Necessity of long-term preservation of steel structure engineering application
So far, the corrosion of steel structures is causing huge losses to the national economies of various countries in the world. According to statistics from some industrialized countries, the annual economic losses due to the corrosion of steel structures account for about 2% to 4% of the GNP. The U.S. economic loss due to corrosion in 1975 was about 70 billion U.S. dollars, accounting for 4.2% of the GNP of that year and up to 126 billion U.S. dollars in 1982. The British had a corrosion loss of 1.365 billion pounds in 1969, accounting for 3.5% of the GNP %. In 1976, Japan's corrosion loss was 9.2 billion U.S. dollars, accounting for 1.8% of the GNP. According to China's statistics in 1995, the corrosion loss was as high as 150 billion yuan, accounting for about 4% of the GNP. At present, the annual economic losses caused by the corrosion of steel structures in the world have reached hundreds of billions of dollars or more.
Moreover, accidents caused by corrosion of steel structures endanger the safe operation of the structure. Corrosion caused by catastrophic accidents are common, the consequences are extremely serious, especially the welded steel structure and steel under greater stress conditions, due to stress, corrosion will be greatly accelerated, that is, the so-called stress corrosion problems occur in the steel Structural damage is extremely common. For example, the bridge structure or the overhead roof structure must be rebuilt due to serious corrosion problems. Otherwise, it will have serious consequences. Of course, the investment in the economy will be quite large. At present, building a large steel bridge in China will cost at least Hundreds of millions of renminbi. In Japan, the Dalang Metro Line was broken by corrosion in 1970, a liquefied petroleum gas storage tank in a certain city of our country caught fire due to corrosion and explosion, leaving dozens of casualties and a direct economic loss of 6.3 million yuan. And, the indirect economic loss caused by the stoppage or stoppage of production caused by an accident may exceed the direct economic loss by several times.
Because of this, the use of steel corrosion technology, especially the long-term preservation of the use of new technologies is very important. If the steel structure can be exempted from maintenance in 15 to 50 years, the user will save a lot of maintenance expenses and greatly improve the safety and service life of the steel structure.
So far, the importance of long-term preservation of steel structures is still lacking in many aspects such as the users of the steel structure engineering, designers and construction parties, and they still remain in the traditional anti-corrosion technology in their consciousness. The latter part of the maintenance may not keep up.And, even in the traditional coating anti-corrosion
, due to the construction process in the anti-corrosion construction technology, but often lead to premature corrosion or destruction of steel structures. For example, in March 1965, a gas pipeline in the United States cracked and caused fire due to stress corrosion, killing 17 people. Another example is the early construction of a swimming pool paint construction engineering non-permanent corrosion, resulting in premature corrosion of the local area of the steel structure, as shown in Figure 1, coupled with the roof system design of the era of limitations of anti-corrosion technology, making use of It must cost millions to replace or maintain it.
In addition, there is a big problem for some engineering users. For example, there is no expert on anti-corrosion engineering prior to the implementation of the project to evaluate the overall anti-corrosion technology of steel structures. When the project is handed over, there is no designated anti-corrosion engineer or Experts on the quality of the entire steel corrosion test rigorous; anti-corrosion after construction sit back and relax, the latter part of the regular testing and maintenance basically no; either is to reduce the cost of anti-corrosion project regardless of the actual situation, and the construction unit combined with each other Produce unqualified "rubbish project."
When the various aspects are grouped together, the life span of the entire steel structure is certainly doubtful. So far, many steel structure damage accidents have taken place and the immediate consequences have been catastrophic, directly attesting to the above Analysis.
The reason why the long-term corrosion of steel structures called a system engineering, precisely because it involves the use of steel structure engineering, engineering design, engineering construction and supervision of parties and other aspects of a comprehensive combination of factors. Only when all aspects are properly combined and taken seriously, the safety and service life of the steel structure can be reliably guaranteed.