GB1452371A - Device for use with a jack in post-stressing the strands of a cable-reinforced concrete structure - Google Patents

Abstract

1452371 Tensioning cables 279030 ONTARIO Ltd 15 Jan 1974 01918/74 Heading F2G Apparatus for stressing the strands 11 of a post-stressed cable-reinforced concrete structure 10 in which the strands of the cable are disposed within a conduit in the concrete structure comprises an annular bearing plate 13, embedded in the structure 10 and having an outwardly flaring frusto-conical passage therethrough, an anchor head 20 with a frustoconical surface seating within the plate 13 and with a plurality of passages 21 therein to receive the strands 11, the passages 21 being flared outwardly of the structure 10 to accommodate tapered grips 24, a centre-hole hydraulic jack 30 bearing on the plate 13 through an annular stool 32, and the strands 11 passing through a central bore 31 in the jack 30 to an auxiliary anchor head 40 carried by the annular piston 38 of the jack 30 and wherein the strands 11 are anchored by tapered grips similarly disposed to the grips 24, the arrangement being such that with the strands 11 secured to the anchor head 40 the piston 38 can be extended to stress the strands, the process being repeated to achieve the desired tension by securing the strands to the head 20; retracting the piston and then securing the strands in the head 40. After final tensioning the strands 11 are secured by the grips 24 in the head 20, the jack is removed and the excess cable cut off. The grips 24 are held in place by a template 35 having slots 36 to pass the strands 11 and movable within the stud 32. The grips 24 may be pushed into engagement with the strands 11 when desired by manual rotation of rods having knurled heads 37c bearing on wings 34 on the template 35 are screwed into the stud 32. The grips for the auxiliary anchor head 40 are circumferentially grooved and held in slots in a template 45 by retaining bars 47. A locating template 50 having apertures 57 for the strands 11 is slidable along the strands within the jack 30 and stud 32. In an alternative embodiment the jack 30 is replaced by a jack having a solid piston, yokes being provided to enable either the piston or cylinder to bear on the plate 13 or to carry an auxiliary anchor head for the strands 11.