Practical Engineering - 2018-08-28
Wind can be one of the most critical and complicated loads on civil structures. The case of the Tacoma Narrows bridge is a well-known cautionary tale that’s discussed in engineering and physics classrooms across the world. Both resonance from vortex shedding and aeroelastic flutter contributed to the failure. When you push the envelope, you have to be vigilant because things that didn’t matter before start to become important (e.g. wind loads on lighter structures). Unanticipated challenges are a cost of innovation and that’s something that we can all keep in mind. Thank you for watching, and let me know what you think. -Patreon: http://patreon.com/PracticalEngineering -Website: http://practical.engineering Tonic and Energy by Elexive is licensed under a Creative Commons Attribution License Source: https://www.youtube.com/watch?v=U6fBPdu8w9U The Great Courses Plus is currently available to watch through a web browser to almost anyone in the world and optimized for the US, UK and Australian market. The Great Courses Plus is currently working to both optimize the product globally and accept credit card payments globally. Signup for your FREE trial to The Great Courses Plus here: http://ow.ly/R5D730k3oNg
Can confirm: Airplanes are in fact designed to aerodynamic loads. (I think)
Source: I’m an aerospace engineer
I thought he was making a joke
@Tsog Gantumur Perhaps it was if he was referencing aerodynamic loading generally, but if he was being specific to the causes of this event such as flutter, that is indeed an engineering headache with a long history in aeronautics with respect to control surfaces. From relatively high performance in light aircraft to supersonic transitions, it has been a cause of, or contributor to, many mishaps. Fortunately they are less common now, mostly in overspeed situations.
Aerospace companies exist to create perfect paperwork, to a precisely forecasted schedule, at or below projected cost. Airplanes are merely a byproduct.
I really hope you are right when people's life is included as in aerospace. I am a rc pilot and build my own planes, or re-build ARF airplanes. The cheap ones are never built to be flown, and have not been tried out. I can use my ears while standing on the ground to hear flutter from control surfaces and then immediately lower the speed (or crash), and go home and re-build. Some real planes have counter weights on control surfaces to reduce flutter (for instance Boeing 747).
Trust me, I'm an engineer.
Goes to Civil Engineering Internship for 8 Hours
Goes to Civil Engineering Class for 2 Hours
Goes Home and Opens Up YouTube
Sees Practical Engineering and Minute Physics Video
It was a good day
Funny stuff that both did kind of the same thing the same day. :)
This is what i aspire to do
"When you push the envelope you have to be vigilant because things that didn't matter before start to become important. Unanticipated challenges are a cost of innovation."
This is like Carl Sagan level stuff right here.
Nothing ventured, nothing gained.
Indeed, that was the main lesson I think.
Also, it's a big red flag when the erection crew nicknames your project "Galloping Gerty".
I think Boeing could have been wise to heed that kind of advice...
you beat me to it... 😂
That quote really stood out to me. Very true.
Airplanes designed for wind loads? That's certainly just a myth propagated by Big Aero :-P
@Kyle Butzerin sorry u got wooshed not them also /r/ihavereddit
@Detryk Willis Man you're dumb....
@Kyle Butzerin sorry tht u got wooshed sucks to suk
@JesusJuenger yum.....
Powered flight is indeed a myth propagated by big aero. You can fly without the aero industry. Take a few drops of miracle cannabis oil and jump off a cliff.
Planes are designed for wind? Getouttaheeeaarree
As someone from Tacoma; you'd be surpsied how often builders from the Southwest buil things here and dont take into account rain
You don't say 🤣😂🤣🤣
heare ey?
👊😆
4:08 I pass by a building with chimneys like that every day. I was wondering what the helical veins were for... Thanks!
Huh. You mentioned mass dampeners and the like, which minutephysics also did a video about today. Today isn't Mass Dampener Appreciation Day or something, is it?
people would write about same topic, even if they were on different continents, and this was before communication became widely available.
it's a rather strange effect,
consider it takes more than a day to research the topic and that youtube it's masive
Video sponsored by the same company probably. Other than that, just coincidence. Also driven by Patreon.
I just love how we all follow the same channels :D
whats a dampener? im pretty sure its called a damper
This happens frequently between a lot of channels. I've thought of a few reasons. Suppose an internet article, news event, or this day in history, etc simultaneously inspires multiple content creators to create similar content. Another reason could be that the same sponsor exists across all of the same youtubers & commissioned it.
It's impressive how much the bridge could actually handle before failing. Just shows how good the overall design of a suspension bridge is.
@John Ross ya i didn't understand that either.
@loganator78r I mean...is asphalt really flexible and I had no idea? Haha
@John Ross, Very flexible. Imagine how much worse roads would be without the serious ability to move around ?
@august that's crazy. In my mind I look at asphalt like concrete in a way.
Lasting only 4 months isn't great for a bridge.
Man. Your videos are the best. I learn a lot here. Sorry about my english. Greetings from Brasil.
@Mahuk your ingurish is pretty good
сорри фор мая инглиш
lol it okey
I’m sorry most English speakers are assholes. Mostly Americans, I’m an American. And we’re assholes. I’m sorry.
Your English is perfect!! As is everyone’s in this thread! It’s also, the hardest language to learn.
So. Extra points to you for learning
@Death By Lego It's not the hardest language to learn.
There was a person who was responsible for buying insurance on the TN bridge. He pocketed the money instead because he viewed the risk low...cuz we know everything. He went to jail.
http://pugetsoundblogs.com/roadwarrior/2007/05/24/insuring-the-new-narrows-bridge/ ..for those interested. I learned about it during engineering ethics class a couple of decades ago.
Bill Schlafly
I learned about the insurance scam while I was at University back in 1973. We spent a complete hour of class on it. It doesn’t come up often in discussion about the bridge failure.
When you push the envelope, sometimes the envelope pushes back.
It wants the stamp rubbed on it's skin.
Or else it gets cut open again.
Once I was reading old military manuals and in a chapter on formations and marching across territories there was a keynote that mentioned never allowing units to march in formation or in time while crossing a large bridge as the resonance could cause it to collapse.
@ErikTheRed33 I also find that hard to believe. Maybe that rule was for using foreign bridges? The Roman Legions weren't famous for staying inside of Rome...
@Quintinohthree this thing is also appear in my physics book, too. Giancoli 5th ed. Vol.1 In the vibration and wave chapter. If u need some source~
Mike Pesta regardless inside or outside the Empire, many bridges would have been built of wood. Particularly smaller ones. The stone bridges of the era — London, Paris, Rome — were famous. You generally only go to the effort if the river is big and variable (so building a wooden bridge is hard and gets swept away next winter anyway) and there’s a major trade route passing through that can pay for the costs using tolls.
Vertical wave oscillations can born if the bridge deck mounted on equal spacings. Its like Flagalet on guitar, railway support bars must be placed irregular for the same reason.
I was heard they did something like that on a bridge in my hometown once
It seems like nearly all of the major "engineering failure" videos have the same sort of thing in common. The guy holding the purse strings cheaped out after construction began.
This is why a lot of engineers major in law schools, so they can cheap out on all the law suits their employers force them to take.
washington has sort of learned their lesson, now we spend as much as humanly possible on projects like this!
Actually, not in this case. The design was specifically created to suit the budget. It was the narrowest suspension bridge designed and was actually quite celebrated for it's innovative design.
Since when did politicians worry about spending our money? Some tv show I watched about 20 years ago stated that after the George Washington Bridge was built engineers had their own goal of making them lighter. IIRC, the show said that the farther west you went the lighter the bridges were.
Just a little fan raving - This channel is one of the best things on YouTube and I really wish you could post more often. Thanks for making the channel and for doing what you can.
Amazing that the road could twist like that
I'm no enginerd but I'll go out on a I'm and certify them aeroplanns are designed to handle wind loads
Can you discuss about the recent bridge collapse the Genoa bridge?
Are those googly eyes on the bridge model? I love those details!
Not only on the bridge model, also on the model showing the tuned mass damper: 6:08
And that's from a video that is more then 2 years old: https://www.youtube.com/watch?v=f1U4SAgy60c
The googly eyes also appear on other videos.
@zvpunry it's like learning a new word. I noticed them everywhere after noticing it there. But thank you. :-)
what about that bridge that collapsed in Italy, what happened there?
https://en.wikipedia.org/wiki/Ponte_Morandi#Partial_collapse
it's got a wikipedia
This video notes that the exact cause of the collapse of the Tacoma Narrows bridge, which happened 79 years ago and was captured on film, is still a subject for debate, with no one theory having gained dominance.
At the time you posted your question, it had been about a month since the bridge in Genoa, Italy collapsed. At the time I post this, it has been about a year. Clearly, both of those are far too soon to expect definitive answers.
@Samuel Pasche And interestingly, PE has several really good videos about concrete and steel reinforced concrete, and the problems it can face. I happened to have watched these coincidentally just before seeing a very good BBC documentary about the Genoa bridge failure.
https://www.bbc.co.uk/programmes/m0007mxm
(Only available in the UK, or for those with VPN and the right settings).
Saverio Ferrari worked as an engineer for the company that built the Morandi bridge. He blamed the collapse on the decision of the original building team not to build the supporting piles with anti-seismic materials. Another problem back in the 60's was mafia involvement in public infrastructure. Many of the projects were built with under-reinforced concrete and made with too much sand and water. Additionally most cable-stayed bridges have multiple stays that fan out from the towers and attach to multiple points on the deck. This bridge only had two stays per tower, one on each side - which makes maintenance all the more critical. I saw a set of pics that looked like a tower failure where the stays were attached. Again probably a result of no maintenance. The General Rafael Urdaneta Bridge in Venezuela is the twin to this bridge and it's still standing - I think -
Plasma strike...... for real......
"I've heard that aeroplanes are designed for wind loads, but I can't confirm it"...... xD
"When you push the envelope, you have to be vigilant, because things that didn't matter before suddenly start to become important." Exactly. This is a fairly profound statement and can apply to almost everything in life, not only engineering problems.
1:04 Yay, footage from Dresden, Germany! 😀 I lived there for many years! Out of curiosity, why did you use this in particular, and where did you find it?
No! I'm not going to watch another "Why the Tacoma Narrows Bridge Collapsed" video. I've been watching these since I was in school back in 1983!
:-)
The antenna on my truck has spirals for the same purpose. I've never seen a chimney that tall but it makes sense.
This is not the primary reason for the helical antenna section, that section has the effect of adding inductance to the antenna and is referred to as a "Loading coil", that simple put, allows you to make an antenna smaller for a given RF frequency.
bgdwiepp interesting comment, especially considering the antenna in question has got to be 3' long. I've never seen spirals on those little stubby antennas. I wonder why not?
@jackfrost1031 The spiral was probably inside the antenna. Also, the higher the frequency = the shorter the antenna. Depending on the band a full 1/4 wave antenna may only be a few inches long.
I wish you would have gone a step further and told what happened AFTER the failure. Not only go through the investigation but now that they built 2 bridges in its place, how THEY were designed.
More concrete please :D
This year concrete is going to be an big topic in our class and your videos are very interesting to watch and also informative.
Are you sure the Moth Man wasn't involved with the bridge collapse?
The effort you go to in all your videos is simply amazing. Thanks for great quality videos that are interesting and make you think about things I wouldn't have other wise.
5:20 I love how this little piece of bridge has googly eyes that's so cute
Great video. I remember reading about the flutter problems on early designs of the F-15, giving rise to its characteristic dogtooth in the horizontal stab.
This is just the best. Love you scaled models. Hope you remembered the reynolds number when scaling :-).
Also "Interesting" = "enormously difficult" for those non engineers out there.
And "enormously difficult" = " many assumptions" for those engineers out there :-p
I think "hang the thing and crank up the fans until something cool happens" is appropriate scientific procedure here. Proper Reynolds scaling would only really be necessary if someone was planning on using this research to for a full-sized googly-eyes bridge and that might not be a great use of taxpayer money.
hehe... Yes it is absolutely fine. :-)
But if its worth doing, its worth overding. Thus bridge to scale and "proper" reynolds scaling it is. What wind conditions might there have been. Analyse the movement of the bridge...
Maybe this is way my youtube channel still have 0 videos :-)
Petch85 Agreed. For my industrial Electrical students “seeing is believing.”
I was expecting it to be from the bridge in Italy
This was covered when I did my engineering diploma. Every civil engineer in world has learnt about this lesson in bridge design
what were the quadrants of the oscillations? to be perfectly sync, the motion of the bridge and the wind should have been out of phase. we need to tackle this mathematically
The Tacoma Bridge is a common example shown in engineering courses
5:19 The googly eyes are hysterical, lol
I live in Tacoma. I remember when my parents taught my about Galloping Gurty.
1:05 is Dresden in Eastern Germany, where I live. Greetings from here!
More detailed and insightful than my physics class :).
Oooooooooooo - I wondered why those helical bits were present on all the big chimneys on campus - my best guess was heat baffles or structural integrity (rigidity), but that didn't make sense because I doubted they would serve well in that capacity, on either front. Now i know!
And knowing is half the battle.
G.I. Joe.
Yo Joe!
Do toilet designers take into account average fart frequencies so stinkers don't crack the bowl?
"It's a reminder of how profoundly capable we are... of making mistakes." Unclear writing.
Aircraft do experience flutter. Smaller aircraft like a Cessna typically have counter weights in the control surfaces to limit the impact of flutter.
Was it a joke when he said he can't confirm?
I wish there was an Electrical equivalent of Practical Engineering! So good!
I had this in my physics class while tackling the topic of oscillations and waves. Mad interesting.
6:34 Stockbridge dampers! I've been wondering for years. Thank-you for the captions, because I kept hearing the wrong thing.
I was actually thinking about when the next Practical Engineering video would be coming out while I was in engineering class today, a welcomed surprise
I used to live in Seattle and must have met half a dozen people who claimed to be the last person off the Tacoma Narrow Bridge before it fell down.
What about the recent Genoa bridge collapse ?
Mark Warbington - 2018-08-28
I recently learned that the tie-down straps on flatbed trucks are given a half twist before they are tightened to prevent resonance from the wind causing the straps to vibrate. For long hauls, resonance vibration can damage the straps or cause the straps to cut into whatever they are securing.
chooch1995 - 2019-08-19
Had one of the State of Illinois' finest at a weigh station inform me that I'd have to 'untwist' my 1/2 twisted cargo straps. I said "No, sorry.....not gonna do it" which brought about the ol' 'pull it around back & come in' response. Ugh.....these guys. They tried to explain to me that by twisting them I was weakening them. I explained that my straps were really just for show & are only on to meet legal requirements { I hauled cement products in paper bags - 42 80# sacks per pallet }. I tried to explain how the wind would whip the straps into a vibration that would eventually cut into the paper bags & spill the contents onto my fellow motorists' windshields. They said "You must" to which I again said "No". I again explained basic aerodynamics & the fact that the load strap was rated at a 10,000 lb. breaking limit. If they were correct { they weren't } about the strap losing half its strength, my fourteen straps were more than adequate { the weight of the product was over 3,000 lbs. per pallet riding on a wooden pallet on a wooden decked flatbed combined with gravity is all that ever held my loads on the trailer......750,000 miles logged & never lost a pallet! } to 'hold' the load. Suddenly it was no longer about the strength, but simply "The law states".....I explained the law wasn't written with paper cement sacks in mind. We stared at each other & I said "Let me simply remove the straps & you write me up for an insecure load"... they wouldn't go for it. I suggested they arrest me then. No, they didn't want that either. I said "okay...you win...sort of...I'll untwist them to make you happy, but I'm not gonna lie....as soon as I leave here, I'm gonna have to head straight for the shoulder & put them back on 'correctly'...so go ahead & ticket me now!".....they all looked at each other & mumbled about a bit before saying "Beat it, kid!!" Yeah......the 'trucker twist'......it works!
Tom R - 2019-09-26
@Hamish Tanner I'm Aussie, what's a scaley?
At least I thought I was Aussie
Paul Standaert - 2019-12-06
Or the straps get cut by whatever they are rubbing against.
Clay Ferguson - 2020-01-26
Mark Warbington the old rule I was told one twist per 7 ft of strap
Wai Chun Kwong - 2020-02-26
omg, wow, thx for telling us that. This is so interesting and good to know at the same time.