Question about nonlinearBeamColumn

[mi.damato]

Hi everyone!

I want to study the properties of nonlinearBeamColumn. For this purpose I used a simple cantilever pushover analysis downloaded from OpenSees script library without axial load. I used square section modelled by concrete01 and steel01 fibers. I tested it using 3 and 5 integration points.
I obtained the following results:
$numIntgrPts=3
-curvature function: it was linear until steel reinforcing yielded. Then it became non linear along the cantilever
-moment function: for each step was alway linear function along the cantilever.
I was not surprised of these results.
On the contrary, the results with 5 intergration points pointed out:
$numIntgrPts=5
-curvature function: it was for each step always non linear function along the cantilever
-moment function: it was for each step always non linear function along the cantilever
For the analysis carried above I used nonlinearBeamColumn with non iterative method.
So I thought that this was the reason why analysis with 5 integration points did not appear a moment linear function.
Hence, I used nonlinearBeamColumn with iteration method. I tested it by using $maxIters=10, 1000 with $tol=10e-16 (default value) and $maxIters=1000 with $ tol=10e-25. The results obtained were the same of those obatined with non iterative method for foce formulation.
Why? Is it normal?

Thanks in advance

P.S. I am using OpenSees 2.0.0. for windows