Why did the bridge fall into the river and the bridge guardrail did not stop?

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 Why did the bridge fall into the river and the bridge guardrail did not stop?


Lu Yuanshi was set up between the sidewalk and the driveway in Yangtze River bridge, Wuhan.

Yangtze Daily News recently, Chongqing Wanzhou bus crash incident continued to ferment, people in sorrow and anger, but also caused the bridge industry to think about this incident.

After the incident, people and netizens questioned the protective performance of the bridge guardrail. In this regard, the Changjiang Daily reporter interviewed many industry experts, carried on the explanation.

The main barrier is defensive line.

Curb stone between sidewalk and carriageway

It is reported that the second Wanzhou Yangtze River Bridge was built and opened to traffic in 2003. It is a two-way four-lane bridge with a speed limit of 60 km/h. It belongs to the urban bridge.

Tian Qixian, president and general manager of China Railway Bridge Science Research Institute, said that on urban bridges, there are roadside stones at the junction of both sidewalks and roadways. The main function of this defense line is to intercept vehicles and prevent them from bumping into pedestrians or hitting bridges. The most lateral guardrail of the bridge is mainly used to protect pedestrians, and the ability to resist collisions is weak.

Therefore, a very strong anti-collision wall or guardrail should be set up at the curb stone. Only a row of steel tube-type metal guardrail is installed on the curb stone of Wanzhou Second Yangtze River Bridge. The whole height is relatively low, and its height, strength and stiffness do not meet the requirements of the code.

Take the bridge in Wuhan as an example, there are curb stones and anti-collision barriers between the sidewalks and motor lanes of Wuhan Yangtze River Bridge, and a higher curb stone barrier between the Second Yangtze River Bridge, while the Nautilus Yangtze River Bridge in Wuhan has stronger protective capacity, with steel barriers in the middle of the bridge, and barriers between the sidewalks and motor lanes on both sides. And the wall.

It can be seen that many bridges are equipped with a central dividing belt, which can play a buffer role for the coming vehicles.

What standards should be adopted for bridge design guardrail?

As a highway engineering industry standard, the Code for Design of Highway Traffic Safety Facilities (JTGD81-2017), which has been implemented since this year, clearly stipulates that bridge guardrails and balustrades must be installed at roadside Guardrails for all levels of highway bridges, and that central partition barriers must be installed for highway bridges and primary highway bridges as secondary trunk lines. A central divider fence should be set up for the main highway bridges.

At the same time, when the design speed of highway bridges is less than or equal to 60 km/h, the pavement and the roadway can be separated by curb stones, while when the design speed is greater than 60 km/h, the pavement and the roadway should be separated by the bridge guardrail. The design of the second Wanzhou Changjiang bridge is 60 kilometers per hour.

According to the Urban Bridge Design Criteria (CJJ11-93) of Wanzhou Second Yangtze River Bridge, the design of pedestrian road margin height should be 0.4 meters. Whether the margin height can reach 0.4 meters remains to be verified.

Early design of bridges to update safety precautions

According to Dr. Zhang Fang, Department of Bridge Engineering, Southwest Jiaotong University, the impact of lateral driving or collision on bridges and driving safety under sudden vehicle accidents was not fully taken into account in the early regulations. On the premise that the bearing capacity of bridges is allowed, measures such as adding anti-collision barriers can be taken to reduce the occurrence of this kind of situation for bridges designed earlier. At the same time, the design of the new bridge should be in accordance with the latest specifications and fully consider the impact of contingencies.

An industry expert who did not want to be named also said that the design specifications of urban bridges and road traffic safety facilities were constantly updated, and urban bridge management units should also update the corresponding bridge safety protection measures to meet the new specifications.

The introduction of health monitoring in Wuhan will check the safety of ancillary facilities of Urban Bridges

Tian Qixian introduced that his Academy of Bridge Sciences is a research institution specializing in bridge health monitoring. At present, it mainly focuses on the safety of main structure of bridges. Next, when they carry out health monitoring of bridges in Wuhan and other cities in China, they will pay attention to and check whether the strength, stiffness and height of ancillary facilities such as guardrails are satisfied. Demand, if the standard is low, will take certain measures. It is reported that 60 bridges in Wuhan have been connected to the health and safety monitoring system this year, covering all 694 urban bridges in the city in five years. Xu Gongyi, Deputy Engineer of China Railway Bridge Survey and Design Institute, said that the anti-collision ability of a bridge guardrail is related to traffic flow, driving speed, external conditions, bridge structure and other factors. Usually, the higher the traffic flow and the faster the speed of the highway bridge, the higher the requirements of the anti-collision grade and anti-collision ability of the bridge guardrail. The guardrail has the function of prevention and protection, but any bridge guardrail can not be said to resist accidental impact under all circumstances. That is to say, it is difficult to specify how many tons of vehicles impact the bridge guardrail at what speed, so as to ensure that there will be no river crash accident. Source: Changjiang Daily editor: Guo Ping _B7442

Tian Qixian introduced that his Academy of Bridge Sciences is a research institution specializing in bridge health monitoring. At present, it mainly focuses on the safety of main structure of bridges. Next, when they carry out health monitoring of bridges in Wuhan and other cities in China, they will pay attention to and check whether the strength, stiffness and height of ancillary facilities such as guardrails are satisfied. Demand, if the standard is low, will take certain measures. It is reported that 60 bridges in Wuhan have been connected to the health and safety monitoring system this year, covering all 694 urban bridges in the city in five years.

No bridge guardrail can block all accidental impacts.

Xu Gongyi, a master of national engineering survey and design and Deputy Engineer of China Railway Bridge Survey and Design Institute, said that the anti-collision ability of bridge guardrail is related to traffic flow, driving speed, external conditions, bridge structure and other factors. Usually, the higher the traffic flow and the faster the speed of the highway bridge, the higher the requirements of the anti-collision grade and anti-collision ability of the bridge guardrail.

The guardrail has the function of prevention and protection, but any bridge guardrail can not be said to resist accidental impact under all circumstances. That is to say, it is difficult to specify how many tons of vehicles impact the bridge guardrail at what speed, so as to ensure that there will be no river crash accident.