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Stupid Engineering Mistakes
Posted by
CowboyNeal
on Thu Jun 01, 2006 06:42 PM
from the back-to-the-drawing-board dept.
from the back-to-the-drawing-board dept.
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."
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one comment, one addition (Score:5, Informative)
The Kansas City Hyatt was a disaster, but it wasn't because of bad design, but actually, "Construction issues led to a subtle but flawed design change that doubled the load on the connection between the fourth floor walkway support beams and the rods carrying the weight of the second floor walkway. This new design could barely handle the dead load weight of the structure itself, much less the weight of the spectators standing on it [wikipedia.org]". The original design would have been safe but what seemed an innocuous change completely changed the dynamics of load bearing, a result easily derived by any first year physics student.
Also, while a "top ten" list is always subjective, I think it'd be instructive to at least include Galloping Gertie [nwrain.com] as honorable mention, another design which had been identified as flawed. This Tacoma Narrows suspension bridge began swaying wildly as it set up its own harmonic resonance in a typical Puget Sound winter wind storm and eventually ripped apart and collapsed into the Sound. Interestingly the original Galloping Gertie could and would have sustained the fatal winds by strategically placed holes in the beams.
Re:one comment, one addition (Score:5, Informative)
Tacoma Narrows (Score:4, Interesting)
Re:one comment, one addition (Score:5, Interesting)
Interesting factoid about the "Galloping Gertie" (Score:5, Interesting)
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.
Re:Interesting factoid about the "Galloping Gertie (Score:5, Informative)
I read the Wikipedia article and found it very interesting:
The vibration had nothing to do with the resonance frequency of the bridge as a structure, but with the fact that it was wind (as opposed to some other form of energy input, e.g. sound) that was exciting the bridge. At a certain wind speed, the bridge enters a positive feedback loop - when the small motion induced by the wind changes the angle of attack in a way that makes the bridge absorb more and more energy from the wind, eventually increasing the amplitude of the oscillation to a point where structural failure occurs.
To make it short: The bridge did not oscillate at one of its resonant frequencies - aerodynamics caused it to vibrate at an entirely different frequency but managed to pump enough mechanical energy into the bridge to break it anyway.
Re:one comment, one addition (Score:5, Interesting)
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.
Correct... (Score:5, Informative)
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.
=
Re:Correct... (Score:5, Insightful)
We need to mod this up to a 6. I also studied this disaster in school, but this simple paragraph does a much better, simpler job of explaining the cause than any other I've heard.
Re:one comment, one addition (Score:5, Insightful)
Re:one comment, one addition (Score:5, Informative)
From a standard beam perspective, that is, under solely strong-axis bending, the two configurations have the same section modulus, and therefore strength. the tip-to-tip has a greater torsional constant, and is better at long, unsupported spans (greater resistance to lateral-torsional failure, where the beam buckles out sideways, then falls).
So, why one over the other, structural concerns aside?
Back to back makes it really easy to capture a rod between the channels. It's basically a wide-flange (I beam) with a split in the center to allow loading through the neutral axis. This is used this all the time for strongbacks in soil support systems, and form walers. (pic on page 2) [williamsform.com]
If you're going tip-to-tip, you've recreated a tube structure the hard way, and you should have bought rectangular tube instead - no weld in the middle of the flange area where you joined the channels, cheaper, stronger (channels are commonly 36ksi, while tubes are 42 or 46ksi), and cleaner looking.
Basically, there's not a lot of good reasons for tip-to-tip channels.
Re:one comment, one addition (Score:5, Funny)
We're having a civilised discussion here. There's no need to go around mooning people! :)
That second one looks disturbingly like the goatse.cx guy.
This is filed under "humor?" (Score:5, Insightful)
Re:This is filed under "humor?" (Score:5, Funny)
Re:This is filed under "humor?" (Score:5, Funny)
Don't worry, they won't read the article
Feats of the past (Score:5, Insightful)
Errors were always rampant. Railway bridges used to collapse routinely. Frank Lloyd Wright built buildings that couldn't even keep the rain off, a feat pre-industrial peasants had been managing for thousands of years.
Only the best work has survived until now.
Re:Feats of the past (Score:5, Interesting)
I don't recall what the Engineers did about it. They probably just repointed the mortar, slapped on a fresh coat of paint and sneaked back to the barracks.
Three Gorges Damn (Score:4, Interesting)
Built on national pride, it's become the world's largest albatross.
Common theme (Score:5, Funny)
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
Re:Common theme (Score:5, Interesting)
I also visited the museum (quite impressive indeed) and there they told that they used to test ships for their stability by having a number of soldiers run from one side of the deck to the other in a coordinated fashion to see if the ship would start to sway. And sway it did, that strong that they had to stop the test to keep it from capsizing. But who wanted to tell the king that his wondership, the one he meant to dominate the Baltic Sea, was not even seaworthy for a pond ?
So everyone kept silent, the ship went under having hardly cleared the harbour, and the best: Afterwards noone could be hold responsible: The master shipbuilder having designed the ship had died before the launch, his successor only inherited the design at a very late stage and couldn't make any substantial changes, and the King, well... you don't hold the King accountable !
15 foot high waves of molasses (Score:5, Funny)
Re:15 foot high waves of molasses (Score:4, Informative)
Re:15 foot high waves of molasses (Score:5, Informative)
Re:15 foot high waves of molasses (Score:4, Informative)
A large molasses (treacle) tank burst and a wave of molasses ran through the streets at an estimated 35 MPH (56 km/h), killing twenty-one and injuring 150 others.
The collapse unleashed an immense wave of molasses between 8 and 15 ft (2.5 to 4.5 m) high, moving at 35 mph (60 km/h) and exerting a pressure of 2 ton/ft (200 kPa).
Google calculator shows:
35 miles = 56.32704 kilometers
No Asian disasters? (Score:5, Interesting)
Re:No Asian disasters? (Score:4, Funny)
Re:No Asian disasters? (Score:5, Informative)
The Romans beat you by almost 2000 years. The Flavian Amphitheater had a retractable roof.
Truth on front-loaders (Score:5, Informative)
1. It's actually your great-grandmother's suffering you're reliving. You see, the way to wash the sweat and human oils out of clothes was to take the big pot (like a witch's cauldron) and make Clothes Soup over an open fire. So good job on advancing yourself to 1890.
2. If you went back to freshman chemistry, you'd learn that water and oil do not mix. Which means, if you want to get the human soils out of your underwear, and the human sweat/grease out of your clothes, you're going to have to use soap. Water won't do it. Or, if you don't believe me, just stop buying laundry detergent. You do use it, right, hypocrite? FYI: The water is the medium for the soap, and removed soils. It all has to go somewhere - the soap alone won't carry it.
3a. A liberal arts guy, huh? 'Nuff said.
3b. Just for general info, did you ever see what your top-loader does with your Clothes Soup? The paddle in the middle spins a turn clockwise, then a turn counter-clockwise....and so forth. It also has to spin the drum for the spin cycle (you know, the only major moving part on a front-loader). So you have 2 major moving parts, one of which has to support counter-movement. So you're actually on the WRONG END OF THE SIMPLICITY ARGUMENT. Duh.
You do have the efficienty argument down, though. Front-loaders use 40% less water and much less soap, along with being much easier on the actual clothes because there is no paddle-like implement used to pummel your clothes. Gravity and water do that for the front-loader, off that one mono-dirctional moving part.
4. So...you do change the water in your washing machine from time to time, right?
How do you get it out?
Could it be...........a cute little rubber seal? At the bottom of the drum? Under way more standing water pressure than a front-loader sees?
PS: Check into how long Mankind has been making watertight seals. I bet you'll be suprised. We've had time to actually get kinda good at it.
How the hell did your particular brand of idiocy get modded up?
Great out of print book (Score:5, Informative)
Amazon.com
The moral of this book is that behind every great engineering success is a trail of often ignored (but frequently spectacular) engineering failures. Petroski covers many of the best known examples of well-intentioned but ultimately failed design in action -- the galloping Tacoma Narrows Bridge (which you've probably seen tossing cars willy-nilly in the famous black-and-white footage), the collapse of the Kansas City Hyatt Regency Hotel walkways -- and many lesser known but equally informative examples. The line of reasoning Petroski develops in this book were later formalized into his quasi-Darwinian model of technological evolution in The Evolution of Useful Things, but this book is arguably the more illuminating -- and defintely the more enjoyable -- of these two titles. Highly recommended.
why isnt Lake Peigneur on this list (Score:5, Interesting)
DC-10 Worst Engineering Disaster hardly... (Score:5, Informative)
And even those accidents the safety defects were quite minor, nothing major that one could claim that it was poorly engineered. Outward opening doors have been used on all aircraft, Douglas was the first one to make one as a baggage door for a production airliner, improper servicing lead to issues with the locks and finally two accidents, the final resulting in a bulkhead failing that sliced the control cables.
United 232 was a result of a failure of imagination, no one imagined that there would be a failure that massive that would severe all there hydraulic lines, even though they weren't placed next to each other (just near each other as they would have be as they have to run to similar areas of the aircraft). The engineer that designed it probably reasoned, that any failure that would result in all three being severed would be large enough that the aircraft would be lost.
Re:DC-10 Worst Engineering Disaster hardly... (Score:4, Insightful)
I guess that was a self-fulfilling prophesy, huh?
Lake Peigneur (Score:5, Interesting)
Basically, an oil rig, drilling in the middle of the lake, punctured a mineshaft below the lake (mining for salt). The end result was the entire lake draining into the mine below it. Fortunately, nobody was hurt.
From: http://members.tripod.com/~earthdude1/texaco/texa
The water of Lake Peigneur slowly started to turn, eventually forming a giant whirlpool. A large crater developed in the bottom of the lake. It was like someone pulled the stopper out of the bottom of a giant bathtub.
The crater grew larger and larger (it would eventually reach sixty yards in diameter). The water went down the hole faster and faster. The lake had been connected by the Delcambre Canal to the Gulf of Mexico, some twelve miles away. The ever-emptying lake caused the canal to lower by 3.5 feet and to start flowing in reverse. A fifty foot waterfall (the highest ever to exist in the state) formed where the canal water emptied into the crater.
The whirlpool easily sucked up the $5 million Texaco drilling platform, a second drilling rig that was nearby, a tugboat, eleven barges from the canal, a barge loading dock, seventy acres of Jefferson Island and its botanical gardens, parts of greenhouses, a house trailer, trucks, tractors, a parking lot, tons of mud, trees, and who knows what else. A natural gas fire broke out where the Texaco well was being drilled. Let's not forget the estimated 1.5 billion gallons of water that seemed to magically drain down the hole (does the Coriolis effect come into play here?). Of course, there was the great threat of environmental and economical catastrophe.
Number 3, the Vasa (Score:5, Interesting)
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.
Re:Number 3, the Vasa (Score:4, Informative)
Now, back in the day good wood carvers were relatively cheap, so hiring a crew to gussy your ship up was, all things considered, pocket change. Think of it as the 1%-for-art stipulation that is built into many civic construction projects today. The result was your ship looked shu-weet, and so when it sailed into port everyone noticed, and talked, and generally got your nation some good press.
By the way, that's still a big deal in navel circles, visiting ports and showing the flag. These vessels have to do something, keep in training, and so doing diplomatic/PR duty is as good as many other things. Part of that is looking the part - now we go for angular grey steel & exotic weaponry, back then it was "I can afford to pimp-out-my-ship" gilding.
As to the decoration being heavy, the whole freakin' ship was "heavy", a layer of pretty painted bits was about negligible in effect.
Finally, your considered expert opinion on historical wooden sailing ships aside, the hull was perfectly fine for it's needs. Yes most i^Hg^Hn^Ho^Hr^Ha^Hn^Ht^H unsophisticated folks look at these ships and wonder "however did they stay upright" but they did. Much of the misapprehension comes from not understanding the weight distribution on these craft, the rest comes from not respecting the skills of it's sailors.
And, as has been doubtless pointed out several times already, the ship sank due to late-added lower gunports that were left open and effectively scuppered them.
Tacoma Narrows & Lake Peigneur (Score:4, Interesting)
This one isn't quite on topic, but it keeps with the mood... Lake Peigneur: The Swirling Vortex of Doom [damninteresting.com]
Ten Worst of ALL TIME??? (Score:5, Insightful)
Mullholland wasn't always wrong (Score:5, Informative)
Therac-25 (Score:4, Interesting)
And really, the humor section? I know being killed by a flood of molasses is novel, how is having a walkway full of people falling on your head funny?
those poor moles (Score:5, Funny)
R-101 versus R-100 (Score:5, Interesting)
The two ships were built simultaneously, to the same set of government design specifications. The R-101 was designed by government engineers with an effectively unlimited budget, and no penalties for failing to meet specifications. Because a government agency was building it, the press were treated to frequent and highly colored bulletins about the R-101.
The R-100 was designed by a private firm, under a strict budget, with limited access to design information about the R-101. It was built with much less publicity and launched with no fanfare at all.
The R-100 made a successful trans-Atlantic test flight, was several knots faster than the specification called for, was highly maneuverable, and had a considerable payload capacity. It performed almost flawlessly, and was fairly economical to operate. (The Wikipedia article makes a bit much of the R-100's problems, such as the tail cone collapse; the engineers decided that the tail cone was unnecessary.)
The R-101 was grossly oversized and overweight, poorly stressed, and had been lengthened by some yards at the eleventh hour. Because of pressure to outperform the R-100, it was sent on an intercontinental flight before its local flight tests (which would probably have revealed its weaknesses) were completed. When it crashed, it took with it any chance that the R-100 would be followed up, even though the R-100 was a nearly unqualified success (for a prototype, anyway).
Dig up a copy of Nevil Shute's Slide Rule for an entertaining and sometimes harrowing account of the two rival airships.
I can't beleive that... (Score:5, Funny)
I guess that would be on the SOFTWARE engineering list.
Shining example of humanity in al lthe fuckups (Score:5, Insightful)
The citgroup building in manhattan. It was well desigend to the standard enginnering principles by its architecht/engineer William LeMessurier. Shortly after its construction, he got a call from a student who asked him about a different type of wind shear, and he assured the student the building was bult to withstand all winds up to like 130mph. After a little thought, he ran the numbers again as the student brought up, and realized that a hurricane might take out the building, and cause a domino effect that would take out most of manhatten. This man actually stepped up and told the buildings owners about the problem, and came up with a plan to fix it. This story seriously restored my faith in humanity, and he is one of the great unknown heroes of our age. All he had to do was keep his mouth shut, and no one could have faulted him, he did everything right. But he still stepped up and said "theres a problem with what i did...."
This is one of the best examples of ethics i have ever seen.
Re:Digg Dupe (Score:4, Insightful)
Re:Digg Dupe (Score:5, Funny)
Bahhhh.. They forgot the Disney Concert Hall (Score:5, Funny)
Re:Killed by molasses (Score:5, Funny)
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!
Re:Forgot the biggest one (Score:5, Funny)
Re:4. Northeastern US power grid, 1965 (Score:4, Funny)
Re:15 feet high? (Score:5, Informative)