Hi,

I made attempts to submit some technical questions to the Plaxis support, and it directed me to the Bentley Connect Centre-Service Request Manager, where I was confused that I do not know what product category Plaxis belongs to. Anyways I filled in some random selection on the questions, and made my main query in the Details section, hoping it will arrive to the correct expert and receive some prompt response.

However, this platform seems a good place to paste my questions. See below.

I am simulating a vibrating pile with both static and dynamic load applied to the pile. I have read/understood relevant chapters in Reference manual and Tutorial manual, but still find myself puzzled.
My engineering project and questions encountered are described as below:  
inputs:
Static load per pile = 55 kN
Dynamic load per pile = 1750 kN
Driven tubular steel pile with :  Pile diameter =0.9m & Steel thickness =0.02m
Plaxis model= axisymmetric model & 3D model

Questions arisen from this analysis in the axisymmetric model  (Q 1& 2) and 3D model (Q3):
1: vertical load input for pile in the axisymmetric model is inputted as kN/radian. i.e. static load= 55kN/(2*pi()) & dynamic load=1750 kN/ (2*pi())
Is it correct?

2: From the output, axial force in the pile = output result *2 * pi()  (according to manual)
From the inspection of axial force in the output:
At top of pile (immediate below the applied load), N= -8.75 kN/m* 2 * 3.14= -55 kN/pile, which equal to the static load input

At the top of pile (immediate below the applied load), N= -624 kN/m *2* 3.14= -3920 kN /pile (at the step maximum amplitude is applied), which is not correct, more than double of the input load.

Why does this happen? What have I done wrong?

3: Apart from this 2D Axisymmetric model, I have also created a 3D plaxis model with same design input, and calculated 1 second for dynamic loading and compared the results(aim to validate each other between 3D and 2D before going into big simulation effort). Applied the pile load as a circular line load around the pile top= kN / (pi()*D), D being the diameter of pile. We would expect the results from 2D axisymmetric and 3D very similar, but it appeared result is not very consistent. Especially the axial force of the pile, pile movement, and excess pore pressure around bottom of pile.
Any thoughts on why these two models produce non-comparable result?

Thanks in advance. 

Regards,
Dan