Problem of using section stress strain recorder

[ysir]

Dear all,

I just have problem for using the Recorder to record the element/section stress strain. Based on the manual, the command is recorder Element -file -ele # section # fiber y z <mat>
For my section model which I use fiber section and I subdivide the flange and web into many discritizations so that I can assign residual stress to each element. In this case, how should I define ele section and fiber y z and mat #?
I have tried compare the stress-strain curves from four flange tips which will be like this (-ele 1 -section 1 fiber <d/2 bf/2> for top right flange, <d/2 -bf/2> for bottom right flange and so on for the left top/bottom flange. If I understand correctly, it is how to get the strain-stress at four flange tips.
However, I have found out that the initial stresses are different for all four of them which I dont really understand why is the reason for this. Since I have assigned the same initial stresses at these four locations.

Hence, I would like to know that the my way for inputs for this command is correct and the possible reason that I have different initial stresses? (one possible reason I guess is that the analysis results does not start from zero load.......)

Thanks,

[fmk]

it might be because the recorder is recording the results after the first analysis step .. if you have loads and section is being deformed even if no loads are present because of your initial stresses.