Impact Behavior of Unbonded Post-Tensioned Concrete Beams

This study experimentally investigates the effects of the unbonded post-tensioning on the response of reinforced concrete (RC) beams under impact loads. A total of fifteen specimens were cast and tested. All specimens had identical longitudinal reinforcement, but varying shear rein forrement ratios designed to be both flexural-and shear-deficient in static conditions according to the ACI code. In particular; thirteen unbonded post-tensioned (PT) beams were tested under drop weight impact applied at the midspan in simply supported conditions and compared with conventional type RC beams. The main variables investigated include increasing levels of PT force and the application of two different impact energies per each specimen type, shear- or flexural-deficient. The experimental results showed that the levels of PT force and shear reinforcements of the specimens played an important role in their overall behavior: With respect to beneficial design recommendations, relationships between the impact resistance and the static capacity are provided; a general increase in strength of around three times that of the static capacity is observed when impacted. Additionally, relationships between the ratio of the impact energy to static capacity are developed with regard to the maximum and residual member displacements.