Seismic performance of precast railway bridge columns with hybrid bonded post-tensioning and grouted sleeve connections

Precast railway bridge columns require high lateral stiffness under service loads while maintaining satisfactory ductility and resilience during earthquakes. Conventional grouted sleeve (GS) connections may reduce the initial lateral stiffness due to deformation concentration at the column–foundation interface. To address this issue, this study proposes a novel hybrid connection combining bonded post-tensioning tendons with GSs. Two half-scale specimens with rectangular and circular cross-sections were designed and tested under quasi-static cyclic loading. A fibre-based finite element model was developed and validated against the experimental results, followed by a parametric study on the effects of initial prestress and tendon spacing. The proposed connection prevented visible cracking under the design service load, and effectively compensated for the stiffness reduction associated with GS connections. Both specimens exhibited flag-shaped hysteretic responses with notable self-centring capability and displacement ductility. Damage was concentrated at the ends of the GS zone, while no tendon fracture was observed. The numerical results showed that increasing the initial prestress and tendon spacing would increase residual displacement by promoting earlier tendon yielding.