Computing continuous load rating factors for bridges using structural health monitoring data

One challenge to the wider adoption of structural health monitoring (SHM) in bridges is demonstrating the value added by the SHM system in maintenance and operation of the bridge to the owner. One way to do this is to use SHM systems and data to provide more accurate, frequent, and realistic live load ratings of a bridge, since the widely accepted load rating is the closest thing a bridge owner has today, to a “health” index of the structure. To address this need, a method has been developed that uses data from SHM systems in combination with conventional load rating equations, to compute continuous rating factors throughout the life of a bridge. The SHM-based ratings take into account slowly varying changes due to thermal effects and deterioration, as well as the actual in-service response due to live loads. The approach is demonstrated on Delaware’s 533-m cable-stayed Indian River Inlet Bridge. Continuous rating factors are computed and reported for periods of time and are compared to the AASHTO LRFR rating factors for the bridge. These rating factors are being used by the Delaware Department of Transportation to both assess the condition of the IRIB and to manage this important structure.