Fig. 3

Internal forces and stress distributions under mixed torsion, shear and flexure. a Distributions of internal forces and b stress distributions induced by internal forces. ^a\( C = [{\text{ch}}(\alpha L/2) - 1]/[\alpha \cdot {\text{sh}}(\alpha L/2)], \) where \( \alpha = \sqrt {\frac{\text{circulatory\; torsional\; stiffness}}{\text{warping\; torsional\; stiffness}}}\).