Behind Wuxi Viaduct Collapse Accident: Fatal Overload and Struggle of Vase Pier

 Behind Wuxi Viaduct Collapse Accident: Fatal Overload and Struggle of Vase Pier

On the afternoon of October 11, rescue work for the collapse of Wuxi viaduct was still in progress in an orderly and tense manner. With Wuxi viaduct collapse accident as the central point, traffic control under the command of the investigation team presents a multi-level. The advantage of this method is that the most peripheral traffic policemen can distribute the vehicles according to the command of the different destinations of the vehicles, so as to make the traffic more orderly.

Economic reporters in the 21st century saw at the edge of the innermost warning line that from time to time a number of large dregs trucks loaded with construction waste were evacuated from the accident site in turn. At the farthest distance from sight, large construction machinery was crushing the debris of collapsed bridges. The loud noise of sudden burst could be transmitted to the second warning line.

Reporterson-site visits and vehicle-borne traffic radio broadcasts show that the local traffic has remained unimpeded as a whole, with only a few road vehicles near the accident site more, but the traffic is slow and not disorderly.

According to the preliminary analysis of Wuxi Accident Investigation Team, the overturning of the overpass bridge is caused by the overloading of transport vehicles. The accident resulted in three deaths, two injuries and eight vehicles damaged. This is not the first accident of urban viaduct collapse in China. As can be seen from the existing cases, overloading is often the most direct fatal factor.

The rescue scene of the overturning accident of Wuxi viaduct in Jiangsu Province was photographed on October 11. - Xinhua News Agency

Fatal overload

At present, there is not much information to announce to the public. According to the emergency mechanism, we should wait for the conclusion of the investigation team. An official of Wuxi Municipal Government told 21st Century Economic Reporter by telephone that the Ministry of Transport dispatched a team of experts to the scene immediately after the accident happened on the evening of October 10 to guide the accident investigation. At the same time, an accident investigation team was set up in Wuxi.

According to the news released in Wuxi on the morning of October 11, the accident was caused by overloading of vehicles. From the scene photos, there are large trailer trucks and many large volume steel coils loaded or scattered. It is estimated that the combined weight of goods carried by the trucks exceeds 170 tons.

In the vicinity of the accident, there are many large steel market. An owner told reporters that it is normal to overload steel vehicles on the market, but if large tonnages of goods are encountered, logistics companies will be reminded not to go overhead. From the local traffic routes, we can see that if we walk from the ground passage under the elevation, there will be a traffic light, which will take 3-5 minutes more than the direct passage from the elevation.

Heavy weight is a typical feature of steel transportation. Special trucks must be used. Why is overloading normal?

This is because most steel transactions are based on weight to pay freight. Therefore, for steel logistics enterprises, the subjective choice is to reduce the number of times of transportation through overloading to increase profits. Usually, there are two kinds of situations: for goods under 20 tons, we will use the argument, that is, how much money is to be pulled at a time, but this should be a matter of friendship, occasionally; for goods over 20 tons, we will use weighing.

According to the 21st Century Economic Reporter, the local steel market for short-haul transportation of stainless steel, the general market price is: the price of the discussion is 200 yuan per time; weighing price is 8-10 yuan per ton. For transporters, the cost of each round trip is the same, and in order to get more profits, they tend to weigh more. Therefore, the heavier the weight, the more money you make.

It is worth noting that in the field of highway transportation, before toll highway was popularized in China, the flow of logistics people mainly relied on national highway. National Highway runs through the city. Later, with the development of economy, especially in the improvement of urban traffic quality, most of the national highways in cities choose to improve and optimize the traffic pattern by laying elevated buildings without changing their original uses. At this time, in the vicinity of the connecting point kilometers, there are often traffic signs to remind the vehicles whether they need to change lanes, etc., to divert the vehicles.

On the one hand, we should strictly check overload, and on the other hand, we should take the excellent traffic environment as the driving force for economic and social development. It is also very difficult in our practical work. On the afternoon of October 11, a person driving a yellow-marked traffic engineering vehicle told 21st century economic reporters that they had been drawn from the suburbs to take part in the rescue work outside the warning line where the accident occurred. At present, there are a lot of vehicles in local transit. Checkpoints are usually located at the junction. If overload checks are carried out strictly, the possibility of traffic paralysis will be great, which will bring a large number of complaints from residents.

Overloading is the most important cause of the collapse of the elevated structure. What about the design of the elevated structure?

The temptation of vase pier

Some people engaged in road and bridge design professionals told the 21st century economic report reporter that from the comparison of the scene photos, it can be seen that the design vehicle load of the elevation at the accident site is 55 tons, and the design has been open for more than 10 years.

By comparison, it is found that the accident elevated structure is a single-pillar pier structure (commonly known as vase pier), with a support in the middle, but the road supported on it has been expanded. According to the Code for Design of Highway Reinforced Concrete and Pre-Sensitive Concrete Bridges and Culverts approved by the Ministry of Transportation in 2018 (hereinafter referred to asnew code), two supports should be set in theory. These people said.

The advantage of using vase pier is that it can effectively meet the bridge design principles of economy, environmental protection, applicability and safety in a specific historical period under the condition of limited economic development, so as to obtain the most economical construction cost.

Unlike the old code, the new code has been supplemented by new experience and new research results in the past 10 years, such as overturning checking. The calculation principle, calculation method and safety factor requirements are explained in detail.

At present, Wuxi Municipal Government has not published the design drawings of the incident viaduct to the outside world, so it is impossible to judge whether the viaduct meets the anti-overturning safety factor of the new code. Moreover, the 2004 edition of the Old Code does not specify the requirements for anti-overturning. If the anti-overturning calculation according to the new code is satisfied, it has nothing to do with the designer.

In response, on the evening of October 11, an official of the Wuxi Municipal Government told reporters of economic reports in the 21st century that the expert group meeting of the Ministry of Transport organizes a review in the name of an authoritative third party.

Many road and bridge designers interviewed pointed out that in practice, the damage caused by overloaded vehicles to bridges is irreversible, which is the fundamental reason why bridges with original design life of 50 years have been in danger for 20-30 years. If the problem of overloading of trucks is not solved systematically, the annual cost of bridge maintenance is huge.

These people point out that at present, local governments should check the viaducts built in the history of cities with reference to the new norms, especially re-check the overturning resistance of single-column pier structures. For those structures that do not meet the safety factor requirements, different structures should be reformed.

Five questions about the overturning accident of viaduct: Who is the design in the end? No one cares about the overload?

For the cause of the accident, the official preliminary analysis is that the overload of transport vehicles caused. But for the moment, there are still some questions to be answered.

Media: Its time for tragedy to repeat itself and re-examine the punishment of overloading trucks

Heavy truck overloading is not a new problem, nor is it a new topic in the public opinion field. The accident in Wuxi shows that the overloading of large trucks not only aggravates the general traffic safety risks, but also poses a major threat to the traffic infrastructure and the life safety of pedestrians. In the face of repeated tragedies, it is time to reexamine and evaluate the damage caused by overloading of large trucks and take corresponding measures to deal with it.