RAILWAY SYSTEM AND ITS SUPPORTING STRUCTURE, AS WELL AS THEIR METHOD OF CONSTRUCTION

Abstract: A bearing structure (100) for a rail track is described, which bearing structure comprises a profiled concrete slab (101), with two rail accommodation areas (104) which are open at their outward directed side edges. Steel plates (110) are screwed against side walls (102) of the concrete slab, preferably by means of tension bars (111) which extend over the full width of the concrete slab. A rail (120) is placed in the groove shut off by the metal plates. The rails are easy to repair and/or replace, because they are easily accessible by removing the said metal plates. The metal plates can also serve as a fixing point for fixing thereto a guide structure (500) for a magnetic train.

Description: RAILWAY SYSTEM AND ITS SUPPORTING STRUCTURE, AS WELL AS THEIR METHOD OF CONSTRUCΗON The present invention relates in general to a new design for a rail track system, and to a method for its manufacture . In general, a track for guiding rail vehicles is 5 composed of two elongated track bars disposed parallel to each other, and also a bearing structure for bearing the bars. The bearing structure serves to support the bars, also indicated as rails, and to ensure a correct mutual distance between the rails. To this end, the rails are 10 fixed on the bearing structure, so that the combination of the bearing structure and the rails can be regarded as a unit . Conventionally, the bearing structure is formed by a multiplicity of transverse members, also known as 15 sleepers, which can be described as elongated supporting blocks, the lengthwise direction of which runs perpendicular to the lengthwise direction of the rails, and which are fitted beneath the rails with a predetermined distance between them. Likewise conventionally, the track 20 structure comprises a gravel bed on which the sleepers are laid. The positioning of track rails has to meet high standards of accuracy. Conventionally, few standards are set for the positioning of the sleepers, and the desired 25 accuracy of the positioning of the track rails is achieved by adjusting the track rails at their destination position (in situ), after which they are fixed to the sleepers. Such conventional rail track systems have a number of major disadvantages. First, it is a disadvantage that 30 the rails are not supported over their entire length. For a result of this is that when a rail vehicle (a train) passes, the track rails sag at the positions between the supporting points, as a result of which they are subjected to a fatigue stress. Moreover, as a result, vibrations are 35 caused in the passing train, fatigue and wear occur in parts of the train, and noise is produced. Another disadvantage is that the position of the rails is not completely static with the passage of time. After some time, the bearing structure with the rails fixed thereon sinks slightly into the gravel bed beneath it, and this sinking process is not necessarily constant along the length of the track rails. This means that regular maintenance has to be carried out on the railway structure, in the sense that the bearing structure has to be restored to the correct height relative to the track structure. Various variants have already been devised for the conventional rail track system described above, in which variants the idea of a large number of individual sleepers was abandoned. An example of such a bearing structure is described by the term "embedded rail". In this case the bearing structure consists substantially of an elongated concrete slab in which two parallel grooves have been made. The track rails are mounted in these grooves. However, this known embedded rail system still has a number of shortcomings. First, a rail still has to be positioned in situ, in other words its position must be adjusted relative to the grooves in the concrete slab. The rails are then cast in the grooves. However, this means that it is extremely awkward and expensive to repair a rail if necessary. Besides, it is still the case that combining the bearing structure with the rails from a structural point of view constitutes a load for the track structure. If the track structure comprises a gravel bed, the bearing structure of the embedded rail system can still sink into said gravel bed. In order to eliminate this problem, track structures formed by a concrete casing were designed. However, here again the concrete casing of the track structure is first fitted at the application location, after which the bearing structure is placed in the casing, and the track rails are then embedded in the bearing structure. Here again, the exact position of the track rails must be adjusted at the position of the application location, while the disadvantage that the bearing structure constitutes a load for the track structure remains the same as before . The disadvantages discussed above become all the more important with the increasingly high speed of trains travelling along the track. In particular, extremely high standards as regards accuracy and positional stability are set for the development of high-speed trains, which have to travel at a speed of the order of 300 km/hour and more along the track. It is therefore an important object of the present invention to overcome the disadvantages described above. More particularly, the object of the present invention is to provide a rail track system which is suitable for use by a high-speed train, and in which the required accuracy of the positioning of the track rails can be achieved without all that much difficulty. A more recent development for public transport is the so-called magnetic train. This is a train which advances in a contact-free manner along a guide structure, supported by a magnetic field and propelled by means of a linear motor forming part of said guide structure. Such a guide structure has to meet extremely high standards of accuracy. It is therefore a further object of the present invention to provide an accurate and positionally stable bearing structure which is suitable for fixing the guide structure of a magnetic train. Until now, a separate rail track system was developed for magnetic trains, totally independently of the rail track systems designed for rail vehicles. This means that the costs of laying a magnetic rail track are extremely high. These costs could be reduced considerably if rail vehicles and magnetic vehicles, more particularly a high-speed train and a magnetic train, could make use of the same rail track system. A problem which plays a role here is that the speed of a magnetic train is much higher than the speed of a high-speed train, and that in bends the skew of the magnetic track must therefore be different from the skew of the rail track. In this case the term "skew" is understood as meaning the transverse gradient of the track, measured in the direction perpendicular to the lengthwise direction thereof, provided to give a counterforce for the centrifugal force or normal acceleration. The present invention also aims to provide a solution to this problem. According to an important aspect of the present invention, the bearing structure for a rail track comprises a substantially slab-shaped, preferably concrete core, which at its top side is provided with two parallel groove- shaped rail accommodation areas, each rail accommodation area having a bottom and a first side wall which are defined by the material of the core, and also a second side wall which is defined by an element to be fixed detachably to the concrete core. In a first embodiment, with respect to the rail accommodation area, the first side wall is situated on the side of the centre of the core, and the element which is detachably fixed to the concrete core is situated on the outside of the bearing structure. These elements can be formed by steel plates fixed against the side walls of the core, preferably by means of tension bars extending over the full width of the core. A rail is fitted in the groove shut off by the metal plates. The rails are simple to repair and/or replace, because they are easily accessible by removing the abovementioned metal plates. The metal plates can also serve as a fixing point for fixing a guide structure for a magnetic train thereto. As is known, the wheels of rail vehicles have a flange which is situated on the inside of the track rails, in other words the side of the rails which faces the centre of the bearing structure. In this way, a wheel exerts an outwardly directed transverse force on a rail, which is particularly significant in bend sections. Said transverse force must be absorbed by the outer side faces of the rail accommodation areas . In the case of the abovementioned first embodiment the transverse force occurring must then be absorbed by said element detachably fixed to the concrete core. Another object of the present invention is to design a bearing structure in such a way that transverse forces are absorbed primarily by the construction material of the bearing structure itself (concrete) . To this end, a bearing structure of the type described above according to the present invention in a second embodiment is characterized in that the element detachably fixed to the core is always situated on the inside of the rail accommodation area in question. According to another important aspect of the present invention, the abovementioned bearing structure is fixed to a trough-shaped track structure, likewise of concrete, with a substantially U-shaped cross section, in such a way that the combination of concrete bearing structure and concrete track structure forms an integral bearing unit . The abovementioned and other aspects, features and advantages of the present invention will be illustrated further by the discussion which follows of exemplary embodiments of the rail track system according to the present invention with reference to the drawing, in which: figure 1 shows diagrammatically a cross section of an embodiment of a rail track system according to the present invention; figures 2A-2F illustrate diagrammatically various application heights for the rail track system of Figure 1 ; figures 3A-3C illustrate diagrammatically the manufacture of a slab-shaped bearing structure and a trough-shaped track structure according to the present invention; figure 4A shows more details of a mould for manuf cturing a concrete core of a slab-shaped bearing structure according to the present invention; figure 4B shows a diagrammatic cross section of an embodiment of a concrete core of a slab-shaped bearing structure according to the present invention; figure 5 shows on a larger scale a diagrammatic cross section of half of an embodiment of a concrete core of a slab-shaped bearing structure according to the present invention, provided with a guide structure designed for magnetic trains; figure 6 shows diagrammatically a cross section of a twin- track railway, designed according to the ideas of the present invention; figure 7 shows diagrammatically a top view of a section of a slab-shaped bearing structure with a guide structure designed for magnetic trains; figures 8A and 8B show diagrammatically variants of embodiments of a slab-shaped bearing structure; and figure 9 shows diagrammatically a cross section of a second embodiment of a rail track system according to the present invention. Figure 1 shows diagrammatically a cross section of an embodiment of a rail track system 1 according to the present invention, on which both a high-speed train 2 (on the left in Figure 1) can travel on wheels and a magnetic train 3 (on the right in Figure 1) can travel in a suspended manner. The rail track system 1 comprises a trough-shaped track structure 200 with a substantially U- shaped cross section and a substantially slab-shaped bearing structure 100, which are fixed to each other to form a bearing unit . The trough-shaped track structure 200 has a bottom 201 and two side walls 202. Spacers 203 are formed on the bottom 201, preferably as an integral unit with the bottom 201. The slab-shaped bearing structure 100 is fixed on said spacers 203, in order to ensure a mutual distance between the slab-shaped bearing structure 100 and the bottom 201 of the trough-shaped track structure 200. Although it is possible in principle to make the trough-shaped track structure 200 and the slab-shaped bearing structure 100 of, for example, structural steel, it is an important aspect of the present invention that the trough-shaped track structure 200 and the slab-shaped bearing structure 100 are advantageously made of concrete. The bearing structure 100, which on account of its slab-shaped exterior is also described by the term "track slab" , is substantially symmetrical relative to a centre plane M (see figure 9) . In the description which follows, a direction facing said centre plane M will be indicated by the term "inwards", while a direction facing away from said centre plane M will be indicated by the term "outwards" . The trough-shaped track structure 200 is well anchored in the substrate 4. In Figure 1 the trough-shaped track structure 200 is raised above the substrate 4 by means of supporting pillars or columns 5, which columns 5 will generally rest on piles driven into the ground 4 and/or on a piled foundation 6. In this case the length of the columns 5 can be selected suitably for positioning the trough-shaped track structure 200 at a desired height relative to ground level, as illustrated in figures 2A to 2F. For instance, the trough-shaped track structure 200 can be of such a height relative to ground level, for example 5 metres or more, that other traffic can pass unimpeded underneath it, as illustrated in figures 2A and 2B . The height relative to ground level can also be less, for example approximately 1 metre as illustrated in figures 2C and 2D. However, according to the present invention, the trough-shaped track structure 200 can also be positioned in a recessed manner in the ground, as illustrated in figures 2E and 2F. As illustrated, inter alia, in figure 2B, the rail track system 1 is composed of prefabricated segments 1' of relatively great length, for example of the order of 30 metres. These segments 1', which are fully self-supporting, are supported at their ends by the abovementioned pillars 5, and are positioned in line with each other at the application location (in situ) . Figures 3A-C illustrate the manufacture of a segment 1' of the rail track system 1 according to the present invention. Segments 200' of the trough-shaped track structure 200 are manufactured separately, as illustrated in figure 3A. A segment 200' of the trough-shaped track structure 200 is manufactured in its entirety by pouring concrete into a mould or formwork 300, it being preferable for the track segment 200' to be manufactured "upside down", as illustrated. The formwork 300 comprises an inner formwork part 301, which is disposed in a fixed position on a suitable base 302, which inner formwork part 301 has an outer contour which defines the inner contour of the trough-shaped track segment 200', including the spacers 203 and the top edge 204 thereof. The formwork 300 also comprises first outer formwork 303 and second outer formwork 304, which are disposed parallel to the inner formwork 301, and which can travel on wheels (or are movable in another way) on the base 302 in a direction substantially perpendicular to their lengthwise direction. When they are pressed against the inner formwork 301, the two outer formwork parts 303 and 304 together form an outer formwork having an inner contour which defines the outer contour of the bottom 201 and the side walls 202 of the trough-shaped track segment 200' . Concrete is poured into this formwork 300. After the concrete has hardened sufficiently, which will generally be the case after approximately 1 day, the formwork parts 303 and 304 are driven out to the position illustrated in figure 3A, and the manufactured track segment 200' can be lifted out of the inner formwork 301. The manufactured track segment 200' is then left for a predetermined time, for example a month or longer, resting on a rest field, in order to allow all shrinkage and creep phenomena to settle down. It is pointed out here that the track segments 200' are prestressed in their lengthwise direction, which can give rise to creep phenomena . Figures 3B and 3C illustrate the manufacture of a segment 100' of the track slab 100. This slab segment 100' is also manufactured "upside down" from concrete, on a lower mould 310 which defines the upper contour of the slab segment 100', as will be explained in greater detail later. For the sake of simplicity, an upper mould which defines the lower contour of the slab segment 100' is not shown in figures 3B and 3C. As mentioned earlier, the slab segment 100' and the trough-shaped track segment 200' form an integral bearing unit. Figures 3B and 3C illustrate two variants for the manufacture of said integral unit. Figure 3B illustrates how a slab segment 200' is placed "upside down" on the concrete of the slab segment 100' shortly after the latter has been poured into the mould 310, i.e. when this concrete is still soft, in order to form an integral unit in this way. After sufficient hardening, the combined segment 1' of the rail track system 1 is lifted out of the lower formwork 310 and rotated 180° about its longitudinal axis. In the case of this method of manufacture, the track segments 200' will be manufactured earlier than the slab segments 100', because a hardened track segment 200' has to be positioned on top of the soft concrete which has just been poured for the slab segment 100', in which case the spacers 203 of said track segment 200' penetrate into the soft concrete of the slab segment 100' . However, it is also possible for the segments 100' and 200' to be manufactured completely separately from each other, as illustrated in figure 3C, so that they harden completely separately from each other. In that case they can therefore also be manufactured simultaneously. The segments 100' and 200' are then fixed to each other when they are fully hardened, the track segment 200' first being rotated through 180° about its longitudinal axis and placed on its bottom 201, while the slab segment 100' is likewise rotated through 180° and placed on the spacers 203 of the track segment 200 ' . It is a great advantage that the combination of the track slab 100 and the trough-shaped track structure 200 is formed as an integral bearing unit, because this means that the track slab 100 contributes to the strength and rigidity of the rail track system 1 as a whole, instead of the track slab constituting a load for the track structure, in which case the full strength and rigidity of the rail track system 1 would in fact have to be provided by the trough- shaped track structure, which would then have to be of a much heavier design. On the other hand, it is advantageous that the primary parts of the rail track system 1, in other words the slab segments 100' and the trough-shaped track segments 200', are manufactured independently of each other. This makes it, in a relatively simple way, possible to manufacture some parts, namely the slab segments 100', with extremely great accuracy, while less requirements are set for the accuracy of other parts, namely the trough- shaped track segments 200' . This emerges in particular during the manufacture of segments 1' of the rail track system 1 which form part of a bend in the rail track. In a bend, the rails have a particularly complex shape. First, they are bent horizontally, wherein the radius of curvature is not constant over the length of the rails (clothoid shapes of bend) . Secondly, the track surface defined by the rails is slightly skew relative to the horizontal, the angle of gradient not being constant over the length of the rails. This means that the track slab 100 has an extremely complex shape, which has to be manufactured with great accuracy. On the other hand, a segment 200' of the trough- shaped track structure 200 may have a bend with a continuous radius of curvature, and may even be entirely straight over its full length, because there will be ample play between the outside of passing trains 2, 3 and the inside wall of the trough-shaped track structure 200 to allow for a curved section of the rails in a straight segment of the trough-shaped track structure, as illustrated in figure 1. The fact that the trough-shaped track segments 200' may all be straight means that the same formwork elements 301, 303 and 304 can always be used (in which case end faces of the formwork will at the most be placed slightly slanting) , which is a considerable saving on the production costs. As mentioned, the accuracy and positional stability of the positioning of the rails, both in the case of the straight track segments and in the case of the curved track segments, where the rails are an extremely complex shape, have to meet extremely high standards. Until now it was necessary to achieve that accuracy at the application location, and the rails were adjusted to the desired position at the application location. This means that until now the work at the application location has been relatively complex: the position of the rails has to be measured, and compared with the desired position, deviations have to be eliminated by shifting the position of the rail to the desired position, and the rail then has to be fixed, the rail having to be supported by means of infiller members and supporting members. According to an important aspect of the present invention, these disadvantages are eliminated by manufacturing the slab segments 100' with great accuracy, the grooves for the rails already being the desired shape, and the shape of the grooves being manufactured so accurately that the rails can simply be fixed in said grooves. The manufacture of a slab segment 100' according to the present invention with great accuracy will now be explained with reference to figures 4A-B. Figure 4B shows diagrammatically a cross section of a first exemplary embodiment of the concrete core 101 of a slab-shaped bearing segment 100' . Said concrete core has two substantially flat, substantially vertically directed side walls 102, and a profiled upper surface 103. The profiled upper surface 103 is slightly concave, for guiding rainwater and the like to discharge channels not shown for the sake of simplicity. The core 101 has on its top side two parallel rail accommodation areas 104, each of which is defined by a substantially horizontal bottom or rail bearing surface 106 and, at the side of said bottom which faces the centre of the core 101, a substantially vertical side wall or rail supporting surface 105. The rail bearing surface 106 adjoins the side wall 102. The two rail supporting surfaces 105 adjoin the profiled top face 103. On its underside, the concrete core 101 has two ridges 107, which are designed for fixing the above- mentioned spacers 203 of the track segments 200'. The precise contour of the underside of the concrete core 101, including these ridges 107, is not critical, and will not be discussed any further. A mould for said core 101 is indicated in general by the reference numeral 400. Since the mould 400 is in principle symmetrical, corresponding parts are indicated by identical reference numerals. The mould 400 comprises two groove mould parts 410 with a substantially L-shaped cross section. Each groove mould part 410 has a substantially horizontally directed first groove mould face 411 and a substantially vertically directed second groove mould face 412. The two groove mould parts 410 are disposed symmetrically relative to each other, the vertically directed second groove mould faces 412 facing each other, and the horizontal first groove mould faces 411 facing away from each other. The groove mould parts 410 of the mould 400 define the shape of the rail accommodation areas 104. More particularly, the first groove mould face 411 defines the horizontal rail bearing surface 106, and the second groove mould face 412 defines the vertical rail supporting surface 105 of the rail accommodation area 104. The shape of these surfaces 105 and 106 must be manufactured extremely accurately, in order to make them suitable for use as guide faces for the fitting of rails. More particularly, these faces have to be capable of being curved to a predetermined shape. This predetermined shape of the rail supporting surface 105 and the rail bearing surface 106 is achieved according to an important aspect of the present invention by the fact that the groove mould parts 410 are not rigid, but are bendable both in the vertical direction and in the horizontal direction. In figure 4A is shown that the mould 400 is provided with adjustable positioning devices 421 for accurately adjusting the vertical position of a groove mould part 410 relative to a fixed supporting surface 420, as illustrated on the right in figure 4A, while the mould 400 is also provided with adjustable positioning devices 422 for accurately adjusting the horizontal position of a groove mould part 410 relative to a fixed reference, as illustrated in the left half of figure 4A. Although only one vertical positioning device 421 and only one horizontal positioning device 422 are shown in figure 4A, the groove mould parts 410 are provided with several of these positioning devices 421 and 422 along their entire length; in a suitable embodiment these positioning devices are spaced approximately 3 m apart . All these positioning devices 421 and 422 are individually adjustable, independently of each other, which makes it possible to bend the bendable groove mould parts 410 to an accurately defined shape which is curved in two directions. The drive of the positioning devices 421 and 422 can be manual, but it is preferably controlled by a computer or microprocessor, which calculates the necessary settings of the individual positioning devices on the basis of the desired shape of the track. Between the groove mould parts 410, the mould 400 contains a large number of elongated mould bottom parts 413, for example nine, disposed next to each other and abutting each other. The mould bottom parts 413 define the top face 103 to be formed of the concrete core 101. Although the exact shape of said top face 103 is not critical, it is still important for said top face 103 to be accurately finished, because said top face 103 is continually exposed to weather influences. Each mould bottom part 413 is bendable both in the vertical direction and in the horizontal direction, and is provided with a large number of positioning devices 423 along its length, for example one for every three metres of length of a mould bottom part, which positioning devices can likewise be controlled by the abovementioned computer, not shown, in order to form the top face 103 in accordance with a course which corresponds to the course of the rail accommodation areas 104 to be formed. The mould 400 further comprises two substantially vertically directed side mould parts 414, which define the side walls 102 of the concrete core 101. Said side mould parts 414 are likewise bendable, and along their length are provided with a large number of positioning devices 424 (for example one for every three metres of length) , as shown on the left side of figure 4A, which positioning devices can likewise be driven by the computer (not shown) . These positioning devices 424 are controlled in such a way that the side mould parts 414 always abut the groove mould parts 410, in order to define curved side walls 102 for the core 101, which side walls have a curved course which corresponds to the curved course of the rail accommodation areas 104. Figure 4B illustrates a substantially horizontal hole 108, extending across the full width of the core 101 between the two side walls 102. More particularly, the core 101 has along its length a large number of these transverse holes 108. The transverse holes 108 can be drilled after the core 101 has hardened, but it is preferable for the transverse holes 108 to be hollowed out during the manufacture of the core 101, to which end the mould 400 is provided with bars 415 extending between the side mould parts 414. As mentioned, the underside of the core 101 is not critical as regards shape. For that reason, an upper mould for defining the shape of the underside of the core 101 is not shown in figure 4A. It will suffice here to point out that the upper mould is also bendable so that it abuts the side mould parts 414, and can be positioned by means of positioning devices, in order to make the shape of the underside of the core 101 conform to the course of said core 101 which is curved in two directions. The positioning devices 421, 422, 423, 424 can be any desired suitable positioning devices which are known per se, for example hydraulically operating positioning devices. After the concrete of the core 101 has hardened sufficiently, the core 101 is removed from the mould 400, and the core 101 is allowed to rest for a sufficiently long time, for example a month or longer, in order to give creep or shrinkage phenomena the opportunity to settle down. The deforming effect of these phenomena on the exact shape of the core 101 can be calculated beforehand, and account is taken of this effect when the shape of the mould 400 is being determined. However, it is possible, if desired, to correct the deformations occurring during the rest period, by loading the core 101 with a prestress, the magnitude of which can be varied. In the left half of figure 4B is shown that the slab-shaped bearing segments 100' are provided with metal side plates 110, which define outer side walls 109 of the rail accommodation areas 104, and which are fixed against the side walls 102 of the core 101 by means of tension bars 111 and bolts 112. The tension bars 111 are situated in the abovementioned transverse holes 108. The metal side plates 110 extend along the full length of the side walls 102. In order to prevent problems as a result of temperature variations, the side plates 110 are preferably of a length of no more than approximately 3 m, and the bearing segment 100' is therefore provided with several side plates 110 placed against each other. The side plates 110 fulfil various functions. They exert a prestressing force, the magnitude of which is adjustable, in the transverse direction on the core 101. The side plates 110 can be fitted after the core 101 has hardened completely and after it has gone through the abovementioned rest period, but the side plates 110 can also be fitted earlier, in which case they serve to exert the correcting prestressing mentioned above. The fact that the tension bars 111 lie in a loose position in through transverse holes 108, in other words that they are "detached bars", has a number of advantages. On the one hand, this means that any repair of a tension bar which may be necessary is easy to carry out . On the other hand, the full strength of the tensile stress is available over the full width of the core 101. Figure 5 shows a diagrammatic cross section of half of a core 101, comparable to figure 4B, on a larger scale, in order to illustrate the fitting of a rail 120 in a rail accommodation area 104. In figure 5 is illustrated that a rail accommodation area 104 has a substantially U-shaped cross section, which at its underside is bounded by the rail bearing surface 106 of the core 101, towards the inside of the core 101 is bounded by the rail supporting surface 105, and towards the outside of the core 101 is bounded by the side plate 110 fitted against the side wall 102 of the core 101. It is also shown in figure 5 that a rail 120 rests with its underside on the rail bearing surface 106 and with a side edge rests against the rail supporting surface 105, while said rail 120 is fixed in the rail accommodation area 104 by means of a casting compound 121, for example of plastic. Preferably, and as illustrated, a damping layer is situated between the under- side of the rail 120 and the rail bearing surface 106, in order to exert a damping effect; the same applies between the side edge of the rail 120 and the rail supporting surface 105. Said damping layer can be formed by the casting compound 121, or by damping sheets of, for example, rubber or plastic. As mentioned, an embedded rail system is known per se, wherein a groove is hollowed out in a concrete member, in which groove a rail is fixed. However, a major disadvantage of such systems is that the rail is difficult or impossible to reach for repair and/or replacement. This disadvantage is absent in the case of the system proposed by the present invention: should it be necessary, for example, to replace the rail, it is relatively simple to remove the side plates 110, after which the casting compound 121 can be approached from the side in order to detach the rail 120. A replacement segment to be fitted instead of the original rail 120 can be placed in a simple manner on the rail bearing surface 106 and pressed with its side edge against the rail supporting surface 105, after which the replacement rail is sure to have the desired shape. After placement of the side plates 110 and restoration of the prestress in the tension bars 111, the new rail is fixed again with casting compound. Instead of a casting compound 121, the rail 120 can also be clamped against the rail supporting surface 105 by means of rubber or plastic clamping blocks 121, which are pressed down by the side plates 110. In that case the removal of the rails 120 is even simpler, because when the side plates 110 are removed such clamping blocks 121 can easily be removed, after which the rails 120 can easily be removed, too. It has been explained above that the three- dimensional curvature of the rail accommodation areas 104 can be manufactured very accurately in the factory, for defining an accurate three-dimensional shape of the rails 120. For one specific section of line, in other words one specific bearing structure for two rails, the three- dimensional shape of the left rail can be adjusted in the optimum manner irrespective of the three-dimensional shape of the right rail, so that in this way the rail of an outside bend can be given a greater radius than the rail of an inside bend. If a specific railway section comprises several rail tracks next to each other, the present invention also offers a number of advantages. First, the individual rails of the different rail tracks can, of course, be formed individually. Secondly, it is an advantage that the rail track system 1 according to the present invention is a single-track railway system. For the manufacture of a multi-track railway, several of these single-track railway systems are then positioned next to each other. Figure 6 illustrates this for a railway with two tracks next to each other. Figure 6 shows diagrammati- cally a cross section through a bend section of such a twin-track railway. It is shown clearly in this figure that the combination of bearing structure and track structure is positioned askew relative to the horizontal, the degree of skew being dependent upon the radius of the bend and of the anticipated speed of the passing vehicles. The transverse gradients of the various rail track systems can be selected independently of each other, so that, for example, a rail track system with a larger radius can have a smaller gradient. On the other hand, a rail track system which is designed for faster trains can have a greater transverse gradient . Even if the several rail track systems of a multi- track railway had the same transverse gradient, the system of the present invention gives the advantage that the two track structures can be positioned at a specific height independently of each other. If the two track structures were immovably connected to each other and situated in one plane, in the case of a bend section where the track has to have a transverse gradient, and where the track in its entirety has to have a minimum height relative to ground level in order to guarantee unimpeded passing of other traffic beneath it, this would mean that the track structure of the outermost track parts would have to be in an unnecessarily high position. In the case of the system according to the present invention, on the other hand, the two track structures can be placed independently of each other at the same height, as shown clearly in figure 6. Another important advantage offered by the present invention is that it is possible in a relatively simple and aesthetically acceptable manner to fit a platform structure 7 between two track structures 200 of two rail track systems 1 disposed next to each other. Such a platform structure has various functions. It acts as a footway for maintenance personnel, but also in case of emergency as an escape route for passengers. Furthermore, various cable ducts can be placed here, for fixing various cables. As also illustrated in figure 6, the top edges 204 of the trough-shaped track structure 200 are preferably designed in such a way that they can serve as a mounting platform for, for example, posts of overhead lines, signposts, guard rails and the like. All the advantages mentioned above according to the present invention are already offered if the rail track system 1 proposed by the present invention is used solely for rolling trains such as a high-speed train 2. According to an important aspect of the present invention, the rail track system can, however, also be used for magnetic trains 3 by mounting a guide structure 500 designed for magnetic trains on the bearing structure 100, as will be explained in greater detail below. Of course, it will be possible to lay different tracks next to each other, one track being used solely by magnetic trains and the other track being used solely by rolling trains, which are normal or high- speed trains, as illustrated in the left half of figure 6. However, as will become clear from the discussion which follows, the present invention offers the important advantage that one and the same track can be used both for magnetic trains 3 and by rolling trains 2, as illustrated in the right half of figure 6 and in figure 1. Another important advantage here is that it is not necessary to fit both the rail structure for rolling trains and the magnetic guide structure for magnetic trains from the outset. In a first phase the rail track can be laid exclusively for rolling trains, as shown on the left in figure 6. In a subsequent phase it is an extremely simple and relatively low-cost operation to make a section suitable for the passage of magnetic trains, simply by then fitting magnetic guide structures, as shown in the right half of figure 6. Of course, the reverse is also possible. Figure 5 shows the details of a possible magnetic guide structure 500 for a magnetic train. This embodiment of a magnetic guide structure 500 comprises a tubular structure with a top plate 501, a bottom plate 502, an outer side plate 503 and an inner side plate 504. By means of a connecting piece 510, the abovementioned tubular structure is fixed to the abovementioned side plates 110 of the bearing structure 100. The connecting piece 510 is provided at its ends with fixing flanges 511 and 512. One fixing flange 511 is fixed to the inner tubular plate 504, for example by means of bolts and nuts. The other fixing flange 512 is fixed against a side plate 110. It is preferable to use the earlier mentioned tension bars 111, as illustrated, to which end the abovementioned fixing flange 512 is provided with holes which correspond to the positions of said tension bars. If the tubular structure 500 is fitted on the side plates 110 at a later stage, the abovementioned nuts 112 are removed first, the flanges 512 are placed over the ends of the tension bars 111, and the nuts 112 are tightened again. It will be clear that all these are very simple actions. The bottom plates 502 are used for mounting the stator packets thereon, which stator packets serve to supply the bearing power for the magnetic trains, and also to supply the propulsion force for said magnetic trains (linear motor) , which is indicated diagrammatically by the reference numeral 505 in figure 5. The outer plates 503 of the tubular structure 500 serve to guide the magnetic trains in the horizontal direction. The top plates 501 of the tubular structure are glide plates, which only fulfil a role if the power supply to the magnetic trains is unexpectedly cut, with the result that the magnetic bearing power for said trains is removed: in such a case a magnetic train will "land" on said top plates 501 and come to a standstill gliding on them. As stated, in bends the track surface of a track should be positioned askew relative to the horizontal in the transverse direction, as illustrated in figure 6. The degree of skew, or the angle of gradient relative to the horizontal, is dependent upon the radius of the bend and on the anticipated speed of the passing trains. Since in practice magnetic trains will travel at a higher speed than rolling trains, it is desirable for the skew of the magnetic track to be greater than the skew of the rail track. According to the present invention, this is very easily possible, even if magnetic train and rolling train are making use of the same section of line. The skew of the rail track is determined by the positioning of the rails 120, and thus by the extent to which the rail bearing surfaces 106 of the rail accommodation areas 104 are positioned askew relative to the horizontal. The degree of skew of the magnetic track, on the other hand, is defined by the mutual position and orientation of the two magnetic guide tubes 500 relative to the horizontal. As mentioned, said magnetic guide tubes 500 are fixed by means of connecting supports 510 to the side plates 110 of the slab- shaped bearing structure 100. The exact positioning and orientation of each tube 500 can be adjusted by a suitably chosen dimensioning of said connecting supports 510, as will be clear to a person skilled in the art, in order to give the magnetic track a suitable desired skew, independent of the skew of the rail track. All magnetic guide tubes 500, apart from the connecting supports 510, can be identical to each other in this case. The magnetic guide tubes 500 can theoretically be continuous, or at any rate the same length as the slab- shaped bearing segments 100' . However this is not the preferable option, in view of temperature variations occurring and length variations caused by them. The magnetic guide tubes 500 are preferably formed as a section with a length of the order of several metres. For practical reasons, it is preferable for the length of said tubular segments to be a full multiple of the length of the stator packets of the linear motor to be fixed thereon for the propulsion of the magnetic train. In a currently known standard design where the length of said stator packets is approximately 1030 mm, a suitable length for said tubular segments is approximately 3090 mm. Figure 7 shows diagrammatically a top view of a part of a slab-shaped bearing segment 100', which along its side edge is provided with tubular segments 500. In the figure is shown that adjacent tubes do not have to rest against each other, but that a slight gap a few millimetres wide may be left between them, in order to be able to accommodate length variations of the tubular segments. In figure 7 is also shown that each tubular segment is fixed to the side plate 110 of this bearing section 100' by means of three connecting supports 510 1 , 510 2 and 510 3 . The first connecting support 510 ! is situated halfway along the length of the tubular segment 500, and is designed to ensure absolute fixing of the centre of the tubular segment to the side plate 110. The second connecting support 510 2 is situated near one end of the tubular segment and is designed to provide fixing of said end of the tubular segment in the horizontal and vertical directions perpendicular to the lengthwise direction of the tubular segment, but to be able to give slightly in the lengthwise direction of the tubular segment when there are length variations of the tubular segment. The same applies to the connecting support 510 3 disposed near the other end of the tubular segment . Figures 8A and 8B show variants of slab-shaped bearing structures according to the present invention. In these figures, parts which are identical to or comparable with parts of the slab-shaped bearing structure 100 discussed with reference to figures 4B and 5 are indicated by the same reference numerals, although in figures 8A and 8B the reference numerals begin with 800 and 900 respectively. The slab-shaped bearing structure 900 will now be discussed first with reference to figure 8B . The concrete core 903 thereof has a profiled top face 903, a substantially flat bottom face 907, and side walls 902. Unlike the embodiment 100 discussed earlier, the side walls 902 of the concrete core 903 are not directed substantially vertically, but form an angle with the vertical, which angle is preferably in the region of approximately 15°. The concrete core 903 also has rail accommodation areas 904 which can be curved in three-dimensional fashion, in a manner explained in detail with reference to the embodiment 100 of figures 4B and 5. Each rail accommodation area 904 has a U-shaped cross section which is bounded by a rail supporting surface 905, a rail bearing surface 906, and a side plate 910 which is fitted against the slanting side wall 902. A rail 920 is fitted in the rail accommodation area 904 by means of a casting compound 921. The side plates 910 fitted on either side of the concrete core 903 are fixed to said core 903 by means of tension bars 911 and 911 2 , which extend in a direction substantially perpendicular to the surface of the side plates 910. In this case the tension bars cannot be in the form of continuous tension bars extending over the full width of the core 903 between the side plates 902, but are in the form of "blind" tension bars which extend to less than half the width of the core 903 between the side walls 902. At their outside end, they act by means of a nut 912 upon a side plate 910, and at their inside end they are fixed to the core 903 by means of a plug or dowel or the like. As a variant, it would be possible for the tension bars 911 x and 911 2 to project with their inside ends from the concrete core 903, through the bottom wall 907 thereof, in which case nuts which can act upon the concrete of the core 903 can also be screwed onto the inside ends of the tension bars . The side plates 910 and the tension bars 911 x and 911 2 thus cause a suitable prestress in areas of the concrete core 903 situated near the rail accommodation areas 904. Because of the slanting position of the tension bars 911 x and 911 2 , the inside ends thereof are situated at a lower level of the core 903 than the outside ends thereof. In order also to achieve a suitable prestress at this lower level, in other words, in the horizontal plane where the inside ends of the tension bars 911 x and 911 2 are situated, traditional tension wires 913 are cast into the concrete core 903. Instead of such traditional tension wires, it would also be possible here to use detached tension bars which are provided with screw thread at least on their ends, in which case tension nuts then act upon tension blocks 914. In the case of the embodiment shown in figure 8B the side wall 902 is slanted over its full height; in that case any tension blocks 914 present have a wedge-shaped cross section, as shown. However, the side wall 902 can also have a bent or curved contour, in which case a top part of the side wall slants as shown, and a bottom part of the side wall is substantially vertical, in which case any tension blocks 914 present can simply have a rectangular cross section. If desired, a guide structure designed for magnetic trains can be fixed on the side plates 910, comparable to the guide structure 500 described earlier. Although the slab-shaped bearing structure 900 of figure 8B can also be combined with the trough-shaped track structure 200 described, it is intended for placing on a traditional substrate. The structure 900 then already provides the advantages described above over conventional bearing structures with sleepers, and over the above- mentioned embedded rail structures. More particularly, the structure 900 can be placed on a gravel bed arranged on an earth track. It is also possible to place the structure 900 in situ, several centimetres above a previously prepared substrate, and then to fix it in the set position by pouring a suitable pouring mortar into the space between the substrate and the underside 907 of the structure 900. Another advantage of the structure 900 is that by comparison with conventional bearing structures with sleepers, and compared with the abovementioned embedded rail structures, it can have a greatly reduced width. However, depending on the stability and elasticity of the foundation, it may be desirable for the structure to have a width which is substantially greater than the width of the track as determined by the mutual distance of the rails 920. This advantage is offered by the embodiment 800 illustrated in figure 8A, which at its underside is provided with two flanks 815, the side walls of which can be directed vertically, as shown. The cast tension bars 813 extend over the full width of the core 803 between the side walls of the flanks 815. If use is made of detached tension bars and tension blocks 814, said tension blocks 814 advantageously have a rectangular cross section. Figure 9 shows diagrammatically a cross section of a second embodiment of a bearing structure 1001 according to the present invention, which embodiment in general is a slab shape and is therefore also indicated by the term "track slab", and which is advantageously, but not necessarily made of concrete. At its top side, the track slab 1 has two parallel profiled ridges 1002 directed in the lengthwise direction of the track slab. Each ridge 1002 has a top face 1003 and a slanting outside side face 1004, and also an inside side face 1005. The outside side face 1004, the angle of gradient of which can be approximately 45°, can run through to a bottom face 1006 of the track slab, or into a side face 1007 of the track slab, but in the preferred embodiment shown the outside side face 1004 merges from the ridge 1002 into a flat shoulder part 1008 of the track slab, which serves to provide better lateral stability. A top surface 9 of the track slab situated between the ridges 2 is slightly concave, for guiding rainwater and the like to discharge channels, which for the sake of simplicity are not shown. Each ridge 2 has a rail accommodation area 1010 with a substantially horizontal bottom or rail bearing surface 1011, an outside side wall 1012 and an inside side wall 1013. The rail bearing surface 1011 extends outwards from the top edge of the inside side face 1005 of the ridge 1002, which inside side face 1005 can be directed substantially vertically, but is preferably slightly slanted. The outside side wall 1012 extends between the inside edge of the top face 1003 and the outside edge of the rail bearing surface 1011, and can be directed substantially vertically. The inside side wall 1013 is defined by a metal or plastic plate 1020 or the like, which is fixed on the inside side face 1005 of the ridge 1002. As shown in the left half of figure 9, the plate 1020 can be fixed by means of a bolt 1021 which engages in a plug placed in a hole drilled in the ridge 1002. Other ways of fixing the plate 1020 will also be possible, as will be clear to a person skilled in the art. In order to prevent problems as a result of temperature variations, the side plates 1020 are preferably no longer than approximately 3 m. In the left half of figure 9 it is also shown that a rail 1030 has been placed in a rail accommodation area, the rail accommodation area for the rest being filled with a casting compound 1031, for example of rubber or plastic, for fixing the rail 1030 and exerting a vibration-damping effect. The type of this compound 1031, and the way in which it is applied, can be the same as the type and way respectively described above. In particular, it is illustrated in figure 9 that the rail 1030 does not rest directly on the rail bearing surface 1011, but that a vibration-damping layer, for example a sheet of rubber or suitable plastic, is interposed. Should it be necessary to replace the rail 1030, it is relatively simple to remove the side plates 1020, after which the casting compound 1031 can be approached from the side in order to detach the rail 1030. After a replacement rail segment has been fitted, the side plates 1020 are fixed again, and the new rail is secured with casting compound . Instead of a casting compound 1031, the rail 1030 can also be clamped by means of rubber or plastic clamping blocks, which are pressed down by the side plates 1020. In that case the removal of the rails 1030 is even simpler, because when the side plates 1020 are removed such clamping blocks can easily be removed, after which the rails 1030 can also easily be removed. The slab-shaped bearing structure or track slab 1001 shown in figure 9 is suitable for being placed on a traditional substrate. More particularly, the structure can be placed on a gravel bed arranged on an earth track. It is also possible to lay the structure in situ, a few centimetres above a previously prepared substrate, and subsequently to fix it in the set position by pouring a suitable pouring mortar into the space between the substrate and the underside of the structure. However, it will be clear to a person skilled in the art that the track slab described can easily be adapted for use in conjunction with a trough-shaped track structure 200 of the type described above . It will be clear to a person skilled in the art that the scope of the present invention is not restricted to the examples discussed above, but that various alterations and modifications thereto are possible without departing from the scope of the invention as defined in the appended claims . It is therefore possible, for example, for the L- shaped groove mould parts 410 of the abovementioned mould 400 to be composed of two individual parts situated at right angles to each other, one part defining the horizontal groove mould face 411, and the other part defining the vertical groove mould face 412. With regard to the outer mould for the trough- shaped track structure 200, it has been stated that said mould is composed of two halves which can be slid onto the substrate. However, it is also possible to make said mould movable in the vertical direction, in which case said outer mould can be designed in one piece .

Claims: Claims 1. Bearing structure for a rail track, comprising: a substantially slab-shaped, preferably concrete core (101; 801; 901; 1001) which at its top side is provided with two parallel, groove-shaped rail accommodation areas (104; 804; 904; 1010), wherein each rail accommodation area has a bottom (106; 806; 906; 1011) which is defined by the material of the core (101; 801; 901; 1001), wherein each rail accommodation area has a first side wall (105; 805; 905; 1012) which is defined by the material of the core (101; 801; 901; 1001), and wherein each rail accommodation area has a second side wall (109; 809; 909; 1013) opposite the first side wall (105; 805; 905; 1012); characterized in that the second side wall (109; 809; 909; 1013) of a rail accommodation area (104; 804; 904; 1010) is defined by an element (110; 810; 910; 1020) which can be detachably fixed to the core (101; 801; 901; 1001) . 2. Bearing structure according to claim 1, wherein, with respect to the rail accommodation area (104; 804; 904), the first side wall (105; 805; 905) is situated on the side of the centre of the core, and the element (110; 810; 910) which is detachably fixed to the core is situated on the outside of the bearing structure. 3. Bearing structure according to claim 1 or 2 , wherein the said element (110; 810; 910) is a metal plate. 4. Bearing structure according to claim 2 or 3 , wherein the concrete core (101; 801; 901) has a side wall (102; 802; 902) which adjoins the bottom (106) of a rail accommodation area (104; 804; 904), and wherein the said element (110; 810; 910) is fixed against said side wall. 5. Bearing structure according to claim 4, wherein the said element (110; 810; 910) is fixed to the concrete core (101; 801; 901) by means of tension bars (111; 811^ 811 2 ; 911 lf 911 2 ) . 6. Bearing structure according to claim 5, wherein said side wall (102) of the core (101) is directed substantially vertically, and wherein said tension bars (111) extend over the full width of the core (101) between the side walls (102) . 7. Bearing structure according to claim 5, wherein said side wall (802; 902) of the core (801; 901) forms an angle greater than zero with the vertical, wherein said tension bars (811 1# 811 2 ; 911^ 911 2 ) form an angle greater than zero with the horizontal, and wherein the core (801; 901) is provided with tension wires (813; 913) at a level which corresponds to the inside ends of the tension bars (811^ 811 2 ; 911 1; 911 2 ) . 8. Bearing structure according to one of claims 2-7, wherein the core (801) is provided with flanks (815) which extend in the widthwise direction of the core beyond said elements (810) . 9. Bearing structure according to one of claims 2-8, wherein the core (101; 801; 901) and the rail accommodation areas (104; 804; 904) have a curved contour for defining a bend section of the rail track. 10. Bearing structure according to one of claims 2-9, wherein a guide structure (500) for magnetic trains (3) is fixed to the said elements (110; 810; 910). 11. Bearing structure according to one of claims 2-8, wherein a guide structure (500) for magnetic trains (3) is fixed to the said elements (110; 810; 910), wherein the core (101; 801; 901), the rail accommodation areas (104; 804; 904) and the guide structure (500) have a curved contour for defining a bend section of the rail track, the guide structure (500) defining a track surface which in a direction perpendicular to the lengthwise direction of the core (101; 801; 901) forms an angle greater than zero with a track surface defined by the rail accommodation areas ( 104 ; 804 ; 904 ) . 12. Bearing structure according to claim 10 or 11, wherein the guide structure (500) comprises a multiplicity of guide structure segments placed in line with each other, wherein each of those segments is fixed by means of at least three connecting supports (510 1; 510 2 , 510 3 ) to a said element (110; 810; 910), wherein a first connecting support (510 ! ) is situated midway along the length of a segment and is designed to ensure an absolute fixing of the centre of said segment to said element (110; 810; 910) , and wherein a second connecting support (510 2 ) and a third connecting support (510 3 ) are situated near ends of the segment and are designed to permit movements in the lengthwise direction of the segment. 13. Bearing structure according to claim 1, wherein, with respect to the rail accommodation area (1010) , the first side wall (1012) is situated on the outside of the bearing structure, and wherein the element (1020) detachably connected to the core is situated on the inside of the rail accommodation area (1010) in question. 14. Bearing structure according to claim 13, wherein each rail accommodation area (1010) is defined in a ridge (1002) of the core (1001) , and wherein the element (1020) is fixed to an inside side face (1005) of the ridge (1002) . 15. Bearing structure according to claim 13 or 14, wherein the said element (1020) is a metal plate. 16. Bearing structure according to one of claims 13-15, wherein the core (1001) and the rail accommodation areas (1010) have a curved contour for defining a bend section of the rail track. 17. Rail track system (1) comprising a bearing structure according to one of claims 1-16, fixed in a trough-shaped track structure (200) with a substantially U- shaped cross section, which trough-shaped track structure (200) is preferably made of concrete. 18. Rail track system according to claim 17, wherein the trough-shaped track structure (200) has a bottom (201) on which spacers (203) are formed, preferably being an integral unit with the bottom (201) , and wherein the bearing structure is fitted on those spacers. 19. Rail track system according to claim 18, wherein the combination of the trough-shaped track structure (200) and the bearing structure forms a bearing unit. 20. Rail track system according to one of claims 17-19, intended for two or more tracks, comprising two or more single- line track structures (200) disposed next to each other, which are individually arranged on a foundation (6) , a platform structure (7) possibly being mounted between two adjacent track structures (200) . 21. Method for manufacturing with great accuracy a substantially slab-shaped concrete core (101; 801; 901; 1001) for a bearing structure for a rail track, which concrete core at its top side is provided with two parallel groove-shaped rail accommodation areas (104; 804; 904; 1010) , wherein each rail accommodation area has a bottom (106; 806; 906; 1011) and a side face (105; 805; 905; 1012) ; which method comprises the steps of: a) providing a lower mould (400) , comprising two elongated, bendable groove mould parts (410) with a substantially L-shaped cross section, which are disposed parallel to each other, for defining rail accommodation areas, and also a multiplicity of bendable elongated mould bottom parts (413) disposed between the trough mould parts (410), for defining a top face (103; 803; 903) of the core (101; 801; 901), and also two bendable elongated side mould parts (414) disposed next to the groove mould parts (410), for defining side faces (102; 802; 902) of the core (101; 801 ; 901 ) ; b) possibly bending the trough mould parts (410) , the mould bottom parts (413) and the side mould parts (414) to a predetermined, desired shape which corresponds to the desired shape of a core (101; 801; 901) to be formed, the bending of the various mould parts preferably being carried out under the control of a computer or microprocessor; c) placing an upper mould for forming an underside (107; 807; 907) of the core to be formed; d) pouring concrete into the possibly bent mould (400) ; and e) removing the formed core from the mould (400) after the concrete has hardened sufficiently. 22. Method for manufacturing a trough-shaped track structure (200) with a substantially U-shaped cross section, comprising the steps of: a) providing a mould (300) , comprising an inner formwork part (301) with an outer contour which corresponds to the inner contour of the track structure to be formed, and an outer formwork (303, 304) with an inner contour which corresponds to the outer contour of the track structure to be formed, wherein the inner formwork part (301) is immovably fixed on a suitable base (302) , and wherein the inner formwork (303, 304) is movable; b) pouring concrete into the mould (300) ; c) removing the outer formwork (303, 304) when the concrete has hardened sufficiently; d) lifting the moulded track structure (200) out of the inner formwork (301) after the concrete has hardened sufficiently; and e) allowing the moulded track structure to rest so that shrinkage and creep phenomena settle down. 23. Method for manufacturing a rail track system (1), comprising the steps of : manufacturing a trough-shaped track structure by means of the method of claim 22; placing the moulded track structure in an upright position; manufacturing a slab-shaped bearing structure by means of FEUILLE RECTIFIEE (REGLE 91) the method of claim 20 or 21; placing the moulded bearing structure in an upright position; mounting the moulded bearing structure in the moulded track structure . 24. Method for manufacturing a rail track system (1), comprising the steps of : manufacturing a trough-shaped track structure by means of the method of claim 22; manufacturing a slab-shaped bearing structure by means of the method of claim 20 or 21, wherein, after the concrete has been poured into the mould (300) , but before the concrete has hardened, the moulded bearing structure is placed upside down on the not-hardened concrete in the mould (300) , in order to form an integral unit in this way; and allowing the concrete to harden in the mould (300) ,- removing of the combination of the track structure (200) and the bearing structure (100) from the mould (300) after the concrete has hardened sufficiently. 25. Mould (400) for the manufacture of a core (101; 801; 901) of a slab-shaped bearing structure (100; 800; 900), comprising: two elongated bendable trough mould parts (410) with a substantially L-shaped cross section which are disposed parallel to each other, for defining rail accommodation areas, and also a multiplicity of bendable elongated mould bottom parts (413) disposed between the trough mould parts (410), for defining a top face (103; 803; 903) of the core (101; 801; 901), and also two bendable elongated side mould parts (414) disposed next to the groove mould parts (410) , for defining side faces (102; 802; 902) of the core (101; 801; 901) ; and means (421, 422, 423, 424) for bending the bendable mould parts (410, 413, 414) into a desired shape. 26. Mould according to claim 25, wherein the above- mentioned means (421, 422, 423, 424) for bending the bendable mould parts (410, 413, 414) into a desired shape comprise : a multiplicity of first adjustable positioning devices (421) disposed at different length positions of a groove mould part (410) , for accurately setting the vertical position of said groove mould part (410) relative to a fixed reference plane (420) at those length positions; a multiplicity of second adjustable positioning devices (422) disposed at different length positions of a groove mould part (410) , for accurately setting the horizontal position of said groove mould part (410) relative to a fixed reference at those length positions; a multiplicity of third adjustable positioning devices (423) disposed at different length positions of a mould bottom part (413), for accurately setting the horizontal and vertical position of said mould bottom part (413) relative to a fixed reference at those length positions; a multiplicity of fourth adjustable positioning devices (424) disposed at different length positions of a side mould part (414), for accurately setting the horizontal position of said side mould part (414) relative to a fixed reference at those length positions; wherein the said positioning devices (421, 422, 423, 424) are preferably under the control of a control device such as a computer or a microprocessor.

Inventors: GRIMBERGEN FREDERIKUS ADOLF JO, GRIMBERGEN, FREDERIKUS, ADOLF, JOSEPH
Applicants: GRIMBERGEN FREDERIKUS ADOLF JO, GRIMBERGEN HOLDING B V, GRIMBERGEN HOLDING B.V., GRIMBERGEN, FREDERIKUS, ADOLF, JOSEPH
Application year: 1999
Main classification: E01B1
IPC codes: B28B7, E01B1, E01B2, E01B21, E01B25