Overview of the National Timber Bridge Inspection Study

Abstract

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, but few are based on actual performance data. Because engineers are least familiar with timber bridges, their expected longevity is often unfairly estimated at only 25-30 years. A national scale project has been developed for the United States, led by the USDA Forest Products Laboratory and the U.S. Federal Highway Administration. In this project, a group of 6 bridge inspection teams, representing the major climate zone types in the U.S., each inspected at least 20 timber bridges. Nondestructive inspection techniques included visual, probing, sounding, stress wave, and resistance micro-drilling. The study results will help to provide a better understanding of the design, performance, and durability characteristics of timber bridge structures. This paper will highlight the overall inspection findings, which were instrumental in reliably estimating the expected service life for timber bridge superstructures and help support future designs that employ life cycle and sustainable features.

Citation

Wacker, James P.; Brashaw, Brian K.; Jalinoos, Frank. 2013. Overview of the National Timber Bridge Inspection Study. In: USDA Forest Service, Forest Products Laboratory, General Technical Report, FPL-GTR-226. pp. 610-615.