Design and Deployment of a Continuous Monitoring System for the Dowling Hall Footbridge

Continuous monitoring of structural vibrations is becoming increasingly common as interest in structural health monitoring (SHM) grows, as equipment becomes more affordable, and as system and damage identification methods develop. In vibration-based SHM, the dynamic modal parameters of a structure may be used as damage-sensitive features. The modal parameters are often sensitive to changes in temperature or other environmental effects, so continuous monitoring systems must also measure environmental conditions. Necessary components of a continuous structural monitoring system include a well-designed sensor array, data acquisition and logging equipment, data transfer and storage functions, and routines for extracting modal parameters from vibration measurements. All processes must be automated to handle the large volume of data generated. Such a monitoring system has been installed on the Dowling Hall Footbridge at Tufts University and is currently providing live data for research in vibration-based SHM. This paper focuses on (1) the design and installation of the system hardware and (2) the strategy used to automate the monitoring system. Successful automation of modal analysis is emphasized as the key component of this strategy. To highlight the system's capabilities, the pattern of variation of the natural frequencies is examined and compared with environmental data.