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Thread: Problems re-importing an analytical model

  1. #1
    Revit Moderator Tom Weir's Avatar
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    Default Problems re-importing an analytical model

    Hi all,
    We exported a Revit model to ETABS for analysis. We then did a Save As to save as an EDB file type. The engineer then worked on the EDB file. Unfortunately when we tried to re-import the EDB file it could not be done.

    Then we thought maybe we could export the EDB file to an EXR exchange file so that we could read that back into Revit. No Luck....we go the message:

    <"Etabs model was modified after import from revit, it cannot be exported back to Revit">

    Are we missing something? It's not clear what the rules are for the import and export. The Help menu has nothing.

    ANybody have any idea?

    Thanks,

    Tom Weir
    Los Angeles









    "Etabs model was modified after import from revit, it cannot be exported back to Revit"

  2. #2
    I could stop if I wanted to kmarsh's Avatar
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    Default Re: Problems re-importing an analytical model

    Tom,
    I was under the impression that, once exported, you could analyze a model and re-import any member size changes but that's all. If you add members or move them around, it can no longer re-import. What exactly did the engineer do while working in the file? I'd suggest a test where you export, run the analysis and redesign the member sizes and then try a re-import with no other modifications to the model while in the analysis package. (I assume that this might also apply to loads etc... you might have to put all that stuff in with Revit)

    I'm kind of basing this on the fact that you cannot create a model in Etabs or Risa and then import into Revit, it must come from revit. So, granted that, I extrapolated the rest.

    This is certainly a topic that i'm curious about (being an engineer) but I haven't actually tested it yet.

    -ken

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    Super Moderator david_peterson's Avatar
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    Default Re: Problems re-importing an analytical model

    Hold the phone here.
    I guess I'm not even on the same planet. I haven't played with RS2 yet, but we did just buy it. It was my understanding that the only rule you had to follow was to start in revit to create the link. (ie place a column in a RS drawing and export) After that I thought you could do anything you wanted to in the Risa or e-tabs or now RAM. Load all the structural family in RS and re-import the model and accept all the changes. If this is not the case and everything but the calcs have to be done in RS, I guess my copy might be collecting some dust for a while. We had a hard enough time getting them to switch from R14 to 2002. Now they can't do any modeling, or loading in the programs they are used to using. I hope someone can explain this whole import/export thing a little better.

  4. #4
    I could stop if I wanted to kmarsh's Avatar
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    Default Re: Problems re-importing an analytical model

    David,
    Please be sure to take my comments with the grain of salt they came with. I have not tested any of what I said, such that I can draw any actual conclusions. I was only suggesting a possible cause for Tom's inability to re-import a model from Etabs. I could be completely, 100% wrong.
    I am, however, still very interested in the outcome of this discussion for obviously personal reasons as we are seriously considering buying a copy or 4.

    -ken

  5. #5
    I could stop if I wanted to kmarsh's Avatar
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    Default Re: Problems re-importing an analytical model

    Here are the results of my preliminary test:
    in RS2
    draw 4 grids,
    add 6 columns and 4- W12x26 beams.
    Export to Risa3d:
    change one member size to 30x108 and add 3 beams (one 12x26 and 2-30x108s)
    Re-import to Revit:
    See results below: 3d pic of Risa before re-import and 3d pic in RS2 after re-import.

    It looks like the 3 added beams were non-existent in the re-imported RS2 model...

    perhaps more test results when I get a few more minutes.
    -ken
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    Last edited by kmarsh; 2005-10-31 at 10:46 PM.

  6. #6
    I could stop if I wanted to David Haynes's Avatar
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    Default Re: Problems re-importing an analytical model

    If a size of beam or column is changed in ETABS, then those new sizes must exist in REVIT Structure prior to the reimport.

    Use Load Family to bring them in before reimporting from ETABS into REVIT Structure.

    Hope this helps.

  7. #7
    I could stop if I wanted to kmarsh's Avatar
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    Default Re: Problems re-importing an analytical model

    David,

    Yes, that is the expected behavior and was verified by my example. (notice that the original W12x26 changed to W30x108 in Risa3d came back into Revit as the W30x108.) So that works. However, in the example, I was not able to add any members to the dataset and re-import.

    I'll try just moving things, without adding info, next.

  8. #8
    I could stop if I wanted to kmarsh's Avatar
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    Default Re: Problems re-importing an analytical model

    Here are the results of example 2:
    In Revit:
    1. draw 4 column grids
    2. add 4-W10x49 columns and 5-W12x26 beams
    3. Load W30x108 family
    Export to RISA3D:
    1. Change one member size to W30x108
    2. Move middle beam. (not the one with size change)
    Re-import to RS2:
    1. Beam size change worked (of course)
    2. Beam move did not.

    Now I'm wondering if changing the size of the beam that moved would change the size back in revit... OK, changing the size of the moved beam, does translate back to Revit but Revit still does not reflect the move.

    On one hand, this behavior could be beneficial to the engineer who might need to line some things up in the analytical model but still want the sized to translate and not move in Revit. However, it also means that engineers will need to do most of their work in RS. (Personally, I don't understand why engineers wouldn't WANT to work in RS. In order to move to BIM, we have to get out of the "engineers engineer and drafters draft" the lines MUST blur to take full advantage of BIM)

    I also added some loads in RISA3d which did not translate back... Interesting, however that there were pre-defined load cases when I got to RISA3d (ostensibly exported from RS...)

    Has anybody else been doing any experimenting?
    -ken
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  9. #9
    Revit Moderator Tom Weir's Avatar
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    Default Re: Problems re-importing an analytical model

    Hi,
    Thanks for your interest in this subject and for taking the time to experiment with it. There does not seem to be any documentation to explain what is going on....I am going to ask the Revit Structural Product Manager to help us flesh this out. Not being an engineer I am a bit over my head here. But as you were saying we engineers and draftspersons need to break our old habits and work more closely in RS.

    I also thought (and have been told) that you could make one column in RS, export to ETABS (or whatever), and create members there. Now we seem to be finding severe limitations on that.

    Let's see what more we can find out from the developers.

    Tom Weir
    Los Angeles

  10. #10
    I could stop if I wanted to kmarsh's Avatar
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    Default Re: Problems re-importing an analytical model

    Agreed. This may also be a limitation of the particular package to which you (we) are exporting. My understanding is that the amount of information returned is in some ways dependent on the 3rd party. For instance, Etabs returns more information per member than Risa 3d does. Things like end reactions etc. So, this may be more an issue of what features the 3rd party vendor took advantage of. There also may be some time-travel type paradoxes in re-importing new or changed info from an analysis package: lost or broken relationships, and that kind of thing. I haven't thought through that far enough to determine if it makes any sense but just wanted to throw it out there.

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