There is a growing need for a cost-effective and accurate method of determining the structural integrity of our nation's bridges. The Sawtooth Wireless Structural Assessment System can be used to monitor the structural integrity of a bridge and locate abnormal stress points when necessary. The system incorporates two main components: a permanent monitoring system and a portable locating system. The Permanent Monitoring System is used to detect developing structural problems by comparing changes in a bridge's vibration "signature" over time. When stimulated by traffic on the bridge, a bridge's beams vibrate at their specific resonant frequencies, providing a unique signature for each bridge. Permanent vibration sensors installed on the bridge structure can continually monitor the spectra of these vibrations. Changes in the spectra over time would alert investigators to possible changes in structural integrity of the bridge. The Portable Locating System can be focused on specific areas of interest if changes to the bridge's structural integrity are suspected. The load on a bridge places stress on its individual beams, which affects the propagation of stress waves along the entire structure. An array of sensors can measure the velocity and attenuation of elastic vibrations traveling along individual beams. These measurements can be converted into a velocity and attenuation image of the bridge, with different colors representing stress concentration areas.
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