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13-636: The Breydon Bridge is a single-span drawbridge carrying the A47 in Great Yarmouth across the River Yare close to Breydon Water . It replaces the former railway Breydon Viaduct which was closed in 1953 and demolished by 1963. Completed in 1985, an average of 31,000 vehicles cross the bridge each day. When built in 1985, the bridge was allocated the road number A12 , which ran from London to Great Yarmouth via Lowestoft and Ipswich / A14 . In February 2017,

26-537: A costly ornamental building with no practical value ". They were criticized because at the time of their completion, the threat from the French navy had passed, largely due to the complete alignment of Napoleon III's foreign policy with British interests then to the withdrawal of France following its crushing by Prussia in the Franco-Prussian war of 1870, and because the technology of the guns had become obsolete. They were

39-425: A ditch or moat , crossed by a wooden bridge. In early castles, the bridge might be designed to be destroyed or removed in the event of an attack, but drawbridges became very common. A typical arrangement would have the drawbridge immediately outside a gatehouse , consisting of a wooden deck with one edge hinged or pivoting at the gatehouse threshold, so that in the raised position the bridge would be flush against

52-772: A group of forts and associated structures around the coasts of the United Kingdom and Ireland . The forts were built during the Victorian period on the recommendations of the 1860 Royal Commission on the Defence of the United Kingdom , prompted by concerns about the strength of the French Navy, and strenuous debate in Parliament about whether the cost could be justified. The name comes from their association with Lord Palmerston , who

65-475: Is called a turning bridge , and may or may not have the raising chains characteristic of a drawbridge. The inner end carried counterweights enabling it to sink into a pit in the gate-passage, and when horizontal the bridge would often be supported by stout pegs inserted through the side walls. This was a clumsy arrangement, and many turning bridges were replaced with more advanced drawbridges. Drawbridges were also used on forts with Palmerston Forts using them in

78-401: Is normally found. The bridge may extend into the gate-passage beyond the pivot point, either over a pit into which the internal portion can swing (providing a further obstacle to attack), or in the form of counterweighted beams that drop into slots in the floor. The raising chains could themselves be attached to counterweights. In some cases, a portcullis provides the weight, as at Alnwick . By

91-675: The A12 was reallocated the number A47 as a Southern extension of the latter road. This left the Breydon Bridge carrying the number A47 which continues to Lowestoft before terminating at the A12 . This article about a bridge in the United Kingdom is a stub . You can help Misplaced Pages by expanding it . Drawbridge As used in castles or defensive structures, drawbridges provide access across defensive structures when lowered, but can quickly be raised from within to deny entry to an enemy force. Medieval castles were usually defended by

104-432: The 14th century, a bascule arrangement was provided by lifting arms (called "gaffs") above and parallel to the bridge deck whose ends were linked by chains to the lifting part of the bridge. In the raised position, the gaffs would fit into slots in the gatehouse wall ("rainures") which can often still be seen in places like Herstmonceux Castle . Inside the castle, the gaffs were extended to bear counterweights, or might form

117-467: The form of Guthrie rolling bridges . Drawbridges have appeared in films as part of castle sets. When the drawbridge needs to be functional this may present engineering challenges since the set may not be able to support the weight of the bridge in the conventional manner. One solution is to build the drawbridge from steel and concrete before hiding the structural materials behind wood and plaster. Palmerston Forts The Palmerston Forts are

130-496: The gate, forming an additional barrier to entry. It would be backed by one or more portcullises and gates. Access to the bridge could be resisted with missiles from machicolations above or arrow slits in flanking towers . The bridge would be raised or lowered using ropes or chains attached to a windlass in a chamber in the gatehouse above the gate-passage. Only a very light bridge could be raised in this way without any form of counterweight, so some form of bascule arrangement

143-511: The most costly and extensive system of fixed defences undertaken in Britain in peacetime. Some sixty years previously, there had been a similar period of defence works construction, when some 140 circular towers were built for the same purpose (mainly along the Sussex, Kent and Suffolk coast to protect London) called Martello Towers , but these had become outdated. The new defences were built to defend

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156-508: The side-timbers of a stout gate which would be against the roof of the gate-passage when the drawbridge was down, but would close against the gate-arch as the bridge was raised. In France, working drawbridges survive at a number of châteaux , including the Château du Plessis-Bourré . In England, two working drawbridges remain in regular use at Helmingham Hall , which dates from the early sixteenth century. A bridge pivoted on central trunnions

169-414: Was Prime Minister at the time and promoted the idea. The works were also known as Palmerston's Follies , partly because the first ones which were around Portsmouth , had their main armament facing inland to protect Portsmouth from a land-based attack, and thus (as it appeared to some) facing the wrong way to defend from a French attack. The name also derived from the use of the term "folly" to indicate "

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