Nonprismatic steel section Etabs Vs Sap2000

[Yazan Atoum]

Hello,
I just converted a steel structure from Etabs to Sap2000, I have checked everything and the results almost matching, however when I specify nonprismatic steel section, I find a significant difference in moment value between the two models. Can anybody help?

Using Sap2000 version 26
Etabs version 22

 

[271828]

Few people have both programs. You might get more responses if you describe an example problem and report the results from both programs.

Also, can you use a classical closed-form solution to let you know what the "correct" answer is? I'd always start there with a situation like this.

 

[JoshPlumSE]

By nonprismatic, you mean something like a tapered wide flange, right?

I'm not sure where the issue could be as I don't know enough about your structure to do my own investigation. But, I have a few quick thoughts..... Some of these are a bit obvious. I'm not implying that you haven't done these already. Rather, I'm saying this is my "investigation" thought process for something like this:
a) Make sure the geometry and member properties are really the same.
b) Make sure the loading is really the same.
c) If you are considering geometric non-linearity, take that out and do just a linear elastic analysis and see if the results are the same. If so, then we'd want to look at all the various non-linear settings as being the source of the difference. If they linear elastic results are the same then we'd probably look at how the tapered members are "meshed" in each program.

d) In general, when I do this, I like to make my "investigation" model as small as possible. Ideally, if I think the issue is with tapered members, then I want to have model that has a single tapered beam or a single tapered column.