Using conventional approaches, an overpass spanning the Garden State Parkway did not rate, despite the seemingly satisfactory visual appearance of the structure. Specifically, calculations indicated that the exterior girders had dead load demand that exceeded the member capacity. As such, the structure was slated for replacement. Intelligent Infrastructure Systems personnel were brought on to determine if refined load rating procedures could rapidly and accurately determine whether the unsatisfactory ratings were accurate or simply a function of conservative rating procedures.
This implemented application included a total of 52 sensors and involved crawl-speed and static truck tests, ambient vibration monitoring and multiple-input, multiple output modal impact testing. This application was led by Drs. Moon and Aktan and was carried out by 6 personnel in 7 hours. Key response metrics such as distribution and impact factors, degrees of composite action, strain / displacement profiles, and modal parameters were captured. An FE model was calibrated and used for refined load rating analysis, demonstrating that the lateral load distribution between the girders was more robust than initially anticipated. The finite element model-based ratings were used to recommend against the removal of the bridge.