Stress in Unbonded Tendons for Post-tensioned Concrete Members—Assessment of Prediction Equations and Experimental Investigation

Abstract

Post-tensioning is being widely used in bridges, namely, highway bridges, railway bridges, segmental box girder bridges, METRO bridges, and sea links. Generally, the ultimate flexural behavior of concrete members with unbonded tendons is evaluated by the stress in unbonded tendons at ultimate state. Researchers have developed the equations using various analytical concepts, namely, moment–curvature relationship, empirical methods, strain reduction coefficient method, equivalent plastic hinge length method, and finite element method. The paper intends to present the performance of the prediction equations and suitable analytical concept for calculating the stress in tendons. Performance of prediction equations for calculating the stress at ultimate in unbonded tendons \( f_{{\text{ps}}} \) has been evaluated using experimental data published in the literature. In the next stage, an experimental investigation on the flexural behavior of post-tensioned concrete beam is done by authors, and the results have been used for evaluation. Also, the FEM analysis using ANSYS package is also performed and compared with test results. It is concluded that the prediction equations developed using equivalent plastic hinge length concept have performed well.