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) 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 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 capita ...
as "the most recognizable city in the country" because of its Y-shaped bridge, and the pilots of ''
Enola Gay'' aimed for
Hiroshima's T-shaped
Aioi Bridge
The is an unusual "T"-shaped three-way bridge in Hiroshima, Japan. The original bridge, constructed in 1932, was the aiming point {{Unreferenced, date=April 2007
In field artillery, the accuracy of indirect fire depends on the use of aiming po ...
when they dropped the atom bomb.
While designing the Tripartite Bridge in 1846—a Y-bridge proposed to span the
Allegheny River 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-cen ...
in
Pittsburgh
Pittsburgh ( ) is a city in the Commonwealth of Pennsylvania, United States, and the county seat of Allegheny County. It is the most populous city in both Allegheny County and Western Pennsylvania, the second-most populous city in Pennsylva ...
, Pennsylvania—engineer
John A. Roebling
John Augustus Roebling (born Johann August Röbling; June 12, 1806 – July 22, 1869) was a German-born American civil engineer. He designed and built wire rope suspension bridges, in particular the Brooklyn Bridge, which has been designated as ...
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