Rotation of Angle Members

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?

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  • 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.



  • I have noticed that after changing "Beta angle" to 45 degree to make legs a of equal angle parallel to global axis es, sectional properties of angle sections like Iy, Iz remain same and I think, it is because by specifying angle beta, we have rotated the locale co-ordinate system "as a whole" . However since my loading is parallel to vertical global Y axis, I have to use sectional properties (Iz etc.) of the angle in a local co-ordinate system whose Y axis is parallel to global Y when legs of the angle are parallel to global axis es. How to proceed in this case?
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  • I have noticed that after changing "Beta angle" to 45 degree to make legs a of equal angle parallel to global axis es, sectional properties of angle sections like Iy, Iz remain same and I think, it is because by specifying angle beta, we have rotated the locale co-ordinate system "as a whole" . However since my loading is parallel to vertical global Y axis, I have to use sectional properties (Iz etc.) of the angle in a local co-ordinate system whose Y axis is parallel to global Y when legs of the angle are parallel to global axis es. How to proceed in this case?
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