Thin-walled open sections
Thin-walled open sections may be defined as
The sections in which the thickness of material is small as compared with the overall geometry of the material and there is only one or no axis of symmetry.
These sections are widely used. Their main use is in air craft industry. Common examples are channel section, top hat, zed, angle and circular sections.
Within the section, shear stress variation is almost constant and we can assume shear stress constant.
Reference : Mechanics of Engineering Materials by P.P.Benham