Development of a smart-device-based vibration-measurement system: Effectiveness examination and application cases to existing structure

After the 2011 Great East Japan Earthquake, long-term vibration measurement using high-density instruments is one of the most critical issues for structural-health-monitoring owing to increasing deterioration and threat of future large earthquakes. Because of the high initial and running costs of traditional monitoring systems, smart-device-based measurement system is considered as a simple and easy solution. In this paper, the effectiveness of in-built sensor, data transfer via wireless local area network, data acquisition to a synchronize cloud server, and trigger function using shaking table tests were firstly examined. A measurement system including a group of sensors has been established successfully based on the control center from which the trigger command can be send to other sensors immediately as any sensor/sensors is/are triggered. Then, the system is applied to seismic-response and environment-vibration measurement at existing structures. Results show that the observable acceleration level of smart devices is more than 5gal in the frequency range of 0.1 to 10Hz. The possible sampling rate is 100Hz. Though it is unstable, correction methods have been proposed. Continuous measurement and data transfer is possible without data loss. Dynamic properties extracted from smart-device-based system is very similar to those extracted from high-quality-sensor-based system.