Synthetic Box Culvert

Abstract

The present invention provides a composite box culvert capable of improving shear strength. [Solution] The composite box culvert according to the present invention comprises a cylindrical concrete structure formed around an axis and an outer shell steel plate formed to cover the outer circumferential surface of the concrete structure, wherein the composite box culvert has a rectangular cross-section perpendicular to the axis, and the outer shell steel plate has an outer circumferential covering portion that covers the entire outer circumferential surface of the concrete structure and a plurality of protruding portions that protrude from the inner circumferential surface of the outer circumferential covering portion and are embedded in the concrete structure, and extend from one end to the other end of the concrete structure along the axial direction.

Description

Technical Field

[0001] The present invention relates to a composite box culvert.

Background Art

[0002] A composite box culvert is a tubular structure with a rectangular cross-section. When embedded underground, for example, it forms conduits for electric wires, gas pipes, water supply pipes, sewer pipes, communication wiring and the like. It is known that since composite box culverts exhibit high bending strength, they are less likely to be damaged by earth pressure even when buried at relatively deep positions underground.

[0003] Incidentally, composite box culverts are required to exhibit excellent strength resistance against shear generated during earthquakes. Conventionally, in order to improve the shear strength of composite box culverts, shear reinforcing bars such as dowel rebars, loop bars and stirrup bars have been installed (for example, Patent Documents 1 and 2).

Prior Art Literature

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problem to be Solved by the Invention

[0005] However, since shear reinforcing bars need to be joined so as to connect the inner and outer steel members (rebars, steel plates, etc.) one by one, the installation work is extremely complicated. Therefore, development of new technology is demanded to improve the shear strength of composite box culverts.

[0006] In view of the current situation, the present invention aims to provide a composite box culvert capable of improving shear strength. [Means for solving the problem]

[0007] The composite box culvert according to the present invention comprises a cylindrical concrete structure formed around an axis and an outer shell steel plate formed to cover the outer circumferential surface of the concrete structure, wherein the composite box culvert has a rectangular cross-section perpendicular to the axis, and the outer shell steel plate has an outer circumferential covering portion that covers the entire outer circumferential surface of the concrete structure and a plurality of protruding portions that protrude from the inner circumferential surface of the outer circumferential covering portion and are embedded in the concrete structure, and extend from one end to the other end of the concrete structure along the axial direction.

[0008] The composite box culvert can improve its shear strength by having the outer steel plate have multiple protruding sections.

[0009] In the composite box culvert according to the present invention, the protruding portion may be composed of a plate-like member, and the surface of the plate-like member in the thickness direction may be in contact with the outer peripheral covering portion.

[0010] With this configuration, the composite box culvert can increase the contact area between the protruding portion and the concrete structure, thereby improving the adhesion force of the concrete structure to the protruding portion.

[0011] In the composite box culvert according to the present invention, the protruding portions may be arranged at substantially equal intervals on at least one of the four surfaces constituting the outer peripheral covering portion.

[0012] The aforementioned composite box culvert can achieve improved shear strength through this configuration.

[0013] In the composite box culvert according to the present invention, the ratio of the length of the protruding ridge in the protruding direction to the thickness of the concrete structure may be 0.03 or more and 1 or less.

[0014] With this configuration, the composite box culvert can further improve shear strength.

[0015] In the composite box culvert according to the present invention, the ratio of the thickness of the protruding ridge to the thickness of the outer peripheral covering portion may be 0.25 or more and 4.00 or less.

[0016] With this configuration, the composite box culvert can further improve shear strength.

[0017] In the composite box culvert according to the present invention, a plurality of main reinforcing bars extending along a direction perpendicular to the axis and arranged around the axis are embedded in the concrete structure, and the main reinforcing bars may be joined to the protruding ridges.

[0018] With this configuration, the composite box culvert can further improve shear strength. Effects of the Invention

[0019] As described above, according to the present invention, a composite box culvert capable of improving shear strength can be provided. Brief Description of Drawings

[0020] [Figure 1] Figure 1 is a perspective view of the composite box culvert 1 according to the present embodiment. [Figure 2] Figure 2 is a cross-sectional view in a direction perpendicular to the axis L of the composite box culvert 1 shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view taken along line III-III of the composite box culvert 1 shown in Figure 2. Mode for Carrying Out the Invention

[0021] Hereinafter, a composite box culvert 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and repeated description thereof will be omitted. FIG. 1 is a perspective view of the composite box culvert 1 according to the present embodiment. FIG. 2 is a cross-sectional view in a direction perpendicular to the axis L of the composite box culvert 1 shown in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III of the composite box culvert 1 shown in FIG. 2.

[0022] The composite box culvert 1 according to the present embodiment includes a cylindrical concrete structure 2 formed around an axis L extending in one direction, and an outer shell steel plate 3 formed to cover an outer circumferential surface of the concrete structure 2. The composite box culvert 1 forms an internal space by an inner circumferential surface of the composite box culvert 1, and is configured to be capable of accommodating electric wires, gas pipes, water supply pipes, sewer pipes, communication wires, and the like in the internal space.

[0023] The composite box culvert 1 has a rectangular cross-section perpendicular to the axis L, more specifically, a substantially square cross-section. The size of the composite box culvert 1 is not particularly limited. A length of the composite box culvert 1 along the axis L can be, for example, 300 mm or more and 2000 mm or less. A distance between opposing outer circumferential surfaces of the cross-section perpendicular to the axis L of the composite box culvert 1 can be, for example, 900 mm or more and 3600 mm or less, and a distance between opposing inner circumferential surfaces of the cross-section perpendicular to the axis L can be, for example, 600 mm or more and 3100 mm or less. In the cross-section perpendicular to the axis L, corners of the outer circumferential surface and the inner circumferential surface of the composite box culvert 1 form an R shape with a predetermined curvature.

[0024] The concrete constituting the concrete structure 2 may be, for example, a composition containing cement, coarse aggregate, and fine aggregate mixed with water. Alternatively, the composition may contain blast furnace slag powder, fly ash, etc., instead of cement. The cement, coarse aggregate, and fine aggregate are not particularly limited, and conventionally known materials can be used. Furthermore, the cement composition may contain other materials such as fibrous materials, admixtures, and other admixtures.

[0025] The cement used is not particularly limited, and various types of cement available on the market can be used. Specifically, one of the following can be used, selected from the group consisting of various Portland cements such as ordinary Portland cement and rapid-hardening Portland cement, various mixed cements of blast furnace cement, silica cement and fly ash cement, or white Portland cement, alumina cement and ultrafast-setting cements such as calcium aluminate, calcium sulfoaluminate and calcium fluoroaluminate, or a mixture of several of these.

[0026] The coarse aggregate can be of a size such that 85% or more by mass does not pass through a 5 mm sieve. Specifically, examples of coarse aggregate include crushed sandstone, gravel (river gravel), natural lightweight coarse aggregate (perlite, vermiculite, etc.), by-product lightweight coarse aggregate, artificial lightweight coarse aggregate, recycled aggregate, etc. The coarse aggregate content is not particularly limited; for example, it may be 100% to 300% by mass relative to the cement, or 100% to 200% by mass.

[0027] The fine aggregate used can be of a size that passes through all 10 mm sieves and through 5 mm sieves, with at least 85% passing through a 5 mm sieve. Specifically, examples of fine aggregate include natural sands such as mountain sand, river sand, land sand, and sea sand, as well as crushed sand (more specifically, crushed limestone sand, etc.) formed by artificially crushing sandstone, limestone, etc. The fine aggregate content is not particularly limited; for example, it may be 100% to 300% by mass relative to the cement, or 150% to 250% by mass.

[0028] The sizes of the coarse and fine aggregates mentioned above are measured according to the aggregate sieving test method in accordance with JIS A 1102, and represent the sieve sizes specified in JIS Z 8801-1.

[0029] Furthermore, other materials included in the cement composition are not particularly limited and include, for example, fibrous materials (glass fibers, steel fibers, vinylon fibers, aramid fibers, polypropylene fibers, carbon fibers, etc.), admixtures (blast furnace slag, fly ash, silica fume, expansive agents, etc.), and admixtures (water-reducing agents, thickeners, defoaming agents, etc.).

[0030] The water used is not particularly limited, and any water known to be suitable for mixing can be used. Furthermore, the water may also contain admixtures such as water-reducing agents used when mixing mortar or concrete, polymer dispersion liquids, shrinkage reducing agents, setting regulators, etc.

[0031] The thickness of the concrete structure 2 is not particularly limited. If the size of the composite box culvert 1 is 3600 mm, the thickness of the concrete structure 2 may be, for example, 220 mm to 400 mm, or 240 mm to 300 mm. If the size of the composite box culvert 1 is 900 mm, the thickness of the concrete structure 2 may be, for example, 70 mm to 200 mm, or 130 mm to 150 mm.

[0032] The outer steel plate 3 has an outer covering portion 31 that covers the entire outer surface of the concrete structure 2, and a plurality of protruding portions 32 that protrude from the inner surface of the outer covering portion 31 and are embedded in the concrete structure 2, and extend from one end to the other end of the concrete structure 2 along the axis L direction.

[0033] The outer periphery covering portion 31 is composed of four surfaces, specifically an upper surface 31a, a bottom surface 31b, and two side surfaces 31c and d. On each surface, eight protrusions 32 are arranged at approximately equal intervals. The spacing of the protrusions 32 is not particularly limited. If the size of the composite box culvert 1 is 3600 mm, the spacing of the protrusions 32 may be, for example, 150 mm to 450 mm, or 200 mm to 350 mm. If the size of the composite box culvert 1 is 900 mm, the spacing of the protrusions 32 may be, for example, 150 mm to 350 mm, or 200 mm to 250 mm. Note that the spacing of the protrusions 32 is the distance between the centers of the protrusions 32 in the thickness direction. The outer periphery covering portion 31 and the protrusions 32 may be formed integrally, or they may be formed separately and then joined together.

[0034] The outer perimeter covering portion 31 is formed entirely from a metal plate. The thickness of the outer perimeter covering portion 31 is not particularly limited. If the size of the composite box culvert 1 is 3600 mm, the thickness of the outer perimeter covering portion 31 may be, for example, 6.0 mm to 22 mm, or 9.0 mm to 19 mm. If the size of the composite box culvert 1 is 900 mm, the thickness of the outer perimeter covering portion 31 may be, for example, 4.5 mm to 22 mm, or 6.0 mm to 16 mm. Furthermore, the metal constituting the outer perimeter covering portion 31 is not particularly limited, and examples include JIS G 3101 "Rolled steel for general structural use", JIS G 3106 "Rolled steel for welded steel", JIS G 4305 "Cold-rolled stainless steel sheets and strips", or steel plates whose mechanical properties are equivalent to these standard values.

[0035] The protruding portion 32 is made of a plate-like member, and the surface of the plate-like member in the thickness direction is in contact with the outer peripheral covering portion 31. The thickness and length of the protruding portion 32 are not particularly limited. When the size of the composite box culvert 1 is 3600 mm, the thickness of the protruding portion 32 may be, for example, 6.0 mm or more and 22 mm or 9.0 mm or more and 19 mm or less. When the size of the composite box culvert 1 is 900 mm, the thickness of the protruding portion 32 may be, for example, 4.5 mm or more and 22 mm or 6.0 mm or more and 16 mm or less. Also, when the size of the composite box culvert 1 is 3600 mm, the length of the protruding portion 32 in the protruding direction may be, for example, 150 mm or more and 350 mm or 200 mm or more and 300 mm or less. If the size of the composite box culvert 1 is 900 mm, the length of the protruding portion 32 in the protruding direction may be, for example, 50 mm or more and 150 mm or less, or 70 mm or more and 100 mm or less.

[0036] The protruding portion 32 is formed entirely from a metal plate. The metal used to constitute the protruding portion 32 is not particularly limited, and the same metal as that used for the outer peripheral covering portion 31 can be used.

[0037] From the viewpoint of improving shear strength, the ratio of the length of the protruding portion 32 in the protruding direction to the thickness of the concrete structure 2 is preferably 0.03 or more and 1 or less, and more preferably 0.5 or more and 0.8 or less.

[0038] From the viewpoint of improving shear strength, the ratio of the thickness of the protruding portion 32 to the thickness of the outer peripheral covering portion 31 is preferably 0.25 or more and 4.00 or less, and more preferably 1.00 or more and 4.00 or less.

[0039] The composite box culvert 1 has a reduced-diameter portion 3' at one end in the direction of the axis L, where the outer surface of the outer shell steel plate 3 is reduced in diameter. The composite box culvert 1 also has a tubular projection 33 at the other end in the direction of the axis L, which protrudes from the end of the outer covering portion 31 in the direction in which the axis L extends. Multiple composite box culverts 1 can be connected along the axis L to form a pipeline by inserting the reduced-diameter portion 3' at one end of one composite box culvert 1 into the tubular projection 33 at the other end of another composite box culvert 1.

[0040] The composite box culvert 1 has holes 4 that penetrate the outer perimeter covering portion 31 and the concrete structure 2. One hole 4 is formed on each of the four surfaces that make up the outer perimeter covering portion 31. The holes 4 may be used, for example, as injection holes for injecting lubricant or backfill material, or as discharge holes for releasing air.

[0041] In this embodiment, the composite box culvert 1 can improve shear strength by having a plurality of protruding portions 32 in the outer steel plate 3.

[0042] In this embodiment, the composite box culvert 1 has a protruding portion 32 made of a plate-like member, and the surface of the plate-like member in the thickness direction is in contact with the outer peripheral covering portion 31. This increases the contact area between the protruding portion 32 and the concrete structure 2, thereby improving the adhesion force of the concrete structure 2 to the protruding portion 32.

[0043] In this embodiment, the composite box culvert 1 can further improve its shear strength because the protruding portions 32 are arranged at substantially equal intervals on at least one of the four surfaces constituting the outer peripheral covering portion 31.

[0044] In this embodiment, the composite box culvert 1 can further improve its shear strength by having a ratio of the length of the protruding portion 32 in the protruding direction to the thickness of the concrete structure 2 to be between 0.03 and 1.

[0045] In this embodiment, the composite box culvert 1 can further improve its shear strength by having a ratio of the thickness of the protruding portion 32 to the thickness of the outer peripheral covering portion 31 of 0.25 or more and 4.00 or less.

[0046] Although embodiments of the present invention have been described above, the synthetic box culvert according to the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention. Furthermore, the synthetic box culvert according to the present invention is not limited by the effects described above.

[0047] For example, the composite box culvert 1 according to the above embodiment had a substantially square cross-section perpendicular to the axis L. However, the composite box culvert according to the present invention is not limited to this configuration, and the cross-section perpendicular to the axis L may be rectangular in shape, with the width or height being longer.

[0048] In the composite box culvert 1 according to the above embodiment, the corners of the outer and inner surfaces are rounded in a cross section perpendicular to the axis L. However, the composite box culvert according to the present invention is not limited to this configuration, and the corners of the outer and inner surfaces may be right angles in a cross section perpendicular to the axis L.

[0049] In the composite box culvert 1 according to the above embodiment, the protruding portion 32 is made of a plate-like member. However, the composite box culvert according to the present invention is not limited to this configuration, and the protruding portion 32 may be made of flat steel, H-shaped steel, C-shaped steel, L-shaped steel, etc. Furthermore, from the viewpoint of improving adhesion to the concrete structure 2, the protruding portion 32 may have a plurality of holes that penetrate in the thickness direction.

[0050] In the composite box culvert 1 according to the above embodiment, eight protrusions 32 are arranged at substantially equal intervals on each of the four surfaces constituting the outer peripheral covering portion 31. However, the composite box culvert according to the present invention is not limited to this configuration, and the protrusions 32 may be arranged at substantially equal intervals on at least one of the four surfaces constituting the outer peripheral covering portion 31, or the protrusions 32 may be arranged at uneven intervals on all surfaces. Furthermore, the number of protrusions 32 may be between four and fifteen on one surface constituting the outer peripheral covering portion 31. The number of protrusions 32 arranged on one surface constituting the outer peripheral covering portion 31 does not have to be equal on all surfaces.

[0051] In the synthetic box culvert 1 according to the above embodiment, one hole 4 is formed on each of the four surfaces constituting the outer peripheral covering portion 31. However, the synthetic box culvert according to the present invention is not limited to this configuration, and the position and number of holes 4 can be appropriately selected depending on the intended use. In other embodiments, the holes 4 may be used, for example, as holes for hanging devices to be attached during transport, inserts for attaching hanging devices during transport, or holes for injecting waterproofing agents. Furthermore, the synthetic box culvert according to the present invention does not necessarily have holes 4 formed in it.

[0052] The composite box culvert 1 according to the above embodiment does not have reinforcing bars. However, the composite box culvert according to the present invention is not limited to this configuration, and the concrete structure 2 may have main reinforcing bars embedded in it that extend along a direction perpendicular to the axis L and are arranged in multiple quantities around the axis L, and these main reinforcing bars may be joined to the protruding portion 32. The composite box culvert can further improve its shear strength with such a configuration. In addition, the concrete structure 2 may have distribution reinforcing bars embedded in it that extend along the axis L and are arranged in multiple quantities around the axis L. The reinforcing bars are not particularly limited, and those commonly used in the manufacture of reinforced concrete can be used.

[0053] This disclosure includes the following aspects: [1] A composite box culvert comprising a cylindrical concrete structure formed around an axis and an outer shell steel plate formed to cover the outer surface of the concrete structure, wherein the cross section perpendicular to the axis is rectangular, A composite box culvert having an outer shell steel plate having an outer covering portion that covers the entire outer surface of the concrete structure, and a plurality of protruding portions that protrude from the inner surface of the outer covering portion and are embedded in the concrete structure, and that extend from one end to the other end of the concrete structure along the axial direction. [2] The protruding portion is made of a plate-like member, The composite box culvert according to [1], wherein the surface of the plate-like member in the thickness direction is in contact with the outer peripheral covering portion. [3] The composite box culvert according to [1] or [2], wherein the protrusions are arranged at substantially equal intervals on at least one of the four surfaces constituting the outer peripheral covering portion. [4] The composite box culvert according to any one of [1] to [3], wherein the ratio of the length of the protruding portion in the projection direction to the thickness of the concrete structure is 0.03 or more and 1 or less. [5] The composite box culvert according to any one of [2] to [4], wherein the ratio of the thickness of the protruding portion to the thickness of the outer peripheral covering portion is 0.25 or more and 4.00 or less. [6] The concrete structure has embedded main reinforcement bars that extend in a direction perpendicular to the axis and are arranged in multiple quantities around the axis. The composite box culvert according to any one of [1] to [5], wherein the main reinforcement is joined to the protruding portion. [Explanation of Symbols]

[0054] 1 Box Culvert 2. Concrete structure 3. Outer shell steel plate 31 Outer peripheral covering 32 Projection part L axis

Claims

1. A composite box culvert comprising a cylindrical concrete structure formed around an axis, and an outer steel plate formed to cover the outer surface of the concrete structure, wherein the cross-section perpendicular to the axis is rectangular, A composite box culvert having an outer shell steel plate having an outer covering portion that covers the entire outer surface of the concrete structure, and a plurality of protruding portions that protrude from the inner surface of the outer covering portion and are embedded in the concrete structure, and that extend from one end to the other end of the concrete structure along the axial direction.

2. The aforementioned protruding portion is made of a plate-like member, The composite box culvert according to claim 1, wherein the surface of the plate-like member in the thickness direction is in contact with the outer peripheral covering portion.

3. The composite box culvert according to claim 1 or 2, wherein the protruding portions are arranged at substantially equal intervals on at least one of the four surfaces constituting the outer peripheral covering portion.

4. The composite box culvert according to claim 1 or 2, wherein the ratio of the length of the protruding portion in the projection direction to the thickness of the concrete structure is 0.03 or more and 1 or less.

5. The composite box culvert according to claim 2, wherein the ratio of the thickness of the protruding portion to the thickness of the outer peripheral covering portion is 0.25 or more and 4.00 or less.

6. The concrete structure has embedded main reinforcement bars that extend along a direction perpendicular to the axis and are arranged in multiple locations around the axis. The composite box culvert according to claim 1 or 2, wherein the main reinforcement is joined to the protruding portion.

Images