Question:
AKB48 (pronounced A.K.B. Forty-eight) are a Japanese idol girl group named after the Akihabara (Akiba for short) area in Tokyo, where the group's theater is located. The group has expanded since then to include over 130 members as of December 2015, aged from their early teens to their mid-20s. AKB48's producer, Yasushi Akimoto, wanted to form a girl group with its own theater (unlike pop groups performing occasional concerts and seen on television) and performing daily so fans could always see them live. This "idols you can meet" concept includes teams which can rotate performances and perform simultaneously at several events and "handshake" events, where fans can meet group members.
The group has publicized special events to choose the promotional and recording lineups for some of its singles. In 2009, the concept of senbatsu sosenkyo (Xuan Ba Zong Xuan Ju , "selection general election") was introduced, which allowed fans to vote their favorite members into the promotional line up or senbatsu (Xuan Ba , "selection") for one of their annual singles. Ballots are obtained by purchasing the group's latest "election single", or, alternatively, through the group's mobile app products and fan club subscriptions. Top vote getting members are heavily promoted, with the winner getting the centerpiece of the group's live performances of the single. The total pool of votes counted has exceeded three million votes for individual events since 2015. Fans have reportedly bought hundreds of copies of singles to vote for their favorite members. Another selection method, AKB48's rock-paper-scissors tournaments, was introduced in 2010 for the group's 19th single ("Chance no Junban") and has recurred as an annual event. Members of AKB48 and its sister groups compete in the knockout tournament to be part of the recording and promotional lineup for the group's next single, with participants wearing a variety of costumes. Starting with 2014, the tournament does not determine the promotional line up of a single anymore. Instead, the winner would debut as a soloist or, if she was already a soloist, would perform a solo concert. AKB48 has also used the general election scheme to determine set lists for an annual Request Hour (rikuesutoawa, rikuesuto awa) show. Other annual events include an AKB48 group only version of Kohaku Uta Gassen and the AKB group draft meeting (AKB48gurupu dorahutoHui Yi , AKB48 gurupu dorafuto kaigi), in which all teams from any of the sister groups chose new members from a pre-selected group of applicants.
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what was the single?

Answer:

Question:
Fazlur Rahman Khan (Bengali: phjlur rhmaan khaan, Fozlur Rohman Khan) (3 April 1929 - 27 March 1982) was a Bangladeshi-American structural engineer and architect, who initiated important structural systems for skyscrapers. Considered the "father of tubular designs" for high-rises, Khan was also a pioneer in computer-aided design (CAD). He was the designer of the Sears Tower, since renamed Willis Tower, the tallest building in the world from 1973 until 1998, and the 100-story John Hancock Center. Khan, more than any other individual, ushered in a renaissance in skyscraper construction during the second half of the 20th century.
Khan's central innovation in skyscraper design and construction was the idea of the "tube" structural system for tall buildings, including the framed tube, trussed tube, and bundled tube variants. His "tube concept", using all the exterior wall perimeter structure of a building to simulate a thin-walled tube, revolutionized tall building design. Most buildings over 40 stories constructed since the 1960s now use a tube design derived from Khan's structural engineering principles. Lateral loads (horizontal forces) such as wind forces, seismic forces, etc., begin to dominate the structural system and take on increasing importance in the overall building system as the building height increases. Wind forces become very substantial, and forces caused by earthquakes, etc. are important as well. The tubular designs resist such forces for tall buildings. Tube structures are stiff and have significant advantages over other framing systems. They not only make the buildings structurally stronger and more efficient, but also significantly reduce the structural material requirements. The reduction of material makes the buildings economically more efficient and reduces environmental impact. The tubular designs enable buildings to reach even greater heights. Tubular systems allow greater interior space and further enable buildings to take on various shapes, offering added freedom to architects. These new designs opened an economic door for contractors, engineers, architects, and investors, providing vast amounts of real estate space on minimal plots of land. Khan was among a group of engineers who encouraged a rebirth in skyscraper construction after a hiatus of over thirty years. The tubular systems have yet to reach their limit when it comes to height. Another important feature of the tubular systems is that buildings can be constructed using steel or reinforced concrete, or a composite of the two, to reach greater heights. Khan pioneered the use of lightweight concrete for high-rise buildings, at a time when reinforced concrete was used for mostly low-rise construction of only a few stories in height. Most of Khan's designs were conceived considering pre-fabrication and repetition of components so projects could be quickly built with minimal errors. The population explosion, starting with the baby boom of the 1950s, created widespread concern about the amount of available living space, which Khan solved by building upward. More than any other 20th-century engineer, Fazlur Rahman Khan made it possible for people to live and work in "cities in the sky." Mark Sarkisian (Director of Structural and Seismic Engineering at Skidmore, Owings & Merrill) said, "Khan was a visionary who transformed skyscrapers into sky cities while staying firmly grounded in the fundamentals of engineering."
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What other things can you tell me about his tube structural systems?

Answer:
Tubular systems allow greater interior space and further enable buildings to take on various shapes, offering added freedom to architects.