Prestressing devices

(See Note preceding 3.2)

3.4.1 Anchorages and couplers

3.4.1.1 General

P(1) This section applies to anchoring devices (anchorages) and coupling devices (couplers) for application in post-tensioned construction, where:

i) anchorages are used to transmit the forces in tendons to the concrete in the anchorage zone;

ii) couplers are used to connect individual lengths of tendon to make continuous tendons.

P(2) The performance requirements, the methods of testing and the methods of attestation of conformity shall be defined in relevant standards or in European Approval documents (to be developed). P(3) In establishing performance requirements, consideration shall be given to:

i) the relative efficiency of the tendon anchorage/coupler assembly in comparing the actual value of the failure load of the assembly with that of the tendon;

ii) the elongation of the anchored/coupled tendon at failure;

iii) the fatigue strength of the anchored/coupled tendon;

iv) the load which can be transferred by the anchorage to the concrete, taking account of the location of the anchorage in the cross-section, the spacing between anchorages, the concrete strength and the reinforcement in the anchorage zone.

P(4) Requirements for the use of anchorages and couplers, shall be defined in technical approval documents. Detailing of anchorage zones shall comply with 4.2.3 and 5.4.

P(5) When defining test methods, consideration shall be given to two modes of testing;

i) Mode a: when components of known geometry and material specification have been taken at random out of production or from stock.

ii) Mode b: when components have been selected by the producer of the components or when prototype anchorages or couplers are to be tested.

3.4.1.2 Mechanical properties

3.4.1.2.1 Anchored tendons

P(1) Tendon-anchorage assemblies and tendon-coupler assemblies shall have strength, elongation and fatigue characteristics sufficient to meet the basic requirements of Chapter 2.

(2) This may be assumed if:

i) The geometry and material characteristics of the anchorage and coupler components are such that their premature failure is precluded.

ii) The elongation at failure of the assemblies is not excessive.

iii) Tendon-anchorage assemblies are not located in otherwise highly-stressed zones.

For the fatigue requirements of anchorages and couplers, see relevant Approval documents.

3.4.1.2.2 Anchorage devices and anchorage zones

P(1) The strength of the anchorage devices and zones shall be adequate for the transfer of the tendon force to the concrete and the formation of cracks in the anchorage zone does not impair the function of the anchorage.

(2) This may be assumed if:

i) The strength of the anchorage devices exceeds the characteristic breaking load of the tendon, either under static loading conditions or a limited number of load cycles.

ii) The detailing provisions of this Code are met. 3.4.2 Ducts and sheaths

3.4.2.1 General

P(1) This section applies to post-tensioned concrete construction where the tendons are tensioned in internal ducts.

P(2) For bonded tendons, where the ducts are grouted after tensioning, the shape (profile) of the duct shall permit the proper transfer of forces from the tendons to the concrete.

P(3) The performance requirements, the methods of testing and the methods of attestation of conformity shall be defined in relevant standards.

P(4) Requirements covering the use of ducts and sheaths shall be defined in technical approval documents. (5) Sheaths should consist of adequate materials as specified in relevant Standards (to be drafted).

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