Analysis of scour vulnerability for bridge lifetime based on hydrological uncertainty

Abstract

[Objective] The formation of scour holes is a primary cause of bridge failure under flood conditions. Uncertainty in hydrological data and multi-layer soil erosion significantly impact the accuracy of scour depth predictions. Evaluating the safety performance of bridges over their entire lifecycle under flood-induced scour is essential. [Methods] Using a real bridge project as a case study, the Seasonal Autoregressive Integrated Moving Average(SARIMA) model was applied to conduct a statistical analysis of scour depth over the bridge's lifecycle, based on incomplete hydrological data. Following AASHTO guidelines, four failure modes of bridge pile foundations under flood conditions were considered, and a time-dependent safety performance evaluation model based on probabilistic scour depth was developed. The time-dependent vulnerability curves for the bridge's lifecycle were also obtained. [Results] The result demonstrated that the proposed method effectively predicts the relationship between bridge foundation scour depth and service time, with scour depth initially increasing rapidly before gradually slowing down, particularly over the first 25 years. [Conclusion] The predicted pile foundation scour depth increases with extended service time, and its failure probability is negatively correlated with embedment depth, but is influenced by soil layer parameters. This method provides a theoretical basis for assessing and designing bridge scour over its lifecycle, improving bridge safety under flood conditions.

Keywords

bridge foundation / risk assessment / hydrological information / scour depth / vulnerability / influencing factor