Lifetime Reliability Assessment of Bridges with Scour Accumulation of Cohesive Soils

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Abstract
Because of undesired hydraulic effects, bridge collapse accidents have become increasingly frequent during the flooding season considering that hydraulic effects on bridge design are paramount to controlling and mitigating hydrological damage. Previous studies have made important progress in assessing bridge performance under flood-induced scour, including time-dependent scour reliability, probabilistic scour vulnerability, and the life-cycle performance of bridges under multiple hazards. However, limited attention has been paid to the design-oriented lifetime reliability assessment of bridges subjected to accumulated foundation scour resulting from successive flood events. To bridge this gap, this study conducted a lifetime reliability analysis against floods, incorporating structural, hydraulic, and geological characteristics. First, a probabilistic scour prediction throughout service life was performed to determine the time-varying scour depth. Then, a refined finite-element model of a bridge was constructed considering soil–pile interaction and scour morphology. Next, the capacity of the pile foundation under floods and service loads was calculated to determine the reliability of bridges under given scour depths. Finally, a lifetime reliability evaluation with and without considering scour accumulation under repeated flood events was conducted. The reliability of the bridge, considering scour accumulation and climate change, decreased to 0.89 after 200 years of service, while that without considering scour accumulation and climate change decreased to 0.01. This paper reveals the necessity of considering scour accumulation throughout service life in bridge design. The proposed lifetime reliability assessment framework can effectively and economically enhance bridge safety against floods.

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