GB2264128A

GB2264128A - Improvements in or relating to concrete reinforcement spacers

Info

Publication number: GB2264128A
Application number: GB9302833A
Authority: GB
Inventors: Donald Taylor
Original assignee: COMPONENT DESIGN Ltd
Current assignee: COMPONENT DESIGN Ltd
Priority date: 1992-02-12
Filing date: 1993-02-12
Publication date: 1993-08-18
Also published as: NO930476L; GB9302833D0; GB9202951D0; NO930476D0

Abstract

A spacer 1 for use in positioning a reinforcing bar 10 during the casting of a concrete coating onto a surface (eg. a pipe 11), is of variable height to provide a tolerance for the positioning of the bar 10 on the surface 11. The spacer may be of plastics, and be resiliently deformable under pressure (Figs 1, 4) to provide for the variation in height, and may comprise a first, arcuate web 2 connected across its ends by a second, transverse web 3, spaced from a limit stop 5, whereby the arcuate web 2 provides the resilience of the spacer. Alternatively, the spacer may be provided with a cam 122 (Figs 13, 14) pivotally connected to a component with an arcuate surface. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO SPACERS This invention relates to spacers for use in- positioning reinforcement within concrete during the casting thereof. The invention relates particularly, but not exclusively, to spacers used for positioning reinforcement during casting (e.g. by impingement) of a concrete coating onto a surface, e.g. a jacket around a pipe.

As used herein, the term concrete covers any hardenable cementitious composition.

In the construction of undersea oil and gas pipelines, it is conventional practice to use steel pipes which have been externally coated with a bituminous material (to confer corrosion resistance) and provided with a dense (generally relatively thin) concrete coating which provides weight for maintaining the pipe on the seabed. Such coated pipes are prepared in special plants prior to shipment for installation in the pipelines.

Within the concrete jacket, it is usual to have a reinforcement cage, for example of steel bars, which provides for additional strength. Generally such a cage comprises a helical steel rod with the turns of the helix being linked by longitudinal bars which generally extend along the inner "surface" of the helix.

Typically, the helix will approximate to the length of the pipe to be jacketed with concrete and the inner diameter of the helix will be such as to provide a predetermined spacing around the bitumen coated pipe when the latter is located concentrically within the cage.

Spacers of the appropriate dimension are then used to support and position the cage in spaced relationship from the bitumen surface.

Whilst the pipe design and coating specification provide a theoretical spacing between the reinforcing cage and bitumen coating, nevertheless production variations in the precise cage dimensions and bitumen coating thickness mean that the distance therebetween does not always correspond to the theoretical value.

Since the spacers used are of a fixed height, the departure from the theoretical value poses problems in that a spacer of a particular height to match the "theoretical" value may not actually be suitable.

It is thus conventional practice to have a range of spacer sizes available, e.g. differing by 5mm. However, this does not solve the problem completely in that (at least at certain locations) the spacing of the cage from the bituminous surface may be such that a particular height spacer is too small but the next larger height spacer is too large and can only be positioned with difficulty between the cage and the bitumen surface. It also requires a large number of spacers to be provided for a particular job, and requires the fitters to gauge which height spacer they should attach to the reinforcement cage at particular places.

In addition to the "tolerance" problem, the fitting of conventional bar spacers is time consuming because they cannot be attached during cage fabrication and must therefore be positioned after the reinforcement cage has been run loosely over the pipe diameter prior to the concrete impingement process.

Fitting spacers at this stage is difficult because the cage has to be prised up to force the spacers under it at intervals around the pipe diameter. Additionally, because of the tolerance problems the spacers may be too tight leading to even more physical difficulty in fixing or too slack leading to insecurity and potential displacement during the concrete impingement process. Displaced spacers lead to inaccuracy in reinforcement location within the jacket and potentially scrap (out of tolerance) pipes.

It is an object of the present invention to obviate or mitigate the abovementioned disadvantages.

According to the present invention there is provided a spacer for use in positioning a reinforcing bar during the casting of a concrete coating onto a surface wherein the spacer is of variable height to provide a tolerance for the positioning of the bar from the surface.

In one advantageous embodiment of the present invention, the spacer is resiliently deformable under pressure to provide for said variation in height.

The spacer preferably comprises a first, substantially arcuate web bridged by a second, transverse web, whereby the arcuate web provides for said resilience of the spacer. The transverse web may be connected at one end thereof to one end of the arcuate web, forming a hinge and leaving a gap betwee; the free end of llle transverse web and the free end of the arcuate web such that on deformation of the spacer the transverse web is able to move relatively to the arcuate web until such movement is restricted by the arcuate web.

Alternatively, the transverse web may be connected across both ends of the arcuate web.

The spacer may include a resilient resistance element provided between the webs to resist deformation of the spacer below a predetermined height. A stop may be further provided between the webs so as substantially to prevent deformation of the spacer below a predetermined height. The stop may be provided centrally of two resilient elements, or a resilient element may be provided centrally of two stops. The resilient element may for example be of hollow cylindrical (or other tubular) cross-section, with its longitudinal axis transverse to a longitudinal axis of the arcuate web.

The spacer may be provided with a reinforcing bar engaging portion so that it can easily be located on the reinforcement. The bar engaging portion may be constructed so as to be capable of engaging two mutually perpendicular reinforcing bars.

A roller may be provided in the spacer to aid positioning thereof.

In an alternative embodiment of spacer, the variation in height is achieved by virtue of the spacer being manually adjustable between a first position and a second bar supporting position.

According to a second aspect of the present invention there is provided a method of casting a concrete coating onto a surface, comprising attaching at least one spacer to a reinforcing bar, positioning the bar over the surface; and casting the concrete over the surface and the reinforcing ban ~.ere., the spacer is of variable height to provide a tolerance for the positioning of the bar on the surface.

Specific embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a side view of a first embodiment spacer according to the present invention; Figure 2 is an end view of the spacer illustrated in Fig. 1; Figure 3 is a top view of the spacer illustrated in Fig. 1; Figure 4 is a schematic illustration of a reinforcing cage provided around a pipe and illustrating also the spacer of Fig. 1 positioned on the cage; Figure 5 is a side view of a second embodiment of spacer; Figure 6 is a side view of a third embodiment of spacer; Figure 7 is a part sectioned side view of a fourth embodiment of spacer; Figure 8 is a top view of the spacer illustrated in Fig. 7; Figure 9 is a side view of a fifth embodiment of spacer; Figure 10 is a top view of the spacer illustrated in Fig. 9;; Figure 11 is a side view of a sixth embodiment of spacer; Figure 12 is a perspective view of a seventh embodiment of spacer; Figure 13 is a side view of the spacer illustrated in Fig. 12 in a tensioning position; and Figure 14 is a side view of the spacer illustrated in Fig. 12 prior to tensioning.

Referring to Figs. 1 to 4, there is illustrated a variable height spacer 1 which is a one-piece plastics moulding arc which comprises an arcuate web 2 bridged by a further web 3. Provide above the web 3 is a clip formation 4 by means of which the spacer may be mounted on a reinforcing cage (see below). Centrally positioned on the concave surface of the arcuate web 2 is a limit stop 5 on either side of which are positioned compressible resistance elements 6.

The resistance elements 6 are generally tubular and extend transversely of the arcuate web 2. Limit stop 5 is a.so hollow but of generally rectangular cross-section. The upper surfaces of the resistance elements 6 are positioned a certain distance (e.g. 2mm) below the lower surface of web 3 and are positioned a certain distance (e.g.

2mm) above the top of limit stop 5. For example, the height of the spacer from the lower surface of the arcuate web 2 to (a) the lower surface of web 3 may be 27mm, to (b) the upper surfaces of resistance elements may be 25mm, and (c) to the upper surface of the central limit stop may be 23mm. The reason for this positioning will be described below.

The lower surface of arcuate web 2 is arcuate in end view (see Fig. 2) and has rounded side edges. The width of the spacer is sufficiently broad so that the pressure exerted by the spacer onto a surface is minimised.

The clip 1 is intended for use in positioning a reinforcing cage 10 around a bitumen coated pipe 11 (see Fig. 4). The cage 10 comprises a helix 12 of steel rod whereof the turns are connected by internal longitudinal reinforcing rods 13. More particularly, clip 1 is intended to be mounted at the intersections of the helically wound rod 12 and the longitudinal rods 13. To this end, the clip formation 4 comprises two clips 7 and 8 (within which a rod 13 may be positioned) between which is a further clip 9 which will engage the helical rod 12.

It will be appreciated from the foregoing description that the spacer 1 may be resiliently compressed (this being allowed by virtue of the arcuate web 2) up to a point at which the lower surface of the web 3 contacts the upper surfaces of resistance elements 6. These elements resist but do not prevent further movement of web 3 which is able to continue its movement until it meets the limit stop 5.

In use, spacers 1 are clipped to the reinforcing cage at the intersection of the helical winding 12 and longitudinal rods 13 as illustrated in Fig. 4. For example, for a length of pipe of approximately 1300mm (40 ft), 90 spacers may be clipped to the reinforcing cage.

A pipe is then inserted relatively into the reinforcing cage.

As the pipe moves relatively past the spacers, variation in tolerances along the cage and the bitumen surface, will mean that some spacers will be of a greater size than the distance between pipe and cage and some will be less.

Those which are of greater size will be compressed (as described above) as the cage moves relatively over the pipe. The compressed spacers will "bump" along the surface of the bituminous coating rather than sliding freely, because of the friction between the bitumen and the spacer. The spacers will not damage the surface of the bitumen, however, because of the shape of the undersurface of web 2. If any spacers have been incorrectly positioned on the cage, the rounded edges of web 2 will ensure that these spacers do not gouge into the bituminous coating of the pipe.

For a spacer positioned at a location with a larger distance between cage and pipe than nominal, the spacer will be in an uncompressed condition. The spacers will stay in the uncompressed condition until such time as a force is applied to the cage (e.g. during rotation of the pipe in the concrete impingement machine) causing the spacing to decrease. The spacer can then compress to prevent the cage contacting the pipe.

For a spacer positioned with a nominal distance of pipe to cage, the spacer will be compressed so that the lower surface of web 3 moves towards the upper surface of resistance elements 6. Upon contact with the resistance elements 6, the web 3 will encounter resistance so that compression of the spacer is resisted until web 3 contacts limit stop 5.

The spacer will not compress further than allowed by the central limit stop 5, giving the spacer a large resistance to compressive forces enabling the spacers to support the weight of the pipe when, for example, the pipe and cage are transferred to a concrete impinging plant. The reinforcing cage also has a slight resilience (because it is formed of steel bars), and may give slightly to allow a spacer to be used in an initially smaller gap between the pipe and the cage than the size of the spacer when fully compressed.

Referring now to figures 5 to 11, there are illustrated spacers which are similar in structure to the spacer of figures 1 to 3, and which operate in a similar manner. Like features to the spacer of figures 1 to 3 are given like reference numerals.

In figure 5, there is illustrated a spacer 50 having an upstanding central formation 51 provided in place of cylindrical resistance elements 6 and limit stop 5 of figs. 1 to 3. Formation 51 comprises a rectangular sectioned limit stop 52 having two upstanding resistance elements in the form of wings 53. The wings 53 extend upwardly in a diagonal direction from the upper surface of limit stop 52 and have horizontal ends 54.

On compression of spacer 50, for a nominal spacer distance, the lower surface of web 3 is compressed onto the horizontal ends 54 of wings 53. Further compression below a nominal spacing has to take place against the resistance to compression of wings 53, and results in the web 3 resting on the upper surface of rectangular section limit stop 52. Compression below this size cannot take place.

In Figure 6, there is illustrated a spacer 60, provided with resistance elements in the form of wings 61 depending from the lower surface of web 3. A flat area 62 is provided on web 3 between the wings 61. A central, upstanding limit stop 63 is provided on arcuate web 2.

On compression of the spacer, "nominal" size is reached when the wings 61 come to rest on the surface of limit stop 63. Further compression to below nominal size must work against the resistive force of wings 61. The spacer is fully compressed when the upper surface of limit stop 63 contacts the flat area 62 provided between wings 61.

In figures 7 and 8, there is illustrated a spacer 70 wherein the arcuate web 71 is provided with two flat areas 71a and 71b for ease of use of the spacer. The central web 72 is not joined across both ends of the arcuate web 71, but is connected only at one end, forming a hinge 73. The free end 74 of arcuate web 71 stops below the central web 72, leaving a gap for movement of the free end 75 of central web 72. The free end 75 of the central web is provided with a depending lip 75a. A central cylindrical resistance element 76 is provided between the two webs, with two limit stops 77 provided either side thereof. Reinforcing bar clips 7,8 and 9 are provided on the upper surface of central web 72.

On compression of the spacer, the central web 72 first moves towards the arcuate web 71 until it rests on the upper surface of cylindrical resistance element 76. Further compression results in the deformation of the resistance element 76 until the central web 71 rests on the end 74 of the arcuate web. Lip 75a ensures that the end 74 does not slip out of alignment with the central web 72. Still further compression of the spacer is achieved by deformation of the arcuate web 71 until the central web rests on limit stops 77.

In figs. 9 and 10, a spacer 90 is illustrated, wherein arcuate web 91 has an indented portion for ease of positioning. Central web 92 is connected to arcuate web 91 and one end thereof, forming a hinge 93.

The free end 94 of arcuate web 91 stops below the central web 92, leaving a gap for movement of the free end 95 of central web 92. A depending lip 95a is provided on the end 95 of central web 92. A central cylindrical resistance element 96 is provided between the two webs, with a limit stop 97 provided centrally therein. Reinforcing bar clips 7,8 and 9 are provided on the upper surface of central web 92.

On compression of the spacer, the central web 92 first moves towards the arcuate web 91 until it rests on the upper surface of cylindrical resistance element 96. Further compression results in the deformation of the resistance element 96 until the central web 91 rests on the end 94 of the arcuate web. Lip 95a ensures that the end 94 does not slip out of alignment with the central web 92. Still further compression of the spacer results in deformation of the arcuate web 91 until the central web rests on the limit stop 97.

Figure 11 illustrates a spacer 110 having an arcuate web 111 connected across its ends by a central web 112. A central resistance element 113 is provided between the webs. Side members 114 depend from the central web 112, and support a roller 115 between them. The roller 115 projects through the arcuate web 111 to enable it to roll along a surface. Reinforcing bar clips 7,8 and 9 are provided on the upper surface of the central web 112.

As the spacer is positioned about a pipe, the roller 115 rolls along the surface to be coated so that the spacer does not gouge into the bituminous coating on the pipe. As the spacer is compressed, the arcuate web 111 and the side members 114 deform until the central web comes to rest on the resistance element 113.

Referring now to figures 12 to 14, there is illustrated a further embodiment of spacer 120 in accordance with the invention. The spacer 120 comprises an arcuate web 121 and a cam 122. The arcuate web has reinforcing bar clips 123 and 124 provided at each end thereof formed so that two mutually perpendicular reinforcing bars may be gripped by the spacer. A central web 125 is provided on each side of the arcuate web, each central web 125 being provided with an aperture 126. A flat 127 is provided on the lower surface of arcuate web 121.

The cam 122 is of a rectangular shape and has recesses 128a and 128b which respectively run (at right angles to each other) along a longitudinal edge and a widthwise edge thereof. Lugs 129 are provided on each side of cam 122 and locate in apertures 126 of the arcuate web portion whereby the cam is rotatably mounted therein. Lifting lugs 130 are also provided on cam 122.

In use of the illustrated spacer, the spacer is clipped to a reinforcing cage for a pipe at an intersection of a helical bar and a longitudinal bar by means of the clips 123 and 124. The longitudinal bar rests in recess 128a in the longitudinal edge of the cam. The cage is then moved relatively over the pipe. The spacer is held clear of the surface of the pipe because the depth of the spacer when clipped to the cage by both clips is less than the nominal distance between cage and pipe, by an amount greater than the expected tolerances between the cage and pipe.

When the cage is in place about the pipe, clip 124 (attached to the longitudinal bar) is released. Lugs 130 are then grasped and lifted. The lifting action of the lugs causes the cam to pivot about lugs 129. The lugs 130 are moved along an arcuate path, which causes the recess 128a to slide past the longitudinal bar, until the bar rests in the recess 128b in the widthwise edge of the cam 122. The camming action caused by this movement urges the arcuate web 121 downwards by pivoting about clip 123 (which is clipped to a helical bar). The surface of arcuate web 121 slides past the surface of the pipe until the longitudinal bar has located in recess 128b in the widthwise edge of cam 122. The arcuate web 121 is then resting on the flat 127 of the web, which provides stability to the spacer.

It will be appreciated that the spacer can be clipped to the cage before location thereof over the pipe, and then adjusted to support the reinforcing cage. The cam may be of a shape other than a rectangle so as to be adjustable to a number of different heights.

Correspondingly, a plurality of flats 127 may be provided for stably maintaining the spacer at different height positions.

Claims

1. A spacer for use in positioning a reinforcing bar during the casting of a concrete coating onto a surface wherein the spacer is of variable height to provide a tolerance for the positioning of the bar on the surface.

2. A spacer as claimed in claim 1, which is resiliently deformable under pressure to provide for said variation in height.

3. A spacer as claimed in claim 2, comprising a first, substantially arcuate web bridged by a second, transverse web, whereby said arcuate web provides for said resilience of the spacer.

4. A spacer as claimed in claim 3, wherein the transverse web is connected at one end thereof to one end of the arcuate web, forming 2 hinge and leaving a gap between the free end of the transverse web and the free end of the arcuate web such that on deformation of the spacer the transverse web is able to move relatively to the arcuate web until such movement is restricted by the arcuate web.

5. A spacer as claimed in claim 3, wherein the transverse web is connected across both ends of the arcuate web.

6. A spacer as claimed in any of claims 3 to 5, wherein at least one resilient resistant element is provided between the webs to resist deformation of the spacer below a predetermined height.

7. A spacer as claimed in claim 6, wherein a stop is further provided between the webs so as substantially to prevent deformation of the spacer below a predetermined height.

8. A spacer as claimed in claim 7, wherein the stop is provided centrally of two resilient resistant elements.

9. A spacer as claimed in claim 7, wherein a resilient resistant elements is provided centrally of two stops.

10. A spacer as claimed in any one of claims 6 to 9, wherein the at least one resilient resistant element is tubular, with its longitudinal axis transverse to a longitudinal axis of the arcuate web.

11. A spacer as claimed in claim 10, wherein a stop is provided within the resilient tubular resistant element.

12. A spacer as claimed in any one of claims 3 to 11, wherein at least one reinforcing bar engaging portion is provided on the transverse web.

13. A spacer as claimed in claim 12, wherein bar engaging portions are provided to engage two mutually perpendicular reinforcing bars.

14. A spacer as claimed in any preceding claim, wherein the spacer is moulded in a one piece plastics moulding.

15. A spacer as claimed in any preceding claim, wherein a roller is provided in the spacer to aid positioning thereof.

16. A method of casting a concrete coating onto a surface, comprising attaching at least one spacer to a reinforcing bar, positioning the bar over the surface; and casting the concrete over the surface and the reinforcing bar wherein the spacer is of variable height to provide a tolerance for the positioning of the bar on the surface.

17. A method as claimed in claim 16 wherein the spacer is as claimed in any one of claims 1 to 15.

18. A method as claimed in claim 16 or 17 wherein the surface to be coated is a pipe, and a reinforcing structure is provided which comprises a helically wound reinforcing bar and at least one longitudinal reinforcing bar.

19. A spacer as claimed in claim 1, wherein the spacer is adjustable from a first position to a second position, the second position being such that the reinforcing bar is supported by the spacer.

20. A spacer as claimed in claim 19, wherein the spacer is adjustable to a plurality of second positions to support a reinforcing bar at different heights.

21. A spacer as claimed in claim 19 or claim 20, wherein the spacer is adapted to support two mutually perpendicular reinforcing bars.

22. A spacer as claimed in any one of claims 19 to 21, wherein the spacer comprises two pivotally connected components, a first component being adapted to rest on the surface to be coated and a second component being moveable to raise a reinforcing bar.

23. A spacer as claimed in claim 22, wherein the first component is provided with a substantially arcuate surface slidably moveable with respect to the surface to be coated.

24. A spacer as claimed in claim 23, wherein the arcuate surface is provided with at least one flat area, on which the spacer rests in said second position.

25. A spacer as claimed in any one of claims 19 to 24, wherein the first component is provided with engagement means to engage a reinforcing bar.

26. A spacer as claimed in any one of claims 19 to 25, wherein the second component raises a reinforcing bar by a cam action.

27. A spacer as claimed in any one of claims 19 to 26, wherein the second component is provided with a lug to enable the component to be raised into the second position.

28. A spacer as claimed in any one of claims 19 to 27, wherein the second component is provided with a recess for supporting a reinforcing bar.

29 A method of casting a concrete coating onto a surface, comprising, attaching at least one spacer to a reinforcing bar, positioning the reinforcing bar over the surface, adjusting the spacer from a first position to a second position in which the reinforcing bar is supported on the surface by the spacer, and casting the concrete over the surface and the reinforcing bar.

30. A method as claimed in claim 29, wherein the spacer is as claimed in any one of claims 19 to 28.

31. A method as claimed in claim 29 or 30, wherein the surface to be coated is a pipe, and a reinforcing structure is provided which comprises a helically wound reinforcing bar and at least one longitudinal reinforcing bar.

32. A spacer substantially as hereinbefore described, with reference to figures 1 to 3; 5; 6; 7 and 8; 9 and 10; or 11 of the accompanying drawings.

33. A spacer substantially as hereinbefore described, with reference to figures 12 to 14 of the accompanying drawings.