Analysis of the Acoustic Response of a Railroad Bridge

Aging infrastructure (e.g., railroad bridges) requires frequent inspections to assess their structural integrity. However, the large amount of existing infrastructure, and the distance between these structures present significant challenges to inspectors. A simple, method to monitor the structural integrity of infrastructure is needed. Acoustics-based technologies represent a simple, and relatively inexpensive, technique to monitor the integrity of a structure. To develop these techniques, designers must understand the frequencies and sound pressure levels that develop from a typical bridge structure. Infrasound is acoustic energy whose frequency is below that of human perception. Large infrastructure, such as bridges, emits such signals at their natural or driven frequencies of vibration, providing an indication of the structural condition. The feasibility of this type of monitoring was recently evaluated during an in-service load test of a single through-truss railroad bridge at Ft. Leonard Wood, MO, in conjunction with local infrasound monitoring.