What is steel structure? In academic language, steel structure is a structure mainly made of steel, which is one of the main types of building structures now. Steel is characterized by high strength, light weight, good overall rigidity and strong deformation capacity, so it is particularly suitable for building large-span, super high and super heavy buildings. Steel structures are steel beams, steel columns, steel trusses and other components made of section steel and steel plates; The members or components are connected by welds, bolts or rivets.
1、 Main features of steel structure
The steel structure has the advantages of light weight, high strength, good overall rigidity and strong deformation capacity. The self weight of the building is only one fifth of that of the brick concrete structure, which can resist the hurricane of 70 meters per second, so that life and property can be effectively protected.
The roofs of low rise villas are mostly sloped roofs. Therefore, the roof structure basically adopts the triangular roof truss system made of cold-formed steel members. After the structural plates and gypsum boards are sealed, the light steel members form a very solid “plate rib structure system”. This structure system has stronger seismic resistance and resistance to horizontal loads, and is suitable for areas with seismic intensity of more than 8 degrees.
Sound insulation effect is an important index for evaluating residential buildings. Hollow glass is used for windows installed with light steel system, which has good sound insulation effect, and the sound insulation reaches more than 40 db; The sound insulation effect of the wall composed of light steel keel and thermal insulation material gypsum board can be as high as 60 dB.
The thermal insulation material used is mainly glass fiber cotton, which has good thermal insulation effect. The thermal insulation board used for the external wall can effectively avoid the “cold bridge” phenomenon of the wall and achieve a better thermal insulation effect. The thermal resistance value of R15 insulation cotton with a thickness of about 100mm can be equivalent to a brick wall with a thickness of 1m.
Dry operation construction can reduce the environmental pollution caused by waste. The steel structure materials of the house can be 100% recycled, and most of other supporting materials can also be recycled, which is in line with the current awareness of environmental protection; All materials are green building materials, which meet the requirements of ecological environment and are conducive to health.
The residential structure of light steel structure is composed of cold-formed thin-walled steel members, and the steel ribs are made of super anti-corrosion high-strength cold-rolled galvanized sheet, which effectively avoids the impact of corrosion of steel plates during construction and use, and increases the service life of light steel members. The service life of the structure can reach 100 years.
The light steel wall adopts high-efficiency energy-saving system, which has breathing function and can adjust the dry humidity of indoor air; The roof has a ventilation function, which can form a flowing air room over the interior of the roof to ensure the ventilation and heat dissipation requirements inside the roof.
2、 Advantages and disadvantages of steel structure
- Compared with traditional buildings, steel structure residences can better meet the requirements of flexible separation of large bays in buildings, and can improve the area utilization rate by reducing the cross-sectional area of columns and using lightweight wallboards. The indoor effective use area can be increased by about 6%.
The energy-saving effect is good. The wall adopts light energy-saving standardized C-shaped steel, square steel and sandwich board, which has good thermal insulation performance and seismic resistance. 50% energy saving,
- The application of steel structure system in residential buildings can give full play to the good ductility, strong plastic deformation capacity, excellent seismic and wind resistance performance of steel structures, and greatly improve the safety and reliability of residential buildings. Especially in the case of earthquake and typhoon disasters, the steel structure can avoid the collapse damage of buildings.
- The total weight of the building is light, and the self weight of the steel structure residential system is light, about half of the concrete structure, which can greatly reduce the foundation cost.
- The construction speed is fast. The construction period is at least one third shorter than that of the traditional residential system. It takes only 20 days and five workers to complete a 1000 square meter building.
- Good environmental protection effect. During the construction of steel structure residential buildings, the amount of sand, stone and ash is greatly reduced. The materials used are mainly green, 100% recycled or degraded materials. When the buildings are demolished, most of the materials can be reused or degraded without causing garbage.
- With flexibility and abundance. Large bay design, indoor space can be divided by multiple schemes, which can meet the different needs of users.
- It meets the requirements of housing industrialization and sustainable development. The steel structure is suitable for mass production in the factory, with a high degree of industrialization. It can integrate advanced products such as energy saving, waterproof, heat insulation, doors and windows, and apply them in complete sets, integrating design, production and construction, and improving the level of the construction industry.
The complexity of construction quality problems of steel structure engineering projects is mainly manifested in that there are many factors that cause quality problems, and the causes of quality problems are also complex. Even for quality problems of the same nature, sometimes the causes are different, so the analysis, judgment and treatment of quality problems increase the complexity. For example, welding cracks can occur not only in the weld metal, but also in the base metal heat effect, either on the weld surface or inside the weld; The crack strike can be either parallel to or perpendicular to the weld bead. The crack may be either cold or hot; The causes also include improper selection of welding materials and improper preheating or post heating of welding.
The construction quality problems of steel structure engineering will continue to develop and change with the external changes and the extension of time, and the quality defects will gradually manifest. For example, due to the change of stress in the weld of steel members, the original weld without cracks will produce cracks: delayed cracks can be produced due to the action of hydrogen activity in the weld after welding. In addition, if the member is overloaded for a long time, the steel member will have bending deformation under the arch, resulting in hidden dangers.
The severity of construction quality problems of steel structure engineering projects is as follows: generally, it will affect the smooth progress of construction, cause delay of construction period, increase of cost, and seriously, buildings will collapse, cause casualties, property damage, and cause adverse social impact.
Because modern buildings in China are mainly concrete structures, the management and technical personnel engaged in building construction are relatively unfamiliar with the manufacturing and construction technology of steel structures, and the specific construction personnel mainly migrant workers do not understand the scientific construction methods of steel structure engineering, resulting in frequent accidents in the construction process.
The steel structure industry can better adapt to and meet the needs of economic construction because of its economic and technological advantages, low-carbon emission reduction, circular economy, industrialization and industrialization. It will also become one of the new industries with broad market, numerous enterprises, continuous innovation and full of vitality.