Curved girder bridges with variable pier heights and small curvature radii are widely adopted in modern transportation infrastructure due to their adaptability to complex terrain and urban landscapes. However, this irregular spatial configuration significantly increases their mechanical complexity under seismic loading. Post-earthquake investigations, such as those following the devastating earthquakes in regions like Japan and California, have demonstrated that these geometric characteristics substantially elevate structural vulnerability. The curvature-induced centrifugal forces, combined with the differential displacements caused by varying pier heights, often lead to concentrated damage at critical components, including pier bases and bearings. As such, the optimization of bearing configurations emerges as a crucial strategy for mitigating seismic responses in these geometrically complex bridges, aiming to enhance structural integrity and safety during seismic events.

This investigation centers on a prototype 4×20 m concrete curved bridge with a 50m radius. To accurately assess its seismic performance, the bridge was scaled down to 1/20 through meticulous dimensional analysis for shaking-table testing. The scaled model was subjected to a series of dynamic loading scenarios, simulating real-world seismic conditions. Concurrently, a refined finite element model was developed using advanced engineering software. This model was rigorously validated against the experimental results, ensuring its reliability for further analysis. This validation process allowed for a comprehensive comparative analysis of seismic performance across different pier-girder connection systems. Three distinct intermediate pier configurations were then systematically examined through nonlinear time-history analysis under bidirectional seismic excitation, enabling a detailed exploration of their dynamic responses and failure mechanisms.

For four-span curved bridges with height-varying piers, the intermediate pier bearing configuration exerts a pivotal influence on global seismic performance, especially when transition piers utilize unidirectional sliding bearings. Numerical simulations, supported by detailed data analysis, reveal that the proposed hybrid system, which combines sliding bearings at tall/medium piers with fixed bearings at short piers, demonstrates superior mechanical behavior compared to conventional fully-fixed configurations. Specifically, the hybrid system reduces pier-bottom moment peaks by up to 35% and shear force peaks by 30% through optimized force redistribution. Despite these significant reductions in internal forces, it maintains comparable displacement control capacity. Notably, the hybrid configuration effectively mitigates moment concentration at critical pier bases and constrains structural displacements within operational thresholds, significantly enhancing the bridge’s capability to prevent girder unseating during extreme seismic events.

Mechanistic analysis reveals that the hybrid system fundamentally alters internal force distribution patterns, concentrating moments at strategically reinforced short piers while redistributing seismic energy through controlled sliding. Compared to fully-fixed systems, the hybrid configuration achieves a 30%~35% reduction of internal force concentration at critical pier locations while maintaining effective displacement control. This study establishes that the rational allocation of fixed bearings to shorter piers combined with sliding mechanisms at taller piers creates an optimal stiffness distribution for seismic energy dissipation. The validated numerical framework and proposed design methodology provide both theoretical foundations and practical guidelines for performance-based seismic design of spatially complex bridge systems. These findings offer essential insights for enhancing structural safety and reliability in earthquake-prone regions, potentially leading to the development of more resilient bridge designs in the future.