Bridges traversing active faults in aggressive environments (such as coastal or reservoir regions) face the
coupled risks of chloride-induced corrosion and fault-crossing seismic excitations. The failure mechanisms
governing continuous rigid frame bridges (CRFBs) under such coupled degradation-seismic conditions remain
poorly understood. This study develops an integrated analytical framework comprising: (i) time-dependent
deterioration models accounting for chloride-induced reinforcement section loss, yield-strength reduction, and
concrete cover softening; and (ii) a refined 3D nonlinear finite element model (FEM) incorporating fiber beam
column elements, a soil-structure interaction system (SSIS), bearings, and pounding effects. (iii) Synthetic fault
crossing ground motions are generated by superimposing low-frequency fling-step pulses onto spectrum-matched
high-frequency records. These synthetic motions are then applied to the bridge model via multi-support excitation.
Comparative analyses demonstrate that fault-crossing motions shift the structural response from an inertia-dominated
amplification mode to a quasi-static forced displacement mode. This mode shift imposes significantly larger and
more asymmetric kinematic demands compared to standard near-fault scenarios. Structural responses exhibit a
nonlinear dependence on permanent ground rupture displacement (PGRD), typically plateauing at an observed peak
of 0. 6 m for the examined cases. This phenomenon is attributed to a force-limiting mechanism: the yielding of
foundation soil and the premature plastic hinging of corroded piers restrict the inertial force transmission to the
superstructure. Furthermore, the fault-crossing angle (FCA) governs the demand distribution, exhibiting an βM
shapedβ sensitivity; deviation from orthogonality amplifies pier-base curvature by up to three orders of magnitude due
to longitudinal locking effects. A frequency-decoupling mechanism is also identified: low-frequency pulses dictate
global pier drifts and permanent bearing offsets, whereas high-frequency components control local cyclic damage.
Crucially, corrosion accelerates pier yielding and exacerbates the accumulation of plastic damage, thereby
substantially amplifying the collapse probability under the extreme forced displacements induced by fault rupture.
Key Words
continuous rigid frame bridge; corrosion-induced degradation; fault-crossing ground motion; frequency decoupling; soil-structure interaction system
Address
Hongyu Jia β State Key Laboratory of Bridge Intelligent and Green Construction, Southwest Jiaotong University, Chengdu, 611756, Sichuan, China
Jiahao Hou β School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China
Hao Bai β Sichuan Expressway Construction & Development Group Co., Ltd., Chengdu, 610041, China
Zhi Xu β Shudao Investment Group Co., Ltd., Chengdu, 610094, China
Kang Jia β Sichuan Chengdu Construction Engineering Group Co., Ltd., Chengdu 610000, Sichuan, China
Shixiong Zheng β 1)State Key Laboratory of Bridge Intelligent and Green Construction, Southwest Jiaotong University, Chengdu, 611756, Sichuan, China 2)School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China
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