1.1 Steel material

 Many achievements have been made in the use of new materials in China, such as the formulation of technical standards for weather resistant steel, and the existing products of Baosteel, such as standardizing the performance of thick plates, stipulating “steel plates with thickness direction performance”; adding Q420 grade steel to the newly revised steel structure design code, etc.The use of these new materials is of great significance to save steel. For example, the use of high-efficiency steel such as H-beam and cold-formed steel can save 20% of steel consumption, which will definitely bring obvious economic significance. 

However, with the high-rise and large-scale structure, the thickness of steel used gradually increases, and China is also an earthquake prone area. It is urgent to improve the weldability (welding performance) and seismic performance of building steel. From this point of view, there is still a big gap in the types, performance and specifications of building steel between China and foreign advanced countries.

 Take Japan as an example, the following steel products developed by Japan are all in the forefront of the world:　　

 　　(1) High strength steel. 590n () and 78on().Taking the 22 story frame structure as an example, 590n steel can save 10% ~ 20% steel than sn490. 　　

 　　(2) Weathering steel (FR steel) is made by adding other elements into ordinary steel, and its heat resistance temperature is 600 ℃ (the general steel is only 350 ℃. At this time, the strength drop is not more than 1 / 3, and the bearing capacity can still be maintained in consideration of long-term load).It is possible to use this kind of steel without fire retardant coating for buildings with less combustible materials and larger space, gymnasiums and museums, thus saving a lot of investment.  　　

 　　(3) Very mild steel.The so-called very soft steel, that is, the yield point of mild steel, its chemical composition is close to pure iron, alloy elements are very few, after rolling through annealing and other heat treatment measures to soften.This kind of steel is mainly used for shock absorption structure. According to the research in Japan, the damping measures made of extremely soft steel have the advantages of low price, stable performance and good fire resistance compared with various damping methods. 　　 　　

1.2 Hot rolled section steel

 In addition to the traditional angle steel, channel steel and I-section, hot-rolled H-beam (parallel wide flange I-beam) has also become a common section in recent years.Hot rolled H-beam is a kind of economic section steel. Compared with ordinary I-beam, the flange is wider, the lateral stiffness is larger, and the moment of inertia around the weak axis is generally more than double. The internal and external surfaces of the flange are parallel, which is convenient for mechanical processing, structural connection and installation. The steel consumption of steel structure components can be reduced by 6% ~ 17%The specification has been listed in the hot rolled H-beam.At present, Ma’anshan Iron and Steel Co., Ltd. and Laiwu Iron and Steel Group Co., Ltd. have been able to roll three types of high-quality hot-rolled H-beam with section height of 200-700m, which conforms to the model series specified in the national standard hot-rolled H-beam and some T-shaped steel (GB / t11263-1998), which fills the blank of steel products in China and provides optional materials for industrial and civil buildings in China. 

　1.3 Thin wall plate　　

 Profiled color steel plate was introduced in the late 1950s. It is made of 0.5 ~ LMM thick steel sheet into serrated shape.It has a certain bending capacity. It can be used as the formwork of profiled steel sheet for non load bearing components. It can also be used as a working platform without scaffolding. Its economic performance and safety are obvious, and the construction period can be greatly shortened.The composite board composed of thermal insulation material (polyurethane plastic) and profiled steel sheet has a wider range of application. As an external wall panel and roof panel, it is widely used in light-weight workshops, with a white weight of only 10kg / m2.After pouring concrete on the profiled steel sheet, it can be used as the floor layer. The profiled steel sheet is not only the tensile reinforcement of the floor, but also can replace the formwork, and can be used as the fire-resistant component without fire-resistant coating.The composite slab composed of profiled steel sheet and concrete is a kind of floor form with good construction and good economy, which has become the mainstream of steel structure building floor at present. 　　

 At present, compared with the similar products abroad (such as BHP, ABC and Butler, etc.), the products produced by domestic manufacturers are more in quantity, but the quality is different. In terms of durability (durability refers to that the board will not peel off, crack or fade within a reasonable period of time) and fade resistance (which is very important for areas with strong sunlight, because ultraviolet radiation often damages deeper colors,There is no advantage in red and blue.We are in urgent need of our own postgraduates to produce plates that can compete with similar products from abroad to meet the demand of this global market.

 　　1.4 Thermal insulation and thermal insulation materials　　

 With the development of the times, people’s energy-saving requirements for buildings are gradually improved.From the past history, the problem of thermal insulation is not a headache in the steel structure construction industry, but people still complain about the lack of thermal insulation.The way to solve the problem of thermal insulation is to use thermal insulation materials, which are used to slow down the heat conduction by retaining static air through the insulation medium.The main difference between different types of insulation materials lies in how they are realized. They are: glass fiber insulation cotton felt, rigid thermal insulation material (foam board), sandwich foam board and spray thermal insulation material.The thickness and type of thermal insulation materials have great influence on the thermal performance of buildings.In this section, the concept of “condensation” has to be mentioned.When the hot air is cooled or meets the cold surface, it will lose part of the water vapor, which will cause the condensation phenomenon, which will lead to corrosion and mildew on the metal surface, thus losing the heat preservation performance and destroying the surface layer.At present, the way to solve this problem is to install waterproof steam facing on the warmer surface, which can slow down the speed of water vapor movement, especially for humid areas or houses with moisture emission.

 　　1.5 Anti rust and anti-corrosion materials 　　

 One of the disadvantages of steel structure is poor corrosion resistance.Generally, the newly built steel structure should be repainted at certain intervals, resulting in high maintenance cost of steel structure.At present, the methods to solve the problem of anti-corrosion are as follows: spraying antirust paint on the surface of steel structure components and using weathering steel which is not easy to rust.The coating used for anti rust and anti-corrosion of steel structure, the derusting grade of steel surface and the structural requirements of anti-corrosion on steel structure shall comply with the provisions of the current national standards “code for design of corrosion protection of industrial buildings” and “rust and anti-corrosion grades of steel surface before coating” (gb8923).The required anti rust grade of steel and the coating (or coating) and coating (plating) thickness shall be indicated in the design documents.During the design, new steel grades with better performance should be considered comprehensively, such as the type of base material, surface rust removal grade, coating structure, coating thickness, coating method, service condition and expected corrosion resistance life, so as to improve and improve the steel quality.

 　　1.6 Fireproof materials　　

 One of the disadvantages of steel structure is poor fire resistance (heat resistance is not fire resistance). In fire, unprotected steel structure can only last about 20 minutes.This was fully proved by the collapse of the world trade center in the “9.11″ incident.At present, the methods to solve the problem of fire prevention are as follows: spraying fire retardant coating on the surface of steel structure components, or wrapping concrete or other fireproof materials outside the steel structure.This is also one of the reasons for the high cost of steel structure, part of which hinders the development of steel structure.The fire protection of steel structure should meet the requirements of the current national standard “fire protection design of buildings”. The fire protection layer of structural components should be designed according to the fire protection rating of buildings.The performance, coating thickness and quality requirements of fire retardant coating shall comply with the provisions of the current national standard “general technical conditions for fire retardant coatings for steel structures” and the current standard “technical specification for application of fire retardant coatings for steel structures” (cecs24:90).