FR2591643A1 - IMPROVEMENTS IN DEVICES FOR EXERCISING TRACTION ON A TIE BEFORE ANCHORING - Google Patents

Abstract

For stressing the second end of a tendon (1) whose first end is already anchored on a first bearing surface of a rigid structure (5), with a view to anchoring this second end on a second bearing surface (3) of the said structure after stressing of the said tendon, use is made of a device comprising a longitudinal stressing jack (V1) whose stationary element (9) is capable of bearing on the second bearing surface (3), a first temporary clamping jaw (30) of the above second end, which jaw is integral with the axially movable element (10, 11) of the jack, and a second temporary clamping jaw (20) of the abovementioned second end, which jaw is integral with the fixed element (9) of the jack. The two jaws work in succession in order to grip the tendon to be stressed during the to-and-fro action of the stressing jack and the clamping pressure of their jaws (32, 22) is applied to the tendon in exclusively transverse directions.

Description

Improvements to devices for exercising a

  pulling on a tie rod before anchoring.

  The invention relates to the tensioning of tie rods, a first end has been previously anchored on a first anchor range of a rigid structure. It relates more specifically to the devices for exerting traction on the second end of such a tie rod for anchoring on a second anchoring range of the rigid structure, after tensioning said tie rod, so as to permanently solicit the

two litters towards each other.

  Such works are for example made up of

  concrete, in which the tie rods provide the

  stress of this concrete by post-tension.

  The works in question could also

  be of any other type, and in particular bridges

  hanged, whose tie rods would then constitute the

banns.

  The invention relates more particularly to

  mid tension devices of the kind in ques-

  those for which the grip of the pulling end can be secured by provisional tightening.

  of a jaw whose jaws overlap this extremity

  tee, said clamp being generated by means of a jack

  fed by a fluid under pressure.

  This is the case for example when the tie rod is

  consisting of parallel flat ribbons superimposed with

  depositing pads at the jaw,

  as taught by the French Patent No. 85 17463.

  In known tensioning devices of the kind in question, means are provided for tightening

  the jaw around a portion, the end of ti

  to reach, on the side of the corresponding anchor span, away from the structure, and then to move the clamped jaw away from said anchor range until the desired tension is obtained in the tie rod, after which the taut pull is anchored to the reach and the

  jaw is loosened and unobstructed.

  When the tie rod is relatively long, the anchoring distance indicated between the jaw and the anchor range is itself relatively large and, as the traction forces to be generated are then

  themselves relatively high, we are obliged to

  of particularly cumbersome, heavy and difficult to implement traction tools,

  which can be a major disadvantage, especially

  when traction is to be performed on the spot,

  in places that are often difficult to access.

  The object of the invention is, above all, to eliminate this drawback. For this purpose, the traction devices according to the invention also comprise a first pulling clamping jaw which is itself integral with the axially movable element of a longitudinal traction cylinder whose fixed element is able to bear on the

  anchorage range and they are essentially characterized

  in that they further comprise a second gripping jaw secured to the element

fixed traction cylinder.

  In preferred embodiments, there is

  In addition, one or both of the following provisions are provided: the jaws and the jack are actuated by pressurized fluids and means are provided for automatically and repeatedly controlling the cycle of the fluid intake and exhausts. capable of producing the following operations: tightening of the first jaw, complete output of the traction cylinder, tightening of the second jaw, loosening of the first jaw and complete retraction of the jack

  the new tightening of the first jaw

  re starting the second cycle and the following being

2 5 9 1 6 4 3

  followed by loosening of the second jaw, - the tie rod is constituted by a bundle of parallel flat ribbons and each clamping jaw

  includes a rigid plate pierced by a transverse opening

  poured by said bundle of ribbons, a plurality of rigid plates each having a central portion interposed contiguously between two successive ribbons and two portions protruding transversely beyond these ribbons and resting on the plate, two prismatic corners arranged on either side of the platelet-ribbon assembly and each having a planar face applied against a ribbon and an opposite oblique face, the oblique faces of the two corners being oriented so as to converge in the direction which is moving away from the structure, a surrounding frame the corners and having two sides shaped so as to slide

  against these corners and to tighten the whole corners-

  platelets when asked for the opening

  ge, and a cylinder whose fixed element is integral with

  the plate and whose movable element, movable

  Like ribbons, it is attached to the frame.

  The invention comprises, apart from these arrangements

  main provisions, certain other provisions which are preferably used at the same time and of which it will be

  more explicitly question below.

  In what follows, a preferred embodiment of the invention will be described with reference to the

  drawings attached in a manner that is of course not

  tative. FIG. 1, of these drawings, shows in schematic longitudinal section a device for putting under

  voltage established according to the invention in its state of rest.

  Figures 2, 3 and 4 show the same arrangement

  schematic longitudinal half-section in resis-

  three stages of its operation.

  In the example illustrated, the tie rod 1 to be energized is constituted by a bundle of parallel flat ribbons 2 each formed for example by a

  steel strip or by an element made of composite

  site (material comprising a plastic matrix reinforced by parallel continuous fibers),

  as has been taught by the patent cited above.

  It is proposed to put the tension rod 1 under consideration for anchoring on a rigid block 3

  pierced with an opening 4 and carried by a book 5 in bene-

your already taken.

  To simplify the description that follows, we

  ask that the end to anchor of target 1 opens

  vertically upward above the structure in

  your. But any other orientation would of course be conceivable without departing from the scope of the invention: one can even observe that in practice it is the horizontal orientation which is most common for the ends

of anchors to anchor.

  The tension device considered comprises a platform 6 hollowed at its center by an opening 7 itself traversed by the tie rod 1, said platform being supported at a certain distance above the

block 3 with a base 8.

  A traction cylinder V1 comprises a cylinder 9 of vertical axis integral with the platform 6 and a

  piston 10 whose stem 11 opens vertically to-

above this cylinder 9.

  The latter is served with compressed fluid by

  intake and exhaust pipes or

12,13.

  The rod 11 is extended at its top by a horizontal rigid plate 14 itself pierced by a

  central opening 15 traversed by the tie rod 1.

  The platform 6 and the plate 14 bear each

  cune a 20.30 jaw clean to grab the tie rod 1 to

corresponding level.

  Each of these jaws 20, 30 comprises: a plurality of plates 21, 31 each comprising a central portion interleaved contiguously between two strips 2 and two projecting end portions resting on the corresponding plate 6 or 14, two prismatic corners 22, 32 having each a planar face applied contiguously against a ribbon 2 and an opposite oblique face, the oblique faces of the two corners converging upwards, - a frame 23, 33 having two sides conforming to specific wedges to slide against the oblique faces of the corners above in order to exert an effort of

  horizontal tightening on these and on the

  lages of ribbons and plates that they frame

  when a wedging force is applied vertically

  downwards on this frame, and a clamping cylinder V2, V3 capable of generating such a force and comprising a cylinder 24, 34 of vertical axis integral with the corresponding plate 6 or 14 and a piston 25, 35 whose stem 26,36 is attached to the

concerned 23,33.

  Each clamping cylinder V2, V3 is served with pressurized fluid by intake lines

  and exhaust or conversely 27,37; 28.38.

  Mutual contact surfaces platelets-

  ribbons, their coefficient of mutual friction (pre-

  increased strength by roughening the surfaces of the wafers and optionally hardening them by heat treatment) and the force of horizontal clamping of the tapes against the wafers must be sufficient to prevent slippage of the tapes relative to the wafers when longitudinal tension is exerted on these ribbons in the way that will be specified

below.

  The construction of all cylinders V1, V2 and V3 is revolution around the vertical axis of the bundle of ribbons 2: only these ribbons, plates, corners and frames affect other forms

than annular.

  To turn on the tie rod 1, we proceed

as following.

  Initially all the cylinders are in their "retracted" position, that is, for which the piston rod is retracted as far as possible,

  cylinder V and upwards for cylinders V and V (fig.

  Chuck 1 and vts the aut por rins 2 3

re 1).

  We begin by tightening the upper jaw around the tie rod 1 by activating the clamping cylinder V3, which lowers the piston 35 and firmly applies the frame 33

on the corners 32.

  Then we raise this upper jaw 30 into action.

  before the traction cylinder V1. which makes its stem 11 come out upwards, and this until its extension

  maximum, as shown in Figure 2, which confers

  pulling a first voltage T1.

  The lower jaw 20 is then tightened to a constant level around the tie rod 1 by activating the clamping cylinder V2. which lowers the piston 25 as well as its

  rod 26 and the frame 23 carried by the latter.

  From the instant o said low jaw

  is tight, it can take over from the

  high for the maintenance of the tension T in the

pulling 1.

  It is then safe to release this tension: - loosen the upper jaw 30 by deactivating the jack

V3. which raises its piston 35.

  - then deactivate the traction cylinder V1, which lowers

  the piston 10 and the upper jaw 30 that it supports. by returning the rod 11 in the cylinder 9

259 1,643

(Figure 3).

  Once this upper jaw 30 has reached its low position again, it is tightened again so that it in turn takes over the relay of the lower jaw 20 to maintain the tension T1 in the lower jaw.

  this low jaw 20 can then be

  and the cycle described above can be fully repeated. Each new actuation of the traction cylinder

  V1 gives the tie 1 additional traction.

  The above cycle is repeated until the tie rod 1 is subjected to the desired total tensile value T, the travel traveled by the traction piston during the last cycle can be only one.

fraction of its total course.

  The order of these successive cycles is advantageous

  it is rendered automatically by making the tool understand a suitable pressurized fluid dispenser and an apparatus capable of measuring the tension applied on the tie rod 1 by the traction cylinder during each active phase of operation of this jack

  corresponding to the progressive exit of its rod 11.

  When the final tensile value T is reached, the tie rod 1 is anchored on the block 3.

any desirable way.

  For this purpose, for example, one uses a

  choire 40 similar to those described above, that is to say comprising: - intermediate plates 41 each having a central portion interposed contiguously between the ribbons 2 and two transversely protruding end portions resting on the block 3, two prismatic corners 42, a frame 43 capable of coacting with the corners 42, and a jack V4 itself comprising a cylinder 44 secured to the encroachment 8 and an extended piston 45

259 1,643

  downwards by a rod 46 able to bear against the frame 43, said cylinder V being served by intake and exhaust pipes of

pressurized fluid 47,48.

  The anchoring is then achieved by activating the jack V4 in the direction that irreversibly solicits the

frame 43 down.

  This anchoring could be achieved in any other desirable manner, for example by tightening the tie rod 1 between two rigid bars urged towards each other by means of bolt-nut systems with high strength, all of these bars and of these systems framing the stack of ribbons 2 and bracing plates

41 to tighten.

  The anchorage thus described in turn

  leaving the two clamping jaws 20 and 30 for maintaining the tension T in the tie rod 1 so that these two jaws can be loosened (FIG. 4), then disengaging the set of tensioning tools, which

  can be used to tension another

  rant. Following this, we obtain a device for

  tension, the constitution and functioning of which

  sufficiently result from the foregoing.

  This device has many advantages over those previously known and, in particular, the following: - the actual travel of the traction cylinder required to apply the desired tension T on the tie rod 1 can be reduced to a very low value since the race total traction is here divided by the number of reciprocating cycles of the traction cylinder V1 which have been described above; this reduction of

  stroke can significantly reduce the

  sions and weights of the entire device, which facilitates its implementation,

  - the gripping jaws can easily be

  tightened during successive cycles and the desired tension T can be accurately applied to the tie rod 1 because of the total independence that exists between this tension and the clamping forces of said gripping jacks,

  - by playing on the obliquity of mutual plane faces

  By coagulating the corners and frames, it is possible to adjust at will the wedging forces to be developed by each of the cylinders V2, V3 and V4 to generate determined clamping forces and in particular to obtain for these forces

relatively weak.

  It goes without saying, and as it follows from elsewhere

  their already of the foregoing, the invention is not limited

  in no way to those of its modes of application and

  which have been more especially envisaged; she

  embraces, on the contrary, all variants.

Claims (3)

  1. Device for exerting traction on the   second end of a tie rod (1), the first of which   tremity is already anchored on a first litter of   casting of a rigid structure (5). in order to anchor this second end on a second anchoring surface (3) of said structure, after tensioning said tie rod, comprising a first provisional clamping jaw (30) of said end, jaw itself secured   axially movable element <10.11) of a long cylinder   longitudinal traction (V1) whose fixed element 19) is adapted to bear on the anchor range (3), characterized in that it further comprises a second   the temporary clamping jaw (20) of the second end   miter of the tie rod, jaw secured to the fixed element (9) of the traction cylinder (V1).   2. Traction device according to claim 1, characterized in that the clamping jaws (20,30) and the jack (V1) are actuatable by fluids under pressure and that means are   intended to automatically control repeatedly   the cycle of the admissions and fluid exhausts to produce the following operations: clamping the first jaw (30), complete output of the traction cylinder (V1)., clamping the second jaw (20). loosening of the first jaw (30) and complete retraction of the traction cylinder (V1), the new tightening of the first jaw which starts the second wheel and the   following, followed by loosening of the second jaw.   3. Traction device according to any one   of claims 1 and 2, characterized in that the   rant (1) is constituted by a bundle of parallel flat ribbons (2) and in that each clamping jaw (20, 30) comprises a rigid plate (6.14) pierced with a   opening (7.15) traversed by said bundle of ribbons. 259 1,643   1 1 a plurality of rigid plates (21,31) each having a central portion interposed contiguously between two successive ribbons and two portions protruding transversely beyond these ribbons and resting on the plate, two prismatic wedges (22,32) arranged- of   on both sides of the platelet-ribbon   each having a flat face applied against a ribbon and an opposite oblique face, the oblique faces of the two corners being oriented so as to converge in the direction   away from the work (5), a frame (23,33) encompassing   corners and having two sides shaped so as to slide against these corners and to tighten the whole wedges-pads-ribbons when it is stressed towards the work, and a cylinder (V2, V3) whose fixed element (24 34) is integral with the plate and whose movable element (25,26; 35,36) is movable parallel to the ribbons, is attached to the frame.