Plastic-collapse analysis of torsion

Ryszard Dabrowski points out inconsistencies in the plastic-collapse analysis of torsion, based on sand-heap analogy, presented by Yong-Lin Pi and N.S. Trahair. In his analysis, Dabrowski identifies three distinct components of total ultimate torque. He then shows how these components produce a total ultimate torque that is slightly higher than the one given by Pi and Trahair. For their part, Pi and Trahair assert that, among other faults, the equation used by Dabrowski merely approximates total ultimate torque and lacks an essential correction factor.