TRANSITION STRUCTURE AND CONSTRUCTION METHOD

Abstract

 The present invention relates to a transition structure consisting of prefabricated reinforced concrete elements arranged in areas of a railway or highway where there is a transition in stiffness, as well as to the method necessary for the construction thereof.

Description

Object of the Invention

[0001] The present invention relates to a transition structure consisting of prefabricated reinforced concrete elements arranged in areas of a railway or highway where there is a transition in stiffness, as well as to the method necessary for the construction, manufacture, transport, stockpiling and placement thereof.

[0002] Given the problems existing in the transitions in stiffness, the main objective of this solution is to obtain a transition which allows (vertical) stiffness variation to occur gradually between earthworks and engineering structures (viaduct, underpass, draining elements, etc.), minimizing settlements and maintenance tasks required by the current transition designs, actions that are encompassed within the sector of civil engineering work.

[0003] The present invention applies to highway, freeway and railway construction and repair.

State of the Art

[0004] Different methods and devices designed for minimizing stiffness variation, mainly vertical stiffness variation, existing between earthworks and engineering structures are known in the state of the art.

[0005] The vertical stiffness of a railway or freeway is understood as the resistance offered by the assembly of the constructed railway or freeway structure against deformation under the force/load applied in the vehicle-infrastructure contact area (by a wheel of a railway vehicle), this value being one of the most relevant indicators of the quality and safety of the (railway) infrastructure, said value being closely related to the sizing of the elements of the infrastructure.

[0006] Taking railway infrastructure as an example, as is well known by the technicians responsible for constructing railway platforms, to the extent possible the vertical stiffness of the track must have a value that is as homogeneous as possible, preventing significant changes. Transverse crossing structures and structures bypassing geographical features or already existing infrastructures, particularly the abutments thereof, usually have a high stiffness, with no or very little vertical movements. In contrast, the embankments for accessing said structures have much higher movements and therefore less vertical stiffness. This fact causes a significant vertical stiffness variation in a short area.

[0007] To prevent the detrimental effects (reduced comfort, lower vehicle speed, increased wear of the moving material and of the track, higher maintenance costs, etc.) generated by this abrupt change an element which distributes as homogeneously as possible the change in stiffness is to be arranged on the track, said function being performed by the so-called "transition structures or wedges".

[0008] Currently in Spain, the type of wedges, their design and the implementation and test methodology are classified by the Railway Infrastructure Administrator (ADIF) in the Technical Specifications for Platform Projects (PGP 2008), as well as in the Codes and Recommendations for Drafting Platform Projects (IGP 2008) also elaborated by ADIF, classifying transitions in stiffness in 4 main cases, said solutions being formed by various granular materials arranged in the form of a "wedge". Similarly, the remaining main railway administrations have elaborated technical sheets describing the main characteristics for constructing the transitions by varying the type of material in each of them and the arrangement thereof.

[0009] From theoretical viewpoint, the operation of said granular wedges fulfills their function, allowing gradually achieving the stiffness of the engineering structure, adapting the deformability of the track to that it has on the structure in question.

[0010] However, experience has shown that, despite adopting the different considered solutions, probably due to the difficulty in correctly implementing these structural units (materials and implementation times), there are still significant stiffness variations causing, in many cases, the problem to remain unresolved and a series of problems both in the infrastructure and in the vehicles and passengers onboard same. That is fundamentally due to the fact that the construction of granular wedges has a series of problems which prevent correctly carrying out same in most cases.

[0011] The state of the art does not disclose any solution such as that considered in the present application, though it does indeed disclose solutions using granular wedge systems for carrying out a gradual transition in the vertical stiffness of the railways, comprising a system for implementing contiguous embankment at the point with maximum stiffness (structure) by means of duly placing and compacting granular materials with specific characteristics that are treated or not treated with cement.

[0012] However, this granular wedge system has specific problems such as:

• High economic costs (material extraction, acquisition and transport, qualified staff, machinery, regular maintenance).
• Long implementation time which exposes the materials to the action of climatic factors (causing excessive implementation time and frequent delay).
• High susceptibility to attacks by climate, mainly water.
• Difficult quality control over end product and implementation process.
• Reduced user comfort and safety.
• Uncertain behavior during use.
• Great environmental costs in view of the difficulty in obtaining granular material, which entails the opening of new quarries and prohibitive transport costs with high CO₂ emissions.
• Need of manufacturing the material treated with cement in plants, which entails constructing new plants if the infrastructure is far away from the concrete production centers.

[0013] With the fundamental objective of enhancing economic viability both of the conventional lines and the new high-speed lines that are being developed throughout the world, as well as for assuring and maintaining the success thereof in the future and, given that the embankment-structure transitions require extensive maintenance, causing a significant cost increase, the present invention is proposed as a solution to the existing problems. This solution does not apply exclusively to railways rather, as mentioned, also applies to highways such as freeways and motorways.

Description of the Invention

[0014] The object of the present invention is a transition structure or wedge for carrying out transition in vertical stiffness formed by prefabricated concrete modules whereby successfully reducing the effects of deformations produced in the superstructure (of the track) as a consequence of massive discontinuous variations along an earthwork as a result of the presence of transverse engineering structures, of the interchange with an overpass or viaduct, etc. is achieved.

[0015] The premises determining the design of the transition wedges object of this application, as well as their dimensions, are those of creating a stable structure as a whole, capable of correctly withstanding and transmitting forces, obtainable with the current technology under a structural and economical efficiency. The most suitable wedge has been chosen through a problem of multiple criteria or multicriterion decision-making.

[0016] The calculation results are based on the regulation relating to the materials used:

• EHE-08. Code on structural concrete EHE.
• EC-2. Eurocode 2, "Concrete Structure Project".
• IGP-2008. Codes and Recommendations for Drafting Platform Projects.

[0017] The transition structure proposed by the present invention is formed by at least two prefabricated reinforced concrete slabs or plates, one being located on the other defining two heights and two rows, the width of the slabs being equal to one another and also preferably at least the width of the cross member in the case of railways due to the fact that the maximum stresses are in the central part, an area which must be covered with the solution and at least the width of the carriageway in the case of highways. Likewise, in those cases in which the width of the track is greater than the greatest width possible of the slabs due to slab design or transport reasons, slabs can be arranged in parallel increasing their width, being able to be mechanically or non-mechanically attached or coupled.

[0018] The structure is formed by solid slabs suitably stacked one on top of the other, the structure or wedge being formed by prefabricated pieces with at least one of their dimensions, preferably the length, different, being suitably aligned close to the face of the engineering structure. Such solution allows a significant variability, the number of heights formed by prefabricated slabs or plates being able to be increased for being adapted, in each specific case, to the difference in stiffness of the structure in question. The slabs are arranged in rows and in height such that the length of the row of bottom slabs is greater than the length of the row of top slabs, the transition structure defining a succession of steps at the end opposite that of the face of the engineering structure. Each height will be formed by at least one row having the same length.

[0019] If the arrangement of the railway or freeway slopes with respect to the transition (slope angle of between 0 and 45°), the solution is also valid since the shape of the first slabs, outer slabs of the wedge or structure would change, such that it will adjust to the slope angle required and therefore to the arrangement of the track. The system of placing successive slabs would be the same.

[0020] If there is a need to construct the structure on a ground with insufficient bearing capacity, the platform must be previously improved (replacing same with another more suitable platform, adding cement, etc.) and, even bearing the solution, if necessary, such that it is assured in all cases that the transition has a suitable bearing capacity.

[0021] It must be considered that these slabs are placed, in principle, without any type of connection element, there being envisaged that at least one of the surfaces of the slab has a rough surface, such that its behavior as a continuous joint structure results exclusively from the moving friction between the contact surfaces between the slabs. Likewise, it is possible to introduce an element or a material between the slabs during the working phase which increases the stress mobilizing capacity between one slab and another, preventing movement between slabs.

[0022] In the case that the friction between the slabs cannot be assured, it is possible to size the slabs with through holes which subsequently allow sewing or attaching the slabs by means of metal bolts, pins or any other device, as well as the case of constructing plates with a morphology which allows a tongue and groove coupling system both in the horizontal plane and in the vertical plane such that, by attaching the slabs, the assembly works as a whole. Said tongue and groove coupling can be made both in the vertical plane and in the horizontal plane such that the slabs can be coupled with other slabs located above or below them as well as with other slabs located in their same plane.

[0023] This configuration aims to provide a solution to the different types of transitions defined by the infrastructure administrator of each country. In the case of Railway Infrastructure Administrator (ADIF) in Spain, this defines 4 transition prototypes, H being the height of soil above the transition structure:

• Case 0 ≤ H ≤ 0.5.
• Case 0.5 ≤ H ≤ 2.
• H≥ 2.
• Abutment.

[0024] A basic solution of a transition structure according to the present invention consists of a wedge formed by at least two prefabricated reinforced concrete slabs, with the same width and preferably the same thickness, but the first slab having a length of about twice the length of the second slab, and the first slab being arranged as a base and the second slab being arranged thereon, two rows thus being defined.

[0025] Said first slab can rest on the stratum where the engineering structure (viaduct, underpass, draining element, among others...) rests or on at least one post or improved ground with sufficient bearing capacity, in turn supported on the stratum where said engineering structure rests, one alternative or another depending on the height of the engineering structure and on the quality of the support stratum.

[0026] If it is necessary to construct a transition structure with a larger number of prefabricated slabs, defining more than two rows, said slabs will be arranged such that the contact areas of the slabs of one row do not coincide with the contact areas of the slabs of the top or bottom row, slabs with at least two different lengths being used for said construction. The creation of a continuous vertical joint along the entire length of the wedge will thus be prevented.

[0027] An alternative to the preceding solution, which may be useful under specific circumstances, is the possibility of arranging slabs having the same width and the same length, said dimensions not having to be equal to one another. Therefore, when creating different rows and heights by placing one slab on top of another, continuous vertical joints separating slab columns will be created.

[0028] Likewise, the method for installing these elements for the formation of the transition structures or wedges object of the present invention does not require construction methods that are significantly different from those already known, resulting in advantages in terms of time reduction and greater control over both manufacture and implementation. Said installation method comprises the following steps:

• Manufacturing the necessary prefabricated concrete modules (in prefabricated product plant) intended for the configuration of the complete structure (wedge), with suitable quality control over materials, process and end product, with a seal of quality. Said elements will be available before starting the works performed on the trace of the structure.
• Transporting and placing said concrete elements on the trace of the structure according to the final arrangement adopted for same and as described in terms of the slab arrangement.
• Spreading the granular material and compacting with suitable tools.

[0029] The different phases show the simplicity of the manufacturing, transport and assembly system as well as the improvements in terms of implementation time and cost reduction. That is due to the fact that concrete prefabricated product companies are very familiar with the manufacture of these pieces and the transport requires using common vehicles like the placement and assembly. An "industrialized" process, which translates into time reduction of each of the phases and cost reduction can be created from the foregoing.

[0030] The main advantages derived from the described solution mainly result in the minimization of the risk of dififerential settlements, which will achieve the following:

• Reduced vertical vibrations in moving material.
• Increased passenger comfort and safety levels.
• Reduced infrastructure and superstructure maintenance needs.
• Improved maintenance operation planning.
• Reduced implementation times and construction cost.
• Greater control over implementation and behavior throughout service live.

[0031] Likewise, and in a more detailed manner, said advantages are reflected in:

• Cost competitiveness:

  o The lower requirements or possibilities of pretreatment and alternatives for obtaining concrete aggregates increase the availability thereof and reduce their cost, decreasing the possibility of excessive cost for transporting specific aggregates from a long distance.

  o The prefabrication of the solution entails optimizing solution implementation costs as a result of the entire industrial process.

  o The prefabricated product reduces railway superstructure maintenance needs which directly influences cost reduction. This aspect also has a direct repercussion in less vehicle deterioration.

• Time competitiveness:

  o The prefabrication of part of the components of the solution of the invention entails the arrangement thereof before starting working on the earthwork.

  ○ The simple and quick placement of the elements makes the implementation of the work easier and reduces the time for finishing the unit and therefore for complete intervention.

  ○ The prefabricated compositions entail a greater implementation control and a better maintenance work planning which assures less unforeseen circumstances.

• Quality control and safety operation competitiveness:

  o The solution contemplates suppressing materials treated with cement which makes controlling the content thereof unnecessary, simplifying quality control.

  ○ In successive inspections it can be verified that the improvement in stiffness control in these transitions causes less differential settlements which translates into vibration reduction and therefore improved passenger comfort. Similarly, fewer defects will be produced in vertical leveling reducing the risk of derailing.

  ○ These prefabricated product-based designs allow greater control over the behavior of the track during service life.

• Lower environmental costs:

  o The actual volume of the exclusively granular transitions requires a large amount of aggregates the volume of which must be measured. The presence of prefabricated elements in the new structure considerably reduces that volume of granular material reducing the degree in which the climate and the environment affect same.

  ○ The greater availability of aggregates for concrete, together with the elimination of materials treated with cement, entails the use of aggregates with higher accessibility reducing the demand for transport as well as their noise level and greenhouse gas emissions (CO, CO₂, etc.).

  ○ The reduction of maintenance operations reduces the transport of moving material which is necessary and associated with these activities contributing to a drop in emissions.

[0032] In view of the foregoing, the invention object of the present patent application provides an answer to the problems caused by the transitions in stiffness existing today by means of incorporating transition wedges which incorporate prefabricated concrete elements that replace the current transition wedges made with granular materials.

Description of the Drawings

[0033] To complement the description that is being made and for the purpose of aiding to better understand the features of the invention, a set of drawings is attached to the present specification as an integral part thereof in which the following has been depicted with an illustrative and non-limiting character:

Figure 1 shows the solution of the invention for a general case of a transition wedge object of the invention with a height of soil H above same.

Figure 2 shows a perspective view of an alternative structure isolated from the environment.

Figure 3 shows a side view of a structure alternative to that shown in Figure 1 without posts.

Preferred Embodiment of the Invention

[0034] In view of the mentioned drawings and according to the numbering used, an example of the described invention which comprises the parts and elements indicated and described in detail below can be seen therein.

[0035] Figure 1 depicts an embodiment of a structure or wedge 10 object of the present invention in which a set of prefabricated reinforced concrete slabs 1, 2 with two lengths is seen stacked on top of one another, defining in this example three heights with three rows of slabs per height. On one of the longitudinal ends thereof a set of slabs are aligned with the face of the engineering structure 3 and on the opposite longitudinal end other slabs define three steps, one per height, the length of the lower height being greater than the upper height.

[0036] As mentioned, said structure comprises two types of slabs 1, 2, having in this case a first slab 1 with a length which is of about twice the length of the second slab 2. The width of the slabs is identical and the thickness thereof is preferably also identical, the width of the slabs being at least equal to the width of the cross member in the case of railways and at least equal to the width of the carriageway or freeway in the case of highways. The slabs 1, 2 are arranged such that the joint created by the contact of two of the slabs of a row do not coincide with that created by the slabs of the top or bottom row, slabs 1, 2 with two different lengths being used in order to achieve said construction.

[0037] Therefore, the lower height of the structure has a bottom row with three aligned longer slabs 1, on which a second row of slabs is arranged, as described previously, with two longer slabs 1 in the center and two shorter slabs 2 on the sides, and three slabs are again arranged on this second row with the same configuration as the first (longer slab 1). There is arranged on this lower height a second intermediate height comprising a first bottom row with a longer slab 1 flanked by two shorter slabs 2, on which a second row with two longer slabs 1 is arranged, and a third row with the same constitution as the first bottom row of this second height is arranged on this second row. The last height, also formed by three rows of slabs, has three rows each formed by a longer slab 1.

[0038] The different rows formed by the slabs are aligned in one of their ends with the engineering structure 3, defining the different heights of the structure on the opposite end.

[0039] In this example, the slabs of the bottom row are supported on posts 5, in turn supported on the substrate 4 where the engineering structure 3 rests. Likewise, there is arranged on the structure a layer of earth 6 with a variable height and which depends on the specific application, on which there is applied a form layer 7 on which a protective sheet 8 is arranged. The railway or freeway is built on this latter sheet 8.

[0040] The dimensions of the slabs are variable, but due to the fact that they are prefabricated reinforced concrete slabs, the thickness must be at least 0.2 meters. The width of the slab depends on the length of the cross member in applications in railway and on the width of the carriageway in applications in freeways or highways.

[0041] In those cases in which the track is wider than the maximum possible width of the slab, due to design or transport reasons, mainly in the case of application in highways, the larger dimension of the slab can be arranged transverse to the track, this larger dimension becoming the width and the smaller dimension the length, unlike what has been described until now in this document where the length of the slab has been considered to be in the direction of the track. Likewise, it is possible to arrange slabs in parallel to achieve the width of the track.

[0042] Concerning the length of the slabs forming the structure, it can also be variable, but there must be at least two types of slabs with different lengths, and preferably two types of slabs where the length of one of the types 1 is about twice the length of the other type 2, in order to be able to construct the structure object of the invention. The length ratio between the different types of slabs may not be 2 to 1 and there can also be more than two types of slabs with different lengths.

[0043] An example of the dimensions of slabs for application in a railway is of a first type 1 with a length of 7.2 meters, a width of 2.5 meters and a thickness of 0.2 meters, whereas the second type of slab 2 would have a length of 3.6 meters, a width of 2.5 meters and a thickness of 0.2 meters. Likewise, it is possible to include in the structure slabs with other lengths and dimensions depending on the application thereof, even though it is suitable that the dimensions of said slabs are as big as possible since the greater said dimensions the better the slabs forming the structure will behave as a single assembly, i.e., as a whole, and when the slabs have greater dimensions a greater friction between slabs is assured due to the greater weight thereof.

[0044] Likewise, the width of the slabs would be defined by the need of covering the area where the stress is, and so that the lower the number of slabs the better the behavior of the structure as a single element or assembly will be. The minimum thickness of the slabs will also be mainly defined by the design conditions or requirements thereof.

[0045] The maximum dimensions of the slabs will be limited by the maximum weight of the slab and the length thereof since they must be transportable on land, and particularly on freeway. The transport is preferably by means of common vehicles that do not need transport permits for greater simplicity and ease, but if necessary, depending on the case, the slabs could be transported in special vehicles.

[0046] On the other hand, the dimensions of the transition structure will be demarcated in terms of width by the width of the slabs, but in terms of length and height they will be variable such that it adapts to the necessary height required in each structure in question, being suitably arranged next to the face of the engineering structure. Due to the ease of manufacturing and working, the adaptation to the height of an abutment or a crossing structure is simple and does not require any special calculation.

[0047] Figure 2 shows another construction of a structure 10 according to the present invention, also with three heights and three stacked rows per height, in which the lower height of the structure is formed by a bottom row having only two slabs, one longer slab 1 and another shorter slab 2, on which there is arranged a second row also with two slabs 1, 2 but alternated with respect to the first bottom row such that the contact areas of the slabs of the second row do not coincide with the contact areas of the slabs of the bottom row, and a third row with the same arrangement as the bottom row. On this first height there is arranged a second height of three stacked rows, each row being formed by a longer slab 1. The last height is formed by three stacked rows, each row formed by a shorter slab 2.

[0048] The third example of construction of a structure according to the present invention, shown in Figure 3, is a structure such as that depicted in Figure 1, but instead of being placed on posts 5, it rests directly on the support stratum 4 of the engineering structure 3.

[0049] An alternative to the previous solutions, not shown in the drawings, is the possibility of arranging slabs having the same width and the same length, said dimensions not having to be equal to one another. Therefore, when creating different rows and heights by placing one slab on top of another, vertical joints separating slab columns will be created.

[0050] To prevent the slabs of the structure from shifting or moving with respect to one another once installed, different solutions have been envisaged to assure the friction between the slabs. These solutions do not determine the operation of the slab as a whole so any of the solutions listed below can be valid and will be applied depending on the availability or constructive processes of the company responsible for the manufacture thereof:

• Not including any material or element to increase the friction,
• Manufacturing the slabs with at least one surface rougher than another or rough enough to assure the friction between slabs,
• Introducing an element or a material between the slabs during the working phase which increases the capacity of moving stresses from one slab to another,
• Sizing the slabs with through holes which subsequently allow sewing or attaching the slabs by means of metal bolts, injection or another system,
• Shaping the plates to allow the tongue and groove coupling in the vertical plane and/or in the horizontal plane, such that the slabs can be coupled to other slabs located above or below them as well as with other slabs located in the same plane.

[0051] The construction method of the transition structures between earthworks and engineering structures shown in the drawings and object of the present invention, comprises at least the following steps,

• Manufacturing the prefabricated reinforced concrete slabs necessary for forming the structure,
• Transporting said slabs to the site where the transition structure will be constructed,
• Placing at least two slabs on the trace of the structure, according to the final arrangement adopted for same, such that said at least two first slabs have the same width and different length, locating the shorter slab on the longer slab defining at least two rows of slabs defining at least two heights, with a longitudinal end of said two slabs aligned with the engineering structure, the width of the slabs being at least equal to the width of the track, and centering the slab longitudinally with respect to said track,
• Spreading granular material on the slabs, and
• Compacting the surface.

[0052] Like the transition structure described above, the same can have several rows and several heights, such that the rows can have more than one slab longitudinally contacting at least another slab on at least one of the two longitudinal ends, so that the longitudinally contacting areas of the slabs of a row do not coincide with the longitudinally contacting areas of the slabs of a top or bottom row.

Claims

1. A transition structure of the type used in track construction and repair for reducing the vertical stiffness variation between an earthwork and an engineering structure, characterized in that it comprises:

- at least two first prefabricated reinforced concrete slabs having the same width, one slab being located on the other slab defining at least two rows of slabs defining at least two heights, with a longitudinal end of said two slabs aligned with the engineering structure.

2. The structure according to claim 1, characterized in that the slabs have different length, the shorter slab being located on the longer slab.

3. The structure according to claim 1, characterized in that the slabs have the same length.

4. The structure according to the preceding claims, characterized in that the rows can have more than one slab longitudinally contacting at least another slab on at least one of the two longitudinal ends.

5. The structure according to the preceding claims, characterized in that it has at least two heights each height comprising at least one row.

6. The structure according to claims 2 to 5, characterized in that each height has a length different from the other heights which are defined by the length of the rows of each height, this length in turn defined by the number of slabs and the length thereof in each row, the bottom height being longer than the height immediately above.

7. The structure according to claims 1, 2 and 4 to 6, characterized in that the longitudinally contacting areas of the slabs of a row do not coincide with the longitudinally contacting areas of the slabs of a top or bottom row.

8. The structure according to claim 1, characterized in that the opposite surfaces of the slabs have different roughness.

9. The structure according to claim 1, characterized in that the slabs have at least one through hole for inserting a pin or an injection material.

10. The structure according to claim 4, characterized in that the slabs have recesses or projections on their longitudinal ends which allow the tongue and groove coupling thereof.

11. The structure according to claim 1, characterized in that the slabs have recesses or projections on their surfaces which allow the tongue and groove coupling of the slabs.

12. The structure according to claim 1, characterized in that the width of the slabs is at least equal to the width of the track.

13. The structure according to claim 1, characterized in that the width of the slab is equal to the length of a railway cross member.

14. The structure according to claim 1, characterized in that the width of the slab is equal to the width of the carriageway of the highway or freeway.

15. A construction method for constructing a transition structure of the type used in track construction and repair for reducing the vertical stiffness variation between earthworks and engineering structures, characterized in that it comprises the steps of:

- manufacturing the prefabricated reinforced concrete slabs necessary for forming the structure,

- transporting said slabs to the site where the transition structure will be constructed,

- placing at least two slabs on the trace of the engineering structure according to final arrangement adopted for same, such that said at least two first slabs have the same width, locating one slab on another slab defining at least two rows of slabs defining at least two heights, with a longitudinal end of said two slabs aligned with the engineering structure, the width of the slabs being at least equal to the width of the track, and centering the slab longitudinally with respect to said track,

- spreading granular material on the slabs, and

- compacting the surface.

16. The method according to claim 12, characterized in that the rows can have more than one slab longitudinally contacting at least another slab on at least one of the two longitudinal ends, such that the longitudinally contacting areas of the slabs of a row do not coincide with the longitudinally contacting areas of the slabs of a top or bottom row.

Drawing