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Project Information
Project ID:   FHWA-PROJ-08-0047
Project Name:   Evaluating Naturally Durable Wood Species for Repair and Rehabilitation of Aboveground Components in Covered Bridges
Project Status:   Completed
Start Date:  October 1, 2008
End Date:  October 31, 2013
Contact Information
Last Name:  Duwadi
First Name:  Sheila R
Telephone:  202-493-3106
E-mail:  sheila.duwadi@dot.gov
Office:   Office of Infrastructure Research and Development
Team:   Hazard Mitigation Team [HRDI-50]
Program:   National Historic Covered Bridge Preservation Program
Project detail
Roadmap/Focus area(s):   Historic Preservation
Project Description:   Covered bridges are designed for protection from the elements, but it is difficult to protect all wood components from moisture exposure. Some areas of the structures, such as weatherboarding and wood members near the ends of the bridges, are particularly susceptible to wind-driven precipitation. Consequently, biodeterioration from decay and insects is frequently responsible for replacement of aboveground covered bridge components. Naturally durable domestic wood species, particularly underutilized or invasive species, should provide a suitable alternative to chemically treated wood products for repair and replacement of aboveground components of covered bridges. Chemical extractives have long been recognized as key features that impart natural durability in the heartwood of certain wood species. The extractives themselves have been evaluated for use as environmentally friendly preservatives or additives to coatings, but little is known about the chemical makeup of the extractives. Research is needed to isolate, identify, and characterize the chemical extractives believed to be responsible for high resistance to decay and insects in well-known and lesser-known durable domestic wood species. A comparison of chemical properties of well-known and lesser-known wood species will improve our understanding of the differences in physical properties and offer opportunities as suitable materials for repair and rehabilitation of covered bridge components in protected outdoor exposure. The chemical component(s) responsible for imparting durability could also provide new environmentally benign wood protection systems for above ground components of covered bridges.
Goals:   The objective is to identify and characterize durable wood species resistant to decay and insects.
Product Type:   Article
Research report
Technical report
Test Methodology:   This study will include analytical and experimental work both in the laboratory and in the field.
Other Information:   Funding is $131,717 from the Federal Highway Administration plus $30,000 from the Forest Service, Forest Products Laboratory.
Expected Benefits:   The expected benefit is the identification of durable wood species that owners can use in building new and/or rehabilitating timber structures.
Deliverables:   The overall findings of this study indicate that several of the species evaluated have benefits for use in above-ground replacement components for covered bridges. For complete information please consult the final report.
Project Findings:   The overall findings of this study indicate that several of the species evaluated have benefits for use in above-ground replacement components for covered bridges.  For complete information please read the final report by Kirker, Clausen, Blodgett, and Lebow titled "Evaluating Naturally Durable Wood Species for Repair and Rehabilitation of Above-Ground Components of Covered Bridges" FPL-GTR-224 which can be obtained online at www.woodcenter.org or at the following link:http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr224.pdf
FHWA Topics:   Roads and Bridges--Structures
TRT Terms:   Covered Bridges
Wooden Bridges
Infrastructure
Bridges
Wood
Rehabilitation (Maintenance)
Biodeterioration
Research
FHWA Disciplines:   Environment
Structures
Subject Areas:   Bridges and other structures
Research

 

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