Probabilistic Understanding of Seismic Performance of River-Crossing Bridges with Scour Effects: A Critical Review and Investigation of Seismic-Scour Damage Effects

This paper first presents a critical review of the existing literature related to the seismic performance of river-crossing bridges considering scour effects. Two probabilistic models are proposed to answer the central research question-how to determine if a river-crossing bridge is seismic-scour critical. The two models, the mean-scour fragility analysis (MS-FA) and the total-scour demand hazard analysis (TS-DHA), produce operational analytics that enables comprehensive evaluation of seismic-scour effects. An integrated damage index is defined based on local and system-level ductility demands to accommodate a soil-foundation-structure bridge system with variable scour depths. The comprehensive numerical study illustrates that foundation scour tends to be beneficial by decreasing the probability of exceedance for minor or possibly moderate damage. Given the bridge model studied in this work, results obtained from the fragility analysis show a 2.5% decrease in the probability of exceedance of the moderate damage at the maximum considered earthquake level as scour depth (SD) increases from the levels of 10 m < SD <= 15 m to SD > 15 m. Also, the demand-hazard analysis illustrates the two-sided effects of foundation scour, which indicates that scour has a positive impact when the proposed damage index is smaller than 2.5 while having a detrimental effect as the damage index increases. This paper concludes with a verification of the proposed framework and remarks on choosing the proposed models in practice.