I have plotted the axial pile load versus pile length for piled raft by PLAXIS 2D software.
Load - UDL - 200 kPa
Domain -200*80
Clay soil Cu = 80 kN/m^2
Es = 20 MPa Epile ,
Eraft = 20 GPa
Analysis- linear Elastic Element - 6 noded
Raft 42*42 m
Raft thickness 2 m
Pile diameter 1 m
Pile length 10-40 m
Pile Spacing 4m
Bg = width of group of pile
Br = Width of Raft Bg/Br = 0.2 then Bg = 42*0.2 = 8.4 m within this length 3 piles are installed
I am getting certain trend for the above curve but that is not matching with normal trends.
In normal trends top resistance of pile is more than bottom or base resistance however in my case i am getting opposite trends.
I'm not sure if Plaxis is calculating what percent of load applied to the pile, but if you want to know output (internal forces) of piles, you can simply double clicking on the "Plate" if you define your pile as plate on the "output tab" after calculation
Hi Mali,
In principal, it is very possible to calculate the percentage of load carried by piles and raft. One of possible ways is:
1. You know your applied loading, i.e = 1000kN (assumption)
2. Make sure your pile element has been assigned interface elements along the skin and the toe of the piles. Also, you need to assign the interface elements below your Raft foundation.
3. After finishing the calculation, you can double click the interface along your pile and check the shear stress (tau in Greek). Then, you need to multiply this shear stress with your pile periphery and get your pile skin resistance.
4. The same manner is applied to check the pile toe resistance and raft resistance, but the output of normal stresses are used instead of the shear stresses. Of course, you need to multiply those stresses with the contact surface area of your pile toe and raft in order to get the loading acting on those elements.
5. Output = Skin resistance + toe resistance + raft resistance should be equal to 1000 kN (external loading)
6. Finally, I believe you can calculate the distributed loads by simple math.
I hope it is clear. Good luck.
Best,
Aswin
Dear Shivanand
As far as I know, you can obtain the axial forces of piles in a pile group and thus by dividing the total applied load to those numbers you will end up with the solution.
Regards,
Aswin Lim i read your comment in detail... in plaxis when i click interface of raft and select normal stresses... the stress varies along the raft interfaces.. which values should i take? because if i take maximum value than it may give more than the applied load....note... i am working on piled raft
i will be very thankfull to you response
What value of EI & EA did you use? Can you share a screen shot of your input parameters? Did you model the pile as a plate element?
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