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911如何改变了摩天大楼的设计

How 9/11 Changed Skyscraper Design - Cheddar Explains

September 11, 2001, changed our lives lot.
2001年9月11日 我们的生活发生了翻天覆地的变化
Political differences seemed to disappear, at least briefly.
政治分歧似乎消失了 至少是短暂的
New security measures filled the world’s airports.
新的安全措施遍布了全世界的机场
Thousands of families mourned the loss of loved ones.
成千上万的家庭痛失所爱
And, of course, the New York City skyline lacked its two tallest buildings.
当然 纽约的天际也失去了最高的两座建筑
But there’s one change that you probably didn’t notice
但有个改变你大概没有注意到
because it took place inside new high-rise buildings.
因为它发生在新建大楼的内部
And it’s probably not what you’d expect.
而这可能不是你期待的
Before we dive in, we want to acknowledge
在深入研究之前 我们想说
that this is perhaps the most analyzed event in modern American history.
这可能是美国现代史上被分析最多的事件
It was a tragedy.
这是一个悲剧
But it occurred nearly 20 years ago,
但这件事发生在近二十年前
meaning a significant portion of the American population doesn’t have clear memories,
这意味着多数美国人对此已没有清晰的印象了
if any,of what happened.
如果有 发生了什么
In order to understand what changed
为了弄清发生了什么变化
we first need to outline how the towers were originally designed.
首先要概述双子塔当初是如何设计的
The plans for a World Trade Center date back to 1946,
世贸中心的建造计划可追溯到1946年
but those were for a single 70-story building
但其他那些拥有70年历史的单个建筑
pretty different from the Twin Towers.
与双子塔大不相同
The twins were designed by Japanese-American architect Minoru Yamasaki
双子塔是由美籍日裔建筑师山崎实设计的
after his firm won the commission in 1962
他的公司于1962年获得双子塔的设计委任后
a renowned job that landed him the cover of TIME Magazine.
他因这一知名工作登上时代杂志的封面
On April 4, 1973,
1973年4月4日
the completed towers debuted as the tallest in the world.
竣工的双子塔作为当时世界上最高的建筑首次亮相
But their height wasn’t their only remarkable feature.
但高度并非它们唯一的标志性特点
The structural design of the towers, and for that matter,
就双子塔的结构设计而言
the architectural design was quite unique.
它是相当独特的
This is Ronald Hamburger.
这是Ronald Hamburger
He was one of a few structural engineers recruited to do a postmortem on the Twin Towers after they collapsed.
他是双子塔倒塌后 被聘去事后析误的结构工程师之一
He explained that earlier skyscrapers were built with a mixture of masonry and steel frames
他解释道 早期的摩天大楼是砖石和钢架结构
with vertical columns spread throughout the building.
整个建筑布满立柱
Picture the Empire State Building
想象一下帝国大厦
practically a fortress, with 210 vertical columns throughout the building,
它实际上是一座有着210根立柱的堡垒
and fortunately no column-free spaces
幸而没有无柱空间
The Twin Towers, on the other hand, were basically “steel tubes.”
双子塔就不同了 它们基本上就是“钢管”
Steel columns lined the exterior perimeter,
钢柱沿排列在外围
connecting to the core of the building via the floors.
通过楼层连接到建筑的核心
The floors themselves were made of concrete poured on a steel frame
地板本身是由浇筑在钢框架上的混凝土制成
note that this concrete wasn’t providing vertical stability.
注意这种混凝土并不能提供垂直稳定性
Just flooring.
只是当作地板
That was the work of the core’s 47 steel columns braced with sheetrock.
起支撑作用的是内部用石膏板加固的47根钢筋
Finally, also in the core were
最后 内部还有
all of the buildings’ elevators, stairwells, and utility shafts.
整栋楼里所有的电梯 楼梯井 公用井
And the reason they did that was
这么做的原因
so that you could have this massive space of open floor space
是使人能拥有较大的地面开放空间
where you can put some desks and workstations
可以放一些办公桌和智能终端
that would not be interrupted by columns,
而不被柱子阻隔
Each building was about 95% air
每栋建筑约95%的部分是空气
so light that they swayed in a strong wind.
太轻了 以至于它们会在强风中摇摆
Now, a super-tall lightweight building may sound risky in retrospect.
现在想想 一座超高的轻型建筑可能听上去很危险
But the towers were actually quite strong.
但双子塔其实非常坚固
The design was highly redundant.
它的设计十分冗余
Structural engineers talk about redundancy
结构工程师说起冗余
much like a person wearing both a belt and suspenders.
就像一个人既系腰带又系背带一样
Either one of them can hold up your pants,
两者中任何一个都可以系牢你的裤子
but if one of them fails, you have the other present that can do the job.
但如果一个坏了另一个还可以撑住
And this building was highly redundant.
况且这座建筑是极其冗余的
Additionally, both buildings were designed
此外 这两座建筑的设计
with the prospect of an airplane impact in mind.
都考虑到了飞机撞击的可能
See, in 1945, a B-52 accidentally crashed into the Empire State Building on a foggy day.
1945年 一架 B-52 飞机在大雾天意外撞上帝国大厦
15 years later, two planes crashed into each other above the city,
15年后 两架飞机在城市上空相撞
raining debris over Staten Island and Brooklyn.
残骸碎片从史坦顿岛和布鲁克林上空如雨般落下
So designers were aware that aircraft crashing into buildings could happen.
因此 设计师意识到会有飞机撞击建筑的情况发生
The World Trade Center towers were designed for the state of the art aircraft of its day,
世贸中心双子塔的设计考虑到了当时最先进的飞机
which was a Boeing 707.
波音707
But designing a building to resist a 1960s-era plane getting lost in the fog
但设计能抵挡1960年代在雾中迷失的飞机的建筑
isn’t the same as designing one to resist a larger plane
与抵挡以最高速度飞行
being steered at top speed to intentionally cause damage.
故意造成损坏的更大飞机不同
Near major airports jetliners are limited in speed to 180 miles an hour.
在主要机场附近 喷气式客机的速度限制为180英里/小时
The aircraft that went into the Twin Towers were traveling in excess of 400 miles per hour.
撞击双子塔的飞机飞行时速超过400英里
I don’t think anyone thought that was a credible event prior to the World Trade’s
我想在世贸事件发生前 没人会相信这是真的
For our viewers who are just tuning in right now,
刚刚调到频道的观众们
a twin-engine plane or possibly a 737 passenger
一架双引擎飞机 或者可能是一架737客机
jet flying into the World Trade Center
撞向世贸中心
It appears to be still embedded inside the building.
它似乎还嵌在大楼里
The impact damaged both the outer shell and the core.
撞击破坏了大楼的外壳和内部
But both towers kept standing because of redundancy
但因其冗余结构 双子塔仍伫立着
their weight was able to shift away to unaffected columns.
它们的重量转移到了未受影响的柱子
But here’s the problem:
问题来了:
the impact had scraped the fire-resistant coating off the steel columns and beams,
撞击使钢筋柱和房梁的防火层解体
and the jet fuel had ignited a raging fire.
航空燃油引起了熊熊烈火
This heated the steel to an unsustainable temperature.
烈火将钢加热到无法承受的温度
The jet fuel burned itself off in a few minutes.
航空燃油虽在几分钟内燃烧殆尽
But what it did is it ignited all the contents of the building
但却点燃了建筑里面的东西
The heat of the fires could not and did not melt the steel.
火的热量无法也没有熔化钢筋
But it’s not actually necessary to melt steel to make the buildings come down…
但要使建筑倒塌 也不必熔掉钢筋
When you reheat steel to about 500 degrees Fahrenheit,
当钢被反复加热到大约500华氏度时
it starts to lose some of its strength and stiffness.
它开始丧失部分强度和刚度
Eventually, the floors above the impacted areas became too heavy
最终 被撞区域上方的地板对弱化的钢材而言太重
for the weakened steel to support,
使其无法支撑
and both buildings collapsed.
两座建筑物都倒塌了
You might think this tragedy would have compelled us
你可能会想 这桩悲剧会促使我们
to make drastic changes to the rules of how we build skyscrapers.
对建造摩天大楼的习惯做出重大改变
And we have in some ways that we’ll get to in a minute.
我们一会儿会讲到在某些方面的确如此
But structurally…
但就结构上来说
Building code requirements have not changed a lot.
建筑规范要求没有太大变化
The people who had a vote, felt
拥有投票权的群众认为
that the added cost of the measures
提议增加费用的方案
that were proposed did not make sense,
是毫无意义的
given what was perceived to be…the extreme rarity of such an attack.
他们觉得 这样的攻击极其罕见
The years since 2000 have seen a rise in supertall buildings around the world
2000年以来 全世界的超高建筑不断增加
nearly 9,000 skyscrapers were added from 2000-2020.
2000至2020年间 就添了近9000座摩天大楼
And even though resisting aircraft impact isn’t a requirement,
即使没必要预防飞机的撞击
many of them are much stronger anyway
由于不同的设计和材料
because of different designs and materials.
它们中的许多都要坚固得多
Rather than using only steel construction.
比起使用钢结构
Now most high-rise buildings, supertall buildings, are constructed all using concrete walls in the form
现在大多数高层建筑 超高层建筑 都是用混凝土墙建造的
And then steel framing around the perimeter
然后是周围的钢架
and then the floor system between the floor and the exterior wall.
再是地板和外墙之间的地板系统
Take the new World Trade Center, for instance.
以新世贸中心为例
It’s basically a hefty three-foot thick concrete core
它基本上是一个三英尺厚的混凝土核心
with a glass skin.
外加一层玻璃
The end result is a stronger building.
最终的结果是一座更坚固的建筑
This is because concrete is far more fire-resistant than steel,
这是因为 混凝土比钢材更耐火
but it’s also because concrete itself has become much stronger.
而且混凝土本身也更结实了
So concrete, typical concrete, conventional concrete we use all the time has a strength of 4,000 psi
所以混凝土 典型的混凝土 传统的混凝土 我们一直使用的混凝土强度为4000psi
Quick pause – psi stands for “pounds per square inch.”
暂停一下 psi代表“磅每平方英寸”
It refers to the total weight the concrete can support before failing.
它是指混凝土在垮掉前所能承受的总重量
The concrete used in the floors of the Twin Towers
双子塔地板所用的混凝土能承受的
ranged from 3,000-4,000 psi.
最大压力在3000-4000psi之间
But that pales in comparison to the strength of newer concrete we use today.
但这与如今使用的新型混凝土的强度相比就相形见绌了
The core of the new 1 World Trade Center, for example, uses concrete ranging in strength
像新世贸中心1号楼的核心使用的混凝土的强度
from 8,000 to 14,000 psi.
在8000至14000psi之间
And that’s not even the strongest concrete that exists!
而这甚至也不是目前存在的最坚固的混凝土
This is a relatively new type of concrete
这是一种相对较新的混凝土类型
called ultra high performance concrete.
叫做超高性能混凝土
The high-strength concrete is roughly
高强度混凝土能承受的最大压力
from 15,000 psi to 30,000 psi
大约在15000至30000psi之间
So greater safety protocols and stronger materials
因此 更严格的安全规程和更坚固的材料
have together created a wave of robust new skyscrapers
共同创造了一波坚固的新摩天大楼
even if protecting against future airplane hijackings isn’t explicitly required
即使防范未来的飞机劫持并不是明确的要求
But Hamburger told us that some of the world’s newest high-rise buildings have been constructed
但Hamburger告诉我们一些世界最新的高层建筑都采取了
with measures to protect against terrorist attacks.
防范恐怖袭击的措施
No one will tell you which buildings have been constructed with it.
没人会告诉你哪些建筑釆取了这样的措施
No one will tell you what weapon they’ve been designed to defend against,
没人会告诉你他们设计了什么武器来防御
but some of them have been voluntarily designed to be better able to resist such events.
但其中一些是自愿设计的 以便更好地抵御此类事件
Karin: do…do you know which ones?
Karin:你知道是哪些吗?
I know some of them. I don’t know all of them, and I won’t talk[laughter]
我知道其中一些 但我并不知道全部 而且我也不会说的[笑声]
Post-9/11 code changes actually revolved less around structural choices
911事件后的法规变化实际上并不围绕结构抉择
and more around “means of egress.”
更多的是围绕“出口方式”
In layman’s terms: exits.
用外行人的话来说就是出口
The designer of the World Trade Center
其实世贸中心的设计者
actually used a system that are called scissor stairs
用了一种称作剪刀楼梯的系统
But stairs were actually very close to each other within the core.
但其实核心里的楼梯彼此紧挨着
So when the plane went into the building, they managed to block both sets of stairs
所以当飞机撞向建筑时 他们设法阻塞几组楼梯
meaning that, even though people trapped inside
也就是说 即使困在里面的人理论上
theoretically had time to escape, they couldn’t.
有时间逃脱 实际上却不能
So one of the most significant things we’ve done is we’ve changed the building code
因此我们做的最重要的事情之一就是改变了关于
to require more separation between the places where stairways are located,
要求楼梯的位置之间有更多间隔的建筑法
so that it is more probable that…
因此 更可能……
there will be at least one stairway available.
至少会有一个楼梯可用
Additional code changes included widening stairways
另外的法律修改包括扩大楼道
self-luminous exit pathways;
出口途径自发光
third stairways in buildings over 420 feet
建筑内的第三楼道超过420英尺
boosting overall fire resistance; and more.
提高整体防火能力等等
These changes reflect less of a focus on saving the buildings,
这些改变反映人们对保护建筑的关注减少
and more on making sure the people inside
而更关注的是确保里面的人
have time to get out in an emergency.
有时间在紧急情况下离开

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视频概述

本视频由建筑结构入手,概述911事件之后,人们开始更重视如何保护摩天大楼内人们的安全,而非建筑本身。

听录译者

收集自网络

翻译译者

深蓝北斗星

审核员

审核员VS

视频来源

https://www.youtube.com/watch?v=4eE8d94qGPo

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