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HAER Surveys

HAER has surveyed 96 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

Photograph of West Union Bridge entrance. The text painted on the bridge reads: "1876, J.J. Daniels, West Union. Cross this bridge at a walk."

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:

Detail of measured drawing: Gilpin's Falls Bridge's Burr-Arch truss


Detail of measured drawing: Contoocook Railroad Bridge's Town truss


Detail of measured drawing: Eldean Bridge's Long truss


Detail of measured drawing: Pine Bluff Bridge's Howe truss


Detail of measured drawing: Morgan Bridge's Queenpost truss

Other truss types:


Detail of measured drawing: Sulphite Railroad Bridge's deck

Additional studies:



Recently Completed HAER Engineering Studies

Moose Brook Bridge (HAER NH-48)

Photograph of Moose Brook Bridge

Significance: The Moose Brook Bridge is one of six boxed pony truss bridges remaining in North America. This former rail line contributed to the economic development of Coos County and the growth of tourism in the White Mountains.

Authors: Lola Bennett (history), 2009; Dario Gasparini and Kamil Nizamiev (engineering), 2018; Timothy Andrews (reconstruction); Vern Mesler (brazing); Christopher H. Marston (editor), 2019.

Project Information: Christopher H. Marston, HAER Architect, served as project leader from 2009-19. The 2009 HAER field team consisted of Anne E. Kidd, field supervisor; Jeremy T. Mauro and Bradley M. Rowley, architects; and Csaba Bartha, ICOMOS intern (Romania); Lola Bennett, historian; and Jet Lowe, photographer. The National Society for the Preservation of Covered Bridges (NSPCB, David Wright, president until he died in 2014) offered the bridge for the research project. Timothy Andrews of Barns and Bridges of New England (BBofNE) disassembled the bridge in 2010, and reconstructed the trusses in 2011-2012, assisted by Will Truax. Vern Mesler led the braze welding repair of the castings at Lansing Community College in 2011. Dario Gasparini led the engineering research on the trusses at Case Western Reserve University, from 2011-2014, assisted by staff Kamil Nizamiev, Neil Harner, Jim Berilla, Michael Butler, and David Conger; and students Vincent Marvin, Lin Wan, and Janette Siu. In 2013, HAER completed laser scanning of the trusses, with a field team consisting of Jeremy T. Mauro, field supervisor; Pavel Gorokhov, Ben Shakelton, and Hummam Salih, architects. Under a Phase II agreement with the NSPCB (William Caswell, president since 2014), Timothy Andrews reassembled the trusses at the Wiscasset, Waterville and Farmington Railway Museum (WW&F; David J. Buczkowski, president) in 2017-18.

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, 11 MB).


Covered Bridge Educational Models (HAER MD-190)

Photograph of educational models

Significance: Scale models of heavy wooden trusses are an important part of the engineering history of covered wooden bridges. At one time, they offered the primary means for a builder to provide evidence of constructability and performance prior to a bridge’s construction. Today, they provide educators the opportunity to bring the rich history of covered wooden bridges into the classroom.

Author: Rachel H. Sangree, 2017.

Project Information: The Covered Bridge Education Models research project was facilitated through Cooperative Agreement No. P15AC00330 between NPS and Johns Hopkins University (JHU). Rachel H. Sangree directed the research and wrote the engineering report. JHU students included Claudio Malicdem, Omer Kama, Jordan Britton, Joshua Weirich, Samantha Wright, Mark Strapko, and Carter Harwood.

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, 18 MB).


Strength of Burr-Arch Trusses

Photograph of Burr Arch truss model

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.