For a number of cross-sections we cannot find stress functions. However, we can resort to an analogy introduced by Prandtl(1903) Consider a membrane under pressure p, Membrane\. structure whose thickness is small compared to surface
We have looked at basic in-plane loading. Lets now consider a second\building block of types of loading: basic torsion There are 3 basic types of behavior depending on the type of cross-section
