- May 26, 2017 -
Dubai project ---Burj Khalifa Tower
The Burj Khalifa (Arabic: برج خليفة, Arabic for "Khalifa Tower"; pronounced English /ˈbɜːrdʒ kəˈliːfə/), known as the Burj Dubai before its inauguration, is a megatall skyscraper in Dubai, United Arab Emirates. With a total height of 829.8 m (2,722 ft) including the antenna and a roof height of 828 m (2,717 ft), the Burj Khalifa is currently the tallest structure in the world since topping out in late 2008.
The primary structure is reinforced concrete. Putzmeister created a new, super high-pressure trailer concrete pump, the BSA 14000 SHP-D, for this project. Burj Khalifa's construction used 330,000 m3 (431,600 cu yd) of concrete and 55,000 tonnes (61,000 short tons; 54,000 long tons) of steel rebar, and construction took 22 million man-hours. In May 2008 Putzmeister pumped concrete with more than 21 MPA ultimate compressive strength of gravel that would surpass the 600 meters weight of the effective area of each column from the foundation to the next fourth level, and the rest is by metal columns jacketed or covered with concreted 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.
Over 45,000 m3 (58,900 cu yd) of concrete, weighing more than 110,000 tonnes (120,000 short tons; 110,000 long tons) 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. The foundation is designed to support the total building weight of approximately 450,000 tonnes (500,000 short tons; 440,000 long tons). This weight is then divided by the compressive strength of concrete of which is 30 MPa which yield a 450 sq.meters of vertical normal effective area which then yield to a 12 meters by 12 meters dimensions.A cathodic protection system is in place under the concrete to neutralize the groundwater and prevent corrosion.
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.