The working characteristics of tower cranes determine the characteristics of standard section connecting bolts, which cannot be overcome. To this end, the tower crane is connected to the standard section connecting bolts of the tower crane with high-strength bolts. Regarding the specifications of tower cranes and the description of each tower crane, the installation of this bolt connection requires pre-tightening force during the installation process, and different pre-tightening force values are given for different specifications.
For accurate application, it is necessary to measure the torque of the bolt on the bolt according to the torque coefficient of the high-strength bolt and the above-mentioned 8.8 M24 bolt, and its theoretical preload torque is about 700n m. The tower crane standard section relies on the top of the tower crane, and assembles a part of a section together to form the entire tower. The function of supporting the upper working unit is mainly to bear the axial pressure, level, bending moment and torque. The bolt pre-tightening force of the installed tower crane cannot meet the specified pre-tightening force requirements, which is an important reason for the loosening of the bolts.
In addition, when the tower crane is suspended up, the standard section of the spring arm is connected to the contact surface, the standard section is connected to the contact surface and pressed, and under the same torque, the pre-tightening force of the bolts on both sides is equal at this time. When the tower crane rotates, the tower boom is changed, the contact surface of the standard section of the tower crane is changed, and the force on the bolt is large, especially the direction of the boom is in the opposite direction, the surface on the contact arm of the original standard section is pulled, and the bolt's contact surface is pulled. The tension is greatly reduced, and there may be no preload when the original preload is too high beyond the correct value. This is another important reason for the loosening of the standard section bolts.
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