Penobscot Narrows Bridge (2007)
Bridges may be classified by several factors: span, travel, form, and material. Five basic forms are arch, beam, cable-stayed, suspension, and truss. Of course, each form may serve several uses, including road vehicles, railroads, and pedestrians. Here are some examples in Maine.
Bridge Forms
The brief discussion of the basic forms below only begins to fully describe their elements and the many variations possible with combined forms. See references below for more resources. Also search “bridges” and “covered bridges” for articles referencing bridges.
Cable-Stayed-Bridges
The Penobscot Narrows bridge spans the the Penobscot River between Prospect and Verona Island. It replaced the Waldo-Hancock bridge (at left in left photo; in background in center photo).
Penobscot Narrows Bridge ’12
Penobscot Narrows Bridge ’12
Suspension Bridges-Roads
The old Waldo-Hancock bridge is one example. Another is the Deer-Isle bridge across Eggemoggin Reach in Hancock County. Finally, the “Wire Bridge” in New Portland.
Waldo-Hancock Bridge (c. 1936)
Waldo-Hancock Bridge (2001)
Deer Isle Bridge (2001)
Deer Isle Bridge (2003)
New Portland over the Carrabassett (2001)
New Portland over the Carrabassett River (2001)
Suspension Bridges-Pedestrians
Waterville–Winslow and Skowhegan span the Kennebec River. The Androscoggin River flows under the Brunswick–Topsham bridge.
Waterville-Winslow (2001)
Skowhegan (2002)
Brunswick-Topsham (2002)
Truss-Bridges
This form relies on triangle-based supports of rigid materials, such as iron, steel, and wood. They include (in order below) single spans, draw, pedestrian, multi-span, wooden covered, and vertical-lift bridges. See the Kennebec Bridge.
1916 Bridge over the Sandy River in New Sharon (2003)
Former Draw Bridge in Thomaston (2005)
Buxton-Hollis Pedestrian Bridge over a Saco River dam (2003)
1929 Bridge on the Penobscot River in Howland (2005)
Sunday River Bridge in Newry (2007)
Old Carleton Bridge over the Kennebec River (2007)
Arch-Bridges
An arch bridge gets it’s support from the arch, not from trusses and beams.
1928 Norridgewock-Skowhegan bridge (2001)
Kittery-Portsmouth Bridge from Eliot (2001)
The Arrowsic Bridge from the Kennebec River (2003)
Pedestrian Bridge in Houlton (2012)
Bridge over Canal in Lewiston (2001)
Somes Sound, Mt. Desert ’01
Beam-Bridges
Also known as girder bridges, the simple form consists of a single beam on a vertical support at each end. A more complex version is a cantilever design, with beams anchored at one end so that they need no support at the other end. Two such beams may meet in the middle to create the span, with no vertical support in the middle.
Bridge over the Songo River in Casco (2003)
Van Buren–St. Leonard International (2003)
Over Wesserunsett Stream, Skowhegan (2003)
Forest Bridge in Silver Ridge TWP (2003)
Walking bridge near Baxter Park from Abol Bridge (2004)
Additional resources
American Institute of Architects — Cincinnati. “Five Bridge Types.” http://www.aiacincinnati.org/community/ABC/curriculum/FiveBridgeTypes.pdf (accessed March 31, 2013)
(Gale, Nellie Isabella. Some Ferries and Covered Bridges of Maine. Orono, Me. University of Maine. 1932. [Maine State Library]
“Historic Bridges of Maine:Maine Overview.” http://historicbridges.org/map_me.php (accessed July 12, 2014)
Jakeman, Adelbert M. Old Covered Bridges of Maine. Ocean Park, Me. Published at Sea Have. 1980.
Maine Covered Bridges: a collection of photographs. State Highway Commission; accompanied by an article on covered bridges from Maine Library Bulletin, April 1932; assembled 1939. [Maine State Library]
Maine Department of Transportation. “Historic Bridges in the State of Maine.” http://www.maine.gov/mdot/historicbridges/index.htm (accessed March 31, 2013)
Maine Department of Transportation. “BRIDGES AND BRIDGE COMPONENTS DEFINITIONS AND TYPES.” http://www.maine.gov/mdot/martinspointbridgedb/documents/pdf/bridgetypes9-21-10.pdf. (accessed March 31, 2013)
Old Covered Bridges of Maine, 1932-1933. Collected by Cora Parsons Watson. [Maine State Library]