12.1 Prestressing Equipment
12.1.1 Tensioning Equipment
12.1.1.1 The requirements of 12.1.1 shall apply to both the pre-tensioned and the post-tensioned methods of prestressing concrete except where specifically mentioned otherwise.
12.1.1.2 Prestressing steel may be tensioned by means of hydraulic or mechanical jacks.
The tension equipment shall be such that it facilitates measurement and control of application of force.
The tensioning equipment should be independently supported so that it does not induce any undesirable secondary stresses.
12.1.1.3 The anchorage provided for the temporary gripping of tendons on the tensioning equipment shall be secure and such as not to damage the tendon.
12.1.1.4 Devices attached to the tensioning equipment for measuring the applied force shall be such that they do not introduce errors exceeding 5 percent.
12.1.2 Temporary Gripping Device
Prestressing tendons may be gripped by wedges, yokes, double cones or any other approved type of gripping devices. The prestressing wires may be gripped singly or in groups. Gripping devices shall be such that in a tensile test, the wire or wires fixed by them would break before failure of the grip itself.
PART 6 STRUCTURAL DESIGN — SECTION 5 CONCRETE: 5B PRESTRESSED CONCRETE
12.1.3 Releasing Device
The releasing device shall be so designed that during the period between the tensioning and release, the tension in the prestressing elements is fully maintained by positive means, such as external anchorages. The device shall enable the transfer of prestress to be carried out gradually so as to avoid large difference of tension between wires in a tendon, severe eccentricities of prestress or the sudden application of stress to the concrete.
12.1.4 Anchorage Device
12.1.4.1 The anchorage device may be patented or otherwise, which complies with the requirements laid down under 12.1.4.2 to 12.1.4.5.
12.1.4.2 The anchoring device shall be strong enough to resist in all respects a force equal to at least the breaking strength of the prestressing tendon it anchors.
12.1.4.3 The anchorage shall transfer effectively and distribute, as evenly as possible, the entire force from the prestressing tendon to the concrete without inducing undesirable secondary or local stresses.
12.1.4.4 The anchorage shall be safe and secure against both dynamic and static loads as well as against impact (see Annex B).
12.1.4.5 The anchorage shall have provision for the introduction of a suitable protective medium, such as cement grout, for the protection of the prestressing steel unless alternative arrangements are made.