In China's industrial and civil buildings, reinforced concrete has been used for many years, and the construction period is long and the pollution is large. In recent years, with the successful market introduction of hot-rolled H-beam products of Maanshan Iron and Steel Co., Ltd., the application of steel structure in the construction industry has been expanding. Various steel structure laboratory buildings, model houses and sign buildings have been launched, design and construction. The standards and specifications have also entered a stage of gradual improvement. China's steel structure industry has taken a big step in recent years. However, at present, the main application of building steel structure in China
If hot-rolled H-beam and welded steel structures, the annual output of hot-rolled H-beams in China has exceeded 1.5 million tons, and the output of welded lightweight H-beams and various steel structures is also several hundred thousand tons. More than 7 million tons, of which the production of cold-formed square rectangular tubes and various cold-formed steels for construction steel structures is less than 5% of the total output of cold-formed steel. The application of cold-formed steel in the steel structure of industrial and civil construction in China is in its infancy. The cold-bent square rectangular welded pipe has just replaced the hot-rolled H-shaped steel for the steel structure. The other cold-formed steel is less used in the construction industry.
China's Ministry of Construction has already built some steel structure test buildings in industrial and civil buildings, such as two steel structure demonstration houses built in Tianjin in 2002. The project uses steel-reinforced concrete column steel beam frame - steel-reinforced concrete core tube ( SRC) Structural system, with a total area of 8 000 m2, 11 main bodies, one column with a round tube, and the other column with a square steel tube of 350 mm 350 mm. The thickness varies with the floor, with 1 to 3 layers being 16 Mm, 4~6 layers are 14 mm, 7~9 layers are 12 mm, 10~11 layers are 10 mm, and steel pipes are filled with C40 concrete. The beam is made of welded I-beam, with dimensions of 350 mm* 200 mm *10 mm*18 mm, and the slab is a high-strength spiral rib prestressed laminate. Since there were no manufacturers in China producing such large-diameter square tubes at the time, the square steel tubes used in the project were four-plate welded BOX columns.
The two steel construction demonstration projects in Tianjin's Ministry of Construction have two implications for the application of cold-formed steel (mainly structural pipes) in steel-structured houses: First, the large-scale cold-formed steel market has a large space, and the rational structure of steel-structured houses The number is 10~18 layers, and such middle and high-rise structures also have certain requirements for the specifications of cold-formed rectangular tubes. Second, the square steel tube has obvious advantages over the round steel tube. The reason is that the square and round tubes of the same side length and diameter have better bearing capacity and seismic performance. According to a university in Tianjin, the three-layer two-span square tube and the circle The test of the concrete column frame, the square tube column length is 150 mm, and the round tube diameter is 150 mm. The test results show that the former lateral force yield bearing capacity and ultimate bearing capacity are 80% higher than the latter, and the seismic performance index is about the latter. Twice; second, square tube construction is more convenient. The round pipe concrete column of the steel structure house generally needs further construction, and the round section is changed to a square shape. Third, the use of round pipe concrete columns, the connection with the beam is more difficult to handle. In the future steel structure market in China, cold-formed square rectangular tubes will occupy an important share.