I have some questions regarding the attached model image,
1- In plaxis 3D, when a prescribed displacement is applied above a quarter pile modeled as a plate, then should the reaction force (Fz) be multiplied by (4) to get the total reaction force for the whole model ?
2- The prescribed displacement is applied in Z-direction, so should the displacement in X-direc. and Y-direc be fixed ? or is it ok to keep them free ?
Thanks for your support.
Hi Toshiyasu,1. In quarter symmetry, the load needed for the quarter-symmetric model to get the same displacements as in the full model is 1/4 of the full model. So, indeed, if you use displacement control and apply prescribed displacements in the quarter-symmetric model, you must multiply the reaction force by a factor of four (4) to get the correct value as in the full model. When in doubt, I would start with half symmetry to understand things.2. The two axes of symmetry coincide with the boundaries of the model. So, it is unnecessary to manually fix the edges of the plate, as they follow the default boundary fixities (normally fixed). You can review those fixities in the Model Explorer by clicking on the Model conditions > Deformations.
Answer Verified By: 三好 俊康 Toshiyasu Miyoshi
Thank you so much for your answer.
I got the point, but I have an additional questios regarding the model.
1- The above model includes around 36000 elements, and therefore the analysis run takes more than 1 day with more than 5000 steps, so is there a way to reduce the required time of the analysis?
2- Plaxis 2D was used for generating the same model as the attached below image, but the reaction force of the 2D analysis is around 750MPa, but the reaction force of the 3D analysis is around 1000 MPa, we do not expect such a big difference between 2D and 3D results, is that right or it is normal to have such a difference ?
Hello,
I hope I can get an advice regarding the above 2 points.