Brass

Brass is a versatile manufacturing material because of its hardness and workability. The longest spans usually require suspension bridges. A dezincified fitting has the pink appearance of pure copper and will easily crumble, being reduced to a weak sponge-like matrix. For medium spans, trusses or box beams are usually most economical, while in some cases, the appearance of the bridge may be more important than its cost efficiency. In some territories, plumbing fittings designed to resist dezincification are embossed "CR" (corrosion resistant). Bridges employing only compression are relatively inefficient structurally, but may be highly cost efficient where suitable materials are available near the site. In some environments, brasses with higher content of zinc are prone to a selective leaching corrosion known as dezincification. For a given site, kind of bridge employed and the materials used determine the total cost, a lifetime cost composed of materials, labor, machinery, engineering, cost of money, maintenance, refurbishment, risk potential, and ultimately, demolition and associated disposal, recycling, and reuse.

The malleablity and acoustic properties of brass have made it the metal of choice for brass musical instruments such as the tuba. A bridge's economic efficiency will be site and traffic dependent, the ratio of savings by having a bridge (instead of, for example, a ferry, or a longer road route) compared to its cost. . A more refined measure for this exercise is to weigh the completed bridge rather than measure against a fixed quantity of materials provided, a test that emphasizes economy of materials and efficient glue joints. Pure zinc, on the other hand, is too reactive to be produced by ancient metalworking techniques. The bridge taking the greatest load is by this test the most structurally efficient. During this process, the zinc is extracted from the calamine and instantly mixes with the copper. In one common challenge young students are to be divided into groups of two or three and then to be given a fixed quantity of wood sticks, a specific distance to span, and a given glue, and then to construct a bridge that will be tested to destruction by the progressive addition of load at the center of the span.

It was produced by melting copper together with calamine, a zinc ore. A bridge's structural efficiency may be considered to be the ratio of load carried to bridge weight, given a specific set of material types. Brass has been known to man since prehistoric times, long before zinc itself was discovered. Bridges can also be classified by their lineage, which is shown as the vertical axis on the diagram to the right. Because of this, and its relative resistance to tarnishing, it is often used as a decoration. In other cases the forces may be distributed among a large number of members, as in a truss, or not clearly discernible to a casual observer as in a box beam. Brass has a yellow colour, somewhat similar to gold. The separation of forces may be quite clear, as in a suspension or cable-stayed span; the elements in tension are distinct in shape and placement.

. Most bridges will employ all of the principle forces to some degree, but only a few will predominate. Despite this distinction, some types of brasses are called bronzes. Bridges may be classified by how the four forces of tension, compression, bending and shear are distributed through their structure. Typically it is more than 50% copper and from 5 to 20% zinc^[1], in comparison to bronze which is principally an alloy of copper and tin.^[2]. The central bridge was reserved exclusively for the use of the Emperor, Empress, and their attendants. Brass is the term used for alloys of copper and zinc in a solid solution. A set of five bridges cross a sinuous waterway in an important courtyard of the Forbidden City in Beijing, China.

Yellow brass is an American term for 33% zinc brass. 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. White brass contains more than 50 % zinc and is too brittle for general use. Other garden bridges may cross only a dry bed of stream washed pebbles, intended only to convey an impression of a stream. Red brass is an American term for CuZnSn alloy known as gunmetal. This type, often found in east-asian style gardens, is called a Moon bridge, evoking a rising full moon. Naval brass, similar to admiralty brass, is a 40% zinc brass and 1% tin. To create a beautiful image, some bridges are built much taller than necessary.

Low brass is a copper-zinc alloy containing 20% zinc with a light golden color, excellent ductility and is used for flexible metal hoses and metal bellows. An aqueduct is a bridge that carries water, resembling a viaduct. It has excellent machinability. For example, it may be a bridge carrying a highway and forbidden for pedestrians and bicycles, or a pedestrian bridge, possibly also for bicycles. Leaded brass is an alpha-beta brass with addition of lead. In some cases there may be restrictions in use. High brass, contains 65% copper and 35% zinc, has a high tensile strength and is used for springs, screws, rivets. A bridge is usually designed for trains, pedestrian or road traffic, a pipeline or waterway for water transport or barge traffic.

Common brass, or rivet brass, is a 37% zinc brass, cheap and standard for cold working. There are four main types of bridges: beam bridges, cantilever bridges, arch bridges and suspension bridges. Cartridge brass is a 30% zinc brass with good cold working properties. The Oxford English Dictionary traces the origin of the word bridge to an Old Norse word bryggja, meaning "landing stage, gangway, or movable pier". Beta brasses, with 45-50 % zinc content, can only be worked hot, is harder, stronger, and suitable for casting. With the advent of steel, which has a high tensile strength, much larger bridges were built, many using the ideas of Gustave Eiffel. Arsenical brass contains an addition of arsenic and frequently aluminium and is used for boiler fireboxes. With the rise of the Industrial Revolution in the 19th century, truss systems of wrought iron were developed for larger bridges, but iron did not have the tensile strength to support large loads.

Aluminium brass contains aluminium, which improves its corrosion resistance. The first engineering book on building bridges was written by Hubert Gautier in 1716. Alpha-beta brasses are usually worked hot. During the 18th century there were many innovations in the design of timber bridges by Hans Ulrich, Johannes Grubenmann, and others. It contains both α and β' phase; the β'-phase is body-centered cubic and is harder and stronger than α. Rope bridges, a simple type of suspension bridge, were used by the Inca civilization in the Andes mountains of South America, just prior to European colonization in the 1500s. Alpha-beta brass (Muntz metal), also called duplex brass, is 35-45 % zinc and is suited for hot working. Brick and mortar bridges were built after the Roman era, as the technology for cement was lost then later rediscovered.

They contain only one phase, with face-centered cubic crystal structure. The Romans also had cement, which reduced the variation of strength found in natural stone. Alpha brasses (Prince's metal), with less than 35% zinc, are malleable, can be worked cold, and are used in pressing, forging, or similar. The arch was first used by the Roman Empire for bridges and aqueducts, some of which still stand today. Admiralty brass contains 30% zinc and 1% tin which inhibits dezincification. The first bridges were spans made of wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement. .

The purpose of a bridge is to allow easier passage by providing a continuous more uniform more easily navigable route via what would otherwise be an uneven or impossible path for the particular kind of thing travelling or being transported, whether people, vehicles, trains, ships, liquids or whatever else. Designs may be built higher than otherwise needed in order to allow other traffic (particularly ship traffic) beneath. A bridge is a structure built to span a gorge, valley, road, railroad track, river, body of water, or any other physical obstacle. Pearl Harbor Memorial Bridge - USA, will be the first extradosed cable-stayed bridge constructed in the United States.

Zakim Bunker Hill Bridge - USA, built during Boston's Big Dig, the widest cable-stayed bridge. Victoria Falls Bridge - linking Zimbabwe to Zambia, built in 1905 as part of the projected Cape-Cairo railway. Vasco da Gama Bridge - Portugal, the longest bridge in Europe at 17.2 km. Trajan's bridge - Romania, ancient Roman bridge over the river Danube, only fragments visible.

Tyne Bridge - England, one of Northern England's most iconic structures. Tsing Ma Bridge - Hong Kong, the world's longest rail & road suspension bridge. Tower Bridge - London, England, and a symbol of this city. Tatara Bridge - Japan, largest span cable-stayed bridge.

Tacoma Narrows Bridge - USA, famous for its collapse due to aerodynamic effects. Sydney Harbour Bridge - Australia, arguably the best-known suspended-deck compression arch bridge. Sundial Bridge - USA, a dramatic single cantilever spar cable stayed span for pedestrians. San Francisco-Oakland Bay Bridge - USA, especially for seismic retrofit and eastern span replacement.

Québec Bridge - Canada, largest cantilever bridge in the world. Penang Bridge - Malaysia, longest bridge in Southeast Asia. Palace Bridge - St Petersburg, Russia, one of iconic images of the city. Overtoun Bridge, - Scotland, dogs have leaped to their deaths from this bridge, leading to urban legends.

Øresundbroen/Öresundsbron. Millau Viaduct - France, tallest bridge in the world. Menai Suspension Bridge - Wales, first road suspension bridge in the world. Mahatma Gandhi Setu - India, the longest river bridge in the world.

Mackinac Bridge - USA, Opened to traffic in 1957, connecting the two peninsulas of Michigan; held the title of the world's longest two tower suspension bridge between anchorages until the 1990s. Lupu Bridge- China, longest single steel arch. Lake Pontchartrain Causeway - USA, spanning Lake Pontchartrain in south Louisiana, it is the longest bridge in the world at 23.87 miles (38.41 km). Jamuna Bridge- Bangladesh, longest rail-road bridge in south asia , 2nd longest in world.

Confederation Bridge - Canada, world's longest bridge over waters that freeze. The Iron Bridge - England, the world's first iron bridge. Golden Gate Bridge - USA, arguably the most beautiful of its type. Forth Railway Bridge - Scotland, one of the most famous cantilever bridges in the world.

Akashi-Kaikyo Bridge - Japan, with the longest section span of 1.9 km.