[Commentary] The highly-watched Humen Bridge will be opened to traffic on May 15. On the afternoon of the same day, the reporter experienced driving on the Humen Bridge and found that the bridge had less traffic and smooth traffic. At the same time, the surveillance video at the Humen Bridge Management Center showed that the traffic volume decreased significantly compared to usual. As of 15:00, no accidents were reported and the conditions for starting the emergency plan were not met.
[Commentary] On the same day, the Humen Bridge Management Center held a Humen Bridge Restoration Traffic Ventilation Conference. Chairman of the International Bridge and Engineering Association, Professor Ge Yaojun of Tongji University, and Professor Liao Haili of Southwest Jiaotong University responded to the hot issues of social concern.
[Explanation] Ge Yaojun said that the vibration frequency of the Humen Bridge is continuously decreasing. At the beginning, the vortex vibration on the 5th day averaged once every 3 seconds; to the next 5 seconds, it can be seen that it is a gradual consumption process.
[Same period] Ge Yaojun, Chairman of the International Bridge and Engineering Association and Professor of Tongji University
The reason for this vibration really took us a lot of time, because our bridges in China have n’t encountered it yet, so what we finally concluded was that the sustained vibration for a long time and the vortex-induced vibration with a relatively large amplitude make the structure The ability to resist vibration itself, called damping ratio, is equivalent to frictional force, which is dissipated with vibration.
【Explanation】 According to Liao Haili, the Humen Bridge currently mainly uses two aerodynamic and dynamic measures to suppress vibration. The former mainly installs a damper plate on the outer guardrail to improve the aerodynamic shape of the steel box beam, while the latter is to add a water tank Increase the damping ratio.
[Same period] Professor Liao Haili of Southwest Jiaotong University
Judging from the operation of the bridge in the past two days, these two measures have played a role. The entire bridge is running relatively smoothly. Today, traffic has been restored smoothly. In fact, we have more long-term control measures, and we are still preparing. .
[Explanation] As to whether the bridge will be affected by the typhoon, Liao Haili said that the impact of the typhoon on the long-span suspension bridge is another type of vibration "flutter". At the beginning of the design of the Humen Bridge, flutter and vortex vibrations were considered. After the occurrence of vortex vibrations this time, the inspection of flutter vibrations was stepped up.
[Same period] Professor Liao Haili of Southwest Jiaotong University
This aspect of flutter was not only fully considered during the wind resistance design at that time, but also to ensure that the bridge would not flutter during the 100-year service life of the bridge. So recently, after this situation occurred in Humen Bridge (vortex vibration), we took measures to dampen it, and at the same time, we also had to investigate whether it would have the risk of flutter, so in the past few days, our three university laboratories are looking for 1. While determining the vortex-induced vibration control measures, we also conducted experiments and research on the flutter problems that these measures may cause. It can be said that the bridge will never occur under the action of typhoons, and the dangerous flutter that will cause damage to the bridge will never occur. This is certain.
【Explanation】 Guangdong Provincial Communications Group said that the inspection unit has integrated the inspection and monitoring data of the past three years and the assessment believes that the technical status and bearing performance of the bridge structure remain stable. The vibration did not affect the structural safety. No abnormalities were found in the sling.
(Reporter Cai Minjie and He Junjie from Dongguan)
Editor in charge: [Wang Kai]