A tower is a tall structure, taller than it is wide, often by a significant factor. Towers are distinguished from masts by their lack of guy-wires and are therefore, along with tall buildings, self-supporting structures.
Towers are specifically distinguished from buildings in that they are built not to be habitable but to serve other functions using the height of the tower. For example, the height of a clock tower improves the visibility of the clock, and the height of a tower in a fortified building such as a castle increases the visibility of the surroundings for defensive purposes. Towers may also be built for observation, leisure, or telecommunication purposes. A tower can stand alone or be supported by adjacent buildings, or it may be a feature on top of a larger structure or building.
Old English torr is from Latin turris via Old French tor. The Latin term together with Greek τύρσις was loaned from a pre-Indo-European Mediterranean language, connected with the Illyrian toponym Βου-δοργίς. With the Lydian toponyms Τύρρα, Τύρσα, it has been connected with the ethnonym Τυρρήνιοι as well as with Tusci (from *Turs-ci), the Greek and Latin names for the Etruscans (Kretschmer Glotta 22, 110ff.)
Towers have been used by mankind since prehistoric times. The oldest known may be the circular stone tower in walls of Neolithic Jericho (8000 BC). Some of the earliest towers were ziggurats, which existed in Sumerian architecture since the 4th millennium BC. The most famous ziggurats include the Sumerian Ziggurat of Ur, built the 3rd millennium BC, and the Etemenanki, one of the most famous examples of Babylonian architecture. The latter was built in Babylon during the 2nd millennium BC and was considered the tallest tower of the ancient world.
Some of the earliest surviving examples are the broch structures in northern Scotland, which are conical towerhouses. These and other examples from Phoenician and Roman cultures emphasised the use of a tower in fortification and sentinel roles. For example, the name of the Moroccan city of Mogador, founded in the first millennium BC, is derived from the Phoenician word for watchtower ('migdol'). The Romans utilised octagonal towersas elements of Diocletian's Palace in Croatia, which monument dates to approximately 300 AD, while the Servian Walls (4th century BC) and the Aurelian Walls (3rd century AD) featured square ones. The Chinese used towers as integrated elements of the Great Wall of China in 210 BC during the Qin Dynasty. Towers were also an important element of castles.
Other well known towers include the Leaning Tower of Pisa in Pisa, Italy built from 1173 until 1372 and the Two Towers in Bologna, Italy built from 1109 until 1119. The Himalayan Towers are stone towers located chiefly in Tibet built approximately 14th to 15th century.
Up to a certain height, a tower can be made with the supporting structure with parallel sides. However, above a certain height, the compressive load of the material is exceeded and the tower will fail. This can be avoided if the tower's support structure tapers up the building.
A second limit is that of buckling—the structure requires sufficient stiffness to avoid breaking under the loads it faces, especially those due to winds. Many very tall towers have their support structures at the periphery of the building, which greatly increases the overall stiffness.
A third limit is dynamic; a tower is subject to varying winds, vortex shedding, seismic disturbances etc. These are often dealt with through a combination of simple strength and stiffness, as well as in some cases tuned mass dampers to damp out movements. Varying or tapering the outer aspect of the tower with height avoids vibrations due to vortex shedding occurring along the entire building simultaneously.
Although not correctly defined as towers, many modern high-rise buildings (in particular skyscraper) have 'tower' in their name or are colloquially called 'towers'. Skyscrapers are more properly classified as 'buildings'. In the United Kingdom, tall domestic buildings are referred to as tower blocks. In the United States, the original World Trade Center had the nickname the Twin Towers, a name shared with the Petronas Twin Towers in Kuala Lumpur. In addition some of the structures listed below do not follow the strict criteria used at List of tallest towers.
The tower throughout history has provided its users with an advantage in surveying defensive positions and obtaining a better view of the surrounding areas, including battlefields. They were constructed on defensive walls, or rolled near a target (see siege tower). Today, strategic-use towers are still used at prisons, military camps, and defensive perimeters.
By using gravity to move objects or substances downward, a tower can be used to store items or liquids like a storage silo or a water tower, or aim an object into the earth such as a drilling tower. Ski-jump ramps use the same idea, and in the absence of a natural mountain slope or hill, can be human-made.
In history, simple towers like lighthouses, bell towers, clock towers, signal towers and minarets were used to communicate information over greater distances. In more recent years, radio masts and cell phone towers facilitate communication by expanding the range of the transmitter. The CN Tower in Toronto, Ontario, Canada was built as a communications tower, with the capability to act as both a transmitter and repeater. Its design also incorporated features to make it a tourist attraction, including the world's highest observation deck at 147 storeys.[ citation needed ]
Towers can also be used to support bridges, and can reach heights that rival some of the tallest buildings above-water. Their use is most prevalent in suspension bridges and cable-stayed bridges. The use of the pylon, a simple tower structure, has also helped to build railroad bridges, mass-transit systems, and harbors.
Control towers are used to give visibility to help direct aviation traffic.
The term "tower" is also sometimes used to refer to firefighting equipment with an extremely tall ladder designed for use in firefighting/rescue operations involving high-rise buildings.
The CN Tower is a 553.3 m-high (1,815.3 ft) concrete communications and observation tower located in the downtown core of Toronto, Ontario, Canada. Built on the former Railway Lands, it was completed in 1976. Its name "CN" originally referred to Canadian National, the railway company that built the tower. Following the railway's decision to divest non-core freight railway assets prior to the company's privatization in 1995, it transferred the tower to the Canada Lands Company, a federal Crown corporation responsible for real estate development.
Central Plaza is a 78-storey, 374 m (1,227 ft) skyscraper completed in August 1992 at 18 Harbour Road, in Wan Chai on Hong Kong Island in Hong Kong. It is the third tallest tower in the city after 2 International Finance Centre in Central and the ICC in West Kowloon. It was the tallest building in Asia from 1992 to 1996, until the Shun Hing Square was built in Shenzhen, a neighbouring city. Central Plaza surpassed the Bank of China Tower as the tallest building in Hong Kong until the completion of 2 IFC.
A skyscraper is a tall continuously habitable building having multiple floors. Modern sources currently define skyscrapers as being at least 100 metres or 150 metres in height, though there is no universally accepted definition. Skyscrapers are very tall high-rise buildings. Historically, the term first referred to buildings with between 10 and 20 stories when these types of buildings began to be constructed in the 1880s. Skyscrapers may host offices, hotels, residential spaces, and retail spaces.
The architecture of Mesopotamia is ancient architecture of the region of the Tigris–Euphrates river system, encompassing several distinct cultures and spanning a period from the 10th millennium BC, when the first permanent structures were built in the 6th century BC. Among the Mesopotamian architectural accomplishments are the development of urban planning, the courtyard house, and ziggurats. No architectural profession existed in Mesopotamia; however, scribes drafted and managed construction for the government, nobility, or royalty.
A defensive wall is a fortification usually used to protect a city, town or other settlement from potential aggressors. The walls can range from simple palisades or earthworks to extensive military fortifications with towers, bastions and gates for access to the city. From ancient to modern times, they were used to enclose settlements. Generally, these are referred to as city walls or town walls, although there were also walls, such as the Great Wall of China, Walls of Benin, Hadrian's Wall, Anastasian Wall, and the Atlantic Wall, which extended far beyond the borders of a city and were used to enclose regions or mark territorial boundaries. In mountainous terrain, defensive walls such as letzis were used in combination with castles to seal valleys from potential attack. Beyond their defensive utility, many walls also had important symbolic functions – representing the status and independence of the communities they embraced.
A spire is a tall, slender, pointed structure on top of a roof or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires are typically built of stonework or brickwork, or else of timber structure with metal cladding, ceramic tiling, shingles, or slates on the exterior.
The Galata Tower, called Christea Turris by the Genoese, is a medieval stone tower in the Galata/Karaköy quarter of Istanbul, Turkey, just to the north of the Golden Horn's junction with the Bosphorus. It is a high, cone-capped cylinder that dominates the skyline and offers a panoramic vista of Istanbul's historic peninsula and its environs.
A Tuned Mass Damper (TMD), also known as a harmonic absorber or seismic damper, is a device mounted in structures to reduce mechanical vibrations, consisting of a mass mounted on one or more damped springs. Its oscillation frequency is tuned to be similar to the resonant frequency of the object it is mounted to, and reduces the object's maximum amplitude while weighing very much less than it.
The Burj Khalifa, known as the Burj Dubai prior to its inauguration in 2010, is a skyscraper in Dubai, United Arab Emirates. With a total height of 829.8 m and a roof height of 828 m (2,717 ft), the Burj Khalifa has been the tallest structure and building in the world since its topping out in 2009, supplanting Taipei 101, the previous holder of that status.
A guyed mast or guyed tower is a tall thin vertical structure that depends on guy lines for stability. The mast itself has the compressive strength to support its own weight, but does not have the strength to stand unsupported. It requires guy lines to stay upright and to resist lateral forces such as wind loads. Guy lines are usually spaced at equal angles about the structure's base.
Kingdom Centre is a 99-story, 302.3 m (992 ft) skyscraper in Riyadh, Saudi Arabia. When completed in 2002, it overtook the 267-meter Faisaliyah Tower as the tallest tower in Saudi Arabia. It has since been surpassed and is now the fifth-tallest skyscraper in the country, whose tallest two buildings are the Abraj Al Bait Towers and the Capital Market Authority Tower. It is the world's third-tallest building with a hole after the Shanghai World Financial Center and the 85 Sky Tower in Taiwan.
An inclined tower is a tower that was intentionally built at an incline. Towers are built with an incline in order to support the weight of another structure, such as the Montreal Tower. Some towers are built with an incline due to the steep terrain upon which they stand, or simply for aesthetics.
An observation tower is a structure used to view events from a long distance and to create a full 360 degree range of vision to conduct long distance observations. Observation towers are usually at least 20 metres (66 ft) tall and are made from stone, iron, and wood. Many modern towers are also used as TV towers, restaurants, or churches. The towers first appeared in the ancient world, as long ago as the Babylonian Empire.
Radio masts and towers are typically tall structures designed to support antennas for telecommunications and broadcasting, including television. There are two main types: guyed and self-supporting structures. They are among the tallest human-made structures. Masts are often named after the broadcasting organizations that originally built them or currently use them.
The Mile-High Illinois, Illinois Sky City, or simply The Illinois is a visionary skyscraper that is proposed to be over 1 mile (1,600 m) high, conceived and described by American architect Frank Lloyd Wright in his 1957 book, A Testament. The design, intended to be built in Chicago, included 528 stories, with a gross area of 18,460,000 square feet (1,715,000 m2). Wright stated that there would be parking for 15,000 cars and 100 helicopters.
The design and construction of skyscrapers involves creating safe, habitable spaces in very high buildings. The buildings must support their weight, resist wind and earthquakes, and protect occupants from fire. Yet they must also be conveniently accessible, even on the upper floors, and provide utilities and a comfortable climate for the occupants. The problems posed in skyscraper design are considered among the most complex encountered given the balances required between economics, engineering, and construction management.
The tallest building in the world, as of 2021, is Burj Khalifa. The title of "world's tallest building" has been borne by various buildings, such as the Rouen Cathedral and the Empire State Building.
The Vainakh tower architecture, also called Nakh architecture, is a characteristic feature of ancient and medieval architecture of Chechnya and Ingushetia. Vainakh architecture was distributed to north-eastern Georgia by Vainakh builders.
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