Non-Linear Finite Element Analysis of Prestressed Concrete Members Under Torsion

This paper is devoted to investigate the behavior of prestressed concrete beams under pure torsion using a non-linear three-dimensional finite element model. The 20-noded isoparametric brick elements have been used to model the concrete. The reinforcing bars are idealized as axial members embedded within the concrete element and perfect bond between the concrete and the reinforcement has been assumed to occur. The behavior of concrete in compression is simulated by an elasto-plastic work hardening model followed by a perfect plastic response, which is terminated at the onset of crushing. On the other hand the behavior in tension is simulated by implementing a smeared crack model in connection with using a tension-stiffening model that account for the retained post-cracking stresses, and a shear retention model that modifies the shear modulus of rigidity as the crack widens. Also a model to simulate the reduction in the concrete compressive strength in presence of tensile transverse straining has been implemented in this study. Two types of prestressed concrete beams under torsion have been analyzed and the finite element solutions were compared with the experimental data. Several parametric studies have been carried out to investigate the effect some important material parameters. In general, good agreement between the finite element solutions and the experimental results was obtained