Parametric experimental investigation of unbonded post-tensioned reinforced concrete bridge piers under cyclic loading

The present paper investigates the cyclic performance of unbonded post-tensioned reinforced concrete (PRC) rocking piers by a parametric experimental campaign. PRC rocking specimens are assembled by hybrid connections, containing an ungrouted post-tensioned (PT) bar and grouted mild steel bars, that is, energy-dissipation (ED) components. The properties of a benchmark PRC pier were defined according to a design procedure to control its strength, ductility, energy dissipation capacity, and self-centering behavior. Five additional PRC piers with different ED bars amounts, initial PT force, and ED bars unbonded lengths were also tested to investigate the influence of these parameters on the cyclic performance. The test results show the superior cyclic performance of the PRC pier in limiting both damage and residual deformations. The parametric analysis highlighted that decreasing the initial PT force and/or ED bars amount enhances the PRC's ED capacity at the expense of the lateral force resistance and self-centering behavior. Moreover, it has been observed that the influence of ED bars' unbonded length only minimally affects the PRC pier's cyclic performance due to ED bars' bond-slip and concrete cover spalling of the pier shaft. Analytical models describing the PRC piers' lateral force-drift cyclic behavior were formulated and calibrated, showing a good agreement with test results for all specimens. The results and findings provide a valuable reference and solution for tailoring an efficient parameter recommendation of PRC rocking piers.