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.

翻译：桥梁冲刷是一个结合水文、岩土与结构过程的复杂现象。作为桥梁垮塌的首要诱因，桥梁冲刷可能引发包括人员伤亡在内的灾难性后果。冲刷深度估算是工程师评估桥梁系统性能的重要任务。设计阶段对冲刷深度的高估可能导致建设成本过度增加，而低估则可能引发桥梁垮塌。多年来，为评估桥墩冲刷深度已发展出众多经验公式，但这些公式仅通过实验室数据或极少量现场数据进行校准。本研究选取包括英国CIRIA C742方法在内的八种公式，利用美国地质调查局（USGS）公开的桥墩冲刷数据库（涵盖现场与实验室条件）对其精度进行比较。通过单参数敏感性评估与全局敏感性分析，识别了八种冲刷公式中最关键的参数。研究表明，采用全局分析方法（即所有参数同时变化）比传统的单参数分析方法能提供更深入的见解。主要结论表明：CIRIA公式与Froehlich公式在现场条件下精度最高；水流攻角、墩体形状及来流水深是影响最显著的参数。降低这三个参数的不确定性将最大程度提升冲刷估算精度。