Seismic performance of an innovative two-level performance system: Self-centering reinforced concrete bridge pier with external inclined slack tendons

Self-centering reinforced concrete (SCRC) bridge piers are a type of bridge piers that return to their original position after lateral displacements during earthquakes, thereby enhancing post-earthquake functionality by minimizing residual displacements. However, their application has often been limited to regions with low seismic activity due to concerns about their reliability under severe earthquakes. This study introduces an innovative two-level seismic performance SCRC bridge pier (TP-SCRC) to address this concern and compares the seismic performance of the novel system with that of a conventional SCRC pier. A 1/3 scale SCRC bridge pier was initially modeled using OpenSees software and validated using available experimental data. Furthermore, a fullscale SCRC bridge pier with internal unbonded tendons and external dampers was designed using a displacement-based design method. To achieve two-level seismic behavior, external inclined slack tendons were added to both sides of the pier. Slack in the tendons is modeled with gaps at the ends, which prevent the tendons from engaging during low seismic events. Both SCRC and TP-SCRC full-scale bridge piers were modeled using OpenSees and subjected to quasi-static and seismic excitations. The seismic performance of both piers was evaluated using Incremental Dynamic Analysis (IDA) and fragility analysis, focusing on maximum and residual drift ratios. The results indicate that the proposed (TP-SCRC) pier exhibits superior seismic performance during severe earthquakes and significantly reduces the risk of bridge collapse.