Agent Coconut
Structural
- Dec 27, 2024
- 21
Hi everyone,
When we are calculating the pile reaction based on position of pile in respect to column and pilecap CG, we often use this formulae,
Ned/n +- M*x/∑x^2 +- M*y/∑y^2
However, one issue with this formulae is the assumption is a rigid cap, and the further away the pile it is, it will attract more load.
For instance,
Pile position (-300,0 ; 300,0 ; 900,0) where column are (0,0) with column load of 900kN
In this case we can get pile reaction of 525kN, 300kN and 75kN.
If we change to (-300,0 ; 300,0) only, we can get equal reaction of 450kN.
This made no sense as in this case, and in my case, the third pile is actually an extra pile. (That story for another time)
So, out of desperate, thru AI, I was present a simplified truss method but afterall it is an AI so I am verifying if this method is valid/practical or even use by any one where we use simplified truss method.
The formulae above is still valid but improved become
Ri (aka ratio of weightage) = z / sqrt(x^2 + y^2 + z^2)
Axial load = Ned * Ri/∑Ri + Mx*Ri*x/∑(Ri*x^2) (same goes to My)
Via this equation, we get a very realistic pile reaction where pile closer to column having higher pile reaction, and height of pilecap also contribute to the loading distribution.
I attached my spreadsheet for everyone easier reference.
Or if anyone have seen this method before, please share me the reference so that I can properly credit the author or strengthen the use of this approach.
When we are calculating the pile reaction based on position of pile in respect to column and pilecap CG, we often use this formulae,
Ned/n +- M*x/∑x^2 +- M*y/∑y^2
However, one issue with this formulae is the assumption is a rigid cap, and the further away the pile it is, it will attract more load.
For instance,
Pile position (-300,0 ; 300,0 ; 900,0) where column are (0,0) with column load of 900kN
In this case we can get pile reaction of 525kN, 300kN and 75kN.
If we change to (-300,0 ; 300,0) only, we can get equal reaction of 450kN.
This made no sense as in this case, and in my case, the third pile is actually an extra pile. (That story for another time)
So, out of desperate, thru AI, I was present a simplified truss method but afterall it is an AI so I am verifying if this method is valid/practical or even use by any one where we use simplified truss method.
The formulae above is still valid but improved become
Ri (aka ratio of weightage) = z / sqrt(x^2 + y^2 + z^2)
Axial load = Ned * Ri/∑Ri + Mx*Ri*x/∑(Ri*x^2) (same goes to My)
Via this equation, we get a very realistic pile reaction where pile closer to column having higher pile reaction, and height of pilecap also contribute to the loading distribution.
I attached my spreadsheet for everyone easier reference.
Or if anyone have seen this method before, please share me the reference so that I can properly credit the author or strengthen the use of this approach.
