Tillmann, Anton S.

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.

Conventional methods for detecting vehicles for permanent travel monitoring stations have relied on detecting physical attributes of vehicles without correlating these with the specific vehicles and/or motor vehicle freight operators. However, by using a license plate reader camera, information can be gathered and cross referenced to other known data related to the specific vehicle assigned to the license plate. This could provide additional tools for enforcing overweight vehicles or targeting enforcement communication with freight carriers that consistently violate weight limits. The analysis conducted during this project compared machine-read license plates to manually collected license plates. The license plates were read as vehicle travelled highway speeds in a generally uncontrolled environment. Analysis is also provided that correlates hours of direct sunlight with accuracy of the automated reader. A second analysis was conducted as an effort to improve the accuracy of the Minnesota Department of Transportation's weigh-in-motion classification scheme and bring it in line with the Department's classification scheme for automatic traffic recorder stations (sites with axle-based detection that do not collect weight information).

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.