In mechanics, an abutment is a fixed point or surface from which resistance or reaction is obtained, such as the cylinder head of a steam engine, the fulcrum of a lever, etc. Research Abutment
A bridge, a structure of stone, brick, wood, iron or other material, affording a passage over a stream, valley, or the like. The earliest bridges were probably the trunks of trees. The simplest form of bridge is known as a clapper-bridge and consists of planks or slabs of stone which rest on piles of stones.
The arch seems to have been unknown amongst most of the nations of antiquity. Even the Greeks had not sufficient acquaintance with it to apply it to bridge building. The Romans were the first to employ the principle of the arch in this direction, and after the construction of such a work as the great arched sewer at Rome, the Cloaca Maxima, a bridge over the Tiber would be of comparatively easy execution. One of the finest examples of the Roman bridge was the bridge built by Augustus over the Nera at Narni, the vestiges of which still remain.
It consisted of four arches, the longest of 43 meters span. The most celebrated bridges of ancient Rome were not generally, however, distinguished by the extraordinary size of their arches, nor by the lightness of their piers, but by their excellence and durability. The span of their arches seldom exceeded 20 or 25 meters, and they were mostly semicircular, or nearly so.
The Romans built bridges wherever their conquests extended, and in Britain there are still a number of bridges dating from Roman times. One of the most ancient post-Roman bridges in England is the Gothictriangular bridge at Croyland, in Lincolnshire, said to have been built in 860, having three archways meeting in a common centre at their apex, and three roadways. The longest old bridge in England was that over the Trent at Burton, in Staffordshire, built in the twelfth century, of squared freestone, and pulled down in the 19th century. It consisted of thirty-six arches, and was 47 meters long.
Old London Bridge was commenced in 1176, and finished in 1209. It had houses on each side like a regular street until 1756-58. In 1831 it was altogether removed, the new bridge, which had been begun in 1824, having then been finished.
The art of bridge-building made no progress after the destruction of the Roman empire until the eighteenth century, when the French architects began to introduce improvements, and the constructions of Perronet (Nogent-sur-Seine; Neuilly; Louis XVI bridge at Paris) are masterpieces. Some of the stone bridges built in later times far surpass those of older times in width of span.
Stone bridges consist of an arch or series of arches, and in building them the properties of the arch, the nature of the materials, and many other matters have to be carefully considered. It has been found that in the construction of an arch the slipping of the stones upon one another is prevented by their mutual pressure and the friction of their surfaces; the use of cement is thus subordinate to the principle of construction in contributing to the strength and maintenance of the fabric. The masonry or rock which receives the lateral thrust of an arch is called the abutment, the perpendicular supports are the piers. The width of an arch is its span; the greatest span in any stone bridge is about 75 meters. A one-span bridge has, of course, no piers.
In constructing a bridge across a deep stream it is desirable to have the smallest possible number of points of support. Piers in the waterway are not only expensive to form, but obstruct the navigation of the river, and by the very extent of resisting surface they expose the structure to shocks and the wearing action of the water. In building an arch, a timber framework was used called the centre, or centering. The centering had to keep the stones or voussoirs in position until they were keyed in, that is, all fixed in their places by the insertion of the key-stone.
The first iron bridges were erected from about 1777 to 1790. The same general principles apply to the construction of iron as of stone bridges, but the greater cohesion and adaptability of the material give more liberty to the architect, and much greater width of span is possible. At first iron bridges were erected in the form of arches, and the material employed was cast-iron; but the arch has been generally superseded by the beam or girder, with its numerous modifications; and wrought-iron or steel was likewise found to be much better adapted for resisting a great tensile strain than cast-metal.
Numerous modifications exist of the beam or girder, as the lattice-girder, bow-string-girder, etc; but of these none is more interesting than the tubular or hollow-girder, first rendered famous from its employment by Robert Stephenson in the construction of the railway bridge across the Menai Strait, and connecting Anglesey with the mainland of North Wales. This is known as the Britannia Tubular Bridge. The tubes are of a rectangular form, and constructed of riveted plates of wrought-iron, with rows of rectangular tubes or cells for the floor and roof respectively. The bridge consists of two of these enormous tubes or hollow beams laid side by side, one for the up and the other for the down traffic of the railway, and extending each to about a quarter of a mile in length.
Other tubular bridges of interest are the Conway Bridge, over the river Conway, an erection identical in principle with the Britannia Bridge, but on a smaller scale; the Brotherton Bridge over the river Aire; the tubular railway bridge across the Damietta branch of the Nile, which has this peculiarity, that the roadway is carried above instead of through the tubes. The Victoria Bridge over the St Lawrence at Montreal, originally tubular, is no longer so, the upper portion having been reconstructed with an open track. It is nearly two miles in length, or about five and a half times as long as the bridge across the Menai Strait. A girderrailway bridge across the Firth of Tay at Dundee was opened in 1887, being the second built at the same place, after the first had given way in a great storm. It is 2 miles 73 yards long, has 85 spans, is 77 feet. high, and carries two lines of rails. The bridge over the Firth of Forth at Queensferry, was completed in 1889, and was the largest bridge built on the cantilever principle and was the first very notable example.
A cantilever is a structure the main feature of which is a projecting arm jutting out over the space to be spanned and supporting the roadway; and two cantilevers may be made to meet directly, or the space between may be bridged over by a girder connected with both. The cantilever principle has the advantage that it may be employed where there might be great difficulties in the way of a bridge otherwise constructed, since the projecting arm may be built out from either side of the river or other opening to be crossed, and at a great height if necessary. In some cases a bridge with an arch or arches of wrought iron or steel is preferred chiefly or solely because such a structure has a more handsome appearance than some other bridges.
American engineers have been very successful as builders of iron bridges, adopting various forms of girder, and constructing also some splendid bridges, with arches of great span, built up of wrought iron and steel.
Suspension-bridges, being entirely independent of central supports, do not interfere with the river, and may be erected where it is impracticable to build bridges of any other kind. The entire weight of a suspension-bridge rests upon the piers at either end, from which it is suspended, all the weight being below the points of support. Such bridges always swing a little, giving a vibratory movement which imparts a peculiar sensation to the passenger. The modes of constructing these bridges are various. The roadway is suspended either from chains or from wire-ropes, the ends of which require to be anchored, that is attached to the solid rock or masses of masonry or iron. One of the earlier of the great suspension-bridges is that constructed by Telford over the Menai Strait near the Britannia Tubular Bridge, finished in 1825. The cable-stayed bridge is a type of suspension bridge in which the supporting cables are connected directly to the bridge deck without the use of suspenders.
Though the oldest bridges on record were built of wood, like the Sublician Bridge at Rome, or that thrown by Caesar across the Rhine, it is only in certain places and for certain purposes that wood was much used after 1800. In the 19th century Germany was the school for wooden bridges. Perhaps the most celebrated of all wooden bridges was that which spanned the Rhine at Schaffhausen in Switzerland. This was 364 feet in length and 18 feet broad. It was designed and executed by Ulric Grttbenman, a village carpenter, in 1758, and was destroyed by the French in 1799. In the United States, where timber was still in common use in the 19th century, the Trenton Bridge over the Delaware, erected in 1804; the bridge over the Susquehannah, etc were examples of wooden bridges.
Trestle Bridges, or bridges the roadway of which is supported on wooden trestles or frames, formed of a series of beams and braces and often built up to a great height, were common in America until recently. Certain kinds of bridges are known as movable bridges. The bascule, balance, counterpoise or drawbridge - in which the roadway may be raised and lowered in one or two pieces, - is a common form; and there are also swing bridges (also known as pivot bridges) - opening horizontally to let shipping pass; bridges constructed so as to roll horizontally on wheels or otherwise; bridges in which the movable part, carrying the traffic, is suspended from a high iron framework or cables, under which shipping passes; these forming transporter bridges, as the bridge across the Mersey between Runcorn and Widnes, etc.
Pontoon or floating bridges are formed of pontoons or boats over which the roadway is laid, there being often the means of making an opening for shipping. A flying bridge is simply a kind of ferry. The Tower Bridge, London, crossing the Thames, is a unique structure, a combined suspension and bascule bridge, opening in the centre to admit ships, and originally having an elevated footway for passengers, with lifts and stairs in two towers.
The Bailey bridge is a temporary bridge made of prefabricated steel parts that can be rapidly assembled. It is named after its inventor, the Englishman Sir Donald Bailey who designed the Bailey bridge during the early-mid 20th century.
In architecture, the reins of a vault are the parts between the crown and the spring or abutment, including, and having special reference to, the loading or filling behind the shell of the vault. The reins are to a vault nearly what the haunches are to an arch, and when a vault gives way by thrusting outward, it is because its reins are not sufficiently filled up. Research Reins of a Vault
In architecture a springer is the impost, or point at which an arch rests upon its support, and from which it seems to spring. Hence the term describes the bottom stone of an arch, which lies on the impost. The skew back is one form of springer. The term is also used to describe the rib of a groined vault, as being the solid abutment for each section of vaulting. Research Springer
Tower Bridge is a famous bridge over the River Thames near the Tower Of London in London, England. The bridge was proposed to assist with the severe congestion of traffic crossing the Thames during the 18th century, with typical delays of several hours being experienced by pedestrians and vehicles alike. The debate and designs for a bridge had been going on since 1800 until 1884 when a solution was finally found by Sir Horace Jones and John Wolfe Barry and others.
Tower Bridge was begun on April the 22nd 1886, and opened on the 30th of June 1894 by the Prince and Princess of Wales. Tower Bridge carries a roadway 49 feet in width, with a central lifting or bascule span of 200 feet and two side spans each of 270 feet. The two river piers are 70 feet wide; and the total length, in addition to approach viaducts is 880 feet. The main towers, rising over 120 feet from the river piers, consist of steel columns encased in masonry. The abutmenttowers are 44 feet in height. The side spans are hung from suspension girder-links between the pier and the abutmenttowers, the links at the shore ends being anchored in massed concrete.
Between the suspension links the ties are carried on two overhead foot bridges between the tops of the towers - these foot bridges being later shut to the public. The centre or bascule span consists of two cantilever arms which meet in the centre, where they are locked by massive bolts, being hinged upon shafts inside the piers, where they are heavily weighted to counterbalance the weight of the projecting portions. Their inner ends are fitted with toothed quadrants engaged by gearing and operated by hydraulic machinery. To raise the bridge the centre locking bolts are drawn, the quadrants depressed, and the two leaves rise simultaneously to a vertical position against the towers, allowing 140 feet between high-water level and the foot bridge, reached if necessary by lifts and staircases in the central towers. The average time taken by the raising and lowering of the central span was five minutes when the bridge was new. When closed the central span is 29 feet and 6 inches above the high-water mark.
The gothicarchitecture used to encase the steel infrastructure in the bridge was designed to blend the bridge with the existing Tower Of London, which it does very successfully, Tower Bridge having proved a tourist attraction since construction work started. Research Tower Bridge
In architecture a water wing is one of the two walls built on either side of the junction of a bridge with the bank of a river, to protect the abutment of the bridge and the bank from the action of the current. Research Water Wing
The Probert Encyclopaedia was designed, edited and programed by
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Abbreviations
Research Abutment
