Important knowledge points of steel structure

1. The steel structure system has comprehensive advantages such as light weight, easy installation, short construction period, good seismic performance, fast investment recovery, and less environmental pollution. It has good plasticity and toughness, as well as good impact resistance. 

2. The types of steel are divided into thin plates (thin steel plate thickness<4mm), medium plates (medium thickness 4-20mm), and thick plates (thickness 20-60mm) according to their thickness. A thickness greater than 60 is considered a special thickness type. Steel strip is included in the category of steel plates. 

3.What is the difference between ordinary bolts and high-strength bolts? Ordinary bolts are generally made of ordinary carbon structural steel without heat treatment, while high-strength bolts are generally made of high-quality carbon structural steel or alloy structural steel and require quenching and tempering heat treatment to improve their comprehensive mechanical properties. High strength is divided into 8.8, 10.9, and 12.9 levels. From the strength level: High strength bolts commonly use two strength levels, 8.8S and 10.9S. Ordinary bolts generally have grades 4.4, 4.8, 5.6, and 8.8. High strength bolts apply pre tension and transmit external force through friction, while ordinary bolts transmit shear force through bolt resistance and hole wall pressure. 

4. Classified by force characteristics: friction type and pressure type. Friction type high-strength bolts transmit external forces based on the frictional force between the connected parts. When the shear force is equal to the frictional force, it is the design ultimate load of the friction type high-strength bolt connection. At this time, the members of Lianzhong will not experience relative slippage, the bolt rod will not be sheared, and the bolt hole wall will not be under pressure. The bearing type high-strength bolt is similar to the ordinary bolt. The shear force can exceed the friction force. At this time, there will be relative slip between the connected components. The bolt rod contacts the hole wall. The connection relies on the friction force and the shear and bearing force of the bolt rod to transmit the force together. Pressure bearing high-strength bolts have significant deformation and are not suitable for connecting structures that directly bear dynamic loads.

5. There are several types of welding rods: generally more than ten types: carbon steel welding rods, low-alloy steel welding rods, molybdenum and chromium molybdenum heat-resistant steel welding rods, low-temperature steel welding rods, stainless steel welding rods, overlay welding rods, cast iron welding rods, nickel and nickel alloy welding rods, copper and copper alloy welding rods, aluminum and aluminum alloy welding rods, and special purpose welding rods.