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  • By the end of the 20th century,

  • the race to build the world's tallest skyscraper grinded to a halt.

  • Each new contender was only slightly taller than the one before,

  • and architects were running out of ways to top their previous efforts.

  • But in 2004 construction began on a new building in Dubai,

  • promising a revolutionary design that would dwarf the competition.

  • In 2009, the 828-meter Burj Khalifa was complete,

  • surpassing the previous record-holder by over 60%.

  • So what innovations allowed for such a huge leap in height?

  • For most of architectural history, heavy building materials

  • made it difficult for tall buildings to support their own weight.

  • To compensate, taller structures had wider, thicker masonry at the base,

  • making them substantially more expensive.

  • The arrival of industrial steel in the early 20th century

  • helped buildings shed weight, and stretch to new heights.

  • But steel frames required intensive labor to produce,

  • often under poor working conditions.

  • And when they were finished,

  • these three dimensional grids took up huge amounts of space inside buildings.

  • Tall steel skyscrapers also had larger, less dense surfaces,

  • making them vulnerable to strong winds.

  • Architects designed various countermeasures

  • to prevent swaying and structural damage,

  • but to increase height further,

  • engineers would have to completely rethink how tall buildings were designed.

  • Enter the father of modern skyscrapers: Fazlur Rahman Khan.

  • This Bangladeshi-American engineer believed tall structures

  • should bear their weight where they were widest and most stableon the outside.

  • He proposed swapping an internal grid of steel beams

  • for a steel and concrete exoskeleton

  • that would make buildings more resilient to wind

  • while using far less heavy materials.

  • Khan developed this idea into what he called tubular designs.

  • These buildings had exterior steel frames that were braced with concrete

  • and connected to horizontal floor beams.

  • Tubular frames proved superior at absorbing and transferring

  • the force of wind to a building's foundation.

  • And since the exterior walls could bear the bulk of the load,

  • internal supporting columns could be removed to maximize space.

  • Following the 1960s, tubular design became the industry standard.

  • This new philosophy allowed for the construction

  • of taller, sturdier skyscrapers,

  • including many of the record holders for world's tallest building.

  • But planning the Burj Khalifa would take one more innovation.

  • In 2004, the late Fazlur Khan's longtime employers,

  • Skidmore, Owings & Merrill, completed the Tower Palace III in South Korea.

  • This building took Khan's exoskeleton design one step further,

  • with a central column supported by three protruding wings.

  • Each wing's weight carries the other two,

  • while the heavy concrete core acts as a support beam,

  • that also houses the building's elevators and mechanical infrastructure.

  • This design, called the buttressed core,

  • allowed the entire structure to work as a single load-bearing unit,

  • supporting the building's 73 stories.

  • SOM was confident the buttressed core could support a much taller building,

  • and they were determined to see how high they could go with their next project.

  • As only the second building to use this design,

  • the Burj Khalifa spans an unprecedented 163 floors.

  • To battle the monumental vertical and lateral forces,

  • the design strategically places the strongest, load-bearing areas

  • where the wind is also most powerful.

  • Additionally, the Y-shaped layout was specifically calibrated

  • to minimize local wind forces.

  • Every several floors, one of the wings recedes slightly,

  • forming a series of setbacks in a clockwise pattern.

  • This spiral shape disperses air currents,

  • transforming 240 kilometer per hour winds into harmless gusts.

  • Considering its height and unique design,

  • the Burj Khalifa was completed in a staggeringly short five year period.

  • However, this pace came at a great human cost.

  • The workforce consisted mostly of South Asian migrants,

  • who regularly endured shifts over 12 hours long

  • for a daily wage of roughly $10.

  • Those who tried to quit or return home had their paychecks and passports withheld

  • by the project's construction company.

  • These abusive conditions led to multiple protests,

  • in addition to at least one suicide, and one fatal accident reported on site.

  • In the years following the tower's completion,

  • the United Arab Emirates fell under harsh scrutiny

  • for failing to enforce worker protection laws.

  • Hopefully, future projects will prioritize the individuals

  • behind these engineering marvels over the buildings themselves.

By the end of the 20th century,

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世界最高的摩天大樓如何被建造的(How the world’s tallest skyscraper was built - Alex Gendler)

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    shuting1215 發佈於 2021 年 04 月 25 日
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