Abstract
In bridge maintenance, particularly with regard to fatigue damage in steel bridges, it is important to determine the displacement response of the entire bridge under a live load as well as that of each member. Knowing the displacement response enables the identification of dynamic deformations that can cause stresses and ultimately lead to damage and thus also allows the undertaking of appropriate countermeasures. In theory, the displacement response can be calculated from the double integration of the measured acceleration. However, data measured by an accelerometer include measurement errors caused by the limitations of the analog-to-digital conversion process and sensor noise. These errors distort the double integration results. Furthermore, as bridges in service are constantly vibrating because of passing vehicles, estimating the boundary conditions for the numerical integration is difficult. To address these problems, this paper proposes a method for determining the displacement of a bridge in service from its acceleration based on its free vibration. To verify the effectiveness of the proposed method, field measurements were conducted using nine different accelerometers. Based on the results of these measurements, the proposed method was found to be highly accurate in comparison with the reference displacement obtained using a contact displacement gauge.
Highlights
Fatigue damage in steel bridges is difficult to detect
To detect fatigue damage and take action before brittle fracture occurs, it is important to determine the displacement response of the entire bridge to external forces, in addition to that of each member, and to specify the displacement responses of members that can lead to stress concentrations [1,2]
To verify the effectiveness of the proposed method, measurements were performed on an actual bridge using the abovementioned nine different accelerometers
Summary
Fatigue damage in steel bridges is difficult to detect. because there is a possibility that fatigue damage will lead to brittle fracture, appropriate inspection and countermeasures are necessary. One method of directly measuring the displacement is to use fixed reference-based technologies, such as linear variable differential transformers (LVDTs), laser Doppler vibrometers (LDVs) [3], and vision-based systems [4,5,6]. These measurements are accurate, they are often impractical because they are costly and difficult to install and, more importantly, they require a fixed reference point, which is often unattainable in full-scale civil structures [7]
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