Hi,
the results for the vertical axial forces N1 in the Plaxis 3D model of a vertical large diameter shaft are shown in the following picture, as well as the deformed shape obtained for the plate elements and the indication of the axis orientation.
All the N1 results are positive, which means, according to the Plaxis manual, that all the shaft structure is subjected to tension. Am I right?
Now, given the deformed shape, I would expect the structure to be in compression… So why are the axial force values all positive? Am I missing something on the signals of the forces or is the tension real? How can I be sure if the results indicate tension or compression?
Thank you,
Francesco
This is one of my favorite topics, so I jump in:
Your local axes etc. seem correct. So, yes, you have tension on your structure. Deformation profile also supports this. Look at the bottom of the shaft. It is lifting up. The reason might be various, not easy without looking, but usually water is responsible for these. But, in your case, it does not look normal.
I just opened a shaft model, here it is.
My suggestion: Try couple of things, try what might be going wrong, and until you get the proper response, reduce your meshes, it will take too much time.
Thank you Berk.
The model has already been validated and its behaviour is ok. The lifting of the base is due to the ground decompression. Looking at the deformations and at soil displacements, apparently there is no reason to have tension, all the shaft should be in compression.
But after a careful analysis, looking at the phase displacements, I came to the conclusion that the tension should be determined by the sequential construction process.
Nailed it! Plaxis is wonderful!
Francesco Cavalieri said:Looking at the deformations and at soil displacements, apparently there is no reason to have tension
I don't precisely agree with this statement.
Francesco Cavalieri said:ension should be determined by the sequential construction process.
And I am not sure if I understood this.
You have tension and upward movement at the bottom. Hope you have reached a safe conclusion.