A multi-way bridge is a
bridge
A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...
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
A footbridge (also a pedestrian bridge, pedestrian overpass, or pedestrian overcrossing) is a bridge designed solely for pedestrians.''Oxford English Dictionary'' While the primary meaning for a bridge is a structure which links "two points at a ...
, 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
Michigan () is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the List of U.S. states and ...
each have a three-way bridge named "Tridge", combining "tri" and "bridge":
The Tridge (Midland, Michigan)
The Tridge is the formal name of a three-way wooden footbridge spanning the confluence of the Chippewa and Tittabawassee Rivers in Chippewassee Park near downtown Midland, Michigan, in the Tri-Cities region. Named as a portmanteau of "tri" and ...
,
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
Brighton is a city in the Detroit metropolitan area in southeastern Livingston County, Michigan, United States. As of the 2010 census, the city population was 7,444. Brighton forms part of the South Lyon-Howell-Brighton Urban Area. It is one of ...
.
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; Presumption of death, declared dead January 5, 1939) was an American aviation pioneer and writer. Earhart was the first women in aviation, female aviator to fly solo acro ...
described
Zanesville, Ohio
Zanesville is a city in and the county seat of Muskingum County, Ohio, United States. It is located east of Columbus and had a population of 24,765 as of the 2020 census, down from 25,487 as of the 2010 census. Historically the state capital ...
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. The Allegheny River runs from its headwaters just below the middle of Pennsylvania's northern border northwesterly into New York then i ...
and
Monongahela River
The Monongahela River ( , )—often referred to locally as the Mon ()—is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed August 15, 2011 river on the Allegheny Plateau in north-c ...
in
Pittsburgh
Pittsburgh ( ) is a city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, United States, and the county seat of Allegheny County, Pennsylvania, Allegheny County. It is the most populous city in both Allegheny County and Wester ...
, 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
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