According to Chinese national standards, the standard for torshear type high-strength bolt assemblies for steel structures is GB/T 3632-2018 Torshear type high-strength bolt assemblies for steel structures. The standard for mechanical properties of general high-strength fasteners is GB/T 3098.1-2010 Fasteners - Mechanical properties - Bolts, screws and studs. These two standards specify the classification, dimensions, materials, mechanical properties, surface treatment and other requirements of high-strength bolts for corresponding applications.
According to GB/T 3098.1-2010, high-strength bolts are mainly divided into two grades: Grade 10.9 and Grade 12.9. Among them, the nominal tensile strength of Grade 10.9 bolts is 1000 MPa, and the nominal yield strength is 900 MPa; the nominal tensile strength of Grade 12.9 bolts is 1200 MPa, and the nominal yield strength is 1080 MPa. High-strength bolts of these grades are mainly used in engineering structures with high connection requirements and large loads, such as bridges, high-rise buildings, automobile manufacturing and other fields.
In addition, the standards specify the dimensional ranges, material requirements and mechanical property indexes of high-strength bolts. The dimensions of bolts include thread diameter, thread length, total bolt length, etc., which should be selected according to actual application requirements. High-strength bolts are usually made of alloy steel to ensure their mechanical strength and corrosion resistance. In terms of mechanical properties, the standards specify clear indexes for tensile properties, yield strength, elongation after fracture and other indicators.
Designing, manufacturing and using high-strength bolts in accordance with national standards can ensure the reliability and safety of bolted connections. In engineering practice, compliant high-strength bolts should be selected according to specific engineering requirements and standard specifications to ensure the stability and safety of engineering structures.
In addition to the national standards GB/T 3632-2018 and GB/T 3098.1-2010, there are also international standard systems for high-strength bolts, mainly including ISO (International Organization for Standardization) and ASTM (American Society for Testing and Materials) standards.
Among ISO standards, those related to high-strength bolts are ISO 898-1 and ISO 898-2. ISO 898-1 specifies the mechanical property requirements for bolts, screws and studs, including core indexes such as tensile strength, yield strength and elongation. ISO 898-2 specifies the mechanical property requirements for matching nuts.
Among ASTM standards, the common standards for structural high-strength bolts are ASTM A325 and ASTM A490, which have now been integrated into the ASTM F3125 standard system. These standards are dedicated to structural high-strength bolts, where ASTM A325 applies to carbon steel and ASTM A490 applies to alloy steel, with clear provisions on chemical composition, mechanical properties, dimensions and permissible tolerances.
It should be noted that standards and specifications vary between different countries and regions. In practical applications, suitable high-strength bolts and corresponding standards should be selected in accordance with the requirements of the country or region where the project is located.
The formulation and implementation of standards and specifications for high-strength bolts help ensure the quality and reliability of bolted connections and improve the overall safety level of engineering structures. When using high-strength bolts, design, manufacturing and installation shall be carried out in strict accordance with relevant standards to ensure the firmness and durability of bolted connections.
