Since the 1990s, China's steel structures, especially light steel structures, have developed rapidly. Many of them were designed and built by China, but there are also complete sets of buildings imported from abroad in Guangzhou, Shenzhen, and Zhanjiang. This type of building system has high construction speed, high degree of industrialization, low cost, easy disassembly, light weight of roof and floor structure, small loss in case of disaster, and easy repair. It is widely used in foreign countries and involves almost all industries and industries. The field of civil construction is prosperous.
Since 1996, China ’s steel output has exceeded 100 million tons and now ranks first in the world. This has provided a good material basis for the development and application of light steel structures in China, especially after the WTO entry into China. This momentum will grow even faster.
2 Light steel structure and its scope of application Light steel structure generally refers to the use of colored steel sheet as the roof and wall enclosure, thin-walled steel, type or type 2 as purlins and surrounding beams, and factory-welded type 1 sections or cold The curved thin-walled steel section is used as the beam and column, and the door-type steel frame bolted or welded on the site is used as the main structure of the building. With the continuous development over the years, there have been a series of supporting components, such as waterproof plugs, waterproof tapes, thermal insulation cotton, and various gutter door and window nodes, and so on. Therefore, a relatively complete building system, that is, a light steel building system, has been formed. . Of course, the above-mentioned portal steel frame can be single-layer or multi-layer, and can be single-span or multi-span, so it is widely used in industrial plants. It is also widely used in low-rise civil buildings abroad.
2.1 Advantages of light steel construction The short construction period The biggest advantage of light steel construction is that the components can be manufactured in the factory and spliced and installed on site. The construction time of a relatively small industrial plant only takes 4560 days, and it takes 812 months if a reinforced concrete structure is used about.
Good comprehensive economic benefits. Due to the short construction period, it can be put into use in advance to obtain investment benefits in advance. In addition, due to the use of colored profiled steel plates, the color is bright and beautiful, which improves the dynamic sense of the surrounding environment. It is not necessary to make a pile foundation, which can save investment. Due to the use of polystyrene foam sandwich panels or veneers plus insulation cotton, the thermal insulation and sound insulation are good. In addition, the color steel plate is galvanized as the substrate and silicone is used as the surface. , Made by two-coating and two-baking, the durability is also very good.
Low cost According to the current market price in China, the cost of light steel structure buildings is already lower than that of reinforced concrete structures. When the seismic performance of the plant is good, the steel structure itself is a flexible structure, and its weight is light, which can effectively reduce the seismic response and facilitate earthquake resistance. .
Should be demolished and relocated. Once the owner is not satisfied with the selected plant site or unexpected changes occur in the external environment, it can be demolished within a short period of time with minimal loss, which is not available in reinforced concrete structures.
It is precisely because of the many advantages of light steel structures, and with the continuous emergence of new products that prevent fire and corrosion in recent years, the shortcomings of poor corrosion resistance of light steel structures have been better solved, making it more and more widely used in industrial plants. application.
3 suggested that national standards for light steel structures should be formulated as soon as possible. In the early 1980s, a series of national standards compiled by China also included such as steel structure design codes, 817 cold-formed thin-walled steel structure design codes 088, and so on. There is no doubt that the above-mentioned national standards and regulations have a huge impact on guiding China's construction cause and it is difficult to cover new content. We can no longer fully apply the design specifications of steel structures to design light steel structures. In recent years, foreign light steel manufacturers have entered domestic malls, and domestic manufacturers have also risen rapidly, pushing the construction of China's light steel structure building system to a new climax. However, so far in China, there are few major factors that reduce the amount of steel used, such as the skin effect of the structure, the post-buckling strength of the wide-belt I-shaped section, and the plastic design of the panel after partial buckling. Draw up your own light steel structure calculation design and construction regulations. Foreign light steel manufacturers design in accordance with their own design specifications, and accidents occur frequently in the construction of light steel structures in China; some domestic light steel manufacturers and design institutes still follow the design specifications of ordinary steel structures, resulting in light steel is not light. Irrational phenomenon. Or, if there is no sufficient theoretical basis to rely on experience to pursue low steel consumption and cause engineering accidents, it is not uncommon. Sure enough, Shanghai has taken the lead in compiling the Shanghai Standard Light Steel Structure Design Code, 8086897, and the China Metal Structure Association has compiled the technical code 080298 for the steel structure of portal rigid frame light houses. All these are the corrections for the preparation of light steel buildings. Fan Liangben College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou 310014, China When the amount is the same, the building will be deflected or twisted, and the superstructure will have secondary stress. When the strength of the structural members is insufficient, cracks or even damages occur. Obvious inclination will seriously affect the function of the building, making it difficult for doors and windows to open and close objects to slide down the pipeline and damaged equipment and instruments. People feel panic when tilt, especially high-rise buildings and high-rise structures, are more noticeable. In addition, due to the additional moment generated by the structure, the eccentricity of the upper load is enlarged, resulting in foundation stress damage.
The reason for the building to have a superstructure is the cause of the foundation, the environment of the foundation, the influence of external interference, etc., or a combination of these factors. The development process of slopes is also different. Some are inclined during construction, some are accumulated after a long period of development and exposed to serious effects after many years of use, and others are suddenly produced under external influences; there are gradually It tends to be stable, and there is also constant speed and even sudden increase. When the slant rate develops quickly, or other corresponding regulations of a constant rate continuous structure, a good beginning is created. It is expected that other design and construction quality supervision regulations covering light steel structures will also be promulgated as soon as possible.
4 Improve the technical level of the steel structure business of technical staff. In a relatively long period of time in China, due to the small application of steel structures, it is inevitable that steel structures are relatively unfamiliar. Now it is time to give full play to the academic institutions such as colleges and universities Role, systematically hold lectures on steel structure and light steel structure technology and relevant standard training courses, etc. I believe that they will be welcomed by all grassroots units. After a period of study, they will receive good results and keep up with the times. Improve your business.
5 attaches importance to the investigation and analysis of light steel structural engineering accidents, any new material and new structure, some quality or disaster accidents occurred during its use, it is not unreasonable. It is important to pay serious attention to the exhibition.
Whether or not to implement building correction should be comprehensively considered from the development trend of the magnitude of the sloping hazard. The deformation of the foundation has stabilized, and the tilt has little effect on the function of the building. Therefore, the township will not perform correction, because the social impact of the cost of correction and the unavoidable additional settlement during the correction process may make the correction worthless. However, when the following situations occur in the building, correction should be considered. The tilt has exceeded the standard value of dangerous houses issued by the country or locality, and has caused structural damage to the building or significantly affected the function of the building. ② The tilt has obviously affected people. The program collects relevant information. Including building design and construction documents, engineering geological data, surrounding environmental data, and building subsidence and crack observation data.
Analyze the development trend of the causes and hazards of the building tilt, and determine the necessity and feasibility of correcting the building.
Determine the appropriate correction method. The correction method requires that the safe and reliable technology is feasible and does not affect the total cost of the environment. The total cost of the selected method should be fully estimated. The real reason should be found in the situation of the foundation and foundation of the building's structural form and function, and the experience should be summarized and lessons learned.
Light steel structure is particularly sensitive to wind and snow loads due to its low rigidity due to its thin material. On September 9, 1996, Zhanjiang City, Guangdong Province was hit by a strong typhoon No. 15 or higher, causing severe damage to the city's light steel structure. The disaster situation was then adjusted, analyzed, and carefully summarized. Types of structures such as simple light steel structures ② Light steel structures imported from abroad ③ Domestic self-designed and constructed categories are statistically analyzed, and the results show that among them, there are more damages in types ② and less losses in ③. This shows that due to differences in domestic and foreign conditions, the introduction of complete sets of buildings must be carried out with caution, and accounting should be based on China's conditions to be more appropriate.