Basic Knowledge Of Steel Structure
Jun 21, 2022
Characteristics of steel structure
Steel structure has light dead weight
The working reliability of steel structure is high
The steel has good vibration (shock) resistance and impact resistance
Steel structure manufacturing has a high degree of industrialization
Steel structures can be assembled accurately and quickly
Easy to make sealed structure
Steel structures are susceptible to corrosion
Poor fire resistance of steel structure
Grades and properties of steels commonly used in structural steel
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.Special purpose steel
Principle of material selection for steel structure
The material selection principle of steel structure is to ensure the bearing capacity of load-bearing structure and prevent brittle failure under certain conditions, according to the importance of structure, load characteristics, structural form, stress state, connection method, steel thickness and working environment and other factors to evaluate.
"Code for Design of Steel Structures" GB50017-2003 proposed four steel models are "appropriate" to use models, is the first choice when conditions permit, does not prohibit the use of other models, as long as the steel used meet the requirements of the code.
Main technical content of steel structure
According to the height and design requirements of the building, frame, frame support, cylinder and giant frame structure, its components can be made of steel, reinforced concrete or concrete filled steel tube. The steel component have good ductility and light weight, and can be welded or rolled, which is suitable for super high construction layer buildings. Strong reinforced concrete steel component stiffness, good fire performance, suitable for high-rise buildings or bottom structure; Concrete filled steel tube is easy to construct and only used for column structure.
Space steel structure has light weight, large stiffness, beautiful shape and fast construction speed. Plate truss with ball joint, multilayer variable section truss and reticulated shell with steel tube as rod are the most used spatial steel structures in China. It has the advantages of large space stiffness, low steel quantity, in design, construction and inspection procedures, and can provide complete CAD. In addition to the grid structure, there are large span suspension cable structure, cable membrane structure and so on.
A new structural form consisting of walls and roof enclosures is made with light colored steel plates. Made of 5mm or more steel plate welding or rolling large section thin wall H-beam and roof purlin, round steel made of flexible support system and high strength bolt connection composed of light steel structure system, column distance can be from 6m to 9m, the span can reach 30m or greater, the height can reach more than ten meters, and can set up light suspension four. Use steel 20 ~ 30kg/m2. There are standardized design procedures and professional production enterprises, good product quality, fast installation speed, light weight, less investment, construction is not restricted by the season, suitable for all kinds of light industrial plants.
Steel concrete composite structure technology
The beam and column bearing structures composed of section steel or steel tube and concrete component are steel-concrete composite structures, which are increasingly applied in recent years. Combined structure has the advantages of both steel and concrete, overall strength, good rigidity, good seismic performance, when the use of concrete structure, more good fire resistance and corrosion resistance. Composite structural component can generally reduce the amount of steel used by 15 ~ 20%. Composite floor and concrete-filled steel tube components also have the advantages of less supporting or no supporting mold, convenient and fast construction, and have great potential for popularization. It is suitable for frame beams, columns and floors of multi-storey or high-rise buildings with large loads, columns and floors of industrial buildings, etc.
High strength bolt connection and welding technology
High-strength bolts are made up of bolts, nuts and washers to transfer stress through friction. 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 engineering and become the main connection means in the production and installation of steel structure. For steel components made in the workshop, automatic multi-wire arc welding should be used for thick plates, and nozzle electroslag welding should be used for box column separators. Semi-automatic welding technology, gas shielded flux cored wire and self-shielded flux cored wire should be used in the field installation and construction.
Steel structure protection technology
Steel structure protection includes fire prevention, anti-corrosion, anti-rust, is generally used in fire retardant coating treatment without anti-rust treatment, but in the building of corrosive gas still need to be anti-corrosion treatment. Domestic fireproof coating types are more, such as TN series, Mc-10 etc., among which Mc-10 fireproof coating has alkyd enamel, chlorinated rubber paint, fluorine rubber paint and chlorinated sulfonated paint. Suitable coating and coating thickness should be selected according to the type of steel structure, fire resistance grade and environmental requirements during construction.
Objectives and measures of steel structure
Steel structure engineering involves a wide range of technical difficulties, in the promotion and application must follow the national and industrial standards. Local construction administrative departments should attach importance to the construction of specialized stage of steel structure engineering, organize the training of quality inspection team, and summarize the work practice and new technology application in time. Colleges and universities, design departments and construction enterprises should speed up the training of steel structure engineers and technicians and popularize the steel structure CAD with mature technology. Mass academic organizations should cooperate with the development of steel structure technology, carry out extensive academic exchanges and training activities at home and abroad, and actively improve the overall level of steel structure design, manufacture, construction and installation technology in the near future.
Connecting method of steel structure
Steel structure connection method has weld joint, bolt connection and rivet connection three kinds.
1.Welding connection
Weld joint is through the heat generated by the arc to melt the electrode and welding parts, after cooling condensation weld, so as to connect the welding parts into one.
Advantage
Does not weaken the component section, saving steel, simple structure, convenient manufacturing, large connection stiffness, good sealing performance, easy to use automation under certain conditions, high production efficiency.
Disadvantage
The heat affected zone of the steel near the weld may be caused by the brittle material in some parts. During the welding process, the steel is subjected to the uneven distribution of high temperature and cooling, resulting in welding residual stress and residual deformation of the structure, which has a certain influence on the bearing capacity, stiffness and service performance of the structure. Due to the large stiffness of welded structure, once the local crack occurs, it is easy to spread to the whole, especially at low temperature, brittle fracture is easy to occur. The plasticity and toughness of weld joints are poor, and defects may occur during welding, which reduces the fatigue strength.
2.Bolted connection
Bolted connections are made by means of fasteners such as bolts. Bolt connection is divided into ordinary bolt connection and high strength bolt connection.
Advantage
The construction process is simple, easy to install, especially suitable for site installation and connection, also easy to disassemble, suitable for the need to assemble and disassemble the structure and temporary
Disadvantage
The need to open holes on the plate and assemble the hole, increase the manufacturing workload, and the manufacturing accuracy is higher; The bolt hole also weakens the section of the member, and the connecting piece often needs to lap each other or add auxiliary connecting plate (or Angle steel), so the structure is more complex and much steel.
3.Rivet connection
Rivet joint is to make rivets with semicircular prefabricated nail head at one end, and quickly insert the nail rod into the nail hole of the connector after it is heated red, and then use a riveting gun to rivet the other end into a nail head to make the connection secure.
Advantage
Reliable riveting force transmission, good plasticity, toughness, quality is easy to check and guarantee, can be used for heavy and directly bearing dynamic load structure.
Disadvantage
Riveting has been largely replaced by welding and high-strength bolting because of its complexity, manufacturing costs and high labor intensity.
