Willis Tower vs Burj Khalifa

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The Willis Tower (formerly and informally: Sears Tower, its title until 2009) is a 110-story, 1,450-foot (442.1 m) skyscraper in Chicago. At completion in 1973, it surpassed the World Trade Center in New York City to become the tallest building in the world, a title that it held for nearly 25 years; it was also the tallest building in the Western Hemisphere for 41 years, before the new One World Trade Center surpassed it in 2013. While it held the title of'Tallest Office Building' before 2013, it dropped the title of'Tallest Man-Made Construction' after only 3 decades. The CN Tower in Toronto, which functions as a communications tower, took over the title in 1976. The Willis Tower is considered a seminal accomplishment for engineer Fazlur Rahman Khan. It is currently the third-tallest construction in the USA and the Western hemisphere -- and the 23rd-tallest in the world.

Annually, several million people visit its observation deck, the highest in the USA, which makes it one of Chicago's most popular tourist destinations. The arrangement was renamed in 2009 by the Willis Group as a term of its lease. As of April 2018, the building's largest tenant is United Airlines, which moved its corporate headquarters in 77 West Wacker Drive (then the United Building) in 2012, occupying around 20 flooring. Other major tenants include the building's namesake Willis Towers Watson and law firms Schiff Hardin and Seyfarth Shaw. Morgan Stanley plans to move into the construction in 2019 and become its fourth-largest tenant by 2020.

Source: Wikipedia

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The Burj Khalifa (Arabic: ??? ?????, Arabic pronunciation: [b?rd?? xa?li?fa]; pronounced English: ), known as the Burj Dubai prior to its inauguration in 2010, is a skyscraper in Dubai, United Arab Emirates. With a total height of 829.8 m (2,722 feet, just over half a mile) and a roof height (excluding antenna, but such as a 244 m spire) of 828 m (2,717 feet ), the Burj Khalifa has been the tallest structure and building in the world since its topping out in 2009 (preceded by Taipei 101).Construction of the Burj Khalifa began in 2004, with the exterior finished five decades later in 2009. The principal structure is reinforced concrete. The building was opened in 2010 as part of a new development called Downtown Dubai. It is designed to be the centrepiece of large-scale, mixed-use development. The decision to construct the building relies on the government's decision to diversify from an oil-based economy, and for Dubai to obtain international recognition. The building was originally named Burj Dubai but was renamed in honour of the ruler of Abu Dhabi and president of the United Arab Emirates, Khalifa bin Zayed Al Nahyan; Abu Dhabi and the UAE government lent Dubai money to pay its debts. The building broke numerous height records, including its designation as the tallest building in the world. Burj Khalifa was designed by Adrian Smith, of Skidmore, Owings & Merrill, whose firm designed the Willis Tower and One World Trade Center. Hyder Consulting was selected to be the supervising engineer with NORR Group Consultants International Limited selected to supervise the architecture of this project. The design is derived from the Islamic architecture of the region, such as in the Great Mosque of Samarra. The Y-shaped tripartite floor geometry is designed to optimize residential and hotel room. A buttressed central core and wings are utilised to support the elevation of the building. Although this design was derived from Tower Palace III, the Burj Khalifa's central center homes all vertical transport with the exception of egress stairs within each of the wings. The structure also offers a cladding system which is designed to withstand Dubai's hot summer temperatures. It comprises a total of 57 elevators and 8 escalators. At a particular stage in the architectural and engineering process, the original Emaar programmers experienced financial problems, and required more money and financial funding. Sheikh Khalifa, the ruler of the United Arab Emirates, granted monetary aid and financing, hence resulting in the changing of the name to'Burj Khalifa'. The concept of profitability derived from creating high density developments and malls around the landmark have proven effective. Its surrounding malls, hotels and condos in Downtown Dubai have generated the most revenue from the project as a whole, while the Burj Khalifa itself made little or no profit.Critical reception to Burj Khalifa has been generally positive, and the building has received many awards. However, there were numerous complaints regarding migrant workers from South Asia who were the key building labor force. These centered on low wages and the practice of confiscating passports until duties were complete. Several suicides were reported.

Source: Wikipedia