Hi
I modelled a circular shaft in Plaxis 3D using Mohr Coulomb solid elements since the shaft is to be an unreinforced slurry wall (hence it would not have a decent tensile capacity). I am looking for a way to extract moments and axial stresses equivalent to those i can get from a plate element. I have considered the following options:
- embedding a dummy plate with reduced stiffness. The problem of this solution is that the options available for plate elements are limited to linear elastic or elastoplastic plates (which assign equal strength in tension and compression). Using a linear elastic element or an elastoplastic element whose strength is yielded by the compressive strength will result in a behaviour where the solid element has cracked in tension while the plate element has not yielded so the extracted forces and moments will be wrong.
- modelling the shaft via a plate element but the problem again rises from the limited options for plate elements. If there was an option for an elastoplastic plate whose compressive and tensile strengths can be independently specified this would help
- manually integrating along the cross-section. This is really hard to do across the shaft. The circular geometry makes it much more complicated (and the incapability of defining cylindrical coordinate system). The cross-section feature in plaxis only averages the normal and shear stresses across the cross-section (so although i might be able to get a normal stress, getting the moments will not be possible via this feature).
Would you please help/advise?
Thank you very much!
HIDid anyone think about a solution to this issue? The problem is really more general than the specific case i talked about. In simple words, is there a tool in plaxis (or external) that allows for the conversion of solid stresses (modeled with a material different than the linear elastic model) into structural forces and moments (given a certain section)?
Thanks
Dear Omar,
I would use the dummy plate approach provided that the cross-section of the shaft does not change.
Note that you should not use equivalent properties to the plate element as then you would consider the stiffness of the concrete twice.
Please check the general approach as explained for a different example but still relevant: https://communities.bentley.com/products/geotech-analysis/w/plaxis-soilvision-wiki/52506/composite-liner-approach-in-plaxis-2d
Therefore, you should not worry about how to define different behaviour in tension and in compression which is not yet implemented for the plate elements. The plate would simply follow what the volume elements would do.
Integration along the cross-section indeed can be a time-consuming task to do, but PLAXIS allows for automation with Python scripting so, if you are performing this type of analysis often, it is worth the time spent to learn Python and implement a solution.
Note that if Mohr-Coulomb is not covering your case, you can consider using the advanced Concrete model: communities.bentley.com/.../concrete-model