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.
RSTAB Main Program
RSTAB 8.xx

Main Program

The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions