Large-scale experimental study of precast segmental unbonded posttensioned concrete bridge columns for seismic regions

The seismic behavior of the proposed precast segmental unbonded posttensioned concrete bridge columns for use in regions of high seismicity was investigated experimentally. Posttensioning tendons were placed in the hollow core of the columns and left unbonded with the surrounding concrete to decrease prestress loss during earthquakes. Bonded mild steel bars continuous across the segment joints, also referred to as energy dissipation (ED) bars, were used to enhance the seismic resistance of the columns. The bars were unbonded at the critical joint to avoid premature low cycle fatigue failure. The objectives of this study were to (1) verify the proposed construction method and seismic detailing for the ED bars and (2) investigate the seismic behavior of the columns with different ED bar ratios and posttensioning forces. Four large-scale specimens were designed and tested with lateral cyclic loading. Test results showed that the proposed construction method and seismic detailing for the ED bars were effective in ensuring the ductility and ED capability of the bars. The specimens exhibited excellent drift capacities that are adequate for use in regions of high seismicity. The hysteretic ED capacity and residual drift of the column increased as the ED bar contribution to the expected column strength λED increased. To maintain self-centering capability, λED of more than 35% is not recommended.