FAQ 000235 EN

Modeling | Structure RSTAB

How can I rotate a cross-section (IPE 270) set in 2D mode by 90° so that it can be loaded about the minor axis? When I try to rotate the section by 90°, an error message appears.

Answer

When entering models in the two-dimensional space, only section rotation angles of either 0 or a multiple of 180 are allowed. This is because the direction of the local axis system in the member (x-y-z) is clearly defined and specified. Moreover, only the member internal forces My and Vz are calculated for 2D structures.

The major axis of the cross-section (y-axis) in the 2D space is always oriented in the direction of the global Y-axis. The minor axis (z-axis) are not considered (as if it was completely undisplaceable).

In case of the cross-section rotations allowed, biaxial bending could occur since loads in the 2D space can only be defined in the X-Z plane. However, the resulting Vy, T and Mz portion would remain unconsidered. This is the reason why only those cross-section rotations are allowed for which the section local z-axis is directed to the X-Z plane.

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