Reinforced concrete bridges are iconic parts of modern infrastructure. They are designed for a minimum service life of 100 years. However, environmental factors and/or inappropriate use might cause overload and accelerate the deterioration of bridges. In extreme cases, bridges could collapse when necessary maintenance lacks. Thus, the permanent monitoring for structure health assessment has been proposed, which is the aim of structural health monitoring (SHM). Studies in laboratories have shown that ultrasonic (US) coda wave interferometry (CWI) using diffuse waves has high sensitivity and reliability to detect subtle changes in concrete structures. The creation of micro-cracks might be recognized at an early stage. Moreover, large-volume structures can be monitored with a relatively small number of US transducers. However, it is still a challenge to implement the CWI method in real SHM practical applications in an outdoor environment because of the complex external factors, such as various noise sources that interfere with the recorded signals. In this paper, monitoring data from a 36-m long bridge girder in Gliwice, Poland, instrumented with embedded US transducers, thermistors, and vibrating wire strain gauges, is presented. Noise estimation and reduction methods are discussed, and the influence of traffic, as well as temperature variation, are studied. As a result, the relative velocity variation of US waves following the temperature change with a very high precision of $$10^{-4} \%$$ 10 - 4 % is shown, and a good bridge health condition is inferred. The influence of lightweight real traffic is negligible. The study verified the feasibility of the implementation of the CWI method on real bridge structures.

中文翻译：

---

在真实桥梁上使用尾波干涉测量改善超声波监测的降噪

钢筋混凝土桥梁是现代基础设施的标志性部分。它们的设计使用寿命至少为 100 年。然而，环境因素和/或不适当的使用可能会导致过载并加速桥梁的退化。在极端情况下，当缺乏必要的维护时，桥梁可能会倒塌。因此，提出了结构健康评估的永久监测，这是结构健康监测（SHM）的目标。实验室研究表明，使用漫射波的超声波（美国）尾波干涉测量法（CWI）在检测混凝土结构的细微变化方面具有很高的灵敏度和可靠性。微裂纹的产生可能会在早期被识别。此外，可以使用相对较少的 US 换能器监测大体积结构。然而，由于复杂的外部因素，例如干扰记录信号的各种噪声源，在室外环境中的实际SHM实际应用中实施CWI方法仍然是一个挑战。在本文中，介绍了来自波兰格利维采的 36 米长桥梁的监测数据，该桥梁配备了嵌入式美国传感器、热敏电阻和振弦应变计。讨论了噪声估计和降低方法，并研究了交通和温度变化的影响。结果，美国波随温度变化的相对速度变化以 $$10^{-4} \%$$ 1​​0 - 4 % 的非常高的精度显示，并推断出良好的桥梁健康状况。轻量级真实流量的影响可以忽略不计。