Wireless transmission for health monitoring of large structures

In order to monitor the health of large structures such as highways, bridges, buildings, and dams, the outputs from various kinds of sensors, which are positioned at different places of structures, should be collected simultaneously and/or sequentially. However, the placements of sensors and wire connections are time consuming and cost expensive. Furthermore, the wires are easy to be damaged during the placement operation or in service. In this paper, the configurations of the wireless health-monitoring systems for structures are discussed. A novel wireless signal retrieval system, which is suitable for transmitting wirelessly the response signals of large structures, is proposed and developed. Special attention is paid to the low-frequency characteristics of the wireless transmitter/receiver pairs due to the following two reasons: The response frequencies of large structures are very low; on the other hand, the commercially available transmitter/receiver pairs have poor characteristics at low frequencies. The principles, feasibility, and configuration of the wireless-transmission system for the health monitoring of large structures are investigated. Also, experiments for testing the system performances are performed in the laboratory. The results show that the proposed wireless-transmission method and the developed system are suitable for the in situ and in-service wireless health monitoring of large structures.