Research Reports

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https://hdl.handle.net/11299/241

The Center for Transportation Studies' research reports present the results of University of Minnesota projects in all areas of transportation research.

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Now showing 1 - 5 of 5

Acoustic Emission Equipment for Infrastructure Monitoring
(Minnesota Department of Transportation, 1999-01) Shield, Carol K.
This system consists of acoustic emissions sensors, preamplifiers, filers, an AE monitor, and a digital oscilloscope. The system has been applied successfully to both steel and concrete structures and used to detect brittle fracture and low-cycle fatigue failures in welded steel joints and crack propagation in cover-plated rolled bridge girders, in the field and in the laboratory. The AE system detected initial cracking during the flexural crack testing of two high-strength concrete prestressed bridge girders. The acoustic emission monitoring of bond tests also provided insight into the behavior of the bond between glass fiber reinforced polymer rebar and concrete.
Acoustic Emission Monitoring of a Fracture-Critical Bridge
(Minnesota Department of Transportation Research Services & Library, 2014-03) Schultz, Arturo E.; Morton, Daniel L.; Tillmann, Anton S.; Campos, Javier E.; Thompson, David J.; Lee-Norris, Alexandria J.; Ballard, Ryan M.
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.
Acoustic Emission Monitoring of Fatigue Cracks in Steel Bridge Girders
(Minnesota Department of Transportation, 1999-09) McKeefry, Jay A.; Shield, Carol K.
This report presents results from a laboratory study and field implementation of acoustic emission monitoring of fatigue cracks in cover-plated steel bridge girders. The acoustic monitoring successfully detected growing fatigue cracks in the lab when using both source location and a state of stress criteria. Application of this methodology on three field bridges also proved successful by detecting a propagating crack in two of the bridges and an extinguished crack in a third bridge. Researchers tested a double angle retrofit, designed by the Minnesota Department of Transportation, both in the lab and in the field of girder with fatigue cracks in the top flange. This retrofit does not require removal of concrete deck, and only involves bolting the retrofit to the bridge girder web. The double angle retrofit applied to laboratory test girder resulted in a reduction of flange stresses by 42 percent. Field implementation of the retrofit had mixed success. On one bridge, stress ranges in the cracked flange was reduced by 43 percent. However, on a second test bridge, the reduction was only 8 percent, likely due to the inadequate space for proper installation of the retrofit.
Development of an Advanced Structural Monitoring System
(Minnesota Department of Transportation Research Services Section, 2010-11) Schultz, Arturo; Thompson, David
With bridge infrastructure in Minnesota aging, advancing techniques for ensuring the safety of bridges and motorists is a fundamental goal of the Minnesota Department of Transportation (Mn/DOT). As such, developing health monitoring systems for fracture critical bridges is an essential objective in meeting the stated goal. This report applies the methodology and uses the information of a previous Mn/DOT report to investigate, select, and design a bridge health monitoring system for the Cedar Avenue Bridge which is a fracture critical tied arch bridge in Burnsville, Minnesota. An investigation of monitoring needs for the Cedar Avenue Bridge was undertaken. In addition, the authors reviewed literature with the goal of determining the most applicable monitoring technology that is commercially available and which fulfills the required bridge monitoring needs. Once a monitoring technology was selected, the authors selected a vendor, using a computer-based program developed in the aforementioned Mn/DOT report, to select a suggested system of monitoring equipment for Mn/DOT to purchase. Finally, the report describes multiple alternatives for monitoring scales, scopes, locations, and capabilities, with global monitoring of the most critical members and connections of the bridge as the authors’ recommendation. A procedure for installation of the suggested bridge health monitoring system follows the authors’ recommendations and is applicable to any of the monitoring alternatives presented in this report.
Protocols and Criteria for Acoustic Emission Monitoring of Fracture-Critical Steel Bridges
(Center for Transportation Studies, University of Minnesota, 2015-06) Tillmann, Anton S.; Schultz, Arturo E.; Campos, Javier E.
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.