A BRIDGE is a structure built to span physical obstacles without closing the way underneath such as a body of water , valley , or road , for the purpose of providing passage over the obstacle. There are many different designs that each serve a particular purpose and apply to different situations. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, the material used to make it, and the funds available to build it.
* 1 Etymology * 2 History
* 3 Types of bridges
Oxford English Dictionary
The first bridges made by humans were probably spans of cut wooden
logs or planks and eventually stones, using a simple support and
crossbeam arrangement. A common form of lashing sticks, logs, and
deciduous branches together involved the use of long reeds or other
harvested fibers woven together to form a huge rope capable of binding
and holding together the materials used in early bridges. The
Arkadiko Bridge in
Arkadiko Bridge is one of four Mycenaean corbel arch bridges part
of a former network of roads, designed to accommodate chariots ,
between the fort of Tiryns and town of Epidauros in the
The greatest bridge builders of antiquity were the ancient Romans .
The Romans built arch bridges and aqueducts that could stand in
conditions that would damage or destroy earlier designs. Some stand
today. An example is the
Alcántara Bridge , built over the river
In India, the
Arthashastra treatise by
Kautilya mentions the
construction of dams and bridges. A
Mauryan bridge near
Although large Chinese bridges of wooden construction existed at the
time of the
Warring States , the oldest surviving stone bridge in
During the 18th century there were many innovations in the design of timber bridges by Hans Ulrich Grubenmann , Johannes Grubenmann , and others. The first book on bridge engineering was written by Hubert Gautier in 1716.
A major breakthrough in bridge technology came with the erection of
In 1927 welding pioneer Stefan Bryła designed the first welded road bridge in the world, the Maurzyce Bridge which was later built across the river Słudwia at Maurzyce near Łowicz , Poland in 1929. In 1995, the American Welding Society presented the Historic Welded Structure Award for the bridge to Poland.
TYPES OF BRIDGES
Bridges can be categorized in several different ways. Common categories include the type of structural elements used, by what they carry, whether they are fixed or movable, and by the materials used.
Bridges may be classified by how the forces of tension , compression , bending , torsion and shear are distributed through their structure. Most bridges will employ all of the principal forces to some degree, but only a few will predominate. The separation of forces may be quite clear. In a suspension or cable-stayed span, the elements in tension are distinct in shape and placement. In other cases the forces may be distributed among a large number of members, as in a truss.
BEAM BRIDGE Beam bridges are horizontal beams supported at each end by substructure units and can be either simply supported when the beams only connect across a single span, or continuous when the beams are connected across two or more spans. When there are multiple spans, the intermediate supports are known as piers . The earliest beam bridges were simple logs that sat across streams and similar simple structures. In modern times, beam bridges can range from small, wooden beams to large, steel boxes. The vertical force on the bridge becomes a shear and flexural load on the beam which is transferred down its length to the substructures on either side They are typically made of steel, concrete or wood. Beam bridge spans rarely exceed 250 feet (76 m) long, as the flexural stresses increase proportional to the square of the length (and deflection increases proportional to the 4th power of the length). However, the main span of the Rio-Niteroi Bridge , a box girder bridge, is 300 metres (980 ft).
The world's longest beam bridge is
Lake Pontchartrain Causeway
TRUSS BRIDGE A truss bridge is a bridge whose load-bearing superstructure is composed of a truss. This truss is a structure of connected elements forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges. The basic types of truss bridges shown in this article have simple designs which could be easily analyzed by nineteenth and early twentieth century engineers. A truss bridge is economical to construct owing to its efficient use of materials.
CANTILEVER BRIDGE Cantilever bridges are built using cantilevers —horizontal beams supported on only one end. Most cantilever bridges use a pair of continuous spans that extend from opposite sides of the supporting piers to meet at the center of the obstacle the bridge crosses. Cantilever bridges are constructed using much the same materials "> Arch bridges have abutments at each end. The weight of the bridge is thrust into the abutments at either side. The earliest known arch bridges were built by the Greeks, and include the Arkadiko Bridge .
With the span of 220 metres (720 ft), the
Solkan Bridge over the
Soča River at
Solkan in Slovenia is the second largest stone bridge
in the world and the longest railroad stone bridge. It was completed
in 1905. Its arch, which was constructed from over 5,000 tonnes (4,900
long tons; 5,500 short tons) of stone blocks in just 18 days, is the
second largest stone arch in the world, surpassed only by the
Friedensbrücke (Syratalviadukt) in
Plauen , and the largest railroad
stone arch. The arch of the Friedensbrücke, which was built in the
same year, has the span of 90 m (295 ft) and crosses the valley of the
Syrabach River. The difference between the two is that the Solkan
The world's current largest arch bridge is the Chaotianmen Bridge over the Yangtze River with a length of 1,741 m (5,712 ft) and a span of 552 m (1,811 ft). The bridge was opened April 29, 2009 in Chongqing , China.
TIED ARCH BRIDGE Tied arch bridges have an arch-shaped superstructure, but differ from conventional arch bridges. Instead of transferring the weight of the bridge and traffic loads into thrust forces into the abutments, the ends of the arches are restrained by tension in the bottom chord of the structure. They are also called bowstring arches.
Suspension bridges are suspended from cables. The earliest suspension
bridges were made of ropes or vines covered with pieces of bamboo. In
modern bridges, the cables hang from towers that are attached to
caissons or cofferdams. The caissons or cofferdams are implanted deep
into the bed of the lake, river or sea. Sub-types include the simple
suspension bridge , the stressed ribbon bridge , the underspanned
suspension bridge , the suspended-deck suspension bridge , and the
self-anchored suspension bridge . There is also what is sometimes
called a "semi-suspension" bridge, of which the Ferry
The longest suspension bridge in the world is the 3,909 m (12,825 ft) Akashi Kaikyō Bridge in Japan.
CABLE-STAYED BRIDGE Cable-stayed bridges , like suspension bridges, are held up by cables. However, in a cable-stayed bridge, less cable is required and the towers holding the cables are proportionately higher. The first known cable-stayed bridge was designed in 1784 by C. T. (or C. J.) Löscher.
FIXED OR MOVABLE BRIDGES
Most bridges are fixed bridges, meaning they have no moving parts and stay in one place until they fail or are demolished. Temporary bridges, such as Bailey bridges , are designed to be assembled, and taken apart, transported to a different site, and re-used. They are important in military engineering, and are also used to carry traffic while an old bridge is being rebuilt. Movable bridges are designed to move out of the way of boats or other kinds of traffic, which would otherwise be too tall to fit. These are generally electrically powered.
George Washington Bridge , connecting New York
Bergen County ,
Double-decked (or double-decker) bridges have two levels, such as the
George Washington Bridge , connecting
New York City
Robert Stephenson 's
High Level Bridge
A viaduct is made up of multiple bridges connected into one longer
structure. The longest and some of the highest bridges are viaducts,
such as the
Lake Pontchartrain Causeway
The three-way Tridge Main article: Three-way bridge
A three-way bridge has three separate spans which meet near the
center of the bridge. The bridge appears as a "T" or "Y" when viewed
from above. Three-way bridges are extremely rare. The Tridge ,
Margaret Bridge , and Zanesville Y-
BRIDGE TYPES BY USE
A bridge can be categorized by what it is designed to carry, such as trains, pedestrian or road traffic, a pipeline or waterway for water transport or barge traffic. An aqueduct is a bridge that carries water, resembling a viaduct, which is a bridge that connects points of equal height. A road-rail bridge carries both road and rail traffic. A bridge can carry overhead power lines as does the Storstrøm Bridge .
Some bridges accommodate other purposes, such as the tower of Nový
Bridges are subject to unplanned uses as well. The areas underneath some bridges have become makeshift shelters and homes to homeless people, and the undersides of bridges all around the world are spots of prevalent graffiti. Some bridges attract people attempting suicide , and become known as suicide bridges .
BRIDGE TYPES BY MATERIAL
The Iron Bridge
The materials used to build the structure are also used to categorize bridges. Until the end of the 18th Century, bridges were made out of timber, stone and masonry. Modern bridges are currently built in concrete, steel, fiber reinforced polymers (FRP), stainless steel or combinations of those materials. Living bridges have been constructed of live plants such as tree roots in India and vines in Japan.
BRIDGE TYPE MATERIALS USED
Cantilever For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from structural steel , or box girders built from prestressed concrete .
Suspension The cables are usually made of steel cables galvanised with zinc , along with most of the bridge, but some bridges are still made with steel reinforced concrete .
Beam Beam bridges can use pre-stressed concrete, an inexpensive building material, which is then embedded with rebar . The resulting bridge can resist both compression and tension forces.
Truss The triangular pieces of Truss bridges are manufactured from straight and steel bars, according to the truss bridge designs.
Most bridges are utilitarian in appearance, but in some cases, the appearance of the bridge can have great importance. Often, this is the case with a large bridge that serves as an entrance to a city, or crosses over a main harbor entrance. These are sometimes known as signature bridges. Designers of bridges in parks and along parkways often place more importance to aesthetics, as well. Examples include the stone-faced bridges along the Taconic State Parkway in New York.
To create a beautiful image, some bridges are built much taller than
necessary. This type, often found in east-Asian style gardens, is
Moon bridge , evoking a rising full moon. Other garden
bridges may cross only a dry bed of stream washed pebbles, intended
only to convey an impression of a stream. Often in palaces a bridge
will be built over an artificial waterway as symbolic of a passage to
an important place or state of mind. A set of five bridges cross a
sinuous waterway in an important courtyard of the
Forbidden City in
See also: List of bridge failures
The failure of bridges is of special concern for structural engineers
in trying to learn lessons vital to bridge design, construction and
maintenance. The failure of bridges first assumed national interest
In the United States, the National Bridge Inventory tracks the structural evaluations of all bridges, including designations such as "structurally deficient" and "functionally obsolete".
There are several methods used to monitor the stress on large structures like bridges. The most common method is the use of an accelerometer , which is integrated into the bridge while it is being built. This technology is used for long-term surveillance of the bridge.
Another option for structural-integrity monitoring is "non-contact
monitoring", which uses the
Doppler effect (Doppler shift). A laser
beam from a
Further information: List of bridge types and List of longest bridges in the world
* Bridges portal
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* ^ Fowler (1925). The Concise Oxford Dictionary. Oxford University
Press. p. 102.
* ^ Kutz, Myer (2011). Handbook of Transportation Engineering,
Volume II: Applications and Technologies, Second Edition. McGraw-Hill
Professional. ISBN 978-0-07-161477-1 .
* ^ DeLony, Eric (1996). "Context for World Heritage Bridges".
Icomos.org. Archived from the original on February 21, 2005.
* ^ "History of BRIDGES". Historyworld.net. Retrieved January 4,
* ^ "Lessons from Roman
* Brown, David J. Bridges: Three Thousand Years of Defying Nature. Richmond Hill, Ont: Firefly Books, 2005. ISBN 1-55407-099-6 . * Sandak, Cass R. Bridges. An Easy-read modern wonders book. New York: F. Watts, 1983. ISBN 0-531-04624-9 . * Whitney, Charles S. Bridges of the World: Their Design and Construction. Mineola, NY: Dover Publications, 2003. ISBN 0-486-42995-4 (Unabridged republication of Bridges : a study in their art, science, and evolution. 1929.)