Torsion in multi-cell thin-walled girders

A technique for finding the stiffnesses and shear flows in multi-cell thin-walled girders subjected to linear elastic torsion is proposed. The girder is thought as the superposition of elementary closed tracks, just like open girders are the juxtaposition of thin strips. For each track there is a uniform value of the stress flow function, found by means of a linear system of compatibility equations resembling those for the redundant reactions in statically indeterminate frames. The connection between the proposed approach and fundamental properties of graphs is discussed; the advantages with respect to the standard procedures are also enlightened referring to two sample cross-sections.