GB2148351A - Cable anchorage - Google Patents

Abstract

A cable anchorage having wires anchored in a plate 13 is filled in situwith a pre-mixed filling mix. The anchorage is pre-heated by blowing hot air from heater 19 into it and into a cover 15 around the exposed end of it. The mix is also pre-heated. Preferably a sheet (41,43 Fig. 1) of resilient material is compressed against the outer face of the anchor plate to seal the holes around the cable wires during the filling operation. In order to protect the cable wires in the case of cyclic loading, the wires are threaded individually through a deflector element (103 Fig. 9) at the cable end of the anchorage and are stressed individually. They may be threaded when the defector element is outside the anchorage, it being moved into position afterwards. <IMAGE>

Description

SPECIFICATION Cable anchorage This invention relates to a method oi filling a cable anchorage with a filling material and to cable anchorages formed by such a method.

The invention is especially applicable to the cable stays in a cable stayed structure where there is a particular need for an anchorage which can withstand cyclical loading, but is in principle applicable to other anchorages of other cables, e.g. prestressing cables and hangers (also known as suspenders) of suspension bridges. The cable may consist of a single cable element or a plurality of cable elements, each element being for example a wire or a strand (a strand is a multi-wire element). For simplicity we shall generally use the term wire in this description.

In the construction of certain types of structures such as roofs or bridges it is common to use cable stays which transmit forces from for example a slab or deck to a column. Normally the stays run through a tunnel or tube in the slab or deck to the anchorage which is at the far surface. The anchorage has a nut threaded around it, which nut bears against a bearing ring set into the slab. Thus the force in the stays is transmitted via the anchorage to the nut, and from the nut to the bearing ring of the slab. In the past such stays were manufactured using conventional cables which were anchored at both ends in dead heads each having a conical internal shape in which the wires or the strands opened out and which were filled with a mixture of tin and other fusible metals at low temperatures.

Modern advances of this technique have introduced the use of tendons made up of parallel wires or strands which are anchored in heads filled with a special mortar of which the binding element is an epoxy resin. At the same time the wires or strands are anchored in an anchor plate by wedges, button heads or by some other type of anchorage.

The present invention will be described in terms of a live lower anchorage with the wires anchored by wedges, but it applies in analogous ways to dead anchorages, upper anchorages, and anchorages with wires anchored by button heads etc.

It is a considerable problem however to obtain a filling material (especially for large tendons where volume is important) which.does not shrink and whose curing temperature is within limits which do not affect the steel of the wires. Such considerations have led to the use of mixtures of epoxy resin, mineral powder and aggregates, in which the quantity of mineral powder and aggregate is great enough to reduce shrinkage of the epoxy resin to a minimum and to prevent any undue rise in temperature during the curing of the epoxy resin. The powder may be of silex or zinc or some other metal and the aggregate may be any type of heavy stone or steel balls.

However, such a filling material is very thick and viscous, and it is very difficult to introduce it into the anchorage and to fill the anchorage completely. Also, it is necessary for the temperature of the mix to be regulated. ideally the temperature should be uniform and between 20"C and 30"C.

GB-A-2,095,302 proposed a method in which the curable low-viscosity liquid component of the filling material was introduced into the anchorage first, and then the aggregate particles were added later. The liquid was then cured.

Before the invention of GB 2,095,302 the conventional method of filling an anchorage with this type of material was to do it in a factory. The anchorage would be arranged vertical and the mix poured in.

It could be vibrated to ensure that it entered the small spaces between the wires etc. Temperature control could be achieved by controlling the temperature of the appropriate part of the factory. The disadvantage of this method is that the heavy filled anchorage must be transported from the factory to the site with the cable attached.

The invention of GB 2,095,302 makes it possible to fill the anchorage on site, so that the transportation problems are avoided.

We have now developed a method of filling an anchorage on site using an aggregate-containing curable filling which is mixed before the anchorage is filled. In this method we preheat the anchorage to a predetermined uniform temperature, usually 20"C to 30 C, and preheat the mix, then pump the mix into the anchorage using a high pressure hydraulic ram. The anchorage temperature is controlled until the mix is cured, possibly the temperature is raised to about 40"C and held there for about 8 hours to ensure curing.

Because the anchorage is normally not vertical when in position on site, and because it is often convenient to fill the anchorage from below, it is necessary to use a pump to fill the anchorage.

However, the mix is so thick that conventional pumps are inadequate, especially if 40% to 50% of the total volu le of the mix is aggregate (preferably in the form of steel balls). We have found that it is necessary to use a hydraulic ram to perform the pumping operation. A thick hose, capable of withstanding high pressures, is used to join the pump to the anchorage.

In order to ensure that the mix enters all the small spaces in the anchorage, especially those between the wires, it is advisable to vibrate it after filling. Preferably the vibrator is placed inside the anchorage so that it contacts the mix and vibrates it directly. It is possible to use a vibrator on the outside of the anchorage, but in this position it vibrates the anchorage and tends also to vibrate the concrete slab in which the anchorage normally sits, increasing the effective mass operated on.

The anchorage is preferably heated by placing a cover around it and passing heated fluid through the space between the cover and the anchorage. In order to assist in the uniformity of heating, heated fluid may also be passed into the anchorage, and into the space between the anchorage and the concrete slab in which it normally sits. Thus in the normal arrangement of an anchorage described above, the cover sits around that part of the anchorage which protrudes from the slab, and prefer ably around the nut as well. The heated fluid will normally be air.

We have developed a special high pressure injection pump for pumping the filling mix into the anchorage. It is preferably a single shot pump without an inlet, since the curable liquid part of the mix, normally an epoxy resin, would tend to clog the inlet valve. Therefore it is preferable for the displacement of a single stroke to be sufficient to fill the anchorage. The pump has a hydraulic cylinder, preferably double action, one end of which has a flange. The piston rod of the hydraulic cylinder extends through the flanged end of the cylinder, and bears a piston for displacing the filling mix. The cylinder for the filling mix fits around this piston and is secured to the flange, so that the cylinder for the filling mix can be disassembled for cleaning without the hydraulic cylinder having to be disassembled.

It is advisable to clean the filling mix cylinder after every shot, and so it is preferable that it is secured to the flange by quick-release means. Likewise it is advantageous if the piston for the filling mix is secured to the piston rod by quick release means. In one embodiment the cylinder end for the mix remote from the flange has means to bear on the cylinder body axially and locate it radially, e.g. a lip extending around the end of the body.

Several (e.g. four) bolts or other connecting elements run between the flange and the cylinder end, passing outside the cylinder body. Means located at or on the flange also bear axially on the cylinder body and locate it radially. The bolts secure the cylinder end to the flange, and the cylinder body is held securely in position between them. Simply by releasing the bolts, the cylinder for the filling mix is disassembled.

In use of the method of the present invention there may be a problem with leakage of the filling mix out of the anchorage at the points where the wires pass out through the end of the anchorage.

In order to prevent this we place a sheet of rubber or other elastomeric material on the outside of the end of the anchorage, covering the wedges, and compress this against the end of the anchorage with a plate. The sheet penetrates and seals all the holes very effectively, and we have found that we can even pour water into the anchorage without there being any leakage.

Preferably there are two sheets of elastomeric material, one of which sits on the anchor plate and passes around the wedges (which normally project somewhat from the anchor plate) and the other of which sits on the first, covering the wedges and passing around the strands.

The anchorages may be filled according to the present invention either from above or from below.

A problem may occur in use of cable anchorages when the cables are put under cyclic loading. Normally the anchorage narrows as it extends away from the anchor plate, typically the anchorage has a parallel-sided portion at each end and a conical central portion. When a cable is put under cyclic loading the strands may press or rub against the anchorage at the narrowest point, or at the corner between the narrow end of the conical portion and the adjacent parallel-sided portion. It is known to place a plastic ring between the anchorage and the strands at this point to minimise the friction and damage resulting from cyclic loading.

However, at this point the strands may also contact each other, and friction between them may result in a weak point in the cable. In order to avoid this, it is known to thread the strands through a plastics plate at this position before the strands are stressed. The plate holds the strands apart. It is relatively easy to thread the strands and to position the plate while the strands are unstressed. However, we propose to perform a part of this operation with at least some of the strands stressed.

One solution is to thread the strands, unstressed, through a deflector element at a location away from the anchorage. The strands are then stressed. Preferably the strands are threaded and stressed one by one, so that some strands are already stressed before others are threaded. Subsequently the element is pushed along the stressed strands into position. The element preferably has two layers or tiers each in the form of a plate, to avoid twisting of the element as it is moved although the element may be a single plate or one or more rings. Substantial force may be needed to move the element, and this can be provided by a jack. Preferably the element is of plastics or includes a plastics plate. This solution is especially useful if the direction of threading of the strands is from the open end of the anchorage to the anchor plate.

If the direction of threading is from the anchor plate to the open end of the anchorage, then it is possible to thread the strands through the deflecting element while it is in its final position, provided that a way can be found of guiding the strands into the channels of the element. In this case, the element may take the form of a single plastics plate.

The strands are threaded and stressed individually, so that some strands are already stressed while others are being threaded. We have found two ways of guiding the strands. In the first, sleeves are placed extending through both the anchor plate and the deflecting element. The strands are introduced into these, and are guided by them through the anchor plate and through the deflecting element. The ends of the sleeves nearer to the element$than the anchor plate may be closed, so that as a strand passes through the anchorage it carries the sleeve away, which may then be removed from the strand. As an alternative to the sleeves, the side of the anchorage may have one or more apertures, allowing access to its interior.

This allows access to the strands between the anchor plate and the deflecting element. Consquently, after the end of a strand has been threaded through the anchor plate, it can be guided through the element. The windows are closed before the anchorage is filled.

One other advantage of these deflecting elements is that they close the open end of the anchorage, which makes it easier to fill the anchorage completely without much of the filling mix escaping. This result can be enhanced by placing washers on the strands which overlie the channels through the deflecting element.

It is also possible to put a deflection element in the anchorage next to the anchor plate, so that any deflection of the strand at this end of the anchorage forces the strand against the deflection element rather than against the edges of the holes in the anchor plate. The anchorage may be filled with a filling grease instead of the epoxy, provided that special strand-gripping wedges are used in the anchor plate to compensate for lack of epoxy. This form of construction allows individual strands in the anchorage to be removed and replaced, for example if one is damaged. If an entire stay needs to be replaced, this can be done strand by strand.

There are circumstances in which this would greatly facilitate repairs, and also effect a considerable economy.

It is necessary, in the fitting of gable stays, to pull the live anchorage relative to the slab away from the other end of the cable stays. This pulling operation is normally performed by pulling on the wire ends protruding through the end of the anchorage. However, there is often some friction between the walls of the anchorage and the walls of the tunnel or tube through the slab in which the anchorage is sitting. As a result, there is a tendency for the anchorage to stick and then the wedges which lock the stays to the anchor plate of the anchorage will pull out. This has the highly undesirable result that the stays cease to be locked to the anchor plate.

In order to prevent this from happening, we fit an additional plate to the end of the anchorage during the pulling operation. The wires pass through this additional plate also, and are wedged into it by a second set of wedges operating in the opposite direction from the wedges in the anchorage. Thus, when the wires are pulled, the second set of wedges lock the wires to the additional plate and pull it also. The additional plate is firmly attached to the anchorage, and so the anchorage is also pulled along.

Preferably the wedges in the anchorage are solid with the second set of wedges, either by direct contact between them or by the interposition of a member. This ensures that neither set of wedges can come out.

When the pulling operation has been completed, and the ends of the wires released, the additional plate may be removed.

An embodiment of the invention, given by way of example, will now be described with reference to the accompanying drawings, in which: Figures 1 to 4 illustrate steps of the procedure followed in filling an anchorage by a method embodying the invention, and show respectively the steps of sealing the end of the anchorage, heating the anchorage, pumping in the mix, and vibrating the mix; Figure 5 shows a pump used to pump the mix into the anchorage; Figures 6 and 7 show a cover which may be placed around the anchorage during the heating; Figure 8 shows the sealing of the end of the anchorage by rubber sheets; Figures 9, 10 and 11 show three ways of threading the strands through a deflecting element; Figure 12 shows hte deflecting element of Figure 9; Figure 13 shows a washer on a strand adjacent a deflecting element; Figure 14 shows the washer of Figure 13;; Figure 15 shows an additional plate with a second set of wedges fitted to the end of the anchorage; and Figure 16 shows a part of the anchoring plate having an auxiliary pulling wire engaged on it.

An anchorage 1, when in situ, is at the lower side of a slab 3. Around the anchorage 1 is a nut 5 which bears on a bearing ring 7 let into the slab 3.

A cable stay runs through a tubular hole or tunnel 9 in the slab 3 to the anchorage, and the wires 11 of the stay are anchored in, and pass through, an anchor plate 13 at the end of the anchorage. In this way, force in the cable stay is transmitted to the slab 3 via the anchorage 1, the nut 5 and the bearing ring 7. The anchorage sits part in and part out of the lower end of the tunnel 9.

To fill the anchorage in situ a cover 15 (Fig. 2), is placed around the part of the anchorage which protrudes beyond the end of the tunnel 9, to form an enclosed space 17 around this part of the anchorage. Preferably the cover 15 encloses the nut 5 as well. Conveniently the cover fits around but does not enclose the anchor plate 13. A heater 19 comprises a fan and electric heating resistances.

The fan blows air over the resistances and into three tubes 21, through which the heated air passes to the space 17 inside the cover, the space 23 between the sides of the anchorage and the sides of the tunnel 9, and into the anchorage itself.

One or more temperature sensors 25 are used to control the heater 19 thermostatically. The anchorage 1 is heated to and held at a uniform temperature of 20 C to 30"C.

The anchorage filling mix 27 contains a curable liquid such as an epoxy resin, and an aggregate, preferably in the form of steel balls and preferably present in 40% to 50% by volume of the mix. The mix may also contain a mineral powder such as zinc or silex. This mix is also maintained at 20 to 30"C before filling. Preferably the mixing is done in a heated van, which may be parked on or near the slab 3, and the ingredients of the mix and equipment used all kept heated. When the anchorage is at the desired temperature, and the filling mix has been prepared and is at the desired temperature, the mix is filled into the pumping cylinder 29 of a special single shot pump 31 (Fig. 3). The pump 31 also has a hydraulic cylinder 33, and this drives the pumping cylinder with an action similar to a jack.

This extremely powerful pump is necessary because the mix is so thick, and conventional pumps are not able to pump it. A thick high pressure hose 35 is used to connect the pumping cylinder 29 to an inlet tube 37 of the anchorage. The inlet tube is shown extending through the anchor plate 13, but it is possible for it to enter the anchorage through its upper end.

Preferably the pumping cylinder 29 holds enough mix for the anchorage 1 to be filled by a single stroke.

The pump 31 is mounted vertically in use.

After the anchorage 1 has been filled with mix it is preferable to vibrate it (Fig. 4). This ensures that the mix 27 penetrates all the small spaces in the anchorage 1. Preferably the vibrator 39 is introduced through the upper end of the anchorage, and contacts the mix 27 directly, though it is possible to place the vibrator in contact with the outside of the anchorage below the nut 5.

The mix is then left for the epoxy to cure The temperature of the anchorage is controlled for the curing period, and may be raised, e.g. to 40"C and held there for a suitable period, e.g. about 8 hours.

There may be a problem during the filling and curing procedure with the epoxy or other liquid leaking out of the anchorage through the holes in the anchor plate 13, especially around the wires 11 and the wedges which hold them in. In order to prevent this it is preferable to place one or more sheets 41,43 of a rubbery material such as neoprene on the lower end of the anchor plate 13 (Fig.

1). A plate 45 compresses the sheets against the anchor plate, and the material of the sheets 41,43 flows under the pressure to seal all the holes.

Figure 5 shows the pump 31 in more detail. The hydraulic cylinder 33 has a piston 47. The piston 47 is connected to one end of a piston rod 49. The piston rod 49 extends through one end of the cylinder 33 and bears on its other end the piston 51 of the pumping cylinder 29. At the other end of the hydraulic cylinder 33 is a hydraulic inlet 53 for hydraulic fluid to drive to pump. A second inlet 55 allows the pistons to be returned hydraulically.

The hydraulic cylinder 33 carries on its first end a flange 57, which in turn carries the pumping cylinder 31. The pumping cylinder can be disassembled from the flange for cleaning without affecting the hydraulic cylinder.

The pumping cylinder 31 has a cylinder end 59, remote from the flange, with an opening 61 through which the cylinder is filled and emptied.

The pumping cylinder body 63 is a separate piece from the end 59. The end 59 extends past the end of the body 63, and has a lip 65 which extends around the outside of the body 63 at its end, locating the body 63 relative to the end 59. Bolts 67 running between the flange 57 and the lip 65 attach the cylinder end 59 to the flange. Next to the flange, behind the piston 51, is a plate 69 which receives and locates the other end of the cylinder body 63. The plate 69 is also attached to the flange 57 by the bolts 67.

When the bolts 67 are tightened the cylinder end 59 is drawn towards the flange 57, and the cylinder body 63 is securely held. The pumping cylinder 31 is disassembled from the flange by removal of the bolts 67. A nut 71 holds the piston 51 to the piston rod 49, and thus the piston 51 can easily be removed after the cylinder 31 has been disassembled. Preferably the pumping cylinder is disassembled and cleaned after each stroke.

Because both cylinders are enclosed, it is not possible to see how far the pistons have moved.

Therefore a follower 73 is attached to the back of the pumping cylinder piston 51. This follower 73 extends outside and alongside the hydraulic cylinder 33, and runs in a scale 75, so that movement of the pistons can be detected.

Figures 6 and 7 show the cover 15 in more detail. It has a lower ring 77 and an upper ring 79. A fibre-glass cylinder 81 extends between the two rings. A hot air inlet duct 83 extends through the cylinder 81. The lower ring 77 bears a seal or lining 85 on which it rests. In use this is placed against the exposed surface of the bearing ring 7 or the slab 3. Attached to the upper ring 79 is a flexible seal 87 which fits around the side of the anchor plate 13 in use.

Figure 8 shows in more detail the method of sealing the holes in the anchor plate 13 using the neoprene sheets 41,43. The wires 11 extend through holes 89 in the anchor plate 13. The holes 89 are flared at each end, and at the end outside the anchorage the wires 11 are anchored by wedges 91 in the holes (see Fig.15). The wedges 91 extend slightly beyond the surface of the anchor plate 13. The temperature sensor 25 and the inlet tube 37 for the filling mix also extend in holes ine anchor plate 13.

A first neoprene sheet 41 is placed on the surface of the anchor plate 13, and extends around the protruding ends of the wedges 91. A second neoprene sheet 43 is placed on the first, and extends over the ends of the wedges 91. A plate 45, preferably of steel, is placed on the second neoprene sheet and tightened to the anchor plate 13 by screws 93. This puts the sheets 41,43 under pressure, and their material flows or creeps into all the holes in the anchor plate 13, sealing them. if any of the holes 89 for the wires 11 are not being used, it is best to block them off with plugs 95.

Figures 9,10 and 11 show three arrangements ior providing the wires 11 with deflecting means 103 at the point where they change direction from being parallel in the tunnel 9 to being splayed inside the anchorage 1. In each case, arrow 105 shows the direction in which the wires 11 are threaded through the anchorage 1.

In Fig. 9 the deflecting element 103 comprises two plastic plates 107,109 spaced apart along the length of the wires 11. The wires 11 are threaded one by one, unstressed, through channels 111 (Fig.

12) in the deflecting element 103 and then through the anchor plate 13. Each strand is stressed after it has been threaded, so that some strands are already stressed before others are threaded. At this stage the deflecting element 103 is in a readily accessible position A outside the anchorage 1, and possibly outside the slab 3. The anchorage 1 is fitted with a plastic ring 113 at the position B where the wires 11 change direction, to avoid friction between the wires 11 and the anchorage 1. After the threading and stressing, the element 103 is moved, possibly with the aid of a jack, to its final position B at the ring 113.

Figure 10 shows an arrangement in which the deflecting element 103 is placed in its final position before threading and is a single plastic plate. The wires 11 are threaded from the anchor plate 13 to the element 103. In order to guide the wires into the channels 111, sleeves 115 are provided extending through the holes 89 in the anchor plate and through the channels 111. The ends of the sleeves 115 at the element 103 are closed, so that each wire 11, as it is passed along the tunnel 9, carries its sleeve 115 away. A circlip or similar 117 holds the sleeve 115 at the outer side of tbe anchor plate 13, preventing the wire 11 from carrying the sleeve 115 away before the end of the wire reaches the end of the sleeve. Each wire 11 is threaded and tensioned individually, so that some wires will already be tensioned while others are being threaded.

In Figure 11 the threading direction is from tbe anchor plate 13 to the deflecting element 103, as in Figure 10. Again, the element 103 is a single plastc plate and is placed in its final position before threading. Instead of providing sleeves 115, in this arrangement there are two apertures 119 in the side of the anchorage 1. Thus, after the end of a wire 11 has been passed through the anchor plate 13, the apertures 119 allow access to that end, so that it can then be guided into a channel 111 of the element 103. As in the arrangement of Figure 10, the wires 11 are threaded and stressed individually. When all the wires 11 have been threaded and stressed, the apertures 119 are closed before the anchorage 1 is filled.

The deflecting element 103 also acts to close the anchorage 1, and thus assists in the filling of the anchorage. The quality of the closure can be improved by placing a washer 121 on each wire 11 on the inner (of the anchorage 1) side of the element 103, to close the channels 111 (Figures 13 and 14).

Figure 15 shows a device for holding the wires 11 secure while the anchorage 1 is pulled along the tunnel 9. The anchorage 1 is normally pulled by the wires 11. However, this reverses the direction in which the wires pull on the anchor plate 13.

Frequently there is friction between the anchorage 1 and the sides of the tunnel 9, and the anchorage resists the pulling movement. As a result the wedges 91 anchoring the wires 11 to the anchor plate 13 tend to come loose. In order to prevent this from happening, it is desirable to attach to the anchor plate 13 an additional plate 97. The wires 11 are anchored in this additional plate 97 by a second set of wedges 99, which point in the opposite way from the first set 91. The additional plate 97 is in turn attached firmly to the anchor plate 13.

Thus force from the wires 11 is transmitted to the anchorage via the second set of wedges 99 and the additional plate 97. The complete assembly moves together and there is no tendency for the wedges 91 to pull out. The wedges can be secured further if the two sets are braced against each other, either by direct contact or by the interposition of blocks 101.

At the end of the pulling operation the additional plate 97, the additional wedges 99 and the blocks 101 (if any) can be removed.

Figure 16 illustrates an alternative method of pulling the anchoring plate 13 rearwardly, so as to apply increased tension to all the wires simultaneously. Like the method of Fig. 15, this method involves the use of a stressing or pulling jack adapted to pull a plurality of wires simultaneously.

Fig. 16 shows a part of the anchoring plate 13 having one bore 89 for a stressed wire (the wire and its anchoring wedge being omitted) and, closer to the periphery of the plate 13, a further bore 121. At least three such bores 121 are provided spaced apart around the plate 13. Each bore 121 is adapted to receive, temporarily, an auxiliary length of wire 123 (e.g. in the form of strand, as shown here) which has an anchoring element in the form of a compression fitting 125 (i.e. a swaged or compressed sleeve) and which extends rearwardly from the plate 13 for a sufficient distance to enable it to be received in the gripping means of the hydraulic pulling jack which is used to move the anchoring plate. To hold the wire 123 temporarily in the bore 121 via the fitting 125, the bore has a threaded portion 127 in which a threaded sleeve 129 located on the wire 123 is engaged after the fitting 125 has been inserted in the bore 121.

Claims (21)

1. A method of filling a cable anchorage, which anchorage has a hollow body closed at one end by an anchor plate with holes therethrough for the reception of cable wires, wherein (a) the anchorage is placed substantially in its final position of rest; (b) cable wires are threaded through the said holes in the anchor plate and are held in a desired position extending through the anchorage and passing through the hollow interior of the anchorage body; (c) before, during and!or after the said threading the anchorage is heated to a predetermined substantially uniform temperature; (d) a pre-heated and pre-mixed filling mix containing a curable material and an aggregate is forced into the hollow interior of the anchorage body, to substantially fill it, by a hydraulic pump; and (e) the temperature of the filled anchorage is controlled until the filling mix is substantially cured.

2. The method of claim 1 wherein the anchorage is heated in step (c) to a temperature in the range of 20"C to 300C and wherein in step (e) the temperature of the anchorage is raised to about 40"C and is held there for about 8 hours.

3. The method of claim 1 or claim 2 wherein the anchorage is placed in step (a) with a first portion within a hole through a slab and a second portion extending from the hole beyond a surface of the slab, the first portion including the end of the anchorage body not closed by the anchor plate and the second portion including the anchor plate and the end of the body closed by it, and wherein, in step (c) a cover disposed around the said sec ond portion of the anchorage enclosing at least a major part of it, and a heated fluid is pumped into the interior of the cover, the interior of the anchorage, and between the wall of the hole in the slab and the said first portion of the anchorage, to effect the said heating of step (c).

4. The method of claim 1 wherein the filled mix is vibrated after step (d), to cause it to enter restricted spaces within the said hollow interior.

5. The method of claim 4 wherein the vibration is carried out by means of a vibrator inserted into the interior of the anchorage and placed in contact with the filled mix.

6. The method of claim 1 wherein leakage of the filling mix around the wires passing through the said holes in the anchor plate during step (d) is restrained by a layer of elastomeric material extending on the outer end surface of the anchor plate around the wires, which layer is compressed against the anchor plate by means of a further plate.

7. A hydraulic pump for use in step (d) of the method of any one of the preceding claims, the pump having a first, hydraulic, cylinder and a second, pumping, cylinder, the cylinders having respective pistons connected by a common piston rod, the said hydraulic cylinder bearing a flange on a first end, through which flange the common piston rod extends movably and to which flange is secured releasably the second, pumping, cylinder, so that the second, pumping, cylinder can be disassembled without disassembly of the hydraulic cylinder.

8. The pump of claim 7 wherein the pumping cylinder has a first end at the said flange and a second end remote from the flange, the second end having an opening through which the pumping cylinder is chargeable and dischargeable, the pumping cylinder being a single shot cylinder and having no further inlet opening.

9. The pump of claim 8 wherein the pumping cylinder has a cylinder body demountable from the said flange, and a cylinder.end at the said second end of the pumping cylinder demountable from the said cylinder body, the flange and the cylinder end being joined, when the pumping cylinder is assembled and secured to the flange, by a plurality of tension members extending between them and passing outside the cylinder body, the tension members urging the flange and the cylinder end towards each other whereby the cylinder body is held securely in place between them.

10. The pump of claim 7 in which the said piston of the pumping cylinder bears a follower which extends movably through the said flange and extends alongside and outside the hydraulic cylinder, the hydraulic cylinder bearing a scale mounted to extend adjacent the follower, whereby movement of the follower relative to the scale indicates movements of the respective pistons inside the said cylinders of the pump.

11. A method of moving a cable anchorage, which anchorage has a hollow body closed at one end by an anchor plate with holes therethrough for the reception of cable wires and which anchor plate has cable wires received in and extending through the said holes, the wires being held in the holes by wedges extending into the holes from the outer (of the anchorage) side of the anchor plate, in which method force is appiied to the anchorage to move it by pulling on the parts of the wires extending beyond the anchorage through the anchor plate, and wherein a further plate is attached to the outside of the anchorage beyond the anchor plate, the further plate having holes through it through which holes extend the wires, the wires being held in the holes of the further plate by additional wedges extending into the holes from the side of the further plate towards the anchorage, the said parts of the wires which are pulled being beyond the further plate so that force is transmitted from the wires to the further plate via the additional wedges, and thence to the anchorage, the wires being substantially relieved, where they pass through the anchor plate, of force tending to loosen the wedges of the anchor plate and the force on the wires where they pass through the further plate being so directed as to tend to tighten the additional wedges.

12. The method of claim 11 wherein the wedges of the anchor plate and the additional wedges abut each other.

13. The method of claim 11 wherein spacer members extend between the wedges of the anchor plate and the additional wedges.

14. A method of threading cable wires through a cable anchorage, wherein the wires extend, in their final threaded position, non-parallel to each other over at least a portion of their extent within the anchorage and extend substantially parallel to each other outside the anchorage, the anchorage being provided with spacer means of a material softer than the wires to space the wires apart where they change from being non-parallel to being parallel so that the wires do not abrade under cyclic loading, in which method the wires are threaded through the spacer means and stressed individually so that some of the wires are already stressed before others are threaded through the spacer means.

15. The method of claim 14 wherein the spacer means is not in its final position when the wires are threaded through it and stressed, the spacer means being moved into its final position when all the wires have been threaded through it and stressed.

16. The method of claim 14 wherein the wires extend non-parallel within the cable anchorage from the said spacer means towards an anchor plate closing an end of the anchorage, the wires passing through holes in the anchor plate, the wires being threaded through the anchorage and the spacer means from the direction of the anchor plate and means being provided during the threading operation to enable the guiding of the wires from the anchor plate to the spacer means.

17. The method of claim 16 wherein the said means to enable the guiding comprise sleeves, open at one end and closed at the other, each extending from its open end through the holes of the anchor plate and then through the spacer means to its closed end, an end of each wire being inserted into the open end of a respective sleeve and being passed along within the sleeve through a respective hole in the anchor plate, through anchorage and through the spacer means until it reaches the said closed end of the sleeve, the wire then carrying away the sleeve as its threading continues.

18. The method of claim 16 wherein the said means to enable guiding comprise at least one closable aperture in the side of the anchorage to enable manual guiding of the wires within the anchorage.

19. The method of claim 14 wherein the wires extend non-parallel within the anchorage from the spacer means towards an anchor plate closing an end ofthe anchorage, the wires passing through holes in the anchor plate, an additional spacer means of a material softer than the wires being provided in the anchorage adjacent the anchor plate to locate the wires so that they do not abrade against the sides of the holes under cyclic loading.

20. The method of claim 19 wherein the anchorage is subsequently filled with a non-setting filler, to provide an anchorage in which cable wires are individually replaceable.

21. A method of moving an anchoring plate of a tensioned cable anchorage, which plate has a plurality of tensioned wires of the cable extending through bores in it and anchored to it by anchoring means, wherein the plate is moved against the force applied to it by said wires by means of a jack which pulls a plurality of auxiliary wires, not forming part of said cable, which are temporarily anchored to said plate and extend there from in the opposite direction to the tensioned lengths of said wires of the cable.