Pile Supported grade beam load distribution at piles

[civilOAK]

Hi,

Attached is a foundation plan for grade beam which is supported by piles. You will see the the column load ( Pmax) lines with center of one the piles at Section A. I am trying to take the advantage of 3 ft thick grade beam and use springs for pile supports. Instead of applying 100 % of the Pmax to one pile, Has anyone an opinion or a reference that explains What percentage of Pmax can be distributed to the other pile which is 3.5 ft apart?

Thank you

 

[rscassar]

Any resource on pile cap design might be helpful. I wouldn't be sharing the column load between all piles.

As long as the span to depth ratio does not exceed 4 I would be assuming that the grade beam is rigid and designing using strut-tie.

 

[civilOAK]

Kikflip Thank you for your response

I dont need to worry about the grade beam this is an existing structure foundation that i am analyzing. If i apply the pmax to one pile at the corner it exceeds pile capacity therefore i am trying to use springs for all piles or at least some to distribute some of the Pmax to the adjacent pile. If this was a new design i wouldnt worry and just applied Pmax to one pile and be done with it Normally we design piles according to the static distribution depending on the geometry in the pile cap but unfourtanetly if i use that results show that pile under Pmax has to take 100 % of Pmax. So as a result your conclusion is to use 100 % of Pmax to one pile ? You can also look at the attachment to see the two 3.5 ft apart piles at the corner.

 

[rscassar]

Personal opinion, If you are applying new loads I would provide new piles. Do you know what reinforcing is in the existing grade beam. If you want it to transfer loads to the other piles you will need to set up a strut-tie model and without knowing the reinforcing in the grade beam it would be difficult to quantify that the grade beam can distribute the forces.