In the first articles of the heavy-duty anchor guide, we dealt with the type of base material and its requirements for fastening elements. The third part focuses on the anchoring methods. We shed light on the function principles and fastening elements and their advantages and disadvantages.
We generally differentiate between three physical function principles of anchoring: friction lock, form-fit and adhesive bond. Let's look at these anchoring methods in detail:
Friction lock
Expanding individual components within the borehole creates friction that securely fixes the anchor in the surface. We differentiate between torque-controlled and displacement-controlled expansion: The nut of the through bolt or the safety bolt must be tightened with a defined torque in order to fully expand the expansion sleeve. The metal cone must travel a certain distance inside the drop-in anchor in order to properly expand the sleeve in the borehole. The ETA-controlled setting tool ensures the correct distance.
Advantages:
- Easy assembly (no setting tools, exception: drop-in anchors)
- Immediate load-carrying capacity (no curing times)
- Self-locking load bearing capacity: As soon as load is introduced via the add-on part, the cone bolt continues to pull into the sleeve. It continues to expand. (Exception drop-in anchor)
- Safety bolt with double cone for higher load bearing capacity
Note:
- Anchors with a large expansion require higher minimum centre and edge distances
- Expansion anchors are not removable
- Expansion anchors are only suitable for solid building materials (usually concrete) or, after a suitability test, for solid and natural stone
