JP7673356B2 - Ladder sleepers - Google Patents

Description

The present invention relates to ladder sleepers.

Ladder sleepers have been put to practical use to reduce the labor required for maintaining ballasted tracks. Ladder sleepers are ladder-shaped sleepers in which long vertical beams made of prestressed concrete (PC) are placed along the rails and a pair of vertical beams are connected by steel joints (see, for example, Patent Document 1).

Patent No. 3217932

When a railway vehicle travels over a rail joint, an impact load acts on the ballast. When a ladder sleeper is placed over a rail joint, the ladder sleeper distributes the impact load and transmits it to the ballast. The force transmitted to the ballast via the ladder sleeper is smaller than the force transmitted to the ballast via a typical cross sleeper. However, there is a need to further reduce the force transmitted to the ballast.

The problem that this invention aims to solve is to provide a ladder sleeper that can reduce the force transmitted to the ballast.

The ladder sleeper of the present invention has a pair of longitudinal beams, an end beam, and an intermediate beam. The pair of longitudinal beams can be positioned below a pair of rails extending in a first direction, and extend in the first direction. The end beams are positioned near the ends of the pair of longitudinal beams in the first direction, and extend in a second direction that intersects the up-down direction and the first direction. The intermediate beam is positioned closer to the center of the pair of longitudinal beams than the end beams in the first direction, extends in the second direction, and is made of concrete.

In the first direction, the ladder sleeper is positioned near the center at the rail joint. When a railway vehicle travels over the rail joint, an impact load acts near the center of the ladder sleeper. The intermediate beam is positioned closer to the center of the pair of longitudinal beams than the end beams in the first direction. The impact load is dispersed by the concrete intermediate beam and transmitted to the ballast. This reduces the force transmitted to the ballast.

The ladder sleeper has a plurality of mounting portions. The mounting portions are formed on a pair of longitudinal beams aligned in a first direction and are used to attach a rail fastening device. The mounting portions include a first mounting portion located adjacent to a center portion of the pair of longitudinal beams in the first direction. The intermediate beam may be disposed at the position of the first mounting portion in the first direction.

In the first direction, the position of the first mounting part of the ladder sleeper is located at the position of the rail joint. When a railway vehicle travels over the rail joint, an impact load acts on the first mounting part of the ladder sleeper. The intermediate beam is located at the position of the first mounting part in the first direction. The impact load is sufficiently dispersed by the intermediate beam and transmitted to the ballast. This sufficiently reduces the force transmitted to the ballast.

The ladder sleeper has a plurality of mounting portions. The plurality of mounting portions are formed on a pair of vertical beams aligned in a first direction and are used to attach a rail fastening device. The plurality of mounting portions include a pair of second mounting portions located on both sides of the center of the pair of vertical beams in the first direction. The intermediate beam may be disposed at the position of the pair of second mounting portions in the first direction.

In the first direction, the center of the pair of second mounting parts of the ladder sleeper is positioned at the position of the rail joint. When a railway vehicle travels over the rail joint, an impact load acts on the pair of second mounting parts of the ladder sleeper. The intermediate beam is positioned at the position of the pair of second mounting parts in the first direction. The impact load is sufficiently distributed by the intermediate beam and transmitted to the ballast. This sufficiently reduces the force transmitted to the ballast.

The intermediate beam may be a double-fixed beam that is fixed to both of the pair of longitudinal beams.
This allows the shock load to be sufficiently distributed and transmitted to the ballast, and therefore the force transmitted to the ballast is sufficiently mitigated.

The intermediate beam may be a cantilever beam fixed to only one of the pair of longitudinal beams, and may be disposed on only one of the inside and outside of the pair of longitudinal beams in the second direction.
When the intermediate beam is a cantilever beam, it can be made of a general reinforced concrete structure. When the intermediate beam is a fixed beam at both ends, tension needs to be applied to the PC steel rod to prevent cracks, but by making it a reinforced concrete structure, the tensioning work can be omitted. This improves the productivity of ladder sleepers. When the intermediate beam is arranged only on the inside of a pair of longitudinal beams, the ladder sleeper does not expand in the second direction. When the intermediate beam is arranged only on the outside of a pair of longitudinal beams, the tamping work of the ballast on the inside of the pair of longitudinal beams becomes easier.

The intermediate beam is a cantilever beam fixed to only one of the pair of longitudinal beams, and may be disposed on both the inside and outside of the pair of longitudinal beams in the second direction.
This increases the contact area between the intermediate beam and the ballast bed. Impact loads are sufficiently distributed and transmitted to the ballast. Therefore, the force transmitted to the ballast is sufficiently mitigated.

The intermediate beam of the present invention is disposed closer to the center of the pair of longitudinal beams than the end beams in the first direction, extends in the second direction, and is made of concrete. This sufficiently reduces the force transmitted to the ballast.

FIG. 1 is a perspective view of a ballast ladder track using the ladder sleeper of the first embodiment. FIG. 2 is a plan view of the ladder sleeper of the first embodiment. FIG. 11 is a plan view of the ladder sleeper of the second embodiment. FIG. 13 is a plan view of a ladder sleeper according to a first modified example of the second embodiment. FIG. 13 is a plan view of a ladder sleeper according to a second modified example of the second embodiment. FIG. 11 is a perspective view of a ballast ladder track using the ladder sleeper of the third embodiment. FIG. 11 is a plan view of the ladder sleeper of the third embodiment. FIG. 13 is a plan view of the ladder sleeper of the fourth embodiment.

Hereinafter, a ladder sleeper according to an embodiment will be described with reference to the drawings.
First Embodiment
Fig. 1 is a perspective view of a ballast ladder track using ladder sleepers of the first embodiment. The ballast ladder track 1 is a track in which ladder sleepers 10 are laid on a ballast track bed 3. The ladder sleepers 10 are ladder-shaped vertical sleepers arranged directly below the rails 5. The rails 5 are fixed to the ladder sleepers 10 by fastening devices 6.

In this application, the Z direction, X direction, and Y direction of the Cartesian coordinate system are defined as follows. The Z direction is the vertical direction, and the +Z direction is the upward direction. The X direction (first direction) is the direction in which the rail 5 and ladder sleeper 10 extend. The Y direction (second direction) is the direction perpendicular to the Z direction and the X direction. The X direction and the Y direction are horizontal directions. In the X direction and the Y direction, the side closer to the center of the ladder sleeper 10 may be called the inside, and the side farther from the center may be called the outside.

Figure 2 is a plan view of the ladder sleeper of the first embodiment. The ladder sleeper 10 has a pair of longitudinal beams 12, a joint member 14, and an end closure beam (end beam) 18. The ladder sleeper 10 is formed in a ladder shape by rigidly connecting the pair of longitudinal beams 12 with multiple joint members 14.

The vertical beams 12 extend in the X direction. The vertical beams 12 are made of prestressed concrete (PC). PC is concrete prestressed by PC steel. A pair of vertical beams 12 are arranged parallel to each other with a gap in the Y direction. Mounting portions 16 used to attach fastening devices 6 (see FIG. 1) are formed on the upper surfaces of the pair of vertical beams 12. For example, the mounting portions 16 are mounting holes into which bolts are inserted. The mounting holes are formed at positions corresponding to both sides of the rail 5 (see FIG. 1) in the Y direction. A plurality of mounting portions 16 are arranged in a row at approximately equal intervals along the X direction. The number of fastening devices 6 and mounting portions 16 in the X direction is not limited to the examples in the figures.

The joint members 14 are formed from steel members such as steel pipes and steel bars. For example, the joint members 14 are formed from straight deformed steel bars extending in the Y direction. The joint members 14 are arranged across a pair of vertical beams 12. Both ends of the joint members 14 in the Y direction are embedded inside the pair of vertical beams 12. A plurality of joint members 14 are arranged in parallel with intervals in the X direction. The joint members 14 may be formed from steel pipes filled with mortar.

The end closure beam 18 is positioned near the X-direction ends of the pair of longitudinal beams 12. The end closure beam 18 extends in the Y-direction. The end closure beam 18 is a fixed beam fixed at both ends to both of the pair of longitudinal beams 12. The basic structure of the end closure beam 18 is a reinforced concrete structure. However, to prevent cracks in the end closure beam 18, prestress (post-tensioning) is additionally applied by unbonded PC steel material. The end closure beam 18 increases the contact area with the ballast track bed 3. The end closure beam 18 prevents the X-direction ends of the pair of longitudinal beams 12 from sinking into the ballast track bed 3.

The ladder sleeper 10 has an intermediate beam 20. The intermediate beam 20 is positioned in the X direction closer to the center C of the pair of vertical beams 12 than the end closure beams 18. The intermediate beam 20 extends in the Y direction. The intermediate beam 20 is made of concrete.

The intermediate beam 20 in the first embodiment is an intermediate closure beam 21. The intermediate closure beam 21 is a fixed beam at both ends that is fixed to both of the pair of longitudinal beams 12. The width of the intermediate closure beam 21 in the X direction is equal to that of the end closure beam 18. As a result, the intermediate closure beam 21 does not interfere with the tamping work of the ballast on the inside of the pair of longitudinal beams 12.

The basic structure of the intermediate closure beam 21 is a reinforced concrete structure, similar to that of the end closure beam 18. In order to prevent cracks in the intermediate closure beam 21, prestress (post-tensioning) is provided by unbonded PC steel. The construction method for the intermediate closure beam 21 is as follows. First, the formwork for the area is assembled and rebar is placed. Next, PC steel with an unbonded surface is placed in the specified position. Next, the PC steel is tensioned primarily to remove slack. Next, concrete is poured and hardened to apply prestress to the vertical beam 12. Next, the PC steel is tensioned secondarily to apply prestress to the intermediate closure beam 21.

The aforementioned multiple mounting portions 16 include a first mounting portion 16a. The first mounting portion 16a is located next to the center portion C of the pair of vertical beams 12 in the X direction. The intermediate closure beam 21 is disposed at the position of the first mounting portion 16a in the X direction.

As shown in FIG. 1, the rail 5 has a joint S. A joint plate 7 is attached to the Y-direction side of the rail 5, straddling the joint S. In the X-direction, the vicinity of the center of the ladder sleeper 10 is positioned at the position of the joint S. As shown in FIG. 2, the first mounting portion 16a and the intermediate closure beam 21 of the ladder sleeper 10 are positioned at the position of the joint S in the X-direction.

The fastening device 6 attached to the first mounting portion 16a fastens the ends of the rail 5 on both sides of the joint S in the X direction to the vertical beam 12. Therefore, the first mounting portion 16a has mounting holes on both sides of the X direction at the position corresponding to the joint S. As a result, the first mounting portion 16a has two mounting holes at positions corresponding to both sides of the rail 5 in the Y direction.

The intermediate closure beam 21 supports the joint S at the same position as the joint S in the X direction. The joint S becomes a support joint that is supported by the so-called support joint method. The ladder sleeper 10 of the first embodiment is used as a support joint.

In the X direction, the vicinity of the center C of the ladder sleeper 10 is positioned at the joint S of the rail 5. When a railway vehicle travels over the joint S of the rail 5, an impact load acts near the center C of the ladder sleeper 10. The intermediate closure beam 21, which is the intermediate beam 20, is positioned closer to the center C of the pair of longitudinal beams 12 in the X direction than the end closure beams 18. The impact load is dispersed by the intermediate closure beam 21 and transmitted to the ballast. This reduces the force transmitted to the ballast.

In the X direction, the position of the first mounting portion 16a of the ladder sleeper 10 is located at the position of the joint S of the rail 5. When a railway vehicle travels over the joint S of the rail 5, an impact load acts on the first mounting portion 16a of the ladder sleeper 10. The intermediate closure beam 21 is located at the position of the first mounting portion 16a in the X direction. The impact load is sufficiently dispersed by the intermediate closure beam 21 and transmitted to the ballast. This sufficiently reduces the force transmitted to the ballast. As a result, deterioration such as ballast wear and subsidence of the ballast track bed 3 can be suppressed.

The inventors of the present application performed a numerical analysis (simulation) of the pressure on the underside of the ladder sleeper 10 when an impact load acts on the first mounting portion 16a. Compared to when there is no intermediate closure beam 21, when there is an intermediate closure beam 21, the maximum pressure on the underside of the ladder sleeper 10 is reduced by about 10%. It was confirmed that the force transmitted to the ballast is sufficiently mitigated by the intermediate closure beam 21.

As described above, the width in the X direction of the intermediate closure beam 21 in the first embodiment is equal to that of the end closure beam 18. In contrast, the width in the X direction of the intermediate closure beam 21 may be greater than that of the end closure beam 18. This increases the contact area between the intermediate closure beam 21 and the ballast track bed 3, and sufficiently reduces the force transmitted to the ballast.

Second Embodiment
3 is a plan view of the ladder sleeper of the second embodiment. The ladder sleeper 10 of the second embodiment differs from the first embodiment in that the intermediate beam 20 is an intermediate protrusion 22. Description of the second embodiment in the same parts as the first embodiment may be omitted.

The intermediate beam 20 in the second embodiment is an intermediate protrusion 22. The intermediate protrusion 22 is a cantilever beam fixed to only one of the pair of vertical beams 12. The intermediate protrusion 22 is disposed only on the inner side of the pair of vertical beams 12 in the Y direction. The intermediate protrusion 22 protrudes on the inner side of the pair of vertical beams 12 in the Y direction. The intermediate protrusion 22 protrudes from each of the pair of vertical beams 12 to form a pair of intermediate protrusions 22.

The intermediate protrusion 22 protrudes from the vertical beam 12 in the Y direction by a protrusion amount 22y. Although the intermediate protrusion 22 is a cantilever beam, cracks are unlikely to occur because the protrusion amount 22y is small. While the end closure beam 18 is prestressed, the intermediate protrusion 22 is a general reinforced concrete (RC) structure. The manufacturing process of the intermediate protrusion 22 does not require the work of primary and secondary tensioning of the PC steel material. This improves the productivity of the ladder sleeper 10.

The width 22x in the X direction of the intermediate protrusion 22 is greater than the width in the X direction of the intermediate closure beam 21 of the first embodiment. The product of the protrusion amount 22y and the width 22x is the contact area between the intermediate protrusion 22 and the ballast track bed 3. The sum of the contact areas of a pair of intermediate protrusions 22 is equal to the contact area of the intermediate closure beam 21 of the first embodiment.

The intermediate protrusion 22 is disposed at the position of the first mounting portion 16a in the X direction. The first mounting portion 16a and the intermediate protrusion 22 of the ladder sleeper 10 are disposed at the position of the joint S. That is, the ladder sleeper 10 of the second embodiment is used for a support joint. When a railway vehicle travels over the joint S of the rail 5, an impact load acts on the first mounting portion 16a of the ladder sleeper 10. The impact load is sufficiently dispersed by the intermediate protrusion 22 and transmitted to the ballast. This sufficiently reduces the force transmitted to the ballast.

The intermediate protrusions 22 are positioned only on the inside of the pair of longitudinal beams 12 in the Y direction. Since the intermediate protrusions 22 are not positioned on the outside of the pair of longitudinal beams 12 in the Y direction, the ladder sleeper 10 does not expand in the Y direction.

Figure 4 is a plan view of a ladder sleeper of a first modified example of the second embodiment. The ladder sleeper 10 of the first modified example differs from the second embodiment in that the intermediate projections 23 are arranged only on the outside of a pair of longitudinal beams 12. Descriptions of the first modified example in the same parts as the second embodiment may be omitted.

The intermediate protrusion 23 protrudes outward in the Y direction from the pair of longitudinal beams 12. The amount of protrusion in the Y direction and the width in the X direction of the intermediate protrusion 23 are the same as those of the intermediate protrusion 22 in the second embodiment. The intermediate protrusion 23 is a general reinforced concrete (RC) structure. The intermediate protrusion 23 is disposed at the position of the first mounting portion 16a in the X direction. The ladder sleeper 10 of the first modified example is used for a support joint. The intermediate protrusion 23 sufficiently distributes the impact load and transmits it to the ballast. Therefore, the force transmitted to the ballast is sufficiently mitigated.

The intermediate protrusions 23 of the first modified example are arranged only on the outside of the inside and outside of the pair of longitudinal beams 12 in the Y direction. This makes it easier to compact the ballast on the inside of the pair of longitudinal beams 12 in the Y direction.

Figure 5 is a plan view of a ladder sleeper of a second modified example of the second embodiment. The ladder sleeper 10 of the second modified example differs from the second embodiment in that the intermediate projections 22, 23 are arranged on both the inside and outside of a pair of longitudinal beams 12. Descriptions of the second modified example in the parts that are similar to the second embodiment or its first modified example may be omitted.

The intermediate protrusion 22 protrudes inward in the Y direction of the pair of longitudinal beams 12. The intermediate protrusion 23 protrudes outward in the Y direction of the pair of longitudinal beams 12. The protrusion amount in the Y direction and the width in the X direction of the intermediate protrusions 22, 23 are the same as those in the second embodiment and the first modified example. The sum of the contact areas between the intermediate protrusions 22, 23 and the ballast track bed 3 is greater than the contact area between the intermediate closing beam 21 and the ballast track bed 3 in the first embodiment.

The intermediate protrusions 22, 23 of the second modified example are arranged on both the inside and outside of the pair of longitudinal beams 12 in the Y direction. This increases the contact area between the intermediate protrusions 22, 23 and the ballast track bed 3. Impact loads are sufficiently distributed and transmitted to the ballast. Therefore, the force transmitted to the ballast is sufficiently mitigated.

Third Embodiment
Fig. 6 is a perspective view of a ballast ladder track using the ladder sleeper of the third embodiment. Fig. 7 is a plan view of the ladder sleeper of the third embodiment. The ladder sleeper 10 of the third embodiment differs from the first embodiment in that it is used at a hanging joint. The description of the third embodiment in the parts similar to those of the first embodiment may be omitted.

As shown in FIG. 7, the intermediate beam 20 is positioned in the X direction closer to the center C of the pair of vertical beams 12 than the end closure beams 18. The intermediate beam 20 extends in the Y direction. The intermediate beam 20 in the third embodiment is a concrete intermediate closure beam 21 similar to the first embodiment.

The multiple mounting portions 16 include a pair of second mounting portions 16b. The pair of second mounting portions 16b are located on either side of the central portion C of the pair of vertical beams 12 in the X direction. The intermediate closure beam 21 is disposed at the position of the pair of second mounting portions 16b in the X direction. The intermediate closure beam 21 is disposed at each position of the pair of second mounting portions 16b to form a pair of intermediate closure beams 21.

As shown in FIG. 6, the rail 5 has a joint S. A joint plate 7 is attached to the Y-direction side of the rail 5, spanning the joint S. In the X direction, the center of the ladder sleeper 10 is positioned at the position of the joint S. As shown in FIG. 7, in the X direction, the pair of second mounting portions 16b of the ladder sleeper 10 and the center C of the pair of intermediate closing beams 21 are positioned at the position of the joint S.

The fastening device 6 attached to the second mounting portion 16b fixes the rail 5 to the ladder sleeper 10 at a position away from the joint S in the X direction. Therefore, the second mounting portion 16b, like the other mounting portions 16, has one mounting hole on each side of the rail 5 in the Y direction.

The intermediate closure beam 21 supports the joint S at the positions of the fastening devices 6 on both sides of the joint S in the X direction. The joint S is a lap joint supported by the so-called lap joint method. The ladder sleeper 10 of the third embodiment is used for a lap joint.

In the X direction, the center of the ladder sleeper 10 is positioned at the joint S of the rail 5. When a railway vehicle travels over the joint S of the rail 5, an impact load acts on the center C of the ladder sleeper 10. The intermediate closure beam 21, which is the intermediate beam 20, is positioned closer to the center C of the pair of longitudinal beams 12 in the X direction than the end closure beams 18. The impact load is dispersed by the intermediate closure beam 21 and transmitted to the ballast. This reduces the force transmitted to the ballast.

In the X direction, the center C of the pair of second mounting portions 16b of the ladder sleeper 10 is located at the position of the joint S. When a railway vehicle travels over the joint S of the rail 5, an impact load acts on the pair of second mounting portions 16b of the ladder sleeper 10. The intermediate closure beam 21 is located at the position of the pair of second mounting portions 16b in the X direction. The impact load is sufficiently dispersed by the intermediate closure beam 21 and transmitted to the ballast. This sufficiently reduces the force transmitted to the ballast. As a result, deterioration such as wear and settlement of the ballast can be suppressed.

Fourth Embodiment
8 is a plan view of a ladder sleeper of the fourth embodiment. The ladder sleeper 10 of the fourth embodiment differs from the third embodiment in that the intermediate beam 20 is an intermediate protrusion 22. Description of the fourth embodiment in the same parts as the third embodiment may be omitted.

The intermediate beam 20 of the fourth embodiment has an intermediate protrusion 22 similar to that of the second embodiment.
The intermediate protrusion 22 is disposed at the position of the pair of second mounting portions 16b in the X direction. In the X direction, the center of the pair of second mounting portions 16b of the ladder sleeper 10 is disposed at the position of the joint S. That is, the ladder sleeper 10 of the fourth embodiment is used for a hanging joint. When a railway vehicle travels over the joint S of the rail 5, an impact load acts on the pair of second mounting portions 16b of the ladder sleeper 10. The impact load is sufficiently dispersed by the intermediate protrusion 22 and transmitted to the ballast. This satisfactorily reduces the force transmitted to the ballast.

In the fourth embodiment, the intermediate protrusion 22 is arranged only on the inner side of the pair of longitudinal beams 12 in the Y direction, as in the second embodiment. Instead of the intermediate protrusion 22, an intermediate protrusion 23 similar to the first modified example of the second embodiment may be used. The intermediate protrusion 23 is arranged only on the outer side of the pair of longitudinal beams 12 in the Y direction, as in the second modified example of the second embodiment. The intermediate protrusion 22 and the intermediate protrusion 23 may be used simultaneously.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configurations are not limited to these embodiments, and include modifications, combinations, deletions, etc. of the configurations within the scope that does not depart from the gist of the present invention.

The intermediate beam 20 in the embodiment is disposed at the position of the first mounting portion 16a or the pair of second mounting portions 16b in the X direction. Alternatively, the intermediate beam 20 may be disposed between adjacent mounting portions 16. Even in this case, the intermediate beam 20 is disposed closer to the center C of the pair of vertical beams 12 in the X direction than the end closure beams 18. This reduces the force transmitted to the ballast.

The end beam in this embodiment is an end closure beam 18, which is a beam with fixed ends that is fixed to both of the pair of longitudinal beams 12. In contrast, the end beam may be an end protrusion similar to the intermediate protrusions 22, 23. The end protrusion is a cantilever beam that is fixed to only one of the pair of longitudinal beams 12. The end protrusion is a typical reinforced concrete structure. This improves the productivity of ladder sleepers.

C...center, S...joint, 5...rail, 6...fastening device, 10...ladder sleeper, 12...longitudinal beam, 16...mounting portion, 16a...first mounting portion, 16b...second mounting portion, 18...end closure beam (end beam), 20...intermediate beam, 21...intermediate closure beam (intermediate beam), 22...intermediate protrusion (intermediate beam), 23...intermediate protrusion (intermediate beam).

Claims (5)

A pair of longitudinal beams extending in a first direction and disposed below a pair of rails extending in the first direction;
an end beam disposed near the ends of the pair of vertical beams in the first direction and extending in a second direction intersecting the up-down direction and the first direction;
An intermediate beam made of concrete arranged at a position closer to the center of the pair of vertical beams than the end beams in the first direction and extending in the second direction;
a plurality of mounting portions formed on the pair of longitudinal beams aligned in the first direction and used for mounting a fastening device of the rail ;
The plurality of mounting portions include a first mounting portion that is not formed in a central portion of the pair of longitudinal beams in the first direction and is located adjacent to the central portion of the pair of longitudinal beams in the first direction,
The first mounting portion has mounting holes on both sides in the first direction at a position corresponding to the joint of the rail in the first direction, for mounting the ends of the rail on both sides of the joint in the first direction to the pair of vertical beams,
The intermediate beam is disposed at a position of the first mounting portion in the first direction.
Ladder sleepers. A pair of longitudinal beams extending in a first direction and disposed below a pair of rails extending in the first direction;
an end beam disposed near the ends of the pair of vertical beams in the first direction and extending in a second direction intersecting the up-down direction and the first direction;
An intermediate beam made of concrete arranged at a position closer to the center of the pair of vertical beams than the end beams in the first direction and extending in the second direction;
a plurality of mounting portions formed on the pair of longitudinal beams aligned in the first direction and used for fastening the rail;
The plurality of mounting portions include a pair of second mounting portions that are not formed in the central portions of the pair of vertical beams in the first direction and are located adjacent to both sides of the central portions of the pair of vertical beams in the first direction,
the pair of second mounting portions have mounting holes for mounting the rail to the pair of vertical beams at positions spaced in the first direction from central portions of the pair of vertical beams where joints of the rail are located in the first direction,
The intermediate beam is disposed at a position of the pair of second mounting portions in the first direction.
Ladder sleepers. The intermediate beam is a double-fixed beam fixed to both of the pair of vertical beams.
3. A ladder sleeper as claimed in claim 1 or 2 . The intermediate beam is a cantilever beam fixed to only one of the pair of vertical beams and is disposed on only one of the inner side and the outer side of the pair of vertical beams in the second direction.
3. A ladder sleeper as claimed in claim 1 or 2 . The intermediate beam is a cantilever beam fixed to only one of the pair of longitudinal beams, and is disposed on both the inside and the outside of the pair of longitudinal beams in the second direction.
3. A ladder sleeper as claimed in claim 1 or 2 .

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