Browsing by Author "Schultz, Arturo E."
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Item 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.Item Crack and Concrete Deck Sealant Performance(Minnesota Department of Transportation, 2009-03) Johnson, Karl; Schultz, Arturo E.; French, Catherine; Reneson, JacobThe objective of this project is to define the current state-of-the-art regarding the use of bridge deck sealants and crack sealers to extend the life of reinforced concrete bridge decks. The report includes the information generated from a literature review and survey which focused on current and significant studies in the field of deck and crack sealing. The intent of the survey was to determine common practices for the use and application of these sealers in different States throughout the United States. Based on the information collected from the literature review and the survey, the best sealant materials and application practices are recommended for use in Minnesota and throughout the Midwest. The report consists of four sections including: (1) a synthesis of the literature review on the background, application, and performance of concrete deck sealants and crack sealers; (2) a summary of the survey conducted by Mn/DOT to determine the current selection criteria, materials, application practices, and findings from different states in United States; (3) an assessment of selection criteria, materials, application practices, and performance; and (4) conclusions, recommendations and areas in need of further research.Item Monitoring and Assessment Program for Wabasha County Bridge(1998-09) Fick, Damon R.; Schultz, Arturo E.; Bergson, Paul M.; Galambos, Theodore V.A 143-m (470-foot) span steel truss bridge, the Wabasha County Bridge crosses the Mississippi River at Wabasha, Minn. In November 1996, the Minnesota Department of Transportation (Mn/DOT) implemented a retrofit strategy to mitigate perceptible vibrations in several truss members at moderate and strong wind gusts. In this strategy, Mn/DOT installed a "central cord" of tubular members, halfway between top and bottom cords, to reduce the effective length of the truss members, thereby increasing the natural frequencies of vibration and reducing the amplitude of vibration and the associated strains. This report documents the monitoring and assessment program used to investigate the dynamic response and efficacy of the retrofit strategy for the Wabasha Country Bridge. Researchers determined amplitudes and frequencies of the vibration for the longest diagonal member. The measured frequencies are larger than those estimated before the retrofit and have resulted in reduced strains and displacements from vibration. Maximum strain levels at the quarter point of the member are estimated to be small after the retrofit, with peak values corresponding to 8.6 MPa (1.2 ksi).Item 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.Item Wakota Bridge Thermal Monitoring Program Part I: Analysis and Monitoring Plan(Minnesota Department of Transportation, 2013-05) Scheevel, Christopher J.; Morris, Krista M.; Schultz, Arturo E.In this work, a common refined design method is evaluated with respect to a recently constructed bridge. Two finite element models of the Wakota Bridge in South St. Paul, Minnesota, were produced, one using a design level program (SAP2000) and the other using a research level program (ABAQUS). These models were verified with respect to each other using linearly elastic materials and were found to behave similarly. After this verification, an arbitrary temperature load was applied to each model and the refined design method was evaluated for accuracy of reduced section properties with respect to the more descriptive progressive cracking solution simulated by ABAQUS. The refined design method was employed using two, four, and six stiffness segments at which stiffness is evaluated along the height of the pier walls. It was seen that accuracy increased as the number of stiffness segments increased and that four segments seemed to balance accuracy and time-commitment by the engineer adequately. A staged construction model of the Wakota Bridge was also built, using the design level program, which incorporates all time-dependent effects of the construction sequence as well as locked-in forces. A pile analysis was performed and appropriate rotational springs were found for Foundations 2 and 3. A simplified method for the determination of the rotational springs is discussed, and a range of effective lengths was found for use with this procedure. The staged construction model is used for field data correlation in Part two of this report. The staged construction model was also used to evaluate the different design options as described in the AASHTO LRFD. The two options given for accounting for reduced section properties were evaluated and compared. The refined analysis option and gross section option were compared for the Wakota Bridge and are shown to correlate to within about 10%. The two temperature application methods (Procedure A and B in the AASHTO LRFD) were also compared. As expected, Procedure B produced much larger design moments than that of Procedure A.Item Wakota Bridge Thermal Monitoring Program Part II: Data Analysis and Model Comparison(Minnesota Department of Transportation, 2013-05) Morris, Krista M.; Schultz, Arturo E.In this work, a common refined design method is evaluated with respect to a recently constructed bridge. Two finite element models of the Wakota Bridge in South St. Paul, Minnesota were produced using a design level program (SAP2000). These models were analyzed and their results compared to the data collected from the bridge. The second half of this study concerned the comparison of the collected field data with the values produced by evaluating the design-level finite element models previously created in Phase I of the project, and calibrating these models to provide an accurate prediction of the future behavior of the bridge. This was done by calculating changes in axial force and moment from strain data collected from the Wakota Bridge and changing various parameters within the design level model (DLM) in order to calibrate the models to the field data. The model using the refined design method was shown to correlate to the superstructure field data to within 2 percent, while between 13 percent and 35 percent correlation was seen between the model deploying the gross section method and the field data. The pier behavior predicted by the two models showed much less correlation to the field data. After calibration, it was possible to predict the general trend of the pier behavior, but the values of changes in moment did not correspond to the field data. This was especially true in Pier 4. Further consideration of the model parameters is necessary to fully calibrate the models. The two temperature application methods (Procedure A and B in the AASHTO LRFD) were also compared. The internal concrete temperature ranges measured in the field were much closer to the range specified in Procedure A.