Seismic Performance and Reinforcement Ratio Analysis of Thin-Walled Piers of Continuous Girder Bridges in High -Seismic-Intensity Regions

Existing studies on bridge seismic behavior mainly address small- and medium-span bridges with circular column piers, with limited applicability to long-span, thin-walled high piers in mountainous regions. This study investigated the seismic performance and rational reinforcement ratio of thin-walled piers in high-seismic-intensity regions. A beam-element finite element model of a three-span prestressed concrete continuous girder bridge was established. Three pier heights (20 m, 50 m, and 80 m) were considered, and response spectrum analyses were conducted under peak ground accelerations of 0.1 g to 0.3 g. Results indicated that tall piers exhibit pronounced flexibility. The fundamental period increases from 1.02 s to 3.38 s with increasing pier height. For an 80 m pier, the first ten vibration modes are predominantly local bending or torsion, each with mass participation below 1%, requiring many modes for computational accuracy. Under seismic loading, the design of short piers is governed by internal forces, while that of tall piers is controlled by pier-top displacements. The reinforcement ratio of short piers is dictated by seismic demands, and shear requirements are difficult to satisfy solely by increasing transverse reinforcement. For tall piers, the longitudinal reinforcement ratio may follow minimum detailing, while the transverse reinforcement ratio increases significantly with higher seismic intensity. These findings provide a reference for seismic design and reinforcement optimization of long-span, thin-walled pier bridges in high seismic intensity regions.