Flipping a section without altering its local axes in Advance Design

In this article, we will show you how to flip or rotate a section while keeping its local axes unchanged.

Why Would I Need That?

Flipping a section is often required when modelling.

For example, on the truss beam below, the Channel section defined on top member will not be left with its default orientation:

Channel section with its default orientation

It will most certainly be flipped, using the ‘Angle’ property:

This will not only rotate the section but also its local axes:

Flipping a section also alters its local axes

The Challenge

This modification of member local axes can be a problem when working in a plane workspace, where several degrees of freedom are automatically disabled due to 2D simplifications:

In a 2D workplane, the Ty, Rx and Rz degrees of freedom (out-of-plane direction) are disabled

Now, how can we define an in-plane rotational release when the corresponding degree-of-freedom (R_z) is not available?

In-plane rotation (Rz) can no longer be controlled due to 2D simplifications

The Solution

Fortunately, there is no need to switch to a 3D workplane.

All you need is to flip the section without altering its local axes.

This can be achieved by adding the ‘S’ character at the end of section name.

This will rotate the section while keeping the in-plane bending about the y-y direction:

Section is flipped but the in-plane rotation remains about y-y

And because the R_y degree-of-freedom is still available, one can simply release it:

The Ry degree-of-freedom is available and can be released

Conclusion

This article showed you how to orientate a member and define the required releases without necessarily switching to a complex 3D workplane.

This simple trick in section naming will let you benefit from all the advantages of a 2D analysis (short calculation time, easy result post-processing) while still getting the expected structural behaviour.