GB1151708A - Apparatus for Tensioning and Anchoring Stressing Members Forming Together a Stressing Cable - Google Patents

Abstract

1,151,708. Wire strainers. LOSINGER & CO. A.G. 19 Aug., 1966 [16 Sept., 1965; 25 May, 1966], No. 37344/66. Heading F2G. A tensioning and anchoring device for concrete reinforcement strands 2 comprises an anchor head 5 having a plurality of parallel part-cylindrical, part-conical bore holes 13 each receiving a strand and a conical wedge clamp 6, which is movable for a limited extent in the direction of release and is self-clamping in the opposite direction. The strands 2 forming a cable, which is to be tensioned and anchored in a channel 1a of a concrete structure 1 prior to tne injection of cement, pass through an embedded plate 3, anchor block and clamps 5, 6, a jack support plate 10, and a jack 7, 8 to a pullhead 9 similar to the anchor block. The support plate, which provides limitation of the wedges moment in the release direction, has a plurality of stepped bores 11 housing coil or cup springs 12 acting between the plate and the clamps 6. The strands are tensioned in a plurality of stages, the clamps disengaging from the bore holes to release the strands during tensioning by the jack but being maintained in frictional engagement with the strands by the springs and re-engaging the bore holes to clamp the strands on release of the jack. The distance the wedges move back on release of the tension on the wires to re-engage the bore holes which distance is called " the retraction slip ", is compensated for in the final stage of tensioning by insertion of a horseshoe shaped plate 14 at least as thick as " the retraction slip " between plates 10 and 3. This enables a comb-shaped plate 4, Fig. 2 (not shown), having a thickness corresponding to " the retraction slip " to be inserted between the plate 3 and anchor head 5 on final extension of the jack. On subsequent release, the head 9, the jack, plate 10 and the plate 14 may be removed. After injection and hardening of the cement, the strands can be burnt through at about plate 4 and the head and clamps re-used. In a modified embodiment, Figs. 4-7 (not shown), each clamp which was previously formed in three segments, is formed by two segments and the springs 12 are omitted. In this arrangement, shoulders 17 formed by the stepped bores in the hold-plate limits the movement of the clamps in the release direction and are said to ensure uniform " retraction slip " of the strands.