Kazuma KITAZONO

A Study on Evaluation of Measurement Performance, Temperature, and Temperature History Dependence of Low-cost Accelerometers in Construction of Bridge Monitoring Systems.

Takaaki IKEDA，Masataka SHIGA

In major earthquakes, emergency inspections of infrastructure are required. However, right after the events, it is not always possible to reach damaged sites quickly due to information confusion and road blockages. In addition, structural health problems in Japan, such as an ageing construction workforce and labour shortages, make it essential to improve the efficiency of inspections.
An effective solution to these problems is to use a bridge monitoring system. This study developes vibration measurement devices into a bridge monitoring system and evaluate the measurement performance of low-cost and compact sensors used for monitoring. Specifically, the study examines Micro-Electro-Mechanical System (MEMS) accelerometers and strain gauge-based accelerometers.
Although previous studies have also used compact and low cost sensors, problems have been yet identified in terms of measurement accuracy and system operation. Therefore, the objective of this study is to clarify the measurement accuracy of low-cost sensors and their characteristics in response to external environmental changes. The study investigates the vibration and tilt characteristics of the ADXL355 MEMS accelerometer, as well as the temperature history and temperature dependence of strain gauge-based accelerometers.
The experiments involved the use of a small shaking table and a cart comparing ADXL355 with the conventional ASW-5A accelerometers and the VSE-15D velocimeter under various vibration conditions. The research methodology includes a detailed description of the experimental equipment, sensors, shaking table settings, experimental conditions, data organisation and analysis procedures.
In the results and discussion, different shaking cases and measurement patterns were tested and analysed. As a result, by improving the system by separating ADXL355 and the microcontroller on separate circuit boards, it was confirmed that the standard deviation in the time history waveforms was reduced to 0.30 gal, which is lower than ASW-5A. In addition, the developed accelerometer system showed a noise reduction of approximately 1/2 to 1/3 in  Fourier amplitude spectrum.
Furthermore, under the same vibration and experimental conditions, the effect of temperature changes on the measurement performance of ASW-5A was evaluated. Although some effects of temperature were observed, no significant differences were found that would interfere with bridge damage assessment under the conditions of this study.
These results indicate that acceleration measurement using low-cost sensors can provide reasonably accurate measurements. However, challenges remain for practical applications, such as improving the accuracy of individual sensor modules and performing evaluations under real environmental conditions.

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