SimCenter Forum

Hi Ahmet,

Glad the solution worked! Thank you for sharing the details. We greatly appreciate your warm interest and support. Your examples and feedback would certainly be of tremendous help to us and future users of quoFEM.

Best,
Sang-ri

Hi Ahmet,

Indeed it is strange that the tmpSimCenter.params file is also empty.

One possibility is that it could be related to the onedrive sync. We were able to reproduce the error (i.e. the two empty files) with an "online-only" sync option and offline environment, which I again presume is not your case . But it might be a signal that the issue is related to the fact the input files are located in the onedrive folder.

Can you please try locating the files in a different directory and let us know the results?

Best,
Sang-ri

Virtual office hours with UQ developers at the NHERI SimCenter

Anyone who wants to talk with the UQ developers in the SimCenter, Dr. Bangalore Satish Aakash and Dr. Sang-ri Yi, is welcome to drop by at the weekly UQ developers’ meeting.

If you would like to

• get hands-on troubleshooting guidance
• discuss topics about UQ in natural hazard applications
• give ideas to improve quoFEM (ranging from the graphical user interface to backend algorithms)
• discuss details of the UQ algorithms in SimCenter tools
• suggest a new feature, especially if you would like to shape the idea together with the developers
• learn how to plug in a UQ algorithm into quoFEM

or if you have any questions that are related to quoFEM or UQ capabilities of the other SimCenter tools, you are invited to visit. You may think of it as an informal office hour.

Time: Every Friday 12 - 1pm (PT)*
Zoom meeting link: click here (Passcode: 012345)

* Any cancellation will be announced by updating this post. Unless otherwise announced, we will be there every week.


Update: The office hour on 05/20/2022 is canceled
Update: Zoom link updated on 08/21/2022
Update: The office hour on 11/04/2022 is canceled
Update: The office hour on 12/16/2022 is canceled
Update: The office hour on 12/30/2022 is canceled
Update: The office hour on 08/25/2023 is canceled
Update: The office hour on 11/10/2023 (Veterans Day) is canceled
Update: The office hour on 11/24/2023 (Thanksgiving Holiday) is canceled
Update: The office hour on 12/15/2023 is canceled
Update: The office hour on 12/28/2023 is canceled
Update: The office hour on 01/19/2024 is moved to 1-2 pm (PT), same day
Update: The office hour on 02/02/2024 is canceled because the developers are participating in NHERI Computational Symposium
Update: The office hour on 02/16/2024 is canceled
Update: Zoom link updated on 04/18/2024
Update: The office hour on 04/19/2024 is moved to 1-2 pm (PT), same day

Also to fix the NO VALID PYTHON error, please go to the preference and check-uncheck the three custom options inside the "external applications" box. It will update the python and other paths. This is a known issue that we are investigating.

Sang-ri

Hi Rashad,
Please see the below:

(1) What does the 'Main' and 'Total' mean, and what is their relationship?
Both are Sobol sensitivity measures that are bounded between 0 and 1. The main index only accounts for the effect of an RV on a QoI, while the total index also considered interactive effects (joint effect of RV1 and RV2 to a QoI). Consider the below two cases as an example (f and g are any functions)

• QoI1 = f(RV1) + g(RV2) : The functions of RV1 and RV2 are additive, therefore they do not have any interaction effect, so the total and main values should be the same.
• QoI2 = f(RV1) + g(RV2) + RV1*RV2 : RV1 and RV2 additionally have an interaction term. In this case, the main Sobol index will capture the contribution of only the first term, while the total index will add up the contribution of the first and the third term. Therefore, in theory, the total index is always equal to or greater than the main index.

Each RV will give the same main index values for the two QoIs, but for the total index value, QoI2 is higher than QoI1

(2) How quoFEM tool is calculating these values
quoFEM provides two different algorithms through Dakota and SimCenterUQ engine. Please check out our user manual to find references.

Dakota - user manual :
https://nheri-simcenter.github.io/quoFEM-Documentation/common/technical_manual/desktop/SimCenterUQTechnical.html

SimCenterUQ - user manual & technical manual :
https://nheri-simcenter.github.io/quoFEM-Documentation/common/user_manual/usage/desktop/SimCenterUQSensitivity.html
https://nheri-simcenter.github.io/quoFEM-Documentation/common/technical_manual/desktop/SimCenterUQTechnical.html

A very brief overview of the algorithms (Live expert tips): https://youtu.be/JC8xN5LAo84

(3) How to identify the effect of each parameter?
Based on what I observe from the figure, 'Fy' has the highest effect, and 'As' shows the least effect. All the RVs appear to have high total index values compared to the main values, which implies significant interaction effects; however, seeing the scatter plot, it seems like you have enforced some responses to be zero and it could have created an illusory interaction effect. This could incorrectly reduce the main index and increase the total index. I will discuss this again in the next question.

(4) How to set the boundaries of parameters?
The parameter bounds are determined either based on (i) your knowledge of the uncertainty in each parameter or (ii) bounding requirements for your analysis, e.g., for an optimization problem.

One caveat
Based on what I observe from the figure, your response in some cases is zero (possibly the opensees analysis is not completed or converged). If it represents the collapsed cases and the zero values physically represent infinity, the Sobol values estimated using zero outputs are incorrect.
However, when infinity output is directly presented, it is not feasible to estimate the Sobol index. Sensitivity analysis necessarily decomposes the output variance, therefore, the variance must be a finite value. So it is impossible to get the overall sensitivity that covers both collapsed and non-collapsed cases. What we can suggest is:

• If you are interested in only stable (converged) responses, you would want to adjust the bounds of RVs so that all the output samples are located in the stable domain (so that all responses from opensees are real non-zero values)
• If you are interested in identifying factors that affect the most when deciding if the model is collapsed and non-collapsed (classification problem), you might want to set the QoI to be 0 or 1 for converged and non-converged cases, respectively. In that case, continue using the Dakota engine as it works better than SimCenterUQ for discrete outputs.
• You might want to consider changing your QoI values to those that don't go to infinity but give you a good indication of the system response.

PS. The new version of quoFEM is released on Nov 12, 2021

Sang-ri

Hi Ashok,

We appreciate your interest in quoFEM and the question!

Yes, quoFEM can be built on Linux, so the required parts are already there on github, but we were not yet distributing the pre-built executable through our website.
But we can. We will upload the Linux distribution of quoFEM as soon as possible and update it here once it is available.

(Please make sure you have email notifications enabled so that you are notified when we post here I think by default it is on)

Sang-ri

Hi Rashad,

Thanks for sharing the screenshots. The quoFEM inputs in your first screenshot look good. For the workdir.1-300 folders, probably you will see the files inside from windows explorer, but not from the quoFEM browser shown in the second screenshot (because it is showing you only folders and not files).

I think the opensees model is either not converged or giving only zeros for all input parameters. We can have a look at your input files if you could share the tcl files.