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Stupid Engineering Mistakes
lee1 writes "Wired has bestowed on us a list of the ten worst engineering mistakes of all time. We have the St. Francis Dam designed by 'self-taught' engineer William Mulholland, which burst and wiped out several towns near LA; the Kansas City Hyatt walkway collapse; the DC-10, and more, but my favorite is the one I'd never heard of: a giant tank of molasses that ruptured in 1919 and sent 'waves of molasses up to 15 feet high' through Boston, killing 21."
I don't consider disasters as consequences of poor engineering to be especially funny.
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A common theme in half of these is that a small change was made at the last minute.
Lesson of Life: Trust the engineers, they do stuff for a reason
Of course the other half were just poor engineering
Lesson of Life: Never trust the engineers
If this signature is witty enough, maybe somebody will like me.
21 people couldn't avoid the flow of molasses? This seems very strange seeing that molasses is the canonical viscous fluid - slow as molasses in January. 15 foot amplitude, gotta wonder at the wavelength crest to crest...
Osaka built the world's first sports stadium with a movable roof, which malfunctioned shortly after inception, and the company that made it went bankrupt. The roof has been stuck for the past 5 years. Incidentally, the stadium was built on rubbery landfill, so whenever audiences jump up and down during rock concerts, it causes earthquakes in the neighborhood. Osaka also built a new airport on an artificial island that is sinking into the sea, so it may become the world's first underwater airport. Seoul has had various engineering disasters also, including a department store that collapsed and killed hundreds of wealthy housewives.
this disaster involved a couple morons on a drilling rig in a lake forgetting to carry the two, hitting a mineshaft, and draining the whole lake and part of the gulf of mexico into the mine, along with several ships, etc etc.
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I can't quite remember, but I seem to recall that the records are scanty on this point -- it may be that the designers of the ship just didn't have the expertise and understanding of buoyancy of later shipwrights, or it may be that there was some kind of kickbacks or other shenanigans that interfered with the building and compromised the design.
When I say "if you look at the ship," though, I am being literal -- because you can. The really interesting thing about the Vasa is that it sank not far from Stockholm harbor, in waters that had a unique mineral consistency. Unlike other parts of the world, for whatever reason the waters in this area were particularly unfavorable to the shipworm. Normally a wooden ship like the Vasa would be eaten up. The Vasa, however, was merely covered with silt at the bottom of the bay, where it lay for hundreds of years.
Eventually -- and again, memory fails me but I believe it was sometime around the 1970s -- the location of the Vasa was discovered and work began to bring it to the surface. Today the entire ship is on display in a museum in Stockholm. The museum building was actually built up around the ship itself. A lot of repair and preservation work had to be done, including plastination of the wood, but it is mostly intact except for the original painting. You can't go onboard, but you can walk around it and view the hull from all sides. It is literally the closest you'll ever get to a 17th century wood-hull sailing vessel -- about five meters away. They've also built a facsimile of the interior decks that you can walk through -- if walking is the word. (Let's just say they made people smaller in those days.)
The museum has salvaged all kinds of other goodies from the ship as well, from cannon to tools to even the bodies of some of the original sailors, all of which are on display. If you get the chance you should check it out -- if you're at all into things nautical, it's a one-of-a-kind experience.
Breakfast served all day!
News: Holy Shit! The town molasses has escaped! You have three hours to save yourselves!
Dude: Whoa, sounds pretty bad! I'd better...
News: Next on Six, that Paris Hilton sex tape in full! One hour later... Dude: Whoa, that ruled. I need a beer!
Dude wastes another hour or so drinking and watching pr0n.
Dude forgets about the molasses and goes to bed.
Molasses: I am nearing Dude's house.
Dude: I am now in bed sleeping, unaware of the impending danger.
The molasses eats Dude alive
Dude: What the fuck? Oh shit, the molasses! I totally forgot!
Molasses: And now there is no escape for you!
"I studied _ART_ in college and I spotted the flaw a mile away."
Yes it shows that you studied art and not engineering. We actually studied this failure in one of my classes. The poorly welded box beams probably contributed to the failure but the much larger flaw was changing the support from one in which the box beams would only be supporting the weight of one floor to one in which they would be supporting the weight of all the floors. As I recall a junior engineer approved the change without consulting with more experienced engineers. The construction crew is not at fault because they built the structure according to approved plans and field changes.
I have a MechEng/ Materials dual degree, and one of my later courses was actually a "Metal Failures" course, dedicated to this kind of stuff. Most of it was more complicated. My professor was actually a retired PhD who worked on investigative teams that evaluated accidents like these, and acted as the 'expert witness' for technical information in many cour cases.
We studied this case, as well as many on the list above, in detail. In particular, the box beams in question ran horizontally to support the walkway, while the vertical rod was the support for the end of the box beams. The beams could have been made better, but they were good enough for their design loads.
The problem was that the original design called for one continuous vertical rod, with several levels of walkway hanging from it at different heights. However, due to construction issues, the installation was changed (for the worse) so that separate vertical rods were used. This unfortunately got written approval, and shouldn't have. Instead of the successive loads being applied to the rod, the box beam was then holding the weight of all the floors below it, which it was not designed to do.
Imagine one rope hanging from a ceiling, with 3 people hanging at various heights on the rope. The rope can hold the total weight of the 3 people easily, but each climber needs only enough grip to hold up his own weight. Now imagine due to "construction issues" you can't get one long rope, so you get 2 shorter lengths. Ideally, you'd tie the ropes together to create a nearly identical scenario, but in this case, it's like they tied the bottom rope to the middle guy's ankle, and expected him to hold on with the added weight of the guy below him.
Unfortunately, it was just strong enough to hold a few people, but let go when it was fully loaded.
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"No fair, you changed the outcome by measuring it!" - Professor Hubert J. Farnsworth
The Tacoma Narrows bridge didn't fail due to resonance.
Read that first line again.
It was not resonance, your first year, second year, calculus, dynamics and control systems books all lied to you. Lied. Not truthful. Not correct.
Read: K. Billah and R. Scanlan, "Resonance, Tacoma Narrows Bridge Failure, and Undergraduate Physics, Textbooks;" American Journal of Physics, 1991.
It was not a time dependant thing, therefore, not resonance. The bridge was shaking NOWHERE near its resonant frequencies. The motion of the bridge actually induced "negative damping" . That would sort of be like pulling your parachute and having it drag you to the ground faster and faster as you gain speed. Sounds weird, but totally true. They show in that paper that the bridge under the wind loading becomes a self excited structure and, at a critical wind speed, the eigenvalues of the bridge stucture change sign, causing the bridge to enter an exponentially increasing vibrational state, eventually breaking the bridge down.
I built a cool model of the Tacoma narrows bridge, with controllable air flow, and reproduced this behavior for a college course in experimental design. It was neat to visually watch eigenvalues change in an experiment.
Oh the physics of pulling wool over eyes is so fun. BTW, that "doubling the loading that any physics student could understand" bit in the other posts. Right. Most physics students can't tell you if the box slips downhill or uphill using a free body diagram. Give me a break.