Displacement Based Fiber Frame Element

04-Unexpected behaviour/errors
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seismosoft
Posts: 1093
Joined: 06 Jul 2007, 04:55

Re: Displacement Based Fiber Frame Element

Post by seismosoft »

In the SeismoStruct support page, you will be able to find plenty of information on the program:
https://seismosoft.com/support/seismostruct-support/
In particular, the technical information sheet includes information on the formulations employed in each element type.
You may also find similar information in the User's manual and the help of the program.
However, I reiterate that the discrepancies are probably attributed to other reasons and not the formulation (e.g., materials, sections discretisation, structural modelling). If you carry a search in Google for 'SeismoStruct vs. Opensees' you will find several publications that provide very similar results between the two programs.
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aaparker
Posts: 9
Joined: 21 Jul 2022, 14:26

Re: Displacement Based Fiber Frame Element

Post by aaparker »

Sir, Thank you. I found the references.
Here is one study I saw, a professor of mine's student did the research.
So many of the results are similar,
Only in a few, there are different results, although they concluded they are similar (this is my observation).
https://web.itu.edu.tr/bariserkus/pdf/O ... Thesis.pdf
Please look at figure 6.48, 6.51 and 6.52.
You can translate it with google translator (Turkish to English - document option)
Also, when I do an anaysis with OpenSees and Seismosoft (as I mentioned) results are a little bit different.
Please look at first step. They are similar (Node2, X direction). Then results are not so similar. I can send you model files.

Seismosoft
Output-No. Load Factor
2 0.100000
Nodal Displacements
1 0.0000E+000 0.0000E+000 0.0000E+000 0.0000E+000 0.0000E+000 0.0000E+000
2 3.5115E-001 0.0000E+000 -7.3980E-003 0.0000E+000 5.2686E-002 0.0000E+000
Output-No. Load Factor
11 1.000000
Nodal Displacements
1 0.0000E+000 0.0000E+000 0.0000E+000 0.0000E+000 0.0000E+000 0.0000E+000
2 7.8687E+000 0.0000E+000 -5.1972E+000 0.0000E+000 1.3084E+000 0.0000E+000

OpenSees

0.351694
1.19817
6.53052
13.4288
20.4161
27.4077
34.4016
41.3959
48.3903
55.3847
User avatar
seismosoft
Posts: 1093
Joined: 06 Jul 2007, 04:55

Re: Displacement Based Fiber Frame Element

Post by seismosoft »

Hello aaparker,

Obviously we cannot comment on the results and the exact source of the differences ,and a thorough study needs to be carried out to check all these (unfortunately we do not have the resources or the time to do it).
I re-iterate however that probably the differences are attributed to different modelling strategies by the user (selected material models, section discretization, possible differences with the inclusion or not of the mass or the self-weight), rather than differences in the element formulations in the two programs.
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User avatar
seismosoft
Posts: 1093
Joined: 06 Jul 2007, 04:55

Re: Displacement Based Fiber Frame Element

Post by seismosoft »

Aaparker,
Note in Figure 6.47 in the report that you sent us the differences in the concrete material model hysteretic rules, which is one of the sources of the difference in the results.
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aaparker
Posts: 9
Joined: 21 Jul 2022, 14:26

Re: Displacement Based Fiber Frame Element

Post by aaparker »

Sir/Madam,
Please get me honest. I am just writing for if there is a bug. Thank you for your comments. Really, honestly, if there is something wrong, I wanted to tell it. I did the formulation by myself in matlab years ago. I compared with Seismostruct (years ago), and see a little difference. I had no real time to compare exactly Seismosoft. Now it came to my mind and wrote to you.
After writing you, I made OpenSees and Seismosoft models (since OpenSees was same with mine). I know, it is not easy to make one to one comparison. I am afraid if there is a problem or not. If you are sure, no problem.
Hope you best
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seismosoft
Posts: 1093
Joined: 06 Jul 2007, 04:55

Re: Displacement Based Fiber Frame Element

Post by seismosoft »

aaparker,

No! To the best of knowledge, there is no bug in the infrmDB element type! Please stop claiming that.

The element has been programmed almost 20 years ago, it has been extensively tested by literally thousands of users and it has been proven correct and accurate in numerous blind prediction contests, winning many of them. Note also that in every new version of the program we carry out hundreds of analyses, in order to check it and guarantee that there are no bugs or other problems in the software.

It is not fair to ask repetitively and claim indirectly that there is a bug in SeismoStruct. We explained patiently the sources of differences between Opensees and SeismoStruct, but you simply chose to ignore them. Without checking what you have done, you came to the conclusion that probably there is a bug. And you did not consider the fact that SeismoStruct has been thoroughly checked up to now, contrary to your formulations and to your models.

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seismosoft
Posts: 1093
Joined: 06 Jul 2007, 04:55

Re: Displacement Based Fiber Frame Element

Post by seismosoft »

I thus urge you to do the following, before coming back with another similar unsupported accusation:
1) Read thoroughly the Verification Report, in particular the dozens of model that employ the infrmDB element.
2) Search the web and find the dozens of publications that compare the two programs. You will
3) Check the sources of the differences between your two models in Opensees and SeismoStruct. Both programs provide very good output, for instance SeismoStruct even outputs stresses and strains at the monitoring point level.

If you find something solid about a problem in SeismoStruct, let us know about it. The fact that you do not get the results that you expect however is not something solid by itself.
Seismosoft Support
aaparker
Posts: 9
Joined: 21 Jul 2022, 14:26

Re: Displacement Based Fiber Frame Element

Post by aaparker »

I told, If you are sure, no problem.
You are not understanding what I am telling.
Also, you say, do not come again. Are there hidden rules about forum?
This is not a question and I do not need answer.
I told.
If you are sure!
No problem.
Interesting!
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