Evaluation of Two Monitoring Systems for Significant Bridges in Texas

Two monitoring systems for bridges were evaluated for use by the Texas Department of Transportation. The first system was designed to increase the quantitative information obtained during a routine inspection of a steel bridge. The miniature, battery-powered data acquisition system selected for study has the ability to record a single channel of strain data and use a rainflow counting algorithm to evaluate the raw data. This system was considered to be particularly useful for evaluating fracture critical bridges. The second system provided long-term monitoring of bridge displacements using global positioning systems (GPS). The accuracy threshold of the GPS data was found to be 3 to 4 mm when the data were averaged for 24 hr. Significantly larger errors were observed for shorter averaging durations when satellite coverage was poor. Both monitoring systems are evaluated in this report.