Update: The current hypothesis is that maintenance works installed temporary water-filled barriers and blocked the proper the air flow over the bridge deck. You can actually see them (red) in the video. It remains to be seen whether the bridge sustained any significant structural damage or whether it will reopen soon.
Weird stuff happening to a heavily-travelled suspension bridge in southern China. This is Humen Bridge (虎门大桥) in Guangdong Province, and shortly after this began the bridge authorities shut down all traffic.
Wind conditions at the time were initially blamed, but obviously it wasn’t even windy enough to close the bridge for weather reasons. The bridge opened in 1997 (I’ve been on it several times myself) and has lived through hurricane-level storms every year, so it’s unlikely that some specific wind conditions caused this.
Experts are now looking into whether ongoing maintenance works changed the mass or aerodynamic shape, and thus changed the natural frequency of the bridge deck. Or, some component in the structure has degraded over time and finally started a domino effect.
The bridge deck continued to vibrate overnight and into the next day, so it remains closed.
As shown on the traffic cam caption, the bridge carries the G9411 expressway and is a major artery in the Pearl River Delta.
All I can say is, Nope Nope Nope Nope Nope.