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| | I am Mickey from Merrigum. I am learning to play the Air horn. Other hobbies are Radio-Controlled Car Racing.<br><br>Feel free to surf to my homepage - [http://stackedpixels.com/p/54 Motor Club Of America] |
| {{Use dmy dates|date=July 2012}}
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| [[File:Burj Khalifa.jpg|thumb|The [[Burj Khalifa]], tallest skyscraper in the world since 2010, with a height of 829.8m. Skyscrapers taller than 300m are also called ''Supertalls'', those taller than 600m are called ''Megatalls''.<ref>{{cite web|url=http://www.ctbuh.org/TallBuildings/HeightStatistics/BuildingsinNumbers/TheTallest20in2020/tabid/2926/language/en-US/Default.aspx |title=The Tallest 20 in 2020: Entering the Era of the Megatall |date=8 December 2011 |publisher=[[CTBUH]] |accessdate=19 October 2012}}</ref>]]
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| A '''skyscraper''' is a tall, continuously habitable building of many [[Storey|stories]], usually designed for office and commercial use. There is no official definition or height above which a building may be classified as a skyscraper. One common feature of skyscrapers is having a steel framework that supports [[curtain walls]]. These curtain walls either bear on the framework below or are possibly suspended from the framework above, rather than [[load-bearing wall]]s of conventional construction. Some early skyscrapers have a [[steel frame]] that enables the construction of load-bearing walls taller than of those made of [[reinforced concrete]]. Modern skyscrapers' walls are not load-bearing, and most skyscrapers are characterized by large surface areas of windows made possible by the concept of steel frame and curtain walls. However, skyscrapers can have curtain walls that mimic conventional walls and a small surface area of windows.
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| Skyscrapers since the 1960s use [[tube (structure)|tubular designs]] innovated by Bangladeshi-American structural engineer [[Fazlur Rahman Khan]]. This engineering principle makes the buildings structurally more efficient and stronger. It reduces the usage of material (economically much more efficient), while simultaneously allowing the buildings to reach greater heights. It allows fewer interior columns, and so creates more usable floor space. It further enables buildings to take on various shapes. There are several variations of the tubular design; these structural systems are fundamental to tall building design today.<ref>{{cite web|url=http://www.constructionweekonline.com/article-10887-on-the-rise/1/print/ |title=On the rise |publisher=Constructionweekonline.com |date=2011-01-31 |accessdate=2013-06-14}}</ref><ref name="ialcce2012.boku">{{cite web|url=https://ialcce2012.boku.ac.at/keynote_details.php?profile=5 |title=IALCCE 2012: Keynote Speakers Details |publisher=Ialcce2012.boku.ac.at |date= |accessdate=2013-06-14}}</ref><ref name="constructionweekonline.com">{{cite web|url=http://www.constructionweekonline.com/article-9180-top-10-worlds-tallest-steel-buildings/1/print/ |title=Top 10 world's tallest steel buildings |publisher=Constructionweekonline.com |date= |accessdate=2013-06-14}}</ref><ref>{{cite news| url=http://www.telegraph.co.uk/news/worldnews/middleeast/dubai/6934603/Burj-Dubai-The-new-pinnacle-of-vanity.html | work=The Daily Telegraph | first=Stephen | last=Bayley | title=Burj Dubai: The new pinnacle of vanity | date=5 January 2010}}</ref> Other pioneers include [[Srinivasa 'Hal' Iyengar|Hal Iyengar]] and [[William LeMessurier]].
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| Today, skyscrapers are an increasingly common sight where land is expensive, as in the centres of big cities, because they provide such a high ratio of rentable floor space per unit area of land. They are built not just for economy of space; like [[temples]] and [[palaces]] of the past, skyscrapers are considered symbols of a city's economic power. Not only do they define the [[skyline]], they help to define the city's identity. In some cases, exceptionally tall skyscrapers have been built not out of necessity, but to help define the city's identity and presence or power as a city.{{Citation needed|date=August 2013}}
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| ==Definition==
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| A relatively small building may be considered a skyscraper if it protrudes well above its built environment and changes the overall [[skyline]]. The maximum height of structures has progressed historically with building methods and technologies and thus what is today considered a skyscraper is taller than before. In the 21st century, the term "supertall" arose for buildings with a structural height of 300 m or more.<ref>{{cite web|url=http://standards.phorio.com/?t=definition&code=4198457539 |title=supertall building |publisher=Phorio |accessdate=7 January 2013}}</ref> The [[Council on Tall Buildings and Urban Habitat|CTBUH]] has now added the term 'megatall', for buildings with a height of 600 m or more.<ref>{{cite web|url=http://www.ctbuh.org/TallBuildings/HeightStatistics/BuildingsinNumbers/TheTallest20in2020/tabid/2926/language/en-US/Default.aspx |title=The Tallest 20 in 2020: Entering the Era of the Megatall |date=8 December 2011 |publisher=[[CTBUH]] |accessdate=19 October 2012}}</ref>
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| [[High-rise]] buildings are considered shorter than skyscrapers. The [[Home Insurance Building]] in [[Chicago]], [[United States]] was considered a skyscraper when it was built in 1884, but it had only ten stories. Today such a building would not be considered a skyscraper. There is no clear definition of any difference between a tower block and a skyscraper though a building lower than about thirty stories is not likely to be a skyscraper and a building with fifty or more stories is certainly a skyscraper.<ref>{{cite web|url=http://www.britannica.com/EBchecked/topic/547956/skyscraper |title=skyscraper (building) |publisher=Britannica.com |date=11 September 2001 |accessdate=2011-11-25}}</ref>
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| The term "skyscraper" was first applied to buildings of steel framed construction of at least 10 [[story]]s in the late 19th century, a result of public amazement at the tall buildings being built in major cities like [[Chicago]], [[New York City]], [[Philadelphia]], [[Detroit]], and [[St. Louis]].<ref>[http://magicalhystorytour.blogspot.com/2010/08/skyscrapers.html For more on the origins of the term skyscraper, see "Skyscrapers," ''Magical Hystory Tour: The Origins of the Commonplace & Curious in America'' (1 September 2010)]</ref> The first steel frame skyscraper was the [[Home Insurance Building]] (originally 10 stories with a height of {{convert|42|m|ft|abbr=on|disp=or}}) in Chicago, Illinois in 1885. Some point to Philadelphia's 10-story [[William L. Johnston|Jayne Building]] (1849–50) as a proto-skyscraper, or to New York's seven-floor [[Equitable Life Assurance Building]], built in 1870, for its innovative use of a kind of skeletal frame, but such designation depends largely on what factors are chosen. Even the scholars making the argument find it to be purely academic.<ref>{{cite journal |author=[[Charles E. Peterson]] |date=October 1950 |title=Ante-Bellum Skyscraper |journal=Journal of the Society of Architectural Historians |volume=9:3 |pages=25–28}}</ref><ref>{{cite news|url=http://findarticles.com/p/articles/mi_m1200/is_v129/ai_4501450/ |title=The first skyscraper – new theory that Home Insurance Building was not the first |date=5 April 1986 |author=Ivars Peterson |publisher=CBS Interactive |quote="In my view, we can no longer argue that the Home Insurance Building was the first skyscraper," says Carl W. Condit, now retired from Northwestern University in Evanston, Ill., and author of several books on Chicago architecture. "The claim rests on an unacceptably narrow idea of what constitutes a high-rise commercial building," he says."If there is a building in which all these technical factors—structural system, elevator, utilities—converge at the requisite level of maturity," argues Condit, "it's the Equitable Life Assurance Building in New York." Completed in 1870, the building rose 7½ stories, twice the height of its neighbors. To lighten the building and keep costs down, engineer George B. Post used a primitive type of skeletal frame in its construction. A great fire destroyed the building in 1912 |accessdate=2010-01-06}}</ref>
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| The structural definition of the word ''skyscraper'' was refined later by architectural historians, based on engineering developments of the 1880s that had enabled construction of tall multi-story buildings. This definition was based on the steel skeleton—as opposed to constructions of load-bearing [[masonry]], which passed their practical limit in 1891 with Chicago's [[Monadnock Building]].
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| {{wikiquote}}
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| {{quote|What is the chief characteristic of the tall office building? It is lofty. It must be tall. The force and power of altitude must be in it, the glory and pride of exaltation must be in it. It must be every inch a proud and soaring thing, rising in sheer exaltation that from bottom to top it is a unit without a single dissenting line.}}
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| :::—[[Louis Sullivan]]'s ''The Tall Office Building Artistically Considered'' (1896)
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| The steel frame developed in stages of increasing self-sufficiency, with several buildings in Chicago and New York advancing the technology that allowed the steel frame to carry a building on its own. Today, however, many of the tallest skyscrapers are built almost entirely with [[reinforced concrete]].<ref>{{cite book |editor1-first=Monty |editor1-last=Finniston |editor2-first=Trevor |editor2-last=Williams |editor3-first=Christopher |editor3-last=Bissell |title=Oxford Illustrated Encyclopedia of Invention and Technology |year=1992 |publisher=Oxford University Press |isbn=0-19-869138-6 |page=322 |chapter=Skyscraper |quote=Modern skyscrapers such as the World Trade Center, New York, have steel and concrete hull-and-core structures. The central core–a reinforced concrete tower–contains lift shafts, staircases, and vertical ducts. From this core, the concrete and steel composite floors span on to a steel perimeter structure; a lightweight aluminium and glass curtain wall encloses the building. This type of construction is the most efficient so far designed against wind forces.}}</ref>
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| The [[Emporis Standards Committee]] defines a [[Tower block|high-rise]] building as "a multi-story structure between 35–100 meters tall, or a building of unknown height from 12–39 floors"<ref>[http://standards.emporis.com/?nav=realestate&lng=3&esn=18727 Data Standards: high-rise building (ESN 18727)], [[Emporis Standards]], accessed on line 16 October 2009.</ref> and a skyscraper as "a multi-story building whose architectural height is at least {{convert|100|m|ft|abbr=on|disp=or}}."<ref>[http://standards.emporis.com/?nav=realestate&lng=3&esn=24419 Data Standards: skyscraper (ESN 24419)], [[Emporis Standards]], accessed on line 16 October 2009.</ref> Some [[structural engineer]]s define a highrise as any vertical construction for which wind is a more significant [[Structural load|load factor]] than [[earthquake]] or weight. Note that this criterion fits not only high-rises but some other tall structures, such as [[tower]]s.
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| The word ''skyscraper'' often carries a connotation of pride and achievement. The skyscraper, in name and social function, is a modern expression of the age-old symbol of the [[axis mundi|world center]] or ''axis mundi'': a pillar that connects earth to heaven and the four compass directions to one another.<ref>{{cite web|url=http://www.fondazione-delbianco.org/seminari/default.asp?tiporiga=A1&idprog=14&label= |title=Penza State University of Architecture and Construction; Before The Workshop (1) Tower |publisher=Fondazione-delbianco.org |date=31 August 1939 |accessdate=2011-06-05}}</ref>
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| A loose convention of some in the United States and Europe draws the lower limit of a skyscraper at {{convert|150|m|ft|abbr=on|disp=or}}.<ref>{{cite web |url=http://www.skyscrapernews.com/news.php?ref=1244 |title=Huge New Rogers Skyscraper Proposed |quote=...their eleventh proper skyscraper, that is by definition buildings above 150 meters |publisher=skyscrapernews.com |date=3 December 2007 |accessdate=2007-12-03}}</ref>
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| The term 'supertall' has {{as of|2010|alt=recently}} been coined.
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| {{quote|The [[Council on Tall Buildings and Urban Habitat]] (CTBUH) defines “supertall” as a building over {{convert|300|m|ft|abbr=on}} in height. Although great heights are now being achieved with built tall buildings—in excess of {{convert|800|m|ft|abbr=on}}—at the mid-point of 2011 there [were] only approximately 54 buildings in excess of {{convert|300|m|ft|abbr=on}} completed and occupied globally. |CTBUH<ref>{{cite web|title=CTBUH Height Criteria|url=http://www.ctbuh.org/HighRiseInfo/TallestDatabase/Criteria/tabid/446/language/en-US/Default.aspx|publisher=Council on Tall Buildings and Urban Habitat|accessdate=2011-12-07}}</ref>}}
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| Modern building practices regarding supertall structures have led to the study of "vanity height".<ref>{{cite web|url=http://www.ctbuh.org/Publications/Journal/InNumbers/TBINVanityHeight/tabid/5837/language/en-US/Default.aspx |title=Tall Buildings In Numbers Vanity Height |publisher=Ctbuh.org |date= |accessdate=2013-09-21}}</ref><ref>{{cite web|url=http://www.worldarchitecturenews.com/index.php?fuseaction=wanappln.showbriefdetail&newsid=2061 |title=CTBUH releases list of supertall towers with highest percentages of 'vanity height' |publisher=World Architecture News |date= |accessdate=2013-09-21}}</ref> Vanity height, according to the CTBUH, is the distance between the highest floor and its architectural top (excluding antennae, flagpole or other functional extensions). Vanity height first appeared in New York City skyscrapers as early as the 1920s and 1930s but recent supertall buildings have relied on such uninhabitable extensions for on average 30% of their height, raising potential definitional and sustainability issues.<ref>{{cite web|url=http://www.theatlanticcities.com/design/2013/09/most-worlds-tallest-buildings-game-system-vanity-height/6822/ |title=Most of the World's Tallest Buildings Game the System With 'Vanity Height' - Jenny Xie |publisher=The Atlantic Cities |date=2013-09-09 |accessdate=2013-09-21}}</ref><ref>{{cite web|last=Lecher |first=Colin |url=http://www.popsci.com/technology/article/2013-09/worlds-tallest-skyscrapers-have-insane-amount-unoccupied-space |title=The World's Tallest Skyscrapers Have A Dirty Little Secret | Popular Science |publisher=Popsci.com |date= |accessdate=2013-09-21}}</ref><ref>{{cite web|author=The Associated Press |url=http://www.nydailynews.com/news/national/height-uselessness-article-1.1448935 |title=World's tallest skyscapers? Only if 'useless' needles count |publisher=NY Daily News |date=2013-09-07 |accessdate=2013-09-21}}</ref>
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| ==History==
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| [[Image:2tours bologne 082005.jpg|thumb|180px|The [[Towers of Bologna|Two Towers of Bologna]] in the 12th century reached {{convert|97.2|m|ft|abbr =on}} in height.]]
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| [[Image:Shibam Wadi Hadhramaut Yemen.jpg|thumb|180px|The 16th-century city of [[Shibam]] consisted entirely of over 500 high-rise tower houses.]]
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| ===Pre-19th century===
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| Until the 19th century, buildings of over six stories were rare, as having great numbers of stairs to climb was impractical for inhabitants, and [[fluid pressure|water pressure]] was usually insufficient to supply running water above {{Convert|50|m|ft|0|abbr=on}}.
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| The tallest building in ancient times was the {{convert|146|m|ft|abbr =on}} [[Great Pyramid of Giza]] in [[ancient Egypt]], built in the 26th century BCE. It was not surpassed in height for thousands of years, the 14th century CE [[Lincoln Cathedral]] being conjectured by many to exceed it.<ref>{{cite web|author=A.F.K. |url=http://gwydir.demon.co.uk/PG/BellsLincoln/BellsLincoln.htm |title=The Project Gutenberg eBook of The Cathedral Church of Lincoln, by A.F. Kendric, B.A |publisher=Gwydir.demon.co.uk |accessdate=2011-06-05}}</ref> The latter in turn was not surpassed until the {{convert|555|ft|m|sp=us|adj=on}} [[Washington Monument]] in 1884. However, being uninhabited, none of these structures actually comply with the modern definition of a skyscraper.
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| High-rise apartments flourished in [[classical antiquity]]. [[Ancient Rome|Ancient Roman]] [[insulae]] there and in other [[Roman Empire|imperial]] cities reached 10 and more stories.<ref name="Gregory S. Aldrete">Gregory S. Aldrete: "Daily Life in the Roman City: Rome, Pompeii and Ostia", 2004, ISBN 978-0-313-33174-9, p.79f.</ref> Beginning with [[Augustus]] (r. 30 BCE-14 CE), several [[Roman emperor|emperors]] attempted to establish limits of 20–25 m for multi-story buildings, but met with only limited success.<ref>[[Strabo]], 5.3.7</ref><ref>Alexander G. McKay: Römische Häuser, Villen und Paläste, [[Feldmeilen]] 1984, ISBN 3-7611-0585-1 p. 231</ref> Lower floors were typically occupied by shops or wealthy families, the upper rented to the lower classes.<ref name="Gregory S. Aldrete"/> Surviving [[Oxyrhynchus Papyri]] indicate that seven-story buildings existed in [[Roman province|provincial]] towns such as in 3rd century CE [[Hermopolis]] in [[History of Roman Egypt|Roman Egypt]].<ref>Papyrus Oxyrhynchus 2719, in: Katja Lembke, Cäcilia Fluck, Günter Vittmann: ''Ägyptens späte Blüte. Die Römer am Nil'', Mainz 2004, ISBN 3-8053-3276-9, p.29</ref>
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| The skylines of many important [[Middle Ages|medieval]] cities had large numbers of high-rise urban towers, built by the wealthy for defense and status. The residential [[Towers of Bologna|Towers]] of 12th century [[Bologna]] numbered between 80 to 100 at a time, the tallest of which is the {{convert|97.2|m|ft|abbr =on}} high Asinelli Tower. A [[Florence|Florentine]] law of 1251 decreed that all urban buildings be immediately reduced to less than 26 m.<ref name="Werner Müller 345">Werner Müller: "dtv-Atlas Baukunst I. Allgemeiner Teil: Baugeschichte von Mesopotamien bis Byzanz", 14th ed., 2005, ISBN 978-3-423-03020-5, p.345</ref> Even medium-sized towns of the era are known to have proliferations of towers, such as the 72 up to 51 m height in [[San Gimignano]].<ref name="Werner Müller 345"/>
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| The [[History of Arab Egypt|medieval Egyptian]] city of [[Fustat]] housed many high-rise residential buildings, which [[Al-Muqaddasi]] in the 10th century described as resembling [[minaret]]s. [[Nasir Khusraw]] in the early 11th century described some of them rising up to 14 stories, with [[roof garden]]s on the top floor complete with ox-drawn [[water wheel]]s for irrigating them.<ref>{{Cite book|title=Islamic Architecture in Cairo|first=Doris|last=Behrens-Abouseif|year=1992|publisher=[[Brill Publishers]]|isbn=90-04-09626-4|page=6}}</ref> [[Cairo]] in the 16th century had high-rise [[apartment building]]s where the two lower floors were for commercial and storage purposes and the multiple stories above them were [[Renting|rented]] out to [[Leasehold estate|tenants]].<ref>{{Cite book|title=Traditional Islamic principles of built environment|first=Hisham|last=Mortada|publisher=[[Routledge]]|year=2003|isbn=0-7007-1700-5|page=viii}}</ref> An early example of a city consisting entirely of high-rise housing is the 16th-century city of [[Shibam]] in [[Yemen]]. Shibam was made up of over 500 tower houses,<ref name=UNESCO/> each one rising 5 to 11 stories high,<ref>{{Cite journal|title=Land without shade|first=Hans|last=Helfritz|journal=Journal of the Royal Central Asian Society|volume=24|issue=2|date=April 1937|pages=201–16|doi=10.1080/03068373708730789}}</ref> with each floor being an [[apartment]] occupied by a single family. The city was built in this way in order to protect it from [[Bedouin]] attacks.<ref name=UNESCO>[http://whc.unesco.org/en/list/192 Old Walled City of Shibam], [[UNESCO]]</ref> Shibam still has the tallest [[mudbrick]] buildings in the world, with many of them over {{convert|30|m|ft|abbr=on}} high.<ref>{{Cite journal|title=The Hadhramaut|first=J. G. T.|last=Shipman|journal=Asian Affairs|volume=15|issue=2|date=June 1984|pages=154–62|doi=10.1080/03068378408730145}}</ref>
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| An early modern example of high-rise housing was in 17th-century [[Edinburgh]], Scotland, where a defensive city wall defined the boundaries of the city. Due to the restricted land area available for development, the houses increased in height instead. Buildings of 11 stories were common, and there are records of buildings as high as 14 stories. Many of the stone-built structures can still be seen today in the old town of Edinburgh. The oldest iron framed building in the world, although only partially iron framed, is [[Ditherington Flax Mill|The Flaxmill]] (also locally known as the "Maltings"), in [[Shrewsbury]], England. Built in 1797, it is seen as the "grandfather of skyscrapers”, since its fireproof combination of cast iron columns and cast iron beams developed into the modern steel frame that made modern skyscrapers possible. In 2013 funding was confirmed to convert the derelict building into offices.<ref>{{cite web |url=http://www.bbc.co.uk/news/uk-england-shropshire-23495105 |title=Shrewsbury Flax Mill: Funding for offices and restoration |author=<!--Staff writer(s); no by-line.--> |date=30 July 2013 |website=http://www.bbc.co.uk/news |publisher=BBC News |accessdate=30 July 2013}}</ref>
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| [[Image:Oriel chambers.jpg|thumb|180px|[[Oriel Chambers]], Liverpool. The world's first glass curtain walled building. The stone [[mullion]]s are decorative.]]
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| [[Image:Wainwright building st louis USA.jpg|thumb|180px|The [[Wainwright Building]], a 10-story red brick office building in [[St. Louis, Missouri]], built in 1891]]
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| ===Early skyscrapers===
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| {{main|Early skyscrapers}}
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| In 1852 [[Elisha Otis]] introduced the safety elevator, allowing convenient and safe passenger movement to upper floors. Another crucial development was the use of a steel frame instead of stone or brick, otherwise the walls on the lower floors on a tall building would be too thick to be practical. An early development in this area was [[Oriel Chambers]] in Liverpool. Designed by local architect Peter Ellis in 1864, the building was the world's first iron-framed, glass curtain-walled office building. It was only 5 floors high.<ref>{{cite web|title=Oriel Chambers |publisher=Liverpool Architectural Society |url=http://www.liverpoolarchitecture.com/tours/buildings/building.php?id=25 |accessdate=2009-07-14}}</ref><ref>[http://www.youtube.com/watch?v=S_pQPhVWNTY Manchester School of Architecture video] YouTube</ref><ref>[http://www.bdonline.co.uk/story.asp?sectioncode=428&storycode=3155796&channel=783&c=2 Building Design] Architect's website, 8 January 2010</ref> Further developments led to the world's first skyscraper, the ten-story [[Home Insurance Building]] in Chicago, built in 1884–1885.<ref name="Verbivore's Feast, p289">{{cite book|last=Smith|first=Chrysti M. |title=Verbivore's Feast: Second Course: More Word & Phrase Origins|publisher=Farcountry Press|year=2006|page=289|isbn=1-56037-402-0, 9781560374022|url=http://books.google.com/books?id=d3bov9J_1w0C&pg=PA289#v=onepage&q&f=false|accessdate=2012-01-19|quote=The word ''skyscraper'', in its architectural context, was first applied to the Home Insurance Building, completed in Chicago in 1885.}}</ref> While its height is not considered very impressive today, it was at that time. The architect, Major [[William Le Baron Jenney]], created a load-bearing structural frame. In this building, a steel frame supported the entire weight of the walls, instead of load-bearing walls carrying the weight of the building. This development led to the "Chicago skeleton" form of construction. In addition to the steel frame, the Home Insurance Building also utilized fireproofing, elevators, and electrical wiring, key elements in most skyscrapers today.<ref>Dupré, Judith. Skyscrapers. New York: Black Dog & Leventhal, 1996. Print.</ref>
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| [[Burnham and Root]]'s 1889 [[Rand McNally Building]] in Chicago, 1889, was the first all-steel framed skyscraper,<ref>{{cite web|url=http://encyclopedia.chicagohistory.org/pages/300004.html |title=The Plan Comes Together - Encyclopedia of Chicago |publisher=Encyclopedia.chicagohistory.org |date= |accessdate=2013-07-27}}</ref> while [[Louis Sullivan]]'s [[Wainwright Building]] in St. Louis, Missouri, 1891, was the first [[steel-framed building]] with soaring vertical bands to emphasize the height of the building and is therefore considered by some to be the first true skyscraper.
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| Most early skyscrapers emerged in the land-strapped areas of Chicago, London, and New York toward the end of the 19th century. A land boom in Melbourne, Australia between 1888–1891 spurred the creation of a significant number of early skyscrapers, though none of these were steel reinforced and few remain today. Height limits and fire restrictions were later introduced. London builders soon found building heights limited due to a complaint from Queen Victoria, rules that continued to exist with few exceptions until the 1950s. Concerns about aesthetics and fire safety had likewise hampered the development of skyscrapers across continental Europe for the first half of the twentieth century (with the notable exceptions of the 1898 [[Witte Huis]] ''(White House)'' in Rotterdam; the [[Royal Liver Building]] in Liverpool, completed in 1911 and {{convert|90|m|ft|abbr=on}} high;<ref>{{cite web|title=Royal Liver Building |work=[[Encyclopædia Britannica]] |url=http://www.britannica.com/EBchecked/topic/511448/Royal-Liver-Building |accessdate=2011-06-23}}</ref> and the 17-story [[Kungstornen]] ''(Kings' Towers)'' in Stockholm, Sweden, which were built 1924–25,<ref>{{cite book|last=Hultin |first=Olof |coauthors=Bengt O H Johansson, Johan Mårtelius, Rasmus Wærn |title=The Complete Guide to Architecture in Stockholm |publisher=Arkitektur Förlag |year=1998 |location=Stockholm |page=62 |isbn=91-86050-43-5}}</ref> the 15-story [[Edificio Telefónica]] in Madrid, Spain, built in 1929; the 26-story [[Boerentoren]] in Antwerp, Belgium, built in 1932; and the 31-story [[Terrazza Martini Tower|Torre Piacentini]] in Genoa, Italy, built in 1940). After an early competition between Chicago and New York City for the world's tallest building, New York took the lead by 1895 with the completion of the [[American Surety Building]], leaving New York with the title of tallest building for many years. New York City developers competed among themselves, with successively taller buildings claiming the title of "world's tallest" in the 1920s and early 1930s, culminating with the completion of the [[Chrysler Building]] in 1930 and the [[Empire State Building]] in 1931, the world's tallest building for forty years. The first completed [[World Trade Center]] tower became the world's tallest building in 1972. However, it was soon overtaken by the Sears Tower (now [[Willis Tower]]) in Chicago within two years. The Sears Tower stood as the world's tallest building for 24 years, from 1974 until 1998, until it was edged out by [[Petronas Twin Towers]] in Kuala Lumpur, which held the title for six years.
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| ===Modern skyscrapers===
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| [[Image:Empire State Building from the Top of the Rock.jpg|thumb|180px|The [[Empire State Building]] in New York City. Completed in 1931, it was the tallest building in the world for nearly 40 years.]]
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| Modern skyscrapers are built with [[steel]] or [[reinforced concrete]] frameworks and [[curtain wall]]s of [[glass]] or polished [[stone]]. They utilize mechanical equipment such as [[water pump]]s and [[elevator]]s.
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| From the 1930s onwards, skyscrapers began to appear around the world - also in Latin America (such as [[São Paulo]], [[Rio de Janeiro]], [[Buenos Aires]], [[Santiago, Chile|Santiago]], [[Caracas]], [[Bogotá]], [[Mexico City]]) and in Asia ([[Tokyo]], [[Shanghai]], [[Hong Kong]], [[Manila]], [[Singapore]], [[Mumbai]], [[Seoul]], [[Kuala Lumpur]], [[Taipei]], [[Bangkok]]).
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| Immediately after [[World War II]], the [[Soviet Union]] planned eight massive skyscrapers dubbed "[[Seven Sisters (Moscow)|Stalin Towers]]" for Moscow; seven of these were eventually built. The rest of Europe also slowly began to permit skyscrapers, starting with [[Madrid]], during the 1950s. Finally, skyscrapers also began to be constructed in cities of Africa, the Middle East and Oceania (mainly Australia) from the late 1950s. After the [[Great Depression]] skyscrapers construction was abandoned for over thirty years.{{where|date=February 2013}}<ref>{{cite web|url=https://docs.google.com/viewer?a=v&q=cache:2RHuSbYRzRMJ:www.crcnetbase.com/doi/abs/10.4324/NOE0415232418.ch32+fazlur+khan+transformed+city+skyline&hl=en&pid=bl&srcid=ADGEESihn5j7rJIRtFoJCbwq8wShPOaHpe58yoE73coq6B9k34MzK5KG_g4uiZBYe3eN3-tzyegycQt0R19bl_DyxG3n6VhbUB22qDRSmc7qpRhhOFaROXHdb6uDXuP8wMukBd_aP404&sig=AHIEtbTdAXBk_8DZzecEJPiR1Tubq-RmxQ |title=Google Drive Viewer |publisher=Docs.google.com |date= |accessdate=2013-06-14}}</ref>
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| [[Germany|German]] architect [[Ludwig Mies van der Rohe]] became one of the world's most renowned architects in the second half of the 20th century. He conceived of the glass façade skyscraper<ref>{{cite book|year=2006|title=A Dictionary of Architecture and Landscape Architecture|publisher=Oxford University Press|page=880|isbn=0-19-860678-8}}</ref> and designed the [[Seagram Building]] in 1958, a skyscraper that is often regarded as the pinnacle of the modernist high-rise architecture.<ref name=obit>{{cite news |first= |last= |authorlink= |coauthors= |title=Mies van der Rohe Dies at 83; Leader of Modern Architecture |url=http://www.nytimes.com/learning/general/onthisday/bday/0327.html |quote=Mies van der Rohe, one of the great figures of 20th-century architecture. |publisher=''[[The New York Times]]'' |date=August 17, 1969 |accessdate=2007-07-21 }}</ref>
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| In the early 1960s structural engineer Fazlur Khan realized that the rigid [[steel frame]] structure that had dominated tall building design and construction so long was not the only system fitting for tall buildings, marking the beginning of a new era of skyscraper revolution in terms of multiple [[structural system]]s.<ref>{{Cite journal|last=Mir M. Ali|first=Kyoung Sun Moon|title=Structural developments in tall buildings: current trends and future prospects|journal=Architectural Science Review|issue=September 2007|url=http://www.accessmylibrary.com/coms2/summary_0286-32962093_ITM|accessdate=2008-12-10}}</ref> His central innovation in [[skyscraper design and construction]] was the idea of the [[Tube (structure)|"tube" structural system]], including the "framed tube", "trussed tube", and "bundled tube".<ref name=Ali>{{Cite journal|title=Evolution of Concrete Skyscrapers: from Ingalls to Jin mao|first=Mir M.|last=Ali|journal=Electronic Journal of Structural Engineering|volume=1|issue=1|year=2001|pages=2–14|url=http://www.ejse.org/Archives/Fulltext/200101/01/20010101.htm|accessdate=2008-11-30}}</ref> These systems allowed far greater economic efficiency,<ref name=Britannica>{{cite web|author=Alfred Swenson & Pao-Chi Chang|title=Building construction: High-rise construction since 1945|work=[[Encyclopædia Britannica]]|year=2008|url=http://www.britannica.com/EBchecked/topic/83859/building-construction/60143/High-rise-construction-since-1945#toc60143|accessdate=2008-12-09}}</ref> and also allowed efficient skyscrapers to take on various shapes, no longer needing to be box-shaped.<ref name=Banglapedia>{{cite web|title=Khan, Fazlur Rahman|work=[[Banglapedia]]|url=http://banglapedia.search.com.bd/HT/K_0187.htm|accessdate=2008-12-09}}</ref> Over the next fifteen years, many towers were built by Khan and the "[[Chicago School (architecture)|Second Chicago School]]",<ref name=Billington>{{Cite book|title=The Tower and the Bridge: The New Art of Structural Engineering|first=David P.|last=Billington|publisher=[[Princeton University Press]]|year=1985|isbn=0-691-02393-X|pages=234–5}}</ref> including the massive {{convert|442|m|ft|abbr=on}} [[Willis Tower]].<ref>{{cite web|url=http://www.emporis.com/en/wm/ci/bu/sk/li/?id=101030&bt=9&ht=3&sro=81 |title=List of Tallest skyscrapers in Chicago |publisher=Emporis.com |date=15 June 2009 |accessdate=2011-06-05}}</ref> The [[tube (structure)|tubular systems]] are fundamental to tall building design. Since 2000, cities such as Chicago,<ref>{{cite web|url=http://thestandard.com.hk/news_detail.asp?we_cat=16&art_id=21823&sid=8582464&con_type=1&d_str=20060630 |title=Chicago Building Boom |publisher=Thestandard.com.hk |date= |accessdate=2013-07-27}}</ref> Shanghai,<ref>{{cite web |title=China's building boom becomes a frenzy |url=http://www.iht.com/articles/2005/10/18/news/boom.php |publisher=International Herald Tribune |author=David Barboza |date=18 October 2005 |accessdate=2008-08-07}}</ref> Dubai,<ref>{{cite web|url=http://www.emirates247.com/news/emirates/909-high-rises-448-skyscrapers-in-dubai-but-do-you-know-how-to-survive-an-earthquake-2013-04-16-1.502399 |title=909 high-rises, 448 skyscrapers in Dubai... But do you know how to survive an earthquake? |author=Vicky Kapur |publisher=Dubai Media Incorporated |website=Emirates 24/7 |date=16 April 2013 |accessdate=14 June 2013}}</ref> and New York have experienced a huge surge in skyscraper construction, thanks to the new tubular design. Chicago, Hong Kong, and New York City, otherwise known as "the big three," are recognized in architectural circles as having especially compelling skylines. A landmark skyscraper can inspire a boom of new high-rise projects in its city, as Taipei 101 has done in Taipei since its opening in 2004. In 2010, The Bank of America Tower at One Bryant Park became the world's first commercial LEED Platinum skyscraper.
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| ==Design and construction==
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| {{Main|Skyscraper design and construction}}
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| The design and construction of skyscrapers involves creating safe, habitable spaces in very tall 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]], [[Civil Engineering|engineering]], and [[construction]] management.
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| One common feature of skyscrapers is having a steel framework from which curtain walls are suspended, rather than load-bearing walls of conventional construction. Most skyscrapers have a steel frame that enables to build taller than load-bearing walls of reinforced concrete. Skyscrapers usually have particularly small surface area of what are conventionally thought of as walls, because the walls are not load-bearing and therefore most skyscrapers are characterized by large surface areas of windows made possible by the concept of steel frame and curtain walls. However, skyscrapers can have curtain walls that mimick conventional walls and a small surface area of windows.
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| The concept of a skyscraper is a product of the [[Industrial society|industrialized age]], made possible by cheap [[fossil fuel]] derived energy and industrially refined raw materials such as [[steel]] and [[concrete]]. The construction of skyscrapers was enabled by [[steel frame]] construction that surpassed [[brick and mortar]] construction starting at the end of the 19th century and finally surpassing it in the 20th century together with [[reinforced concrete]] construction as the price of steel decreased and labour costs increased.
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| The steel frames become inefficient and uneconomic for supertall buildings as usable floor spaces are reduced for supporting column and due to more usage of steel.<ref name="lehigh.edu">{{cite web|url=http://www.lehigh.edu/~infrk/2011.08.article.html |title=Lehigh University: Fazlur Rahman Khan Distinguished Lecture Series |publisher=Lehigh.edu |date= |accessdate=2013-06-14}}</ref> Since about 1960, tubular designs have been used for high rises. This reduces the usage of material (more efficient in economic terms - [[Willis Tower]] uses a third less steel than the Empire State Building) yet allows greater height. It allows fewer interior columns, and so creates more usable floor space. It further enables buildings to take on various shapes.
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| [[Elevator]]s are characteristic to skyscrapers. In 1852 Elisha Otis introduced the safety elevator, allowing convenient and safe passenger movement to upper floors. Another crucial development was the use of a steel frame instead of stone or brick, otherwise the walls on the lower floors on a tall building would be too thick to be practical. Today major manufacturers of elevators include [[Otis Elevator Company|Otis]], [[ThyssenKrupp AG|ThyssenKrupp]], [[Schindler Group|Schindler]], and [[KONE]].
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| ===Basic design considerations===
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| Good structural design is important in most building design, but particularly for skyscrapers since even a small chance of catastrophic failure is unacceptable given the high price. This presents a paradox to civil engineers: the only way to assure a lack of failure is to test for all modes of failure, in both the laboratory and the real world. But the only way to know of all modes of failure is to learn from previous failures. Thus, no engineer can be absolutely sure that a given structure will resist all loadings that could cause failure, but can only have large enough margins of safety such that a failure is acceptably unlikely. When buildings do fail, engineers question whether the failure was due to some lack of foresight or due to some unknowable factor.
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| ===Loading and vibration===
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| The load a skyscraper experiences is largely from the force of the building material itself. In most building designs, the weight of the structure is much larger than the weight of the material that it will support beyond its own weight. In technical terms, the [[dead load]], the load of the structure, is larger than the [[live load]], the weight of things in the structure (people, furniture, vehicles, etc.). As such, the amount of structural material required within the lower levels of a skyscraper will be much larger than the material required within higher levels. This is not always visually apparent. The [[Empire State Building|Empire State Building's]] [[Setback (architecture)|setbacks]] are actually a result of the building code at the time, and were not structurally required. On the other hand [[John Hancock Center|John Hancock Center's]] shape is uniquely the result of how it supports loads. Vertical supports can come in several types, among which the most common for skyscrapers can be categorized as steel frames, concrete cores, tube within tube design, and shear walls.
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| The wind loading on a skyscraper is also considerable. In fact, the lateral wind load imposed on super-tall structures is generally the governing factor in the structural design. Wind pressure increases with height, so for very tall buildings, the loads associated with wind are larger than dead or live loads.
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| Other vertical and horizontal loading factors come from varied, unpredictable sources, such as earthquakes. | |
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| ===Shear walls===
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| A shear wall, in its simplest definition, is a wall where the entire material of the wall is employed in the resistance of both horizontal and vertical loads. A typical example is a [[brick]] or [[cinderblock]] wall. Since the wall material is used to hold the weight, as the wall expands in size, it must hold considerably more weight. Due to the features of a shear wall, it is acceptable for small constructions, such as suburban housing or an urban brownstone, to require low material costs and little maintenance. In this way, shear walls, typically in the form of [[plywood]] and framing, brick, or cinderblock, are used for these structures. For skyscrapers, though, as the size of the structure increases, so does the size of the supporting wall. Large structures such as [[castle]]s and [[cathedral]]s inherently addressed these issues due to a large wall being advantageous (castles), or ingeniously designed around (cathedrals). Since skyscrapers seek to maximize the floor-space by consolidating structural support, shear walls tend to be used only in conjunction with other support systems.
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| ===Steel frame===
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| The classic concept of a skyscraper is a large steel box with many small boxes inside it. The genius of the [[steel]] frame is its simplicity. By eliminating the inefficient part of a shear wall, the central portion, and consolidating support members in a much stronger material, steel, a skyscraper could be built with both horizontal and vertical supports throughout. This method, though simple, has drawbacks. Chief among these is that as more material must be supported (as height increases), the distance between supporting members must decrease, which actually in turn, increases the amount of material that must be supported. This becomes inefficient and uneconomic for buildings above 40 stories tall as usable floor spaces are reduced for supporting column and due to more usage of steel.<ref name="lehigh.edu"/>
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| ===Tube structural systems===
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| {{see also|Tube (structure)}}
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| [[File:KM 5939 sears tower august 2007 B.jpg|thumb|180px|The [[Willis Tower]] showing the bundled tube frame design]]
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| Since 1963, a new structural system of framed tubes appeared. [[Fazlur Khan]] and J. Rankine defined the framed tube structure as "a three dimensional space structure composed of three, four, or possibly more frames, braced frames, or shear walls, joined at or near their edges to form a vertical tube-like structural system capable of resisting lateral forces in any direction by cantilevering from the foundation."<ref>{{cite web
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| | title = Evolution of Concrete Skyscrapers
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| | url = http://www.civenv.unimelb.edu.au/ejse/Archives/Fulltext/200101/01/20010101.htm
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| }}</ref> Closely spaced interconnected exterior columns form the tube. Horizontal loads (primarily wind) are supported by the structure as a whole. About half the exterior surface is available for windows. Framed tubes allow fewer interior columns, and so create more usable floor space. Where larger openings like garage doors are required, the tube frame must be interrupted, with transfer girders used to maintain structural integrity. Tube structures cut down costs, at the same time allow buildings to reach greater heights. Tube-frame construction was first used in the [[DeWitt-Chestnut Apartment Building]], completed in [[Chicago]] in 1963.<ref>{{cite web|author=Alfred Swenson & Pao-Chi Chang|title=building construction|publisher=''[[Encyclopædia Britannica]]''|year=2008|url=http://www.britannica.com/EBchecked/topic/83859/building-construction|accessdate=2008-12-09}}</ref> It was used soon after for the [[John Hancock Center]] and in the [[construction of the World Trade Center]].
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| A variation on the tube frame is the bundled tube, which uses several interconnected tube frames. The [[Willis Tower]] in Chicago used this design, employing nine tubes of varying height to achieve its distinct appearance. The bundle tube design was not only highly efficient in economic terms, but it was also "innovative in its potential for versatile formulation of architectural space. Efficient towers no longer had to be box-like; the tube-units could take on various shapes and could be bundled together in different sorts of groupings."<ref name="Banglapedia"/> The bundled tube structure meant that "buildings no longer need be boxlike in appearance: they could become sculpture."<ref name=Bayley/>
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| The [[tube (structure)|tubular systems]] are fundamental to tall building design. Most buildings over 40-stories constructed since the 1960s now use a tube design derived from Khan’s structural engineering principles,<ref name="constructionweekonline.com"/><ref name="lehigh.edu"/> examples including the [[construction of the World Trade Center]], [[Aon Center (Chicago)|Aon Center]], [[Petronas Towers]], [[Jin Mao Building]], and most other [[supertall]] skyscrapers since the 1960s.<ref name=Ali>{{Cite journal|title=Evolution of Concrete Skyscrapers: from Ingalls to Jin mao|first=Mir M.|last=Ali|journal=Electronic Journal of Structural Engineering|volume=1|issue=1|year=2001|pages=2–14|url=http://www.ejse.org/Archives/Fulltext/200101/01/20010101.htm|accessdate=2008-11-30|postscript=<!-- Bot inserted parameter. Either remove it; or change its value to "." for the cite to end in a ".", as necessary. -->{{inconsistent citations}}}}</ref> The strong influence of tube structure design is also evident in the construction of the current tallest skyscraper, the [[Burj Khalifa]].<ref name=Bayley>{{cite news|title=Burj Dubai: The new pinnacle of vanity|author=Stephen Bayley|work=[[The Daily Telegraph]]|date=5 January 2010|url=http://www.telegraph.co.uk/news/worldnews/middleeast/dubai/6934603/Burj-Dubai-The-new-pinnacle-of-vanity.html|accessdate=2010-02-26}}</ref>
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| ====Trussed tube and X-bracing====
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| [[File:Skyscraper structure.png|thumb|left|Changes of structure with height. The [[Tube (structure)|tubular systems]] are fundamental for super tall buildings.]]
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| Khan pioneered several other variations of the tube structure design. One of these was the concept of [[X-bracing]], or the "[[Tube (structure)#Trussed tube|trussed tube]]", first employed for the [[John Hancock Center]]. This concept reduced the lateral load on the building by transferring the load into the exterior columns. This allows for a reduced need for interior columns thus creating more floor space. This concept can be seen in the John Hancock Center, designed in 1965 and completed in 1969. One of the most famous buildings of the [[Structural Expressionism|structural expressionist]] style, the skyscraper's distinctive X-bracing exterior is actually a hint that the structure's skin is indeed part of its 'tubular system'. This idea is one of the architectural techniques the building used to climb to record heights (the tubular system is essentially the spine that helps the building stand upright during wind and [[seismic loading|earthquake loads]]). This X-bracing allows for both higher performance from tall structures and the ability to open up the inside floorplan (and usable floor space) if the architect desires.
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| In contrast to earlier [[Steel frame|steel-frame]] structures, such as the [[Empire State Building]] (1931), which required about 206 kilograms of steel per square metre and [[Chase Manhattan Bank Building]] (1961), which required around 275 kilograms of steel per square metre, the John Hancock Center was far more efficient, requiring only 145 kilograms of steel per square metre.<ref name=Britannica/> The trussed tube concept was applied to many later skyscrapers, including the [[Onterie Center]], [[Citigroup Center]] and [[Bank of China Tower, Hong Kong|Bank of China Tower]].<ref name="Introduction to Tall Building architectures">{{cite web |url=http://teaching.ust.hk/~civl101/Civl101%20-%20Introduction%20to%20Tall%20Building%20Structures.pdf |format=PDF |page=34 |title=Introduction to Tall building Structures |author= Dr. D. M Chan |publisher=Teaching.ust.hk}}</ref>
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| ====Bundle tube====
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| One of Khan's most important variations of the tube structure concept was the "[[Tube (structure)#Bundled tube|bundled tube]]," which he used for the [[Sears Tower]] and [[One Magnificent Mile]]. The bundle tube design was not only the most efficient in economic terms, but it was also "innovative in its potential for versatile formulation of architectural space. Efficient towers no longer had to be box-like; the tube-units could take on various shapes and could be bundled together in different sorts of groupings."<ref name=Banglapedia/><ref>{{cite web|title=Fazlur R. Khan|publisher=[[Encyclopædia Britannica]]|year=2008|url=http://www.britannica.com/EBchecked/topic/316259/Fazlur-R-Khan|accessdate=2008-12-10}}</ref>
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| ====Concrete tube structures====
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| The last major buildings engineered by Khan were the [[One Magnificent Mile]] and [[Onterie Center]] in Chicago, which employed his bundled tube and trussed tube system designs respectively. In contrast to his earlier buildings, which were mainly [[steel]], his last two buildings were [[concrete]]. His earlier DeWitt-Chestnut Apartments building, built in 1963 in Chicago, was also a concrete building with a tube structure.<ref name=Ali/>
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| The influence of Khan's tube structure design can be seen in numerous buildings built since the 1960s. Tube structures have since been used in many skyscrapers, including the [[construction of the World Trade Center]], [[Petronas Towers]], [[Jin Mao Building]], and most other [[supertall]] skyscrapers since the 1960s.<ref name=Ali/> The strong influence of tube structure design is also evident in the world's current tallest skyscraper, the [[Burj Khalifa]] in [[Dubai]]. According to Stephen Bayley of ''[[The Daily Telegraph]]'':
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| {{quote|Khan invented a new way of building tall. [...] Which created the unconventional skyscraper. Reversing the logic of the steel frame, he decided that the building's external envelope could – given enough trussing, framing and bracing – be the structure itself. This made buildings even lighter. The "bundled tube" meant buildings no longer need be boxlike in appearance: they could become sculptures.}}
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| ===The elevator conundrum===
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| The invention of the [[elevator]] was a precondition for the invention of skyscrapers, given that most people would not (or could not) climb more than a few flights of stairs at a time. The elevators in a skyscraper are not simply a necessary utility, like running water and electricity, but are in fact closely related to the design of the whole structure: a taller building requires more elevators to service the additional floors, but the elevator shafts consume valuable floor space. If the service core, which contains the elevator shafts, becomes too big, it can reduce the profitability of the building. Architects must therefore balance the value gained by adding height against the value lost to the expanding service core.<ref name="HSW3">{{cite web|url=http://science.howstuffworks.com/skyscraper3.htm|title=How Skyscrapers Work: Making it Functional|publisher=HowStuffWorks|accessdate=2008-10-30}}</ref> Many tall buildings use elevators in a non-standard configuration to reduce their footprint. Buildings such as the former [[World Trade Center Towers]] and Chicago's [[John Hancock Center]] use [[sky lobby|sky lobbies]], where express elevators take passengers to upper floors which serve as the base for local elevators. This allows architects and engineers to place elevator shafts on top of each other, saving space. Sky lobbies and express elevators take up a significant amount of space, however, and add to the amount of time spent commuting between floors. Other buildings, such as the [[Petronas Towers]], use [[double-deck elevator]]s, allowing more people to fit in a single elevator, and reaching two floors at every stop. It is possible to use even more than two levels on an elevator, although this has never been done. The main problem with double-deck elevators is that they cause everyone in the elevator to stop when only people on one level need to get off at a given floor.
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| ===Sky lobby===
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| The first [[sky lobby]] was also designed by Khan for the John Hancock Center. Later buildings with sky lobbies include the [[World Trade Center]], [[Petronas Twin Towers]] and [[Taipei 101]]. The 44th-floor sky lobby of the John Hancock Center also features the first [[high-rise]] indoor [[swimming pool]], which remains the highest in America.<ref name=Emporis>[http://www.emporis.com/en/wm/bu/?id=116876 John Hancock Center], [[Emporis]]</ref> This was the first time that people could have the opportunity to work and live "in the sky".<ref name=Banglapedia/>
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| ==Economic rationale==
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| Skyscrapers are usually situated in [[city center]]s where the price of land is high. Constructing a skyscraper becomes justified if the price of land is so high that it makes [[economics|economic]] sense to build upwards as to minimize the cost of the land per the total floor area of a building. Thus the construction of skyscrapers is dictated by economics and results in skyscrapers in a certain part of a large city unless a [[building code]] restricts the height of buildings. Skyscrapers are rarely seen in small cities and they are characteristic of large cities, because of the critical importance of high land prices for the construction of skyscrapers. Usually only office, commercial and hotel users can afford the rents in the city center and thus most tenants of skyscrapers are of these classes. Some skyscrapers have been built in areas where the [[bedrock]] is near surface, because this makes constructing the [[foundation (engineering)|foundation]] cheaper, for example this is the case in [[Midtown Manhattan]] and [[Lower Manhattan]], in [[New York City]], [[United States]], but not in-between these two parts of the city.
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| Today, skyscrapers are an increasingly common sight where land is expensive, as in the centers of big cities, because they provide such a high ratio of rentable floor space per unit area of land.
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| <math>\text{Simple price of floor area (currency/m²)} = \frac{\text{price of land area (currency)}} {\text{total floor area (m²)}}</math>
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| One problem with skyscrapers is [[Parking lot|car parking]]. In the largest cities most people travel to work by public transport because of road congestion, but for slightly smaller cities a lot of parking spaces will be needed. [[Multi-storey car park]]s are impractical to build very tall, so a lot of land area would be needed.
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| ==Environmental impact==
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| {{unreferencedsect|date=February 2014}}
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| [[File:30 St Mary Axe - The Gherkin from Leadenhall St - Nov 2006.jpg|thumb|180px|[[30 St Mary Axe]] in London is an example of a modern environmentally friendly skyscraper.]]
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| The environmental impact of skyscrapers and whether instead of skyscrapers multiple smaller, lighter buildings would be more environmentally friendly or [[sustainability|sustainable]] is under debate. The concept of a skyscraper is a product of the [[Industrial society|industrialized age]], made possible by cheap [[fossil fuel]] derived energy and industrially refined raw materials such as [[steel]] and [[concrete]]. The construction of skyscrapers was enabled by [[steel frame]] construction that surpassed [[brick and mortar]] construction starting at the end of the 19th century and finally surpassing it in the 20th century together with [[reinforced concrete]] construction as the price of steel decreased and labour costs increased.
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| The amount of steel, concrete and glass needed to construct a single skyscraper is large, and these materials represent a great deal of [[embodied energy]]. Skyscrapers are thus energy intensive buildings, but skyscrapers have a long lifespan, for example the [[Empire State Building]] in [[New York City]], [[United States]] completed in 1931 and is still in active use. Skyscrapers have considerable mass, which means that they must be built on a sturdier foundation than would be required for shorter, lighter buildings. Building materials must also be lifted to the top of a skyscraper during construction, requiring more energy than would be necessary at lower heights. Furthermore, a skyscraper consumes a lot of electricity because [[potable]] and non-potable water have to be pumped to the highest occupied floors, skyscrapers are usually designed to be [[HVAC|mechanically ventilated]], elevators are generally used instead of stairs, and natural lighting cannot be utilized in rooms far from the windows and the windowless spaces such as elevators, bathrooms and stairwells.
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| Skyscrapers can be artificially lighted and the energy requirements can be covered by [[renewable energy]] or other electricity generation of low [[greenhouse gas]] emissions. Heating and cooling of skyscrapers can be efficient, because of centralized [[HVAC]] systems, heat radiation blocking [[window]]s and small surface area of the building. There is [[Leadership in Energy and Environmental Design]] (LEED) certification for skyscrapers. For example the Empire State Building received a gold Leadership in Energy and Environmental Design rating in September 2011 and the Empire State Building is the tallest LEED certified building in the United States, proving that skyscrapers can be environmentally friendly. Also the [[30 St Mary Axe]] in [[London]], the [[United Kingdom]] is an environmentally friendly skyscraper.
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| In the lower levels of a skyscraper a larger percentage of the building cross section must be devoted to the building structure and services than is required for lower buildings:
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| *More structure – because it must be stronger to support more floors above
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| *[[Skyscraper design and construction#The elevator conundrum|The elevator conundrum]] creates the need for more lift shafts—everyone comes in at the bottom and they all have to pass through the lower part of the building to get to the upper levels.
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| *[[Building services]]—power and water enter the building from below and have to pass through the lower levels to get to the upper levels.
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| In low-rise structures, the support rooms ([[chiller]]s, [[transformer]]s, [[boiler]]s, [[pump]]s and [[air handling unit]]s) can be put in basements or roof space—areas which have low rental value. There is, however, a limit to how far this plant can be located from the area it serves. The farther away it is the larger the risers for ducts and pipes from this plant to the floors they serve and the more floor area these risers take. In practice this means that in highrise buildings this plant is located on 'plant levels' at intervals up the building.
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| {{further|Bird-skyscraper collisions}}
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| == History of the tallest skyscrapers ==
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| {{Main|History of the tallest buildings in the world}}
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| At the beginning of the 20th century, New York City was a center for the [[Beaux-Arts architecture|Beaux-Arts architectural]] movement, attracting the talents of such great architects as [[Stanford White]] and [[Carrere and Hastings]]. As better construction and engineering technology became available as the century progressed, New York and Chicago became the focal point of the competition for the tallest building in the world. Each city's striking skyline has been composed of numerous and varied skyscrapers, many of which are icons of 20th-century architecture:
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| * The '''[[Flatiron Building]]''', designed by [[Daniel Hudson Burnham]] and standing 285 ft (87 m) high, was one of the tallest buildings in the city upon its completion in 1902, made possible by its steel skeleton. It was one of the first buildings designed with a steel framework, and to achieve this height with other construction methods of that time would have been very difficult. (The 1889 Tower Building, designed by [[Bradford Gilbert]] and considered by some to be New York's first skyscraper, may have been the first building to use a skeletal steel frame.)<ref>{{cite book|url=http://books.google.com/books?id=ODnnmcciMLgC&lpg=PP1&dq=The%20Epic%20of%20New%20York&pg=PA405#v=onepage&q&f=false |title=The Epic of New York City: A Narrative History |author=Edward Robb Ellis |pages=405–415 |year=2005 |publisher=Carroll & Graf publishers|isbn=0-7867-1436-0|accessdate=2011-06-05}}</ref> Actually [[Home Insurance Building]] in [[Chicago]], [[United States]] built in 1884 was the first building that had a skeletal frame. Subsequent buildings such as the '''[[Singer Building]]''', the '''[[Metropolitan Life Tower]]''' were higher still.
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| * The '''[[Woolworth Building]]''', a neo-Gothic "Cathedral of Commerce" overlooking City Hall, was designed by [[Cass Gilbert]]. At 792 feet (241 m), it became the world's tallest building upon its completion in 1913, an honor it retained until 1930, when it was overtaken by [[40 Wall Street]].
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| * That same year, the '''[[Chrysler Building]]''' took the lead as the tallest building in the world, scraping the sky at 1,046 feet (319 m).<ref>{{cite web|url=http://skyscraperpage.com/cities/?buildingID=83 |title=Chrysler Building. Quote: An exhibition in the building's lobby reports the height as 1046 |publisher=Skyscraperpage.com |accessdate=2011-06-05}}</ref> Designed by [[William Van Alen]], an [[Art Deco]] style masterpiece with an exterior crafted of brick,<ref>{{cite web|author=Emporis GmbH |url=http://www.emporis.com/en/wm/bu/?id=114867 |title=– Chrysler Building statistics |publisher=Emporis.com |accessdate=2011-06-05}}</ref> the Chrysler Building continues to be a favorite of New Yorkers to this day.<ref>{{cite web|url=http://favoritearchitecture.org/afa150.php |title=America's Favorite Architecture: Chrysler Building ranked 9th |publisher=Favoritearchitecture.org |accessdate=2011-06-05}}</ref>
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| * The '''[[Empire State Building]]''', the first building to have more than 100 floors (it has 102), was completed the following year. It was designed by [[Shreve, Lamb and Harmon]] in the contemporary Art Deco style. The tower takes its name from the [[List of U.S. state nicknames|nickname]] of [[New York State]]. Upon its completion in 1931 at 1,250 feet (381 m), it took the top spot as tallest building, and towered above all other buildings until 1972. The antenna mast added in 1951 brought pinnacle height to 1,472 feet (449 m), lowered in 1984 to 1,454 feet (443 m).<ref name="pollak">{{cite news|url=http://query.nytimes.com/gst/fullpage.html?res=9D03EEDD153FF930A15757C0A9609C8B63&scp=4&sq=%22empire%20state%20building%22%20height%201,454&st=cse|title=75 YEARS: F. Y. I.|last=Pollak |first=Michael|date=23 April 2006|work=The New York Times|accessdate=2009-10-31}}</ref>
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| * The '''[[World Trade Center]]''' officially reached full height in 1972, was completed in 1973, and consisted of two tall towers and several smaller buildings. For a short time, the first of the two towers was the world's tallest building. Upon completion, the towers stood for 28 years, until the <!--despite the dmy date ordering in this article, this event is better known worldwide as '911' or 'September 11'-->[[September 11 attacks]] destroyed the buildings in 2001. Various governmental entities, financial firms, and law firms called the towers home.
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| * The '''[[Willis Tower]]''' (formerly Sears Tower) was completed in 1974, one year after the World Trade Center, and surpassed it as the world's tallest building. It was the first building to employ the "[[Tube (structure)|bundled tube]]" structural system, designed by Fazlur Khan.<ref name=Banglapedia/> The building was not surpassed in height until the [[Petronas Towers]] were constructed in 1998, but remained the tallest in some categories until [[Burj Khalifa]] surpassed it in all categories in 2010. It is currently the tallest building in the United States, after [[One World Trade Center]] (2013), which was built to replace the destroyed towers.
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| Momentum in setting records passed from the United States to other nations with the opening of the '''[[Petronas Twin Towers]]''' in Kuala Lumpur, Malaysia, in 1998. The record for the world's tallest building has remained in Asia since the opening of '''[[Taipei 101]]''' in Taipei, Taiwan, in 2004. A number of architectural records, including those of the world's tallest building and tallest free-standing structure, moved to the Middle East with the opening of the '''[[Burj Khalifa]]''' in Dubai, United Arab Emirates.
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| This geographical transition is accompanied by a change in approach to skyscraper design. For much of the twentieth century large buildings took the form of simple geometrical shapes. This reflected the "international style" or [[Modern architecture|modernist]] philosophy shaped by [[Bauhaus]] architects early in the century. The last of these, the Willis Tower and World Trade Center towers in New York, erected in the 1970s, reflect the philosophy. Tastes shifted in the decade which followed, and new skyscrapers began to exhibit [[Postmodernism|postmodernist]] influences. This approach to design avails itself of historical elements, often adapted and re-interpreted, in creating technologically modern structures. The Petronas Twin Towers recall Asian [[pagoda]] architecture and Islamic geometric principles. Taipei 101 likewise reflects the [[pagoda]] tradition as it incorporates ancient [[Motif (visual arts)|motifs]] such as the [[Ruyi (scepter)|ruyi]] symbol. The Burj Khalifa draws inspiration from traditional [[Islamic art]]. Architects in recent years have sought to create structures that would not appear equally at home if set in any part of the world, but that reflect the culture thriving in the spot where they stand.
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| For current rankings of skyscrapers by height, see [[List of tallest buildings in the world]].
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| The following list measures height of the '''roof'''. The more common gauge is the '''highest architectural detail'''; such ranking would have included Petronas Towers, built in 1998. See [[List of tallest buildings in the world]] for details.
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| {| class="sortable wikitable"
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| !Built || Building || City || Country || colspan="2" style="text-align:center;"|Roof||Floors|| colspan="2" style="text-align:center;"|Pinnacle || Current status
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| |1870 || [[Equitable Life Building (New York City)|Equitable Life Building]] {{dubious|date=January 2012}} || [[New York City]] || United States || 142 ft||43 m|| 8 || || || Destroyed by fire in 1912
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| |1889 || [[Auditorium Building, Chicago|Auditorium Building]] || [[Chicago]] || United States ||269 ft||82 m||17 ||349 ft||106 m|| Standing
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| |1890 || [[New York World Building]] || New York City || United States ||309 ft||94 m||20 ||349 ft||106 m|| Demolished in 1955
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| |1894 || [[Manhattan Life Insurance Building]] || New York City || United States || 348 ft||106 m|| 18|||||| Demolished in 1963
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| |1895 || [[Milwaukee City Hall]] || [[Milwaukee]] || United States ||353 ft||108 m || 15 |||||| Standing
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| |1899 || [[Park Row Building]] || New York City || United States || 391 ft||119 m|| 30 |||||| Standing
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| |1901 || [[Philadelphia City Hall]] || [[Philadelphia]] || United States || 511 ft || 155.8 m || 9 || 548 ft||167 m|| Standing
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| |1908 || [[Singer Building]] || New York City || United States || 612 ft||187 m|| 47 |||||| Demolished in 1968
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| |1909 || [[Metropolitan Life Insurance Company Tower|Met Life Tower]]|| New York City || United States || 700 ft||213 m||50 |||||| Standing
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| |1913 || [[Woolworth Building]] || New York City || United States || 792 ft||241 m||57 |||||| Standing
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| |1930 || [[40 Wall Street]] || New York City || United States |||||| 70||927 ft||283 m|| Standing
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| |1930 || [[Chrysler Building]]|| New York City || United States || 927 ft||282.9 m||77 ||1,046 ft||319 m|| Standing
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| |1931 || [[Empire State Building]]|| New York City || United States || 1,250 ft||381 m||102 ||1,454 ft||443 m|| Standing
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| |1972 || [[World Trade Center]] (North tower) || New York City || United States || 1,368 ft||417 m||110 ||1,727 ft||526.3 m|| Destroyed in 2001
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| |1974 || [[Willis Tower]] (formerly Sears Tower) || Chicago || United States || 1,450 ft || 442 m|| 108 || 1,729 ft || 527 m || Standing
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| |2004 || [[Taipei 101]] || [[Taipei]] || Taiwan || 1,474 ft || 449 m || 101 || 1,671 ft || 509 m || Standing
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| |2008 || [[Shanghai World Financial Center]] || [[Shanghai]] || China || 1,599 ft || 487 m || 101 || 1,614 ft || 492 m || Standing
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| |2010 || [[Burj Khalifa]] || [[Dubai]] || United Arab Emirates || 2,717 ft || 828 m || 160 || 2,722 ft || 829.8 m || Standing
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| |}
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| ''Source: [http://www.emporis.com emporis.com]''
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| {{gallery|width=140|lines=6
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| |File:Taipei 101 2009 amk-EditMylius.jpg|[[Taipei 101]], formerly the world's tallest skyscraper, was the first to exceed the half-kilometer mark.
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| |File:World Trade Center, New York City - aerial view (March 2001).jpg|The iconic [[World Trade Center]] twin towers were [[September 11 attacks|destroyed in 2001]].
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| |File:Sears Tower ss.jpg|The [[Willis Tower]] in Chicago was the world's tallest building from 1974 to 1998, and is now the second tallest in the [[Western Hemisphere]].
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| |File:Petronas Panorama II.jpg|[[Petronas Twin Towers|The Petronas Twin Towers]] in Kuala Lumpur.
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| |File:IFC HKSAR.JPG|Tower 2 of the [[International Finance Centre]] in Hong Kong is one of the 20 [[List of tallest buildings in the world|tallest buildings in the world]].
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| }}
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| ==Future developments==
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| {{see also|Proposed tall buildings and structures}}
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| At the time Taipei 101 broke the half-km mark in height, it was already technically possible to build structures towering over a km above the ground.{{Citation needed|date=March 2012}} Proposals for such structures have been put forward, including the [[Kingdom Tower]] to be built in [[Jeddah]], Saudi Arabia<ref>{{cite web|url=http://www.arabnews.com/?page=6§ion=0&article=115403&d=13&m=10&y=2008 |title=Kingdom Tower |publisher=Arabnews.com |date=13 October 2008 |accessdate=2011-06-05}}</ref><ref>{{cite web|url=http://www.zawya.com/Story.cfm/sidZAWYA20081012131000/Prince%20Waleed%20To%20Build%201,000-Metre%20Tower%20in%20Jeddah |title=Zawya |publisher=Zawya |accessdate=2011-06-05}}</ref> and [[Mubarak al-Kabir Tower|Burj Mubarak Al Kabir]] in Kuwait. Kilometer-plus structures present architectural challenges that may eventually place them in a new architectural category.<ref name="Sadek">{{cite web|url=http://www.arabianbusiness.com/537095-reaching-for-the-stars|title=Reaching for the stars|last=Owainati|first=Sadek|date=3 November 2008|publisher=ArabianBusiness.com|accessdate=2008-11-15}}</ref>
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| The following skyscrapers, all contenders for being among the tallest in their city or region, are under construction and due to be completed in the next few years:
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| * Construction of the 115-floor, 660 meter tall '''[[Ping'an International Finance Center]]''' started in [[Shenzhen]], [[China]], 2010. It will be China's tallest building and the second-tallest building in the world.
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| * Construction of the 124-floor, 636 meter tall '''[[Wuhan Greenland Center]]''' started in late 2012 in [[Wuhan]], [[China]]. It will be the third tallest building in the world and the tallest structure in [[Hubei]] province.
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| *Construction of the '''[[Shanghai Tower]]''' started on 29 November 2008.<ref>{{cite web|last=Woollard |first=Deidre |url=http://www.luxist.com/2008/11/29/shanghai-tower-breaks-ground/ |title=Shanghai Tower Breaks Ground – Luxist |publisher=Luxist.com |date=29 November 2008 |accessdate=2011-06-05}}</ref> The tower will be {{Convert|632|m|ft|0|abbr=on}} high and have 127 floors.<ref>{{cite web |title=Shanghai Center main building will reach 632 meters |url=http://english.people.com.cn/90001/90776/6479288.html |publisher=People's Daily Online |date=18 August 2008 |accessdate=2008-08-19}}</ref><ref name=EIS>{{cite web |title=上海中心大厦项目环境影响报告书简本公示 |url=http://www.envir.gov.cn/info/2008/200808131.pdf |publisher=Envir.gov.cn |language=Chinese |format=PDF |date=13 August 2008 |accessdate=2008-08-14}}</ref> The building will feature a glass curtain wall and nine indoor gardens when it is completed in 2014.<ref name=emporis>{{cite web |url=http://www.emporis.com/en/wm/bu/?id=323473 |title=Shanghai Center |publisher=[[Emporis]] |accessdate=2008-05-17}}</ref><ref name=gardens>{{cite web |title=Tallest Chinese building features indoor gardens |url=http://www.shanghaidaily.com/sp/article/2008/200807/20080724/article_367915.htm |publisher=[[Shanghai Daily]] |date=24 July 2008 |accessdate=2008-08-09}}</ref>
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| * Construction of the 123-floor, 555 m tall '''[[Lotte World Premium Tower]]''' started in [[Seoul]], South Korea in 2012. It is set to become the tallest building in the OECD, with the tallest observation deck in the world.
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| *'''[[One World Trade Center]]''' is currently under construction in [[New York City]] and will be the tallest tower in the redevelopment of the site of the former [[World Trade Center]].<ref name=EmporisNY>{{cite web|author=Emporis GmbH |url=http://www.emporis.com/en/wm/bu/?id=freedomtower-newyorkcity-ny-usa |title=Freedom Tower, New York City / |publisher=Emporis.com |accessdate=2011-06-05}}</ref> Its pinnacle will reach a height of {{Convert|541.4|m|ft|0|abbr=on}},<ref name=EmporisNY/> a height (in feet) representing the year of the [[United States Declaration of Independence]].
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| *Construction of the 110-[[floor]], 510 m tall '''[[Busan Lotte World]]''', [[Busan]], South Korea, started in 2009. It is due for completion in 2016.
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| *Construction of the 93-floor, 509 m tall '''[[Federation Tower]]''' in [[Moscow]], Russia is set to become the tallest building in [[Europe]] when it is completed.
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| *Construction of the 102-[[floor]], 487 m tall '''[[151 Incheon Tower]]''' in [[Songdo International City]], [[Incheon]], South Korea, started in 2008, which will be the tallest twin towers in the world when it is completed in 2014.
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| * '''[[World One]]''' is a {{convert|442|m|ft|abbr=on}} tall residential skyscraper under construction in [[Mumbai]], [[India]]. It is located in Upper Worli of Mumbai on a 17.5 acre site. The project will cost INR 2,000 crore (US$380 million), be completed by 2014 and will have the world’s second tallest residential tower once completed. It will be rated as Leed Gold Certified building by the Green Building Council. World One is designed by Pei Cobb Freed and Partners and Leslie E. Robertson Associates.
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| * '''[[Gran Torre Santiago]]''' will be the tallest building in Latin America with 300 m (984 ft) to the top. Construction started in 2006 and is planned to finish in 2013. It is located in [[Chile]]´s Capital [[Santiago]] and is being developed by [[Cencosud]].
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| ==See also==
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| *[[Emporis Skyscraper Award]]
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| *[[Groundscraper]]
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| *[[List of cities with most skyscrapers]]
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| *[[List of tallest buildings and structures in the world]]
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| *[[List of tallest buildings in the world]]
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| *[[Seascraper]]
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| *[[Skyscraper design and construction]]
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| *[[Skyscraper Index]]
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| *[[Skyscraper Museum]] in NYC
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| *[[Skyscrapers in film]]
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| *[[Skyline]]
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| *[[Timeline of three tallest structures in the world]]
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| *[[Vertical farming]], "farmscrapers"
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| *[[World's littlest skyscraper]]
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| ==References==
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| {{Reflist|30em}}
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| == Further reading ==
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| *''Skyscrapers: Form and Function'', by David Bennett, Simon & Schuster, 1995.
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| * Landau, Sarah Bradford; Condit, Carl W., [http://books.google.com/books?id=zR1Get-mUU8C&printsec=frontcover ''Rise of the New York skyscraper, 1865–1913''], New Haven : Yale University Press, 1996. ISBN 0-300-06444-6
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| * Willis, Carol, ''Form Follows Finance: Skyscrapers and Skylines in New York and Chicago.'' Princeton Architectural Press, 1995. 224 P. ISBN 1-56898-044-2
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| ==External links==
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| {{Commons category|Skyscrapers|Skyscraper}}
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| *[http://www.skyscraper.org/ Skyscraper Museum]
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| *[http://www.tallestbuildingintheworld.com/ Tallest Building in the World]
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| *[http://www.skyscraperpage.com SkyscraperPage Technical information and diagrams]
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| *{{dmoz|Arts/Architecture/Building_Types/Skyscrapers|Skyscrapers}}
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| *[http://standards.phorio.com/?t=definition&code=6761770913 Skyscraper definition on Phorio Standards]
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| *[http://www.youtube.com/watch?v=97QqO2Mdi88 How Do You Make a Building Disappear?], [[New York Times]] video on skyscraper demolition
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| * [http://www.ctbuh.org/ Council on Tall Buildings and Urban Habitat]
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| {{TBSW}}
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| {{Developments}}
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| [[Category:Skyscrapers| ]]
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| [[Category:Structural engineering]]
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| [[Category:Structural system]]
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| [[Category:World Digital Library related]]
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| {{Link FA|he}}
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| {{Link FA|fy}}
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