Experts at Humen Bridge navigable waters unblock the bridge vortex phenomenon

　　Previously, vortex vibration lasted for more than 20 hours, and experts believe that it will not have a major impact on the bridge structure; road traffic has not been restored

　　From the afternoon of May 5th to the noon of the 6th, the Humen Bridge in Guangdong repeatedly shook, lasting more than 20 hours. After the shaking occurred, the bridge and the nearby sea area were closed to traffic. Starting at 4:30 pm yesterday, the navigable waters of the Humen Bridge resumed navigation. Experts said that the shaking phenomenon is vortex vibration, which will not have a big impact on the bridge structure.

　　Beijing News News The Humen Bridge deck appeared vortex vibration from the afternoon of May 5 to noon of May 6. Affected by this, roads and water surfaces are forbidden. On the afternoon of May 7, the navigable waters of the bridge resumed navigation. It is still unknown when road traffic will resume.

　　The first vibration system is affected by the water horse

　　At 2 pm on May 5th, the vibration of the deck of the suspension bridge of Humen Bridge occurred. Multiple live video shows that when a car is driving normally on the bridge deck, the bridge deck suddenly starts to fluctuate, and the fluctuation is very obvious. After that, the bridge was closed and vehicles were forbidden, and several staff members carried out survey work on the bridge.

　　Guangdong Provincial Communications Group Co., Ltd. reported on May 6 that, according to the preliminary judgment of the expert group, the main reason for this vibration was the continuous installation of water horses along the bridge's side guardrail, which changed the aerodynamic shape of the steel box girder in a specific wind environment Under the conditions, the bridge vortex vibration phenomenon occurs.

　　According to the Guangzhou Meteorological Bureau, the winds around the Humen Bridge on May 5 were relatively strong. Among them, Humen Bridge Station maintained winds of magnitude 6 to 7 at 15-17 hours. In an interview with CCTV, Zhang Xinmin, deputy chief engineer of the Humen Bridge Overhaul Office, also mentioned the weather factor, saying that the wind around the bridge dropped to level 5 at 18:00.

　　After the incident, the water horses on the bridge deck were evacuated one after another, and the bridge deck no longer had significant vibration.

　　The next day the vibration amplitude is lighter than before

　　On the morning of May 6, the Humen Bridge appeared vibrating again.

　　Ge Yaojun, a bridge design expert, bridge wind engineering research expert, and chairman of the International Bridge and Engineering Association, said that the vibrations in the past two days are vortex vibrations, but after communicating with the site personnel and other bridge experts, the vortex vibration level on the 6th The day before was light. He speculates that it is more likely to be due to a change in the mechanical performance of the bridge, or the reduction of the mechanical damping and structural damping of the bridge. "The cause of the subsequent vortex vibration, the expert group is still waiting for the measurement data."

　　Yesterday afternoon, according to CCTV News client news, the Guangdong Maritime Safety Administration reported to the higher authorities for approval, starting at 16:30 on May 7, Humen Bridge navigable waters resumed navigation.

　　The maritime department reminds that after the navigable waters of the Humen Bridge resume navigation, the passing ships should pay attention to strengthen the lookout, observe the high frequency, and follow the traffic instructions of the maritime department on the spot to ensure the safety of navigation.

　　-Link

　　Suspension of suspension bridges occurred in many places

　　The Beijing News reporter searched and found that the wave-shaped shaking of the bridge happened from time to time.

　　The Wuhan Parrot Island Yangtze River Bridge once waved up and down on April 26 this year. Many netizens passed the bridge at the time, saying "it was like motion sickness." Later experts judged that the abnormal vibration of the bridge was caused by specific wind conditions, the amplitude was within the allowable range of the design, and the bridge structure was operating normally.

　　In May 2010, a "wave undulation" occurred on the Volga River Bridge in Russia, and a sharp deafening sound was emitted. Judging from the video, the bridge vibration form is symmetrical vertical bending vibration, accompanied by a slight torsional deformation. After the vibration of the bridge stopped, the bridge experts inspected the roads and fences of the bridge and found that the bridge was free of cracks and damage.

　　The Tokyo Bay Bridge in Japan has also experienced vortex vibrations, shaking cars up and down on the deck.

　　-Dispel doubts

　　Will vibration cause damage to the bridge?

　　The official report states that the structure of the suspension bridge of the bridge is safe and reliable, and experts believe that the vortex vibration has little effect on the safety of the bridge structure

　　Historically, there have indeed been incidents of bridge collapse due to vibration. On November 7, 1940, the Tacoma Bridge in the United States, which had just been in operation for four months, vibrated, and finally the bridge collapsed.

　　Wu Mingyuan, a member of the on-site disposal expert group and the bridge expert of China Communications Highway Planning and Design Institute, said that the suspension bridge will have two kinds of vibration, one will affect the comfort, called vortex vibration; the other will affect the safety of the bridge, Called flutter. The vibrations of the Humen Bridge this time are mainly vortex vibrations that affect comfort, and will not have a large impact on the bridge structure. The situation of the Tacoma Bridge is caused by flutter. At high wind speeds, damage is caused by structural design, and vortex vibration is at low wind speeds. So the situation between the two bridges is completely different.

　　Guangdong Communications Group also issued a notice on May 6 that according to the available data and analysis of observed phenomena, the structure of the Humen Bridge suspension bridge is safe and reliable, and the vibration will not affect the structural safety and durability of the Humen Bridge suspension bridge for subsequent use. .

　　Wu Mingyuan said that the reason why the vibration lasts longer is because the Humen Bridge is a large suspension bridge with a main span of 888 meters. It weighs more than 15,000 tons. After oscillation, the damping is relatively small, so it needs enough time to calm down.

　　In an interview with the Beijing News, Professor Fang Zheng of the School of Civil Engineering and Architecture at Wuhan University stated that the suspension bridge will have a safe range of vibration during design. Safety".

　　Is there any hidden danger to the bridge?

　　Limited load regulations, the frequency of testing has previously been increased, and the regular inspection has been increased from once every three years to once a year

　　The Humen Bridge has been in use for 23 years and has always had a relatively large traffic flow. There is also public concern. After this vortex, will there be any hidden dangers?

　　Bridge expert Wu Mingyuan said that there are load standards in the design of the bridge, as long as the operation of the bridge is safe on the basis of the load standards. In particular, Humen Bridge has limited load regulations for various reasons, so it is still safer than other large bridges under current conditions.

　　Zhang Xinmin said that since the Humen Bridge vibration occurred, professional inspection units have been organized to carry out all aspects of inspection. The highway project is a full life cycle project. It is not only to be built but also to be maintained, so it is inevitable to maintain it. It is also a work that must be done, and the country has clear requirements for maintenance standards. Previously, on the basis of national regulations, the management unit of the Humen Bridge also increased the frequency of inspections, and the scheduled inspections were increased from once every three years to once a year.

　　When can bridge deck traffic be restored?

　　It is necessary to continue the comprehensive inspection of the bridge and confirm that the bridge has no problems before it can pass.

　　The Humen Bridge is an important cross-river channel across the Pearl River Estuary. It connects Guangzhou to Nansha and is an integral part of the southern connecting line of the ring highway in the Pearl River Delta region. After the implementation of traffic control, the pressure on travel is very great. As of yesterday, the bridge still adopted traffic control measures, and when it opened to traffic became a matter of great concern to local residents.

　　In this regard, Wu Mingyuan said that the expert group will continue to do relevant research and judgments, conduct a comprehensive inspection of the bridge, and finally ensure that there is no problem before it can pass.

　　In addition, under the Humen Bridge, the main channel of the Pearl River estuary is the main channel for the entire port group. The main channel was restored to navigation yesterday afternoon after nearly two days of closure.

　　Beijing News reporter Pei Jianfei Liu Mingyang Sun Zhao