As many engineers begin to implement life cycle cost analyses within the preliminary bridge design phase, there is a significant need for more reliable data on the expected service life of highway bridges. Many claims are being made about the expected longevity of concrete and steel bridges being 75 years or more, but few are based on actual performance data. Because engineers are least familiar with timber bridges, their expected longevity is often unfairly estimated at 20 years. A national scale project has been developed for the United States, headed by the USDA Forest Products Laboratory and the U.S. Federal Highway Administration. In this project, national cooperators including Federal Highway Administration, the U.S. Forest Service, Louisiana Department of Transportation, University of Minnesota Duluth, Iowa State University, Mississippi State University, Laminated Concepts, Inc. and Tom Williamson Timber Engineering, LLC will each inspect 15-25 timber bridges, using visual, probing, stress wave, and resistance microdrilling. The study results will help to provide a better understanding of the design, performance, and durability characteristics of timber bridge structures, which can improve future bridge design and preservation practices and ultimately extend service life. Lastly, the findings should assist with timber bridge service life expectancy when compared with alternative bridge materials.
