Feasibility study of prestress force prediction for concrete beams using second-order deflections

The safety and sustainability of prestressed concrete bridges can be improved with accurate prestress loss prediction. Considerable loss of the prestress force may imply damages hidden in the bridge. In this study, a prestress force identification method was implemented for concrete beams. Based on the Euler–Bernoulli beam theory, the procedure estimates the prestress force by using one or a set of static displacements measured along the member axis. The implementation of this procedure requires information regarding the flexural rigidity of the beam. The deflected shape of a post–tensioned concrete beam, subjected to an additional vertical load, was measured in a short term in several laboratory experiments. The accuracy of the deflection measurements provided favorable prestress force estimates. In particular, the “compression–softening” theory was validated for uncracked post–tensioned concrete beams.