Browsing by Subject "Stress wave timing"
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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 Flexural Vibration Inspection Techniques to Rapidly Assess the Structural Health of Rural Bridge Systems(University of Minnesota Center for Transportation Studies, 2008-09) Brashaw, Brian K.; Vatalaro, Robert; Wang, Xiping; Sarvela, Kevin; Wacker, James P.Approximately 4,000 vehicle bridges in the State of Minnesota contain structural timber members. Recent research at the University of Minnesota Duluth Natural Resources Research Institute (UMD NRRI) has been conducted on vibration testing of timber bridges as a means of developing rapid in-place testing techniques for assessing the structural health of bridges. The technique involves measuring the frequency characteristics of the bridge superstructure under forced flexural vibration. The peak frequency of vibration was measured and compared to a set of load testing data for each of 9 bridges. Each bridge was also inspected using commercially available advanced inspection equipment to identify any major structural problems with individual bridge components such as timber pilings, pile caps, and girders. Two bridges were identified that needed immediate maintenance attention. The relationship between the load deflection data and the vibration characteristics showed a useful relationship and the results indicate that forced-vibration methods have potential for quickly assessing timber bridge superstructure stiffness. However, improvements must be made to the measurement system to correctly identify the 1st bending mode frequency of the field bridges. This global vibration technique has potential benefits for routine inspections and long-term health monitoring of timber bridge superstructures.