1. The head of the anchor bolt is broken.
Reasons: the head bar is not vertical, and there is bending stress after tightening; the transition fillet of the head bar is too small, and there is stress concentration; the pre-tightening force is too large, there is a higher frequency of fluctuating load, which causes fatigue failure.
That is, the verticality between the anchor bolts and the concrete foundation plane is not enough. The anchor bolts should be installed before the tower crane. When the anchor bolts are embedded, the correction frame provided by the tower crane manufacturer should be used for positioning and installation. If the correction frame is not used or the deformed The installation of the correction frame may result in a large deviation between the pitch of the anchor bolts and the pitch of the base hole of the tower crane.This causes interference between the anchor bolt and the wall of the seat hole, causing one of the bolts to have an excessive pre-tightening force, causing the bolt to work under heavy load, causing fatigue deformation, and causing it to break.
2. The anchor bolts are sunken, pitted or rusty.
Cause: Corrosion has occurred.
3. The anchor bolt breaks in the shrinking area.
Reason: The tightening force is too large, and the excessive stress is used.
4. Shortly after screwing in, there will be a fracture, the fracture will be flat, and there will be no reduction in diameter.
Reason: The phenomenon of hydrogen embrittlement occurred.
In addition, there are the following reasons: whether the anchor bolts are over-tightened; whether the anchor bolts have shear load; whether the anchor bolts are used, whether there is corrosion phenomenon; whether the anchor bolts have higher frequency fluctuation loads.