Comparative study on seismic behavior of steel tube reinforced concrete piers and reinforced concrete piers

The Steel Tube Reinforced Concrete (STRC) bridge pier is an advanced steel-concrete composite system, featured by the integration of a centrally placed core steel tube into conventional reinforced concrete (RC) piers. This study experimentally evaluates the fundamental seismic behavior of STRC piers through cyclic-loading test on six pier specimens, comprising three STRC and three RC counterparts, designed with shear span ratios spanning 1.5 to 3.0. Damage progression and failure modes were meticulously documented, followed by a systematic comparative analysis of key seismic performance indicators between the two structural typologies. Experimental results reveal that STRC piers exhibit stable hysteretic responses with gradual strength attenuation and stiffness degradation. While the embedded steel tube has negligible influence on initial lateral stiffness, it significantly enhances lateral load capacity, deformability, energy dissipation, and self-centering capability compare to RC piers. Crucially, the core steel tube suppresses brittle shear failure mechanisms in low shear span ratio specimen, facilitating a transition to a relatively ductile failure mode. These findings validate that STRC piers integrate high load-carrying capacity with controlled damage progression under severe seismic loading, providing a viable solution for enhancing the resilience and post-earthquake serviceability of transportation infrastructure in seismically active regions.