Finite Element

The beauty of Streamlit with Plaxis is the simplicity of the UI and how minimalistic it looks. Also, the 2x2 output figure for a retaining wall is the most compact output you can imagine. Everything you need to show for all these stages is inside one figure. Moreover, this tool can deliver a really detailed excel sheet to share with other designers. Watch the video to see it on action: Also fixed-end anchors and node-to-node anchors! And lastly, how to start the Streamlit directly from Plaxis as shown in videos: ...

Update on the Post (13/10/2022) New update of the Plaxis, partially, solves the problem mentioned in the post below. Now, if you define a manual tensile strength, this will be reduced during safety analysis. But if you rely on the tensile strength automatically calculated by Plaxis, it will not be reduced and same problem continues for that case, in my opinion. But at least, for the users that are aware of this distinction, there is an option to correctly use Hoek-Brown model. See the note on Plaxis ...

Recently, I have prepared a Moment-Axial Force Interaction Diagram that fetches the structural forces from Plaxis automatically. Using the amazing Streamlit module, I have created a simple GUI for MN diagram and published its video in Linkedin. The response was amazing and I got a lot of questions regarding the procedure, Python-Plaxis connection and Streamlit. You can see the video here. I will not publish the code since it will require me to check every aspect of the code, do extensive tests and prepare a documentation. Instead, I want to give some insights on the methods that I have used in the code. I had to try and fail too many times and contacted Plaxis support several times. Since this is a gray area still with lot to develop, it is not easy to find discussions on the internet, so even a brain-storming with Plaxis support is really valuable. (Thanks to Stefanos) So, to create a record of these functions, I will share small gists (a little code snippets sharing tool by Github.) ...

There was a question regarding Plaxis in Bentley forum: A user asked the following question -paraphrased-: When we changed the plate parameters to simulate long term stiffness, there is no change in deformations. Is there something wrong? I have tried my best to explain this in the forum, but it is not an isolated case. In fact, there are many examples of design reports that do not take this into account. For example, changing the plate parameters from shotcrete to final lining is not a correct approach to simulate long-term degradation of the temporary lining. Why are deformations not changed when we changed the stiffness of structural elements? There is a clear explanation for that: Because finite element method does not work that way. As can be seen below or in Appendix of Scientific Manual of Plaxis, the incremental deformations are caused by unbalanced load. If there is no unbalanced load, the deformations will not increase since the equation results in 0. But let’s consider a tunnel. As you can see below, the real case is in first row. If we want the ground loads to act on the permanent lining, we can’t just change the material properties and hope for the best. We have to simulate the degradation of the temporary lining. There are several methods for this such as gray rock or assuming a certain thickness of shotcrete thickness is degraded. However, some project requirements do not allow for the consideration of temporary lining for permanent lining analyses at all. This is the case for subway projects in Turkey. In the second row, you see the wrong way of using plates for tunnel design. If we use this method, structural forces will be less than actual. Why? Let’s remember few things and consider the above case of wrong use of plates: ...

For underground structures, a rough but reasonable simplification is pseudo-static deformation method. In this method, we apply seismic strain which can be calculated as the ratio of effective PGV (Peak Ground Velocity) to effective shear wave velocity. $$ \gamma = \frac{PGV_e}{VS_e} $$ Effective PGV can be multiplied with depth dependent reduction factors (see FHWA-NHI-10-034) and maximum shear wave velocity obtained from geophysical tests with almost zero strain can be converted to effective shear wave velocity based on recommendations of FHWA or Eurocode 8. A simple Python code can be written to implement lateral deformation profile in Plaxis to simulate seismic loading. If you locate this Python file inside the Bentley folder (< PLAXIS installation folder >\pytools\input) this can be directly called from Plaxis Input. ...