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With bridge infrastructure in Minnesota aging, advancing techniques for ensuring bridge safety is a fundamental goal of the Minnesota Department of Transportation (MnDOT). As such, developing health monitoring systems for fracture-critical bridges is an essential objective in meeting the stated goal. This report documents the acquisition, testing and installation of a 16-sensor acoustic emission monitoring system in the Cedar Avenue Bridge, which is a fracture-critical tied arch bridge in Burnsville, Minnesota. The overall goal of the project was to demonstrate that acoustic emission technology could be used for global monitoring of fracture-critical steel bridges. Project activities included the acquisition of the monitoring equipment, its testing to verify compliance with manufacturer specifications, installation of the equipment on the selected bridge, field testing to calibrate the system, development of data processing protocols for the acoustic emission (AE) data, and the collection of field data for a period of 22 months. Fracture tests of notched cantilever steel beams were conducted in the laboratory to provide characterization data for fracture events.

With bridge infrastructure in Minnesota aging, advancing techniques for ensuring bridge safety is a fundamental goal of the Minnesota Department of Transportation (MnDOT). Developing health monitoring systems for fracture-critical bridges is an essential objective in meeting the stated goal. This report documents the implementation of two, 16-sensor, acoustic emission monitoring systems in one of the tie girders of the Cedar Avenue Bridge, which is a fracture-critical tied arch bridge spanning the Minnesota River between Bloomington and Eagan, MN. The goal of the project is to develop a process for using acoustic emission technology to monitor one of the girders of the bridge while continuously collecting data from the monitoring systems. Given the cost of acoustic emission sensing equipment, an approach was adopted to space the sensors as widely as possible. Fracture tests were conducted on a specimen acoustically connected to the bridge to simulate fracture in a bridge member. Sets of criteria were developed to differentiate between acoustic emission data collected during fracture and ambient bridge (i.e. AE noise) data. The sets of criteria were applied to fracture test data and AE noise data to determine the validity of the criteria. For each criteria set, a period of Cedar Avenue Bridge monitoring data was analyzed. The results of the analysis of each period showed that the criteria could differentiate between the bridge AE noise data and the fracture test data. The AE noise data never met all of the criteria in the set, whereas all criteria were met during each of the applicable fracture tests.