Parameter IDUCT

Hi all,

I have a question about parameter IDUCT for frame member. If i chose 0 or 1 the behavior is quite difference....
How can I decide about one value or the other?

Thanks

When IDuct=1 the stiffness of you member changes to keep yielding curvature constant when your yielding strength changes (e.g you have varying axial load on your member). Even though this type of analysis is not very common, this is supposed to be the true behaviour of reinforced concrete members (have a look to section 4.4 of the book "Displacement-Based Seismic Design of Structures" by Priestley et al.). As I said though, I don't think this feature is very common in NLTH and I am not aware of any other lumped plasticity program (beside Ruaumoko) that implements it. I guess it is because it is not very easy to be implemented (but I might be wrong)..
How different are results? are both cases realistic, or you suspect some problems of convergence or similar when Iduct=1?
To choose between Iduct=1or0 I would quantify the expected variation of axial force on the member during the analysis and then perform sectional analysis to see how much the stiffness of my member is expected to vary. After this I would go for Iduct=1 only if strictly necessary, but this is just my opinion.

Let me know how it goes..

Thanks Domenico,

the axial load on members doesn't have high differences during the analysis, so I decided to use IDUCT = 0

But then why was there big difference of results in the first place?
Is IDUCT=1 not working properly or the error was somewhere else? It would be good to know for future reference..

There were some differences in terms of Moment-curvature diagrams, clearly. With IDUCT=1 the maximum curvatures were lower. In terms of global quantities, i.e. story forces, the values were more or less the same.

Thanks again