, Former Professor, Civil, Environmental and Geo-Engineering
The integrity of bridges has become a major public safety concern. The goal of this project was to improve the safety and operation of bridges by developing response-modification technology for bridges and their components. The new technology monitors structural health and controls stress paths to protect bridges from live loading. Such loads include heavy but legal trucks, overloaded and illegal trucks, or catastrophic loads such as vehicle strikes, earthquakes, or blasts. This project represented a first step toward enhanced operation and safety of bridges; the overall initiative also included the incorporation of traffic monitoring by video into the process. This research showed that safe extension of the service life of existing bridge structures is possible through bridge health monitoring and structural response modification. The efficacy of response modification techniques on a realistic bridge system were demonstrated using the Cedar Avenue Bridge in Minnesota as a specific example. The Cedar Avenue Bridge is a steel tied arch bridge, which means that it is fracture critical. Due to the non-redundant nature of a fracture critical bridge, fatigue failure could be catastrophic. Previous research has shown that stress concentrations exist at the joints where the hangers and floor beams are attached to the box girder. Using a simulation of response modification on the Cedar Avenue Bridge model, stress ranges were reduced on the specific details of concern. Modeling using a scissor jack and simple damping device has shown that stress ranges can be reduced by approximately 39 percent, which can lead to a life extension of as much as 346 percent.