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.