纽约花旗中心:一场被学生提问揭示的工程危机
这里是花旗中心(Citicorp Center: 位于纽约曼哈顿的一座摩天大楼)。
View/Hide Original English
This is Citicorp Center.
View/Hide Original English
In the summer of 1978, it had been open for less than a year when its structural engineer, Bill LeMessurier, made a terrifying discovery.
View/Hide Original English
His cutting edge skyscraper, an engineering marvel had a fatal flaw.
View/Hide Original English
Winds of just 110 kilometers per hour could cause it to collapse in the middle of Manhattan, potentially killing thousands.
View/Hide Original English
Over 200,000 people lived and worked in the surrounding area, and hurricane season was only weeks away.
View/Hide Original English
Here I am, the only man in the world who knew this. This thing is in real trouble.
View/Hide Original English
LeMessurier faced a stark choice.
View/Hide Original English
He could stay silent and hope for the best, or he could try to fix it and risk professional ruin and mass panic.
View/Hide Original English
But Citicorp Center had a 100% probability of total collapse by the end of the century.
View/Hide Original English
How could he save New York from a near certain disaster?
View/Hide Original English
And how was this allowed in the first place?
View/Hide Original English
Veritasium producer and engineer, Henry van Dyck, traveled to New York to investigate further.
独特的设计挑战:教堂与支柱
20世纪60年代,金融巨头花旗集团(Citicorp: 曾用名,现为花旗银行母公司)正试图在曼哈顿建造新的总部大楼。
View/Hide Original English
So in the 1960s, the financial giant, Citicorp, was trying to build a new headquarters in Manhattan.
View/Hide Original English
So just down the street from their original headquarters was this entire city block, which was up for sale.
View/Hide Original English
Well, everything except for this church, Saint Peter's.
View/Hide Original English
So Citicorp came to the pastor, Ralph Peterson, and asked, "What's it gonna take for you guys to leave?"
View/Hide Original English
And he came back and said, "We're not leaving. Anything that Citicorp builds has to involve the church as part of it."
View/Hide Original English
What the pastor wanted was for the church to have its own separate identity.
View/Hide Original English
So eventually they agreed on two things.
View/Hide Original English
One was to replace this old crumbling gothic church with a brand new one, which you see in front of you.
View/Hide Original English
And the second thing was that the church had to be physically distinct from the new tower.
View/Hide Original English
In other words, it had to be completely independent.
View/Hide Original English
And again, most importantly, two thirds of the space above the church had to be free and clear, had to be open.
View/Hide Original English
Citicorp then hired architect Hugh Stubbins to design the tower and the church and Bill LeMessurier as the structural engineer,
View/Hide Original English
Stubbins explained the constraints they faced.
View/Hide Original English
The church needed to be in the exact same spot and they needed to build the tower around it.
View/Hide Original English
If they were to maximize the floor area, they would have to notch out one corner of the tower for the church.
View/Hide Original English
LeMessurier agreed that could work, but why not notch two, three, or even all four corners, essentially constructing the skyscraper on stilts.
View/Hide Original English
So it's probably the first time in history that an engineer has come to an architect and said, "Let's make our job harder for us."
View/Hide Original English
The stilts would serve two main purposes.
View/Hide Original English
First, they would need to support at least half of the building's gravity load.
View/Hide Original English
The rest would be held up by a larger central column.
View/Hide Original English
Second, they would need to withstand the load due to high winds.
View/Hide Original English
But unlike an ordinary structure, the stilts wouldn't be at the corners. They would be at the center of each face.
View/Hide Original English
Imagine a chair, and instead of the columns or the supports on each corner of the chair, it's at the midpoint of each side.
View/Hide Original English
Obviously, it's not an ideal situation. It doesn't seem very stable.
View/Hide Original English
Exactly. So it created an engineering problem.
勒梅苏里耶的创新:V形斜撑与调谐质量阻尼器
当勒梅苏里耶思考这个问题时,他突然灵光一闪。
View/Hide Original English
As LeMessurier considered the problem, he suddenly had a flash of inspiration.
View/Hide Original English
He grabbed a napkin and sketched out an idea.
View/Hide Original English
He drew six layers of diagonal braces up each face of the tower.
View/Hide Original English
These chevrons would transfer the forces to the middle of each face and down to the stilts.
View/Hide Original English
Now we have to see the gravity loads, right?
View/Hide Original English
But now here's the trick.
View/Hide Original English
The gravity loads are coming down the column.
View/Hide Original English
When they get to the brace, they need to find their way into the brace.
View/Hide Original English
Okay.
View/Hide Original English
So what you do is you take out that column right there.
View/Hide Original English
There is no way that load can jump over and go to that column.
View/Hide Original English
And now they're coming down into the braces.
View/Hide Original English
They get down to the bottom here, and now they continue to go down.
View/Hide Original English
You take that column out, it has nowhere to go except into the brace.
View/Hide Original English
By removing the columns at the top and middle of each chevron, every tier acted as a separate unit.
View/Hide Original English
They were only connected to the braces and through the central core.
View/Hide Original English
So every eight stories, half of the gravity load would be forced through the chevrons to the midface columns, leading down to the stilts.
View/Hide Original English
Can you tell me how big of a new idea was this?
View/Hide Original English
Yeah, well, this particular system was entirely unique, driven by the placement of the columns, driven by the conditions of the building.
View/Hide Original English
As satisfied the chevrons could transfer the gravity load, LeMessurier turned his attention to the second problem, the wind.
View/Hide Original English
When wind hits the left side of a normal building with corner columns, the entire frame deforms like this.
View/Hide Original English
So to reduce this deformation, we could strengthen these joints, but there's a better way because beams and columns are much stronger in compression or tension than they are with bending loads.
View/Hide Original English
So if we add diagonal bracing, they can carry this horizontal load.
View/Hide Original English
The beams sort of act like springs, and when they're compressed, they push on the joints.
View/Hide Original English
When they're stretched, they pull inwards.
View/Hide Original English
With braces like these, the wind load compresses this diagonal and stretches this one.
View/Hide Original English
The left column pulls down in tension and the right column pushes up in compression.
View/Hide Original English
Where the braces meet, they both push the bottom beam to the right.
View/Hide Original English
This stretches the left side and compresses the right one.
View/Hide Original English
But this floor is the top of the next chevron, so this lower section is carrying the force from the layer above it and the normal wind load from the side.
View/Hide Original English
And this keeps happening at every chevron so the wind load builds up as you go down the building.
View/Hide Original English
But Citicorp can't have corner columns like this because of the gravity load.
View/Hide Original English
So in the wind, this entire triangle wants to rotate like this and to prevent that from happening, this chevron pulls down going into tension and the far chevron pushes up in compression.
View/Hide Original English
The top and bottom beams are again forced into compression and tension.
View/Hide Original English
The wind load ends up wrapping around the entire building.
View/Hide Original English
So every chevron works to transfer the wind load to the section below.
View/Hide Original English
When we think about skyscrapers, like how big of a deal is wind?
View/Hide Original English
If we made a skyscraper here, you know, out of all these different things, you push with your phone, you get a certain amount of force, but then you push on my phone as well with a certain amount of force, but your phone is also pushing on my phone.
View/Hide Original English
And so that's the shear in the building, what we call the building shear.
View/Hide Original English
It increases as you go down the building.
View/Hide Original English
You know, at the 10th floor, you may have a smaller force than at the 60th floor, but the total force of the 10th floor is like carrying everything above it. So it's much bigger than what's going on on the 60th floor.
View/Hide Original English
So these chevrons were key to LeMessurier's design, but the braces were massive, almost 40 meters long end to end.
View/Hide Original English
So even if you could fabricate a steel brace that long, there would be no way to get it through Manhattan.
View/Hide Original English
So instead it was sent in pieces to be welded together on site.
View/Hide Original English
The chevron bracing solved the wind and gravity load issues, but it also created a different problem.
View/Hide Original English
Because of the chevron bracing system, they were able to save a lot of money and weight.
View/Hide Original English
It was a lighter construct than most other buildings in New York, I think it was 22 pounds a square foot, which is very light.
View/Hide Original English
Unfortunately, that made the building swayable, it could move in the wind.
View/Hide Original English
That wasn't necessarily a structural problem, it was just, it could have been uncomfortable for the patrons.
View/Hide Original English
The way they could solve this was just let's add more structural steel and make it a lot stiffer.
View/Hide Original English
But the solution that LeMessurier came up with was far more elegant.
View/Hide Original English
He adopted something that had been regularly used in bridges, power lines and ships, but never before in a building: a tuned mass damper or TMD.
View/Hide Original English
So we're here at Stark Laboratories, and I'm not with Iron Man, but instead the Columbia Space Initiative, the student team here on campus who has helped us build this incredible tuned mass damper kind of system.
View/Hide Original English
We'll use this cart to represent a building.
View/Hide Original English
By pulling it back and releasing it, we can excite its resonant frequency,
View/Hide Original English
And then we'll put on a little pendulum, aluminum rod, and a mass at the bottom.
View/Hide Original English
As the building sways, it transfers some of its kinetic energy to the pendulum, which starts to swing.
View/Hide Original English
Then some of its energy is dissipated through friction at the hinge.
View/Hide Original English
The pendulum and the building oscillate out of phase from each other.
View/Hide Original English
So every time the building pulls the pendulum in a different direction, more energy is lost, significantly damping the sway of the tower.
View/Hide Original English
But this system needs to be carefully tuned so it has the same frequency as the building itself and the right amount of friction.
View/Hide Original English
So first, the mass needs to be at least one to 5% of the building's weight to be effective.
View/Hide Original English
And we tune the frequency of the TMD by adjusting the length of the pendulum.
View/Hide Original English
I assume engineers do math around this thing, but we're just doing it by feel.
View/Hide Original English
(both laugh)
View/Hide Original English
Second, by loosening or tightening the bolt, we can tune the amount of damping.
View/Hide Original English
We need to dissipate more energy from friction at the hinge to stop the swaying faster.
View/Hide Original English
We just tighten the top bolt, make the whole system a little bit, you know, add a little bit more resistance, and we'll see if we can dampen it now further.
View/Hide Original English
Woohoo.
View/Hide Original English
Much different. Yeah.
View/Hide Original English
Yeah, that looked great. That was so quick.
View/Hide Original English
Yeah, that was.
View/Hide Original English
It is cool when an experiment works.
View/Hide Original English
Does not always happen.
View/Hide Original English
There are many different types of TMDs, like pendulums, liquid columns, and a large mass on springs.
View/Hide Original English
LeMessurier used this last one in Citicorp.
View/Hide Original English
What you see is a mass of concrete, which is 29 feet square and about eight feet thick and weighs 400 tons.
View/Hide Original English
It was installed on the top floor and it's affectionately known as that great block of cheese.
View/Hide Original English
As Citicorp sways to one side, the block starts to move in the same direction.
View/Hide Original English
Some energy is dissipated through separate viscous dampers.
View/Hide Original English
Citicorp's oscillations are damped through those energy losses as the block oscillates out of phase to the building's motion.
View/Hide Original English
LeMessurier expected the damper to reduce the amplitude of swaying by roughly 50%, and he saved around $4 million by not needing an additional 2,800 tons of structural steel.
View/Hide Original English
With both the chevron bracing to channel forces to the stilts and the tuned mass damper to reduce sway, LeMessurier was convinced the building was structurally sound.
View/Hide Original English
On Citicorp Center's opening day in 1977, it was the 11th tallest building in the world.
View/Hide Original English
It was described by the press as an acrobatic act of architecture.
View/Hide Original English
Later, the American Institute of Architects even gave it an honor award, calling it a tour de force as a stylish silhouette in the skyline, and, for the pedestrian, a hovering cantilevered hulk.
致命的发现:螺栓、斜向风与安全系数
那么,一切都顺利进行了好几年,对吗?
View/Hide Original English
So then, it's going swimmingly for years, right?
View/Hide Original English
Well, it's going swimmingly for about a year.
View/Hide Original English
The first hint of trouble came in May, 1978.
View/Hide Original English
LeMessurier was talking with another client about welding similar chevron braces.
View/Hide Original English
The architect and the steel fabricator said, "Tell me, how did those welded braces work out?"
View/Hide Original English
Seems like overkill, they thought.
View/Hide Original English
And LeMessurier says, "Yeah, they were fine. Let me call my guys in New York and I'll check."
View/Hide Original English
So he put the call into his office in New York and they say, "Oh, Bill, didn't you know? We bolted those connections."
View/Hide Original English
The contractor had suggested saving a quarter of a million dollars by using bolts to attach the braces instead of welds.
View/Hide Original English
And LeMessurier's firm had agreed.
View/Hide Original English
There is nothing that says a bolt is inherently worse or better than a weld.
View/Hide Original English
You use them in different circumstances for different reasons, but it's a little surprising to find out,
View/Hide Original English
I thought the connections in this tour de force, one of a kind skyscraper, you know, that's on the cutting edge of structural engineering, was connected one way, but apparently it's connected another way.
View/Hide Original English
But if the braces are going like this, where are they gonna go?
View/Hide Original English
You know, you only need the weld when the braces are going like this.
View/Hide Original English
Since the gravity load was always compressing the braces, some of the chevrons only went into tension under very high winds.
View/Hide Original English
And even then, it wasn't a lot of tension.
View/Hide Original English
LeMessurier trusted that his team did the right calculations, and the substitution was fine, logical, even.
View/Hide Original English
(phone ringing)
View/Hide Original English
But around a month later, LeMessurier got a phone call from a student who wanted to ask some questions about the Citicorp Center.
View/Hide Original English
And his teacher said to him, "That engineer didn't know what he's doing and nobody should put the columns in the middle. They should put 'em in the corners. That's silly."
View/Hide Original English
And I told the student, I said, "Well, you're a professor's full of it. He doesn't understand the problem we had to solve."
View/Hide Original English
LeMessurier went through the calculations with the student to reassure him the stilts were in the right place.
View/Hide Original English
But the interesting thing is, is in that moment, he's thinking about wind loads from all directions.
View/Hide Original English
You know, late spring, early summer of 1978, Bill LeMessurier is working on the back of a Hilton Hotel that, in plan, forms a triangle, not a rectangle.
View/Hide Original English
Now you got a triangle. What's your orthogonal direction?
View/Hide Original English
You just have to give up and say, "We're gonna analyze it from every direction."
View/Hide Original English
That's going on the moment that Bill LeMessurier gets this phone call.
View/Hide Original English
Then I called him back and pointed it out to him that there's some peculiar things about this building.
View/Hide Original English
The worst loading case was not the diagonal, but it was the ordinary wind that everybody thinks about.
View/Hide Original English
The wind pushes straight on the building.
View/Hide Original English
That was the critical case.
View/Hide Original English
He said, you know what, I've been getting all these calls from all these people.
View/Hide Original English
I'm gonna sit down and explain this thing.
View/Hide Original English
He decided to double check what happens to the building if wind is hitting a corner of the building, not straight on one of the faces.
View/Hide Original English
These are also known as quartering winds.
View/Hide Original English
So the west side and north side are hit by the force divided by the square root of two.
View/Hide Original English
He computed the forces for each, as we did before, and summed up the result, but then he noticed something strange.
View/Hide Original English
Then now we look at the diagonals, the stresses in half of them vanish, and in the other half, double.
View/Hide Original English
Since the force on each side was F over the square root of two, these beams get double that.
View/Hide Original English
Compared to LeMessurier calculations for the perpendicular wind load, the forces here were 40% higher.
View/Hide Original English
So 1.4 by itself is not enough to wreck havoc.
View/Hide Original English
Okay? It may be, but it may not be.
View/Hide Original English
Okay.
View/Hide Original English
So then the question is, well, what happens?
View/Hide Original English
This increase in forces wouldn't have mattered in the original design since the chevrons were fully welded together.
View/Hide Original English
But that wasn't the case anymore.
View/Hide Original English
LeMessurier remembered his earlier phone call.
View/Hide Original English
The welds holding the chevrons together were swapped for bolts.
View/Hide Original English
How did his team calculate the number of bolts per joint?
View/Hide Original English
Did they consider quartering winds?
View/Hide Original English
It would be a miracle if they ever thought that through, to think about the diagonal wind.
View/Hide Original English
It just wasn't in the nature of anybody.
View/Hide Original English
So I had a bit of a worry.
View/Hide Original English
I didn't panic right away, but I decided to go down to New York to my office.
View/Hide Original English
LeMessurier requested the building diagrams and poured over all of the connections.
View/Hide Original English
He looked at how his firm calculated the number of bolts.
View/Hide Original English
There was no question, they had taken straight on wind, not the diagonal wind.
View/Hide Original English
Although wind speed is highest at the top of the tower, the wind shear builds up as you go lower.
View/Hide Original English
Looking at this brace around halfway down the tower, the perpendicular wind load is 454 tons.
View/Hide Original English
Because of the skipped columns, all of these braces carry the same gravity load, just 340 tons, from the eight stories above.
View/Hide Original English
The gravity load builds up in the center column, not in the braces,
View/Hide Original English
which means there are 114 tons of tension in this brace.
View/Hide Original English
If each bolt can withstand around 28 tons, that would require four bolts.
View/Hide Original English
The original calculations said just four bolts were enough.
View/Hide Original English
So that was all they used.
View/Hide Original English
But when he added quartering winds, LeMessurier's calculations showed there were some braces that needed far more bolts.
View/Hide Original English
At this particular part of the building, which I can show you on my calculations is right about here, and Bill LeMessurier talked about the 30th floor, and I always wondered why was it the 30th floor?
View/Hide Original English
The 40% increase from quartering winds means that this brace has a wind load of 635 tons.
View/Hide Original English
The tension in the brace is now 295 tons, over double the original calculation.
View/Hide Original English
So these braces actually need around 10 bolts, not four.
View/Hide Original English
But then it turned out they had done something else.
View/Hide Original English
LeMessurier's firm considered the braces to be minor structural elements.
View/Hide Original English
They didn't use the right factor of safety to calculate the number of bolts.
View/Hide Original English
They should have overestimated the tension in the brace by underestimating the gravity load.
View/Hide Original English
With only 75% of the gravity load, the tension in the beam is now 380 tons.
View/Hide Original English
So they really needed 14 bolts, but they used only four.
View/Hide Original English
I thought this thing is in real trouble.
View/Hide Original English
Imagine, you know, what Bill LeMessurier was thinking at that moment.
View/Hide Original English
You see that number and you're like, "Oh my God, this is serious. It's really serious."
View/Hide Original English
LeMessurier was starting to panic.
View/Hide Original English
He didn't wanna rush to conclusions, so he flew to Canada to check his calculations with Alan Davenport at the Boundary Layer Wind Tunnel.
View/Hide Original English
After running more tests, they found that it was even worse than LeMessurier thought.
View/Hide Original English
The estimated 40% increase in stress was technically correct, but LeMessurier made his calculations assuming the building wasn't moving.
View/Hide Original English
This is called static conditions.
View/Hide Original English
But the wind tunnel gave LeMessurier a dynamic analysis, how the forces change when the building is moving around.
View/Hide Original English
To LeMessurier's horror, the wind tunnel analysis showed that the stresses could increase up to 60% more than originally anticipated.
View/Hide Original English
LeMessurier squirreled himself away in Maine and worked through the data from the wind tunnel again, joint by joint on every floor.
View/Hide Original English
The weakest joints were at the building's 30th floor.
View/Hide Original English
If those failed, the entire building would fall.
View/Hide Original English
But what were the chances that a storm strong enough to topple the building would pass through New York City?
View/Hide Original English
LeMessurier dug through the historical weather reports.
View/Hide Original English
On average, a storm strong enough to tear the building apart occurred every 67 years.
View/Hide Original English
But only if the tuned mass damper was working.
View/Hide Original English
If a storm knocked out power, then even 110 kilometer per hour winds blowing for just five minutes would collapse the building.
View/Hide Original English
In any given year, the chance of a storm that size happening was one in 16.
View/Hide Original English
Just one year before Citicorp was completed, wind gusts of 110 kilometers per hour roared through New York City as Hurricane Belle passed through.
View/Hide Original English
What do you think this moment was like for LeMessurier, when he ran these calculations, like-
View/Hide Original English
Oh, it must have been devastating.
View/Hide Original English
I mean, it just must have been, I can't imagine the fear. I can't imagine the feelings. I mean, like, it just must have been truly a moment he never thought he would live through.
View/Hide Original English
That storm was gonna fall down in my lifetime. And since this was July, it could fall down the summer of 1978.
View/Hide Original English
LeMessurier needed to decide and decide fast.
View/Hide Original English
But revealing this mistake could mean lawsuits, bankruptcy and professional ruin.
View/Hide Original English
He could stay silent, only Davenport knew and he wouldn't reveal anything, or he could entirely disappear.
View/Hide Original English
In a later interview he admitted, "I did say to myself, I could drive down the Maine Turnpike at a hundred miles an hour and deliberately drive into a bridge abutment. That would be the end and all of this would go away. I thought about that."
View/Hide Original English
But there was a 1 in 16 chance of collapse that very fall.
View/Hide Original English
With thousands of lives at risk, there was never any other choice but to act.
秘密修复:宁静计划与危机管理
在与几位律师和其他工程专家交谈后,勒梅苏里耶告诉了建筑师斯塔宾斯,然后他们一起通知了花旗集团董事长沃尔特·里斯顿(Walter Wriston)。
View/Hide Original English
After speaking to a few lawyers and other engineering experts, LeMessurier told the architect, Stubbins, and together they informed Citicorp's chairman, Walter Wriston.
View/Hide Original English
Within hours of that meeting, LeMessurier acquired emergency generators for the tuned mass damper.
View/Hide Original English
The TMD was originally designed to stabilize any swaying for comfort, but now it became the crutch that the tower leaned on.
View/Hide Original English
LeMessurier pinned all his hopes on it.
View/Hide Original English
He called the confidential repair plan Project Pandora, but that sounded ominous, so he came up with the Special Engineering Review of Events Nobody Envisioned, or Project Serene for short.
View/Hide Original English
Each night, welders would enter the building after everyone left, rip off the sheet rock around the chevron beams, and then weld two five-centimeter thick, two-meter long steel plates on each joint.
View/Hide Original English
Like Band-Aids, literally Band-Aids, on both sides of these joints.
View/Hide Original English
After, they'd replaced the wall and clean everything up before the office workers came back the next morning,
View/Hide Original English
They needed to weld over 200 joints and LeMessurier ranked them by importance, starting with the ones on the 30th floor.
View/Hide Original English
But the repairs wouldn't be completed before hurricane season.
View/Hide Original English
So Citicorp worked with the Red Cross to develop a 10 block evacuation plan.
View/Hide Original English
Like, how many people were at risk in the building and if it fell, would it affect other buildings?
View/Hide Original English
Like, were there chances of it leading to something more disastrous?
View/Hide Original English
Absolutely, this would have toppled and it would've toppled into another building, which would've toppled into another building, which would've continued a horrific process.
View/Hide Original English
So it was untold what the ultimate effects could have been.
View/Hide Original English
I mean, like, just the evacuation plans were how many people?
View/Hide Original English
Thousands, the building itself housed thousands and then the residents and the businesses surrounding the building, it was into the thousands.
View/Hide Original English
Despite the risk, they decided not to tell the public or even the office workers in the building.
View/Hide Original English
No one wanted a mass panic.
View/Hide Original English
Instead, they fitted strain gauges on important structural members.
View/Hide Original English
The gauges monitored the skyscrapers every bend and twist from a comm center eight blocks away.
View/Hide Original English
At least that would give them a little bit of warning.
View/Hide Original English
But this plan required new telephone lines, and the phone company wouldn't get around to doing this for months.
View/Hide Original English
So Citicorp's chairman immediately called AT&T's president and the lines were installed the next morning.
View/Hide Original English
Now you might not be able to install emergency telephone lines at a whim, but you can still stay connected no matter what.
View/Hide Original English
(phone ringing)
View/Hide Original English
It's probably not that important.
View/Hide Original English
Henry, can you hear me? Hello!
View/Hide Original English
Team Veritasium travels all over the globe for our videos
View/Hide Original English
We traveled here to New York to visit the Citicorp Center, and there's one really annoying problem.
View/Hide Original English
It's hard to stay connected with the rest of the team while we're on site.
View/Hide Original English
We either have to pay ridiculous roaming charges, find a local SIM card and hope it actually works, or search around for public Wi-Fi that might not be the most secure.
View/Hide Original English
That's not something we wanna be dealing with while making a video.
View/Hide Original English
So Saily makes it incredibly easy and affordable to stay connected while abroad.
View/Hide Original English
Download it once and use it in over 180 countries.
View/Hide Original English
You choose how much data you want and for how long.
View/Hide Original English
It's much cheaper than roaming and super quick to set up.
View/Hide Original English
I just select the country and plan, then activate the e-SIM before I take off and I'm done.
View/Hide Original English
Then when I land, I'll automatically connect to a local network with no hidden charges and be able to do the important things, like access maps, book a car or call your boss.
View/Hide Original English
So if you've got travel plans coming up, scan this QR code to download the app.
View/Hide Original English
Choose a plan in the country you're going to and, here's the important thing, use our code, Veritasium, at checkout to get an exclusive 15% off your first purchase.
View/Hide Original English
Again, check out with code, Veritasium, and get connected no matter where you are.
View/Hide Original English
Thank you Saily for sponsoring this video.
View/Hide Original English
And now back to Project Serene.
View/Hide Original English
(phone ringing)
View/Hide Original English
(sighs) I mean, should probably take this.
View/Hide Original English
(phone beeps)
View/Hide Original English
But even though LeMessurier tried to keep Project Serene under wraps, people started asking questions.
View/Hide Original English
On August 8th, Citicorp released a statement about the repairs.
View/Hide Original English
Now, we had to cook up a line of bull, I'll tell you. And white lies at this point are entirely moral.
View/Hide Original English
(class laughs)
View/Hide Original English
You don't wanna spread terror in the community to people that don't need to be terrorized.
View/Hide Original English
We were terrorized, no question about that.
View/Hide Original English
Several newspapers reported on it, but they didn't have the details.
View/Hide Original English
Then LeMessurier got a message.
View/Hide Original English
The New York Times was trying to reach him.
View/Hide Original English
If he didn't respond, they would know something was up.
View/Hide Original English
So I mixed a martini for myself and it's one minute past six. I dialed The New York Times.
View/Hide Original English
I pick it up the phone, they pick up the phone, it's a tape recorder saying, The New York Times has gone on strike as of six o'clock.
View/Hide Original English
(class laughs)
View/Hide Original English
Not only did The New York Times go on strike, but all the newspapers in New York went on strike until October.
View/Hide Original English
So we had a press blackout and that was the greatest thing that ever happened.
View/Hide Original English
(class laughs)
View/Hide Original English
The press was off their back and the weather was beautiful.
View/Hide Original English
The repair work continued smoothly.
View/Hide Original English
But late August brought the news everyone had been dreading.
View/Hide Original English
Hurricane Ella starts brewing in the Caribbean.
View/Hide Original English
And this is the one storm that they're nervous about.
View/Hide Original English
The repairs were halfway done by now.
View/Hide Original English
I think it was a one in 200 year storm that it could withstand, but LeMessurier wasn't taking chances 'cause he didn't know the intensity of the storm.
View/Hide Original English
And this was a strong storm.
View/Hide Original English
So there was, there was a chance.
View/Hide Original English
There was absolutely a chance and they had to prepare for that chance.
View/Hide Original English
By Friday, September 1st, Ella was making her way toward New York, with winds reaching 200 kilometers per hour.
View/Hide Original English
City officials braced to start the evacuation.
View/Hide Original English
Police would go door to door to get everyone out within a 10 block radius.
View/Hide Original English
For 24 tense hours, Ella stalled around North Carolina.
View/Hide Original English
Like LeMessurier said, we were sweating blood.
View/Hide Original English
But sometime in the night, Hurricane Ella veered off into the sea at the last minute.
View/Hide Original English
It intensified and hit Canada with peak winds of 225 kilometers per hour.
View/Hide Original English
But Citicorp was safe.
View/Hide Original English
LeMessurier described that next morning in New York as the most beautiful day that the world's ever seen.
View/Hide Original English
They completed the repairs in October, just six weeks after LeMessurier told Citicorp.
View/Hide Original English
Now the building, according to LeMessurier, can withstand a one in 1000 storm.
View/Hide Original English
The repairs cost between $4 and $5 million, but LeMessurier argued that Citicorp approved an earlier building design that cost $5 to $6 million more, so they were willing to spend that much on the skyscraper anyway.
View/Hide Original English
And for almost two decades, the secret was confined to a small inner circle.
View/Hide Original English
But in 1995, "The New Yorker" finally brought Project Serene into the light.
View/Hide Original English
Far from being vilified, LeMessurier was praised for owning up to his mistake and fixing the issue as soon as possible.
View/Hide Original English
After the article, New York updated the building code to require quartering wind calculations.
View/Hide Original English
And since that first damper in Citicorp, TMDs have spread across the globe.
View/Hide Original English
allowing architects to push skyscrapers taller and slimmer.
View/Hide Original English
It's in the first tall building in the world ever built with mechanical help to make the structure work.
View/Hide Original English
That's remarkable.
View/Hide Original English
Incidentally, that has been now copied a hundred times in Japan, this is ubiquitous,
View/Hide Original English
and when I go to Japan, I'm treated like a tin god 'cause I'm the father of the tuned mass damper.
View/Hide Original English
I said, "Really?"
View/Hide Original English
Of the 20 tallest buildings in the world, six include the tuned mass damper, and they're especially critical in typhoon or earthquake-prone regions.
View/Hide Original English
For example, Taipei 101 has a massive 660 ton pendulum that stabilizes the building.
View/Hide Original English
It can withstand up to 200 kilometer per hour winds and earthquakes with magnitudes over 6.8.
争议与工程伦理的遗产
但这栋建筑的遗产仍然充满争议。
View/Hide Original English
But the legacy of this building is still steeped in controversy.
View/Hide Original English
First, who was the mysterious student that started it all?
View/Hide Original English
I think it was spring of 1978.
View/Hide Original English
There's a student at Princeton, an undergraduate student by the name of Diane Hartley, and she's studying structural engineering.
View/Hide Original English
It was time for her to consider a senior thesis, and then they decided that a study of the new Citicorp Tower would be wonderful.
View/Hide Original English
It's a remarkable thesis.
View/Hide Original English
It contains a lot of the original engineering calculations by the engineers.
View/Hide Original English
She's looking through the documentation, where did they consider quartering winds?
View/Hide Original English
And she's not seeing it
View/Hide Original English
"I must be wrong," she says.
View/Hide Original English
She's just an undergraduate student and you guys are award-winning structural engineers.
View/Hide Original English
The engineer explains to Diane Hartley, quartering winds are not a factor in this building.
View/Hide Original English
So she's satisfied. She graduates, that's it.
View/Hide Original English
Doesn't think about it again.
View/Hide Original English
But a year after "The New Yorker" article, the BBC released a documentary on the crisis.
View/Hide Original English
And so she, she was holding her baby and she turned on the television, and lo and behold, she heard them reference a conversation with a student, an engineering student from New Jersey reaching out to LeMessurier.
View/Hide Original English
And she said, "I almost dropped my baby."
View/Hide Original English
And then so she just assumed for years afterwards, she assumed that it wasn't me because I didn't speak to LeMessurier.
View/Hide Original English
But then in 2003, her thesis advisor told Diane that he checked all the other New Jersey engineering and architecture programs, and no one else was working on a project about Citicorp in 1978.
View/Hide Original English
She was the only one.
View/Hide Original English
She never spoke to LeMessurier personally.
View/Hide Original English
She never claimed to speak to LeMessurier personally.
View/Hide Original English
The assumption was that either LeMessurier was mistaken and that it was Diane Hartley who made the call, it was a female, or more likely that LeMessurier was basically tipped off by his New York engineers.
View/Hide Original English
Then, in 2011, a man named Lee DeCarolis came forward.
View/Hide Original English
And the phone call, as we understand it, came from a student at the New Jersey Institute of Technology.
View/Hide Original English
His name is Lee DeCarolis.
View/Hide Original English
He's not asking for money, he's not asking for fame or glory.
View/Hide Original English
He's just saying, "This is interesting. And I'm the guy who made this call."
View/Hide Original English
And he pretty much lined up with what LeMessurier himself said.
View/Hide Original English
Sadly, LeMessurier passed away in 2007 before he could confirm the student's identity.
View/Hide Original English
Believe it or not, 40 years later, there's still, I learned, a lot of raw feeling still on this.
View/Hide Original English
People aren't anxious to talk about this, especially people that were involved in it, even people that weren't involved in it but were tangentially involved in it.
View/Hide Original English
We reached out to a LeMessurier Associates and they refused to respond to our request.
View/Hide Original English
You think that the namesake for their company stood up and did the right thing, but I don't think they wanna be associated with mistakes.
View/Hide Original English
Their project description for Citicorp doesn't even mention the repairs.
View/Hide Original English
The building was sold to Boston Properties in 2001, who renamed it 601 Lexington.
View/Hide Original English
They also didn't respond to our request for comment and refused to let us film inside the building.
View/Hide Original English
Further questions arose in 2021, with a new study from the National Institute of Standards and Technology.
View/Hide Original English
They wanted to see if quartering winds were more demanding for a building like Citicorp,
View/Hide Original English
Although they did conclude that the pressure from perpendicular winds was greater, their analysis didn't include any internal structure specific to Citicorp.
View/Hide Original English
As for LeMessurier, the engineering field still regards his actions as upstanding.
View/Hide Original English
And the Citicorp case is taught all over the world as a case of good engineering ethics.
View/Hide Original English
In fact, in my own engineering ethics course, I learned about the Citicorp building.
View/Hide Original English
And every structural engineer experiences this.
View/Hide Original English
When you actually feel the weight of the responsibility, you're saying, "Based on my engineering, that building is gonna stand up."
View/Hide Original English
Nobody else worries about it.
View/Hide Original English
And so if you think about the emotional pressure that Bill LeMessurier was under and then needing to come back and do something about it and to mobilize and to hold that during this entire process, it's truly a remarkable story.
View/Hide Original English
I mean, I can't imagine it. I can't imagine it.
View/Hide Original English
I said, look, if you got a license from the state and a certification from university first, then now you're gonna use that license to hold yourself out as a professional, you have a responsibility beyond yourself.
View/Hide Original English
If you see something that is a social risk, good heavens, this thing would kill thousands, you must do something, you must do something.
📌 文中提及的人物和组织
公司/组织: Veritasium, Red Cross, AT&T, The New York Times, National Institute of Standards and Technology
产品/模型: Saily
媒体/书籍: The New Yorker, BBC