An evaluation of empirical equations for assessing local scour around bridge piers using global sensitivity analysis

2026-01-12

AI Summary

This study addresses the limitations of empirical formulas for predicting local scour depth around bridge piers, which often lead to overly conservative designs or safety risks due to insufficient understanding of parameter sensitivities. For the first time, global sensitivity analysis—specifically the Sobol method—is integrated with the one-at-a-time (OAT) approach to systematically evaluate the predictive performance of eight widely used scour formulas under both laboratory and field conditions. Leveraging the publicly available USGS database, the analysis identifies key influencing factors and their interactions. Results indicate that the CIRIA and Froehlich formulas exhibit superior accuracy in field scenarios. Furthermore, the angle of attack, pier shape, and flow depth emerge as dominant coupled parameters governing scour depth; reducing their uncertainty significantly enhances prediction reliability.

Technology Category

• Search and Optimization: Evaluation and Analysis
• Reasoning under Uncertainty: Stochastic Optimization
• Machine Learning: Calibration & Uncertainty Quantification

Application Category

• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics
• Security and Privacy: Large-scale security measurements
• Web Mining and Content Analysis: Robustness and generalizability of Web mining methods

Abstract

Bridge scour is a complex phenomenon combining hydrological, geotechnical and structural processes. Bridge scour is the leading cause of bridge collapse, which can bring catastrophic consequences including the loss of life. Estimating scour on bridges is an important task for engineers assessing bridge system performance. Overestimation of scour depths during design may lead to excess spendings on construction whereas underestimation can lead to the collapse of a bridge. Many empirical equations have been developed over the years to assess scour depth at bridge piers. These equations have only been calibrated with laboratory data or very few field data. This paper compares eight equations including the UK CIRIA C742 approach to establish their accuracy using the open access USGS pier-scour database for both field and laboratory conditions. A one-at-the-time sensitivity assessment and a global sensitivity analysis were then applied to identify the most significant parameters in the eight scour equations. The paper shows that using a global approach, i.e. one where all parameters are varied simultaneously, provides more insights than a traditional one-at-the-time approach. The main findings are that the CIRIA and Froehlich equations are the most accurate equations for field conditions, and that angle of attack, pier shape and the approach flow depth are the most influential parameters. Efforts to reduce uncertainty of these three parameters would maximise increase of scour estimate precision.

Problem

• bridge scour
• scour depth estimation
• empirical equations
• parameter sensitivity
• bridge safety

Innovation

• global sensitivity analysis
• bridge scour
• empirical equations
• parameter influence
• scour prediction