Punching shear and direct shear in pile cap design

[ynnuseel0106]

As far as I know, when I design a pile cap, I need to check the direct shear in two orthogonal directions, and then I need to check the punching shear under the concentrated load or support. Then I have a question, should the provided shear reinforcement be the sum of the three components (direct shear x + direct shear y + punching shear)? Some said that after I have checked the punching shear and provide punching shear reinforcement, I no longer need to check for the direct shear. Is that correct?

Thanks very much for help.

 

[Trenno]

What reinforcement are you providing to resist punching shear? Not stud rails right?

 

[ynnuseel0106]

Just normal links with 90 degree hook at one end and 135 degree hook at the other end

 

[cliff234]

We size pile caps so that shear reinforcing is not required. We follow the procedure specified in the CRSI Manual. We rarely use shear reinforcing in standard pile caps supporting columns. To answer your question, if you do have thin pile caps, there is no guarantee that providing punching shear reinforcing will eliminate the need for beam shear (or what you call "direct shear") reinforcing.

 

[KootK]

I do not believe that the three demands for link reinforcement would be additive. If one were to split hairs, I suppose that a couple of links might be double counted where the two direct shear failure planes cross.

I agree that both direct shear and punching shear should be evaluated in all cases.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[allimuthug]

Hi there are two shear checks for pile cap , Two way shear check for pile which occurs at d/2 distance around pile ,Beam shear occurs between pile and the pedestal , Better increase the thickness of pile cap. else you have to provide shear reinforcement in the pile cap for shear reinforcement in pile cap, The 90 degree and 135 degree shear link is provided for shear reinforcement in pile.