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.
Etymology
Old Englishtorr is from
Latinturris via
Old Frenchtor. 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.)
History
Towers have been used by humankind 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 in the 3rd millennium BC, and the
Etemenanki, one of the most famous examples of
Babylonian architecture.
Some of the earliest surviving examples are the
broch structures in northern
Scotland, which are conical
tower houses. 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 towers[1] as 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.
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.
Functions
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.
Strategic advantages
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.
Potential energy
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.
Communication enhancement
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.
Transportation support
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.
Gallery
The
Galata Tower, also called Christea Turris (the Tower of Christ in Latin), was built in 1348 A.D. by the
Genoese colony in
Constantinople.
Typical modern water tower in
Carmel, Indiana, United States
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.
Etymology
Old Englishtorr is from
Latinturris via
Old Frenchtor. 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.)
History
Towers have been used by humankind 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 in the 3rd millennium BC, and the
Etemenanki, one of the most famous examples of
Babylonian architecture.
Some of the earliest surviving examples are the
broch structures in northern
Scotland, which are conical
tower houses. 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 towers[1] as 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.
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.
Functions
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.
Strategic advantages
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.
Potential energy
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.
Communication enhancement
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.
Transportation support
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.
Gallery
The
Galata Tower, also called Christea Turris (the Tower of Christ in Latin), was built in 1348 A.D. by the
Genoese colony in
Constantinople.
Typical modern water tower in
Carmel, Indiana, United States