Browsing by Subject "Structural health monitoring"
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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 Applying the DMAIC method for developing a PVDF matrix composite for integrated structural load sensing(2014-08) Haghiashtiani, GhazalehThis thesis introduces a new carbon fiber reinforced composite structure that uses polyvinylidene difluoride (PVDF) as the matrix material instead of the polymers that are typically used. The piezoelectric properties of PVDF enable the proposed composite material to act both as the structure and as an integrated sensor for in situ structural health monitoring. In this study, the fabrication process, the polarization process, and the mechanical and piezoelectric characterization of the composite structure are discussed. In addition, the DMAIC method was applied to the polarization process in order to identify the factors affecting the degree of polarization. As part of the improve phase, a 23 factorial design of experiment (DOE) was performed to investigate the optimal conditions of the identified factors for the polarization process. Lastly, the future market potential of the proposed composite structure is explored by applying strategic market analysis tools including SWOT analysis, Ansoff's matrix, and technology S-curve.Item Bridge Health Monitoring and Inspections – A Survey of Methods(Minnesota Department of Transportation, 2009-09) Gastineau, Andrew; Johnson, Tyler; Schultz, ArturoSince the collapse of the I-35W bridge in August 2007, bridge health monitoring has become an area of intense interest. This report defines terminology related to bridge health monitoring and provides a general glossary of available monitoring systems. The glossary is meant to help readers make an informed decision by understanding how different systems function and their strengths and weakness. The authors developed a questionnaire to send to commercial companies offering monitoring systems. Of the 72 questionnaires that were sent to commercial companies, 38 companies responded and are included in this report. From information provided with these questionnaires, available commercial systems are briefly summarized. Criteria for system evaluation were developed to help the bridge owner narrow down company choices for bridge application. After the owner answers a set of questions pertaining to a particular bridge, a program developed in Microsoft EXCEL helps the bridge owner decide the best system for a particular situation. An example is provided for program clarity. Once company choice is narrowed down, additional criteria were developed to aid in final product choice.Item Carbon Nanotube Addition to Cement-Sand Based Piezoelectric Composites(2016) Kadlec, Alec; Wang, Shifa; Zhao, PingCarbon Nanotubes (CNTs) were added to a cement-sand based piezoelectric composite with consideration of Structural Health Monitoring (SHM) to improve conductivity and poling efficiency, increasing piezoelectric effects. The addition of CNTs to the composite structure formed continuous electric networks between the Lead Zirconate Titanate (PZT) particles, allowing more effective poling. Samples of 50 volume percent PZT were fabricated with a mixture of PZT powder, white Portland cement, graded silica sand, CNTs and a superplasticizer, and cured at room temperature. The properties of the composite, including piezoelectric coefficient and sensing effects were characterized for a range of CNT inclusion from 0 to 0.9 vol %. Results showed that CNT inclusion allowed for effective room temperature poling, improving piezoelectric properties of the composite. The modified composite was optimal at 0.6 vol % CNTs.Item Development and Integration of Advanced Timber Bridge Inspection Techniques for NBIS(Center for Transportation Studies, University of Minnesota, 2015-01) Brashaw, Brian; Dahlberg, Justin; Hosteng, Travis; Wacker, JamesMinnesota has over 2,000 bridges that contain structural timber in the superstructure or the substructure. Historically, inspections for timber bridges have been mostly limited to visual inspection, hammer sounding and probing. These techniques have proven appropriate for advanced decay detection, but are inadequate for early stage or internal deterioration. During this project, new advanced inspection techniques and equipment were identified that were capable of improving the quality of timber bridge inspection. This equipment and technologies were introduced into routine bridge inspections through the development of standard inspection protocols, integration of the results into bridge data management software, development of a customized inspection manual, outreach training for MnDOT districts and state counties, recommendation of equipment purchases, and completion of an economic assessment on the use of advanced inspection techniques. Implementation of these inspection techniques will support the long-term service life of Minnesota’s timber bridges and will improve the safety and reliability of Minnesota’s bridges.Item Development of an Advanced Structural Monitoring System(Minnesota Department of Transportation Research Services Section, 2010-11) Schultz, Arturo; Thompson, DavidWith 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.Item Development of Flexural Vibration Inspection Techniques to Rapidly Assess the Structural Health of Rural Bridge Systems: Phase II(Minnesota Department of Transportation, 2009-12) Brashaw, Brian K.; Vatalaro, Robert J.; Wang, Xiping; Verreaux, Matthew; Sarvela, KevinCurrent timber bridge inspection procedures used in Minnesota and across the United States are mostly limited to visual inspection of the wood components. Use of advanced techniques like stress wave timing, moisture meters, resistance drills will significantly improve the reliability of the inspections but these inspection techniques are time consuming. The objective of this project was to conduct vibration testing of dowel laminated timber bridge systems to better understand the potential for using vibration testing to assess the structural health and condition of bridges in Minnesota. A second key objective was to improve and automate the vibration testing system that is currently being used. This research showed that the forced vibration system developed is an effective tool for conducting forced vibration tests of timber bridges and that there is a noted increase in frequency during each successive stage of construction. A reliable means for assessing the peak frequencies and an identification of the mode still needs to be developed for this system to use the vibration response to predict the EI product for use in load ratings. Each bridge has a unique set of vibration characteristics that were identified using the automated system. These characteristics showed peaks in amplitude as the frequency of the vibration was increased from 0 - 35 Hz during testing. It is believed that monitoring of the characteristic vibration response for each bridge would be a means of identifying changes in structural health over time due to wood decay, accidents, vandalism, or lack of maintenance.Item Displacement Monitoring of I-35W Saint Anthony Falls Bridge with Current Vibration-Based System(Minnesota Department of Transportation, 2019-01) Brown, Riley J; Gaebler, Karl O; Shield, Carol K; Linderman, Lauren ESince the opening of the I-35W Saint Anthony Falls Bridge in 2008, over 500 sensors have been collecting data to better understand the behavior of post-tensioned concrete box girder structures. Recent research in the accelerometers installed on the bridge indicates they can be effectively used in a vibration-based structural health monitoring system, but previous studies have shown that natural frequency alone may not be sufficient to determine the performance of the structure. Vertical displacements were believed to be a simpler performance measure as direct comparisons can be made with design calculations and maintenance guidelines. To avoid the shortcomings of conventional displacement measurement options, this study focuses on using the currently installed accelerometers to estimate the vertical displacements of the southbound bridge. The proposed technique utilizes up-to-date modal parameters within a dual Kalman filter to estimate the vertical displacements of the structure from noisy acceleration measurements. When applied to the I-35W Saint Anthony Falls Bridge, it was found that the dual Kalman filter approach captures only dynamic displacements due to relatively slow loading (e.g., traffic loading and thermal loading) and the corresponding low-frequency static displacements are likely too small for GPS measurements due to the high stiffness of the structure.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 Scour Monitoring Technology Implementation(Center for Transportation Studies, University of Minnesota, 2014-09) Lueker, Matthew; Marr, JeffBridge scour is the removal of sediment around bridge foundations and can result in the failure of the bridge. Scour monitoring is performed to identify unacceptable scour on bridges considered to be scour critical and determine when scour reaches elevations that could cause potential bridge failure. Two types of monitoring are available: portable monitoring and fixed monitoring. Prior to this project, MnDOT was only using portable monitoring devices, which requires the deployment of personnel to make physical measurements of scour depths. For some scour critical bridges, especially during high-water events, fixed instrumentation capable of continuous scour monitoring was preferred, but MnDOT lacked the experience or expertise to install this type of equipment. This project installed fixed monitoring equipment at two bridge sites and monitored them for three years to determine the effectiveness and reliability of fixed scour monitoring deployments. Several device options were installed to allow MnDOT to analyze the installation and performance of different types of sensors. Both systems operated for the three years with some outages due to various causes but overall performance was acceptable. The outages were mostly related to power issues and communication issues. Valuable lessons were learned through the deployment, which may be applied to future installations. The deployment executed in this project has provided the confidence to deploy other fixed scour monitoring equipment at key bridges around the state of Minnesota. In addition, the data collected during deployment of the scour monitoring equipment has been stored and provides insight into scour processes. This data can be used by other research groups for design or research purposes.