Basic structural elements of stringer-stiffened thin-walled structures, forces, moments, stresses and deformation of tapered/segmented bars/beams, flexure stress and deflection of beams, principal plane, plane of bending and plane of loading for beams with asymmetric cross sections, stresses and twist due to torsion, shear flow and shear center in open and closed stiffened thin-walled structures, stiffened multicell beams, materials properties and selection.