Modelling of columns subjected to large axial force

[IlanildoDias]

Hello everyone.

I have some questions, I would appreciate it if you could help me figure it out.

I am looking into the performance of a 4-, 8- and 12- Story Chevron brace frame. I have some questions about the modeling of the columns. For the 4 story system, I used 1 force-based beam-column element to model the columns and this was sufficient to capture the axial force-bending moment interaction present in the column.
However, for the 8- and 12-story systems, the axial force present in the column is very large, while the story drift is relatively small. For these cases, the axial force-bending moment interaction is not being captured and the columns develop large bending moment capacity, larger than expected, and therefore the story shear is very large. I did some parametric study where I discretized the column into 2, 4, and 16 displacement-based beam-column elements, to see if the column response would change, but the outcome was similar to the 1 force-based beam-column Element.

Any idea on what can I possibly be doing wrong?

I would appreciate any help on how to accurately model the columns.

Kind Regards

Dias

[selimgunay]

How are you modeling the braces and beams? If you have them elastic, that may be the reason of large axial forces.

[Kearsh]

Hi i want to know the answer too .did you find a appropriate meterial to simulate the brace?