Pile cap design Questions
Pile cap design Questions
(OP)
We are using RISA Foundation to design a pile cap. The piles are in a radial layout. We want to design the reinforcing in a rectancular grid. We have modeled it and it looks good. We how do we check our results? Any ideas?






RE: Pile cap design Questions
Check bearing.
Provide more info?
RE: Pile cap design Questions
But seriously, we need more info, because there are over 20 mechanisms of failure that could be apparent in your pile cap, and I don't have all day. If this is a typical pile cap, say 4 piles you could do a strut tie for reo and punching check by hand. but again I want more info.
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: Pile cap design Questions
DaveAtkins
RE: Pile cap design Questions
THe piles are 18" diameter.
RE: Pile cap design Questions
Wasn't meaning to say hand clas were funny, What I was hahaha was the fact that saying hand cals without more info is about as helpful as a hole in the head.
SO Hand cals are required Just to be clear!!! Once we have more info we can be more specific.
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: Pile cap design Questions
Work out two rough continuous beams:
1) A radial beam
2) A circumferential beam
The top and bottom steel that you calculate should roughly match the output from your model.
Also check punching shear and one-way shear based on a tributary area calculation.
RE: Pile cap design Questions
If so, then the FEM output for that program is much friendlier for producing concrete design information than just looking at Von Mises stresses.
To hand verify the results, I would take a two or three step approach:
1) Verify the reactions in the piles. A quick and dirty method would be confirming that the sum of reactions = sum of applied loads. Then also confirm that the centroid of applied load = centroid of the reactions.
2) Graphically view the bending moment and shear diagrams in the design strips. Compare this to what you would get from a continous beam model with a similar applied load.
3) After you confirm those numbers are in basic agreement with your hand calc method, then moving from moment and shear demand to reinforcement and code checks should be pretty simple.
The program doesn't do punching shear calculations yet (as it is geared towards soil supported foundations), so you would have to check the punching of the piles through the slab manually.
Josh
RE: Pile cap design Questions
RE: Pile cap design Questions
RE: Pile cap design Questions
you can get bending Reinforcement based on finite element stress but again consider that finite element mesh affect the results.
Many times in this problems i do computer model but should study the results and verify it and sometimes i re-distribute the reinforcement as well
RE: Pile cap design Questions
RE: Pile cap design Questions
RE: Pile cap design Questions
RE: Pile cap design Questions
Think of your problem as an elevated slab, not as a foundation, since you have concentrated pile reaction points (like columns) and not a bed of uniform soil springs.
Use a simplified strip method - coefficients from ACI 318 from direct design method (section 13.6) will usually suffice - to get moments & shears within 15% accuracy. Easier to think in 2-D.
You should do this before you turn on your computer.
RE: Pile cap design Questions
RE: Pile cap design Questions
Thanks all for the input.
RE: Pile cap design Questions