"Chan - Mid-engine with cabin fever" (superchan7)
05/14/2020 at 21:31 • Filed to: Bridges, Bridgelopnik, China, Guangdong
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"Chan - Mid-engine with cabin fever" (superchan7)
05/14/2020 at 21:31 • Filed to: Bridges, Bridgelopnik, China, Guangdong | 0
| 7 |
Update: Well, damn. They literally just opened it back up to light vehicles (no cargo vehicles and no buses over 40 passengers) . Hope to find out some analysis and test conclusions to share.
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Humen Bridge of Guangdong Province, built in 1997 and a very heavily used artery in the Pearl River Delta.
A week ago, during maintenance works, it began to display a strong wave-like vibration, scaring motorists and shutting the bridge down. Initially, blame was assigned to wind vortices caused by maintenance barriers blocking the proper air flow.
Now it has been disclosed that one set of suspension cables (#38, whatever that means) was discovered to be rusting in 2019. As a result, inspections were carried out and 128 of the bridge’s 288 suspension cables were replaced as of April 2020.
They haven’t admitted it, but I suspect this cable replacement (the combination of old and new cables) has something to do with the bridge behaving like this.
Here is a recent static load test being done. As you can see, the bridge has been vibrating for days now. Not sure what exactly they’re up to today, but I suspect more static and dynamic loading tests will be on the menu.
The video is titled to imply that this was a stunt to attempt to suppress the vibrations, but various commenters disagree with it.
Highlander-Datsuns are Forever
> Chan - Mid-engine with cabin fever
05/14/2020 at 21:38 |
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I have some Chinese coworkers who are proper civil engineers . Gonna send this out and get some hot takes.
ttyymmnn
> Chan - Mid-engine with cabin fever
05/14/2020 at 22:00 |
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Video is on a 30-second loop. Is it still undulating? Also looks pretty windy, judging by the tarps on the trucks.
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Chan - Mid-engine with cabin fever
> ttyymmnn
05/14/2020 at 22:19 |
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The bridge began vibrating in moderately high wind speeds and was closed on 5/5. This video was on 5/10, so it’s highly unlikely that the problematic wind speeds were sustained over 6 days. And yes, the bridge is still closed and no reports of the shaking having stopped .
Fortunately for the region, a second bridge was completed in 2019 to relieve congestion on this one. Needless to say, that one is now congested all the time.
coqui70
> Chan - Mid-engine with cabin fever
05/14/2020 at 22:44 |
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Depending on the shape of the waves this could be harmonic vibrations getting worse due to the mismatch between the n ew and old cables. Wind can also cause problems. Also if there are seismic vibrations that happen to get in phase with the other vibrations then the problem can get worse.
wafflesnfalafel
> Chan - Mid-engine with cabin fever
05/15/2020 at 00:32 |
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It’s doing basically exactly what the doomed original Tacoma Narrows bridge did before it snapped a single support cable which started the twisting motion that most folks associate with the bridge (and what is commonly shown.) It is interesting that the issue with this Guangdong bridge hadn’t presented itself so severely since it’s construction in 97, (the Narrows bridge did it immediately.) Maybe a minor failure that isn’t immediately apparent?
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Chan - Mid-engine with cabin fever
> wafflesnfalafel
05/15/2020 at 01:18 |
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I’ll bet it has something to do with the recent mixing in of new suspension cables.
John Norris (AngryDrifter)
> Chan - Mid-engine with cabin fever
05/15/2020 at 09:30 |
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Strange that the pavement is moving but the suspension cables and street lights on either side don’t appear to be moving. As I recall the Tacoma Narrows bridge was all moving. This must be a significantly different design where the paved section is supported differently.
Edit: I guess the streetlights are moving. Kind of hard to see on the phone.