Chinanews.com, Dongguan, May 15 Question: Humen Bridge resumes operation on the first day with low traffic volume Experts: preparing measures to ensure long-term operation of the bridge
Author Cai Minjie
The much-watched Humen Bridge was opened to traffic on the 15th. At 15 o'clock that 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 of the Humen Bridge Management Center showed that the traffic volume decreased significantly compared with normal days. As of 15:00, the bridge did not report an accident and did not meet the conditions for starting the emergency plan.
The Humen Bridge is located on the Lion Ocean at the Pearl River Estuary, connecting Nansha District of Guangzhou City and Humen Town of Dongguan City. The main bridge is 4.6 kilometers long and the main span is 888 meters of steel box girder suspension bridge.
On May 5th, the suspension bridge of Humen Bridge exhibited abnormal jitter and obvious vertical bending vibration; the next day, the expert working group of the Ministry of Transport of China and the management party of Humen Bridge conducted a comprehensive inspection, inspection and safety assessment of the suspension bridge. Analyze the cause of vibration.
The invited expert group believes that the Humen Bridge is a long-span steel box girder suspension bridge. The continuous installation of water horses along the side rails of the bridge changes the aerodynamic shape of the steel box girder. Under specific wind conditions, it induces vertical vortex induced resonance.
At present, the overall condition of the suspension bridge of Humen Bridge is stable and the vibration suppression effect is good.
Guangdong Provincial Communications Group said that the inspection unit integrated the recent 3 years and this inspection and monitoring data, and evaluated that the technical status and load-bearing performance of the bridge structure remained stable. The vibration did not affect the structural safety. The key components of the bridge are steel box beams and slings. No abnormalities were found.
Humen Bridge Management Center held the Humen Bridge Restoration Traffic Ventilation Conference on the 15th. 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.
Within the controllable range, long-span bridge vibration is normal
Ge Yaojun said that the vibration frequency of the Humen Bridge is continuously decreasing. At the beginning of the 5th day, the vortex vibration was 0.37 Hz, with an average of 3 seconds of vibration; afterwards, it fell to 0.275 Hz, once every 4 seconds; then to 0.225 Hz, 5 Vibrate once every second, it can be seen as a gradual consumption process.
Liao Haili believes that from a scientific point of view, long-span bridge vibration is a normal phenomenon. The cause of vibration may be wind or vehicles. However, the vibration must be within the controllable range, which does not affect the safety of the bridge, nor Under this premise, the vibrations are harmless.
Will the bridge be affected by typhoons? Hardly
The effect of typhoons on long-span suspension bridges is another type of vibration: flutter.
Liao Haili said that at the beginning of the design of Humen Bridge, flutter and vortex vibrations were considered. After the occurrence of vortex vibrations, the inspection of flutter vibration was also stepped up. "In the design and construction of the Humen Bridge for more than 20 years, wind resistance design mainly This is to prevent bridge flutter. In this regard, Humen Bridge will not flutter and will hardly be affected by typhoons. "
Preparing measures to ensure long-term operation of the bridge
Liao Haili introduced that vibration suppression is mainly carried out by two methods: aerodynamic measures and dynamic measures. 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 to increase the damping ratio.
"At present, these two measures have been implemented urgently during this period, and the effect is more obvious. The Humen Bridge is back to normal. At the same time, longer-term control measures are still being prepared to ensure the long-term reliable operation of the bridge." Liao Haili said.
Special reminder, Humen Bridge continues to implement the policy of restricting travel, all-weather trucks and passenger cars with more than 40 seats are prohibited. At the same time, remind passing vehicles to drive safely, especially not to speed and stop on the bridge. (Finish)