This post is by Colleen Gardina, Engineering Specialist in the Science & Business Reading Room.
You probably knew you could truss a turkey, but did you know about the truss bridge? In the 13th century, French architect, Villard de Honnecourt, sketched one of the first depictions of a truss bridge. Later, an Italian architect, Andrea Palladio, described four designs of truss bridges in his “Treatise On Architecture,” published in 1570. The use of truss bridges spread across Europe during the mid-1700s. By the mid-1800s, in replacing structures destroyed during the Revolutionary war and expanding the transportation infrastructure of the growing nation, the United States led the world in truss bridge construction.
How exactly does a truss bridge work? Truss bridges have a framework made up of trusses – beams made up of three main types of components: vertical, horizontal, and diagonal members, which form triangles. Simply put, these triangles cannot be distorted by stress and can withstand considerable loads. Truss bridges require less material relative to the weight they support.
Originally, truss bridges were constructed of wood and built according to “rule of thumb” methods. This meant that architects designed bridges based on look and feel, rather than using quantifiable data to analyze stresses on the materials. By 1847, though, Squire Whipple, of Utica, NY published, “A Work On Bridge-Building,” where he correctly analyzed stresses on a truss bridge. His works established the science of bridge design.
On January 28, 1820, Ithiel Town of New Haven, CT received a patent for his design of a lattice wooden truss bridge. His patented design minimized building and labor costs. Town’s truss could be, “built by the mile and cut by the yard,” according to Town. One of the most famous examples of the lattice wooden truss was an incarnation of the Tucker Toll Bridge in Bellows Falls, VT, which was constructed in 1840 with a total length of 262 feet.
Town’s design is not the only kind of truss bridge. For example, the Howe Truss, named after designer William Howe, is the first patented truss bridge design to incorporate iron, and the Whipple Truss, named after Squire Whipple, is the first all-iron truss bridge design. During World War II, Sir Donald Coleman Bailey designed the Bailey Bridge to aid the Allies. Invaluable to the war efforts in Italy, and other theaters of war, the Bailey Bridge is a portable, prefabricated truss bridge, light enough to be carried in trucks and built by hand, without the need for special tools.
If you’d like to learn more about the different types of truss bridges, check out this engineering drawing, Trusses: a Study By the Historic American Engineering Record. The next time you cross a bridge, keep an eye out for triangles. It just might be a truss!
If you want to learn more about the history of truss bridges and their design, check out the following books:
Barratt, Claire, and Ian Whitelaw. The Spotter’s Guide to Urban Engineering: Infrastructure and Technology in the Modern Landscape. Richmond Hill, Ont: Firefly Books, 2011.
Bennett, David. The Creation of Bridges: From Vision to Reality, the Ultimate Challenge of Architecture, Design and Distance. Edison, NJ: Chartwell Books, 1999.
Denison, Edward, and Ian Stewart. How to Read Bridges: A Crash Course in Engineering and Architecture. New York: Rizzoli, 2012.
Steinman, David B., and Sara Ruth Watson. Bridges and their Builders. New York, New York: Dover Publications, 1957.
Zettwoch, Dan. Bridges: Engineering Masterpieces. New York, New York: Roaring Brook Press, 2022. (Science Comics series)
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