Hi, I'm making a base for a lattice mast in Plaxis 3D. The foundation takes the loads from the mast at four points.What is the best way to make bending moments Mx, My, Mz at all points?
Hello Nina,
If you consider it works like a beam (long elements) to extract its bending moments, you may use "dummy beam" approach, which is similar to the " dummy plate" shown in the link below:communities.bentley.com/.../composite-liner-approach-in-plaxis-2d
The bending moment must be transmitted from the mast to the foundation at four points. This is is not possible directly with the soil element. My first thought was a dummy plate on the top or force couple. Am I wrong? Please explaine the dummy beam option.
I think I was confused your original question. You are interested in input moments, not output (but it is better to mention moments instead of bending moments as input loads since it can cause bending and torsion and make confusion).
A plate cannot sustain torsion, you may use a plate and dummy beams (which has small stiffness) on the plate (e.g.: use two cross the dummy beams on the your plate above) and now, you can apply these moments at the center point of the plate.
Answer Verified By: Nina Shepel
Thank you for the answer. I have one more question. What should be the thickness of the plate and beams compared to the surrounding volume , if the top part of the foundation is a cube 2,5m x 2,5m x 2,5m.
Hello Nina,Since stiffness of dummy plate or beam is very small, its thickness does not have much impact but e.g. 10 or 20 cm to be fine.
Thank you for the answer!