Jeffrey A. Laman*, Thomas E. Boothby* and James W. Bintrim** * The Pennsylvania Slate University, USA** HDR, Pittsburgh, USA
Dynamic testing has been applied to four late nineteenth-century primitive stone arch bridges, located in Hunter don County, NJ, USA. The structures were tested dynamically using a loaded truck and a drop-weight device. Measurements were taken of the vibration velocities in various locations and orientations throughout the bridge. Based on the observed vibration velocities, the condition of the bridge could be assessed from the vibration intensity that incorporates peak-to-peak velocity, comparison of the expected fundamental frequency with the observed fundamental frequency, and measurement of peak-to-peak vibration velocity under expected loading. All of these indicators correctly identified two of the structures as significantly damaged; the other two were generally found to be in reasonably good condition. The variation in the measurements taken at different locations throughout the bridges also appears to assist in the identification and location of damage to the structure.