If you commute daily on a bridge or not, regardless, the idea of one collapsing during your morning school run is nightmare-inducing. Sadly, this nightmare turned into a reality for a small town in Washington, USA.
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Within 8 minutes, a structure that was created just five days ago collapsed in a pile of rubble and with it, the cars on top of it. Find out, how this preventable disaster happened in the first place and how those on top of the bridge, crawled to save their lives.
Just Another Day
It’s not quite 10 am on a blustery November morning in 1940. Like many other motorists that day, newspaperman Leonard Coatsworth makes his way toward Washington’s Tacoma Narrows suspension bridge.
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Carrying his daughter’s black cocker spaniel in the back of the car, Coatsworth cruises onto the stretching span completely unaware that it is about to collapse. As his car hits the roadway, the crossing begins to violently convulse. Horrified onlookers can only watch as he approaches what looks like certain death.
Modern Update
On its completion, the Tacoma bridge was the third-longest suspension bridge on the planet. It was designed by Leon Moisseiff, a consulting engineer of San Francisco’s Golden Gate Bridge, the world’s longest at the time.
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Constructed using light-weight steel girders and thin concrete skin, the bridge’s design was hailed as a modern masterpiece. Low-cost and easy on the eye, Tacoma was the proud home of a ground-breaking project.
Hidden Problems
But the problems began during the building process when workmen first noticed the undulations. In May 1940, those laying the roadway noted the deck’s wave-like motion or “bounce.”
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The roadway would visibly move, sending waves up and down the deck. Locals became so used to the rippling that they even gave the crossing a nickname, “Galloping Gertie.” Unfazed by this, drivers continued to use the bridge.
Reassuring The Public
Though the locals didn’t seem to be to bothered by the movements, most local news channels did point out to the sudden, dangerous and unacceptable level of undulations on the bridge.
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This forced the bridge engineers to talk to local media, where they said the movement was entirely normal and that the crossing would be perfectly safe when it opened. But just to err on the side of caution, the state installed some hydraulic dampeners in an attempt to stabilize the deck.
Bridge Opened
On November 7, 1940, Gertie’s characteristics went from weird to deadly in a matter of hours. At 7.30 am winds of 38 miles per hour were gusting across The Narrows. This would be an event which would ripple itself into a disaster.
Image: University of Washington Libraries Digital Collections
This increased the bridge’s rippling, with the surrounding waves reaching as high as five feet. Despite this, the bridge remained open to traffic. Everything seemed to s smoothly but around 10 am, Gertie began doing something unbelievable.
Unpredictable Movement
The bridge began to twist. At which point, the authorities finally decided to close it to all traffic. This dramatic turn of events didn’t go unnoticed by locals. Crowds began to gather, watching the bridge writhe in horrified silence.
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The sounds of screeching metal and crumbling concrete joined the gusting wind, adding to the sense of impending doom. And among the spectators, two men set up their 16mm cameras, ready to capture the events as they unfolded.
Closed But Not Empty
The bridge continued to twist, reaching ever-higher with each swing. But while the crossing was closed to traffic, it certainly wasn’t empty. With a few locals, thinking the movement was so big deal.
Image: via Wikimedia Commons
At around the same time that Leonard Coatsworth was unwittingly making his way onto the bridge, a single pedestrian also began to cross. But this walker was doing so for a very different reason.
Risk Takers
Winfield Brown, a 25-year-old college student decided the twisting bridge was an opportunity not to be missed. He later said he crossed the bridge, not once, but twice, because he “wanted to get a little fun out of it.” It was a decision, though, that he soon came to regret.
Image: University of Washington Libraries Digital Collections
“About the time I got to the centre, the wind seemed to start blowing harder, all of a sudden. I was thrown flat. Time after time I was thrown completely over the railing. When I tried to get up, I have knocked flat again. Chunks of concrete were breaking up and rolling around. The knees were torn out of my pants, and my knees were cut and torn.”
Not Alone
The student went on, “During the worst parts, the bridge turned so far that I could see the Coast Guard boat in the water beneath.” Eventually, though, he made it to safety. “I don’t know how long it took to get back. It seemed like a lifetime. As soon as I got off the bridge, I became sick.”
Image: YouTube/Garrett Lenz
During Brown’s ordeal, he noticed someone else on the bridge. As the student was making his third trip, he said, “A car came up. The driver got out, walking and crawling on the other side. We didn’t have time for any conversation.” The vehicle belonged to Leonard Coatsworth. He had just driven past the East Tower when he lost control of his vehicle.
Escape
Coatsworth hit the brakes hard and made his escape through the car window. For his efforts, he was thrown face-down on the ground as the bridge convulsed once more. Holding onto the curb for dear life, he tried to reach Tubby — who was still in the car — but another twist landed him too far away to reach the dog.
Image: YouTube/Garrett Lenz
At that point, amid all the chaos and sure that the bridge was going to collapse, Coatsworth made a heart-wrenching decision. With Tubby too far away to reach safely, the newspaperman began to crawl the 500 yards back towards the toll plaza. His daughter’s cocker spaniel remained in the abandoned car.
Desperate For Safety
Making progress on his hands and knees, Coatsworth crawled over 500 yards towards the safety of the toll plaza. All the while, the bridge was twisting further and further with each turn, the sound of cracking concrete and whining steel must have been terrifying.
Image: YouTube/Garrett Lenz
Somehow, Coatsworth made it back to the toll plaza. Despite the cuts and bruises to his body, after informing the authorities that Tubby was still out there, Coatsworth then called his office. They immediately sent out a photographer to capture the incredible events as they were unfolding.
Watched In Horror
Then, at 11 am, all hell broke loose. The bridge, which had been twisting and swaying in the high winds for over an hour by now, finally began to fail. The photographer later described hearing “rumblings and explosive sounds which scared the daylights out of me.”
Image: YouTube/Garrett Lenz
As the men scrambled to safety, cables broke and the concrete cracked. Hundreds of people had gathered to watch the stricken bridge and the attempts of those stranded to escape the inevitable collapse. Bolts flew threw the air and the cables snapped with the sudden crack of gunshots. The din grew louder as steel girders twisted and wailed.
Complete Failure
At 11.02 am that morning, as the suspension cables failed, a 600-foot-long section of the bridge twisted and fell into the waters below. Creating a thunderous roar, it’s wrenching-free was followed by a cloud of concrete dust and water plumes as it hit the ocean.
Image: YouTube/Garrett Lenz
Foam shot up over 100 feet in the air and ripped electrical wires sparked and spat as they shorted. From there, successive sections of the roadway split and fell straight into the water. Along with them went Coatsworth’s car and the stricken Tubby
Personal Loss
As Coatsworth later told the Washington Department for Transportation, that was perhaps the hardest part of the day. “With real tragedy, disaster and blasted dreams all around me, I believe that right at this minute what appals me most”
Image: YouTube/Garrett Lenz
“Is that within a few hours I must tell my daughter that her dog is dead when I might have saved him.” All in all, the collapse had taken only eight minutes. But that wasn’t the end of the story.
Getting Answers
Once the dust had settled on the collapse in which, miraculously, Tubby was the only casualty, the search for answers began in earnest. Authorities turned to the bridge engineers to find out what went wrong.
Image: YouTube/Garrett Lenz
They ended up reaching out to Frederick Burt Farquharson, a professor in engineering at the University of Washington, who they hoped would be able to help them. He created a wind tunnel experiments to recreated the bridge’s twisting motion seen that day.
No Real Conclusion
The fact that the swaying had been noticed during construction and not dealt with certainly contributed to the disaster. And secondly, although Farquharson had been able to reproduce the twisting, no one could explain exactly why it occurred.
Image: YouTube/Garrett Lenz
A new bridge was eventually built, using a much sturdier design as well as the wind-dampening deflectors and holes Farquharson had recommended. Around the time the new crossing opened, the professor finally found an answer to the twisting riddle.
Modern Day Assumptions
Thanks to the spectacular footage taken on the morning of the collapse, as well as some questionable physics, many experts have attributed the incident to the wrong phenomena. The swinging swaying and rippling on the show led many physicists to conclude that harmonic resonance caused the bridge to fail.
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For the non-scientists among us, harmonic resonance is best described as the phenomena that cause the glass to break when a singer hits a particular note. And for many experts, the Tacoma Bridge is the glass and the wind the voice, leading to catastrophe.
Not The End Of It
That conclusion while popularly believed to be right, though, is far from the truth. Farquharson backed up by several other engineers puts the collapse down to a phenomenon known as “flutter.”
Image: YouTube/Garrett Lenz
This means that while the high wind caused the bridge to sway, the span’s construction meant that its reaction to the wind set up a vibration of its own. This interaction created a feedback loop of rippling, growing exponentially worse with each circuit.
Proof
But how do we not know that? The answer, it seems, is in the original video. The two cameramen responsible for the footage of the bridge collapse shot the action at different frame rates.
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One-shot at the standard 24 frames per second [fps] while the other was 16 fps. As a result, when the film was transferred to video or DVD, the footage was stretched so that it would all run at the same speed. The result of this process is that the treated film appears sped up, leading many to a false conclusion based on the rate of rising and fall on the roadway. Thankfully, though, some engineers listened.
New Research Field
The work was done after the Tacoma collapse led to a new field of research — bridge flutter. Its findings and principles have since guided the construction of several huge suspension spans, including Japan’s Akashi Kaikyo crossing.
Image: via Wikimedia Commons
As for the remains of Galloping Gertie, they’ve been given a new lease of life. While some of the twisted steel from the bridge is now on display in the local harbour museum, much of it remains on the ocean floor. And there, it has been transformed into an artificial reef, a magnet for marine life and divers alike.