might be able rationalize the load via the strut and tie principles that MIS mentioned.

3) If your piles are close enough to the load that your punching frustum would have sides steeper than 45 degrees, there are alternate punching shear formulations yielding higher capacities.

I'd recommend posting your loads, utilization ratios, and sketches of your geometry for this. That will allow us to provide you with much more meaningful assistance.