Browsing by Author "Vatalaro, Robert"
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Item Development of Cost-Competitive Timber Bridge Designs for Long-Term Performance(Minnesota Department of Transportation, 2020-06) Brashaw, Brian; Wacker, James; Fosnacht, Don; Aro, Matt; Young, Matthew; Vatalaro, RobertModern timber bridges have shown that timber is a durable option for primary structural members in highway bridges and can perform satisfactorily for 50 years or longer when properly designed, fabricated and maintained. However, various cost assumptions have indicated that timber bridges are more expensive than concrete bridges. This project was undertaken to better understand the benefits and costs of using timber bridges as a viable substitute for other bridge construction materials and designs. Two demonstration construction projects were completed to develop comparative information. A steel girder with a transverse glulam deck bridge with a curbless, crash-tested railing system was built, and a spike-laminated longitudinal deck bridge was constructed. Both projects were completed and allowed for a good comparison to be developed both in terms of project-specific cost and the time required for bridge construction completion. These projects showed that the main advantage of a timber bridge is the speed of superstructure construction with the other costs similar to that of other materials. It is clear from previous case studies, interviews with engineers, contractors, and suppliers, and the projects that timber superstructures can be installed within days to weeks, compared to months for other materials.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.