JP6925091B1 - Box culvert - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a box culvert capable of achieving high yield strength and high quality while having a thin wall due to an integrated steel plate / concrete structure. SOLUTION: A box culvert 1 of the present invention has a substantially rectangular tubular steel frame body 10 having a communication space S inside, a concrete skeleton 20 provided around the inner surface of the steel frame body 10, and a part of the steel frame. A plurality of fixing materials 30 which are fixed to the inner surface of the body 10 and whose other parts are arranged in the concrete skeleton 20 and a plurality of reinforcing bars 40 which are arranged in the concrete skeleton 20 are provided, and the plurality of fixing materials 30 are provided. It is characterized in that the steel frame body 10 and the concrete skeleton 20 are integrally configured to be able to behave. [Selection diagram] Fig. 1

Description

The present invention relates to a box culvert, and more particularly to a box culvert capable of achieving high yield strength and high quality while being thin due to a steel plate / concrete integrated structure.

Box culvert is a reinforced concrete box used for construction purposes such as propulsion method and open-cut method.
Patent Document 1 discloses a box culvert for propulsion work and a tunnel propulsion method using the box culvert.
In the propulsion method using box culvert, while excavating the pit wall in front of the box culvert, the box culvert is pushed in sequentially using a hydraulic jack, and an underpass and a waterway are constructed by the continuous internal space of the box culvert.

Japanese Unexamined Patent Publication No. 2001-173368

The conventional box culvert requires a certain cross section (wall thickness) for the concrete skeleton in order to secure sufficient proof stress against earth pressure, live load, earthquake external force, etc., so the wall thickness is thinned to reduce the internal space. It was difficult to secure it widely.
In addition, when the construction depth differs depending on the construction area in the propulsion method, even if the wall pressure is different depending on the size of the overburden, even if it is a small overburden, a box culvert with a large cross section designed by the large overburden is used. I had no choice but to go.
For this reason, a large excavator corresponding to a box culvert with a large cross section is required regardless of the size of the overburden, which increases the construction cost.

An object of the present invention is to provide a box culvert capable of solving the above-mentioned problems of the prior art.

The box culvert of the present invention has a substantially rectangular tubular steel frame having a communication space inside, a concrete skeleton circulated around the inner surface of the steel frame, and a part fixed to the inner surface of the steel frame, and other parts. It is equipped with a plurality of fixing materials arranged inside the concrete skeleton and a plurality of reinforcing bars arranged inside the concrete skeleton, and the steel frame body and the concrete skeleton can behave integrally through the plurality of fixing materials. It is characterized by being configured.

In the box culvert of the present invention, a part of the reinforcing bar may be fixed to the inner surface of the steel frame body.

In the box culvert of the present invention, the fixing material is arranged in parallel with the two lower chord members attached along the circumferential direction of the inner wall of the steel frame and the two lower chord members on the communication space side of the two lower chord members. It may be a truss reinforcing bar gibber composed of one provided upper chord member and a plurality of continuous chevron diagonal members connecting each lower chord member and upper chord member.

In the box calvert of the present invention, the steel frame body includes a frame body body, a female joint provided at one end of the frame body body, and a male joint provided at the other end of the frame body body, and the female joint body is an inner wall. It may have a side plate extending to the communication space side over the entire circumference of the.

In the box culvert of the present invention, an elastic seal ring may be ringed on the outer wall of the male joint.

In the box culvert of the present invention, the steel frame may also serve as a formwork when placing the concrete skeleton.

The box culvert of the present invention has a high shear strength due to a steel plate / concrete integrated structure in which the outer surface of the concrete skeleton is covered with a steel skeleton and the concrete skeleton and the steel frame are integrally movably connected via a fixing material. And can exhibit bending strength.
Therefore, the wall thickness of the concrete skeleton can be made thin, a large internal space can be secured with respect to the outer dimensions, and the degree of freedom in design can be increased.
In particular, in the propulsion method, a box culvert with a thin wall and a large cross section can be used regardless of the size of the overburden, and it can be constructed with a small excavator, so that the construction cost can be significantly reduced.
Further, since the steel frame body is continuous on the outer periphery, the frictional force on the peripheral surface with the surrounding soil during propulsion is reduced, so that the press-fitting can be smoothly performed with a relatively small propulsive force.

The perspective view from the male joint side of the box culvert of this invention. The perspective view from the female joint side of the box culvert of this invention. Explanatory drawing of the formwork unit. Explanatory drawing of fixing material. Explanatory drawing of the reinforcing bar. Explanatory drawing of Example 2. FIG.

Hereinafter, the box culvert of the present invention will be described in detail with reference to the drawings.
In the present invention, directional terms such as "upper", "lower", "horizontal", "front", and "rear" refer to the state in which the box culvert is erected with the male joint facing the front side, that is, the state shown in FIG. Means each direction in.

[Box Culvert]
<1> Overall configuration (Figs. 1 and 2)
The box culvert 1 of the present invention is a box body used for construction purposes such as a propulsion method and an open-cut method.
The box culvert 1 includes a substantially rectangular tubular steel frame body 10, a concrete skeleton 20 provided around the inner surface of the steel frame body 10, and a part fixed to the inner surface of the steel frame body 10 and the other part inside the concrete skeleton 20. A plurality of fixing materials 30 arranged in the concrete frame 20 and a plurality of reinforcing bars 40 arranged in the concrete skeleton 20 are provided at least.
Inside the steel frame body 10 and the concrete skeleton 20, there is a communication space S that communicates both the front and rear surfaces of the box culvert 1.
The box culvert 1 of the present invention has one feature in a steel plate / concrete integrated structure in which a steel frame body 10 and a concrete skeleton 20 are integrally and movably connected via a plurality of fixing materials 30.
That is, by winding the concrete skeleton 20 entirely around the steel frame body 10, the steel frame body 10 can be regarded as a structural member, and the outer reinforcing bars and the shear resistance material in the box culvert of the prior art can be omitted. This makes it possible to reduce the wall thickness of the concrete skeleton 20 and secure a wide internal space.

<2> Steel frame body The steel frame body 10 is a member having a function of a tensile resistance material in a steel plate / concrete integrated structure.
The steel frame body 10 includes a substantially rectangular tubular frame body 11 having a communication space S inside, a female joint 12 provided at the rear of the frame body 11, and a male joint provided at the front of the frame body 11. 13 and at least.
In this example, as the steel frame body 10, a tubular structure made of SM490 steel plate having a thickness of 9 mm is adopted.
The female joint 12 and the male joint 13 of the steel frame body 10 are a pair of connecting joints, and a plurality of box culverts 1 can be connected in the tunnel axial direction by fitting the female joint 12 and the male joint 13.

<2.1> Female joint The female joint 12 has a joint structure that fits into the male joint 13 of the subsequent box culvert 1 in a plurality of continuous box culverts 1.
The female joint 12 extends the side plate 12a toward the communication space S side over the entire circumference of the inner wall of the frame body 11 at the rear portion of the frame body 11.
The front surface of the side plate 12a is in contact with the rear surface of the concrete skeleton 20. That is, the concrete skeleton 20 is partitioned by the side plate 12a, and the concrete skeleton 20 does not extend in the female joint 12.
When the box culvert 1 is used in the propulsion method, the thrust is concentrated inside the curved portion of the female joint 12 during propulsion, especially in the sharp curved portion. By distributing this thrust to the side plate 12a, the outer wall (collar) of the female joint 12 is distributed. ) Can be suppressed. This makes it possible to prevent deterioration of the sealing performance of the joint portion.

<2.2> Male joint The male joint 13 has a joint structure that fits into the female joint 12 of the preceding box culvert 1 in a plurality of continuous box culverts 1.
The male joint 13 is formed by reducing the diameter of at least the outer wall of the frame body 11 toward the communication space S side at the front portion of the frame body 11.
An elastic seal ring 13a is ringed on the outer wall of the male joint 13. Since the structure of the seal ring 13a is known, it will not be described in detail here.

<2.3> Functions of the steel frame body The steel frame body 10 exhibits the following plurality of functions.
(1) Functions of the outer main reinforcing bars and force distribution bars in the steel plate / concrete integrated structure.
(2) Formwork function when placing 20 concrete skeletons.
(3) Protective function of the concrete skeleton 20 to prevent edge chipping during transportation.
(4) Water stop function after operation.
Further, when the box culvert 1 is used in the propulsion method, the following functions are further exhibited in addition to the above.
(1) A function to prevent cracks in the concrete skeleton 20 during propulsion, especially due to stress concentration in curved propulsion.
(2) Propulsion smoothing function by applying a lubricant such as bendnite liquid to the outer wall.

<2.4> Formwork unit (Fig. 3)
In the box culvert 1 of the present invention, the steel frame body 10 and the fixing material 30 attached to the inner wall of the steel frame body 10 constitute a formwork unit 10A for placing the concrete skeleton 20.
In this example, since the reinforcing bar 40 is attached to the inner wall of the steel frame body 10 in addition to the fixing material 30, the form unit 10A further includes the reinforcing bar 40.
A method for manufacturing the box culvert 1 using the formwork unit 10A will be described later.

<3> Concrete skeleton The concrete skeleton 20 is a member having a function of a compression resistance material in a steel plate / concrete integrated structure.
The concrete skeleton 20 is provided around the inside of the steel frame body 10.
Inside the concrete skeleton 20, a connected space S having a shape corresponding to the use of the box culvert 1 is formed.
The concrete skeleton 20 is provided with a sheath hole for vertical tightening by a PC steel rod or a PC stranded wire, a grout injection hole (not shown), and the like.
Other structures of the concrete skeleton 20 in the box culvert 1 are known and will not be described in detail here.

<4> Fixing material (Fig. 4)
The fixing material 30 is a slip-preventing member for fixing and integrating the steel frame body 10 to the concrete skeleton 20.
In this example, as the fixing material 30, two lower chord members 32 attached along the circumferential direction of the inner wall of the steel frame body 10 and two lower chord members 32 parallel to the communication space S side from the two lower chord members 32. A truss reinforcing bar gibber composed of one upper chord member 31 arranged in the above, a plurality of continuous chevron diagonal members 33 connecting each lower chord member 32 and the upper chord member 31, is adopted.
The truss reinforcing bar gibber not only has a slip prevention function, but also exhibits a high reinforcing function for the concrete skeleton 20 by the upper chord member 31 and the lower chord member 32 acting as main bars and the mountain-shaped diagonal member 33 acting as a shear reinforcing bar. .. Further, since the gap between the members is large, the concrete filling property is high when the concrete skeleton 20 is placed with concrete.
In this example, the fixing members 30 are arranged in parallel in four rows in the axial direction (direction orthogonal to the circumferential direction) on each surface of the steel frame body 10. However, the number of rows of the fixing material 30 is not limited to four, and may be one to three rows, or five or more rows.

<5> Reinforcing bar (Fig. 5)
The reinforcing bar 40 is a tensile resistance material that reinforces the concrete skeleton 20.
The reinforcing bar 40 is embedded inside the concrete skeleton 20.
In this example, as the reinforcing bars 40, a plurality of main bars 41 arranged along the circumferential direction of the inner wall of the steel frame body 10, and a plurality of force distribution bars 42 extending in the orthogonal direction between the plurality of parallel main bars 41. A combination of a plurality of haunch bars 43 diagonally bridged between the main bars 41 in two directions orthogonal to each other at the corners of the steel frame body 10 is adopted.
However, the structure of the reinforcing bar 40 is not limited to the above, and an appropriate design such as arranging a stirrup can be made according to the required performance.
Further, in this example, both ends of the main bar 41 arranged along the first surface of the steel frame body 10 are bent in the circumferential direction along the second surface orthogonal to the first surface to form the fixing end 41a. , The fixing end 41a is welded to the second surface.
In the case of this example, by connecting the reinforcing bar 40 to the inner wall of the steel frame body 10, it is possible to improve the integrity of the steel frame body 10 and the concrete skeleton 20 via the reinforcing bar 40.

<6> Manufacturing method Box culvert 1 is manufactured by, for example, the following procedure.
The formwork unit 10A is manufactured by welding the fixing material 30 and the reinforcing bar 40 to the inner wall of the steel frame body 10.
The formwork unit 10A is installed in the work yard with the male joint 13 facing up.
In the inner space of the formwork unit 10A, an inner formwork having an outer shape for defining the communication space S of the concrete skeleton 20 is arranged.
Depending on the arrangement of the inner formwork, a concrete casting space is defined between the inner wall of the steel frame body 10, the side plate 12a of the female joint 12, and the outer wall of the inner formwork.
If necessary, a support material is assembled on the outside of the formwork unit 10A to support the steel frame body 10 of the formwork unit 10A from the outside.
Concrete is poured between the steel frame body 10 and the inner formwork up to the edge of the male joint 13 of the steel frame body 10. Although the composition and type of concrete are not limited, it is desirable to use a water reducing agent or an AE water reducing agent as an admixture in order to prevent deterioration of the performance of the fixing material 30.
After the concrete is hardened, the inner formwork is disassembled to the communication space S side and removed. As a result, the communication space S is formed in the concrete skeleton 20, and the box culvert 1 is completed.

<6.1> Quality of concrete skeleton The box culvert 1 of the present invention has a structure in which a steel frame body 10 and a concrete skeleton 20 are integrated by a fixing material 20 attached to an inner wall of the steel frame body 10.
Therefore, it is not necessary to provide a side plate (collar material) as a slip stopper for the concrete skeleton 20 on the male joint 13 side.
If a side plate is provided on the male joint side of the steel frame to prevent slippage, the top edge of the concrete will be blocked by the side plate after the concrete is placed, so air bubbles in the concrete will remain near the top edge of the concrete. By hardening, the quality of the edge surface of the concrete skeleton is significantly reduced.
On the other hand, in the box culvert 1 of the present invention, since there is no side plate on the male joint 13 side of the steel frame body 10 and the box culvert 1 is open, air bubbles escape from the top end of the concrete to the air after the concrete is poured. Therefore, the high quality of the concrete skeleton 20 can be ensured by making the edge surface of the concrete skeleton 20 dense.

[Other Examples of Fixing Material]
In the first embodiment, the truss reinforcing bar gibber is used as the fixing material 30, but the fixing material 30 is not limited to this.
For example, as the fixing material 30, a stat gibber with a head (FIG. 6 (a)), a perforated steel plate gibber (FIG. 6 (b)), a steel pipe penetrating type perforated steel plate gibber (FIG. 6 (c)), or the like is adopted. May be good.
In short, it suffices that the steel frame body 10 and the concrete skeleton 20 have a fixing performance capable of acting integrally.

1 Box Culvert 10 Steel frame 10A Formwork unit 11 Frame body 12 Female joint 12a Side plate 13 Male joint 13a Seal ring 20 Concrete skeleton 30 Fixing material 31 Upper chord material 32 Lower chord material 33 Mountain-shaped diagonal material 40 Reinforcing bar 41 Main bar 41a 42 Power distribution muscle 43 Haunch muscle S Communication space

Claims (6)

A substantially rectangular tubular steel frame with a communication space inside,
A concrete skeleton laid around the inner surface of the steel frame and
A plurality of fixing materials in which a part is fixed to the inner surface of the steel frame and the other part is arranged in the concrete skeleton.
It is provided with a plurality of reinforcing bars arranged in the concrete skeleton.
It is characterized in that the steel frame body and the concrete skeleton are configured to be able to behave integrally via the plurality of fixing materials.
Box culvert. The box culvert according to claim 1, wherein a part of the reinforcing bar is fixed to the inner surface of the steel frame body. The fixing material was arranged in parallel with the two lower chord members attached along the circumferential direction of the inner wall of the steel frame and the two lower chord members on the communication space side of the two lower chord members. The invention according to claim 1 or 2, wherein the truss reinforcing bar gibber is composed of one upper chord member, a plurality of continuous chevron diagonal members connecting each of the lower chord members and the upper chord member, respectively. Box culvert. The steel frame body includes a frame body body, a female joint provided at one end of the frame body body, and a male joint provided at the other end of the frame body body, and the female joint body is the entire circumference of the inner wall. The box calvert according to any one of claims 1 to 3, further comprising a side plate extending toward the communication space side. The box culvert according to claim 4, wherein an elastic seal ring is ringed on the outer wall of the male joint. The box culvert according to any one of claims 1 to 5, wherein the steel frame body also serves as a formwork at the time of placing the concrete skeleton.

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