Softened truss model for reinforced NSC and HSC beams under torsion: A comparative study

A computing procedure is presented to predict the ultimate behavior of Normal-Strength Concrete (NSC) and High-Strength Concrete (HSC) beams under torsion. Both plain and hollow beams are considered. In order to model the non-linear behavior of the compressed concrete in the struts and of the tensioned steel reinforcement several proposals for the stress (σ)–strain (ε) relationships were tested. The theoretical predictions of the maximum torque and corresponding twist were compared with results from reported tests and with the predictions obtained from Codes. One of the tested theoretical models was found to give excellent predictions for the maximum torque when compared with those obtained from some codes of practice and with experimental values of NSC and HSC beams (plain and hollow).

► A procedure to evaluate the behavior of RC beams under torsion is presented.
► Both plain and hollow beams are considered.
► Various proposals for stress–strain curves for concrete and steel were tested.
► Theoretical results are compared with test results and codes of practice.
► One combination of the tested models gave excellent predictions.