One of the most prevalent causes of bridge failure around the world is “scour”—the gradual erosion of soil around a bridge foundation due to fast-flowing water. A reliable technique for monitoring scour would help bridge engineers take timely countermeasures to safeguard against failure. Although vibration-based techniques for monitoring structural damage have had limited success, primarily due to insufficient sensitivity, these have tended to focus on the detection of local damage. High natural frequency sensitivity has recently been reported for scour damage. Previous experiments to investigate this have been limited as a result of the cost of full-scale testing and the fact that scaled-down soil-structure models tested outside a centrifuge do not adequately simulate full-scale behaviour. This paper describes the development of what is believed to be the first-ever centrifuge-testing programme to establish the sensitivity of bridge natural frequency to scour. A 1/60 scale model of a two-span integral bridge with 15 m spans was tested at varying levels of scour. For the fundamental mode of vibration, these tests found up to a 40% variation in natural frequency for 30% loss of embedment. Models of three other types of foundation, which represent a shallow pad foundation, a deep pile bent and a deep monopile, were also tested in the centrifuge at different scour levels. The shallow foundation model showed lower frequency sensitivity to scour than the deep foundation models. Another important finding is that the frequency sensitivity to “global scour” is slightly higher than the sensitivity to “local scour”, for all foundation types. The level of frequency sensitivity (3.1–44% per scour depth equivalent to 30% of embedment of scour) detected in this experiment demonstrates the potential for using natural frequency as an indicator of both local and global scour of bridges, particularly those with deep foundations.

世界范围内桥梁失效最常见的原因之一是“冲刷”，即快速流动的水流逐渐侵蚀桥基周围的土壤。可靠的冲刷监测技术将帮助桥梁工程师及时采取对策，防止发生故障。尽管主要由于灵敏度不够，基于振动的结构损伤监测技术取得了有限的成功，但这些技术往往侧重于局部损伤的检测。最近有报道称冲刷损伤具有高固有频率敏感性。由于全尺寸测试的成本以及在离心机外测试的按比例缩小的土壤结构模型不能充分模拟全尺寸行为，先前对此进行研究的实验受到限制。本文描述了被认为是有史以来第一个离心机测试程序的开发，以确定桥梁固有频率对冲刷的敏感性。跨度为 15 m 的两跨整体桥的 1/60 比例模型在不同的冲刷水平下进行了测试。对于基本振动模式，这些测试发现，嵌入损失 30% 时，固有频率变化高达 40%。其他三种类型的基础模型，即浅垫基础、深弯桩基础和深单桩，也在不同冲刷水平的离心机中进行了测试。浅基础模型对冲刷的频率敏感性低于深基础模型。另一个重要发现是，对于所有地基类型，对“整体冲刷”的频率敏感性略高于对“局部冲刷”的敏感性。频率灵敏度水平 (3.本实验中检测到的每次冲刷深度 1-44%（相当于冲刷嵌入的 30%）表明了使用固有频率作为桥梁局部和整体冲刷指标的潜力，特别是那些具有深基础的桥梁。