Generalized softened variable angle truss-model for reinforced concrete beams under torsion

A new analytical model based on a refinement of the variable angle truss-model (VATM) is developed to predict the entire torque-twist curve of reinforced concrete beams under torsion, including ultimate and cracking states. The refinement is based on the incorporation of the tensile stress-strain relationship of the concrete into the VATM. The new analytical model is called generalized softened variable angle truss-model (GSVATM). The new formulation and the calculation procedure for GSVATM are presented and the theoretical predictions are compared with the results from reported tests. It is shown that the new analytical model described in this paper gives good predictions when compared with the experimental data reported in the literature.