The anchorage in the concrete is produced by the foot of the spread anchor creating a wrenching cone.
The anchorage resistance depends on:
- – The concrete strength (fck)
- – The length of the spread anchor (L)
- – Distances to the edge of the concrete (TN)
- – Distances between each anchor (TN)
The larger the wrenching cone, the more resistant the anchorage. It is at its maximum when the distance between the 2 anchors is greater than 3.5 times the anchoring length (L) and the distance to the edge of the concrete greater than 1.75 times L.
The following tables indicate minimum spacing between 2 anchors and minimum thickness (Ep) of a beam.