JP2991653B2 - Box culvert - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for construction of culverts, etc.
The present invention relates to a box culvert reinforced with steel.

[0002]

2. Description of the Related Art This type of box culvert 1 is shown in FIG.
As shown in FIG. 1, the top plate 2 and the bottom plate 3 are connected by left and right side walls 4, but conventionally, the top plate 2 and the bottom plate 3 are connected.
To reduce the concrete thickness, 9 and other rebar
As shown in FIG. 10 , a technique for embedding and reinforcing PC steel materials 5 and 6 in the top plate 2 and bottom plate 3 of the box culvert 1 has been established. That is, this kind of box culvert 1
In the top plate 2, the bottom plate 3, and the side wall 4, reinforcing bars (not shown) having a double cage structure are arranged at portions deviated inward and outward from the center in the thickness direction, respectively. But
PC steel materials 5 and 6 are intermittently arranged along the depth direction inside the formwork corresponding to the top slab 2 and the bottom slab 3 in order to avoid interference with the reinforcing bar, and then concrete is driven into the formwork, and the concrete is poured. When the PC steel materials 5 and 6 are hardened to a compressive strength of a certain level or more, a prestress is introduced into the concrete structure between the anchor plates 5a and 6a of the top plate 2 and the bottom plate 3 by applying tension F to the concrete structure. The strength is increased by the compression characteristics of the material. At that time, the top version 2
In consideration of the fact that the bottom slab 3 receives an external load during practical use and a bending moment that gradually increases from the end to the center acts, the method of disposing the PC steel materials 5 and 6 is as follows.
It is arranged so as to be curved inward as shown in FIG. 10 , or slightly inwardly from the axes p and q passing through the center in the thickness direction of the top plate 2 and the bottom plate 3 as shown in FIG. The top plate 2 or the bottom plate 3 has an outward bending moment M as shown in FIG.
As shown in FIG. 13 , p and Mq are generated to offset or reduce the internal tensile stress in practical use, and the top plate 2 and the bottom plate 3 are maintained while maintaining a constant load resistance to concrete.
Is designed to be thinner.

[0003]

However, when such a structure is adopted, an internal bending moment for bending the PC steel members 5 and 6 from the fixing portion formed by the anchor plates 5a and 6a at both ends to the side wall 4 and inwardly. Mr (see FIG. 12 ) acts. That is, when the fixing portions of the PC steel materials 5 and 6 are considered to be rigid, when the top plate 2 and the bottom plate 3 are subjected to a bending moment to bend outward, the upper and lower ends of the side walls 4 are turned to the top and bottom. As a result of maintaining the right angle with respect to the plate 2 and the bottom plate 3, the entire side wall 4 receives a bending moment in which the side wall 4 is bent in a concave direction. As described above, the inner upper and lower ends 4a and 4b of the side wall 4 are adjacent to the rigid portion and are directly subjected to the torsional force.
Since the upper and lower ends 4a and 4b are bent to different shapes, the inner upper and lower ends 4a and 4b must be most vulnerable to bending moment. For this reason, these inner upper and lower ends 4
10a and 10b cannot endure the tensile stress at the forefront, and FIG.
A crack c as shown in FIG. In particular, when the PC steel materials 5 and 6 are arranged in a curved shape, an extreme design can be achieved in which the top plate 2 and the bottom plate 3 are made as thin as possible as compared with the case where the PC steel materials 5 and 6 are arranged linearly.
The frequency of occurrence of cracks c at the upper and lower ends 4a and 4b inside the side wall 4 without any treatment is much higher.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method in which a PC steel material is arranged on a side wall, particularly when a PC steel material is curved and arranged on a top plate and a bottom plate. Prestress is introduced, and this PC steel material generates an outward bending moment in a direction to decrease the above-described inward bending moment. For this reason, the tensile stress inside the side wall can be reduced, and the occurrence of cracks at the upper and lower ends inside the side wall can be effectively suppressed.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a box culvert having a top plate, a bottom plate and a side wall, in which a PC steel material which is curved inward is disposed in a mold corresponding to the top plate and the bottom plate. after typing the concrete, giving tension to PC steel in those as to introduce concrete tissue prestressing constituting the top plate and bottom plate, also provided the PC steel inside the mold corresponding to the side walls , The abbreviation of this PC steel
The center is divided, and the fixing part of this divided part is
To the axis passing through the center in the thickness direction of the side wall rather than the attachment part
It is arranged linearly so as to be located on the outside, tension is applied after concrete is poured, and thereby prestress is introduced into the concrete structure constituting the side wall to generate an outward bending moment It is.

With such a structure, the strength of the top plate and the bottom plate is increased by disposing the PC steel material on the top plate and the bottom plate, and the thickness of the concrete structure is set as a structure capable of sufficiently withstanding an external load. Can be reduced as much as possible. Moreover, the inward bending moment generated on the side wall due to the PC steel material can be reduced by the outward bending moment generated by the PC steel material disposed on the side wall, so that the tensile stress inside the side wall is reduced. It is possible to effectively reduce the occurrence of cracks at the upper and lower ends inside the side wall. That is, according to the present invention,
The purpose of reinforcing the top plate and the bottom plate with the PC steel material can be achieved without generating cracks on the side walls. Such an effect is maximized when both moments are balanced.

Further, as another embodiment of the present invention,
PC curved inward in a mold corresponding to the top and bottom plates of a box culvert consisting of a top plate, a bottom plate and side walls
After arranging the steel material and driving concrete into the formwork, tension is applied to the PC steel material, and prestress is introduced into the concrete structure constituting the top and bottom plates,
A PC steel material is also arranged in the formwork corresponding to the side wall, and a tension is applied after the concrete is cast, whereby prestress is introduced into the concrete structure constituting the side wall to generate an outward bending moment. A plurality of the PC steel materials are provided as a set on the top plate and the bottom plate , and each set of the PC steel materials is distributed outside and inside with respect to an axis passing through the center in the thickness direction of the top plate and the bottom plate. And those arranged in multiple stages.

[0008] With such a structure, the PC steel material does not exist on the axis, so that a sheath hole usually provided only at the four corners is also provided on the axis, the connecting member is inserted, and the culverts are connected to each other. The connection strength can be effectively increased.

[0009]

EXAMPLES <Example illustrating the principle> The following examples to explain the principles of the present invention will be described with reference to FIGS. Box culvert 1 shown in FIG.
Not only introduces the prestress by the PC steel materials 5 and 6 to the top plate 2 and the bottom plate 3, but also makes the PC steel materials 7 and
7, a pre-stress is introduced. That is, the box culvert 1 of this embodiment is also
At the time of construction, the top plate 2, the bottom plate 3, and the side walls 4 are respectively doubled at portions deviated inward and outward from axes p, q, and r (see FIG. 2 ) passing through the center in the thickness direction . Reinforcing bars (not shown) forming a basket structure are arranged. PC steel materials 5 and 6 are arranged inside the formwork corresponding to the top plate 2 and the bottom plate 3 while avoiding interference with the reinforcing bars, and at the same time, correspond to the side walls 4. The PC steel 7 is also arranged inside the formwork to be formed. At that time, these P
The C steel members 5, 6, 7 are curved inward, that is, the central part is deviated inwardly from the axis p, q, r passing through the center of the top plate 2, the bottom plate 3, or the side wall 4 in the thickness direction. The anchor plates 5a, 6a and 7a, which are the fixing portions at both ends, are set so as to be deviated from the center to the outside thereof. Then, concrete is poured into the formwork in this state, and when the concrete hardens to a compressive strength of a certain level or more, a tension F is applied to the PC steel materials 5, 6, and 7, and the top plate 2, the bottom plate 3 In addition, a prestress is introduced into the side wall 4. Such prestress can be introduced not only by the post-tension method but also by the pre-tension method.

In a state where the box culvert having such a configuration is put to practical use, an external load acts on the top plate 2 and the bottom plate 3, and a bending moment is applied to the top plate 2 and the bottom plate 3 so as to curve them inward. However, in this box culvert 1, the bending moments Mp and Mq which gradually increase from the end to the center as shown in FIG. Since the bending moment is generated, the bending moment due to the external load can be reduced by these bending moments Mp and Mq, and preferably can be canceled. For this reason, as shown in FIG. 4 , the internal tensile stress of the top plate 2 and the bottom plate 3 can be eliminated or kept extremely small, and their thickness can be reduced as much as possible while maintaining effective load resistance. It becomes possible to plan. Moreover, PC steel 5,6 disposed in these top plate 2 and the bottom plate 3 is conventional, the inner upper and lower ends 4a of the side wall 4 by generating bending moment Mr towards the inside on the side walls 4 as shown in FIG. 1 0, Although this causes the crack c as shown in FIG. 8 in FIG. 4b, in this embodiment, the PC steel material 7 arranged on the side wall 4 generates an outward bending moment as shown in FIG. Therefore, the inward bending moment Mr can be canceled or effectively reduced by the outward bending moment Mr as shown in FIG . Therefore, according to the present embodiment, the purpose of reinforcing the top plate 2 and the bottom plate 3 to the maximum by the PC steel materials 5 and 6 having the curved arrangement is to generate cracks in the upper and lower inner ends 4a and 4b of the side wall 4. It can be achieved effectively without any problem.

Incidentally, for example, as shown in FIGS. 5 and 6,
In the box culverts 101 and 201 in which the side wall 4 is constituted by the outer wall 41 and the intermediate wall 42 and a plurality of culvert spaces are formed in parallel inside, the top plate 2 and the bottom plate 3 are made of PC steel 5, takes only 6 to bending moments outer wall 41 by disposing, since the offset is on the intermediate wall 42, the PC steel material 7 described above only in that the outer wall 41
Even if the PC steel material 8 is simply arranged in a straight line on the center line in the thickness direction of the intermediate wall 42 and the PC steel material 8 is arranged on the intermediate wall 42 , the operation and effect similar to those described above can be obtained. Is
You .

<First Embodiment> Next, a first embodiment of the present invention will be described. The PC steel material 107 disposed on the side wall 4 in the present embodiment is not a single piece continuously extending from the upper end to the lower end of the side wall 4 as in the embodiment for explaining the principle described above, but as shown in FIG. , The middle of which is divided. Even in such a configuration, if the divided portion is fixed by the anchor plate 107a and the fixed portion is located outside the end portion in the thickness direction of the side wall 4, the above-described principle can be achieved.
Actions and effects similar to those of the embodiment to be described can be obtained, and the bending moments of the inner upper and lower ends 4a and 4b of the side wall 4 where cracks easily occur can be appropriately canceled.

<Second Embodiment> Next, a second embodiment of the present invention will be described. As shown in FIG. 8 , a plurality of the PC steel materials 205 and 206 of this embodiment are provided as a set, and the PC steel materials 205 and 206 of each set are provided.
Reference numerals 206 are arranged outside and inside with respect to axes p and q passing through the center of the top plate 2 and the bottom plate 3 in the thickness direction, respectively, and are arranged in multiple stages. If you do this,
Since the PC steel materials 205 and 206 no longer exist on the axes p and q, the sheath holes 10 usually provided only at the four corners are also provided on the axes p and q to penetrate the connecting member, and the connection strength between the culverts is reduced. Can be enhanced effectively. In addition,
The principle described above is explained for these PC steel materials 205 and 206.
In order to give the same prestress introduction effect as the PC steel materials 5, 6 and the like of the embodiment and the first embodiment, the total cross-sectional area may be designed to be substantially the same. Even if the number increases, the thickness of the top plate 2 and the bottom plate 3 is not hindered, and the nut for fastening both ends is small, so that the anchor plate 205 is not required.
The pre-stress introduction region can be expanded by extending the interval between “a” and “206a”, and the pre-stress is dispersed and quickly transmitted to each part. Therefore, when the total cross-sectional area is the same, the actual Therefore, the reinforcement effect by the introduction of prestress is higher. Such a multi-stage arrangement structure can adopt not only a mode in which four or more even numbers are sorted up and down by the same number, but also a mode in which odd totals are sorted up and down such that the total cross-sectional area is substantially the same.

Other configurations can be variously modified without departing from the spirit of the present invention. For example, in the above embodiment, only the bending moment applied to the side wall from the PC steel material disposed on the top plate and the bottom plate was considered. However, in practical use, an external load may also act on the side wall inward in the thickness direction. It is significant to set the bending moment value of the PC steel introduced into the side wall in consideration of such a load. In addition, some box culverts have a structure in which the center of the side wall is divided and the whole has a half-split structure vertically. The present invention can be effectively applied to such a box culvert.

[0015]

The present invention is embodied in the above-described embodiment, and has the following effects. That is,
The box culvert of the present invention is designed such that when the PC steel material is curved and disposed on the top plate and the bottom plate in order to improve the load-bearing characteristics and reduce the wall thickness as much as possible, the PC steel material is also placed on the side wall up and down. A prestress is introduced by dividing and arranging the PC steel material, and the PC steel material generates an outward bending moment in a direction to reduce an inward bending moment acting on the side wall from the PC steel material of the top plate and the bottom plate. It was made. For this reason, the tensile stress inside the side wall can be reduced, and the occurrence of cracks at the upper and lower ends inside the side wall can be effectively suppressed. That is, according to the present invention, there is an excellent effect that the object of designing the limit for reducing the thickness of concrete can be effectively achieved without generating cracks on the upper and lower ends inside the side wall.

Further, a PC steel material curved inward is disposed in a mold corresponding to the top plate and the bottom plate of the box culvert including the top plate, the bottom plate, and the side wall, and concrete is driven into the mold. Tension is applied to the PC steel material to introduce prestress into the concrete structure constituting the top slab and the bottom slab, and the PC steel material is also arranged in the formwork corresponding to the side wall to apply tension after the concrete is cast. Thereby, a prestress is introduced into the concrete structure constituting the side wall to generate an outward bending moment.
Provided on the top plate and the bottom plate , if each set of PC steel is arranged in multiple stages by dividing it outside and inside with respect to the axis passing through the center in the thickness direction of the top plate and the bottom plate , P
Since the C steel material is no longer present, sheath holes that are usually provided only at the four corners are also provided on the axis thereof, so that the connecting members can be inserted and the connecting strength between the culverts can be effectively increased.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment illustrating the principle of the present invention;
The perspective view showing a sculvert.

FIG. 2 shows the state of introduction of prestress in the embodiment.
FIG.

FIG. 3 is a distribution diagram of a bending moment corresponding to FIG . 2;

FIG. 4 is a distribution diagram of internal tensile stress corresponding to FIG . 2;

FIG. 5 is a front view corresponding to FIG. 2 showing a modification.

FIG. 6 is a front view corresponding to FIG. 2 showing a modification.

FIG. 7 is a front view corresponding to FIG. 2 showing the first embodiment of the present invention .

FIG. 8 is a front view corresponding to FIG. 2, showing a second embodiment of the present invention .

FIG. 9 is a perspective view corresponding to FIG. 1 showing a conventional example.

FIG. 10 shows a state of introduction of prestress in the conventional example .
The schematic front view shown .

FIG. 11 shows a state of introduction of another prestress in the conventional example .
The schematic front view which shows a state .

FIG. 12 is a distribution diagram of a bending moment in the conventional example .

FIG. 13 is a distribution diagram of internal tensile stress in the conventional example .

[Explanation of symbols]

1, 101, 201 ... box culvert 2 ... top plate 3 ... bottom plate 4 ... side wall 5, 6, 7, 107 , 205, 206 ... PC steel material F ... tension Mp, Mq, Mr ... bending moment

Claims (2)

(57) [Claims] 1. A PC steel material which is curved inward in a mold corresponding to a top plate and a bottom plate of a box culvert composed of a top plate, a bottom plate and a side wall, and after concrete is driven into the mold, In the case where the prestress is introduced into the concrete structure constituting the top plate and the bottom plate by applying tension to the PC steel material, the P frame is also formed in the formwork corresponding to the side wall.
C steel is arranged, and approximately the center of this PC steel is divided.
The fixing part of the split part is more on the side wall than the fixing part of the upper and lower ends.
Be located outside of the axis passing through the center in the thickness direction
The box is characterized in that it is arranged in a straight line and tension is applied after the concrete is cast, whereby prestress is introduced into the concrete structure constituting the side wall to generate an outward bending moment. Calvert. 2. A PC steel material which is curved inward in a mold corresponding to the top plate and the bottom plate of a box culvert comprising a top plate, a bottom plate and a side wall, and after concrete is poured into the mold, Tension is applied to PC steel, and prestress is introduced into the concrete structure that constitutes the top and bottom slabs.
At the same time, a PC steel material is installed in the formwork corresponding to the side wall.
Tension after concrete is cast,
Of prestress into concrete structure
Generates bending moment facing outward
In the above, a plurality of the above-mentioned PC steel materials are grouped to form a top plate and
And the bottom plate, and each set of PC steel is used for the thickness of the top plate and the bottom plate.
Outward and inward with respect to the axis passing through the center of the
And a multi-stage arrangement.
X culvert.