Factored two-way shear stress in THICK pile cap due to pile - take moment at cap centerline or bottom face?

[Ronengo]

Hi all, I think I have a relatively simple question that we are getting pushback on.

Please see the attached sketch. We have a very thick pile cap and a very large pile.

For the two-way shear stress check, would you take Msc as Mpile (moment at bottom face of pile cap), or would you take Msc as Mlink (moment at centerline of pile cap)?

I think the answer would simply be the centerline if the pile cap was thin. However, given that it's an extremely thick and stiff pile cap, we are getting pushback on whether the moment we consider should actually be at the bottom face of the pile cap.

Any thoughts or references are very welcome. Thanks in advance!

 

[canwesteng]

I would always take it at the pile/pile cap interface

 

[ThomasH]

Given the thickness of the pile cap and the diameter of the pile, what are the other dimensions of the structure? Length of pile, size of pile cap etc.

If the question concerns the local effects I would use a model with volume elements to check the stress distribution.

 

[HTURKAK]

For the two-way shear stress check, would you take Msc as Mpile (moment at bottom face of pile cap), or would you take Msc as Mlink (moment at centerline of pile cap)?

How did you model the pile cap and pile ? Is this a raft foundation supported on piles?
Pls provide more info. ( size of the pile cap , number and spacing of piles ..) to get better responds.