“一到夜晚 摩天楼隐约地出现在云烟和众星中
“By night the skyscraper looms in the smoke and the stars
其灵魂也会显现出来“——卡尔·桑德堡
and has a soul.” – Carl Sandburg
1956年 建筑师弗兰克·劳埃德·赖特
In 1956, architect Frank Lloyd Wright
提议兴建一座一英里高的摩天楼
proposed a mile-high skyscraper.
它将成为世界上最高的建筑
It was going to be the world’s tallest building,
其高度是埃菲尔铁塔的5倍
by a lot — five times as high as the Eiffel Tower.
但很多评论者却嘲笑他
But many critics laughed at the architect,
认为人们等电梯就要花好几个小时
arguing that people would have to wait hours for an elevator,
更糟的是 这栋楼会因为自身重量而坍塌
or worse, that the tower would collapse under its own weight.
大多数工程师表示同意
Most engineers agreed,
所以 尽管这一提议被大肆宣传
and despite the publicity around the proposal,
这座巨楼从未被真正建成
the titanic tower was never built.
而如今 世界上建起了越来越高的建筑
But today, bigger and bigger buildings are going up around the world.
有企业甚至计划兴建超过一千米高的摩天楼
Firms are even planning skyscrapers more than a kilometer tall,
比如 沙特阿拉伯的吉达塔
like the Jeddah Tower in Saudi Arabia,
其高度是埃菲尔铁塔的三倍
three times the size of the Eiffel Tower.
再过不久 莱特的一英里高楼可能成真
Very soon, Wright’s mile-high miracle may be a reality.
那么 究竟是什么
So what exactly was stopping us
使我们在70年前无法兴建这些巨型建筑
from building these megastructures 70 years ago,
现在又如何建起一英里的高楼呢？
and how do we build something a mile high today?
在每一个建设项目中
In any construction project,
建筑的每一层楼
each story of the structure needs to be
都要能够支撑上面的楼层
able to support the stories on top of it.
建筑越高
The higher we build,
高楼层施加在低楼层上的重力就越大
the higher the gravitational pressure from the upper stories on the lower ones.
长久以来 建筑的形状受到了这一原理的限制
This principle has long dictated the shape of our buildings,
所以古代建筑师才会喜欢建金字塔
leading ancient architects to favor pyramids
因为它们地基较宽 所支撑的高楼层也较轻
with wide foundations that support lighter upper levels.
但是这样的建法并不适用于城市
But this solution doesn’t quite translate to a city skyline–
因为如此高的金字塔要有约1.5英里宽
a pyramid that tall would be roughly one-and-a-half miles wide,
市中心很难容纳得下它
tough to squeeze into a city center.
幸好 有了混凝土这种坚固的材料
Fortunately, strong materials like concrete
建筑就不必建成这种不切实际的形状了
can avoid this impractical shape.
现代的混凝土会加入钢筋 为混凝土加固
And modern concrete blends are reinforced with steel-fibers for strength
还会加入减水剂 以防产生裂痕
and water-reducing polymers to prevent cracking.
世界上最高大楼是迪拜的哈利法塔
The concrete in the world’s tallest tower, Dubai’s Burj Khalifa,
它的混凝土能承受每平方米8千吨的压力
can withstand about 8,000 tons of pressure per square meter–
这相等于1200多只非洲象的重量
the weight of over 1,200 African elephants!
当然 就算一座建筑能够支撑自己
Of course, even if a building supports itself,
它还是需要有地表的支撑
it still needs support from the ground.
没有地基 这么重的建筑物
Without a foundation, buildings this heavy
就会沉下 倾倒或者倾斜
would sink, fall, or lean over.
为了避免这座约50万吨重的大楼下沉
To prevent the roughly half a million ton tower from sinking,
192条钢筋混凝土基桩
192 concrete and steel supports called piles
被钻到地下50多米深
were buried over 50 meters deep.
基桩和土地之间的摩擦力
The friction between the piles and the ground
让这座庞大的建筑得以矗立
keeps this sizable structure standing.
一座摩天楼不仅要抵抗重力 以免崩塌
Besides defeating gravity, which pushes the building down,
还要克服从旁边吹来的风
a skyscraper also needs to overcome the blowing wind, which pushes from the side.
一般来说
On average days,
风会在高楼大厦的表面
wind can exert up to 17 pounds of force
施加每平方米17磅的压力
per square meter on a high-rise building–
重量相等于一团吹过来的保龄球
as heavy as a gust of bowling balls.
用空气动力学原理设计的建筑
Designing structures to be aerodynamic,
比如中国的上海中心大厦
like China’s sleek Shanghai Tower,
能将风的力量减少最多25%
can reduce that force by up to a quarter.
建筑以内或以外安装的支架
And wind-bearing frames inside or outside the building
能承受并吸收剩余的风力
can absorb the remaining wind force,
比如首尔的乐天世界大厦
such as in Seoul’s Lotte Tower.
但是就算实施了这些措施
But even after all these measures,
遇到飓风的时候
you could still find yourself swaying back and forth
摩天楼的最高楼层也可能会摇摆一米多
more than a meter on top floors during a hurricane.
为了防止摩天楼被风吹得左摇右摆
To prevent the wind from rocking tower tops,
许多摩天楼采用一个重达数百吨的配重
many skyscrapers employ a counterweight weighing hundreds of tons
被叫作“调谐质量阻尼器”
called a “tuned mass damper.”
比如 台北101的87层上方
The Taipei 101, for instance,
吊着一颗巨大的金属球
has suspended a giant metal orb above the 87th floor.
当大楼被风吹动时 金属球也会摆动
When wind moves the building, this orb sways into action,
将大楼的动能吸收掉
absorbing the building’s kinetic energy.
由于金属球会跟着大楼摆动
As its movements trail the tower’s,
安装在金属球和大楼之间的液压缸
hydraulic cylinders between the ball and the building
会将动能转换成热能
convert that kinetic energy into heat,
将摇摆中的大楼稳定下来
and stabilize the swaying structure.
有了这些技术
With all these technologies in place,
我们的巨型建筑可以保持屹立不倒
our mega-structures can stay standing and stable.
但在这么高的大楼内快速升降 本身就是问题
But quickly traveling through buildings this large is a challenge in itself.
在赖特的时代
In Wright’s age,
最快的电梯时速只有22公里
the fastest elevators moved a mere 22 kilometers per hour.
幸好 现代的电梯快得多了
Thankfully, today’s elevators are much faster,
其时速最少有70多公里
traveling over 70 km per hour
未来的电梯也有可能采用无摩擦力的磁轨
with future cabins potentially using frictionless magnetic rails
从而达到更快的速度
for even higher speeds.
交通管理算法也可以根据目的地将乘客分组
And traffic management algorithms group riders by destination
以让乘客和空电梯到达所需之处
to get passengers and empty cabins where they need to be.
自从赖特提议兴建一英里高楼以来
Skyscrapers have come a long way
摩天楼已经变得先进多了
since Wright proposed his mile-high tower.
过去被认为是不可能的建筑
What were once considered impossible ideas
如今已经变成了可能
have become architectural opportunities.
如今 一座大楼突破一英里的高度
Today it may just be a matter of time
可能是迟早的事情
until one building goes the extra mile.
工程师怎么确保这些巨大建筑
How do engineers ensure that these massive structures
不会在遇到大地震时倒塌？
don’t come down in a massive earthquake?
看看这个视频
Check out this lesson,
了解为什么只有最聪明的建筑
and learn why it’s not the sturdiest buildings,
而非最坚固的建筑 才能保持屹立不倒
but the smartest, that remain standing.