|Ancestor||Trestle bridge, Box girder bridge|
|Carries||Expressways, highways, streets, railways|
|Span range||Short (multiple)|
|Material||reinforced concrete, prestressed concrete, masonry|
|Falsework required||available for use, since viaducts are all composed of low bridges.|
A viaduct is a specific type of bridge that consists of a series of arches, piers or columns supporting a long elevated railway or road. Typically a viaduct connects two points of roughly equal elevation, allowing direct overpass across a wide valley, road, river, or other low-lying terrain features and obstacles.The term viaduct is derived from the Latin via meaning "road", and ducere meaning "to lead". It is a 19th century derivation from an analogy with ancient Roman aqueducts. Like the Roman aqueducts, many early viaducts comprised a series of arches of roughly equal length.
The longest in antiquity may have been the Pont Serme which crossed wide marshes in southern France.At its longest point, it measured 2,679 meters with a width of 22 meters.
Viaducts are commonly used in many cities that are railroad hubs, such as Chicago, Atlanta, Birmingham, London and Manchester. These viaducts cross the large railroad yards that are needed for freight trains there, and also cross the multi-track railroad lines that are needed for heavy rail traffic. These viaducts provide grade separation and keep highway and city street traffic from having to be continually interrupted by the train traffic. Likewise, some viaducts carry railroads over large valleys, or they carry railroads over cities with many cross-streets and avenues.
Many viaducts over land connect points of similar height in a landscape, usually by bridging a river valley or other eroded opening in an otherwise flat area. Often such valleys had roads descending either side (with a small bridge over the river, where necessary) that become inadequate for the traffic load, necessitating a viaduct for "through" traffic.Such bridges also lend themselves for use by rail traffic, which requires straighter and flatter routes. Some viaducts have more than one deck, such that one deck has vehicular traffic and another deck carries rail traffic. One example of this is the Prince Edward Viaduct in Toronto, Canada, that carries motor traffic on the top deck as Bloor Street, and metro as the Bloor-Danforth subway line on the lower deck, over the steep Don River valley. Others were built to span settled areas, crossing over roads beneath—the reason for many viaducts in London.
Viaducts over water make use of islands or successive arches. They are often combined with other types of bridges or tunnels to cross navigable waters as viaduct sections, while less expensive to design and build than tunnels or bridges with larger spans, typically lack sufficient horizontal and vertical clearance for large ships. See the Chesapeake Bay Bridge-Tunnel.
The Millau Viaduct is a cable-stayed road-bridge that spans the valley of the river Tarn near Millau in southern France. It opened in 2004 and is the tallest vehicular bridge in the world, with one pier's summit at 343 metres (1,125 ft). The viaduct Danyang–Kunshan Grand Bridge in China was the longest bridge in the world as of 2011 [update] .
Where a viaduct is built across land rather than water, the space below the arches may be used for businesses such as car parking, vehicle repairs, light industry, bars and nightclubs. In the United Kingdom, many railway lines in urban areas have been constructed on viaducts, and so the infrastructure owner Network Rail has an extensive property portfolio in arches under viaducts.In Berlin the space under the arches of elevated subway lines is used for several different purposes, including small eateries or bars.
Elevated expressways were built in major cities such as Boston (Central Artery), Los Angeles, San Francisco, Seoul, Tokyo and Toronto (Gardiner Expressway). [ citation needed ] In other cases, viaducts were demolished because they were structurally unsafe, such as the Embarcadero Freeway in San Francisco, which was damaged following an earthquake in 1989. However, in developing nations such as Thailand, India (Delhi-Gurgaon Expressway), China, Bangladesh, Pakistan, Nicaragua elevated expressways have been built and more are under construction to improve traffic flow, particularly as a workaround of land shortage when built atop surface roads.[ citation needed ]Some were demolished because they were unappealing and divided the city.
In Indonesia viaducts are used for railways in Java and also for highways such as the Jakarta Inner Ring Road. The Coulée verte René-Dumont in Paris, France is a disused viaduct which was converted to an urban park in 1993. In January 2019 the Alaskan Way Viaduct in Seattle was closed and replaced with a tunnel after several decades of use due to being seismically unsafe.[ citation needed ]
A bridge is a structure built to span a physical obstacle without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually something that is otherwise difficult or impossible to cross. There are many different designs of bridges, each serving a particular purpose and applicable to different situations. Designs of bridges vary depending on factors such as: the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, and the material used to make it and the funds available to build it.
The Frederick G. Gardiner Expressway, commonly known as the Gardiner Expressway or simply the Gardiner, is a municipal expressway in Toronto, Ontario, Canada. Running close to the shore of Lake Ontario, it extends from the foot of the Don Valley Parkway (DVP) in the east, just past the mouth of the Don River, to the junction of Highway 427 and the Queen Elizabeth Way (QEW) in the west, for a total length of 18.0 kilometres (11.2 mi). East of Dufferin Street to just east of the Don River, the roadway is elevated for a length of 6.8 kilometres (4.2 mi), unofficially making it the longest bridge in Ontario. It runs above Lake Shore Boulevard east of Spadina Avenue.
A bridge to nowhere is a bridge where one or both ends are broken, incomplete, or unconnected to any roads. If it is an overpass or an interchange, the term overpass to nowhere or interchange to nowhere may be used respectively. There are five main origins for these bridges:
The Don Valley Parkway (DVP) is a municipal expressway in Toronto, Ontario, Canada which connects the Gardiner Expressway in downtown Toronto with Highway 401. North of Highway 401, it continues as Highway 404. The parkway runs through the parklands of the Don River Valley, after which it is named. It has a maximum speed limit of 90 km/h (56 mph) for its entire length of 15.0 km (9.3 mi). It is six lanes for most of its length but it is eight lanes north of York Mills and four lanes south of Eastern. As a municipal road, it is patrolled by the Toronto Police Service.
The Prince Edward Viaduct System, commonly referred to as the Bloor Viaduct, is the name of a truss arch bridge system in Toronto, Ontario, Canada, connecting Bloor Street East, on the west side of the system, with Danforth Avenue on the east. The system includes the Rosedale Valley phase and the Sherbourne Phase, an embankment built to extend Bloor Street East to the Rosedale Ravine from Sherbourne Street. The Don Valley phase of the system, the most recognizable, spans the Don River Valley, crossing over the Bayview Avenue Extension, the Don River, and the Don Valley Parkway.
The Millau Viaduct is a multi-span cable-stayed bridge completed in 2004 across the gorge valley of the Tarn near Millau in Southern France. The design team was led by engineer Michel Virlogeux and English architect Norman Foster. As of September 2020, it is the tallest bridge in the world, having a structural height of 336.4 metres (1,104 ft).
A trestle bridge is a bridge composed of a number of short spans supported by closely spaced frames. A trestle is a rigid frame used as a support, historically a tripod used both as stools and to support tables at banquets. Each supporting frame is a bent. A trestle differs from a viaduct in that viaducts have towers that support much longer spans and typically have a higher elevation.
The Silver Jubilee Bridge crosses the River Mersey and the Manchester Ship Canal at Runcorn Gap between Runcorn and Widnes in Halton, England. It is a through arch bridge with a main arch span of 361 yards. It was opened in 1961 as a replacement for the Widnes-Runcorn Transporter Bridge. In 1975–77 the carriageway was widened, after which the bridge was given its official name in honour of the Queen's Silver Jubilee. It carries the A533 road and a cantilevered footway. The bridge is recorded in the National Heritage List for England as a designated Grade II listed building. The bridge was closed to vehicles for refurbishment upon the opening of the new Mersey Gateway Bridge, but reopened as a toll bridge in February 2021.
The Boston University Bridge, originally the Cottage Farm Bridge and commonly referred to as the BU Bridge, is a steel truss through arch bridge with a suspended deck carrying Route 2 over the Charles River, connecting the Boston University campus to Cambridge, Massachusetts. According to the American Association of State Highway and Transportation Officials route log, the bridge also carries U.S. Route 3 across the river to its southern terminus at U.S. Route 20. However, the Massachusetts Department of Transportation does not consider the bridge to be a part of US 3; it continues the route along Memorial Drive in Cambridge until it meets Route 2A at the end of the Harvard Bridge.
The Atlantic Branch is an electrified rail line owned and operated by the Long Island Rail Road in the U.S. state of New York. It is the only LIRR line that runs in the borough of Brooklyn.
The Old Eastern Avenue Bridge consists of two bridges spanning the Don River in Toronto, Ontario, Canada. The north bridge or Gas Line Bridge is a concrete arch bridge built for Consumer's Gas Company and is used by Enbridge Gas to carry a major gas main. The southern Howe truss bridge, similar to Queen Street Viaduct and Sir Isaac Brock Bridge, previously carried traffic on Eastern Avenue but is currently unused.
The Old Main Line Subdivision is a railroad line owned and operated by CSX Transportation in the U.S. state of Maryland. The line runs from Relay west to Point of Rocks, and was once the main line of the Baltimore and Ohio Railroad, one of the oldest rail lines in the United States. At its east end, it has junctions with the Capital Subdivision and the Baltimore Terminal Subdivision; its west end has a junction with the Metropolitan Subdivision.
Canton Viaduct is a blind arcade cavity wall railroad viaduct in Canton, Massachusetts, built in 1834–35 for the Boston and Providence Railroad (B&P).
The West Philadelphia Elevated, also known as the High Line or Philadelphia High Line, is a railroad viaduct in the western part of Philadelphia, Pennsylvania. The 8,140-foot (2,480 m) structure spans the railway lines of 30th Street Station, parallel to the main track of the station, in a north-south direction. The 1,045-foot (319 m) long approach made of brick arches is the longest brick bridge and probably even the longest brick building in the United States.
Bergen Hill refers to the lower Hudson Palisades in New Jersey, United States, where they emerge on Bergen Neck, which in turn is the peninsula between the Hackensack and Hudson Rivers, and their bays. In Hudson County, it reaches a height of 260 feet.
The 178th and 179th Street Tunnels are two disused vehicular tunnels in Upper Manhattan in New York City. Originally conceived and constructed under the auspices of Robert Moses, the twin tunnels have been superseded by the Trans-Manhattan Expressway in Washington Heights, which itself runs through a cut with high-rise apartments built over it in places.
The Rosedale Valley Bridge is a covered arch bridge in the northeast of Downtown Toronto, Ontario. Built in 1966 by architect John B. Parkin, the concrete bridge carries Line 2 trains of the subway across the Rosedale Ravine.