Effect of fibers on stress

[Heady]

Hi,
I was studying the stresses in the sections of a beam. The stress-strain outputs changes with the number of subdivisions ( fibers ) in the section.
How can I know at what number of subdivisions ( fibers ) the outputs will be correct ?

[fmk]

what element type?

[Heady]

I used nonlinearBeamColumn element.

[Heady]

LindaBPolk, the beam I was studying is a rectangular beam, which is a part of a fixed suport portal frame. The section of the beam is uniform i.e. no reinforcement is used.