A unified softened truss model for RC and PC beams under torsion

A recent analytical model based on refinement of the Variable Angle Truss Model (VATM) and called Generalized Softened Variable Angle Truss-Model (GSVATM) was proposed in previous articles to predict the full response of reinforced concrete (RC) and prestressed concrete (PC) beams (solid and hollow) under torsion. The GSVATM is reformulated here in a unified form and used to illustrate some calculation examples related to RC and PC beams under torsion. It is shown that the unified GSVATM can provide reliable information about the effective torsional response of the analyzed beams; namely the torque, twist, torsional stiffness, and stress or strain in the materials for all loading stages, as well as information on the failure type of the beam. The model is not difficult to implement in a computer and can be used as a reliable analytical tool to help engineers optimize some aspects of the torsional design of structural concrete beams.