JP2020105768A - Box culvert - Google Patents

Abstract

To provide a box culvert which improves the quality of joint parts between walls and top plates and prevents cracks and can be used under high banking conditions.SOLUTION: A side wall 23 of a box culvert 1 consists of precast sidewall members 2. A top plate is composed of a PC plate 5 placed and erected on a haunch 24 protruding inward from the two precast side wall members 2, and cast-in-place concrete 6 formed on the PC plate 5. The thickness of the top plate is 500-2,500 mm, a whole of an end joint 21 between the side wall 23 and the top plate is a part of the precast side wall member 2, and there is no lap joint of reinforcing-bar inside the end joint 21.SELECTED DRAWING: Figure 7

Description

The present invention relates to box culverts. Precast concrete is simply called precast. Moreover, prestressed concrete is described as PC.

In recent years, high embankments of 20 to 30 m have been adopted for roads constructed to cross valleys, rivers, roads, etc. in mountainous areas, and the overburden of box culverts also tends to be high embankments. In the box culvert used under high embankment conditions, the member thickness of the top slab, the bottom slab, and the side wall may become large so as to be able to withstand the high embankment, and the thickness may be close to 2 m.

In the box culvert used under such a high embankment condition, there are the following problems in precasting, so that a complete precast product is not found.
-If the thickness of the precast member is large, it is disadvantageous to use the precast material because of the size limitation when transporting the precast member to the site.
-Because of the weight limitation during transportation, it is necessary to keep one member to about 25t, which increases the number of divisions of the precast member.
-It is difficult to join the precast top plate members to the precast side wall members on both sides, and internal support work for temporary placement is required.
-Box culverts used under high embankment conditions are not standardized.

Therefore, box culverts used under high embankment conditions are generally constructed of cast-in-place concrete. However, in-situ concrete requires a long construction period because after placing the bottom slab, a large-scale form supporting work is installed according to a large amount of placement and the side wall and the top slab are placed.

Therefore, the present inventors are considering combining precast and in-situ casting in a box culvert used under high embankment conditions.

Although there is no description in Patent Documents 1 and 2 that it is used under high embankment conditions, as shown in FIG. 10, it also serves as a formwork between the precast side wall member 51 and the haunch 52 protruding inward. A PC slab 53 was installed, and reinforcing bars were placed on the PC slab 53 and at the corners (joints) 54, and a cast-in-place concrete 55 was placed, and the PC slab 53 and the cast-in-place concrete 55 formed a top slab. Box culvert 50 is disclosed. The box culvert 50 uses the PC plate 53, which is a structural member, also as a mold for the cast-in-place concrete 55, so that there is an advantage that mold support is not required.

Here, the upper end of the side wall is on the extension of the lower surface of the top plate, and the side edge of the top plate is on the extension of the inner surface of the side wall. The "corner part" referred to in Patent Documents 1 and 2 is a rectangular parallelepiped part between the upper end of the side wall and the side end of the top plate, and is also called "joint part" (in the present application, the term "joint part"). To use).

JP, 2008-223370, A JP, 2011-89390, A

However, since the box culvert 50 described above is constructed by in-situ casting the joint, which is the most important part of the rigid frame structure, it is difficult to stabilize the quality. Further, since there is a lap joint in which the loop streak 56 projecting from the precast side wall member 51 and the loop streak 57 projecting from the top plate are overlapped and joined with concrete inside the joint portion 54, the Japan Road Association "Road Bridge Specification With reference to "," an unexpected crack may occur in the joint portion 54 due to stress concentration, drying shrinkage, and the like, and the assumption of the load bearing mechanism may not hold.

Therefore, an object of the present invention is to improve the quality of the joint portion between the wall and the top plate, prevent cracks, and enable the use under high embankment conditions.

According to the present invention, a wall is formed of a precast wall member, and a top plate is formed on a PC plate mounted on a haunch projecting inward from two precast wall members, and is formed on the PC plate. In the box culvert, which is composed of cast-in-place concrete and
The top plate has a thickness of 500 to 2500 mm,
The entire joint between the wall and the top plate is a part of the precast wall member, and there is no lap joint of reinforcing bars in the joint.

Here, it is preferable that the rebar embedded in the joint and the rebar embedded in the cast-in-place concrete are directly connected by a mechanical joint.

The precast wall member may include a top plate end portion that projects inward from the joint and forms a part of the top plate. Since there are complicated bar arrangements at the joint, it is difficult to secure a bar arrangement space.By giving a part of the bar arrangement space to the overhanging top plate end, the degree of freedom of bar arrangement increases. Is.

The cast-in-place concrete is preferably joined to the PC plate by digging into the roughened joint upper surface of the PC plate and embedding a dowel reinforcement projecting upward from the PC plate. It is preferable that the amount of reinforcement of the dowel reinforcement is 0.1 to 0.3% of the area of the upper surface of the joint.

[Action]
The present invention has the following effects.
-By using the PC version as a part of the formwork, it is possible to eliminate the need for formwork support of cast-in-place concrete on the top version. Further, the joint portion can also be used as a part of the formwork, thereby eliminating the need for a formwork for the side end face of the in-situ cast concrete of the top plate. Therefore, construction becomes easy.
-By precasting the joint, which is the most important part of the ramen structure, the quality can be improved compared to in-situ casting.
-Reinforcing bar assembly is easy and workability is excellent because there is no need to arrange joints for complicated lap joints.
・Because there is no lap joint of reinforcing bars at the joint, cracks are less likely to occur at the joint due to stress concentration or drying shrinkage.
-Since the reinforcing bars of the joint and the reinforcing bars of cast-in-place concrete are directly connected, the stress transmission between the top plate and the wall is sufficiently performed, and the structure is excellent in stability.
-Because the top plate includes a PC plate and cast-in-place concrete and has a thickness of 500 to 2500 mm, it can be used under high embankment conditions.

The box culvert of the present invention can improve the quality of the joint between the wall and the top plate and prevent cracks, and can be used under high embankment conditions.

FIG. 1 is an exploded front view of a precast member forming the single box culvert of the first embodiment. FIG. 2 is an exploded perspective view of FIG. 1 viewed obliquely. FIG. 3A is a front view when the precast member is joined and the PC plate is placed on the haunch, and FIG. 3B is a cross-sectional view of the PC plate of FIG. FIG. 4 is a perspective view of FIG. 3A viewed obliquely. FIG. 5A is a front view when a continuous reinforcing bar and a hook reinforcing bar are connected to the precast member, and FIG. 5B is a cross-sectional view of the PC plate of FIG. FIG. 6 is a perspective view of FIG. 5A viewed obliquely. FIG. 7A is a front view of a continuous box culvert constructed by pouring in-situ concrete onto the PC plate, and FIG. 7B is a cross-sectional view of the PC plate of FIG. FIG. 8 is a perspective view of FIG. 7A viewed obliquely. FIG. 9 is a front view of the double box culvert of the second embodiment. FIG. 10 is a partial front view of a conventional box culvert.

1. Box culvert The box culvert is not only a single box culvert with one internal space (Fig. 7), but also a multiple box culvert with two internal spaces arranged side by side (two box culverts and Fig. 9). Box culverts are common.)
The "wall" of the single box culvert is only the "side wall" on both sides (Fig. 7).
The "wall" of the multiple box culvert includes "side walls" on both sides and "intermediate wall" that partitions the internal space (Fig. 9).

2. Joining part Therefore, in the case of a single box culvert, the "joining part" between the wall and the top plate is only the "end joining part" between the side wall and the top plate (Fig. 7).
In the case of multiple box culverts, the "joint" between the wall and the top plate includes the "end joint" between the side wall and the top plate and the "intermediate joint" between the intermediate wall and the top plate (Fig. 9).

3. Precast wall member Therefore, in the case of the single box culvert, the "precast wall member" that constitutes the wall is only the "precast side wall members" on both sides (Fig. 7).
In the case of a multiple box culvert, the "precast wall member" that constitutes the wall includes "precast side wall members" on both sides and "precast intermediate wall member" (Fig. 9).

Therefore, the present invention includes the following two aspects.
(1) A mode in which the "end joint part" is a part of the "precast side wall member" and there is no lap joint of the reinforcing bar in the "end joint part" (2) The "intermediate joint part" is a "precast intermediate wall member" Which is a part of the above, and in which there is no lap joint of reinforcing bars in the "intermediate joint"

Further, the precast wall member may not be divided in the middle of the vertical direction, or may be formed by being divided in the middle of the vertical direction (two or three divisions are practical). The divided and formed parts are joined to each other on the site.

4. Bottom plate In the present invention, the structure of the bottom plate is not particularly limited. The bottom slab may be composed of, for example, a precast bottom slab member, cast-in-place concrete, or a combination thereof.

Next, embodiments of the present invention will be described with reference to the drawings. The structure, material, shape and dimensions of each part of the embodiment are examples, and can be changed as appropriate without departing from the spirit of the invention.

[Example 1]
As shown in FIGS. 7 and 8, Example 1 shown in FIGS. 1 to 8 is a large-sized (for example, 3000 to 10000 mm in length and 4000 to 17000 mm in width) single continuous box culvert 1. Both side walls (23 described later) are made of the precast side wall member 2. The bottom plate is composed of the precast bottom plate member 4 and a part of the two precast side wall members 2 (bottom plate end portion 26 described later). The top plate is placed on the haunch 24 projecting inward from the two precast side wall members 2 and installed on the PC plate 5, the cast concrete 6 formed on the PC plate 5, and the precast It is composed of a part of the side wall member 2 (top plate end portion 22 described later). Then, the thickness of the top plate is 500 to 2500 mm, the entire end joint portion (21 described later) of the side wall 23 and the top plate is a part of the precast side wall member 2, and the rebar is provided in the end joint portion 21. It is characterized by the absence of a lap joint.

(Precast side wall member 2)
The precast side wall member 2 includes an end joint portion 21, a top plate end portion 22 protruding inward from the end joint portion 21, a side wall 23, and a haunch 24 upper surface at a boundary level between the end joint portion 21 and the side wall 23. As described above, it includes a haunch 24 that protrudes inward from the side wall 23, a bottom end joint 25 that is a joint with the bottom plate, and a bottom plate end portion 26 that extends inward from the bottom end joint 25. The amount of protrusion of the haunch 24 is larger than the amount of protrusion of the top plate end portion 22.

As shown in FIG. 1, the precast side wall member 2 is composed of an upper member 2a and a lower member 2b, which are divided into two parts at the center in the vertical direction, and are vertically joined by a mortar filling joint 10 on site. The mortar filling joint 10 includes both filling joint reinforcing bars 11 embedded in the upper member 2a and the lower member 2b, a common sleeve 12 embedded in the vicinity of an end face of either one of the members, and both inside the sleeve 12. It is composed of mortar (not shown) that is filled in the gap between the reinforcing bar 11 for filling joint and the reinforcing bar 11 for filling in the sleeve 12 and hardened in a state where the end of the reinforcing bar 11 for filling joint has entered.

As shown in FIG. 3, the end joint portion 21 and the top plate end portion 22 are provided with a plurality of mechanical joints 7 (for example, screw joints) arranged in a lattice array near the end face of the top plate end portion 22. The connected mechanical joint reinforcing bar 8 is buried. As shown in FIG. 1, further reinforcing reinforcing bars are embedded in the upper member 2a and the lower member 2b.

(Precast bottom plate member 4)
The precast bottom slab member 4 forms an intermediate portion of the bottom slab, and is joined to the lower member 2b by the mortar filling joint 10 on site. The mortar filling joint 10 includes a rebar 11 for both filling joints embedded in the precast bottom plate member 4 and the lower member 2b, a common sleeve 12 embedded in the vicinity of an end face of one of the same members, and a sleeve 12 in the sleeve 12. It is composed of mortar (not shown) that is filled and hardened in a gap between the reinforcing bars 11 for filling joints in the sleeve 12 in a state where the ends of the reinforcing bars 11 for filling joints have entered.

(PC version 5 and cast-in-place concrete 6)
Both ends of the PC slab 5 are supported by the haunch 24, and the tensile stress is applied to the lower edge of the span by the weight of the top slab (PC slab 5 and cast-in-place concrete 6) and the load of the embankment on the top slab (during use). Therefore, the PC steel material 13 is arranged in the concrete slab, and prestress (compressive stress) is introduced into the lower edge by the pretension method or the posttension method. The PC plate 5 is made of precast.
The cast-in-place concrete 6 bites into the roughened joint upper surface of the PC plate 5 and is firmly joined to the PC plate 5 by embedding the dowel reinforcement 14 projecting upward from the PC plate 5. Further, the cast-in-place concrete 6 is directly connected to the mechanical joints 7 of the upper members 2a on both sides and is erected, and the continuous rebar 15 is directly connected to each mechanical joint 7 and ends in the cast-in-place concrete 6. By being embedded with the hook rebar 16, it is firmly joined to the upper member 2a.
Among the thicknesses of the top plate of 500 to 2500 mm, the thickness of the PC plate 5 is 100 to 500 mm and the thickness of the cast-in-place concrete 6 is 400 to 2000 mm.

The continuous box culvert 1 of the embodiment configured as described above conveys the precast side wall member 2 (upper member 2a and lower member 2b), the precast bottom plate member 4 and the PC plate 5 to the construction site, and at the construction site. It is assembled as follows. It should be noted that connecting a plurality of box culverts in the path length direction to form a waterway, a road, etc. is known.

(1) First, as shown by the changes in FIGS. 1, 2, 3 and 4, the lower member 2b and the precast bottom plate member 4 are joined by a mortar filling joint 10, and the lower member 2b and the upper member 2a are mortar filled. It joins by the joint 10.
(2) Next, as shown in FIGS. 3 and 4, the PC plate 5 is placed on the haunch 24 and erected.
(3) Next, as shown in FIGS. 5 and 6, the continuous reinforcing bar 15 and the hook reinforcing bar 16 are connected to the mechanical joint 7 of the upper member 2a. At this time, the PC plate 5 can be used as a work scaffolding substitute.
(4) Next, as shown in FIGS. 7 and 8, the cast-in-place concrete 6 is cast on the PC plate 5. At this time, since the PC plate 5 functions as a part of the form and the PC plate 5 is supported by the haunch 24, the form supporting work is unnecessary.

According to this embodiment, the following effects can be obtained.
-By using the PC slab 5 as a part of the formwork, it is possible to eliminate the need for the formwork support of the cast-in-place concrete 6 on the top plate. Further, the end joint portion 21 can also be used as a part of the formwork to eliminate the need for a formwork for the side end face of the top casting in-situ concrete 6. Therefore, construction becomes easy.
-By precasting the end joint part 21, which is the most important part of the ramen structure, the quality can be improved compared to in-situ casting.
・Reinforcing bar assembly is easy and workability is excellent because there is no need to arrange end joints for complicated lap joints.
-Since the end joint 21 does not have a lap joint of reinforcing bars, cracks due to stress concentration, drying shrinkage, etc. are less likely to occur at the end joint 21.
The mechanical joint rebar 8 of the end joint 21 and the continuous rebar 15 and the hook rebar 16 of the cast-in-place concrete 6 are directly connected by the mechanical joint 7, so that the stress transmission between the top plate and the side wall is sufficient. And has excellent structural stability.
Since the top plate includes the PC plate 5 and the cast-in-place concrete 6 and has a thickness of 500 to 2500 mm, it can be used under high embankment conditions.

[Example 2]
Example 2 shown in FIG. 9 is a large double box culvert 20 and is different from Example 1 in that it is provided with a precast intermediate wall member 3 and has two top plates and two bottom plates. ..

(Precast intermediate wall member 3)
The precast intermediate wall member 3 includes, from above, an intermediate joint portion 31, a top plate end portion 32 protruding from the intermediate joint portion 31 to both insides, an intermediate wall 33, and a boundary between the intermediate joint portion 31 and the intermediate wall 33. A haunch 34 that protrudes inward from the intermediate wall 33 so that the upper surface of the haunch 34 is at the level, a bottom intermediate joint 35 that is a joint with the bottom slab, and a bottom plate end that extends from the bottom intermediate joint 35 to both insides. And a portion 26. The amount of protrusion of the haunch 34 is larger than the amount of protrusion of the top plate end portion 32.

The precast intermediate wall member 3 is composed of an upper member 3a and a lower member 3b, which are divided into two parts at the center in the vertical direction, and are joined vertically at the site by a mortar filling joint (the same as the one described above).

In the double box culvert 20 of Example 2, the side walls 23 on both sides are made of the precast side wall member 2 and the intermediate wall 33 is made of the precast intermediate wall member 3. The slab comprises a precast bottom slab member 4, a bottom slab end portion 26 of the precast side wall member 2, and a bottom slab end portion 36 of the precast intermediate wall member 3. The top plate is placed on the haunch 24 of the precast side wall member 2 and the haunch 34 of the precast intermediate wall member 3, and is erected on the PC plate 5, and the cast-in-place concrete 6 formed on the PC plate 5. And a top plate end portion 22 of the precast side wall member 2 and a top plate end portion 32 of the precast intermediate wall member 3. Then, the thickness of the top plate is 500 to 2500 mm, the entire end joint portion 21 is a part of the precast side wall member 2, and there is no lap joint of reinforcing bars in the end joint portion 21, The whole is a part of the precast intermediate wall member 3, and there is no lap joint of reinforcing bars in the intermediate joint portion 31.

The other points of the second embodiment are common to the embodiments. Also according to the second embodiment, the same operational effect as the operational effect of the first embodiment (the end joining portion is read as “end joining portion and intermediate joining portion”) can be obtained.

It should be noted that the present invention is not limited to the above-described embodiments, and can be embodied with appropriate modifications without departing from the spirit of the invention.
(1) The precast side wall member 2 is not provided with the top plate end portion 22. In this case, the inner side surface of the end joint portion 21 is an extension of the inner side surface of the side wall 23.
Further, the precast intermediate wall member 3 should not include the top plate end portion 32. In this case, the inner side surface of the intermediate joint portion 31 is an extension of the inner side surface of the intermediate wall 33.
(2) The precast side wall member 2 is not divided in the middle of the vertical direction.
In addition, the precast intermediate wall member 3 shall not be divided in the middle of the vertical direction.
(3) Replacing the precast bottom plate member 4 with in-situ casting.

1 1 continuous box culvert 2 Precast side wall member 2a Upper member 2b Lower member 3 Precast intermediate wall member 3a Upper member 3b Lower member 4 Precast bottom plate member 5 PC plate 6 Cast-in-place concrete 7 Mechanical joint 8 Reinforcing bar for mechanical joint 10 Mortar filling Joints 11 Reinforcing bars for filling joints 12 Sleeves 13 PC steel materials 14 Gibel reinforcing bars 15 Continuous reinforcing bars 16 Hook reinforcing bars 20 Double box culverts 21 End joints 22 Top plate end portions 23 Side walls 24 Haunches 25 Bottom end joints 26 Bottom plate end portions 31 Intermediate joints Part 32 Top plate end part 33 Intermediate wall 34 Haunch 35 Bottom intermediate joint part 36 Bottom plate end part

Claims (4)

The walls (23, 33) consist of precast wall members (2, 3) and the top plate is mounted on a haunch (24, 34) projecting inwardly from the two precast wall members (2, 3). In a box culvert including a erected PC plate (5) and cast-in-place concrete (6) formed on the PC plate (5),
The thickness of the top plate is 500-2500 mm,
The joint (21, 31) between the wall (23, 33) and the top plate is a part of the precast wall member (2, 3), and there is no lap joint of the reinforcing bars in the joint (21, 31). Box culvert featuring. Reinforcing bars (8) buried in the joints (21, 31) and reinforcing bars (15, 16) buried in cast-in-place concrete (6) are directly connected by a mechanical joint (7). Box culvert described in 1. The box according to claim 1 or 2, wherein the precast wall members (2, 3) are provided with top plate end portions (22, 32) that project inward from the joint portions (21, 31) and form a part of the top plate. Calvert. The cast-in-place concrete (6) digs into the roughened joint upper surface of the PC plate (5), and by embedding the dowel reinforcing bar (14) projecting upward from the PC plate (5), the PC plate The box culvert according to claim 1, 2 or 3, which is joined to (5).

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