Why the Tacoma Narrows Bridge Collapsed

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.

Tonic and Energy by Elexive is licensed under a Creative Commons Attribution License

This video is sponsored by The Great Courses Plus.

[JamesCoyle]

It's impressive how much the bridge could actually handle before failing. Just shows how good the overall design of a suspension bridge is.

[MarkWarbington]

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.

[clark]

In 1940, my father-in-law Joe Yamamoto was a young teenager who lived near the railroad tracks a mile or so east of the bridge. His school was on the west side. He was there the day the bridge collapsed. Less than two years later Joe, his family and all the other Japanese Americans in the area were rounded up, taken to the nearby fairgrounds, then shipped off to various interment camps throughout the West. Joe never returned to his hometown until 1998 when we embarked on an unplanned RV road trip up the Pacific Coast. Some 55 years since he last set foot in Tacoma, Joe was back in the old neighborhood. He couldn't stop talking about the Tacoma Narrows Bridge. It was a joy to see him relive his big moment in history before the war consumed the entire world. We were further rewarded when we serendipitously stumbled upon a reunion of the Tule Lake Camp internees, where he met so many friends from so long ago. For all my failures as a son-in-law, I feel very proud to have made this trip possible for Joe, my mother-in-law, and my wife. And for this reason, the Tacoma Narrows Bridge holds a very special place in my heart.

[adfaklsdjf]

"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.

[Ostsol]

4:08 I pass by a building with chimneys like that every day. I was wondering what the helical veins were for... Thanks!

[calebshonk]

I live in Michigan and north of here we have the Mackinac Bridge, which was built four years after the Tacoma Narrows bridge, yet spans almost 5x the distance. The winds between the Mackinac straits are well known for it's variability, some days it will be calm, occasionally it might experience hurricane force winds (and ice, snow, freezing rain and high heat in the summer). The bridge was built utilizing some of the lessons learned from TN. The bridge is equipped with grates in the middle and some aerodynamic buffering on the sides. Additionally, the towers were beefed up and the road suspension was built with a much deeper support system. Even with all that, the road surface will sometimes sway as much as 35 feet from side to side.

[notjackschannel]

Can confirm: Airplanes are in fact designed to aerodynamic loads. (I think)
Source: I’m an aerospace engineer

[nomore]

What I find most amazing about that Tacoma Narrows Bridge video is not the way in which the bridge failed, but the fact that the vertical motion and twisting didn't cause the deck to break apart long before the cables failed. We non-engineers typically think of concrete as completely rigid material, but that video shows quite a different story.

[LookingRickrRolls]

*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

[theonewhohonks]

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.

[FYTfaEjYHNXjChexsxmCpNEtz]

"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.

[pjcanfield]

“And our next episode is on the Tacoma Narrows Bridge disaster”
Alice: “That’s right”

[billschlafly]

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.

[pufthemajicdragon]

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.

[richdiscoveries]

This is exactly why I watch your Channel. I've watched countless documentaries on this bridge, but when I noticed you had a video of it it was a must-see. Explain things so perfectly, so easily understood that someone like me with zero engineering knowledge can completely understand what happened..
Thank you for the effort you put into these videos

[brandy]

Airplanes designed for wind loads? That's certainly just a myth propagated by Big Aero :-P

[alex]

Planes are designed for wind? Getouttaheeeaarree

[coryman]

I can't help but like this channel- it's just straight up engineering, no clickbait, or anything of that nature. Just engineering and googly eyes.

[betsykeller]

As the daughter of a former Chief of Aerodynamics for Naval Air Systems Command, I can remember going to Lakehurst and seeing model propeller variations on a large board that were monitored for how they handled wind resistance. It was the coolest thing I'd ever seen. And, I enjoyed learning about Engineering failures that led to engineering successes. Thanks for the lesson!

[seancpp]

Grady, your content is seriously some of the best stuff on here. You bring very complex topics down to earth for us to understand, and your material is also very binge-friendly. Thank you