Recently, many catastrophic natural disasters took place such as massive earthquakes, tsunamis, and storms all around the world, in the U.S., Italy, India, Japan, China, Taiwan and Mexico, for instance. However, it is not easy to secure their safety because they are constantly exposed to deterioration due to aging, excessive load, and carelessness, and also natural disasters as well, thus threatening public safety. It is important all civil structures are securely built and maintained from the very beginning until the end of their life since their insecurity may endanger human lives and public well-being. Therefore, the WUMS is proved valid as a SHM, and its outstanding performance is also proven. The analysis of dynamic characteristics also showed that the wireless acceleration responses in real-time represented satisfactorily the dynamic properties of structures. The test results proved that the WUMS was able to secure stable communication far up to nearly 800 m away by acquiring wireless responses in realtime accurately, when compared to the displacement and acceleration responses which were acquired through wired communication. To verify its performance, the following tests were performed: (i) A test to see how far communication is possible in open field, (ii) a test on a shaker to see how accurate responses are, (iii) a modal test on a bridge to see how exactly characteristic real-time dynamic responses are of structures.
The WUMS is designed to measure diverse types of structural responses in realtime based on wireless communication, allowing users to selectively use WiFi RF band and finally working in standalone mode by means of the field-programmable gate array (FPGA) technology.
Therefore, this study is aimed at developing a wireless unified-maintenance system (WUMS) that would satisfy all the requirements for a disaster preventive SHM system of civil structures.
Furthermore, it should be capable of prompt processing and realtime wireless communication of a huge amount of data. Second, it also requires standalone power supply to guarantee its immediate response in crisis (e.g., sudden interruption of normal AC power in disaster situations). A disaster preventive structural health monitoring (SHM) system needs to be equipped with the following abilities: First, it should be able to simultaneously measure diverse types of data (e.g., displacement, velocity, acceleration, strain, load, temperature, humidity, etc.) for accurate diagnosis.
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