Modularized wireless dense sensor array for infrastructure monitoring

Localized nature of damage in structure requires local measurements for structural health monitoring (SHM). The major difficulties of making local measurements include (1) difficulty in exciting local, usually higher, modes in a structure, especially if the structure is large and complex; (2) the fact that structural vibrations are usually dominated by the lower frequency global modes. Structural health monitoring in this project is performed using a three-tier module-based approach. In the lowest tier, dense arrays of wireless strain gauges and accelerometers are deployed to measure the responses due to ambient or induced vibrations in a structure. The second tier consists of modules, each of which monitors one key member or area using a pre-selected set of sensors in the structure; these modules process the data to determine if local damage is detected. Information on possible local damage is then wirelessly sent to the top-tier, the base station, which uses the second-tier information to determine the health status of the structure. In this manner, damage is detected based on local data, which may change significantly if the measurements are made near the damage location. Experimental data are obtained to show that relatively small damage can be detected even when the global dynamic characteristics do not change significantly.