Response Modifi cation for Enhanced Operation and Safety of Bridges

This report shows that safe extension of the service life of existing bridge structures is possible through bridge health monitoring and structural response modification. To understand bridge health monitoring and structural response modification and control, it is necessary to examine: 1) common bridge vulnerabilities, 2) bridge loading models, 3) response modification devices, and 4) bridge monitoring systems. 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 and is of concern. Previous research has shown that stress concentrations exist at the joints where the hangers and floor beams are attached to the box girder [7]. Using a simulation of response modification on the Cedar Avenue Bridge model, stress ranges have been reduced on these specific details that are of concern. Modeling using a scissor jack and simple damping device has shown that stress ranges can be reduced by approximately 39% which can lead to life extension of as much as 346%. The authors and the University of Minnesota do not endorse products or manufacturers. Any trade or manufacturers' names that may appear herein do so solely because they are considered essential to this report.