Continuous monitoring of the Dowling Hall Footbridge

Continuous monitoring of structural vibrations is becoming increasingly common as sensors and data acquisition systems become more affordable and as system and damage identification methods develop. This study is focused on continuous vibration monitoring of the Dowling Hall Footbridge at Tufts University. A continuous monitoring system was designed and installed on this bridge. Automated system identification algorithms were used to extract the modal parameters of the bridge at constant time intervals. The accuracy of these algorithms was evaluated through a numerical study. Significant variability was observed in the identified natural frequencies of the bridge. This variability showed strong correlation with the measured temperatures. A nonlinear polynomial model was proposed to represent the relationship between the identified natural frequencies and measured temperatures. Finally, confidence intervals were estimated for the natural frequencies as a function of temperature presenting a simple damage index as the ratio of confidence interval outliers.