Remote Bridge Monitoring Using Infrasound

As transportation infrastructure continues to age, new methods of noncontact sensing should be evaluated and, if found suitable, used for bridge monitoring and structural health assessment. This study highlighted the use of infrasound monitoring, a geophysical technique utilizing acoustics below 20 Hz, as one possible solution for noncontact, nonline-of-sight bridge health monitoring. The study focused on the technique of infrasound for infrastructure monitoring with a detailed case study involving a steel, two-girder bridge in northern California. Infrasound was used to detect natural modes of the structure from a distance of 2.6 km. The frequencies detected infrasonically were validated with data collected by on-structure accelerometers. The noncontact nature of this structural assessment approach has potential to supplement traditional structural assessment techniques as affordable, remote, persistent monitoring of transportation infrastructure. Implications for use of this technology were also discussed alongside specific applications for scour monitoring and postdisaster assessment.