Gratacèl
Un gratacèl (var. gratacèu, gratacial, grataciau) es un immòble plan naut e que se pòt abitar de longa. A mai existiscan pas de definicions oficialas, en general se pren coma critèri una nautor mininimala d'aperaquí 150 mètres per designar aqueste edifici coma un gratacèl. D'autres critèris coma la forma o l'aparença pòdon de segur afectar aquesta qualificacion de gratacèl. Se ditz que la vila de Chicago (Estats Units d'America) es lo brèç dels gratacèls.

Lo mot gratacèl, revirada de l'anglés skyscraper (sky es 'cèl' e to scrape 'gratar') s'apliquèt d'en primièr a d'edificis d'aquesta mena quand se tancava lo sègle XIX, mot que marcava l'estonament de las gents en veire d'immòbles tan nauts se sarrar del cèl a Chicago e a Nòva York. La definicion estructurala d'aqueste mot gratacèl foguèt refinada puèi pels istorians de l'arquitectura, en se basar sul desvolopament de las tecnicas d'engenheriá de las annadas 1880 que avián permés construccion d'immòbles nauts de fòrça nivèls. Aquela definicion s'apiejava sus l'ossamenta d'acièr—en oposicion a las construccions mai tradicionalas de pèira, qu'avián passat son limit practic en 1891 amb l'Immòble Monadnock de Chicago. Philadelphia's City Hall, terminat en 1901, still holds claim as the world's tallest load-bearing masonry estructura.  L'estructura d'acièr desvolopada en stages of increasing self-sufficiency, with several buildings a Chicago e Nòva York advancing the tecnologia que permetèt a l'ossamenta d'acièr de portar un immòble soleta. Uèi, pasmens, un nombre bèl dels gratacèls mai nauts son bastits mai o mens completament amb de reinforced concrete. Als Estats Units uèi, es una convencion loose d'establir lo limit minimal de çò qu'es un gratacèl a 150 mètres. Endacòm mai, pr'aquò, d'eficis mai basses pòdon èsser denominats gratacèls, mai que mai se domina de sa nautor tota l'environa. En consequéncia, lo fach de dire d'un edifici qu'es un gratacèl en general, mas pas totjorn, implicarà d'orguèlh e achievement.

A l'origina, gratacèl èra un nautical term per se referir a un tall mast o vela d'un sailing ship. Un gratacèl que se quilha ensús de 300 mètres es sonat d'unes còps que i a supertall (supergrand).

Lo tèrme, d'unes còps que i a arbitrari gratacèl se deuriá pas confondre amb lo tèrme un brin mens arbitrari highrise, definit per l'Emporis Data Committee coma "un edifici que mesura 35 mètres (115 feet) o mai en nautor, e qu'es devesit a d'intervals regulars en superfícias ocupablas" . Totes los gratacèls son de highrises, mas sonque los highrises mai nauts son de gratacèls. Lo critèri d'abitabilitat es l'element que dissepara los gratacèls de las torres e masts. D'unes structural engineers define a highrise coma tota mena de construccion verticala for which vent es un factor mai significant load factor que lo pes. Cal remarcar qu'aqueste critèri conven pas sonque als highrises mas tanben a d'autras estructuras elevadas, coma las torres.

Istòria 
Las evolucions essencialas pel desvolopament dels gratacèls modèrnes foguèron l'acièr, lo veire, lo reinforced concrete, las pompas d'aiga, e los ascensors. Fins al sègle XIX, las construccions de mai de sièis nivèls èron escassas. 
Los escalièrs tròp longs èran pas gaire practics e una empacha de las pesugas pels abitants, la pression d'aiga èra en general insufisenta per alimentar en aiga correnta a mai de 15 mètres (50 feet). Pasmens, malgrat aquesta manca de sanitation, high rise housing dates back a las annadas 1600 dins d'unes endreches. Los romans fabricavan de apartment buildings sometimes nauts de 7 o 8 nivèls. Aqueles edificis èran inestables e dirty and often caught fuòc per encausa de la manca d'atencion dels abitants. A Edimborg, en Escòcia per exemple, the defensive city wall defined the boundaries de la vila. With limited land area for development los ostals increased in height. Buildings de 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 d'Edimborg particularament dins los 'Wynds' e 'Closes' just off the Royal Mile.

L'immòble d'ossamenta de fèrre mai anciana del mond es The Flaxmill (tanben conegut localament coma lo "Maltings") a Shrewsbury, Anglatèrra. Bastit en 1797, se considera qu'es l'"aujòl dels gratacèls” per encausa a sa combinason ignifuga de colomnas cast iron e cast iron beams developed into the modern steel frame que faguèt possibles los gratacèls modèrnes. It unfortunately lies derelict e a mestièr much investiment to keep it standing. Lo 31 de març de 2005, foguèt anonciat que English Heritage comprariá the Flaxmill, so that it could be redeveloped.

Lo primièr gratacèl èra lo Home Insurance Building de dètz nivèls a Chicago, bastit en 1884–1885. Encara que sa nautor siá pas considerada inabituala o vertadièrament impressionanta uèi, l'arquitècte, Major William Le Baron Jenney, creèt la primièra load-carrying structural frame. In this building, a steel frame supported the entire weight of the walls instead of the walls themselves carrying the weight of the building which was the usual method. This development portèt a la the "Chicago skeleton" form of construction. After Jenney's accomplishment the sky was truly the limit so far as building was concerned. 

Sullivan's Wainwright Building building a St. Louis, 1890, was the first steel frame building with soaring vertical bands to emphasize the height of the building, e es, doncas, considerat per d'unes coma lo primièr vertadièr gratacèl.

Surprisingly for some, lo Reialme Unit aguèt una part bona de gratacèls d'ora. The first building to fit the engineering definition meanwhile was the then l'ostalariá mai granda del mond, the Grand Midland Hotel, conegut ara jol nom de St Pancras Chambers a Londres, acabat en 1873 with a clock tower 82 metres (269 feet) de nautor. The 12-floor Shell Mex House de Londres, at 58 metres (190 feet), foguèt acabat una annada aprèp the Home Insurance Building and managed to beat it in both height and floor count. 1877 saw the opening of the Gothic revival style Manchester Town Hall by Alfred Waterhouse. Its 87-metre-high clock and bell tower dominated that city's skyline for almost a sègle.

La part màger dels gratacèls early emerged in the land-strapped areas de Chicago, Londres, e de Nòva York cap a la fin del sègle XIX. Los constructors de Londres se trobèron lèu amb de limits de nautor per encausa d'una complaint de la Reina Victoria, rules that contunhèron d'existir amb qualques excepcions fins a las annadas 1950s; concerns about aesthetics e la seguretat contra lo fuòc had likewise hampered lo desvolopament dels gratacèls dins tota l'Euròpa continentala pendent la primièra partida del sègle vint (with the notable exceptions of the 26-storey KBC Tower in Antwerp, Belgium, built in 1932, and the 31-storey Torre Piacentini in Gènoa, Italy, built in 1940). After an early competicion between New York City e Chicago for the world's tallest building, New York took a firm lead by 1895 with the completion of the American Surety Building. Developers in Chicago also found themselves hampered by laws limitavan la nautor a aperaquí 40 nivèls, leaving Nòva York to hold lo títol de tallest building pendent fòrça annadas. New York City developers then competed among themselves, with successively taller buildings claiming the title of "world's tallest" in the 1920s and early 1930s, culminating amb l'acabament del Chrysler Building in 1930 and the Empire State Building in 1931, the world's tallest building pendent quaranta ans.  A partir de las annadas 1930s, los gratacèls comencèron d'aparéisser en America Latina (São Paulo, Buenos Aires, Mexico City) e en Asia (Shanghai, Hong Kong).

Immediatament aprèp la Segonda Guèrra Mondiala, l'Union Sovietica planned eight massive gratacèls sonats "Stalin Towers" per Moscòu; seven of these were eventually built. The rest of Euròpa also began dapasset a permetre de gratacèls, starting with Madrid in Espanha durant las annadas 1950. Fin finala, los gratacèls comencèron tanben d'aparéisser en Africa, the Middle East e en Oceania (essencialament en Austràlia) tre la fin de las annadas 1950 e la debuta de las 1960.

Uèi encara, malgrat la pèrdia de las torres del World Trade Center, e the relatively slow pace of new construccions novèlas, no vila dins lo mond entièr has more completed individual free-standing buildings over 492 ft. (150 m) than New York City, with 197. Hong Kong comes in with the most in the world (221), if one counts individually the multiple towers that rise from a common podium (like Emporis does), as in buildings that rise several stories as one structure, before splitting into two or more columns of floors. If Hong Kong's multiple-skyscraper complexes are treated as a single skyscraper, Hong Kong would certainly have less skyscrapers over 492 ft. However, this number is likely to continue to increase rapidly, due to a prolonged highrise building boom in Hong Kong. Chicago's skyline was not allowed to grow until the height limits were relaxed in 1960; over the next fifteen years, many towers were built, including the massive 442-meter (1,451-foot) Sears Tower, leading to its current number of 90 buildings over 492 ft. Chicago is currently undergoing an epic construction boom that will greatly add to the city's already magnificent skyline. Since 2000, at least 40 buildings at a minimum of 50 stories high have been built.  400 North Lake Shore Drive, Trump International Hotel and Tower (Chicago), Waterview Tower, Mandarin Oriental Tower, 29-39 South LaSalle, Park Michigan, and Acqua are some of the more intriguing projects currently underway in the city that invented the skyscraper. This construction boom will surely boost the number of skyscrapers in Chicago, and Chicago will likely be the third city in the world to have more than 100- 492 ft. skyscrapers. Chicago, Hong Kong, and New York City, other wise known as the "the big three," are recognized in most architectural circles as having the most compelling skylines in the world. Other large cities which are currently experiencing major building booms in skyscrapers include Shanghai in China and Dubai in the United Arab Emirates.

Uèi, los gratacèls son a venir un increasingly common sight where land is scarce, as dins los centres de las grandas vilas, because of the high ratio of rentable floor space per area of land. Skyscrapers, like temples and palaces in the past, are considered the ultimate symbols of a city's economic power which is exemplified by the rise of the Asian economy and skyline.

Istòria dels gratacèls mai nauts 

Per aver una classificacion dels gratacèls per nautor, veire Lista dels gratacèls.

Aquesta lista mesura la talha fins al teulat. The more common gauge is the highest architectural detail; such ranking would have included Petronas Towers, built in 1998. Veire la lista dels gratacèls per obtenir mai de detalhs.

Source: emporis.com

Futur 
Per ara la construccion del Burj Dubai es a se far a Dubai. Sa nautor exacta futura es gardada secretament, pasmens se pensa que deuriá arribar a almens  800 m high, making it the tallest building in the world. Lo Burj Dubai se deu acabar en 2008.

Vejatz tanben

Ligams extèrnes 

 Gratacèl
 Skyscraper Museum
 SkyscraperPage - Technical information and diagrams
 SkyscraperCity - Largest forum for urbanity. City portals with some technical information
 Emporis Buildings
 All About Skyscrapers

Autres sits
 Fòtos istoricas de gratacèls
 SkyScrapers.org - Contains High Resolution skyscraper illustrations
 Fòtos de la construccion de Burj Dubai (lo gratacèl que serà mai naut en 2008)
 City, Urban and Skyscraper Forum
  Urbanity.es
 
 SkyscraperModels.us
 SkyscraperNews (UK only)
 Reflections of a City
 Skyscraper 1880s "skyscraper" citations from word researcher Barry Popik.
 Skyscraperlife