Difference between alpha and LCS rotation of a 1D member

DEFINITION

Both ‘Alpha’ and ‘LCS Rotation’ are properties of a 1D member, which allow to input an angle in [deg] to define a rotation of the 1D member’s cross-section around itself (around its local x axis).

• ‘Alfa [deg]’ is available as well in a 2D as a 3D environment.

Entering a value here has the following result: the cross-section is rotated around the local x axis of the 1D member, but the LCS isn’t.

So the direction of the local y an z axes doesn’t change.

• ‘LCS-rotatie [deg]’ is only available in a 3D environment (Frame XYZ or General XYZ).

Entering a value here has the following result: The cross-section as well as the LCS is rotated around the local x axis of the 1D member.

Remark: LCS stands for Local Co-ordinate System.

 

EXAMPLE

The example consists of 3 beams with the same cross-section. Their LCS is shown by activating the View Parameters.

• Beam B2 (in the middle) is the original one, with Alpha and LCS Rotation both = 0 deg.
• For Beam B1 (at the left) Alpha = 90 deg, while for Beam B3 (at the right) LCS Rotation = 90 deg.