Refined softened-truss model with efficient solution procedure for reinforced concrete members under torsion combined with bending

This article presents a refined version of the Combined Action Softened Truss Model (CA-STM) with efficient solution procedure to analyze reinforced concrete (RC) members under torsion combined with bending. To refine the model, a set of appropriate smeared stress-strain relationships for concrete and steel bars, to account for the softening and stiffening effects, are implemented. For solid sections, an alternative criterion to fix the maximum thickness for the panels constituting the walls of the equivalent hollow section is also considered. In addition, a simpler criterion is used to compute the equivalent longitudinal reinforcement for each panel. Instead of using the original algorithm to solve the CA-STM, which is based on a classical trial and error solution technique, an alternative one which lead to a more efficient solution procedure with higher numerical stability is implemented. These refinements allow the model to predict efficiently the response of RC members under torsion combined with bending. The results obtained from the refined efficient CA-STM procedure are compared with several experimental results found in the literature, where good agreement is observed.