Collapse of the Wimer Covered Timber Bridge

On, July 6, 2003, the Wimer Covered Bridge, an historic covered wooden bridge located in southern Oregon, collapsed shortly after a pickup truck crossed over it. A local resident and his two grandsons were on the bridge at the time and sustained serious injuries. The bridge was originally built in 1892 and substantially rebuilt in 1927. The bridge underwent major rehabilitations in 1962 and 1985. The 2001 bridge rating concluded that it was safe to keep the bridge open to restricted traffic loads. The bridge collapsed due to extensive decay in the bottom chord at a panel point on the upstream truss. Engineers involved had numerous opportunities to identify the critical nature and deteriorated condition. Mistakes were made in both the analysis and in the inspections of the bridge. This paper addresses standard of care and the importance of assessing wood decay when analyzing a timber bridge structure.