Seismosoft | Earthquake Engineering Solutions

Hi
i'm trying to carry out an IDA , So my objective is reaching the global collapse of the structure "R.C Framed structure", but some times i have a problem with the convergence "fbd-ite" message , according to the note in the manual "p28-decrease the number of integration section to 2-3,in the inelastic force based element (2 section is not allowed)".

So i have divided the structural components "beams and columns " to 4 elements each one has 3 integration sections , and i have unchecked the option:
"Do not allow element unbalanced forces in case of fbd_ite"
after that i can often reach the global collapse .
My question is There's any problem in my procedure ??
Thanks

Dear bashar,

The User Manual note you refer to does not suggest users to subdivide the structural members into more elements, but rather says that, if users have subdivided a structural member in several infrmFB elements featuring a high number of integration sections, then convergence difficulties may occur.

Hence, we would not necessarily say that the solution to your convergence difficulties is to subdivide your columns and beams in four infrmFB elements. (maybe such convergence difficulties occur because the strains in your materials are excessive, for instance, and the structure is thus collapsing due to lack of capacity to sustain imposed actions)

In any case, for what concerns your question on allowing the analysis to proceed even if internal forces convergence has not been fully achieved in some elements; if you are mainly interested in the global response of your structure, the use of such option should indeed not introduce important errors in the analysis (you can always check this by running some sensitivity studies and/or manual checks).

Seismosoft Support

Thanks Seismostruct for your answer and your help .