Hi,
I modeled a 90 ft suction mooring pile as a plate and I modeled the soil inside the pile as a very stiff material. Then I applied the design load at the padeye 58 ft below ground surface. I also created external interface around the pile.
I needed the structural forces around the anchor so I extracted the pressures on the interface every 45 degrees along horizontal using the vertical cross section option. I assumed the same pressure along each 45 degree surface and calculated the forces. Then I transferred these forces from local coordinate system to global coordinate system to calculate the total forces in x and y directions to check the force-balance in horizontal direction. Unfortunately, the forces calculated from the interface are ~15% lower than the forces applied on padeye. I even checked the force balance for another pile length and I am still getting similar type of difference.
Do you think that the procedure that I follow for extracting structural forces are correct? Should I have modeled the suction pile as a rigid body/volume pile? Do you have any other recommendations for me to check? Do you suggest an alternative way for coming up with the structural forces?
Below is the table of Padeye and interface forces. Thank you in advance.
Dear Mustafa,
I noticed you have already opened a support Case and I have already replied to you.
As I mentioned there, there are several considerations on both the modelling technique and general approach to be considered which I conveyed to you via email.
Mostly, it depends on how you model this suction pile with interfaces (allowing for slipping and gapping) and using instead of the structural results available, the cross-sections which with coarse mesh can give (extrapolated) results that are not very accurate as they go through the current generated mesh.
Finally on the question of rigid body vs. volume, that depends on the behaviour of the structure. If it is considered (practically) infinitely stiff, then the rigid body can be utilized just like our tutorial example: communities.bentley.com/.../plaxis-3d-tutorial-03-loading-of-a-suction-pile