PSI - Issue 64

Ayaho Miyamoto et al. / Procedia Structural Integrity 64 (2024) 464–475 Author name / Structural Integrity Procedia 00 (2019) 000–000

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can be characterized by standard deviations and averages if about 15 data sections are used, indicating that the central limit theorem mentioned earlier holds true. In fact, in the bus-based monitoring system, the standard deviation of “characteristic deflection” may be deemed to converge if the number of data sections is around 14 or 15. It was therefore decided to use 15 data sections in monitoring time-dependent changes in “characteristic deflection”. Based on the concept described above, Fig. 6 shows how “characteristic deflection” (measured value) and the simple moving average change. As shown in Fig. 6, measured values of “characteristic deflection” vary considerably, while simple moving averages of “characteristic deflection” are noticeably better in terms of variability. 3.3. Results of long-term monitoring and damage detection sensitivity The bus-based monitoring system has been applying for 3 target bridges on the in-service municipal bus network of Ube-city, Japan, from Dec. 2010 to now, namely 12 years long-term monitoring at present. Based on the accumulated field data (big data), this section describes the comprehensive verification results by the monitoring big data, thus accumulated over a period of the first 5 years of total 12 years monitoring. For this purpose, the influence of bus operating conditions (external disturbances) such as vehicle speed and the number of oncoming vehicles on changes in “characteristic deflection” (indicator used for damage detection) induced by in-service fixed-route bus operation is determined, and their correlations are reflected in conversion (correction) factors. All data on the 3 bridges

Fig. 5: Example of differences in standard deviation of “characteristic deflection” among data sections.

Fig. 6. Example of measured values of “characteristic deflection” and simple moving averages.