Architecture and design

The tower is designed by Skidmore, Owings and Merrill, which also designed the Willis Tower (formerly the Sears Tower) in Chicago, Illinois and the new One World Trade Center in New York City, among numerous other famous high-rises. The building resembles the bundled tube form of the Willis Tower, but is not a bundle tube structure. Its design is reminiscent of Frank Lloyd Wright's vision for The Illinois, a mile-high skyscraper designed for Chicago. According to Marshall Strabala, an SOM architect who worked on the building's design team, Burj Khalifa was designed based on the 73-floor Tower Palace Three, an all-residential building in Seoul, South Korea. In its early planning, Burj Khalifa was intended to be entirely residential.[34]
Subsequent to the original design by Skidmore, Owings and Merrill, Emaar Properties chose Hyder Consulting to be the supervising engineer.[39] Hyder was selected for its expertise in structural and MEP (mechanical, electrical and plumbing) engineering.[40] Hyder Consulting's role was to supervise construction, certify SOM's design, and be the engineer and architect of record to the UAE authorities.[39] Emaar Properties also engaged GHD,[41] an international multidisciplinary consulting firm, to act as an independent verification and testing authority for concrete and steelwork.
The design of Burj Khalifa is derived from patterning systems embodied in Islamic architecture.[24] 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.[24] The design architect, Adrian Smith, has said the triple-lobed footprint of the building was inspired by the flower Hymenocallis.[42] 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).[43]
To support the unprecedented height of the building, the engineers developed a new structural system called the buttressed core, which consists of a hexagonal core reinforced by three buttresses that form the ‘Y' shape. This structural system enables the building to support itself laterally and keeps it from twisting.[24]
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.[44]
More than 1,000 pieces of art will adorn the interiors of Burj Khalifa, while the residential lobby of Burj Khalifa will display the work of Jaume Plensa, featuring 196 bronze and brass alloy cymbals representing the 196 countries of the world.[45] The visitors in this lobby will be able to hear a distinct timbre as the cymbals, plated with 18-carat gold, are struck by dripping water, intended to mimic the sound of water falling on leaves.[46]
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.[47] 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.[44]
A 304 room Armani Hotel, the first of four by Armani, occupies 15 of the lower 39 floors.[48][2] The hotel was supposed to open on 18 March 2010[49][50] but after several delays the hotel finally opened the public on 27 April 2010.[51] The corporate suites and offices were also supposed to open from March onwards[52] but the hotel and observation deck remain the only parts of the building which are open.
The sky lobbies on the 43rd and 76th floors will house swimming pools.[53] 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.[53][54]
Burj Khalifa is expected to hold up to 35,000 people at any one time.[24][55] A total of 57 elevators and 8 escalators are installed.[44] 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).[24][56] Engineers had considered installing the world's first triple-deck elevators, but the final design calls for double-deck elevators.[27] The double-deck elevators are equipped with entertainment features such as LCD displays to serve visitors during their travel to the observation deck.[57] The building has 2,909 stairs from the ground floor to the 160th floor.[58]
The graphic design identity work for Burj Khalifa is the responsibility of Brash Brands, who are based in Dubai. Design of the global launch events, communications, and visitors centers[59] for Burj Khalifa have also been created by Brash Brands as well as the roadshow exhibition for the Armani Residences, which are part of the Armani Hotel within Burj Khalifa, which toured Milan, London, Jeddah, Moscow and Delhi

Water supply system

The Burj Khalifa's water system supplies an average of 946,000 l (250,000 USgal) of water per day.[24]
At the peak cooling times, the tower requires cooling equivalent to that provided by 10,000 t (22,000,000 lb) of melting ice in one day. The building has a condensate collection system, which uses the hot and humid outside air, combined with the cooling requirements of the building and 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

Maintenance
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.[61] 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.[44][62]
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