Non Standard Pile Cap Design 1

[MacGruber22]

Howdy - I have a crazy job with non-standard pile caps galore. Designing with RAM Concept of which I am very experienced with. Concept does not account for d-regions in concrete design so basic strength design checks tend to place stirrups all over the place in even the most standardized pile cap sizes. These stirrups are easy to ignore when I happen to have standard caps in my model...then just pull the designs from the CRSI tables.

I am just losing my confidence in eliminating stirrups in irregular caps. If you consider standard beam design, no stirrups would be required considering d-distances. But, I am concerned that there may be many caps where the stirrups spec'd by Concept are actually non-conservative due to d-region stresses. I spend a lot of time looking at section cut results and trying to combine capacities of adjacent design strips when it seems to make sense to average the shear over a wider area, but I just don't have the confidence in the results so I have ended up with adding stirrups beyond Concept's desires, just so I can sleep. I hate this because we try to be very economical. Deep beam software is fee and far between and it seems like I would need a PhD and 300 free hours to develop deep pile cap spreadsheets to check this.

I can provide some examples from my job if anyone thinks it would be helpful.

-Mac

 

[KootK]

...seems like I would need a PhD and 300 free hours to develop deep pile cap spreadsheets to check this.

Agree.

I can provide some examples from my job if anyone thinks it would be helpful.

Please.

 

[r13]

If you consider standard beam design, no stirrups would be required considering d-distances.

I think you shall check shear at a distance "d" from column face, then provide stirrups from the column face to wherever it is no longer required. I like to provide stirrups to the entire span, with increased spacing in middle span, if it is too closely spaced in d region.

 

[hardbutmild]

Are these non-standard pile caps all similar? Maybe if there are a few different types that occur in the project you can do a relatively simple strut and tie check for each of them. How complex are they?

Maybe I'm not experienced enough, but I wouldn't aim to achieve economy in pile caps, I'd put more reinforcement than needed. Too much uncertainties, too great of a risk.