High strength bolt connection

　　High-strength bolts are made of high-strength steel, or the bolts that need to impose a large preload, can be called high-strength bolts, high-strength bolts are mostly used for Bridges, rails, high-pressure and ultra-high-pressure equipment connection, the fracture of such bolts is mostly brittle fracture.

　　Steel structure high strength bolt connection is rapidly developed in nearly 40 years of use and form bolt connection, due to its good mechanical performance, fatigue performance is good, good aseismatic new can, connection stiffness big, construction is convenient wait for a characteristic, is widely used in steel structure engineering, in a lot of the structure of the high-rise steel structure, steel beams and the connection between the main secondary beam with high strength bolt connection, usually High strength bolts are used to withstand the shear force of the mesh.

　　1, welding

　　Advantages: Strong adaptability to geometric forms; Simple structure; Do not weaken the section, can realize automatic operation; The sealing of the connection is good and the structure stiffness is large

　　Disadvantages: high requirements for material; Heat affected zone, easy to lead to local material change; The residual stress and deformation of welding reduce the bearing capacity of the compression member. Welded structure is sensitive to crack; Low temperature cold brittle problem is more prominent

　　2, riveting

　　Advantages: reliable force transmission, good toughness and plasticity, easy to check quality, good resistance to dynamic load

　　Disadvantages: complex structure, cost steel cost

　　3. Ordinary bolt connection

　　Advantages: convenient loading and unloading, simple equipment

　　Disadvantages: low bolt accuracy should not be cut; When the bolt precision is high, the processing and installation are complicated, and the price is higher

　　4, high strength bolt connection

　　Advantages: Friction shear deformation is small, elastic performance is good, especially suitable for the structure with dynamic load. The bearing capacity of the bearing type is higher than that of the friction type and the connection is compact

　　Disadvantages: friction surface treatment, installation process is slightly complex, slightly higher cost; Because of the large shear deformation of the compression connection, it should not be used in the structure under dynamic load.

　　5, the difference between ordinary bolt and high strength bolt

　　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, requiring quenching and tempering heat treatment to improve the comprehensive mechanical properties. The high intensity is divided into 8.8, 10.9 and 12.9. From the strength grade: high strength bolt commonly used 8.8s and 10.9s two strength grade. Ordinary bolts are generally 4.4, 4.8, 5.6, 8.8. According to the stress characteristics of high-strength bolts, pre-tension and friction force are applied to transfer the external force, while the shear force of ordinary bolts is transferred by the shear resistance of bolt rod and the pressure of hole wall.