The invention relates to a U-section structure used to delineate the tracks of a public transport vehicle.
A U-section structure designed to delineate the trackway of a public transport vehicle is known  the U-section structure comprising a horizontal lower wall which forms a slab on which the vehicle is designed to run  and two vertical side walls designed to flank the tracks laterally  each side wall at its upper free end bearing a horizontal ledge.
Such a U-section structure is very often used to build viaducts and extends between two adjacent piers. However  such a structure  which is self-supporting  which means to say that rests directly on the piers  is of a limited length (35 m long at most).
It is an object of the present invention to create a structure that exhibits the same advantages as a U-section structure but which can have a longer length while at the same time remaining self-supporting.
The invention thus relates to an element for delineating the tracks of a public transport vehicle  comprising a U-section structure comprising a horizontal lower wall that forms a slab on which the vehicle is able to run  and two vertical side walls which are designed to flank the trackway laterally  each side wall at its free upper end bearing a horizontal ledge. According to the invention  the delineating element comprises a lower structural element borne by the horizontal lower wall and of one piece with the U-section structure.
Combining the lower structural element with the U-section structure into a one-piece structure makes a complex U-section structure the length of which can be far greater and even as much as 120 m.
Further features and advantages of the invention will become clearly apparent from the description given thereof hereinafter by way of entirely nonlimiting indication and with reference to the attached drawings in which:
- Figure 1 is a view in cross section of a U-section structure to the upper surface of the horizontal ledge of one vertical sidewall of which is anchored a post for supporting a catenary system  according to a first aspect of the present invention;
- Figure 2 is a perspective view from above of a viaduct pier collaborating with two U-section structures placed side by side  each U-section structure comprising a cutout to accept part of a protrusion projecting from the pier  according to a second aspect of the present invention;
- Figure 3 is a partial perspective view of a U-section structure to the upper surface of the horizontal ledge of one vertical side wall of which are anchored platform-access doors  according to a third aspect of the present invention;
- Figure 4 is a front view illustrating the lifting of a U-section structure delineating two trackways using a lifting beam according to a fourth aspect of the present invention;
- Figure 5 is a side view illustrating the launch of a U-section structure  using a launching beam according to a sixth aspect of the present invention;
- Figure 6 is a view in cross section of a modified U-section structure according to a seventh aspect of the present invention; and
- Figure 7 is a perspective view of a viaduct using modified U-section structures according to the seventh aspect of the present invention.
A U-section structure  referenced 1 in Figure 1  according to the present invention  is used to delineate a trackway for a public transport vehicle  notably a vehicle that travels along rails 2  such as a train or metro line  or a vehicle guided by lateral rails  such as a tyred metro train.
The U-section structure 1 comprises a horizontal lower wall 3 which forms a slab on which the vehicle runs  and two vertical side walls 4 which flank the trackway laterally.
These two vertical walls 4 extend vertically from the horizontal lower wall 3 up to a level substantially level with the floor of a vehicle running along the tracks. Each vertical wall 4 may be inclined with respect to the vertical  notably in the direction which has them more widely separated at their top than at their bottom. These two vertical walls 4 notably serve as protection in the event of the vehicle becoming derailed.
Each vertical wall 4 at its upper free end bears a horizontal ledge 5 which is designed to form a vehicle evacuation path. Each horizontal ledge 5 may project beyond the corresponding vertical wall 4 on the track side  on the side opposite to the track  or on both sides  depending on the configuration of the U-section structure 1.
In the present embodiments  the U-section structure 1 is made of concrete  and forms a structure that operates as a single unit. This unit is self-supporting for one viaduct pier to another.
The trackway is delineated by an alignment of U-section structures 1 butted one after the next.
According to a first aspect of the present invention  illustrated in Figure 1  at least one of the horizontal ledges 5 at the free end of the vertical walls 4 acts as a base for anchoring posts 6 which are designed to carry the catenary system 7 that supplies the vehicle with power.
Because the height of the catenary system 7 is dictated by the gauge of the tracks  the advantage of such an arrangement is that the posts 6 used can be smaller in size than conventional posts. Thus  on the one hand  their height can be reduced by that of the corresponding vertical wall 4 (typically around 1.5 m) and  on the other hand  because of the reduction in height  their cross section can also be reduced. This then results in a significant saving on the material of which the posts are made  consequently leading to appreciable cost savings.
For preference  the U-section structure 1 has its reinforcement strengthened at the location of these posts 6 (for preference  the reinforcing steels are reinforced).
The second aspect of the present invention  illustrated in Figure 2  relates more specifically to a U-section structure 1 delineating a viaduct trackway. Typically  in such instances  the viaduct comprises an alignment of piers 8 supporting an alignment of U-section structures 1 that forms the deck of the viaduct  the U-section structures 1 being self-supporting.
More specifically  each U-section structure 1 forms a U-section span which extends longitudinally from a first pier 8 to a second pier. More precisely  each lower wall 3 of a U-section structure 1 extends approximately from the middle of the first pier 8 to the middle of the second pier so that two U-section structures 1 butted together each rest on half of one and the same pier.
In order to limit the movements of U-section structure 1 with respect to the piers 8 and with respect to the other U-section structures 1 in the event of seismic tremors  the viaduct is fitted with antiseismic key systems which require the use of an appreciable number of special-purpose elements.
According to the second aspect of the present invention  the lower wall 3 of a U-section structure 1 comprises a cutout 9 at each of its two longitudinal ends 10 (which ends are designed to be supported by a corresponding pier). Correspondingly  each pier at its top 11 comprises a vertical protrusion 12 extending along the mid-plane of the pier 8. For preference  the protrusion 12 is in one piece with the remainder of the pier 8. Thus  once correctly positioned on two piers  each cutout 9 of the U-section structure 1 encloses the corresponding half of the protrusion 12 of the corresponding pier 8 (the half of the protrusion 12 preferably having a shape that complements that of the cutout 9)  and this provides immobilization  or in other words acts as an anti-seismic key. This immobilization is strengthened by the presence of the longitudinal end of the other U-sectional structure borne by the same pier.
Thus  because of their complementary geometries  the U-section structure and the pier form a particularly simple and economic anti-seismic key.
For preference  each cutout 9 runs vertically over the entire thickness of the horizontal wall 3 of the U-section structure 1. In such instances  in order not to introduce problems with levelling  the height of the corresponding protrusion 12 is such that its upper surface reaches the upper level of the upper surface of the horizontal wall 3 and thus forms part of the slab on which the vehicle runs.
The third aspect of the present invention  illustrated in Figure 3  relates more specifically to a U-section structure 1 situated in the region of a station along the trackway  or which could subsequently be used to create such a station. In such instances  because of the height of the vertical walls 4 of the U-section structure 1  the horizontal ledge 5 of each vertical wall forms that part of the station platform 13 that is closest to the track (or is designed subsequently to form such a part of the station platform).
According to the third aspect of the present invention  the part of the aligned set of U-section structures 1 which is positioned in the region of an existing station or in the region designed to be the site of a future station  is structurally continuous (for example by using prestressing cables that pass through the U-section structures of this region) with no expansion joints. As a result  variations in temperature will not cause any relative movement between these U-section structures.
It is therefore possible to use these horizontal ledges 5 (which are the elements of the station platform which are closest to the corresponding track) as supports for access doors 14 used to prevent access to the track and allow access to the vehicle when the vehicle is at the station.
More specifically  the upper surface of the horizontal ledges 5 of the U-section structures 1 are then used as surfaces to which to anchor vertical posts 15 used as structural elements of the access door and step  system 16 on which the access doors 14 are intended to slide and the emergency access doors 17 are intended to open.
Hitherto  when the trackway at which the station platform was built was delineated by an aligned set of U-section structures  either the access doors were supported by the part of the station platform  that was closest to the tracks  that formed an integral part of the rest of the station platform and was not connected to the upper ledges of the U-section structures in order not to be subjected to the relative movements thereof  or the upper ledges of the U-section structures formed that part of the station platform that was closest to the track and the access doors were borne by the part of the station platform situated just beyond the edge of the upper ledges so as not to be subjected to the relative movements of the latter. In the former instance  the station platform was particularly complicated and costly  and in the latter instance the effectiveness of the access doors was reduced because of the empty space between them and the edge of the station platform.
The fourth aspect of the present invention  illustrated in Figure 4  relates more specifically to the installation of the U-section structures 1 when creating the aligned set of structures. It relates more precisely to prefabricated U-section bridge segments 1 of relatively short length.
Hitherto  the handling of U-section structures often required through-openings to be made in the vertical walls  securing devices (such as metal bars) to be inserted therein and connected to a lifting system (such as a gantry crane). Such  a system was equipped with means that prevented any release during the handling process. As a result  moving the U-section structures around was a fairly laborious task  both when fitting the securing devices and when removing them.
According to this fourth aspect  the lower surfaces of the two horizontal ledges 5 are used as lifting surfaces for lifting the U-section structure 1.
This makes the handling of such a U-section structure far simpler: All that is required is a lifting beam 18 supported by a gantry crane 19. This lifting beam 18 runs longitudinally  transversely to the trackway  substantially from one of the two vertical walls 4 of a U-section structure 1 to the other. In use  the lifting beam 18 is arranged in such a way that the upper surface of each of its two longitudinal ends 20 fits under the corresponding lower surface of the two horizontal ledges 5 (in this particular instance  the lower surface of the interior part of each horizontal ledge 5  which means the part extending towards the side of the trackway). Next  the beam 18 is lifted so that firstly it comes into abutment against the U-section structure 1 and secondly allows the structure 1 to be lifted and moved around. For preference  protective elements 21 (made of a strong elastomeric material) are positioned on top of the upper surface of the beam 18.
With this new use  there is no longer any need to use additional attachment devices for temporarily connecting the beam to the U-section structure  nor is there any longer any need to make holes therein.
The fifth and sixth aspects of the present invention  which are illustrated in Figure 5  relate more specifically to the installation of the U-section structures 1 when creating the aligned set of structures. It relates more specifically to U-section spans (preferable self-supporting) of relatively significant length (at least 10 m long) extending between two adjacent piers 8.
In order to install such a U-section structure 1  it is usual practice to use a launching beam 22 which launches this U-section structure 1 from the last pier that have already had a U-section structure 23 installed  to the next pier 8.
The launching systems used to allow both the launching beam and the U-section structures  around are particularly complicated.
According to the fifth aspect  the upper surfaces of the two horizontal ledges 5 of a first U-section structure 23 are used either as runway surfaces for the launching beam 22 so that the latter can be installed after the first U-section structure 23  and then a launch and an installation of a second U-section structure 1 after the first U-section structure 23 (once the launching beam 22 has been moved along) or as supports for rails on which the launching beam 22 will run.
According to the sixth aspect  the upper surfaces of the two horizontal ledges 5 of a first U-section structure 23 are used as runway surfaces for a second U-section structure 1 as said second U-structure is launched by a launching beam 22 and is installed after the first U-section structure 23.
Thus  the launching beam used can be of a far simpler design.
According to a seventh aspect illustrated in Figures 6 and 7  associated with the U-section structure 1 is a lower structural element 24 borne by the horizontal lower wall 3 of the U-section structure 1. The U-section structure 1 and the lower structural element 24 form a one-piece structure 25.
In this example  the lower structural element 24 is formed of a box section 24. More specifically  the lower box section 24 is of rectangular or trapezoidal cross section. In this particular instance  it comprises a horizontal upper wall 26  formed by the horizontal lower wall 3 of the U-section structure 1  two vertical side walls 27 extending downwards from the horizontal upper wall 26 of the box section 24  and a lower wall 28 extending between the two lower free ends of the vertical side walls 27 of the box section 24.
In this instance  the width of the lower structural element 24 (of the box section 24) is smaller than that of the U-section structure 1. 
The length of such a complex U-section structure 25 is greater than that of a conventional U-section structure 1. Thus  whereas a U-section structure 1 can extend over 30 m (35 m at most)  a complex U-section structure 25 can be as much as 120 m long. When the complex U-section structure 25 exceeds a length of 35 m  it is then produced by assembling with prestress bridge segments which are either cast in situ or prefabricated.
Increasing the length of the U-section structure means that the separation between the piers 8 of the viaduct can be increased and the number of structures used to delineate the trackway can be reduced.
Rather than being a box section  the U-section structural element could be a rib  i.e. the equivalent of a box section without a vertical lateral wall and in which the lower wall of the structural element is continuous with the lower wall of the U-section structure  which is thus extra-thick  or several ribs.
In general  the use of a U-section structure  with the two vertical walls 4  affords a high level of safety in the production of a viaduct: because the structure 1  25 is prefabricated (at the works or on site)  there is no need to fabricate or install protective parapets for workers carrying out the work that follows on from the main concrete works (such as the installation of rails  cables  etc.)  because the vertical walls 4 perform this role. Elimination of parapet management means that substantial cost savings can be made and the time taken to build the viaduct can be reduced.
 
We Claim:
1. Element for delineating the tracks of a public transport vehicle  comprising a U-section structure (1) comprising a horizontal lower wall (3) that forms a slab on which the vehicle is able to run  and two vertical side walls (4) which are designed to flank the trackway laterally  each side wall (4) at its free upper end bearing a horizontal ledge (5)  characterized in that it comprises a lower structural element (24) borne by the horizontal lower wall (3) and of one piece with the U-section structure (1).
2. Delineating element according to Claim 1  characterized in that the lower structural element (24) is a box section (24).
3. Delineating element according to Claim 2  characterized in that the box section (24) is of rectangular or trapezoidal shape.
4. Delineating element according to either of Claims 2 and 3  characterized in that the box section (24) comprises a horizontal upper wall (26)  formed by the horizontal lower wall (3)  two vertical side walls (27) extending downwards from the horizontal upper wall (26)  and a lower wall (28) extending between the two lower free ends of the vertical side walls (27).
5. Delineating element according to Claim 1  characterized in that the lower structural element (24) is a rib.
6. Delineating element according to one of Claims 1 to 5  characterized in that the width of the lower structural element (24) is less than that of the U-section structure (1).