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Embarrassing Moments in Engineering (and what they taught us)

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This article was written by Mark Fischetti and originally appeared in mental_floss magazine.

Remember giving that long and tearful toast at your brother's wedding, only to find out later that you had a huge chunk of spinach stuck in your teeth? Or the time you shot that brilliant last-second 3-pointer into the other team's basket? Or what about when you built that giant highway bridge for the city and it suddenly collapsed one day? On second thought, that last one is its own special kind of embarrassing. And one for which you'd probably trade a million spinach-toothed moments. So take comfort in knowing that, if nothing else, your bad hair day didn't put anyone in danger or make the nightly news.

Tacoma Narrows Bridge is Falling Down
Tacoma, Washington, 1940

While buildings and bridges are made to bend in the wind, the engineers behind the Tacoma Narrows Bridge might have benefited from heeding a different aphorism: everything in moderation. Stretching 2,800 feet above the riverbed, the Tacoma Narrows Bridge was (at the time) the third-longest suspension bridge in the world, behind the Golden Gate in San Francisco and the George Washington in New York City. Its sleek design incorporated a roadbed only 39 feet wide, making the bridge far more slender and light than its contemporaries. But it was also a lot more flexible.

The simple fact is that any structure built without enough "give" is more likely to break in a strong wind. There's no shortage of mathematical formulas for calculating how flexible a structure should be. But there was a problem.

The Tacoma Narrows Bridge was only one-third as stiff as common engineering rules dictated.

Even in modest winds, the roadway oscillated up and down several feet, quickly earning it the nickname Galloping Gertie.

Continue reading to see video of the collapse and learn about more engineering embarrassments.

While drivers found the undulations unsettling, the bridge seemed steady enough from the outset—at least to everyone except University of Washington engineering professor Bert Farquharson. Worried that it was far too flexible, Farquharson began studying the bridge in an attempt to uncover what sort of retrofits might improve its stability. As part of his investigation, he showed up at Tacoma Narrows on the morning of November 7, 1940, to film the movement of the bridge. His timing was eerily coincidental. As he was shooting, the Tacoma Narrows Bridge began heaving, and soon collapsed.

The Moral: It's OK to be a stiff. Materials like wood, metal, and concrete vibrate when they're struck—whether it's your fork hitting a wine glass (causing it to ring) or wind pushing across the roadbed of a bridge. If sustained, the vibrations can build to dangerous levels. It's like pushing someone on a swing; when they reach the back-most point in the oscillation, the same light push over and over will make the swing go higher and higher. You don't have to push harder each time; you just have to push repeatedly at the right moment. Similarly, if wind pushes a roadbed steadily for long enough, it can oscillate higher and higher, creating what's known as resonance.

The antidote is torsional rigidity, which is just a fancy way of saying a resistance to twisting. In the case of the Tacoma Narrows Bridge, the undulating roadbed caused alternating tension and slack in the support cables, creating a twisting motion. The action eventually became so violent that the cables snapped, and enormous sections of the bridge fell into the water below. To prevent this, Farquharson had suggested the addition of stiffeners along the roadbed. Indeed, had this retrofit been made, the collapse might have been avoided.

Citicorp Center's Close Call
New York City, 1978

citigroup-night.jpg
Talk about narrowly averting disaster. When the Citicorp Center in New York was completed in 1977, it added a dramatic, sloping peak to the city's skyline. But less than a year later, the building's chief engineer, William LeMessurier, helped it avoid destruction by razor-thin margins.

LeMessurier faced a unique situation when it came to designing the Citicorp Center. In the early 1970's, the banking behemoth was looking for a new headquarters and had its eye on a vibrant square block in midtown Manhattan. There was just one small problem: the historic St. Peter's church sat on the block's northwest corner. While the clergy wouldn't let Citicorp tear down the church, after a little negotiating, they did agree to let the bank use the airspace above it. This allowed the engineering team to form a novel architectural plan: build the 59-story rectangular tower atop four massive, nine-story-high pillars so that it actually hovered over the church. Here's a contemporary photo of the pillars, courtesy of Wikipedia:

citigroup.jpg

Having positioned the building on what essentially amounted to stilts, LeMessurier knew he would have to make the structure especially resistant to strong winds. To help stabilize it, he embedded special braces in the Center's frame every eight stories or so to prevent the skyscraper from bending too far. What's more, LeMessurier devised an additional (and unique) way to counter any swaying that might occur. At the base of the building's steeply angled roof, he placed a giant pendulum-like mechanism called a tuned mass damper—a 400-ton block of concrete resting on a film of oil and held in place by huge springs.

If winds rocked the tower left or right, the block would slip in the opposite direction, counteracting the sway. The skyscraper was the first in the United States to sport such a device.

When the Citicorp Center opened, all seemed well. But less than a year later, LeMessurier got a phone call from an engineering student in New Jersey claiming that the building's four columns (positioned at the center of the sides instead of at the corners to avoid the church) were improperly placed, making it susceptible to what sailors call quartering winds—winds that would hit the building across its vertical corners, pushing on two sides at once. LeMessurier assured him they were fine, but it prompted him to review details of the design for his own students at Harvard—and thankfully so.

That's when LeMessurier got some bad news. The skyscraper's builders broke it to him that they hadn't welded the wind braces' joints together, as LeMessurier had prescribed, but simply bolted them. This met code and saved a good deal of money, but it wouldn't allow the joints to hold in winds above 85 mph—like those that accompany, oh, say, a hurricane. True; hurricanes aren't exactly common in New York City, but LeMessurier wasn't going to take any chances.

During what had to be a rather humiliating meeting with Citicorp, LeMessurier informed the bank that it needed to make additional retrofits to the building. As not to scare the employees (or let the building's problems leak to the press), they launched a plan to make the adjustments in a more, shall we say, subtle fashion. An army of welders worked the graveyard shift seven days a week and bound two-inch-thick steel plates over all 200 joints.

The Moral: Own up to your mistakes. Roughly a month before the welding project was completed, weather forecasters predicted that Hurricane Ella was headed directly for the Big Apple. The welders tried frantically to finish the retrofits early, but ultimately, the bank had to go to city authorities and warn them of the possible catastrophe they were facing. Emergency officials secretly formed a massive evacuation plan for midtown and crossed their fingers. LeMessurier (and Manhattan) finally caught a break as Ella veered out to sea.

By the time the welders and carpenters finished, the building was one of the strongest in the country. Though justifiably annoyed, Citicorp executives commended LeMessurier for coming forward with his concerns, even though his initial work had met all code requirements. And fortunately for all the engineers involved, the entire fiasco was kept under wraps thanks to a newspaper strike that coincided with the events. Virtually no one knew about it for more than a decade, until LeMessurier released a report about the ordeal titled, "Project SERENE," an acronym for Special Engineering Review of Events Nobody Envisioned.

The Millennium Bridge's Not-So-Grand Opening
London, June 10, 2000

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The world might have avoided a Y2K disaster at the dawn of the new millennium, but it wasn't immune to the follies of bad engineering. On the morning of June 10, 2000, the Millennium Bridge in London opened with great fanfare. Only two days later, it closed with a sigh of relief from hundreds of nauseated pedestrians.

Intended as a high-profile commemoration of the 21st century, the Millennium footbridge was meant to convey a new, innovative spirit. It was given a prime location smack in the middle of downtown, connecting St. Paul's Cathedral on the north bank of the River Thames to the Tate Modern Gallery on the south. Its cutting-edge design included an aluminum deck supported from underneath by two Y-shaped frames, rather than the more common overhanging arches. The final product was sleek, futuristic—and a wee bit wobbly.

As with all bridges, the Millennium engineers designed the span to sway slightly in the wind so that it wouldn't snap. But even the light breeze blowing on the morning of June 10 was enough to make the $26 million bridge swing like a ride in a carnival funhouse. In an attempt to keep their balance, the thousands of inaugural pedestrians began to do what anybody on a rocking platform does: step in time with the rhythm of the swaying, shifting their weight from side to side to counter the motion. The result was something engineers call synchronized footfall. As more people moved in unison, more force was added to the lateral motion, and the rocking increased.

Eventually, the sway was so strong that it threatened to loft people overboard. Police quickly restricted access, and only two days later, city officials closed the bridge indefinitely.

The following year, at a cost of more than $7 million, the bridge's engineering firm and a New York-based contractor fixed the problem. Underneath the deck, they installed some 87 dampers—huge shock absorbers—to reduce the forces of synchronized footfall. The bridge reopened on January 30, 2002, but this time around, getting people to cross was going to take some convincing. City officials offered walkers free sandwiches, and even had a Southwick mayor and a London town crier dressed in Victorian garb lead the way. Still, just to be on the safe side, numerous British Coast Guard rescue vessels were placed downstream. Fortunately, the bridge proved rock solid.

The Moral: Beware of people. By the time it reopened, the Millennium Bridge (albeit inappropriately named by this point) was safe, but its engineers were roundly criticized for not having heeded the lesson of synchronized footfall. After all, even Napoleon's troops knew about its dangers. His armies always marched in unison, but whenever they came upon a footbridge, all the soldiers would alternate their stepping cadence precisely to keep the bridge from breaking.

If that weren't enough, the Millennium Bridge engineers had a much more recent call to warning. On May 24, 1987, a major "pedestrian jam" occurred on the Golden Gate Bridge, when more than 250,000 people swarmed up the ramps as part of the bridge's 50th anniversary celebration. The sheer weight of the crowd flattened the roadway (more than motor vehicles could have), putting enough slack in the suspension cables to allow the roadbed to swing. The pedestrians began stepping in time with the motion and the sway increased. Police managed to calmly dispurse the crowd, but the incident was an eye-opening reminder for engineers that even one of the most stable roadway bridges in the world isn't necessarily secure enough for people.

Kansai International Airport Learns to Sink or Swim
Osaka Bay, Japan; 1987 to present

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Never mind the two-dimensional cell phones and microscopic digital cameras. If you're talking mind-boggling Japanese inventions, think floating airport. In a country where open land is pretty hard to come by, the Japanese government commissioned the construction of an airport for the growing cities of Kobe and Osaka in the only available space around them: the clear, blue sea.

In 1987, builders started construction on a manmade island a mile and a half offshore in Osaka Bay. To build the 2.5 mile-long, half-mile-wide piece of land, they erected a giant box of rock and concrete in the water and filled it with even more rock, gravel, and sand. The idea was simple, but the process of carrying it out was anything but. It took three years, 10,000 workers and 80 barges to level two mountains and shuttle the material to sea before the box was filled.

Geologists knew the soft clay seabed would compress from the weight of the "island," but they allowed for settlement and filled the box high enough above water to negate the effect. Unfortunately, their calculations were way off.

What they didn't anticipate was the amount of water in the clay bed that would ooze out, as if seeping from a sponge. By 1990, the island had already sunk 27 feet. In an attempt to counter that sinking feeling (and heighten the island surface), workers leveled a third mountain to come up with the amount of earth needed.

Complicating matters even more were the builders' plans to erect a mile-long terminal alongside the runway. Engineers knew that if the ends or middle of the span sank at different rates, it would tear the terminal apart. To compensate for the varying rates of sinkage, they decided to rest the terminal's glass sides on 900 cement columns sitting atop two foundation walls. As parts of the walls sank, maintenance crews could jack up certain columns, slip a hefty steel plate beneath them, and level out the terminal as needed.

The Moral: Make sure to overbudget. Thanks largely to the steel-plate system, the Kansai International Airport has proved shockingly stable. Since opening in 1994, the single-terminal marvel has survived the 1995 Kobe earthquake (centered only 18 miles away) and a 1998 typhoon packing 200-mph winds.

Nevertheless, the island continues to sink about six inches per year, which means engineers are still stuffing plates beneath columns. All in all, it's a pricey project. Kansai Airport cost more than $15 billion (almost $5 billion over budget) and is deeply in debt, losing more than $500 million a year in interest payments alone. Some airlines won't use the facility because of high landing fees, and air traffic remains below profitable levels. Amazingly, the regional government is already busy building another nearby island of even larger proportions to support a second runway for the airport.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Cs California, Wikimedia Commons // CC BY-SA 3.0
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How Experts Say We Should Stop a 'Zombie' Infection: Kill It With Fire
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Cs California, Wikimedia Commons // CC BY-SA 3.0

Scientists are known for being pretty cautious people. But sometimes, even the most careful of us need to burn some things to the ground. Immunologists have proposed a plan to burn large swaths of parkland in an attempt to wipe out disease, as The New York Times reports. They described the problem in the journal Microbiology and Molecular Biology Reviews.

Chronic wasting disease (CWD) is a gruesome infection that’s been destroying deer and elk herds across North America. Like bovine spongiform encephalopathy (BSE, better known as mad cow disease) and Creutzfeldt-Jakob disease, CWD is caused by damaged, contagious little proteins called prions. Although it's been half a century since CWD was first discovered, scientists are still scratching their heads about how it works, how it spreads, and if, like BSE, it could someday infect humans.

Paper co-author Mark Zabel, of the Prion Research Center at Colorado State University, says animals with CWD fade away slowly at first, losing weight and starting to act kind of spacey. But "they’re not hard to pick out at the end stage," he told The New York Times. "They have a vacant stare, they have a stumbling gait, their heads are drooping, their ears are down, you can see thick saliva dripping from their mouths. It’s like a true zombie disease."

CWD has already been spotted in 24 U.S. states. Some herds are already 50 percent infected, and that number is only growing.

Prion illnesses often travel from one infected individual to another, but CWD’s expansion was so rapid that scientists began to suspect it had more than one way of finding new animals to attack.

Sure enough, it did. As it turns out, the CWD prion doesn’t go down with its host-animal ship. Infected animals shed the prion in their urine, feces, and drool. Long after the sick deer has died, others can still contract CWD from the leaves they eat and the grass in which they stand.

As if that’s not bad enough, CWD has another trick up its sleeve: spontaneous generation. That is, it doesn’t take much damage to twist a healthy prion into a zombifying pathogen. The illness just pops up.

There are some treatments, including immersing infected tissue in an ozone bath. But that won't help when the problem is literally smeared across the landscape. "You cannot treat half of the continental United States with ozone," Zabel said.

And so, to combat this many-pronged assault on our wildlife, Zabel and his colleagues are getting aggressive. They recommend a controlled burn of infected areas of national parks in Colorado and Arkansas—a pilot study to determine if fire will be enough.

"If you eliminate the plants that have prions on the surface, that would be a huge step forward," he said. "I really don’t think it’s that crazy."

[h/t The New York Times]

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