8.4 Design and construction considerations

(1)P The design of the anchorage and the specification for its execution shall take into account any adverse effects of tensile stresses transmitted to ground beyond the vicinity of the anchorage.

(2)P The zone of ground into which tensile forces are to be transferred shall be included in site investigations.

(3)P For pre-stressed anchorages, the anchor head shall allow the tendon or rod to be stressed, proof-loaded and locked-off and, if required by the design, released, de-stressed and re-stressed.

(4)P For all types of anchorage, the anchor head shall be designed to tolerate angular deviations of the anchor force, taking into account 6.3 of EN 1537:1999, and to be able to accommodate deformations, which may occur during the design life of the structure.

(5)P Where different materials are combined in an anchorage, their design strengths shall be assessed with due account of the compatibility of their deformation performance.

(6)P Since the effect of anchorage systems depends on their tendon free lengths, the following requirements shall be fulfilled:

  • the anchor force shall act in ground that is sufficiently distant from the retained volume of ground that the stability of this volume is not adversely affected;
  • the anchor force shall act in ground that is sufficiently distant from existing foundations to avoid any adverse effects on them;
  • measures shall be taken to avoid adverse interactions between the tendon bond lengths of anchorages that pass close to each other;

(7) Adverse interactions between the tendon bond lengths of anchorages should be avoided, if possible, by keeping a space not less than 1,5 m between them.

(8)P Only anchorage systems shall be used that have been tested by investigation tests (see EN 1537:1999) or for which successful comparable experience is documented in terms of both performance and durability.

(9)P The direction of the tendon shall normally be such as to provide self-stressing with deformations due to potential failure mechanisms. In case this is not feasible, adverse effects shall be taken into account in the design.

(10)P For grouted anchorages and screw anchorages, the characteristic value of the pull-out resistance, Ra;k, shall be determined on the basis of suitability tests according to 8.7 or comparable experience. The design resistance shall be checked by acceptance tests after execution.

(11)P The performance of the tendon free length of pre-stressed ground anchorages shall be checked in accordance with EN 1537:1999.

(12)P A sufficient lock-off force shall be used to ensure that the anchorage resistance under serviceability limit state conditions will be mobilised with tolerable head displacements.

(13)P Corrosion protection of pre-stressed anchorages shall comply with 6.9 of EN 1537:1999.

(14)P Corrosion protection of anchorages having a steel tendon shall be designed taking into account the aggressiveness of the ground environment.

(15) Suitable means, such as the use of a protective sheath or the provision of sacrificial steel, should be specified if necessary to protect steel tendons against corrosion.

Eurocode 7 Geotechnical design Part 1 : General rules