ASSESSING SEISMIC VULNERABILITY OF PRECAST POST-TENSIONED SEGMENTAL PIERS

Abstract

Precast post-tensioned segmental (PPS) bridge piers mitigate global and local damages of bridge structures through natural hinges. The application of PPS piers has increased recently in Accelerated Bridge Construction (ABC). Therefore, to increase their use in high-seismicity regions, this paper examines seismic vulnerability assessment of post-tensioned segmental bridge piers with Shape Memory Alloy (SMA) bars through a Finite Element (FE) framework. First, to investigate the energy dissipation capacity of the PPS piers with SMA, an extensive parametric study performed on the key design parameters including, (i) number of segments or aspect ratio, (ii) length, area, and post-tensioning of the SMA bars, and (ii) area and post-tensioning of the tendon. The results are also compared with the piers without SMA bars. Furthermore, an equivalent reinforced concrete (RC) pier to one of the PPS piers is also analysed. Incremental dynamic analysis (IDA) is performed, and fragility curves are generated to evaluate seismic performance of the PPS piers with and without SMA bars using a suite of 44 far-fault ground motions. The IDA results show that, slenderizing the PPS piers tends to change failure criterion from the yielding of the post-tensioning tendon to strength loss of the pier. For squat piers, the yielding of the tendon governs the failure of the pier while for very slender PPS piers, the strength of PPS piers drops due to second-order effects at small drift values prior to the yielding of the post-tensioning tendon. Furthermore, the equivalent RC pier reaches slight and medium damage states in lower intensity measures compared to the PPS piers. Finally, IDA results of PPS piers with SMA bars show that their median IDA curves for drift responses are lower than the ones without SMA bars.