Cyclic Response of Unbonded Posttensioned Precast Columns with Ductile Fiber-Reinforced Concrete

A precast segmental concrete bridge pier system is being investigated for use in seismic regions. The proposed system uses unbonded posttensioning (UBPT) to join the precast segments and has the option of using a ductile fiber-reinforced cement-based composite (DRFCC) in the precast segments at potential plastic hinging regions. The UBPT is expected to cause minimal residual displacements and a low amount of hysteretic energy dissipation. The DFRCC material is expected to add hysteretic energy dissipation and damage tolerance to the system. Small-scale experiments on cantilever columns using the proposed system were conducted. The two main variables were the material used in the plastic hinging region segment and the depth at which that segment was embedded in the column foundation. It was found that using DFRCC allowed the system to dissipate more hysteretic energy than traditional concrete up to drift levels of 3-6%. Furthermore, DFRCC maintained its integrity better than reinforced concrete under high cyclic tensile-compressive loads. The embedment depth of the bottom segment affected the extent of microcracking and hysteretic energy dissipation in the DFRCC. This research suggests that the proposed system may be promising for damage-tolerant structures in seismic regions.