Normally, steel beams are of open section (except box section), and their torsional section modulus is about one order of magnitude smaller than the flexural section modulus, i.e., their torsional capacity is about 1/10 of the bending capacity, which makes it uneconomical to utilise steel beams to withstand torsional moments.Thus, it is usually constructed to ensure that it is not subjected to torsion, so there is no torsion calculation of steel beams in the steel structure design code.