Torsional behaviour of prestressed high-strength concrete beams

A model for analysing nonlinear behaviour up to rupture of prestressed and reinforced concrete beams subjected to torsion is proposed. The variables governing the proposed model are the opening, w, and the sliding, v, of crack lips, as well as the strain, epsilon(c2), Of the compressed concrete struts which are generated between cracks. The use of these variables permits to express compatibility and equilibrium conditions in a compact form, and to model in a realistic way phenomena as interlock, tension-stiffening and dowel-action. By means of the proposed approach, the specific aspects of torsion are highlighted, with reference also to complex aspects such as crack width, stress level in the reinforcement, maximum strain in the concrete cover and torque-rotation response. Results obtained through the proposed model have shown a good agreement in comparison to experimental data.