Tension anchors are structural elements operating in traction that transmit power to the ground through a steel strand armor or self-drilling rods (or hollow bars) with improved adherence.
The most common use of the anchors is inside the supporting structures of the excavations, together with micropiles or piles (in berliner walls) or with diaphragm in c.a.; by increasing the tension anchors class it is possible to carry out excavations even at high depth without making very heavy vertical structures.
The scope of the tie rods varies depending on the number of strands, from 15 to over 120 tons, or on the diameter of self-drilling rods.
These are the functional parts of a tie rod:
Based on the temporary life of their action, anchors can be classified in: – provisional, with a time-limited function, as it is no longer required once the structure is completed and – permanent, which need adequate protection against corrosion as to guarantee a duration equal to that of the supporting structure.
The installation phases of anchors can be summed up as follows:
Tie rods are structural elements operating in traction, used to secure rock faces and anchor to the ground bulkheads and retaining walls.
In general, the function of the anchor is to ensure that the work is static, in areas where the soil offers the possibility of absorbing the stresses.
We consider anchoring tie-rods those structural elements connected to the ground or to the rock that act to get traction. Traction forces are applied to anchored structure by means of a distribution plate (with anchor head).
Depending on type of stress, tie rods can be:
- Passive anchors, in which tensile stress rises after deformation of the anchored work;
- Active anchors, in which tensile stress is totally or partially linked to the anchorage work;
Depending on the duration of the exercise, tie rods can be:
- Provisional ties, with a time-limited function
- Permanent ties, which function is linked to useful life of the work anchored.
To sum up, ties are essential and basic construction means in special foundation works than transmit large tensile forces to almost all types of soil.
It should be noted that the consolidation of rocky friable or cracked surfaces, request injection works.
TYPES OF TENSION ANCHORS: