Collapse of Steel Silos

Sometimes, collapse accident would happen to the steel silos. According to statistics, these steel silos basically belong to building materials enterprises, or fly ash storage and transportation enterprises, that is, concentrated in the steel silos that storage powder materials. Most of the collapsed steel silos are concentrated in the regions with low temperature, but in some areas where the temperature condition is good, the collapse of the steel silo may also occur. At the same time, it is also founded that the steel silo may be deformed and cracked. What's the reason exactly? And how to prevent the steel bin from collapsing? This article will explore the cause and put forward the countermeasure .

The cause of the collapse of the steel silo

Low temperature environment impact

Based on the analysis of the time of the steel bin collapse in recent years, it is true that most of the collapses occur in winter, and in the coldest period of winter in which the temperature changes drasticly. Therefore, from the point of view of intuitive analysis, people think that steel silos are frozen, and are always attributed to unreasonable selection of steel plates. Q345 series steel plate and low temperature plate are better than Q235B plate, but they are not the main cause of the accident. Cryopreservation is only an inducement. Is the steel silo collapsed because of frozen? Is it because of the selection? Of course not.
If the low temperature is so severe, for the group of steel bunkers where several steel warehouses are together, their materials, environment, construction, and use conditions are almost the same, why not collapse at the same time, but only a part of them?Why do steel silos accidents mainly occur in the building materials industry,but not in the grain or oil industry which have the same large use of steel silos?
Therefore, there are other more critical reasons for the collapse of steel storage, of course, the low temperature environment undoubtedly contributed to the rapid collapse of steel storage.

Insufficient design strength

Based on the analysis of collapsed steel silo, it is found that the design strength of most of them is seriously inadequate. Many of these steel silo have serious deficiency, especially in the stability. The reason is that the designer does not understand the material characteristics, and the design parameters are not correct in the design. This leads to surface clearance of the design, but the actual strength is insufficient. Of course, the design of some steel warehouse projects is caused by market competition, the designers know that the strength is not enough, but according to experience, they think they can be lucky to pass the test. The failure of design resulted in a huge hidden danger of safety in the steel silo.

Unreasonable structure and improper selection of load index

The external appearance of the steel silo is nothing but a storage container, in fact, because of the different materials stored in the silo, the force on the steel silo wall is different. In particular, the material characteristics of industry building materials are all in big difference, do not distinguish design, can not meet the requirements of safe use. For example, clinker steel storage is not necessarily suitable for cement storage, not necessarily suitable for the storage of fly ash. In short, the design must be based on material characteristics.
Every steel silo should be designed not only according to material characteristics, but also according to the characteristics of building materials industry.
The steel silo in building materials industry is different from that in grain and oil industry. For example, the roof of steel silo in petroleum industry only needs to consider other loads such as wind load, snow load, deadweight load and so on. In addition, building materials industry also has a lot of equipment load, corridor load, overhaul load, ash load and so on. If the designers do not understand the characteristics of these loads, it will inevitably lead to insufficient design strength of the silo wall, leaving a hidden danger of safety. From the steel silo drawings which collapsed, we can see that they have a lack of consideration in this aspect.
The structural design of the steel silo is not only safe if the structure of the steel structure part is well designed. If the foundation design is unreasonable and the connection form between the foundation and the steel silo is improper, then when the extreme low temperature is encountered, Due to structural constraints, the possibility of silo damage will be increased. Another important reason is that many large steel silo structures under 20m are used in the design of large steel silo, which results in that the accident usually happens to the less than 20m steel silos.
Many of these steel silos were not full of material when they collapsed, and some were loaded at less than 1/3. Because of the serious shortage of strength and unreasonable structure of these silos, the demand for local strength increases sharply when the sharp low temperature occurs. Therefore, when the steel silo exceeds the strength limit, the structure is destroyed and the collapse is inevitable.

Material selection is unreasonable

At present, most steel silo uses ordinary Q235B steel silo, and it is safe to use, but this does not mean that it is not proper to use steel silos under low temperature. On the contrary, some of the steel silos that have collapsed would have used low temperature steel plates at that time. These steel silo can avoid collapse. At low temperature, the coefficient of cold shrinkage of steel plate is smaller than that of common plate when the structure is defective, the stress increase is smaller, the force of damage is much smaller, and at the same time, The low temperature "cold embrittlement" phenomenon will not appear in the steel plate in the range of service temperature. And the possibility of structural failure will be greatly reduced. Therefore, in the process of building and strengthening the steel plate warehouse in the low temperature area, it is suggested that the low temperature steel plate should be used. In particular, the selection of Q 340 series of low-temperature steel silos is both safe and very beneficial to reduce the cost.

Lack of construction quality

In recent years, due to the rapid construction of steel silo, construction management is not in place.
In addition, some construction units are not fully prepared in advance and want to be put into use as soon as possible, resulting in construction units unable to carry out construction at normal speed and difficult to ensure quality. On the other hand, due to the uneven technical level of construction units, Construction units in order to save investment, choose low-price units, further leading to a decline in the quality of the project. Therefore, if there are several steel silos built at the same time, the fastest built silo would collapse first, the silo which the quality is a little better collapses later. In this case, even if the front design, material selection are all done well, then the construction quality control is not strict, accidents may still happen to the steel silos.

Improper use

Improper use is also one of the causes of the accident in the steel silo. Some unit steel storehouses will increase the load on the silo, such as adding equipment to the top of the warehouse, adding load on the corridor, and increasing the loading (mostly due to the rich volume of the design and the insufficient strength and insufficient strength), the loading of the silo and the opening of the silo, such as the collapse of a 40 thousand ton steel storehouse designed by a unit. During the accident, the loading capacity of fly ash may reached 60 thousand tons. These practices increase the probability of accidents and need to arouse our alert.