In recent years, the application of steel structure building is more and more common in various industries, whether it is high-rise building structure or large-span bridge and various industries, it can be used as the main construction component of the frame, or as a single supporting structure part, which can be used on different parts according to the demand.Steel structure engineering types can be divided into a variety of types, can be overpass, canopy, attic, can also be steel structure engineering, warehouse, office building, as long as it is necessary to use the steel structure part of the structure, can be used as steel structure engineering. 

Steel structure engineering has many advantages, such as elegant shape, bright color, diversified building shape, low cost, short construction period, high degree of factory production of steel components, simple installation and construction, flexible plane layout. At the same time, steel has many advantages, such as light weight, uniform material, convenient design and calculation, recyclable and so on. It is more and more widely used in modern industrial steel structure engineering.But the steel structure engineering also has a fatal shortcoming is not fire resistant.Although steel is nonflammable material, under the action of open fire and high temperature, with the increase of temperature, its mechanical indexes will change greatly. The bearing capacity and equilibrium stability will greatly decrease with the increase of temperature. At about 500 ℃, the reduction is more obvious. Generally, it will collapse due to loss of bearing capacity in about 15 minutes. 　　

 Therefore, protective measures should be taken for building steel structure engineering.The first is to protect the steel members themselves against fire, so that they will not exceed the critical temperature rapidly when the fire temperature rises, and the steel structure can also ensure the stability and the safety of personnel and property within the specified time; the second is to set an effective fire prevention zone inside the industrial steel structure project to prevent the fire from spreading and spreading to other areas. 　　

 1、 Fire protection of steel members in steel structure engineering 　　

 Because the steel member itself has reached the non-standard fire resistance limit, it is necessary to take corresponding fire-resistant protection measures for steel members.The commonly used fire-resistant protective measures include fire-retardant coating method, foaming fire-proof paint method and external fire-proof layer method 　　

　1.Fire retardant coating method 　　

 Fire retardant coating method is to spray fire retardant coating on steel structure to improve its fire resistance.At present, fire retardant coatings for steel structures in China are mainly divided into thin coating type and thick coating type, namely thin type (B type, including ultra-thin type) and thick type (H type).The thickness of the thin coating is below 7mm. It can absorb heat and expand foam in fire, and form a foam carbonized insulation layer, thereby preventing heat from transmitting to the steel structure, postponing the temperature rise of the steel structure and playing the role of fire protection.Its main advantages are: thin coating, light load on steel structure, good decoration, coating on small area of complex shape of steel structure surface is easier than thick type; thick coating thickness is 8-50 mm, the coating is heated without foaming, relying on its low thermal conductivity to delay the rise of steel structure temperature, so as to play the role of fire protection.Both of them have different performance characteristics and are suitable for different occasions. However, no matter what kind of products, they should be tested by national testing institutions before they can be selected. 

Fire retardant coating spraying of steel components in steel structure engineering

On the fire retardant coating spraying must pay attention to a few points

 　　a. The coating is too thin

 The purpose of spraying fireproof coating on steel structure is to improve the fire resistance of steel structure.The performance index of steel structure fire resistance is closely related to the spraying thickness.For the same kind of fire retardant coating, the thickness of spraying is different, and the fire resistance limit is also different.If the thickness of fire retardant coating for steel structure is not sprayed according to the design requirements, the fire resistance limit of steel can not meet the requirements of fire protection.According to statistics, the spray coating is too thin, and this kind of problem accounts for 25%.

 　　b. There are papillae on the spraying surface

 In order to ensure that the coating surface is even and flat, and the spraying thickness also meets the requirements, steel structure engineering, article 3.4.5 of “technical specification for application of fire retardant coating for steel structure” clearly requires that the coating after spraying shall be removed of mastoid to ensure uniform and smooth.

 　　c. Wrong selection type

 Different types of fire retardant coatings have different thickness on steel structure, and their fire resistance is also different.In order to ensure the fire resistance of the steel structure to meet the fire protection requirements, different types of fire retardant coatings should be sprayed on different parts of the steel structure.If the wrong type is selected, even if the spraying layer reaches the thickness, it will not meet the fire protection requirements.

 　　2Foam fire retardant paint method

 Foamed fireproof paint is a kind of flame retardant coating made of film-forming agent, flame retardant, foaming agent and other materials.The difference is that the film itself is not easy to burn after it is dried. When it is exposed to fire, it can delay the flame to burn to the combustible materials, so it has a certain fire resistance performance.According to the test: the general paint and fire-retardant paint are respectively painted on the wood board, and after drying, they are baked with the same flame. The wood plate coated with general paint will scorch with the paint in less than 2 minutes; while the board coated with non expansive fire retardant paint only has smoldering phenomenon after 2 minutes, and it will extinguish immediately after standing for 30 seconds;Even if the boards were baked for 15 minutes, the smoldering phenomenon did not appear.It can be seen that fire-retardant paint applied to the surface of objects can prevent the spread of fire in a certain period of time and protect the surface of objects in case of fire, so as to take precious time for extinguishing fire.

 　　3External fire protection layer method

 The outer fireproof layer method is to add an outer layer on the surface of steel structure, which can be cast-in-place or sprayed.In order to limit the shrinkage cracks and ensure the strength of the shell, steel mesh or reinforcement is usually used to strengthen the outer layer of solid concrete.Spraying method can spray lime cement or gypsum mortar on the surface of steel structure at the construction site to form a protective layer, and can also be mixed with perlite or asbestos.At the same time, the outer layer can also be made of perlite, asbestos, gypsum or asbestos cement, light concrete, and fixed on the steel structure with adhesives, nails and bolts.

 2、 Fire compartment of steel structure engineering

 Fire compartment refers to the local area (space unit) divided by fire separation measures, which can prevent the fire from spreading to the rest of the same building in a certain period of time.When the fire breaks out in the building, the fire can be effectively controlled in a certain range and the fire loss can be reduced. At the same time, it can provide favorable conditions for personnel safety evacuation and fire fighting.The common methods of fire compartment are to set up fire wall and set up independent water curtain. However, due to the particularity of industrial steel structure engineering, both methods have shortcomings.

 　　1, firewall

 Using firewall to separate steel structure engineering to control fire spread is a common method in civil buildings. However, in industrial steel structure engineering, not only because the large space of steel structure engineering is divided will affect its permeability, but also from the perspective of production process continuity and logistics organization in steel structure engineering; from the Perspective of production management, it is not conducive to production management. 

Firewall materials used in steel structure engineering

　　2Independent water curtain

 The water curtain can act as a firewall. It is a very good plan to use the independent water curtain as the fire prevention partition.Sprinkler heads should be used for fireproof water curtain and rain shower sprinklers.The arrangement of water curtain nozzles shall not be less than 3 rows, and the width of water curtain formed by fire-proof water curtain belt shall not be less than 5m.This kind of separation method is flexible, unlike the firewall which needs to cut off the workshop, theoretically any large span can be used.In normal production, as if it does not exist, once there is a fire need fire separation, it can immediately achieve effective separation.However, the independent water curtain for fire division also has shortcomings: firstly, the water demand is large; secondly, the fire in steel structure engineering is often local at the beginning, and only a few fire extinguishers can solve the problem. At this time, if the water curtain is started, the production equipment will be damaged, and the loss caused by this is greater than that of local fire.Therefore, it is necessary to strictly control the starting time of the water curtain to prevent misoperation, so it is more appropriate to use manual starting in the design; there is also the trouble of effective maintenance.

 3、 Summary

 To sum up, it is common to use fire retardant coating method and independent water curtain respectively for fire protection and fire compartment of building steel structure engineering. However, due to the production needs of steel structure engineering, each method has its own disadvantageous place in practical application.We still need to continue to explore in practice, in order to find better fire prevention measures, in hardware to protect personnel and property safety.

 HongJiShunDa Steel Structure Co., Ltd. is engaged in steel structure engineering, construction engineering, steel member processing and export, steel structure workshop construction design and other types of engineering.Three dimensional steel structure is a company with more than ten years of steel structure engineering experience. It is a set of steel structure design, processing, installation, maintenance, anti-corrosion, and other aspects in one, to provide you with one-stop construction services.Professionals to do professional work has always been the purpose of three-dimensional, will be able to build high-quality building steel structure engineering.