Compared with the structural form of traditional residential buildings, steel structure is a new structural form that is most in line with the characteristics of "green building", that is, environmental protection, energy saving, and industrialization, and is also more conducive to the development of industrialization of residential buildings. The steel structure also has a series of advantages such as strength, light weight, rapid construction, favorable earthquake resistance, flexible building space layout and increased effective use area. At present, many countries such as the United States, Japan, the United Kingdom and Australia are actively promoting the application and development of prefabricated prefabricated steel structure houses (called industrialized steel structure houses in Japan). In the early period of the promotion in 1992, the United States had only 500 buildings, and in 2000 it reached 200,000 buildings, accounting for about 20% of the total number of residential buildings. According to the statistics of Japan in 1999, its steel structure houses accounted for industrial housing. 71%, the rest are wooden and concrete houses. The market share of Australian steel-framed houses is 15%, and there is a significant growth every year. In villa houses built in Europe (such as the United Kingdom, Germany, and the Netherlands), steel structure systems have increasingly been used to replace traditional brick structures. In many developing countries, the industrial production of steel-structured dwellings can provide people with comfortable housing quickly and economically.
Since the reform and opening up, China's residential construction has developed rapidly. In 1999, compared with 1978, the per capita living area of ​​cities in the country has increased from 3.6m2 to 9.78m2. Since the 1990s, under the strong support of national policies, the Ministry of Construction has actively promoted the application and development of steel-structured housing throughout the country. In recent years, a number of demonstration pilot projects for steel-structured houses have been started and completed in Beijing, Shanghai, Xinjiang, Hunan, Ma'anshan in Anhui, and Laiwu Steel City in Shandong. It can be expected that the steel structure residential construction will continue to develop rapidly in the 21st century.
2 The composition and characteristics of the steel structure system of the multi-story building 2.1 The structural system of the steel structure house The steel structure system of the residential building is very different from the traditional brick-concrete structure system or the concrete structure system. It is mainly composed of a load-bearing steel structure system , Floor structure system, supporting structure system and enclosure structure system.
2.1.1 Load-bearing steel structure system The steel frame (beam-column) system is suitable for the load-bearing system of multi-layer steel structure residences. Because the steel structure housing of the load-bearing frame system has a low self-weight and a long natural vibration period, it is insensitive to earthquake response. However, the frame system is a typical flexible structural system, and its lateral rigidity is relatively small. Therefore, for high-rise steel structure houses or multi-storey steel structure houses with large storey heights, various lateral supports need to be provided or combined with elevator shafts and pipelines. The layout of the walls of the wells and stairwells adopts new anti-lateral force systems such as steel frame-shear steel plate shear wall structure, steel frame-shear truss structure, steel frame-concrete core tube (shear wall) structure, etc. The steel frame part mainly bears the vertical load, and the steel frame and the shear wall, the shear truss or the supporting system work together to bear the horizontal load to ensure that the horizontal displacement of the structure is controlled within the allowable value of the code. During the design, the number, stiffness, and form of supports can be adjusted according to the height of the building and the action of horizontal forces, or different anti-lateral force systems can be used.
The structural design of the load-bearing steel structure system should be based on the general design principles of strong columns and weak beams, and strong nodes and weak members, but in specific engineering design, if it is difficult to meet the design formula of strong columns and weak beams, as long as the axial compression ratio is controlled also may. The materials of frame beams and columns are generally high-frequency welding or hot-rolled H-shaped steel; when the column is under a small force, light hot-rolled steel or cold-rolled thin-walled steel can also be used. In order to save steel materials and reduce cost, the frame column can also be a concrete-filled steel tube column, that is, a composite compression member formed by pouring high-strength plain concrete into an empty steel tube. As the concrete-filled steel tube column combines the advantages of the steel column and the concrete column, the axial bearing capacity of the single column is greatly improved, and the cross-sectional size of the steel column is greatly reduced. Compared with H-shaped steel columns, the steel consumption can be saved by about 50%, and the cost is reduced by about 45%. The connection between the tsk frame column and the beam in the direction of the strong axis is suitable for rigid connection; while the connection with the beam in the direction of the weak axis should be combined with support The arrangement adopts hinge + joint processing. The structural form of the steel frame beam-column connection is: (1) full bolt connection: (2) fully welded connection; (3) bolt and weld hybrid connection.
The connection rigidity of the fully welded node is large, followed by the mixed node, and the connection rigidity of the bolt node is small, but the installation and construction speed of the bolt node connection is the fastest, and it is easy to ensure the construction quality when splicing and installing on site. The main beam and the secondary beam are generally hinged, and the structure is mainly welded and high-strength bolt connection, or a mixed connection of bolt and welding can be used: the flange of the beam is welded, and the web is connected by high-strength bolts. The bolts are installed and positioned first, and then the flange is welded, which is more convenient for construction.
2.1.2 Floor structure system The floor structure is composed of steel beams and floor panels. In addition to distributing the vertical load directly to the walls and columns, the main function is to ensure the spatial synergy with the anti-side force structure. Therefore, it must be ensured that the floor has sufficient strength, rigidity and overall stability. As a civil residential structure, the floor must also have good sound insulation, waterproof and fire performance. The primary and secondary beams on the floor should adopt compact construction measures and be closely connected with the floor slab to ensure the overall stability of the steel beam. In order to reduce the weight of the floor slab and increase the construction speed, the currently adopted floor slabs are as follows: (1) Profiled steel plate-cast-in-place concrete composite floor slab. The profiled steel plate is fixed to the steel beam by bolts, which can be used as a permanent formwork and participate in joint work (acting as a tensile reinforcement), eliminating the inconvenience of supporting the formwork. If the cast-in-place concrete slab adopts lightweight aggregate concrete, the self-weight of the combined floor slab can be greatly reduced. (2) Precast prestressed concrete laminated floor slab. That is, prefabricated prestressed concrete thin slabs are connected with steel beams, and concrete thin slabs are poured to form laminated floor slabs. This floor slab not only has the integrity of the cast-in-place composite floor, but also eliminates the need for pressed steel plates, and also requires no formwork, which is convenient for construction and can reduce the cost of floor slabs.
2.1.3 Supporting structure system In order to make the multi-layer steel frame can effectively resist the horizontal earthquake action, improve the lateral rigidity, and reduce the interlayer displacement, a vertical support system composed of angle steel or channel steel can be arranged in the lightweight wall body, and According to the design of the tie rod, the support can be mainly arranged between the window sill and the top of the lower window, which is concealed and can meet the needs of the supporting system. The supporting strokes are arranged in a closed circle around the same plane of the building to form a closed reinforcing hoop, which can effectively improve the lateral rigidity of the steel frame. The form of the supporting system can adopt herringbone, W, X and K shapes. The eccentric support has better ductility and energy dissipation performance under earthquake action, and can be used in strong earthquake areas.
2.1.4 Enclosure structure system In order to reduce the weight of the structure, meet the energy-saving requirements of the building, and give full play to the advantages of the steel structure residence, its enclosure wall should be made of lightweight materials, such as SRC composite insulation wall panels, autoclaved ALC concrete panels (ALC panels) and other factory-prepared standardized lightweight wall panels, glass fiber reinforced cement wall panels and glass curtain walls, etc .; the inner wall can be made of light steel keel gypsum board, aerated concrete lightweight wall panels, lightweight Gypsum block and ALC light block etc.
The roofing system adopts a sassafras system as far as possible. The roofing material can be the same as the floor, or it can be a color profiled steel plate waterproof roof. The roofing system not only has a good waterproof effect, but also plays a role in the thermal insulation of the roof, enriching the building. The external shape of the object.
2.2 The characteristics and comprehensive benefits of the steel structure system Compared with the traditional residential building structure system, the steel structure has a very obvious technical and economic comprehensive advantages. Now, combined with its characteristics, the analysis is summarized as follows: (1) The structure has light weight, good seismic performance, and engineering Low cost. The steel structure house can give full play to the high strength of steel, light weight (about 1/3 ~ 1/2 of the weight of ordinary reinforced concrete structure), good ductility, strong plastic deformation ability, and good seismic performance, not only the earthquake The effect is small, thereby reducing the cross-sectional size of beams and columns, saving the amount of steel, and also reducing the cost of transportation and installation and the cost of foundation foundation. The economic benefit is very considerable.
(2) The external appearance is beautiful, the space layout is flexible, and the building function is enhanced. Due to the light and strong characteristics of steel, it is easy to form a large column spacing and a large space between buildings, flexibly divide and arrange the indoor partition, occupy less structural area and space, and improve the area utilization rate (combined with brick-concrete structure or concrete Compared with the structure, its effective use area can be increased by 1 ° / 15%), which can better meet the functional requirements of modern residential buildings; the supplement of Engineering Mechanics in 2002 can be colorful, concise and clear, and it is very popular among the owners .
(3) It is suitable for standardization, serialization and industrial production, and has a high degree of commercialization. The structural parts used for steel-structured houses can be manufactured in the factory and installed on site. It is suitable for the standardization, serialization and industrial production of the factory. It has a high degree of commercialization, which is conducive to reducing costs, improving product quality, and realizing the integration and industry of China's residential building technology. Change.
(4) The installation of components is convenient, and the construction period is shortened. The steel structure house has a high degree of assembly, the structural parts used are light and handy, and the transportation and installation are convenient and fast; the use of the steel structure can also provide a larger space and more working surfaces for the construction site, and the site has less wet operation, no mold support, and is affected by the climate small. Therefore, its construction cycle can be shortened by at least 1/3 compared with traditional residential buildings, which can speed up capital turnover and greatly improve investment efficiency.
(5) Meet the requirements of environmental protection and reusability. The materials used in steel structure residential buildings are mainly environmentally friendly green recyclable or easily degradable materials. When the building needs to be demolished, most of its materials can be recycled or degraded, which greatly reduces gray construction waste and has little pollution to the surrounding environment. Benefit the country and the people.
In summary, the steel structure system of residential buildings not only has the advantages of high strength, light weight, favorable earthquake resistance, saving steel consumption, transportation and installation costs, lower foundation cost and earthquake resistance, but also has convenient component installation and short construction cycle Accelerate capital turnover, improve investment efficiency, flexible and reasonable building layout, increase effective use area, improve the function of building use and ensure the comprehensive technical and economic advantages of building products. In addition, the exterior of the steel structure house is beautiful in appearance, wide in applicability, beautifying the living environment and steel pollution is small, recyclable and renewable, saving energy, conforming to the characteristics of environmental protection and adapting to industrialized production. It is also extremely competitive economic and social benefits. The design and construction practice of the steel structure residential pilot project that has been built in the domestic industry has shown that the cost of steel structure houses can be lower than that of traditional reinforced concrete structure houses.
An example is the comprehensive comparison of the residential buildings of the Jinfeng Urban Credit Cooperative in Korla, Xinjiang (Table 1).
Table 1 Comparison of the comprehensive schemes of three structural systems of steel and concrete Frame beam floor slab 110mm thick now selected board 110mm thick now around board 110mm thick now zen board filled wall exterior wall: 250nunff aerated concrete block inner wall: 150mm thick aerated concrete block outer wall: 250mm thick aerated concrete block inside Wall: 150mm thick gas block outer wall: 250mm thick block inner wall: 150nun thick block ± 0.00 or more Structural weight (standard value of constant load) unit area weight :. Unit weight of 62t * m'2 :. Weight per unit area of ​​65t * m2: 0.95t * m2 soil over 0.00 Concrete folding thickness (kg * ra'2) steel consumption (lcg * m2) steel consumption (including basic reinforcement) (kg * m'2) comprehensive steel (kg * m2) Comprehensive cost (Yuan * m2) 3 Brief introduction of several domestic pilot projects (1) Shanghai Luhai City is composed of six 25-story high-rise steel structure residences with a construction area of ​​70,000 m2, using a steel frame and a concrete core tube (shearing force) Wall) structural system, profiled steel plate combined floor. The frame columns are made of round steel tube concrete columns, and the frame beams are all made of high frequency welded light H-shaped steel. The outer wall and the household wall are 200mm thick Yitong block, and the inner partition wall is 150mm thick Yitong pet block. The fire resistance grade of the component is first grade, and the design adopts thick fireproof coating.
(2) Shanghai Modern Real Estate Industry Co., Ltd. has built a pilot project of tens of thousands of square meters of multi-layer and thin-layer light steel structure houses. The multi-layer house adopts a frame system composed of cold-formed rectangular steel pipe columns and cap-shaped cold-formed steel: high-rise residence The frame system is composed of a rectangular steel tube concrete column and a cap-shaped cold-formed steel composite beam. The steel is fire-resistant, corrosion-resistant and high-strength phosphorus copper rare earth steel. The floor slab is densely dovetail reinforced concrete composite slab.
6-layer H-shaped steel frame-shear wall structure system, profiled steel plate combined floor, self-supporting masonry external wall, reinforced concrete independent foundation plus connecting beams, fireproofing of components adopts fire retardant coating and mortar cladding. The effective construction period is 120 days, of which the steel frame part is 10 days, and the project cost is 1,000 yuan / m2. Maanshan Iron and Steel Company has built a two-story light steel structure pilot project, all of which use hot-rolled H-shaped steel produced by Maanshan Iron and Steel. In addition, two 16-storey steel frame-supporting structural system residential buildings will also be built in Guangming New Village of Ma Steel.
(5) Shandong Laiwu Iron and Steel Group Co., Ltd. is building an H-shaped steel steel structure residential demonstration community (Sakura Garden Community) in Laiwu Steel City.
Among them, a small apartment (12 floors above ground) residential building adopts steel frame-in-situ concrete shear wall structure, and the enclosure material uses cement lightweight thermal insulation and waterproof wall panels, with a construction area of ​​12,000 m2; The building area is about 1,200m2, using a 6-layer steel frame-supporting structure, and the surrounding materials are aerated concrete blocks and ALC panels.
(6) Hunan Changsha Yuanda Group built a 7-story light steel frame residential model building with a column grid size of 3.6mX6.0m, 120mm thick profiled steel plate-concrete combined floor, steel consumption of 46kg / m2, project cost About 650 yuan / m2 (excluding decoration cost and land price).
(7) In 2000, an 8-storey steel frame-supporting system residential building (Jinfeng City Credit Cooperative Residence Building) was built in Korla, Xinjiang, with a construction area of ​​5,850m2. The frame columns are 4> 300X6 steel tube concrete columns. The copper beams are high-frequency welded light H-shaped steel, the floor slabs are 110mm thick cast-in-place reinforced concrete slabs, the frame filling walls are all made of locally produced fly ash aerated concrete blocks, and the fire protection design of the steel members is 50mm thick aerated concrete masonry Block coating, which is economic and safe, the construction period of the entire project is 5 months.
4 Conclusion The steel structure house is an environmentally friendly green building system. Its rapid development at home and abroad is a new trend in the development of modern buildings and is also in line with the development trend of residential industrialization. The steel structure system of residential buildings has obvious technical and economic comprehensive advantages such as high strength, light weight, saving materials, beautiful appearance, flexible layout, wide applicability, rapid construction, favorable earthquake resistance, energy saving, environmental protection and industrial production. It can be expected that with the development of high-efficiency building steels and the application of building steel structure application technology, the 21st century will be a century in which steel structure residential buildings continue to develop rapidly.
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