The shear areas are usually a form factor times the axial area. These form factors are dependent on the shapes and are published in text books like Timoshenko & Gere; Roark; etc. For thin walled pipes pi x r x t may be used, I think, where r=(OD+ID)/2 and t is the thickness.

The shear areas are usually a form factor times the axial area. These form factors are dependent on the shapes and are published in text books like Timoshenko & Gere; Roark; etc. For thin walled pipes pi x r x t may be used, I think, where r=(OD+ID)/2 and t is the thickness.