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?
Although you cannot change local axes for angles and align it with the geometric axes but you can always orient angles so that the legs are aligned with the global axes. This can be done using the beta angles. Loads can also be applied along the global directions for the scenarios where your angle legs are aligned with the global axes. For angles which are inclined to the global planes you would need to resolve the load in the global directions and apply it that way. As far as design of single angles is concerned, design as per geometric axes is only allowed for certain limited cases whereas you can always design single angles based on principal axes as that is the more generic case. In addition, our design code implementations are equipped to automatically check if the member can be designed as per geometric axis or not and if so, design as per both principal and geometric axes is carried out. I am specifically referring to the AISC 360-16 specifications here but I believe other international codes also impose conditions on design of angles as per geometric axes as well.