07-11-2010, 03:41 PM
In ETABS the PM curve is generated for the each cutting plane of the member in the cross section. For example, if you have square concrete column. Etabs will generate a 3D profile of PM curves. The first curve will be generated for the angle = 0 (horizontal). At that time the rebar on the right side and left side will be in maximum tension and compression. Next it will increase the angle to next interval (for example 20 degree). In that case the cutting plane is not a horizontal line, but it will be a line drawn at 20 degree with horizontal and the rebar at ends of this line will be in compression and tension.
In short, if you have just a moment on your column in x axis then you need to check 0 degree result and if you have moment in only y axis then check 90 degree PM curve. If you both (bi axial moment) then you need to check all the angle to make sure your moment is within the PM curve of all the angles.
I know this sounds really confusing, but I would say the second paragraph above should answer your question. If not, don't hesitate to write me back.
In short, if you have just a moment on your column in x axis then you need to check 0 degree result and if you have moment in only y axis then check 90 degree PM curve. If you both (bi axial moment) then you need to check all the angle to make sure your moment is within the PM curve of all the angles.
I know this sounds really confusing, but I would say the second paragraph above should answer your question. If not, don't hesitate to write me back.