Steel structure: a structure mainly made of steel, which is one of the main types of building structures. Steel is characterized by high strength, light weight and high rigidity, so it is especially suitable for building long-span, ultra-high and overweight buildings. The material is an ideal elastomer with good uniformity and isotropy, which is most in line with the basic assumptions of general engineering mechanics. The material has good plasticity and toughness, can deform greatly and can bear dynamic load well; Short construction period; High degree of industrialization, which can be used for specialized production with high degree of mechanization; It has high machining precision, high efficiency and good air tightness, and can be used to manufacture gas tanks, oil tanks, transformers, etc. Its disadvantages are poor fire resistance and corrosion resistance. It is mainly used for the load-bearing skeleton of heavy factory buildings, factory buildings under dynamic loads, plate-shell structures, high-rise TV towers and masts, long-span structures such as bridges and libraries, high-rise and super-high-rise buildings, etc. In the future, high-strength steel should be studied in steel structure to greatly improve its yield point strength; In addition, new steel products such as H-beam (also known as wide flange steel), T-beam and profiled steel plate should be rolled to meet the needs of long-span structures and super high-rise buildings. Steel structures are divided into light steel and heavy steel. Without a unified evaluation standard, many experienced designers or project managers often can't fully explain it. We can comprehensively consider and use some data to judge:

The general specifications for steel structure design are as follows:

Code for Design of Steel Structures (GB500 17-2003)

Technical specification for cold-formed thin-walled steel structures (GB500 18-2002)

Code for Acceptance of Construction Quality of Steel Structure Engineering (GB50205-200 1)

Technical Code for Welding of Building Steel Structures (JGJ8 1-2002, J2 18-2002)

Technical Specification for Steel Structures of High-rise Civil Buildings (JGJ99-98)

The first-class registered structural engineer exam is required.

Connection method of steel structure

Welded joint

bolted connection

Rivet connection [edit this paragraph] 1. Heavy steel structure 1, lifting capacity of workshop crane: ≥ 25t.

2. Steel consumption per square meter: ≥ 50kg /M2. Such as: petrochemical plant facilities, power plant buildings, long-span gymnasiums, exhibition centers, high-rise or super-high-rise steel structures. [Edit this paragraph] 2. Thickness of steel plate, the main component of light steel structure: ≥ 10 mm Light steel is also a vague term, which can be understood in two ways. One is the "light steel structure with round steel and small angle steel" in Chapter 11 of the current Code for Design of Steel Structures (GBJ 17-88), which refers to the light steel structure made of round steel and angle steel smaller than L45×4 and L56×36×4. It is mainly used for small structures that are not suitable for reinforced concrete structures when steel is in short supply, but it has not been widely used yet, so this steel structure design specification is adopted. The other is the single-layer solid-web light-weight external wall of portal frame roof (masonry external wall can also be used if conditions permit) stipulated in Technical Specification for Steel Structure of Portal Frame Light-weight Buildings. The light structure here mainly refers to the use of light materials for enclosure. Since the former has been cancelled soon, the meaning of light steel now mainly refers to the latter. In addition, there are some reference values, such as cost per square meter, maximum component weight, maximum span, structural form, eaves and so on, which can provide empirical data when judging whether the factory building is heavy steel or light steel. Of course, many buildings now have light and heavy steel. There is no word "heavy steel" in national specifications and technical documents. In order to distinguish the steel structure of light houses, it may be more appropriate to call the general steel structure "ordinary steel". Because the scope of ordinary steel structure is very wide, it can include all kinds of steel structures, regardless of load, and even include many contents of light steel structures. The Technical Specification for Steel Structures of Light Buildings only provides some more specific contents for its "light" characteristics, and its scope is limited to single-story portal frames. It can be seen that the difference between light steel and heavy steel lies not in the weight of the structure itself, but in the weight of the envelope material it carries, but in the concept of structural design. Steel structure is one of the common structural forms in modern building engineering. China is the first country to manufacture load-bearing structures with iron. As early as the Qin Shihuang era (246-2 BC19 BC), iron was already used as a simple load-bearing structure, while western countries began to use metal load-bearing structures in the17th century. In the 3rd-6th century, the smart and industrious people of China built a suspension bridge with iron chains. The famous iron cable bridge of Dadu River in Luding, Sichuan, Yuanjiang Bridge in Yunnan and Panjiang Bridge in Guizhou are all models of early iron load-bearing structures in China. Although China made outstanding achievements in iron structure in the early days, it remained at the level of iron construction for a long time because of the shackles of feudal system for more than 2,000 years and underdeveloped science. It was not until the end of 19 that China began to adopt modern steel structures. After the founding of New China, the application of steel structure has made great progress, both in quantity and quality. It has reached a high level in design, manufacture and installation technology, and mastered the design and construction technology of various complex buildings. Many large and complex steel structure workshops, long-span steel structure civil buildings and railway bridges have been built all over the country, such as the steel roof truss of the Great Hall of the People in China, the steel grid of the gymnasium in Beijing and Shanghai, the three-hinged steel arch of the Terracotta Warriors and Horses Exhibition Hall in Shaanxi, and the Bird's Nest in Beijing.

Code for Design of Steel Structures (GBJ 17-88) was abolished on June 65438+February 1 day, 2003. At present, the Code for Design of Steel Structures (GB 500 17-2003) is implemented. Three. Definition of equipment steel structure.

Equipment steel structure refers to the steel structure of large equipment. According to the experience of Julia Engineering (QYTEC) technicians, the following structures should be classified into the category of equipment steel structure: tower steel structure of bridge erecting machine, crane lifting beam, crane body, large equipment support, etc. It belongs to one of the precision steel structures with high requirements on precision, material and connection. For the complete set of equipment, it is the most important stress component, which plays a structural role in function.

manufacture

The fabrication of equipment steel structure is similar to that of precision steel structure, which is between ordinary structural parts (with low machining requirements) and precision machined parts (with fine machining requirements) and connected by welding or bolts.

ask

Equipment steel structure usually puts forward special requirements or higher requirements in the following aspects:

Structural parts: material, surface roughness, tolerance, surface treatment, straightness (or radian)

Connection: hole position deviation and bolt grade; Welding methods, welding standards and welding materials; Air tightness requires nondestructive testing, liquid penetration testing, etc.

Overall structure: verticality, levelness, etc.

Packaging: packaging materials and methods.

Storage: ambient temperature and humidity.

Transportation: loading and unloading, putting into cars, putting into containers, and so on. [Edit this paragraph] Steel structure refers to the structural form that connects steel plates with hot rolled, cold bent or welded profiles through connectors and can bear and transmit loads. The steel structure system has the comprehensive advantages of light weight, factory manufacturing, quick installation, short construction period, good seismic performance, quick investment recovery and less environmental pollution. Compared with reinforced concrete structure, it has the unique advantages of "high, large and light". Steel structure has been reasonably and widely used in the field of construction engineering in all countries of the world, especially in developed countries and regions. Steel structure industry is usually divided into five categories: light steel structure, high-rise steel structure, residential steel structure, space steel structure and bridge steel structure.

Steel structures are widely used in various projects, such as steel bridges, steel mills, steel gates, various large pipeline containers, high-rise buildings, tower and rail mechanisms, etc. [Edit this paragraph] The steel structure is characterized by 1, and its weight is relatively light.

2. The reliability of steel structure is high.

3. Steel has good vibration (impact) and impact resistance.

4. The steel structure manufacturing is highly industrialized.

5. The steel structure can be assembled accurately and quickly.

6. The steel structure has a large indoor space.

7. It is easy to make a sealing structure.

8. Steel structures are easy to corrode.

9. The fire resistance of steel structure is poor.

10, steel structure can be recycled.

1 1, short steel structure construction period [edit this paragraph] Brand and performance of common steel structures 1, carbon structural steel: Q 195, Q2 15, Q235, Q255, Q275, etc.

2, low alloy high strength structural steel

3, high quality carbon structural steel and alloy structural steel

4. Special-purpose steel [edit this paragraph] There is no unified judgment standard for the qualitative difference between light steel and heavy steel, and the structure of heavy steel and light steel. Many experienced designers or project managers often can't fully understand, but we can use some data to comprehensively consider and judge:

1. Lifting capacity of workshop crane: 25 tons and above, which can be regarded as heavy steel structure.

2. Steel consumption per square meter: above 50KG/M2, which can be regarded as heavy steel structure.

3. The thickness of the main component steel plate: 10MM or more, and light steel structure is rarely used.

In addition, there are some reference values, such as cost per square meter, maximum component weight, maximum span, structural form, eaves and so on, which can provide empirical data when judging whether the factory building is heavy steel or light steel. Of course, many buildings now have light and heavy steel. But some of them are heavy steel, such as petrochemical plants and facilities, power plants, long-span stadiums and exhibition centers, high-rise or super-high-rise steel structures, etc.

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In fact, there is no such thing as heavy steel in national specifications and technical documents. In order to distinguish the steel structure of light houses, it may be more appropriate to call the general steel structure "ordinary steel". Because the scope of ordinary steel structure is very wide, it can include all kinds of steel structures, regardless of load, and even include many contents of light steel structures. The Technical Specification for Steel Structures of Light Buildings only provides some more specific contents for its "light" characteristics, and its scope is limited to single-story portal frames.

Light steel is also a vague term, which can generally be understood in two ways. One is the "light steel structure with round steel and small angle steel" in Chapter 11 of the current Code for Design of Steel Structures (GBJ 17-88), which refers to the light steel structure made of round steel and angle steel smaller than L45 * 4 and L56 * 36 * 4. It is mainly used for small structures that are not suitable for reinforced concrete structures when steel is in short supply, but it is not widely used now, so this steel structure design specification is adopted. The other is the single-layer solid-web light-weight external wall of portal frame roof (masonry external wall can also be used if conditions permit) stipulated in Technical Specification for Steel Structure of Portal Frame Light-weight Buildings. The light structure here mainly refers to the use of light materials for enclosure. Since the former has been cancelled soon, the meaning of light steel now mainly refers to the latter.

It can be seen that the difference between light steel and heavy steel lies not in the weight of the structure itself, but in the weight of the envelope material, and the structural design concept is the same.

Steel structure installation

Prefabrication of steel members

According to the installation sequence and process requirements, prefabrication and assembly of steel members are carried out on the steel platform to ensure the welding quality.

The spacing between flange plate splicing joint and web splicing joint of section steel splicing joint should be greater than 200mm. The splicing length of flange plate should not be less than 2 times of plate width; Web splicing width should not be less than 300㎜ and length should not be less than 600㎜.

In order to facilitate welding and ensure welding quality, stiffening ribs, connecting plates, pads and cantilever beams on columns and beams should be assembled and welded on the ground steel platform according to the construction drawing size.

Precast steel members on the steel platform shall be manufactured and assembled according to the requirements of construction drawings and specifications, and the changes of site installation technology and installation size shall also be considered.

The allowable deviation of the overall verticality and overall plane bending of the main structure of steel structure shall comply with the provisions in the table below.

The allowable deviation of column installation shall comply with the provisions in the table below.

Allowable deviation of overall verticality and overall plane bending (mm)

Example of allowable deviation of project

The entirety of the main structure

perpendicular/vertical

Development prospect of steel structure

Steel structure is the future development trend.

In the past, the slow development of steel structure in China was mainly due to the high cost of steel structure (after all, we are a developing country) and limited steel output.

Today is different from the past. The advantages of steel structure, such as fast construction speed, less pollution and light weight, make it the future development trend. Today, many buildings have begun to adopt steel structures. [Edit this paragraph] Advantages of steel structure: The roofs of low-rise villas are mostly sloping roofs, so the roof structure basically adopts a triangular roof truss system made of cold-formed steel members. After the structural plate and gypsum board are sealed, the light steel members form a very strong "plate-rib structure system", which has stronger seismic and horizontal load resistance, and is suitable for areas with seismic intensity above 8 degrees.

Wind resistance: I-shaped steel structure building has light weight, high strength, good overall stiffness and strong deformation ability. The 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 and effectively protect life and property.

Durability: The residential structure of light steel structure adopts cold-formed thin-walled steel member system, and the steel skeleton adopts ultra-anticorrosive high-strength cold-rolled galvanized sheet, which effectively avoids the influence of steel plate corrosion during construction and use, and increases the service life of light steel members. The structural life can reach 100 years.

Thermal insulation: the thermal insulation material used is mainly glass fiber cotton, which has good thermal insulation effect. The insulation board used for the external wall can effectively avoid the "cold bridge" phenomenon of the wall and achieve better insulation effect. The thermal resistance of R 15 thermal insulation cotton with a thickness of about 100mm can be equivalent to that of a brick wall with a thickness of1m.

Sound insulation: Sound insulation effect is an important index to evaluate the house. The windows installed in the light steel system are made of insulating glass, which has good sound insulation effect, and the sound insulation reaches more than 40 decibels. The sound insulation effect of the wall composed of light steel keel and thermal insulation gypsum board can reach 60 decibels.

Health: dry construction reduces the environmental pollution caused by wastes, the steel structure materials of the building can be recycled 100%, and most other supporting materials can be recycled, which conforms to the current environmental awareness; All materials are green building materials, which meet the requirements of ecological environment and are beneficial to health. ?

Comfort: Light steel wall adopts high-efficiency and energy-saving system, which has breathing function and can adjust indoor air humidity; The roof has ventilation function, which can form a flowing air chamber above the house to ensure the ventilation and heat dissipation requirements inside the roof.

Fast: all dry construction, not affected by environmental seasons. A building of about 300 square meters needs only five workers for 30 working days to complete the whole process from foundation to decoration.

Environmental protection: the material can be recycled 100%, which is truly green and pollution-free.

Energy-saving: All walls are made of high-efficiency and energy-saving materials, with good thermal insulation and sound insulation effect, which can reach 50% energy-saving standard. [Edit this paragraph] Causes of steel structure damage and reinforcement technical measures When the steel structure is damaged, the problem should be found and solved immediately. The main factors of steel structure damage are: 1) insufficient bearing capacity of the structure caused by load change, extended service and code change; 2) The component is deformed, twisted, failed and sunken due to various accidents, which leads to the weakening of the component section, the warping of the bar and the cracking of the connection. 3) Deformation, cracking and warping of components or connectors caused by temperature difference; 4) Corrosion caused by chemical corrosion and electrochemical corrosion weakens the section of steel structure members; 5) Others include mistakes in design, production and construction and illegal operation during service.

There are three main technical measures for steel structure reinforcement: 1) section reinforcement method: steel is used to reinforce parts or along the whole length of components, and they are connected into a whole to bear the same force; 2) Change the calculation diagram: add additional supports, adjust the load distribution, reduce the internal force level, forcibly replace the statically indeterminate structural supports, and reduce the peak stress; 3) Prestressed cable method: using high-strength cables to strengthen the weak links of the structure or improve the overall bearing capacity, stiffness and stability of the structure. [Edit this paragraph] Advantages of steel structure Compared with other buildings, steel structure has advantages in use, design, construction and comprehensive economy, with low cost and can be moved at any time.

1. Compared with traditional buildings, steel structure residential buildings can better meet the requirements of flexible partition of large rooms, and can improve the area utilization rate by reducing the cross-sectional area of columns and using lightweight wallboard, and the indoor effective area can be increased by about 6%.

Second, the energy-saving effect is good. The wall is made of light and energy-saving standardized C-section steel, square steel and sandwich panel, which has good thermal insulation and seismic performance. Save energy by 50%,

Thirdly, the application of steel structure system in residential buildings can give full play to good ductility, strong plastic deformation ability and excellent earthquake-resistant and wind-resistant ability, and greatly improve the safety and reliability of residential buildings. Especially in the case of earthquake and typhoon disasters, steel structures can avoid the collapse of buildings.

Fourth, the total weight of the building is light, and the steel structure residential system is light, which is about half of the concrete structure, which can greatly reduce the foundation cost.

5. The construction speed is fast, the construction period is at least one third shorter than that of the traditional residential system, and it only takes 20 days and 5 workers to complete a building with a square meter of 1000.

Sixth, the environmental protection effect is good. In the construction of steel structure residence, the amount of sand, stone and ash is greatly reduced. The materials used are mainly green, and 100% recycled or degraded materials. When the building is demolished, most materials can be reused or degraded without causing garbage.

7. Flexibility and richness. Large bay design, indoor space can be divided into a variety of programs to meet the different needs of users.

Eight, in line with the requirements of residential industrialization and sustainable development. The steel structure is suitable for mass production in factories and has a high degree of industrialization. It can integrate advanced finished 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.

Compared with ordinary reinforced concrete structure, steel structure has the advantages of uniformity, high strength, fast construction speed, good seismic performance and high recovery rate. The strength and elastic modulus of steel are many times higher than that of masonry and concrete, so the weight of steel members is light under the same load. From the aspect of being destroyed, the steel structure shows signs of large deformation in advance, which belongs to ductile failure structure and can find the danger in advance and avoid it.

Steel structure workshop frame steel structure workshop has the advantages of light overall weight, foundation saving, less materials, low cost, short construction period, large span, safety and reliability, beautiful shape and stable structure. Steel structure workshops are widely used in long-span industrial workshops, warehouses, cold storage, high-rise buildings, office buildings, multi-storey parking lots, residential buildings and so on.