ANSI B18.2.1 Bolt Safety Design

ANSI B18.2.1 bolts are classified according to design requirements in the shear design: ANSI B18.2.1 Bolt Pressure Type and ANSI B18.2.1 Bolt Type. The bearing capacity of the friction type depends on the anti-slip coefficient and the number of friction surfaces of the frictional friction surface. The friction coefficient of the red rust after sandblasting (pill) is the highest, but it is greatly affected by the construction level from the actual operation. Many supervisory units It is suggested whether the standard can be lowered to ensure the quality of the project. The bearing capacity of the bearing type depends on the shear resistance of the bolt and the minimum value of the bolt's pressure bearing capacity. In the case of only one joint surface, the M16 friction type shear capacity is 21.6~45.0kN, while the M16 compression type shear capacity is 39.2~48.6 kN, which is better than the friction type. In the installation, the pressure-bearing type process is simpler, and the joint surface only needs to remove oil and rust. The tensile bearing capacity along the shaft is very interesting in the steel structure specification. The friction design value is equal to 0.8 times the pre-tension. The bearing design value is equal to the screw effective area multiplied by the material tensile strength design value. It seems that There is a big difference. In fact, the two values ??are basically the same. I have never understood why the specification should be written this way. Why do the same material use the two expressions to calculate the same value? When simultaneously receiving the shear force and the axial force of the rod axis, the friction type requirement is the ratio of the shearing force to the shear bearing capacity of the bolt and the sum of the axial force of the screw bearing and the tensile load bearing force is less than 1.0, and the pressure type requirement The square of the ratio of the shearing force to the shear bearing capacity of the bolt plus the square of the ratio of the axial force of the screw to the tensile bearing capacity is less than 1.0, that is to say, under the same load combination, the same diameter is supported. Type ANSI B18.2.1 bolts are designed to have a higher safety reserve than the friction type ANSI B18.2.1 bolts.