Time-dependent seismic safety assessment of aging steel bridge piers in varied atmospheric conditions

Abstract

Steel bridge piers are typically considered to have good seismic performance and ductility. However, long-term exposure to atmospheric environment can lead to corrosion of the steel bridge piers, which may lead to different performance and failure modes throughout life-cycle stages. This study aims to explore the time-varying seismic performance evolution of steel bridge piers in different atmospheric environments and propose a time-varying seismic evaluation method based on performance requirements. First, a numerical simulation method for aging steel bridge piers is developed by considering the time-varying model of corrosion characteristic parameters. The degradation patterns and failure modes of steel bridge piers with varying parameters throughout their entire life-cycle in industrial and marine atmospheric environments are then analyzed. The concept of time-varying degradation ratio and aging damage index is used to quantify the effects of time-varying factors on seismic performance. Finally, formulas for predicting critical displacement values based on performance requirements are established, and a time-varying seismic performance evaluation method and process are presented. The results show that the seismic performance degradation of aging steel bridge piers caused by different service environments can reach up to 23.7 %. In addition, in the early stages of service, seismic performance of aging steel piers may be significantly reduced, with the displacement ratio for safety performance points decreasing by up to 28.6 %. Corrosion leads to more pronounced plastic deformation and stress concentration in the failure mode of aging steel piers. The aging damage index is affected by the coupling of corrosion parameters and geometric parameters. As service time progresses, the value and variability of aging damage index of steel piers increase. The accuracy of the formula for predicting time-varying critical displacement values, considering performance requirements, is validated through supplementary models and previous test results. The results underscore the importance of considering aging effect and environmental factors in the seismic performance evaluation. The proposed time-varying seismic performance evaluation method can provide reference for the life-cycle seismic design and verification of aging steel bridges.