Method and device for manufacturing a road surface, a runway or the like

Abstract

 In a prestressed, post-tensioned concrete road or like surfacing consisting of a series of slab sections (3) separated by transverse expansion joints, essentially all the longitudinal prestressing members (11) of each cast in situ section are tensioned by means of hydraulic cylinder apparatus (16) fitting into the joint gaps and bearing against one of the end faces of the at least partially hardened section, and said members are held in tension by anachor means embedded close to the end faces of the section.

Description

[0001] The invention relates to a method of manufacturing a road surface, a runway or the like by at least one sequence of concrete slabs separated from one another in the concrete path by a dilatation groove, in which at least one of the concrete slabs is made by casting concrete mortar in situ on a foundation, whilst anchors of stretching elements extending in the direction of length of the concrete slab are fastened to the casing beams and in which the stretching elements are tightened after at least partial curing of the concrete.

[0002] Such a method is known. Therein first a main portion of a concrete slab is made, after which at least one head rim completing the concrete slab and bounding the dilatation groove is cast to the main portion, whilst during the manufacture of the main portion about 60% of the number of stretching elements is provisionally anchored by means of intermediate anchors arranged at the interface between the main portion and the head rim and prior to casting the head rim the 60% of the number of stretching elements is pre-tightened. Pre-tightening is carried out by means of tensile forces conducted via the two concrete slabs bounding the dilatation groove into the foundation. Therefore, the overall tensile forces are limited to the frictional forces between a concrete slab and its foundation. For this reason only about 60% of the number of stretching elements can be pre-tightened. The stretching elements of these two concrete slabs are intercoupled by means of coupling stretching elements extending across the groove anchors of the two concrete slabs. After curing of the concrete of the head rim the parts of the coupling stretching elements located in the dilatation groove are removed so that the concrete of the head rim is subjected to stress. Thus the head rim cast to the main portion is subjected to a stress amounting to only about 60% of the stress prevailing in the main portion.

[0003] From the foregoing it is apparent that the known method results in concrete slabs in which various stresses are prevailing so that it is exactly the regions of the groove transitions that are loaded most heavily during the passage of heavy vehicles, for example, airplanes are the weakest.

[0004] The invention has for its object to enhance the strength of the concrete slab at the head rim. For this purpose essentially all stretching elements of a concrete slab are post-tightened and anchored on groove anchors provided near the dilatation groove, the post-tightening force bearing on the concrete of the slab concerned.

[0005] During post-tightening, in which the external reactive forces consist of pressure forces bearing on the head rim all stretching elements can be tightened so that the stress of the stretching elements and thence also of the concrete in the head rim and in the main portion is the same.

[0006] The invention relates to and provides in addition an improved device for carrying out the method according to the invention comprising tightening means for tightening the stretching elements and being characterized in that the tightening means comprise one hydraulic, linear tightening motor, the axial length of which is smaller than the width of the dilatation groove.

[0007] The aforesaid and further features of the invention will be described more fully hereinafter with reference to a drawing. In the drawing:

Figure 1 is a perspective view of a concrete path in accordance with the invention during the execution of the method in accordance with the invention,

Figure 2 is an enlarged, partial elevation of the concrete path of Figure 1 in a further stage,

Figure 3 is an enlarged sectional view taken on the line III-III of Figure 1,

Figure 4 is an elevational view of a stretching element used in the method in accordance with the invention,

Figure 5 is a sectional view taken on the line V-V in Figure 4,

Figure 6 is a sectional view taken on the line VI-VI in Figure 4,

Figures 7 and 8 are sectional views corresponding to Figure 6 of different devices in accordance with the invention,

Figure 9 is a perspective view of a concrete path during the manufacture by another method in accordance with the invention,

Figure 10 is an enlarged sectional view of a detail taken on the line X-X in Figure 9,

Figure 11 is an exploded view of the detail of Figure 10,

Figure 12 is a sectional view corresponding to Figure 10 of a simplified detail in a final position,

Figure 13 is a perspective view of a bridge piece in the detail of Figure 12, and

Figure 14 is a sectional view of a dilatation groove with other stretching means.

[0008] By the method according to the invention a road surface, runway or the like 1 of concrete (see Figure 1) is made from at least one sequence of concrete slabs 3 separated from one another by a dilatation groove 2. Each concrete slab 3 is made by casting concrete mortar in situ on a foundation 4 between two casing beams 6 arranged at the two head ends 5 of the concrete slab and between two longitudinal beams 7. First a main portion 9 is made for each concrete slab 3 and subsequently a head rim 10 completing the concrete slab 3 is cast to the main portion 9 adjacent the dilatation groove 2. During the manufacture of the main portion 9 stretching elements 11 of stretching cables are provisionally anchored by means of intermediate anchors 8 disposed at the interface 12 between the main portion 9 and the head rim 10 and definitely by groove anchors 13 disposed at the dilatation groove 2. The stretching elements 11 arranged in the casing prior to casting of the concrete mortar are enveloped by sleeves 15 and are movable at least with respect to the surrounding concrete 14. Therefore, subsequent to partial curing of the concrete 14 each stretching element 11 can be tightened by means of known tighteners 16 each comprising a frame 17 supporting via the casing beam 6 on the concrete 14 of the main portion 9, a clamp 18 engaging the stretching element 11 and two linear hydro-motors 19 fastened to the clamp 18, the piston rods 20 of which are secured to the frame 17. When the hydro-motors 19 are energized, the stretching element 11 is stepwise tightened to the required stress.

[0009] The very long, narrow concrete slabs 3 may have an overall length of the order of magnitude of 150 metres. During curing, in order to avoid shrinkage cracks, the stress is partly produced in stages, for example, by stretching the stretching elements 11 each in order of succession by 25%, 50%, 75% and after total curing to about 100% of the prescribed elongation. For this purpose, by means of tighteners 16, each stretching element 11 is stretched to a predetermined elongation of the stretching element 11, after which each stretching element 11, subsequent to the formation of the main portion 9, is anchored definitely in groove anchors 13 and temporarily in intermediate anchors 8. The groove anchor 13 consists of a sleeve 22 fastened to a metal plate 21, in which an axially divided cone 23 is clamped. The intermediate anchor 8 also consists of a sleeve 24 and an axially divided cone 25 clamped therein. When the tighteners 16 are welded the cones 23 and 25 pressed into their anchor seats 26 and 27 retain the stretching element 11. Then the head rim 10 is cast to the main portion 9 in a casing consisting of the groove plate 47 and two longitudinal beams 23, whilst a screw rod 29 enveloped in a sleeve 51 and connected through a coupling 30 with the stretching element 11 is provided coaxially with each stretching element 11 in said casing. The coupling 30 consists of a screw sleeve 31 and a nut 32 screwed thereon with an anchor seat 33 and a divided cone 34 fitting therein. After the concrete 14 of the head rim 10 has hardened, the stretching element 11, one end of which is formed by the screw rod 29 is tightened to 100% of the prescribed stress. For this purpose the tightening means 35 are arranged in the narrow space of the dilatation groove 2, which may have a width a of 8 cms and a length c of the main portion 9 being, for example, 150 metres, whilst the length b of the head rim 10 may be 60 cms. These small-scale tightening means 35 comprise two hydraulic, linear motors 36 each comprising a cylinder 37,the axial length d of which is smaller than the width a of the dilatation groove 2. These motors 36, when energized, set off via the groove plate 47 from the concrete 14 of the concrete slab 3, each stretching element 11 of which is post-tightened. For energizing purposes the motors 36 communicate through control- means 38 and a manometer 40 with a pump 39. The tightening frame 41 of the tightening means 35 engages the screw rod 29 by means of a nut 42 screwed thereon. For tightening the screw rod 29 over the length b and the additional tightening of the stretching element 11 over the length c up to the required stress, only a slight elongation e of, for example, 1 cm is required. When the stretching element 11 with the screw rod 29 is brought to the predetermined stress, at which the cone 25 is lifted over a distance f from the anchor seat 27 of the intermediate anchor 8, an anchor nut 43 screwed onto the screw rod 29 is pressed by means of a ratchet wrench 44 to the anchor seat 45 of a flange-shaped groove anchor 46. Then the motors 36 can be de-energized and the tightening frame 41 having on the lower side a slot 48 for passing the screw rod 29 can be removed. If desired, a free end of the screw rod 29 is ground off. Since the temporary intermediate anchors 8 are then out of function the stress of all stretching elements 11 with the screw rods 29 uniformly extends from groove anchor 13 to groove anchor 46. Thus the concrete 14 of the main portion 9 and the head rim 10 is thus biassed in the same manner so that it has substantially anywhere the same strength.

[0010] The method shown in Figure 7 is distinguished from that of Figure 6 only in that in Figure 7 each stretching element 11 from groove anchor 13 to anchor 46 consists of an uninterrupted worm rod so that the coupling 30 is omitted, whilst the intermediate anchor 8 consists of a flange 49 with a nut 50.

[0011] Figure 3 shows a dilatation groove 2 bounded by groove plates 21 and 47 with lugs 65 supporting standing profiles 66, when they are welded to the groove plates 21 and 47 at the joints 67. To the profiles 66 is tightly vulcanized an elastic strip 68 extending transversely of the dilatation groove 2 in a compressed state.

[0012] Referring to Figure 8, the stretching elements 11 are formed by a cable extending from groove anchor 13 to groove anchor 53. The groove anchor 53 comprises a sleeve 24 with a guide sleeve 54 and an anchor seat 55 for an axially divided cone 56. The sleeve 24 is screwed onto a screw sleeve 52 welded to the groove plate 21.

[0013] For post-tightening the stretching element 11 two tighteners 35 are arranged in the dilatation groove 2, said tighteners comprising an axially divided clamping cone 58 urged into the clamping state by means of a hydraulic, linear motor 60 setting off from a tightening plate 59. For this purpose a lug 62 of the tightening plate 59 co-operates with a hook 61 of the motor 60, whose sleeve-like plunger 63 urges, upon energization, the clamping cone 58 into a conical seat 57 of the tightening plate 59. In the tightening plate 59 is arranged a hydraulic, linear motor 80 coaxially with the tightening element 11 and the motor 60. The plunger 81 of the motor 80 has an annular shape and bears on the groove plate 21 when the motor 80 is energized. Then the cone 25 is lifted from its anchor seat 27. After adequate tightening of the stretching element 11 throughout its length, the cone 56 forming a retaining member is pressed into its anchor seat 55 by means of two spacer sleeves 82 and a hydraulic, linear motor 69 bearing on the tightening plate 59 and arranged in the plunger 81 of the motor 80 in a coaxial position.

[0014] In the method illustrated in Figures 9, 10 and 11 each concrete slab 3 is formed as a whole and all, for example, 10 or 20 spaced, parallel stretching elements 11 are post-tightened from the narrow dilatation groove 2 by tightening means 70. Only groove anchors 71 are provided at the ends of the stretching elements 11 near the dilatation grooves 2. Opposite each stretching element 11 the adjacent end of the next concrete slab 3 has a coaxial recess 72. For this purpose the stretching elements 11 of successive concrete slabs 3 are relatively off-set over a small distance g. From the detail of Figures 10 and 11 it will be apparent that the groove anchor 71 is identical to the groove anchor 53. The tightening means 70 comprise a tightening plate 73, which clamps the stretching element 11 by means of a clamping sleeve 74 and a clamping cone 75 and which bears on a pressure plate 77 by means of two hydraulic, linear motors 76 during tightening of the stretching element 11, said plate 77, in turn, bearing on the groove plate 21 of the concrete slab 3 through two small hydraulic, linear motors 78 in which upon energization the fluid pressure exceeds that of the motors 76. When during a first step the stretching element 11 has been elongated over the stroke of the motors 76 and 78, the motors 78 are de-energized so that the pressure of the motors 76 urges via the - sleeves 82 the cone 56 lifted previously from its anchor seat 55 back into its anchor seat 55. Subsequently the motors 76 are de-energized and the tightening plate 59 is shifted in the direction of the arrow 79 a slight distance along the stretching element 11. After the cone 75 is pressed into its clamping sleeve 74, a next tightening step can be initiated so that each time the stretching element 11 penetrates over the length of the elongation further into the recess 72. After the stretching element 11 has reached the desired stress, the portion extending in the dilatation groove 2 is severed and the tightening means 70 can be removed for use on a further stretching element 11.

[0015] The tightening means 83 of Figure 12 comprise a split wedge 84 driven in between a tightening plate 73 and the spacer sleeves 82 for repelling the cone 56 back into its anchor seat 55. For the next tightening step the wedge 84 is withdrawn by means of handles 85 from between the tightening plate 73 and the sleeves 82.

[0016] In the method shown in Figure 14 each stretching element 11 is tightened by means of a conventional tightener 16, which bears through a curved tubing 86 and a pressing plate 87 with two hydraulic, linear motors 88 on the groove plate 21 of the relevant concrete slab 3, the stretching element 11 of which has to be tightened. The tubing 86 extends across a recess 89 in the next-following concrete slab 3. The pressing plate 87 with the motors 88 operates like the pressing plate 77. This tightening operation need not be carried out stepwise, whilst in addition the concrete slab 3 can be formed in a single run with the aid of a concrete mortar wiper (not shown), which is not hindered by tightening means projecting out of the concrete slab 3 and the adjacent dilatation groove 2. After all stretching elements 11 have been tightened to the desired stress, each stretching element 11 may, if desired, be fixed in its sleeve 15 by means of the surrounding concrete, which is injected into it through a recessed inlet channel 90.

Claims

1. A method of manufacturing a road surface, runway or a similar concrete path of at least one sequence of concrete slabs separated-from one another by a dilation groove, in which at least one of the concrete slabs is made by casting concrete mortar in situ on a foundation, whilst anchors of stretching elements extending in the direction of length of the concrete slab are fastened to the casing beams and subsequent to at least partial curing of the concrete the stretching elements are tightened characterized in that essentially all stretching elements of a concrete slab are post-tightened by bearing on concrete of the concrete slab concerned and anchored on groove anchors arranged near the dilatation groove.

2. A method as claimed in claim 1, characterized in that of at least one concrete slab first a main portion is made and subsequently at least one head rim completing said concrete slab and bounding the dilatation groove is cast to the main portion, whilst during the manufacture of the main portion the stretching elements are temporarily anchored by means of intermediate anchors disposed near the interface between the main portion and the head rim and in that after casting of the head rim essentially all stretching elements are post-tightened and anchored by means of the groove anchors with such a tension that the retaining members of the intermediate anchors are drawn off their anchor seats.

3. A method as claimed in claim 1 or 2 characterized in that during tightening of a stretching element the emerging end thereof is passed into a space recessed in the opposite concrete slab.

4. A method as claimed in claim 1, 2 or 3 characterised in that the stretching elements are tightened stepwise by each time a stroke which is smaller than the width of the dilatation groove.

5. A method as claimed in anyone of claims 1 to 4 characterized in that the stretching elements are permanently held free of adhesion to the surrounding concrete.

6. A method as claimed in anyone of claims 1 to 4 characterized in that after the stretching elements are tightened from the dilatation groove to the definite, predetermined stress, they are fastened to surrounding concrete.

7. A device for carrying out the method claimed in claim 1 comprising tightening means for tightening the stretching elements characterized in that the tightening means comprise at least one hydraulic, linear tightening motor, the axial length of which is smaller than the width of the dilatation groove.

8. A device as claimed in claim 7 characterized in that the tightening means comprise a tightening plate which bears via at least one hydraulic, linear tightening motor on the head side of the concrete.slab and which is provided with energizing means for pressing the retaining member to its anchor seat.

9. A device as claimed in claim 7 or 8 characterized in that the retaining member is formed by a nut to be screwed onto a tapped end of a stretching element.

1Q. A device as claimed in claim 7 or 8 characterized in that the retaining member is formed by a clamping cone which is urged into the clamping position by means of at least one hydraulic, linear motor bearing on the tightening plate.

11. A device as claimed in claim 10 characterized in that in order to move the retaining member into its clamping position the linear motor is arranged in a coaxial recess of the tightening motor.

12. A device as claimed in anyone of claims 7 to 11 characterized in that the tightening plate is provided with a member engaging a stretching element and being coaxially arranged inside the tightening motor.

13. A concrete path manufactured by the method claimed in anyone of claims 1 to 6.

Drawing