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 not built to be habitable but to serve other functions. The principal function is the use of their height to enable various functions to be achieved including: visibility of other features attached to the tower such as clock towers; as part of a larger structure or device to increase the visibility of the surroundings for defensive purposes as in a fortified building such as a castle; as a structure for observation for leisure purposes; or as a structure for telecommunication purposes. Towers can be stand alone structures or be supported by adjacent buildings or can be a feature on top of a large 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.
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 continuously habitable high-rise building that has over 40 floors and is taller than 150 m (492 ft). Historically, the term first referred to buildings with 10 to 20 floors in the 1880s. The meaning shifted with advancing construction technology during the 20th century. 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 ziggurat is a type of massive structure built in ancient Mesopotamia. It has the form of a terraced compound of successively receding stories or levels. Notable ziggurats include the Great Ziggurat of Ur near Nasiriyah, the Ziggurat of Aqar Quf near Baghdad, the now destroyed Etemenanki in Babylon, Chogha Zanbil in Khūzestān and Sialk.
Uruk was an ancient city of Sumer situated east of the present bed of the Euphrates River on the dried-up ancient channel of the Euphrates 30 km (19 mi) east of modern Samawah, Al-Muthannā, Iraq.
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.
An inclined tower is a tower that was intentionally built at an incline. Towers are built with an incline in order 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.
A step pyramid or stepped pyramid is an architectural structure that uses flat platforms, or steps, receding from the ground up, to achieve a completed shape similar to a geometric pyramid. Step pyramids are structures which characterized several cultures throughout history, in several locations throughout the world. These pyramids typically are large and made of several layers of stone. The term refers to pyramids of similar design that emerged separately from one another, as there are no firmly established connections between the different civilizations that built them.
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 Liaodi Pagoda of Kaiyuan Monastery, Dingzhou, Hebei Province, China is the tallest existing pre-modern Chinese pagoda and tallest brick pagoda in the world, built in the 11th century during the Song dynasty (960–1279). The pagoda stands at a height of 84 meters (276 ft), resting on a large platform with an octagonal base. Upon completion in 1055, the Liaodi Pagoda surpassed the height of China's previously tallest pagoda still standing, the central pagoda of the Three Pagodas, which stands at 69.13 m (230 ft). The tallest pagoda in pre-modern Chinese history was a 100-meter (330 ft)-tall wooden pagoda tower in Chang'an built in 611 by Emperor Yang of Sui, yet this structure no longer stands.
The St. Francis Shangri-La Place, also known as The St. Francis Towers 1 & 2 are twin-tower residential condominium skyscrapers in Mandaluyong, Philippines. The towers are the 6th and 7th-tallest buildings in the country and Metro Manila as well, and are currently the second tallest twin towers in the Philippines surpassing Pacific Plaza Towers with a height of 212.88 metres from the ground to its architectural spire. It also has two of the most number of floors in the Philippines. The buildings have 60 floors above ground, including a podium which connects the two towers, and 5 basement levels for parking, and are considered as one of the most prestigious residential buildings in the Philippines.
The tallest building in the world, as of 2020, 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.
Vista Tower is a 101-story, 1,198 ft (365 m) supertall skyscraper under construction in Chicago, Illinois. Construction started in August 2016 and is expected to be completed in 2020. Upon completion, Vista Tower will become the city's third-tallest building at 1,198 ft (365 m), surpassing the Aon Center, and the tallest structure in the world designed by a woman.
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