Development of a multi-hop wireless sensor system for the dynamic event monitoring of civil infrastructure and its extension for seismic response monitoring

摘要

The dynamic response of civil infrastructures under transient dynamic events is of particular interests for structural engineers, because these event-induced responses usually provide useful insights into the real dynamic behavior of civil infrastructures under extreme conditions. Monitoring these dynamic event induced vibrations are among the most frequently conducted measurements and experiments in the structural engineering field, and a cheaper, simpler and more flexible monitoring system is always under pursuit of civil engineers. One particular such request comes from the seismic response monitoring applications. Seismic response monitoring for general civil infrastructure is critical in high-risk earthquake areas like Japan. It contributes to earthquake safety by providing quantitative measurement that enables improved understanding and predictive modeling of the earthquake response of these engineered systems. However, due to the limitations of the current monitoring systems, such seismic response records of general civil infrastructure are usually not available. Therefore, this research describes a novel development of an autonomous dynamic event monitoring system using Wireless Smart Sensor Network(WSSN), which is further extended to support the purpose of long-term seismic response monitoring. This developed WSSN monitoring system is portable and low-cost, it has a potential to provide long-term seismic response monitoring for a wide range of civil infrastructure. This system can run on existing power sources readily available in common civil infrastructure and thus is able to perform long-term continuous sensing as demanded by the seismic response monitoring applications. A quick and stable event detection method is developed to trigger the recording of the complete seismic response and also eliminate possible false alerts caused by unexpected disturbance. Long-term network-wide time synchronization is guaranteed by a customized long-term Flooding Time Synchronization Protocol(FTSP) so that the all sensor nodes in the network can provide consistent time records of their captured seismic response. An efficient multi-hop service module is also incorporated into the system to disseminate commands and accommodate the need of collecting data in a reliable and prompt manner after major earthquakes, the integrated multi-hop data collection protocol provides a theoretically optimum data collection efficiency. Various experiments have been done to validate the developed programs. Suggestions are also given towards the final realization of successful long-term implementation of the developed monitoring system.