In recent years, steel structure residential buildings are being developed all over the country. The research and application of green and energy-saving building system of steel structure has gradually become a national key research topic. From the perspective of developed countries, steel structure building has become the mainstream. Among them, the high-rise steel structure has a history of 110 years. Thousands of consultancy in China, published by the steel structure processing market investigation and analysis report, in the European and American countries, steel structure residential building has accounted for about 65% of the total construction, 50% in Japan. At present, the United States, Japan, the United Kingdom and other countries are actively promoting prefabricated and assembled steel structures in low – and medium-rise housing.
1.The United States
In view of the development history of American market, the steel structure industry has experienced a process from decentralization to centralization, with increasing concentration. After many acquisitions and reorganizations, nearly half of MBIVIA’s members are now in the NCI, Nucor and B1ue Scope groups.
There are two mainly reasons for the increase of concentration of steel structure industry: (1)As for the spatial steel heavy steel structure building, general contractor requirements to undertake business with first-class construction qualification and excellent projects performance, thus forming a competition that good enterprise with good projects accumulation to be the stronger; (2) the transportation cost of steel structure products is high, and enterprises with a nationwide layout can grab a larger market share. The weight and volume of steel structure products are large, and the long-distance transportation will bring high transportation cost, which has certain economic radius. According to statistics, the economic transportation radius of steel structure processing points is 700-1000 km. Therefore, enterprises with a national layout can reduce costs and seize market share.
2.The United Kingdom
The UK steel construction industry is worth 3.5 billion pounds a year (about 5 per cent of UK construction activity), employs about 42,000 people and steel usage of 1.2 million tons a year. Especially for multi-storey buildings, the construction speed is the first reason to choose steel, and the second reason is the ‘lowest overall cost’. Steel accounts for 70 per cent of the market, with multi-storey industrial houses (92 per cent) and single-storey homes (90 per cent) for non-residential. 95 per cent of construction steel in the UK is recycled, 10 per cent is repeatly to use and 85 per cent is recycled.
Before the 1980 s, Japan produced only 200 mm x 200 mm square rectangle tube and a small amount of opening cold bend steel, steel structure housing in Japan post adopt H-beam. After the 1984 earthquake in Sendai, Japan, through the research of Sendai earthquake encountered in the sabotage of the steel structure housing, found the welding seam cracking between the column and beam, the reason is limited by H-beam shape characteristics, using H-beam and H-beam welding, the welding seam is too little. As a result, Japan modify the building law, require Japan’s steel structure residential pillar must use square or rectangle tube, in order to increase the length of the welding, thus improve the shock resistance of the residence. Then cold bending section steel structure was largely produced and applied in Japan. In 2002, cold bend steel structure steel and round pipe amounted to 2 million tons in Japan. So far the largest steel market demand is 200 mm * 200 mm, 400 mm * 400 mm steel pipe; The specifications of the cold bending torque tube account for over 80% of the Japan’s square and rectangle tube market, and other specifications product market share of less than 10%.
There are several kinds of new building steel developed by some Japanese steel companes:
One is SN steel. It is a kind of newly developed steel for building steel structure. Advantages: Ensure plastic deformation ability;Ensure welding ability; Ensure the performance of plate thickness direction; Ensure nominal sectional dimensions; Can be selected different steel according to different parts; its performance and steel grade distinction: the yield point upper limit, yield ratio upper limit, thickness direction drawing value lower limit value, (charpy impact value lower limit value, carbon equivalent (ceq) welding crack sensitivity (PCM) upper limit, minus tolerance precision strict regulations. At present, the application of SN steel in large buildings is increasing and its development prospect is promising. However, some small and medium-sized buildings use more SSSM materials.
Second is the TMCP steel. Usually the JIS standard steel plate, when the thickness more than 40 mm, will affect its yield strength, but if use TMCP steel (thermal control technology), without increasing the ceq can make steel (plate, h-beam) will be with good weld ability. In Japan, this kind of steel products has been widely used in high-rise buildings, of which 400 x400mm, 500 x500mm super heavy H-beam as pillars, in the application of high-rise buildings has been quite common.
The third is ultra low yield point steel. This steel is commonly used in steel column and beam such as low yield point of suspension components. When an earthquake occurs, make its yield first, lag by repeated loading and absorb seismic energy, compared to other shock absorption material has the advantages of low cost, high reliability and durability, and therefore has been widely used in Japan.
Four is light welding H steel. In Japan, nearly all light H steel used in industrial steel structure residence, each year more than 1 million households of new residence, nearly 15% by industrialized building, is in a factory assembly line production houses. Industrialized housing manufacturers in order to improve production efficiency, put forward new requirements of accuracy of automated production equipment and materials continuously, while light H steel is with high precision than rolling h-steel, more suitable for the industrialization of residential buildings. Now Japan’s metal industries co. produce H steel more than 100000 tons a year, accounting for 80% of Japan’s industrialization residential steel market share.