Abstract
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} % 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.
Highlights
For many decades, concrete has been widely used for civil infrastructure construction because it is strong, durable, and resistive
This paper describes how the coda wave interferometry (CWI) method is applied at a bridge, which is equipped with a new type of embedded US transducer
This study has shown the possibility of applying the CWI method at a real bridge under a noisy outdoor environment
Summary
Concrete has been widely used for civil infrastructure construction (i.e., bridges, highways, foundations, etc.) because it is strong, durable, and resistive. The bridge construction market is growing rapidly to meet the demand of economic development. Due to the increasing freight traffic, environmental factors and/or irregular use, the service life time of bridges can be reduced significantly. The timely necessary maintenance of bridges to guarantee their service life is receiving more attention. A wide variety of sensors have been developed for bridge health monitoring. Accelerometers, which measure the vibration acceleration data, are another type of common sensor used for bridge SHM applications [19,20,22]. Along with the development of technologies, smartphones can be involved in SHM. Some sensors integrated inside the smartphone may contribute valuable information for SHM [11,30].
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