Shaking table tests of seismic-resilient post-tensioned reinforced concrete bridge piers with enhanced bases

Post-tensioning reinforced concrete (PRC) bridge piers represent a promising solution due to their reduced damage and self-centering behavior after severe seismic events. However, it has been highlighted that their performance and repairability could be compromised by the early crushing of the base compression toe due to rocking. Several studies attempted to address this issue by proposing strategies to enhance the piers' base integrity. The present study experimentally investigates the seismic performance of two enhanced PRC solutions by shaking table tests. One bridge pier was selected as a benchmark and investigated without any enhanced detail, named PRC, and with two enhancement strategies based on armoring the pier's base with a steel tube and ultra-high performance concrete, respectively, named PRC+ST and PRC+UHPC. The seismic performance of the three types of PRC piers was evaluated using three ground motion records scaled at the elastic and design-basis earthquake levels. Successively, the piers were subjected to a sequence of ground motion records with increasing intensity until failure. The results show that the enhanced solutions substantially reduced the base region damage compared with the benchmark PRC; nevertheless, their segments above the enhanced regions experienced some damage, highlighting the importance of considering an adequate length for the enhanced segment. The results are also compared with identical quasi-static tests highlighting the influence of the dynamic response. The effects of the dynamic loading, the impact at the rocking interface, and the velocity pulse on the PRC piers' responses are analyzed and discussed.