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

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

The 21st century economic report reporter saw at the edge of the innermost warning line that from time to time, many large-scale muck trucks loaded with construction waste were withdrawn from the scene of the accident in turn. At the farthest sight, large construction machinery was crushing the collapsed bridge debris. The sudden sound could be transmitted beyond 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, overload is often the most direct fatal factor.

The rescue scene of the overturning accident of the viaduct in Wuxi, Jiangsu Province, was taken 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 the 21st century economic reporter by telephone that after the accident on October 10, the Ministry of transport immediately sent an expert group to the scene to guide the accident investigation, and Wuxi also set up an accident investigation group.

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.

Its plain carbon steel with a wide range of uses. Its much heavier than the stainless steel coils we normally do business with. An owner of a steel trade market near the site of the accident told 21st century economic reporters.

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?

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 single weight, the more money.

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?

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.

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.

Many road and bridge designers interviewed pointed out that, from the perspective of practice, the damage of overloaded vehicles to bridges is irreversible, which is the fundamental reason why the original bridge with a design service life of 50 years has become a dangerous bridge after 20-30 years. If the problem of truck overload is not systematically solved, the annual bridge maintenance cost 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.

Source: Responsible Editor of Economic Report in the 21st Century: Chen Hequn_NB12679