I have a couple of questions concerning the rotation of singe angle members. Which command should I use to rotate these angle members? "Beta Angle" or "Beta 45" (or 135 or 225 or whatever your required angle is)? I pose this question because I would have thought the results would have been the same but they are not. The results for "Beta Angle" actually match those of an angle member modeled along its principal axis with no rotation or "Beta 0". I also would have thought the properties for the weld design, namely Sz, Sy, CH & CV, would have changed with this "Beta Angle" command since the member end forces are no longer being applied in the same manner to the weld. Any thoughts?
Local Y is the principal strong axis of an angle - the one that passes through the vertex of an equal leg angle, and intersects one of the legs at the "Apha" angle for an unequal leg angle. Alpha is published in the property catalogues.
For a member which is horizontal, and an "ST" angle is assigned, and BETA=0, the local Y axis is parallel to global Y. So, applying a load along local Y will automatically ensure that the load is along global Y too. Take a look at figures 1-9 and 1-10 in the Technical Reference manual.
You can get member forces printed in terms of global directions by using PRINT MEMBER FORCES GLOBAL LIST ... in the command file.
The same can also be set using the GUI as shown next