Evaluating the Seismic Performance of Circular Concrete-Encased Steel Bridge Columns for High Seismicity Regions

This research evaluates the seismic resilience of lifeline bridge columns in Vancouver, British Columbia, by comparing traditional reinforced concrete (RC) columns with an equivalent circular concrete-encased steel (CES) system. Designed to meet the stringent performance-based requirements of CSA S6-25 and the BC Ministry of Transportation and Infrastructure (MoTI) Supplement, the structures were analyzed under a suite of ground motions representing the complex crustal, subcrustal, and subduction hazards of the Pacific Northwest. Nonlinear fiber-discretization modeling, validated against experimental data, was employed to assess damage progression and serviceability limits through comprehensive pushover, moment-rotation, and nonlinear time-history analyses. The results demonstrate that while both systems satisfy lifeline criteria, the CES configuration provides a superior safety margin due to the presence of the encased structural steel core. This internal steel member maintains vertical load capacity and extends the stable displacement plateau beyond the capacity of conventional RC, effectively reducing reinforcement strain and facilitating immediate post-seismic recovery. These findings highlight circular CES piers as a highly resilient alternative for critical transportation infrastructure in high-seismicity regions.