The core differences between Grade I and Grade II joints of steel bar couplers lie in the tensile strength indicators, application locations, and limitations on the joint percentage, which are classified according to the current industry standard “Technical Specification for Mechanical Connection of Steel Bars” (JGJ 107 - 2016).

Differences in mechanical performance indicators

Different requirements for tensile strength

Grade I joint: The ultimate tensile strength of the joint shall not be less than 1.10 times the standard value of the tensile strength of the connected steel bar, or the actual tensile strength of the steel bar.

Grade II joint: The ultimate tensile strength of the joint shall not be less than the standard value of the tensile strength of the connected steel bar.

Requirements for deformation performance

The Grade I joint has high ductility and repeated tension - compression performance, with smaller residual deformation, and can fully exert the strength of the steel bar.

The Grade II joint also needs to have high ductility and repeated tension - compression performance, but its strength reserve is lower than that of the Grade I joint.

Application scenarios and limitations

Applicable stress locations

Grade I joint: It can be set in high - stress locations and is suitable for structures with a relatively high seismic grade or extremely high requirements for connection quality.

Grade II joint: It is usually used in general building structures and is recommended to be set in locations with lower stress.

Limitations on the joint percentage

Grade I joint: In the same connection section, the percentage of the joint area can be unrestricted (up to 100%).

Grade II joint: In the same connection section, the percentage of the joint area usually should not be greater than 50%.