A multi-way bridge is a
bridge with three or more distinct and separate spans, where one end of each span meets at a common point near the centre of the bridge. Unlike other bridges which have two entry-exit points, multi-way bridges have three or more entry-exit points. For this reason, multi-way bridges are not to be confused with commonly found road bridges which carry vehicles in one direction from one entry point, and then bifurcate into two other one-way bridges.
Description
Multi-way bridges are located throughout the world, though they are rare. Some are as small as a
footbridge, while others are multi-lane roadways.
Three-way bridges are often referred to as "T-bridges" or "Y-bridges", due to their shape when viewed from above. Three cities in
Michigan each have a three-way bridge named "Tridge", combining "tri" and "bridge":
,
The Tridge (Ypsilanti, Michigan)
Ypsilanti (), commonly shortened to Ypsi, is a city in Washtenaw County, Michigan, Washtenaw County in the U.S. state of Michigan.
As of the 2020 United States census, 2020 census, the city's population was 20,648. The city is bounded to the n ...
and The Tridge in
Brighton, Michigan.
The unique shape of a multi-way bridge makes it easy to identify from an airplane. Pilot
Amelia Earhart
Amelia Mary Earhart ( , born July 24, 1897; disappeared July 2, 1937; declared dead January 5, 1939) was an American aviation pioneer and writer. Earhart was the first female aviator to fly solo across the Atlantic Ocean. She set many oth ...
described
Zanesville, Ohio as "the most recognizable city in the country" because of its Y-shaped bridge, and the pilots of ''
Enola Gay
The ''Enola Gay'' () is a Boeing B-29 Superfortress bomber, named after Enola Gay Tibbets, the mother of the pilot, Colonel Paul Tibbets. On 6 August 1945, piloted by Tibbets and Robert A. Lewis during the final stages of World War II, it be ...
'' aimed for
Hiroshima's T-shaped
Aioi Bridge when they dropped the atom bomb.
While designing the Tripartite Bridge in 1846—a Y-bridge proposed to span the
Allegheny River
The Allegheny River ( ) is a long headwater stream of the Ohio River in western Pennsylvania and New York (state), New York. The Allegheny River runs from its headwaters just below the middle of Pennsylvania's northern border northwesterly into ...
and
Monongahela River in
Pittsburgh, Pennsylvania—engineer
John A. Roebling identified one of the challenges of erecting a three-way
suspension-type bridge. Suspension-bridge cables on two-way bridges support heavy loads and are anchored solidly at either end,
while on a three-way bridge the cables of each of the three spans need to anchor at a central pier in the water, where cable forces from each span would have to balance each another: "the intersection of the cables at the top of the center pier...would have created enormous horizontal forces, and the stone arches connecting the three towers could hardly have resisted the tensions imposed by the cables radiating from their tops."
The bridge was never built.
Three-way bridges
Four-way bridges
Five-way bridge
References
{{Bridge footer