National Covered Bridges Recording Project:
HAER Documentation
HAER Surveys
HAER has surveyed 86 covered bridges as part of the National Covered Bridges Recording Project. The archival documentation produced for these surveys is housed at the Library of Congress in the HAER Collection.
Fly-Through Animation
West Union Bridge (HAER IN-105) is the work of the prolific Indiana covered bridge builder Joseph J. Daniels (1826-1916). It is an excellent example of his use and development of the Burr-Arch Truss. Read more about the bridge and watch the fly-through.
HAER Engineering Studies
The following engineering studies have been carried out or are in progress:
Burr-Arch:
- Gilpin's Falls Covered Bridge (HAER MD-174)
- Pine Grove Bridge (HAER PA-586)
- Strength of Burr-Arch Trusses (HAER OH-138, recently completed)
Town:
- Bath-Haverhill Bridge (HAER NH-33)
- Brown Bridge (HAER VT-28)
- Contoocook Railroad Bridge (HAER NH-38)
- Cornish-Windsor Covered Bridge (HAER NH-8)
Other truss types:
- Childs: Harshman Bridge (HAER OH-126)
- Modified Multiple Kingpost: Taftsville Bridge (HAER VT-30)
- Pratt: Sulphite Railroad Bridge (HAER NH-36)
- Queenpost: Morgan Bridge (HAER VT-33)
- Smith: Cataract Falls Bridge (HAER IN-104)
- Smith: Structural Study of Smith Trusses (HAER PA-645)
Recently Completed Engineering Study: Strength of Burr-Arch Trusses
Significance: Beginning about 1804, Theodore Burr (1771-1822) built wooden covered bridges that combined a multiple-kingpost truss with an arch into one structural form. The Burr arch-truss is now the most common type in the inventory of extant nineteenth-century covered bridges in the United States. However, there is considerable variability in the geometric parameters and details used for actual bridges. Results of a survey of thirty Burr arch-truss bridges were used to design and fabricate a 2/3-scale symmetry model of a Burr arch-truss. This model was load-tested to investigate the behavior of Burr arch-trusses at strength. The overall observations from the tests are that strength is connection-controlled, flaw-controlled, and generally brittle. Some general principles of strength limit state analyses of structural systems are presented in the context of Burr arch-trusses.
Authors: Dario Gasparini, Stacey Hursen, Gregory Willenkin, Kamil Nizamiev, Case Western Reserve University, 2015.
Project Information: The Strength of Burr-Arch Trusses research project was facilitated through Cooperative Agreement No. P10AC00630, between NPS and CWRU. Christopher H. Marston, HAER Architect, served as project leader. Prof. Dario Gasparini developed and led the research, with engineering students Stacey Hursen, Gregory Willenkin, and Kamil Nizamiev, all of Case Western Reserve University. Rudy Christian constructed the truss model, assisted by his wife Laura and Andrew Schaeffer. David Simmons, James Cooper, Campbell Fitzhugh, and Linda Gasparini assisted with the survey of Burr arch-truss bridges in Ohio, Indiana, and Pennsylvania.
Download the Report: The report will be available on the Library of Congress' website next year. Until then, you can download the report here (pdf, 12 MB).
Supplemental Materials: The following files are provided for use in the peer-review process. We will post them in a different format for public use once the study is published. The video and photographs show the load-testing of the Burr arch-truss model on May 21, 2015. Both focus on the moment of failure, when the model was loaded to the maximum load of 68.8 kips.
- Video of the load-testing experiment (.wmv, 129 MB). Right-click the link and save it to your computer. The file opens in Windows Media Player.
- Photo sequence of the rupture (pdf, 4.7 MB). This photo sequence can be viewed like a "flip book" when opened in Adobe Acrobat or Adobe Reader, outside of a web browser.