8 basic knowledge of steel structure-Part One

Characteristics of steel structure

1. Lighter weight.
2. Higher reliability.
3. Good vibration (shock) and impact resistance.
4. Relatively highdegree of industrialization of steel structure manufacturing.
5. The steel structure can be assembled accurately and quickly.
6. Easy to be made as a sealed structure.
7. Easy to be corrode
8. Poor fire resistance

Steel grades and properties of commonly used steel structures

1. Carbon structural steel：Q195、Q215、Q235, etc.
2. Low-alloy high-strength structural steel.
3. High-quality carbon structural steel and alloy structural steel
4. Steel for special purpose.

The principle of material selection for steel structure

The principle of material selection for steel structures is to ensure the bearing capacity of the load-bearing structure and prevent brittle failure under certain conditions. It is considered comprehensively according to the importance of the structure, load characteristics, structural form, stress state, connection method, steel thickness and working environment, etc.

The four steel models proposed in the "Code for Design of Steel Structures" GB50017-2003 are the models that are "suitable" for use. They are the first choice when conditions permit. The use of other models is not prohibited, as long as the steel used meets the requirements of the specification.

Main steel structure technical content

High-rise steel structure technology

According to the building height and design requirements, the frame, frame support, tube and giant frame structure are respectively adopted, and its components can be steel, rigid reinforced concrete or steel tube concrete. Steel components are light and have good ductility, and can be welded or rolled, suitable for ultra-high-rise buildings. Rigid reinforced concrete components have high rigidity and good fire resistance, suitable for middle and high-rise buildings or bottom structures. Steel tube concrete construction is simple, only used for column structure.

Space steel structure technology

The space steel structure has light weight, high rigidity, beautiful appearance and fast construction speed. Spherical joint flat grids, multi-layer variable cross-section grids and reticulated shells with steel pipes as members are the structural types with the largest amount of space steel structures. It has the advantages of large space rigidity and low steel consumption. It can provide complete CAD in design, construction and inspection procedures. In addition to the grid structure, the space structure also includes a large-span suspension cable structure, a cable-membrane structure, and so on.

Light steel structure technology

A new structural form composed of light-weight colored steel plates and roof enclosure structures. A light steel structure system composed of large section thin-walled H-shaped steel wall beams and roof purlins welded or rolled by steel plates of more than 5mm, round steel made of flexible support system and high-strength bolt connection, the column distance can be from 6m to 9m, and the span can be up to 30m or more, the height can reach more than ten meters, and can be equipped with light cranes. The steel consumption is 20-30kg/m2. Now there are standardized design procedures and specialized production enterprises, with good product quality, fast installation speed, light weight, low investment, construction is not restricted by seasons, and it is suitable for all kinds of light industrial plants.

Steel-concrete composite structure technology

The load-bearing structure of beams and columns composed of section steel or steel management and concrete components is a steel-concrete composite structure, and its application scope has been expanding in recent years. The combined structure has the advantages of both steel and concrete, with high overall strength, good rigidity, and good seismic performance. When the outer concrete structure is used, it has good fire resistance and corrosion resistance. Combined structural members can generally reduce the amount of steel used by 15-20%. The combined floor and concrete-filled steel tube components also have the advantages of convenient and fast construction, and great potential for promotion. It is suitable for frame beams, columns and floors of multi-storey or high-rise buildings with larger loads, as well as industrial building columns and floors, etc.

High-strength bolt connection and welding technology

High-strength bolts transmit stress through friction and are composed of bolts, nuts and washers. High-strength bolt connection has the advantages of simple construction, flexible removal, high bearing capacity, good fatigue resistance, good self-locking performance, and high safety. The project has replaced riveting and partial welding, and has become the main connection method in the production and installation of steel structures. For steel components made in the workshop, automatic multi-wire arc submerged welding shall be used for thick plates. During on-site installation and construction, semi-automatic welding technology, gas shielded flux cored wire and self-shielded flux cored wire technology should be used.

Steel structure protection technology

Steel structure protection includes fire protection, anti-corrosion, and anti-rust. Generally, anti-rust treatment is not required after the treatment of fire-resistant paint, but anti-corrosion treatment is still required in buildings with corrosive gas. There are many types of domestic fireproof coatings, such as TN series, MC-10, etc. Among them, MC-10 fireproof coatings include alkyd enamel, chlorinated rubber paint, fluororubber paint and chlorosulfonated paint. During construction, appropriate paint and coating thickness should be selected according to the steel structure type, fire resistance grade requirements and environmental requirements.

Goals and measures of steel structure

Steel structure projects involve a wide range of areas and are technically difficult. National and industry standards must be followed in the promotion and application. Local construction administrative departments should pay attention to the construction of the specialization stage of steel structure engineering, organize the training of quality inspection teams, and summarize work practices and new technology applications in a timely manner. Mass academic groups should cooperate with the development of steel structure technology, extensively carry out domestic and foreign academic exchanges and training activities, and actively improve the overall level of steel structure design, production, construction and installation technology, and rewards can be improved in the near future.

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