Humen Bridge 3

[CANPRO]

Not a disaster, but certainly looks like a failure on some level...

https://www.youtube.com/watch?v=HBEHPNFmFQ0

 

[MintJulep]

https://en.wikipedia.org/wiki/Humen_Pearl_River_Bridge

Opened in June, 1997.

 

[1503-44]

Looks very suspiciously like Nov 7 1940 Tacoma Narrows

https://www.youtube.com/watch?v=j-zczJXSxnw

80 more years of experience and tons of software later and we're still making the same mistakes?

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[JAE]

Of course this reminds a lot of people of the Tacoma Narrows bridge.
What I found humorous were the comments below that video on YouTube:

[blue]gotta be more careful with the future designs man. Building bridges is one of the hardest things in my opinion because of the law of physics.

The bridge has never experince something like that since it open 23 years ago, even with those extreme typhoon in 2017 and 2018.

This bridge was designed by UK 23 years ago, they must check the issue!

There is something spirit ram is going on in China....

Scary stuff. Seems like the construction held though, so as they say - all's well that ends well.

wrong calc in natural resonance frequency. should have put air vents to let the wind through.

Need do a big job at once before it collapsed if wind excess more than 100 mph.
Just replace a big job or add bottom ties to make it less wave to avoid metals stress.

They should consider banning music being played on bridges

It was later found that theyr built 2 water counter shaking things on each end of the bridge . They now taken it down so it does not shaking anymore

Those big dummies

CIA in action? Or HK TW thugs?

The bridge got infected by an alien virus and became alive

This footage actually reflects extremely sound engineering. The bouncing of the bridge is purposely tolerated by the structure to account for aeroelastic flutter. Only inferior people wouldn't know this.

Dam man this virus is lasting longer than made in China bridge lmao

better than most italian bridge[/blue]

 

[JStephen]

We visited the Royal Gorge suspension bridge in years past. It was reasonably windy, not bad, though. Looking down the bridge it looked like it was moving maybe a foot or so.
I was talking to an older lady at the church up there. She said when they built it, it would move enough that you couldn't see cars at the far end, and that at some point, they added additional cables to restrain that.

 

[GregLocock]

In the loosest sense, yes it is like Tacoma - wind+suspension bridge gives unexpected deflections. But Tacoma was torsional instability caused by flutter, this doesn't look torsional. Apparently the problem started after a new 4 ft high wall was added recently.

I imagine that is now being un-added.

Cheers

Greg Locock


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[Sym P. le]

... this doesn't look torsional.

That's an interesting observation. I wonder if the sustained wind was diagonal to the deck somehow spawning vortex rolls down the length of the bridge? The geography of the greater area (22.793056, 113.608611) is flat river delta but the east end of the bridge is anchored in a rise of hills, which could create some interesting scenarios as well.

From Google Earth with 1.3x vertical exaggeration.

From above video at 19 sec. Note debris blowing in the wind.

 

[Sym P. le]

Further to my previous post, the weather in Hong Kong on May 5, from timeanddate.com

 

[hokie66]

But that bridge is a long way from Hong Kong, maybe 130 km.

 

[Sym P. le]

Sorry, I wasnt standing on the bridge at the time!

 

Gallopin' Gertie Redux

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Sym P. le]

In case anyone is interested in the meteorology that caused this event, I found some better info. If anyone can improve on this with charts from the region, please do.

Generally, the wind was from the south, rising to 36 km/hr in the afternoon. The airport is located 27 km from the bridge.

Map from flightradar24.com.

From Google Earth and Wikipedia

Weather data from rp5.am.

 

[Sym P. le]

It appears that temporary safety barriers set out along the windward edge were indeed the problem. It is rather incredible, though not unforseeable, that such a small item could have such a drastic effect.

A screen grab of the barrier being dismantled.

From Youtube.

 

[LittleInch]

Looking closely the original barrier has spaces under and around it which was then blocked off by the solid barriers. Clearly enough to set up a different frequency of vortex.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[IRstuff]

Seems odd that there isn't even a hint of a torsional mode

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[Sym P. le]

And when you consider that the bridge is designed to withstand hurricane force winds, the winds that afternoon were but a breeze. I'm thinking there just wasn't enough leverage to pick up the leading edge w.r.t. the trailing edge. Or another way of analyzing it, the center of lift was too far aft, i.e. over the center of the bridge as opposed being closer to the leading edge.

 

[GregLocock]

Bending mode flutter of wings is apparently a possible thing at least in FEA world, fig 24 in this

https://www.researchgate.net/public..._Analysis_of_Fully_Flexible_Aircraft/download

https://www.researchgate.net/profil...single-wing-configuration-Model-5-Index-5.ppm

Cheers

Greg Locock


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[Alistair_Heaton]

It happens in real aircraft as well.

Some of them even have emergency checklist for when its starts happening.

The saab2000 has had more than a few occurrences of it. A mate that was flying one when it happen was not happy in the slightest afterwards. Not a change of underpants but it was the first time he had ever been airsick in his life. Pretty much everyone that was sober barfed their guts up. Unfortunately they were half way across the North Sea when it started so they had 40 mins of it before they could land.

Its called aeroelastic stability

 

[hokie66]

Very few, if any, engineers or scientists completely understand this type of dynamic behavior. We try to avoid it by either tweaking or brute force, but sometimes the physics is elusive.

 

[Sym P. le]

Truly a humbling moment.