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Drawbridge
A drawbridge or draw-bridge is a type of moveable bridge typically at the entrance to a castle or tower surrounded by a moat. In some forms of English, including American English, the word ''drawbridge'' commonly refers to all types of moveable bridges, such as bascule bridges, vertical-lift bridges and swing bridges, but this article concerns the narrower historical definition of the term where the bridge is used in a defensive structure. 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. Castle drawbridges Medieval castles were usually defended by 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 ed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drawbridge
A drawbridge or draw-bridge is a type of moveable bridge typically at the entrance to a castle or tower surrounded by a moat. In some forms of English, including American English, the word ''drawbridge'' commonly refers to all types of moveable bridges, such as bascule bridges, vertical-lift bridges and swing bridges, but this article concerns the narrower historical definition of the term where the bridge is used in a defensive structure. 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. Castle drawbridges Medieval castles were usually defended by 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 ed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drawbridge Mentality
A drawbridge mentality is the attitude of people who have migrated to a more exclusive or more "unspoiled" community and then campaign to preserve the tranquility of that community by opposing further inward migration by people or businesses and, possibly, any development or refurbishment, including plans put forward by those already located there. The term can imply a selfish attitude and can be taken as an insult by people who have strong affection for their home locality and wish to protect it from any changes. It is closely related to the NIMBY attitude. There are many factors that can lead to a person developing a drawbridge mentality, and two of the factors are quality of place and migration. When new people migrate into an already populated area, they often bring with them new ideas and practices. Sometimes, the original population is upset with this change and wants to keep things how they were. These individuals “reject change and work to preserve the status quo, adopting a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moveable Bridge
A moveable bridge, or movable bridge, is a bridge that moves to allow passage for boats or barges. In American English, the term is synonymous with , and the latter is the common term, but drawbridge can be limited to the narrower, historical definition used in some other forms of English, in which ''drawbridge'' refers to only a specific type of moveable bridge often found in castles . An advantage of making bridges moveable is the lower cost, due to the absence of high piers and long approaches. The principal disadvantage is that the traffic on the bridge must be halted when it is opened for passage of traffic on the waterway. For seldom-used railroad bridges over busy channels, the bridge may be left open and then closed for train passages. For small bridges, bridge movement may be enabled without the need for an engine. Some bridges are operated by the users, especially those with a boat, others by a bridgeman (or bridge tender); a few are remotely controlled using video-cam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bascule Bridge
A bascule bridge (also referred to as a drawbridge or a lifting bridge) is a moveable bridge with a counterweight that continuously balances a span, or leaf, throughout its upward swing to provide clearance for boat traffic. It may be single- or double-leafed. The name comes from the French term for balance scale, which employs the same principle. Bascule bridges are the most common type of movable span because they open quickly and require relatively little energy to operate, while providing the possibility for unlimited vertical clearance for marine traffic. History Bascule bridges have been in use since ancient times, but until the adoption of steam power in the 1850s, very long, heavy spans could not be moved quickly enough for practical application. Types There are three types of bascule bridge and the counterweights to the span may be located above or below the bridge deck. The fixed-trunnion (sometimes a "Chicago" bascule) rotates around a large axle that raises the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bascule Bridge
A bascule bridge (also referred to as a drawbridge or a lifting bridge) is a moveable bridge with a counterweight that continuously balances a span, or leaf, throughout its upward swing to provide clearance for boat traffic. It may be single- or double-leafed. The name comes from the French term for balance scale, which employs the same principle. Bascule bridges are the most common type of movable span because they open quickly and require relatively little energy to operate, while providing the possibility for unlimited vertical clearance for marine traffic. History Bascule bridges have been in use since ancient times, but until the adoption of steam power in the 1850s, very long, heavy spans could not be moved quickly enough for practical application. Types There are three types of bascule bridge and the counterweights to the span may be located above or below the bridge deck. The fixed-trunnion (sometimes a "Chicago" bascule) rotates around a large axle that raises the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linkspan
A linkspan or link-span is a type of drawbridge used mainly in the operation of moving vehicles on and off a roll-on/roll-off (RO-RO) vessel or ferry, particularly to allow for tidal changes in water level. Linkspans are usually found at ferry terminals where a vessel uses a combination of ramps either at the stern, bow or side to load or unload cars, vans, trucks and buses onto the shore, or alternately at the stern and/or the bow to load or unload railroad cars. History The first linkspans appeared at the end of the 19th century when train ferries came into operation. Each rail ferry berth has to be specifically designed to make sure that it fitted one class of ship. In most of these vessels it was also possible to carry some road vehicles. By the mid 20th century with the rise of road transport, general purpose Ro Ro ferries started to come into service. Most could use the rail ferry berths but generally they were fitted with stern ramps that had the dual function of gi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Portcullis
A portcullis (from Old French ''porte coleice'', "sliding gate") is a heavy vertically-closing gate typically found in medieval fortifications, consisting of a latticed grille made of wood, metal, or a combination of the two, which slides down grooves inset within each jamb of the gateway. Usage Portcullises fortified the entrances to many medieval castles, securely closing off the castle during time of attack or siege. Every portcullis was mounted in vertical grooves in the walls of the castle and could be raised or lowered quickly by means of chains or ropes attached to an internal winch. Portcullises had an advantage over gates in that they could be closed immediately at a time of crisis by a single guard. Often, two portcullises to the main entrance would be used. The one closer to the inside would be closed first, and then the one farther away. This was used to trap the enemy, and often, burning wood or fire-heated sand would be dropped onto them from the roof or murder-h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertical-lift Bridge
A vertical-lift bridge or just lift bridge is a type of movable bridge in which a span rises vertically while remaining parallel with the deck. The vertical lift offers several benefits over other movable bridges such as the bascule and swing-span bridges. Generally speaking, they cost less to build for longer moveable spans. The counterweights in a vertical lift are only required to be equal to the weight of the deck, whereas bascule bridge counterweights must weigh several times as much as the span being lifted. As a result, heavier materials can be used in the deck, and so this type of bridge is especially suited for heavy railroad use. The biggest disadvantage to the vertical-lift bridge (in comparison with many other designs) is the height restriction for vessels passing under it, due to the deck remaining suspended above the passageway. Although most vertical-lift bridges use towers, each equipped with counterweights, some use hydraulic jacks located below the deck. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swing Bridge
A swing bridge (or swing span bridge) is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its center of gravity, about which the swing span (turning span) can then pivot horizontally as shown in the animated illustration to the right. Small swing bridges as found over canals may be pivoted only at one end, opening as would a gate, but require substantial underground structure to support the pivot. In its closed position, a swing bridge carrying a road or railway over a river or canal, for example, allows traffic to cross. When a water vessel needs to pass the bridge, road traffic is stopped (usually by traffic signals and barriers), and then motors rotate the bridge horizontally about its pivot point. The typical swing bridge will rotate approximately 90 degrees, or one-quarter turn; however, a bridge which intersects the navigation channel at an oblique angle may be built to rotate only 45 degrees, or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moat
A moat is a deep, broad ditch, either dry or filled with water, that is dug and surrounds a castle, fortification, building or town, historically to provide it with a preliminary line of defence. In some places moats evolved into more extensive water defences, including natural or artificial lakes, dams and sluices. In older fortifications, such as hillforts, they are usually referred to simply as ditches, although the function is similar. In later periods, moats or water defences may be largely ornamental. They could also act as a sewer. Historical use Ancient Some of the earliest evidence of moats has been uncovered around ancient Egyptian castles. One example is at Buhen, a castle excavated in Nubia. Other evidence of ancient moats is found in the ruins of Babylon, and in reliefs from ancient Egypt, Assyria, and other cultures in the region. Evidence of early moats around settlements has been discovered in many archaeological sites throughout Southeast Asia, including ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Portcullis
A portcullis (from Old French ''porte coleice'', "sliding gate") is a heavy vertically-closing gate typically found in medieval fortifications, consisting of a latticed grille made of wood, metal, or a combination of the two, which slides down grooves inset within each jamb of the gateway. Usage Portcullises fortified the entrances to many medieval castles, securely closing off the castle during time of attack or siege. Every portcullis was mounted in vertical grooves in the walls of the castle and could be raised or lowered quickly by means of chains or ropes attached to an internal winch. Portcullises had an advantage over gates in that they could be closed immediately at a time of crisis by a single guard. Often, two portcullises to the main entrance would be used. The one closer to the inside would be closed first, and then the one farther away. This was used to trap the enemy, and often, burning wood or fire-heated sand would be dropped onto them from the roof or murder-h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Castle
A castle is a type of fortified structure built during the Middle Ages predominantly by the nobility or royalty and by military orders. Scholars debate the scope of the word ''castle'', but usually consider it to be the private fortified residence of a lord or noble. This is distinct from a palace, which is not fortified; from a fortress, which was not always a residence for royalty or nobility; from a ''pleasance'' which was a walled-in residence for nobility, but not adequately fortified; and from a fortified settlement, which was a public defence – though there are many similarities among these types of construction. Use of the term has varied over time and has also been applied to structures such as hill forts and 19th-20th century homes built to resemble castles. Over the approximately 900 years when genuine castles were built, they took on a great many forms with many different features, although some, such as curtain walls, arrowslits, and portcullises, were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
