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Image courtesy of Stefan Kuhn, wikimedia commons.
TYPES OF BRIDGES
Man's first attempts at building bridges were constructions generally made from wood as trees were plentiful and wood was easy to cut and lighter to transport.
However Britain's supposed oldest bridge, shown above, is actually a stone bridge and is reported to be around one thousand years old. The Grade I Listed Tarr Steps Bridge, pictured above, located on the River Barle in Exmoor National Park in Somerset consists of seventeen stone spans which cover a distance of fifty five meters.
Since those early days bridges have gone on to be constructed from five general styles of design, they are the arch bridge, the beam bridge, the cable stayed bridge, the cantilever bridge and the truss bridge.
Shown below is an example of each of these bridge types followed by a selection of variations on these styles, followed by a list of the largest bridges in the British Isles.
The Arch Bridge
Image courtesy of Dave Curry, wikimedia commons.
The idea of the arch bridge is to transfer the weight of the bridge outwards towards either side by way of it's curved structure or arch onto it's supporting pillar known as an abutment. An arch bridge can be constructed from one single arch or a series of many arches connected to each other by the abutments.
The arch bridge pictured above is the Silver Jubilee Bridge over the Manchester Ship Canal which links the Merseyside town of Runcorn with the Cheshire town of Widnes.
The through arch bridge, to give it it’s correct technical title, was designed by London based civil engineering company, Mot, Hay & Anderson. The eighty seven meter high bridge was originally opened in 1961, but later widened in 1977, which is how it received it’s new name of Silver Jubilee.
The Beam Bridge
Image courtesy of Lis Burke, wikimedia commons.
The beam bridge, also known as a girder bridge, is the most simple of the bridge designs and the design that has been around for the longest. Basically the beam or girder bridge is constructed by way of two or more support pillars which hold up a beam or girder on which the deck - the path, the road or railtrack - is situated on.To make the bridge longer it just requires more support pillars in order to take more beams or girders.
Our classic example of a beam bridge is the Friarton Bridge which spans the River Tay in Perthshire, Scotland. The one hundred and seventy four meter long bridge was constructed by Canadian construction company, The Miller Group, and engineered by Andrew Stevenson.
The bridge, which is officially known as a segmental beam bridge, carries part of the M90 motorway between Edinburgh and Perth and was opened in 1978.
The Cable Stayed Bridge
Image courtesy of Bencherlite, wikimedia commons.
The cable stay or suspension bridge are of similar design to one another and are constructed by using cables hung from pillars at either end of the bridge, and it is by way of these cables that the main deck is held aloft. The idea is to form tension in the cable by way of compression from the pillars.The cables are generally made up of multiple steel wires or forged or cast chain links.
This type of bridge is ideal in areas of high wind or unstable ground as the cables allow a certain amount of movement to the structure, enabling it to move ever so slightly at times of high wind or in high risk, earth movement areas.
The above bridge is the Menai Suspension Bridge which spans the Menai Straits between the Welsh Mainland and the Isle of Anglesey. The bridge was designed by civil engineer, Thomas Telford, and consists of one wrought iron arch situated on five stone pillars. The bridge is four hundred and seventeen meters long and thirty meters high and was opened in 1826.
The Cantilever Bridge
Image courtesy of |George Gastin, wikimedia commons.
A cantilever is a projecting beam that is supported at one end and which carries a load at the other end. A cantilevered bridge is formed by two cantilevers being placed next to one another in order for one to counterbalance the other, which are connected by a support pillar. The support pillar is anchored onto a pier at it's base which is buried into the bedrock below.
The most famous of this type of bridge is the Forth Rail Bridge in Scotland, which consists of three double truss cantilevers.
This rail bridge, that spans the Firth of Forth waterway between Scotland's capital Edinburgh and the town of Fife, is the second longest cantilever bridge in the world and was considered an engineering masterpiece when it was constructed at the end of the nineteenth century.
Opened in 1890 the bridge is one point five miles long and has a span of five hundred and twenty one meters and carries a traffic load of two hundred trains a day.The bridge was designed by Glasgow civil engineering company, William Arrol & Co.
VARIATIONS OF BRIDGES
The above four types of bridge have been modified to form several other styles of bridges, built in order to perform certain procedures. This has led to the construction of the the aqueduct, the viaduct, the bascule bridge, the swing bridge, the tilt bridge, the truss bridge and the transporter bridge.
Shown below are a sample of these other types of bridges which can be found around the British Isles.
The Aqueduct
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An aqueduct is a bridge built to carry water, generally in the form of a canal. These bridges became popular during the height of the industrial revolution in order to accommodate the country’s vast canal system, which at the time was the country’s main form of infrastructure.
Aqueducts tended to be built over some type of land obstacle, such as a gorge, a valley or a ravine, rather than over water, although that does not mean to say that there are no over water aqueducts.
Our example of an aqueduct is the Grade II Listed, UNESCO World Heritage Site of Pontcysyllte Aqueduct, which carries the Llangollen Canal over the River Dee between the town of Llangollen and the village of Frontcysyllte in North Wales.
The cast iron and brick built aqueduct was designed by civil engineer Thomas Telford and has eighteen spans and four piers. The bridge, which was opened in 1805, is three hundred and seven meters long and thirty eight meters high, making it both the longest and the tallest aqueduct in the British Isles.
The Bascule Bridge
Image courtesy of C.M.Glee, wikimedia commons.
The bascule or draw bridge is generally formed from a beam or girder bridge that has been given a deck that can be pulled up to allow water traffic to pass under it. These types of bridges are generally constructed above areas of tidal water where the water level rises and falls quite considerably with the daily tides. The most famous of this type of bridge is Tower Bridge in London.
Tower Bridge is both a bascule bridge and a suspension bridge that spans the River Thames between the borough of Tower Hamlets and the city of London on the north of the river and Bermondsey in the Borough of Southwark on the south side of the river..
The bridge was built between 1886 and 1894 to acommodate two lanes for vehicular traffic and two pedestrian walkways .
It's draw bridge section, which is positioned over the middle of the river, is sixty meters long and allows the passage of tall vessels to pass beneath it with a clearance of eight point six meters at high tide. When closed, and due to it's eighty three degree raise, it can reach a clearance of forty two point five meters when open.
The two stone supporting towers on either side of the draw bridge hold it's fifty six meter long suspension platforms - known as piers - and the cables that take the other two sections of the bridge further onto the shore are further supported by another twelve meter high tower . The taller towers are sixty four point nine meters high and the hydraulic motors housed inside them can lift the draw bridge, as seen in the above image, in less than five minutes.
The bridge was designed by Glasgow civil engineering company, William Arrol & Co.
The Swing Bridge
Image courtesy of Tagishsimon, wikimedia commons.
A swing bridge is a bridge that has been constructed in order to be swung away from the river when ships need to pass at high tide.The swing bridge pictured above is the hydraulic powered Newcastle / Gateshead Swing Bridge which spans the River Tyne in Newcastle which was opened in 1876.
This eighty five point six meter wide bridge was designed by local industrialist and civil engineer William Armstrong in order to transport goods to his factory further up river. He had the hydraulic accumulator sunk eighteen meters below the bridge where water would be released under pressure in order to run the three oscillating hydraulic motors which turn the bridge.
The bridge is still run today by way of Armstrong's original machinery.
The Tilt Bridge
The tilt bridge is a modern design on the swing bridge, again constructed in order to allow ships to pass beneath it at high tide.The bridge’s two vast arches tilt into an upright position when ships need to pass below it.
Britain’s most famous tilt bridge is the Gateshead Millenium Bridge built over the River Tyne between Newcastle Quayside and Gateshead Quays. The bridge is a pedestrian foot bridge which is one hundred and twenty six meters wide and was opened in 2001.
The bridge’s designers were London based architects, Wilkinson Eyre, who were awarded with the Stirling RIBA Prize for their design of the bridge in 2000. The above image shows the bridge at tilt.
The Transporter Bridge
Image courtesy of Huw, wikimedia commons.
A transporter bridge, also known as a gondola bridge, is a beam or girder bridge that has a load bearing car or gondola suspended from the underside of the main beam or girder in order to carry passengers.There are only six working types of transporter bridge in the world, two of which are located in the UK.
The Middlesborough Transporter Bridge, shown above, stands two hundred and fifty nine meters above the River Tees and links the town of Middlesborough with Port Clarence. The bridge was opened in 1911 and designed by Glasgow civil engineering company William Arrol & Co.
The Newport Transporter Bridge carries passengers over the River Usk in Newport, South Wales. This Grade I Listed bridge was designed by French engineer Ferdinand Arnodin and was opened in 1906.
It’s twin towers are seventy four meters high, making it the tallest of the world's six transporter bridges, and the gondolas, shown above, are electric powered.
The Truss Bridge
Image courtesy of Roantrum, wikimedia commons.
The truss bridge is a variation of any type of design where the load bearing superstructure has been constructed with triangular or diamond shaped units to form a truss. The nature of the truss bridge allows for the application of Newton’s Law of Motion, according to the branch of physics known as statics.
There are around thirty different types of truss bridge design, the most famous examples of which are the trusses of the cantilevers on the Forth Rail Bridge and the under arch trusses of the world’s first Iron Bridge at Shropshire.
This first cast Iron arch, truss bridge was designed by foundry owner, Abraham Darby III and is situated over the River Severn at what is now known as Iron Bridge Gorge in Coalbrookdale, Shropshire.
The bridge was constructed between 1775 and 1779, but was not opened until 1781.The bridge was at first a toll bridge which carried all types of traffic over the gorge, but is today only for the use of foot passengers. The bridge has a water clearance of eighteen meters and is sixty meters long.
The Viaduct
A viaduct is a bridge which is constructed in order to carry some type of transport network, such as a road, a motorway or a railway track. Most viaducts tended to be built over some type of land obstruction, such as a gorge, valley or ravine rather than over water, although that does not mean to say that there are no over water viaducts.
Our example of a viaduct is the six hundred and ninety meter high, Yarm Viaduct, near Stockton on Tees in Yorkshire.This viaduct, which carries the Leeds to Thirsk railway between the villages of Yarm and Eaglescliffe, was designed by Scottish civil engineers Thomas Grainger and John Bourne and was opened in 1851.
The viaduct consists of forty three arches, forty one of which were built of brick and the two which span the River Tees were built from stone.
BRITAIN'S LARGEST BRIDGES
The British Isles' longest rail bridge is the Tay Rail Bridge which spans the River Tay in Scotland between the city of Dundee and the small town of Wormit.
This 2.75 mile long segmented truss bridge consists of eighty five spans and was built to replace a former bridge which once stood in the same place which collapsed during heavy winds in December 1879. There was a train traversing the bridge at the time of it's collapse which resulted in the deaths of everyone on board, around seventy five people.
This second bridge was designed by William Barlow and built by Glasgow civil engineering company William Arrol & Co and was opened just eight years later in 1887.
Image courtesy of Mattbuck, wikimedia commons
The longest road bridge in the British Isles is the 3.1 mile long Severn Second Crossing situated between Sudbrook in Monmouthshire, South Wales and Severn Beach in Gloucestershire, England.
The bridge was constructed in three sections with a twenty five span segmented beam bridge on the English side and a twenty four span segmented beam bridge on the Welsh side both of which are linked by way of a four hundred and fifty six meter long cable stayed bridge in the centre. This central span is officially known as Shoot's Bridge.
The bridge, which was opened in 1996, stands 137 meters high at it's highest point and carries the M4 Motorway across the vast River Severn estuary.
The bridge is unusual for charging a one way toll, with tolls levied to enter Wales but not to enter England.
The tallest bridge in the British Isles is the 155.5 meter high Humber Road Bridge, which was opened in 1981.
This toll bridge, which links the Lincolnshire town of Barton on Humber with the Yorkshire town of Hessle, carries the A15 road across the vast expanse of the River Humber Estuary in north east England.
Due to it's height the 2.22 mile long, single span suspension bridge enforces a 50 mile per hour speed limit.
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