Principles Of Material Selection For Steel Structures

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

The four steel types proposed in “Code for Design of Steel Structures” GB50017-2003 are the “appropriate” types and are the first choice when conditions permit. The use of other types is not prohibited, as long as the steel used meets the requirements of the specification.

Fourth, the main technical content of steel structure:

(a) High-rise steel structure technology. According to the building height and design requirements, the frame, frame support, cylinder and giant frame structure are respectively used, and the components can be steel, stiff reinforced concrete or steel tube concrete. The steel members are light and ductile, and can be welded or rolled, which is suitable for super high-rise buildings; stiff reinforced concrete members have high rigidity and good fire resistance, and are suitable for medium and high-rise buildings or bottom structures; steel pipe concrete is easy to construct, For column structures only.

(b) Space steel structure technology. The space steel structure has the advantages of being lightweight, high rigidity, beautiful appearance and fast construction speed. The ball joint flat grid, multi-layer variable-section grid and reticulated shell with a steel pipe as the rod are the structural types with the largest amount of space steel structure in my country. It has the advantages of large space rigidity and low steel consumption and can provide complete CAD in the design, construction and inspection procedures. In addition to the grid structure, there are also large-span suspension cable structures and cable-membrane structures in space structures.

(c) Light steel structure technology. A new structural form consisting of walls and roof envelopes is made with light-colored steel plates. 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 above 5mm, round steel made of flexible support systems and high-strength bolt connections. 30m or more, the height can reach more than ten meters, and light cranes can be set up. The amount of steel used is 20-30kg/m2. Now there are standardized design procedures and specialized production enterprises, with good product quality, fast installation speed, lightweight, low investment, and construction is not limited by seasons, suitable for all kinds of light industrial plants.

(d) Steel-concrete composite structure technology. The beam and column load-bearing structure composed of section steel or steel management and concrete components is a steel-concrete composite structure, and its application range has been expanding in recent years. The composite 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 better fire resistance and corrosion resistance. Combined structural members can generally reduce the amount of steel by 15 to 20%. The composite floor and concrete-filled steel tubular components also have the advantages of less or no formwork, convenient and fast construction, and great promotion potential. It is suitable for frame beams, columns and floors of multi-story or high-rise buildings with large loads, industrial building columns and floors, etc.

(e) High-strength bolt connection and welding technology. High-strength bolts transmit stress through friction and are composed of three parts: bolts, nuts and washers. The high-strength bolt connection has the advantages of simple construction, flexible dismantling, high bearing capacity, good fatigue resistance and self-locking, and high safety. It has replaced riveting and partial welding in the project and has become the main connection method in the production and installation of steel structures. For steel components and thick plates made in the workshop, automatic multi-wire arc submerged welding should be used, and the box-column clapboard should use melting nozzle electro slag welding and other technologies. In the field installation and construction, semi-automatic welding technology, gas-shielded flux-cored welding wire and self-shielded flux-cored welding wire technology should be used.

(f) Steel structure protection technology. The protection of steel structures includes fire prevention, anti-corrosion and rust prevention. Generally, it is not necessary to do anti-rust treatment after the fire-retardant coating treatment, but it still needs to be anti-corrosion treatment in buildings with corrosive gas. There are many types of domestic fire retardant coatings, such as TN series, MC-10, etc. Among them, MC-10 fire retardant coatings include alkyd enamel paint, chlorinated rubber paint, fluororubber paint and chlorosulfonated paint. In the construction, the appropriate coating and coating thickness should be selected according to the steel structure type, fire resistance grade requirements and environmental requirements.