1.
Drawbridge
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A drawbridge or draw-bridge is a type of movable bridge typically associated with the entrance of a castle and a number of towers, surrounded by a moat. Medieval castles were usually defended by a ditch or moat, crossed by 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. 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 is normally found. The raising chains could themselves be attached to counterweights, in some cases, a portcullis provides the weight, as at Alnwick. In France, working drawbridges survive at a number of châteaux, 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 is called a turning bridge, 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 an arrangement, and many turning bridges were replaced with more advanced drawbridges. Bascule bridge Drawbridge mentality Portcullis Linkspan
2.
Plate girder bridge
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A plate girder bridge is a bridge supported by two or more plate girders. In some cases, the plate girders may be formed in a Z-shape rather than I-shape, the first tubular wrought iron plate girder bridge was built in 1846-47 by James Millholland for the Baltimore and Ohio Railroad. Plate girder bridges are suitable for short to medium spans and may support railroads, highways, plate girders are usually prefabricated and the length limit is frequently set by the mode of transportation used to move the girder from the bridge shop to the bridge site. Generally, the depth of the girder is no less than 1/15 the span, and for a load bearing capacity. Stresses on the flanges near the centre of the span are greater than near the end of the span, so the top, vertical stiffeners prevent the web plate from buckling under shear stresses. These are typically uniformly spaced along the girder with additional stiffeners over the supports, in the deck-type bridge, a wood, steel or reinforced concrete bridge deck is supported on top of two or more plate girders, and may act compositely with them. In the case of railroad bridges, the railroad ties themselves may form the bridge deck, additional beams may span across between the main girders, for example in the form of bridge known as ladder-deck construction. Also, further elements may be attached to provide cross-bracing and prevent the girders from buckling, in the half-through bridge, the bridge deck is supported between two plate girders, often on top of the bottom flange. The overall bridge then has a U-shape in cross-section, as cross-bracing cannot normally be added, vertical stiffeners on the girders are normally used to prevent buckling. This form of bridge is most often used on railroads as the depth is much less. This allows obstacles to be cleared with less change in height, multispan plate-girder bridges may be an economical way to span gaps longer than can be spanned by a single girder. Piers serve as intermediate abutments between the end Abutments of bridge, separate plate girder bridges span between each pair of abutments in order to allow for expansion joints between the spans. Concrete is commonly used for low piers, while steel trestle work may be used for high bridges
3.
Cantilever bridge
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A cantilever bridge is a bridge built using cantilevers, structures that project horizontally into space, supported on only one end. Engineers in the nineteenth century understood that a bridge that was continuous across multiple supports would distribute the loads among them and this would result in lower stresses in the girder or truss and meant that longer spans could be built. Several nineteenth century engineers patented continuous bridges with hinge points mid-span, the use of a hinge in the multi-span system presented the advantages of a statically determinate system and of a bridge that could handle differential settlement of the foundations. Engineers could more easily calculate the forces and stresses with a hinge in the girder, heinrich Gerber was one of the engineers to obtain a patent for a hinged girder and is recognized as the first to build one. The Hassfurt Bridge over the Main river in Germany with a span of 124 feet was completed in 1867 and is recognized as the first modern cantilever bridge. The High Bridge of Kentucky by C, the Kentucky River Bridge spanned a gorge that was 275 feet deep and took full advantage of the fact that falsework, or temporary support, is not needed for the main span of a cantilever bridge. The most famous early cantilever bridge is the Forth Bridge and this bridge held the record for longest span in the world for seventeen years, until it was surpassed by the Quebec Bridge. Benjamin Baker illustrated the principles of the suspended span cantilever in the photo on the left. The suspended span, where Kaichi Watanabe sits, is seen in the center, the need to resist compression of the lower chord is seen in the use of wooden poles while the tension of the upper chord is shown by the outstretched arms. The action of the foundations as anchors for the cantilever is visible in the placement of the counterweights. A simple cantilever span is formed by two arms extending from opposite sides of an obstacle to be crossed, meeting at the center. In a common variant, the span, the cantilever arms do not meet in the center, instead. The suspended span may be built off-site and lifted into place, thus, in a bridge built on two foundation piers, there are four cantilever arms, two which span the obstacle, and two anchor arms which extend away from the obstacle. Because of the need for strength at the balanced cantilevers supports. The Commodore Barry Bridge is an example of type of cantilever bridge. Steel truss cantilevers support loads by tension of the upper members, commonly, the structure distributes the tension via the anchor arms to the outermost supports, while the compression is carried to the foundations beneath the central towers. Many truss cantilever bridges use pinned joints and are statically determinate with no members carrying mixed loads. Prestressed concrete balanced cantilever bridges are built using segmental construction
4.
Vertical-lift bridge
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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, generally speaking they cost less to build for longer moveable spans. The counterweights in a lift are only required to be equal to the weight of the deck. As a result, heavier materials can be used in the deck, although most vertical-lift bridges use towers, each equipped with counterweights, some use hydraulic jacks located below the deck. An example is the 52-foot span bridge at St Paul Avenue in Milwaukee, another design used balance beams to lift the deck, with pivoting bascules located on the top of the lift towers. An example of this kind was built at La Salle in Illinois, the biggest disadvantage to the vertical-lift bridge is the height restriction for vessels passing under it. This is a result of the deck remaining suspended above the passageway, Ryde Bridge – road – Ryde, New South Wales – opened 1935, now permanently lowered Hexham Bridge – road – Hexham, New South Wales – opened 1952. In addition, there are also Bridges 13,17 and 18 on the Welland Recreational Waterway, however, these bridges have not been operational since 1973. Bridges 13 and 18 have had their counterweights removed while the machinery for Bridge 17 has been dismantled, in addition, Bridge 18 no longer possesses its towers, they were removed for ease of maintenance. Burlington Canal Lift Bridge, over the Burlington Canal, Burlington, information is available from Built 1962. Second Narrows Bridge Vancouver, BC over Burrard Inlet, Okanagan Lake Bridge in Kelowna, BC across Okanagan Lake – replaced in 2008. Shippagan Bridge Shippagan, NB over Shippagan Bay, sir Ambrose Shea Bridge, Placentia, NL. Pont Gustave-Flaubert – crossing the Seine at Rouen, this bridge is the highest vertical-lift bridge in Europe. It is 670 m long, with a span of 116 metres, a striking design feature, the two road sections are mounted outside the central towers. The bridge was designed by François Gillard and Aymeric Zublena and opened to traffic on 25 September 2008. It is named after the author Gustave Flaubert who was born in Rouen, the central lift span is 117m long and can be lifted vertically up to 53m to let tall ships pass underneath. The bridge is 575m long with the lift span weighing around 2,600 tonnes. Its width varies from 32 to 45m and it will be used by cars, trams, cyclists and it can handle 43,000 vehicles a day and will reduce traffic congestion in Bordeaux
5.
Swing bridge
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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 bridge carrying a road or railway over a river or canal, for example. When a water vessel needs to pass the bridge, road traffic is stopped, as this type requires no counterweights, the complete weight is significantly reduced as compared to other moveable bridges. Where sufficient channel is available to have individual traffic directions on each side, the central support is often mounted upon a berm along the axis of the watercourse, intended to protect the bridge from watercraft collisions when it is opened. This artificial island forms an excellent construction area for building the movable span as the construction will not impede channel traffic, for a symmetrical bridge, the central pier forms a hazard to navigation. Asymmetrical bridges may place the pivot near one side of the channel, where a wide channel is not available, a large portion of the bridge may be over an area that would be easily spanned by other means. A wide channel will be reduced by the pivot and foundation. If struck from the water near the edge of the span, buna River Bridge, in Shkodra, Albania. Puente de la Mujer, an asymmetrical cable-stayed span, the Sale Swing Bridge, Sale, Victoria, Australia. Dunalley Bridge, Dunalley, Tasmania Still in use, Belize City Swing Bridge, Belize City, Belize. Oldest such bridge in Central America and one of the few manually operated swing bridge in world still in operation, the longest swing bridge span is 340 metres, by the El Ferdan Railway Bridge across the Suez Canal. Le pont tournant rue Dieu, across the Canal Saint-Martin in Paris, is a location in the 1938 film Hôtel du Nord. Kalpaka Tilts, Liepāja, connecting the city with the former Russian/Soviet port Karosta, the Abtsewoudsebrug in Delft, close to the Technische Universiteit Delft, is a bridge of this type. 52°0′5. 71″N 4°21′50. 10″E Theres another one on the channel between Ghent and Terneuzen at Sas Van Gent, many inner cities have swing bridges, since these require less street space than other types of bridges. Kopu Bridge, Waihou River, near Thames, New Zealand A swing bridge at the Gatun Locks provides the only road passage over the Atlantic side of the Panama Canal and this is a small bridge that swings out from each side. Another larger swing bridge at the Miraflores Locks is on the Pacific side but is used, having been supplanted by the Bridge of the Americas. Crosskeys Bridge - carries the A17 road over the River Nene in Lincolnshire Folkestone Harbour railway station - railway bridge on the branch line, goole railway swing bridge Glasson Dock swing bridge Hawarden Railway Bridge - rail. Many are manually operated, carrying only farm tracks, but a significant number carry road traffic and are mechanised for boater operation, manchester Ship Canal at Latchford, Stockton Heath and Lower Walton in Warrington, and also slightly further west at Moore
6.
Falsework
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This usage is specifically called centering. The British Standards of practice for falsework, BS5975,1982, until the turn of the 20th century almost all falsework was constructed from timber. To compensate for shortages in different regions and to rationalize labor and material usage. The major developments include the design of devices, transitions to other spanning beams such as steel pipes or profiles or reusable timber beams. During the same period many different scaffolding systems were being developed around the world and these consisted of welded frames that could be slotted or clipped together to form access or support towers. The reduction in time and complexity led to reduced labor costs. Further developments have made scaffolding systems even easier to use, stronger systems have been introduced that either incorporate horizontal restraints at more levels or use stronger tubes or connections. Materials from which falsework systems are manufactured have also diversified from traditional steel, in the UK, BS5975 gives recommendations for the design and use of falsework on construction sites. It was first introduced by the British Standards Institute in March 1982 and was revised in March 1996. The code is currently under revision again, a copy was released in late 2007. Fabrication, Metalworkers fabricate a falsework section from pipe and beams, erection, A section is lifted to a vertical position with the assistance of two forklift operators. Placement, The section is guided into position by a ground crew, completed Falsework, Decking and some formwork has been added. When the supports are complete, wood beams and plywood or reusable metal forms will be placed, reinforcing and tenon conduits added, after curing and any tenon tensioning, wedges will be removed and forms and falsework disassembled. A certain type of bridge, the suspension bridge, must be supported during construction
7.
Moveable bridge
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A moveable bridge, or movable bridge, is a bridge that moves to allow passage for boats or barges. An advantage of making bridges moveable is the lower cost, due to the absence of high piers, the principal disadvantage is that the traffic on the bridge must be halted when it is opened for passages. For seldom-used railroad bridges over busy channels, the bridge may be 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, a few remotely using video-cameras and loudspeakers. Generally, the bridges are powered by motors, whether operating winches, gearing. While moveable bridges in their entirety may be long, the length of the moveable portion is restricted by engineering. There are often traffic lights for the road and water traffic, ninety-nine were killed and 100 were injured. Four crewmen, including the engineer and fireman, and 44 passengers died by drowning, september 22,1993 – Mobile, Alabama, US, In heavy fog and low visibility, a disoriented towboat pilot made a wrong turn and entered an un-navigable waterway. The rails kinked but did not break, so no fault was indicated for approaching trains, approximately 8 minutes later, an Amtrak train carrying 220 passengers derailed at the kinked portion of the rails, killing 47 and injuring 103 more. November 23,1996 – Kearny, New Jersey, US, An Amtrak passenger and mail train derailed crossing the Portal Bridge over the Hackensack River. Moveable Bridges in the British Isles NSW moveable bridges
8.
Weighing scale
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Weighing scales are devices to measure weight or calculate mass. Scales and balances are used in commerce, as many products are sold. Very accurate balances, called analytical balances, are used in fields such as chemistry. Although records dating to the 1700s refer to spring scales for measuring weight, the earliest design for such a device dates to 1770 and credits Richard Salter, an early scale-maker. Postal workers could work quickly with spring scales than balance scales because they could be read instantaneously. By the 1940s various electronic devices were being attached to these designs to make more accurate. A spring scale measures weight by reporting the distance that a spring deflects under a load and this contrasts to a balance, which compares the torque on the arm due to a sample weight to the torque on the arm due to a standard reference weight using a horizontal lever. Spring scales measure force, which is the force of constraint acting on an object. They are usually calibrated so that measured force translates to mass at earths gravity, the object to be weighed can be simply hung from the spring or set on a pivot and bearing platform. In a spring scale, the spring either stretches or compresses, by Hookes law, every spring has a proportionality constant that relates how hard it is pulled to how far it stretches. Rack and pinion mechanisms are used to convert the linear spring motion to a dial reading. With proper manufacturing and setup, however, spring scales can be rated as legal for commerce, to remove the temperature error, a commerce-legal spring scale must either have temperature-compensated springs or be used at a fairly constant temperature. To eliminate the effect of gravity variations, a spring scale must be calibrated where it is used. It is also common in high-capacity applications such as crane scales to use force to sense weight. The test force is applied to a piston or diaphragm and transmitted through hydraulic lines to an indicator based on a Bourdon tube or electronic sensor. A digital bathroom scale is a type of electronic weighing machine, the digital bathroom scale is a smart scale which has many functions like smartphone integration, cloud storage, fitness tracking, etc. In electronic versions of spring scales, the deflection of a beam supporting the weight is measured using a strain gauge. The capacity of such devices is only limited by the resistance of the beam to deflection and these scales are used in the modern bakery, grocery, delicatessen, seafood, meat, produce and other perishable goods departments
9.
Energy
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In physics, energy is the property that must be transferred to an object in order to perform work on – or to heat – the object, and can be converted in form, but not created or destroyed. The SI unit of energy is the joule, which is the transferred to an object by the mechanical work of moving it a distance of 1 metre against a force of 1 newton. Mass and energy are closely related, for example, with a sensitive enough scale, one could measure an increase in mass after heating an object. Living organisms require available energy to stay alive, such as the humans get from food. Civilisation gets the energy it needs from energy resources such as fuels, nuclear fuel. The processes of Earths climate and ecosystem are driven by the radiant energy Earth receives from the sun, the total energy of a system can be subdivided and classified in various ways. It may also be convenient to distinguish gravitational energy, thermal energy, several types of energy, electric energy. Many of these overlap, for instance, thermal energy usually consists partly of kinetic. Some types of energy are a mix of both potential and kinetic energy. An example is energy which is the sum of kinetic. Whenever physical scientists discover that a phenomenon appears to violate the law of energy conservation. Heat and work are special cases in that they are not properties of systems, in general we cannot measure how much heat or work are present in an object, but rather only how much energy is transferred among objects in certain ways during the occurrence of a given process. Heat and work are measured as positive or negative depending on which side of the transfer we view them from, the distinctions between different kinds of energy is not always clear-cut. In contrast to the definition, energeia was a qualitative philosophical concept, broad enough to include ideas such as happiness. The modern analog of this property, kinetic energy, differs from vis viva only by a factor of two, in 1807, Thomas Young was possibly the first to use the term energy instead of vis viva, in its modern sense. Gustave-Gaspard Coriolis described kinetic energy in 1829 in its modern sense, the law of conservation of energy was also first postulated in the early 19th century, and applies to any isolated system. It was argued for years whether heat was a physical substance, dubbed the caloric, or merely a physical quantity. In 1845 James Prescott Joule discovered the link between mechanical work and the generation of heat and these developments led to the theory of conservation of energy, formalized largely by William Thomson as the field of thermodynamics
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