Burj Khalifa known as Burj Dubai prior to its inauguration, is a skyscraper in Dubai, United Arab Emirates, and is currently the tallest structure ever built, at 828 m (2,717 ft). Construction began on 21 September 2004, with the exterior of the structure completed on 1 October 2009. The building officially opened on 4 January 2010, and is part of the new 2 km2 (490-acre) flagship development called Downtown Dubai at the 'First Interchange' along Sheikh Zayed Road, near Dubai's main business district.
The tower's architecture and engineering were performed by Skidmore, Owings and Merrill of Chicago, with Adrian Smith as chief architect, and Bill Baker as chief structural engineer. The primary contractor was Samsung C&T of South Korea.
The total cost for the project was about US $1.5 billion; and for the entire "Downtown Dubai" development, US $20 billion. In March 2009, Mohamed Ali Alabbar, chairman of the project's developer, Emaar Properties, said office space pricing at Burj Khalifa reached US $4,000 per sq ft (over US $43,000 per m²) and the Armani Residences, also in Burj Khalifa, sold for US $3,500 per sq ft (over US $37,500 per m²).
The project's completion coincided with the global financial crisis of 2007–2010, and with vast overbuilding in the country, led to high vacancies and foreclosures. With Dubai mired in debt from its huge ambitions, the government was forced to seek multibillion dollar bailouts from its oil rich neighbor Abu Dhabi. Subsequently, in a surprise move at its opening ceremony, the tower was renamed Burj Khalifa, said to honour the UAE President Khalifa bin Zayed Al Nahyan for his crucial support.
Due to the slumping demand in Dubai's property market, the rents in the Burj Khalifa plummeted 40% some ten months after its opening. Out of 900 apartments in the tower around 825 were still empty at that time.
Burj Khalifa has been designed to be the centrepiece of a large-scale, mixed-use development that would include 30,000 homes, nine hotels such as The Address Downtown Dubai, 3 hectares (7.4 acres) of parkland, at least 19 residential towers, the Dubai Mall, and the 12-hectare (30-acre) man-made Burj Khalifa Lake.
The building has returned the location of Earth's tallest freestanding structure to the Middle East where the Great Pyramid of Giza claimed this achievement for almost four millennia before being surpassed in 1311 by Lincoln Cathedral in England.
The decision to build Burj Khalifa is reportedly based on the government's decision to diversify from an oil based economy to one that is service and tourism based. According to officials, it is necessary for projects like Burj Khalifa to be built in the city to garner more international recognition, and hence investment. "He (Sheikh Mohammed bin Rashid Al Maktoum) wanted to put Dubai on the map with something really sensational," said Jacqui Josephson, a tourism and VIP delegations executive at Nakheel Properties.
There are unconfirmed reports of several planned height increases since its inception. Originally proposed as a virtual clone of the 560 m (1,837 ft) Grollo Tower proposal for Melbourne, Australia's Docklands waterfront development, the tower was redesigned by Skidmore, Owings and Merrill (SOM). Marshall Strabala, an SOM architect who worked on the project until 2006, in late 2008 said that Burj Khalifa was designed to be 808 m (2,651 ft) tall.
The design of Burj Khalifa is derived from patterning systems embodied in Islamic architecture. According to the structural engineer, Bill Baker of SOM, the building's design incorporates cultural and historical elements particular to the region. The Y-shaped plan is ideal for residential and hotel usage, with the wings allowing maximum outward views and inward natural light. The design architect, Adrian Smith, has said the triple lobed footprint of the building was inspired by the flower Hymenocallis. The tower is composed of three elements arranged around a central core. As the tower rises from the flat desert base, setbacks occur at each element in an upward spiralling pattern, decreasing the cross section of the tower as it reaches toward the sky. There are 27 terraces in Burj Khalifa. At the top, the central core emerges and is sculpted to form a finishing spire. A Y-shaped floor plan maximizes views of the Persian Gulf. Viewed from above or from the base, the form also evokes the onion domes of Islamic architecture. During the design process, engineers rotated the building 120 degrees from its original layout to reduce stress from prevailing winds. At its tallest point, the tower sways a total of 1.5 m (4.9 ft).
The spire of Burj Khalifa is composed of more than 4,000 tonnes (4,400 ST; 3,900 LT) of structural steel. The central pinnacle pipe weighing 350 tonnes (390 ST; 340 LT) was constructed from inside the building and jacked to its full height of over 200 m (660 ft) using a strand jack system. The spire also houses communications equipment.
The exterior cladding of Burj Khalifa consists of 142,000 m2 (1,528,000 sq ft) of reflective glazing, and aluminium and textured stainless steel spandrel panels with vertical tubular fins. The cladding system is designed to withstand Dubai's extreme summer temperatures. Additionally, the exterior temperature at the top of the building is thought to be 6°C (11°F) cooler than at its base. Over 26,000 glass panels were used in the exterior cladding of Burj Khalifa. Over 300 cladding specialists from China were brought in for the cladding work on the tower.
The sky lobbies on the 43rd and 76th floors will house swimming pools. Floors through to 108 will have 900 private residential apartments (which, according to the developer, sold out within eight hours of being on the market). An outdoor zero-entry swimming pool will be located on the 76th floor of the tower. Corporate offices and suites fill most of the remaining floors, except for a 122nd, 123rd and 124th floor where the At.mosphere restaurant, sky lobby and an indoor and outdoor observation deck is located respectively. Burj Khalifa will receive its first residents from February 2010. They will be among the first of 25,000 people who will live there.
Burj Khalifa is expected to hold up to 35,000 people at any one time. A total of 57 elevators and 8 escalators are installed. The elevators have a capacity of 12 to 14 people per cabin, the fastest rising and descending at up to 18 m/s (59 ft/s). Engineers had considered installing the world's first triple-deck elevators, but the final design calls for double-deck elevators. The double-deck elevators are equipped with entertainment features such as LCD displays to serve visitors during their travel to the observation deck. The building has 2,909 stairs from the ground floor to the 160th floor.
The Burj Khalifa's water system supplies an average of 946,000 l (250,000 USgal) of water per day through 100 km (62 mi) of pipes. An additional 213 km (132 mi) of piping serves the fire emergency system, and 34 km (21 mi) supplies chilled water for the air conditioning system.
The air conditioning system draws air from the upper floors where the air is cooler and cleaner than on the ground. At peak cooling times, the tower's cooling is equivalent to that provided by 13,000 t (29,000,000 lb) of melting ice in one day. The condensate collection system, which uses the hot and humid outside air, combined with the cooling requirements of the building, results in a significant amount of condensation of moisture from the air. The condensed water is collected and drained into a holding tank located in the basement car park, this water is then pumped into the site irrigation system for use on the Burj Khalifa park.
To wash the 24,348 windows, a horizontal track has been installed on the exterior of Burj Khalifa at levels 40, 73 and 109. Each track holds a 1,500 kg (3,300 lb) bucket machine which moves horizontally and then vertically using heavy cables. Above level 109, up to tier 27 traditional cradles from davits are used. The top of the spire, however, is reserved for specialist window cleaners, who brave the heights and high winds dangling by ropes to clean and inspect the top of the pinnacle. Under normal conditions, when all building maintenance units will be operational, it will take 36 workers three to four months to clean the entire exterior facade.
Unmanned machines will clean the top 27 additional tiers and the glass spire. The cleaning system was developed in Melbourne, Australia at a cost of A$8 million.
Burj Khalifa is surrounded by an 11 ha (27-acre) park designed by landscape architects SWA Group. The design of the park is also inspired by the core design concepts of Burj Khalifa which is based on the symmetries of the desert flower, Hymenocallis. The park has six water features, gardens, palm lined walkways, and flowering trees. At the centre of the park and the base of Burj Khalifa is the water room, which is a series of pools and water jet fountains. In addition the railing, benches and signs incorporate images of Burj Khalifa and the Hymenocallis flower.
The plants and the shrubbery will be watered by the buildings's condensation collection system that uses water from the cooling system. The system will provide 68,000,000 L (15,000,000 imp gal) annually. WET designers, who also developed the Dubai Fountain, developed the park's six water features.
The primary structural system of Burj Khalifa is reinforced concrete. Over 45,000 m3 (58,900 cu yd) of concrete, weighing more than 110,000 tonnes (120,000 ST; 110,000 LT) were used to construct the concrete and steel foundation, which features 192 piles; each pile is 1.5 metre diameter x 43 m long, buried more than 50 m (164 ft) deep. Burj Khalifa's construction used 330,000 m3 (431,600 cu yd) of concrete and 55,000 tonnes (61,000 ST; 54,000 LT) of steel rebar, and construction took 22 million man-hours. A high density, low permeability concrete was used in the foundations of Burj Khalifa. A cathodic protection system under the mat is used to minimize any detrimental effects from corrosive chemicals in local ground water. In May 2008 concrete was pumped to a then world record delivery height of 606 m (1,988 ft), the 156th floor. Three tower cranes were used during construction of the uppermost levels, each capable of lifting a 25-tonne load. The remaining structure above is constructed of lighter steel.
Burj Khalifa is highly compartmentalised. Pressurized, air-conditioned refuge floors are located approximately every 35 floors where people can shelter on their long walk down to safety in case of an emergency or fire.
Special mixes of concrete are made to withstand the extreme pressures of the massive building weight; as is typical with reinforced concrete construction, each batch of concrete used was tested to ensure it could withstand certain pressures. CTLGroup, working for SOM, conducted the creep and shrinkage testing critical for the structural analysis of the building.
The consistency of the concrete used in the project was essential. It was difficult to create a concrete that could withstand both the thousands of tonnes bearing down on it and Persian Gulf temperatures that can reach 50 °C (122 °F). To combat this problem, the concrete was not poured during the day. Instead, during the summer months ice was added to the mixture and it was poured at night when the air is cooler and the humidity is higher. A cooler concrete mixture cures evenly throughout and is therefore less likely to set too quickly and crack. Any significant cracks could have put the entire project in jeopardy.
The unique design and engineering challenges of building Burj Khalifa have been featured in a number of television documentaries, including the Big, Bigger, Biggest series on the National Geographic and Five channels, and the Mega Builders series on the Discovery Channel.
In June 2010, Burj Khalifa was the recipient of the 2010 Best Tall Building Middle East & Africa award by the Council on Tall Buildings and Urban Habitat. On 28 September 2010 Burj Khalifa won the award for best project of year at the Middle East Architect Awards 2010.
The Council on Tall Buildings and Urban Habitat bestowed a new award for Burj Khalifa at its annual “Best Tall Buildings Awards Ceremony” on 25 October 2010 when Burj Khalifa honored as first recipient of CTBUH’s new Tall Building “Global Icon” Award. According to CTBUH the new “Global Icon” award recognizes those very special supertall skyscrapers that make a profound impact, not only on the local or regional context, but on the genre of tall buildings globally. Which is innovative in planning, design and execution, the building must have influenced and reshaped the field of tall building architecture, engineering, and urban planning. It is intended that the award will only be conferred on an occasional basis, when merited by an exceptional project perhaps every ten or fifteen years.
Burj Khalifa was built primarily by workers from South Asia. On 17 June 2008, there were 7,500 skilled workers employed at the construction site. Press reports indicated in 2006 that skilled carpenters at the site earned UK£4.34 a day, and labourers earned UK£2.84. According to a BBC investigation and a Human Rights Watch report, the workers were housed in abysmal conditions, their pay was often withheld, their passports were confiscated by their employers, and they were working in hazardous conditions that resulted in an apparently high number of deaths and injuries on site. During the building of the Burj Khalifa tower only one construction-related death was reported. However workplace injury and fatality in the UAE are "poorly documented".
On 21 March 2006, about 2,500 workers, who were upset over buses that were delayed for the end of their shifts, protested, damaging cars, offices, computers, and construction equipment. A Dubai Interior Ministry official said the rioters caused almost UK£500,000 in damage. Most of the workers involved in the riot returned the following day but refused to work.
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