About the research
The structural capabilities of timber have been widely known for centuries as evidenced by the fact that it has been the primary building material for many generations. Recently, there have been even further improvements to timber construction components as they are now being specially fabricated into highly engineered cross-sections. Unfortunately, the integration and use of these engineered timber materials/sections in bridge construction is still slow to progress, in large part due to the negative perception of timber. The negative perception that timber has obtained, and unfortunately sustained, over the years is in large part due to timber bridges that have performed poorly, not because of material inadequacies, but because of insufficient design and protection, often more related to serviceability than structural adequacy.
When properly designed and protected from elements such as water, insects, and fire, timber is a structurally capable, cost-effective, and aesthetically pleasing material suitable for many structural applications. In response to the negative performance and perception of timber bridges in the past, significant research has been completed related to the development of design details, improved preservatives, and advanced engineering concepts. As a result, the performance of these structures has been greatly enhanced; unfortunately, the perceptions of these structures has not been enhanced to the same degree.
In the search for additional bridge replacement alternatives, the Buchanan County Engineer has been working with the National Center for Wood Transportation Structures and a timber fabricator to develop the next generation timber bridge. The goal with the development of this concept is to increase the structural efficiency of timber bridges and increase longevity by creating a composite deck-girder system and the application of an epoxy overlay, respectively. If successful, this development has the potential to increase viable bridge options for use on Iowa’s roadways.
This work is in support of the Buchanan County project and is aimed at providing needed laboratory test results, construction documentation, design documentation, and field performance evaluation. The objective of this project is to aid in the development of the next generation timber bridge by performing laboratory testing of an innovative, field-installed girder-to-deck connection detail that results in a composite structure, documenting the construction of the Buchanan County Bridge using video and other formats, and performing a field performance evaluation that includes measuring changes in live load response over time and documenting the performance of the thin, epoxy overlay.