JP2020133197A - Structure and method of constructing structure - Google Patents

Abstract

To provide a structure etc., capable of preventing an outer cable from shifting in position when tensed with simple constitution.SOLUTION: A digestor is a structure which is structured with precast segments 31, 32, and has a side wall 3 forming a closed area in plane. Circumferential pre-stress is introduced into the side wall 3 by a circumferential PC steel material 17, and a groove shaped hollow 30 for accommodating the circumferential PC steel material 17 is provided on an outer surface of bodies of the segments 31, 32. The hollow 30 has an end face 301 orthogonal to a direction B in which the circumferential PC steel material 17 is to be displaced inward when tensed.SELECTED DRAWING: Figure 5

Description

The present invention relates to a structure and a construction method thereof.

As an anaerobic fermentation digestion tank for sewage sludge, there is a storage tank (hereinafter referred to as PC egg-shaped digestion tank) equipped with a stirrer inside the egg-shaped side wall made of prestressed concrete. Is excellent. Prestress is introduced into the side wall by a tension material in the circumferential direction and the meridian direction, which resists internal pressure such as hydraulic pressure and can suitably prevent liquid leakage from the PC egg-shaped digestive tub.

When constructing a PC egg-shaped digestion tank using conventional cast-in-place concrete, it is necessary to place concrete, attach heat insulating material, and apply anticorrosion coating, and for each of these operations, a complicated scaffolding along the curved surface of the egg is required. I needed it. In addition, it was difficult to construct the PC egg-shaped digestive tank because it was necessary to introduce prestress in the circumferential direction and the meridian direction on a special shape.

On the other hand, Patent Document 1 describes a PC oval digestive tank composed of precast segments (hereinafter, may be referred to as segments), and the use of such segments simplifies the construction.

Patent No. 4309835

By the way, in the PC egg-shaped digestion tank, a tension material in the circumferential direction may be arranged outside the side wall to form an outer cable from the viewpoint of workability and the like. However, as shown in FIG. 14, since the outer surface of the side wall a of the PC egg-shaped digestion tank is inclined with respect to the vertical direction, a tension material b in the circumferential direction is tentatively arranged along the outer surface of the side wall a. When the tension is applied, the tension material b in the circumferential direction tries to be displaced inward (see arrow c), and as a result, the tension material b is displaced along the inclined surface of the side wall a (see arrow d). ..

In Patent Document 1, a rib is provided at the end of the segment, and the outer cable is passed through the through hole of the rib so that the above-mentioned misalignment does not occur, but the segment has a complicated shape and a manufacturing cost is high.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a structure or the like that can prevent misalignment of an external cable when it is tense with a simple configuration.

The first invention for solving the above-mentioned problems is a structure constructed by a precast segment and having a side wall forming a closed region in a plane, and the side wall is peripheral due to tension of a tensioning material in the circumferential direction. Directional prestress is introduced, and a recess is provided on the outer surface of the precast segment body for accommodating the circumferential tension material, and the recess is the direction in which the circumferential tension material tends to be displaced inward during tension. It is a structure characterized by having planes that are substantially orthogonal to each other.

In the present invention, when a circumferential tension material (outer cable) is arranged outside the side wall and the tension introduces circumferential prestress to the side wall, the circumferential tension material is applied to the outer surface of the side wall segment body. It is housed in the provided depression. Since the recess has a surface substantially orthogonal to the direction in which the tension material in the circumferential direction tends to be displaced inward during the tension, it is possible to prevent the tension material in the circumferential direction from being displaced during tension. Since the present invention has a simple configuration in which a recess is formed on the outer surface of the segment body, the shape of the segment is not complicated. In addition, it does not require the trouble of arranging the tension material through the through hole, and the construction is easy.

It is desirable that the outer surface of the precast segment main body has an inclined surface that is inclined with respect to the vertical direction, and that the recess is provided on the inclined surface.
If the tension material in the circumferential direction is directly arranged on the inclined surface and tension is applied, the tension material is displaced along the inclined surface as described above. The present invention is particularly effective in that such misalignment can be prevented.

It is desirable that the recess is formed in a concave shape from the outer surface to the inside and has an upper surface and a lower surface.
As a result, the upper surface and the lower surface of the recess can prevent the tension material from being displaced in the circumferential direction when the tension material is tense, and the upper surface and the lower surface can position the tension material when the tension material is arranged, so that the construction accuracy is improved.

It is desirable that the outer periphery of the side wall has a polygonal shape, and the surface of the recess is formed in an arc shape in a plane.
As a result, even if the outer circumference of the side wall has a polygonal shape, the tension material in the circumferential direction can be arranged in an arc shape without requiring a separate jig.

The structure is a sludge digestion tank, and it is desirable that the middle portion in the height direction of the side wall is narrowed in a curved shape toward the top and bottom ends. It is also desirable that a part of the side wall is below the ground surface and the recess is provided on the ground surface of the side wall.
This makes it possible to form a substantially egg-shaped digestive tub having advantages such as less formation of a dead water area and high agitation. If a part of the side wall of the digestive tub is located below the ground surface, the outer cable shall be applied to the circumferential tension material on the ground surface, and the depression shall be formed on the ground surface of the side wall. Good.

The second invention is a method of constructing a structure having a side wall forming a closed region in a plane, in which the side wall is constructed by a precast segment and the side wall is subjected to a circumferential tension due to tension of a tension material in the circumferential direction. It has a step of introducing prestress, and a recess for accommodating the tension material in the circumferential direction is provided on the outer surface of the precast segment main body, and the recess will be displaced inward when the tension material in the circumferential direction is tensioned. It is a construction method of a structure characterized by having a surface substantially orthogonal to the direction to be defined.
The second invention is the construction method of the structure of the first invention.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a structure or the like that can prevent misalignment of an outer cable when it is tense with a simple configuration.

The figure which shows the digestion tank 1. The figure which shows the side wall 3. The figure which shows the segment 31 and 32. The figure which shows the arrangement of PC steel materials 15 and 16 in the meridian direction. The figure which shows the PC steel material 17 and the depression 30 in the circumferential direction. The figure which shows the PC steel material 18 in the circumferential direction and the notch 35. The figure which shows the steel shell 60 and concrete 66. The figure which shows the construction method of the digestion tank 1. The figure which shows the construction method of the digestion tank 1. The figure which shows the construction method of the digestion tank 1. The figure explaining the groundwork of segment 32 and the installation of segment 31. The figure which shows the gap between the segments 32 adjacent in the circumferential direction. Example of depression 30. The figure explaining the movement of the tension material b.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

(1. Digestion tank 1)
FIG. 1 is a diagram showing a digestion tank 1 according to an embodiment of the present invention, and is a view of a vertical cross section of the digestion tank 1. 2 (a) is a perspective view showing the side wall 3, and FIG. 2 (b) is a view of the side wall 3 as viewed from above.

The digestion tank 1 is a structure provided in a sewage treatment plant or the like, and is a storage tank for storing sewage inside. In the digestion tank 1, sewage sludge is treated by anaerobic digestion. A stirrer (not shown) is provided inside the digestion tank 1 in order to efficiently treat sludge.

The digestion tank 1 is a PC egg-shaped digestion tank having a substantially egg-shaped shape as a whole, and includes a side wall 3, a pedestal concrete 5, a bottom member 6, a lid 7, a steel scaffold 8, and the like. The digestion tank 1 is a semi-underground storage tank, and a part of the lower part 3c of the side wall 3 and the pedestal concrete 5 are buried under the ground surface.

The side wall 3 is a substantially egg-shaped tubular member made of concrete that narrows toward the top end and the bottom end. More specifically, the intermediate portion 3a in the height direction of the side wall 3 bulges outward in a spherical shape, and the upper and lower portions of the intermediate portion 3a are narrowed in a truncated cone shape toward the top and bottom ends.

When looking at the vertical surface, the inner surface of the intermediate portion 3a of the side wall 3 bulges in an arc shape from the center C at the center in the height direction of the side wall 3 with a predetermined radius of curvature R and a central angle α to the top and bottom ends. The inner surfaces above and below the intermediate portion 3a are narrowed in a curved line toward the apex and the bottom, respectively, in a straight line smoothly continuous with the above arc. In the present embodiment, the central angle α is 90 °, the inclination angles β of the upper and lower inner surfaces of the intermediate portion 3a are 45 ° with respect to the horizontal direction, and the inner surface of the side wall 3 is up and down with respect to the center in the height direction of the side wall 3. It is symmetrical, but not limited to this.

The side wall 3 is divided into upper and lower parts at a position where the distance from the central axis O on the plane of the side wall 3 is maximum, that is, at the center of the side wall 3 in the height direction. The upper portion 3b and the lower portion 3c of the side wall 3 are configured by arranging a plurality of precast segments 31 and 32 in the circumferential direction of the side wall 3.

The segment 32 of the lower portion 3c of the side wall 3 is further divided into small segments 321 and 322. The division positions of the upper and lower small segments 321 and 322 correspond to the intersection of the line segment L extending from the center C and inclined downward at an inclination angle β / 2 with respect to the horizontal direction and the side wall 3.

As described above, the side wall 3 is a tubular member and forms a closed region in a plane. Further, the shape of the outer circumference of the side wall 3 is a pseudo-circumferential shape (substantially circular shape) formed by a polygon in consideration of ease of manufacturing of the segments 31 and 32 (see FIG. 2B). The inner circumference of the side wall 3 is also a pseudo-circumferential shape (substantially circular) formed by reducing the outer peripheral polygon.

As shown in FIG. 2B, the segment 31 of the upper portion 3b of the side wall 3 has a shape in which the upper portion 3b of the side wall 3 is equally divided in the circumferential direction in a radial vertical plane passing through the central axis O. Some segments 31 (see P in FIG. 2B) are thicker outward than the other segments 31, which are used as pilasters to anchor the ends of the circumferential PC steel 17 (see FIG. 1). Be done.

The left figure of FIG. 3A is a view of the segment 31 (segment 31 other than the pilaster P) along the vertical plane, and the right figure is an elevational view of the segment 31. The segment 31 has an elongated shape having a vertical length larger than the left and right width (the length in the circumferential direction of the side wall 3), and the width of the main body becomes narrower toward the upper end.

The segment 32 of the lower portion 3c of the side wall 3 also has a shape in which the lower portion 3c of the side wall 3 is equally divided in the circumferential direction in a radial vertical plane passing through the central axis O. Further, the upper part of some segments 32 (see P in FIG. 2A) is thickened outward from the upper parts of the other segments 32, and the end portion of the circumferential PC steel 17 (see FIG. 1) is fixed. Used as a pilaster.

FIG. 3B is a diagram showing the segment 32 (segment 32 other than the pilaster P) in the same manner as in FIG. 3A. The segment 32 also has an elongated shape having a vertical length larger than the left and right width, and the width of the main body becomes narrower toward the lower end.

At the upper end of the small segment 321 is formed a widening portion 321a that widens outward in a stepwise manner. A widening portion 322a that widens in a stepwise manner is also formed at the upper end of the small segment 322. The lower surface of the small segment 321 has the same thickness as the upper surface of the small segment 322, and the inner and outer surfaces of both segments 321 and 322 are smoothly continuous.

Precast concrete members manufactured in advance by casting concrete into a formwork or the like are used for the segments 31 and the small segments 321 and 322. The small segments 321 and 322 can be manufactured at once by dividing the internal space of one formwork into two by a partition such as an iron plate and placing concrete in each of the divided spaces. When constructing the digestion tank 1, anticorrosion coating may be applied to the inner surfaces of these segments in advance, and a heat insulating material (not shown) may be attached to the outer surface of the segments in advance.

Inside the segments 31 and 32, the meridian direction PC steel materials 15 and 16 are arranged. The meridian direction PC steel materials 15 and 16 are tension members arranged in the meridian direction of the side wall 3, and for example, a PC steel rod is used. FIG. 4 shows the arrangement of the PC steel materials 15 and 16 in the meridian direction on the elevations of the segments 31 and 32 that are continuous vertically.

A plurality of PC steel materials 15 in the meridian direction are passed through the segment 31. The lower end of each meridian direction PC steel 15 penetrates the widening portion 321a at the upper end of the segment 32 and is fixed on the lower surface of the widening portion 321a.

On the other hand, the fixing position of the upper end of each meridian direction PC steel material 15 is different, and the upper end of the meridian direction PC steel material 15 located at the center in the width direction of the segment 31 is fixed at the upper end of the segment 31, but the meridians on both sides thereof. The upper end of the directional PC steel 15 is fixed in the segment 31 at a lower position as the distance from the central portion is increased. This is to prevent overcrowding of the meridian direction PC steel material 15 at the upper end of the segment 31.

A plurality of PC steel materials 16 in the meridian direction are passed through the segment 32. The upper end of each meridian direction PC steel 16 is fixed at the upper end of the segment 32. On the other hand, the fixing position of the lower end of each meridian direction PC steel material 16 is different, and the lower end of the meridian direction PC steel material 16 in the central portion in the width direction of the segment 32 protrudes from the lower end of the segment 32 and is fixed at the lower end. , The lower ends of the meridian direction PC steel 16 on both sides thereof are fixed in the segment 32 at a higher position as the distance from the central portion is increased. The purpose is to prevent the meridian direction PC steel 16 from being overcrowded at the lower end of the segment 32, as described above.

Circumferential PC steel materials 17 and 18 are also provided on the side wall 3. The circumferential PC steel 17 is provided outside the side wall 3 as an outer cable, and the circumferential PC steel 18 is provided inside the side wall 3 as an inner cable. As the circumferential PC steel materials 17 and 18, tension materials such as PC steel wires can be used.

FIG. 5A is a view showing a circumferential PC steel material 17 provided on the upper portion 3b of the side wall 3, and is a horizontal cross section of the upper portion 3b of the side wall 3.

In the present embodiment, the circumferential PC steel material 17 is arranged in an arc shape along the outer circumference of the side wall 3. The end portion of the circumferential PC steel material 17 penetrates the segment 31 of the pilaster P from one side surface and is fixed by the fixing portion 40 on the other side surface of the segment 31. A fixing portion 40 for fixing the other end portion of the circumferential PC steel material 17 or the end portion of the other circumferential PC steel material 17 is also provided on the one side surface of the segment 31 of the pilaster P. Within the segment 31 of P, the circumferential PC steel materials 17 are arranged so as to intersect with each other.

In the segment 31 other than the pilaster P, a groove-shaped recess 30 for accommodating the circumferential PC steel material 17 is provided along the width direction of the segment 31.

FIG. 5B is a diagram showing a plane of the segment 31 at the height of the recess 30. The plane of the segment 31 main body is substantially trapezoidal, and its outer surface is basically linear, but an arc surface for arranging the circumferential PC steel material 17 in an arc shape by the groove-shaped recess 30 (end surface 301 described later). ) Is formed on the outer surface of the segment 31 main body. In the present embodiment, two recesses 30 are formed on both sides of the segment 31 in the width direction, but one recess 30 may be formed so as to be continuous over the entire width of the segment 31.

FIG. 5C shows a cross section in the vertical direction along the line AA of FIG. 5A. The recess 30 is formed in a concave shape from the outer surface of the segment 31 toward the inside, and has an end surface 301, an upper surface 302, and a lower surface 303. The end surface 301 is a substantially vertical surface on the innermost side of the recess 30, and is formed in an arc shape in a plane to form the arc surface (see FIG. 5B). The upper surface 302 and the lower surface 303 are substantially horizontal planes arranged above and below the recess 30, respectively.

When the circumferential PC steel 17 is strained to introduce prestress, the circumferential PC steel 17 tends to be displaced in the substantially horizontal direction indicated by the arrow B so as to be tightened inward. The outer surface of the segment 31 main body is inclined with respect to the vertical direction, and becomes an inclined surface toward the inside as it goes upward. However, the end surface 301 is a substantially vertical surface and is orthogonal to the direction indicated by the arrow B. ..

FIGS. 5A to 5C are examples of the circumferential PC steel material 17 provided on the upper portion 3b of the side wall 3, but the circumferential PC steel material 17 is similarly provided in the range on the ground surface of the lower portion 3c of the side wall 3. It is provided as an outer cable, and a groove-shaped recess 30 similar to the above is formed in the segment 32. FIG. 5D is a diagram showing the recess 30 in the same manner as in FIG. 5C, and has an end surface 301, an upper surface 302, and a lower surface 303 as described above. However, the length of the upper surface 302 (the radial length of the side wall 3) is larger than that of the lower surface 303, and in this respect, the length of the upper surface 302 is smaller than that of the lower surface 303, which is different from the recess 30 in FIG. 5 (c). In addition, in FIGS. 2 and 3 above, the illustration of these depressions 30 is omitted.

FIG. 6 is a diagram showing a circumferential PC steel material 18 provided in the lower portion 3c of the side wall 3 below the ground surface. The circumferential PC steel 18 is passed through a sheath pipe (not shown) inside the side wall 3, and its end is fixed by a fixing portion 50 on one side surface of the segment 32. Further, a fixing portion 50 is also provided on the other side surface of the segment 32, and the other end portion of the circumferential PC steel material 18 or the end portion of the other circumferential PC steel material 18 is fixed. Within the segment 32, the circumferential PC steel materials 18 are arranged so as to intersect with each other.

In the segments 32 on both sides of the segment 32, notches 35 are formed at the ends on the fixing portion 50 side, respectively, and a space for tensioning the circumferential PC steel material 18 is secured. The notch 35 is filled with a filler 36 such as concrete after tensioning work, and the inner surface is smoothed.

The circumferential PC steel material 18 is arranged as an inner cable under the ground surface, except that the meridian direction PC steel material 15 is also provided at the widening portion 321a at the upper end of the segment 32 on the ground surface. A similar inner cable is arranged for the purpose of avoiding interference from the viewpoint of balance with the above (see FIG. 1).

The pedestal concrete 5 is provided around the lower portion 3c of the side wall 3 and is formed so as to have a mortar-shaped recess for accommodating the lower portion 3c of the side wall 3.

The bottom member 6 is a mortar-shaped member arranged below the segment 32 in the lower portion 3c of the side wall 3. The bottom member 6 is formed by filling a steel shell with concrete, and constitutes the bottom surface of the internal space of the side wall 3. The inner surface of the bottom member 6 has the same inclination as the inner surface of the bottom end of the side wall 3, and is smoothly continuous with the inner surface.

FIG. 7A is a view showing a steel shell 60, and FIG. 7B is a vertical sectional view showing a state in which the steel shell 60 is filled with concrete 66. The steel shell 60 is a mortar-shaped box-shaped member having a bottom plate 61 and partition plates 62, 63, 64, 65.

The bottom plate 61 is a plate material provided so as to be inclined with respect to a horizontal plane, and a plurality of bottom plates 61 are arranged in a mortar shape along the circumferential direction of the steel shell 60.

The partition plate 62 is a plate material provided at the lower end of each bottom plate 61, and is arranged so as to extend upward from the lower end. In the steel shell 60, a plurality of partition plates 62 are arranged in a tubular shape along the circumferential direction of the steel shell 60.

The partition plates 63 and 64 are plate materials provided at the middle portion and the upper end of the bottom plate 61 in the vertical direction, respectively, and are arranged so as to be orthogonal to the bottom plate 61 along the circumferential direction of the steel shell 60. In the steel shell 60, a plurality of partition plates 63 and 64 are arranged in an annular shape along the circumferential direction of the steel shell 60, and the partition plate 64 is provided with a hole 641 for passing the lower end of the PC steel material 16 in the meridian direction.

The partition plate 65 is a plate material arranged so as to be orthogonal to the bottom plate 61 along the vertical direction of the steel shell 60. In the steel shell 60, a plurality of partition plates 65 are provided radially so as to intersect the partition plates 62, 63, 64.

As shown in FIG. 7B, the concrete 66 is filled so that a predetermined cover is secured for the steel shell 60. When filling the concrete 66, a box punching portion 661 is formed in the vicinity of the hole 641 (see FIG. 7A) of the partition plate 64 to secure a space for performing the work related to the main tension of the meridian direction PC steel material 16. Then, after the main tension of the PC steel material 16 in the meridian direction, the box punching portion 661 is filled with a filler 662 such as concrete.

The lid 7 is provided in the opening at the top of the side wall 3. A stirrer (not shown) is attached to the lid 7. The steel scaffold 8 is a scaffold for work provided around the lid 7.

(2. Construction method of digestion tank 1)
Next, the construction method of the digestion tank 1 will be described with reference to FIGS. 8 to 10 and the like. When constructing the digestion tank 1, first, as shown in FIG. 8A, the foundation pile 9 is driven and the ground 2 is excavated. Then, leveling concrete 13 is placed on the bottom surface of the excavated portion of the ground 2.

After that, as shown in FIG. 8B, the steel shell 60 is arranged at the center of the bottom surface of the excavated portion, and the segment 32 is installed around the steel shell 60 to assemble the lower portion 3c of the side wall 3. The segment 32 is arranged by supporting the lower surface of the widening portion 322a with the support member 14. The height of the lower surface corresponds to the position of the center of gravity of the segment 32, and the stability against an earthquake or the like is improved during the construction of the digestion tank 1. Even after the digestion tank 1 is completed, high stability can be obtained by supporting the lower surface with the pedestal concrete 5.

In the present embodiment, the upper and lower small segments 321 and 322 are grounded at the site and integrated into a segment 32, and then the segment 32 is installed. As shown in FIG. 11A, the small segment 322 is preliminarily charged with the PC steel material 160 in the meridian direction, and the PC steel material 160 projects from the upper end thereof.

When the small segments 321 and 322 are grounded, the small segment 321 is connected to the upper surface of the small segment 322. At this time, the protruding portion of the PC steel material 160 described above is connected to the PC steel material 160 passing through the sheath pipe (not shown) of the small segment 321 by using the joint 161. These PC steel materials 160 constitute the above-mentioned meridian direction PC steel material 16, and prestresses in the meridian direction are introduced into the upper and lower small segments 321 and 322 by temporary tension and fixing thereof to connect them. Adhesive with an adhesive (not shown) is also performed between the small segments 321 and 322.

When installing the segment 32, pass the lower end of the meridian direction PC steel 16 (see FIG. 4) protruding from the lower end of the segment 32 (small segment 322) through the hole 641 of the partition plate 64 of the steel shell 60, and use a dead anchor or the like. Connect to the partition plate 64. After the segment 32 is installed, the concrete 66 is cast on the steel shell 60 as shown in FIG. 8C to form the bottom member 6. The steel shell 60 positions the segment 32 at the time of installation and also functions as a reinforcing material for the bottom member 6. At this point, the box-extracting portion 661 is left unfilled.

Further, as shown as a schematic view in FIG. 12 (a), joint materials 33 are provided inside and outside in the gaps between the segments 32 adjacent to each other in the circumferential direction of the side wall 3, and grout 34 (hardened material) is filled between them. .. As the joint material 33, for example, a resin having sulfuric acid resistance or the like is used. Further, at the position of the sheath tube of the segment 32, as shown in FIG. 12B, a bag in which the opening of the sheath tube 320 exposed in the gap is expanded by gas or the like so that the grout 34 does not flow into the sheath tube. It is closed in advance by the body 70. The bag body 70 is shrunk and removed after the grout 34 is cured.

Next, the main tension of the meridian direction PC steel material 16 of each segment 32 is performed, and the meridian direction prestress is introduced into the lower portion 3c of the side wall 3. The box punching portion 661 is filled after the main tension of the PC steel material 16 in the meridian direction.

Further, as shown in FIG. 9A, the circumferential PC steel materials 17 and 18 are arranged as described above, and the tension causes the circumferential prestress to be introduced into the lower portion 3c of the side wall 3. The notch 35 (see FIG. 6) of the segment 32 is filled with a filler 36 such as concrete after the tensioning work of the circumferential PC steel 18 is completed.

After that, as shown in FIG. 9A, concrete is cast on the leveled concrete 13 to construct the pedestal concrete 5. A connecting material (not shown) such as a gibber is attached to the outer surface of the segment 32, whereby the lower portion 3c of the side wall 3 and the pedestal concrete 5 are integrated (rigidly connected). The connecting member may be attached after the segment 32 is installed, or may be attached to the segment 32 in advance. Since the casting of the pedestal concrete 5 is a reverse casting operation with the formwork installed, it is desirable that the concrete contains a leavening agent or the like in order to improve the solidity.

Further, if necessary, a stage (not shown) is provided on the bottom member 6 inside the side wall 3, an aerial work platform is operated on the stage, and work such as painting and joint treatment is performed on the inner surface of the lower portion 3c of the side wall 3. I do.

Then, as shown in FIG. 9B, the excavated portion around the lower portion 3c of the side wall 3 is backfilled with the backfill soil 21, and the center tower 22 for aerial work is installed on the bottom member 6. Remove the above stages and aerial work platforms in advance.

Next, as shown in FIG. 10A, the segment 31 of the upper portion 3b of the side wall 3 is installed on the segment 32 of the lower portion 3c of the side wall 3 to assemble the upper portion 3b of the side wall 3. As shown in FIG. 11B, a PC steel material 150 in the meridian direction is preliminarily charged in the segment 31 as an unbonded steel material, and a joint 151 is provided at the lower end of the PC steel material 150 in the vicinity of the lower surface of the segment 31. After arranging the segment 31 on the segment 32, the PC steel material 150 in the meridian direction passed through the through hole (not shown) of the widening portion 321a of the segment 32 is connected to the joint 151. These PC steel materials 150 constitute the meridian direction PC steel material 15 of the present embodiment. Further, as in the example of FIG. 12A, the joint material 33 and the grout 34 are provided in the gap between the adjacent segments 31.

After the assembly of the upper portion 3b of the side wall 3 is completed, the circumferential PC steel material 17 is arranged as shown in FIG. 10 (b), and the tension between the meridian direction PC steel material 15 and the circumferential direction PC steel material 17 causes the circumference to the upper portion 3b of the side wall 3. Introduce directional and meridian prestress.

If necessary, work such as internal painting and joint treatment is performed on the inner surface of the upper portion 3b of the side wall 3, the center tower 22 is removed, and as shown in FIG. 1, the lid 7 and the steel scaffolding 8 are attached to the top end of the side wall 3. The digestive tank 1 is completed by attaching the remaining necessary members.

As described above, in the present embodiment, by forming the side wall 3 of the digestion tank 1 with the precast segments 31 and 32, the scaffolding required for the construction of the conventional digestion tank using cast-in-place concrete at the time of construction of the side wall 3 can be obtained. It can be reduced to a minimum, and insulation can be installed and anticorrosion coating can be applied at the factory or on the ground before installation of segments 31 and 32. Therefore, the construction of the side wall 3 becomes easy, which contributes to shortening the construction period and reducing the cost. In addition, even an inexperienced worker can easily perform the construction, and it is easy to ensure the quality.

Further, in the present embodiment, the circumferential PC steel material 17 (outer cable) is arranged outside the side wall 3, thereby introducing the circumferential prestress to the side wall 3, but the circumferential PC steel material 17 is a segment of the side wall 3. It is housed in the recess 30 provided on the outer surface of the 31 and 32 main bodies. Since the recess 30 has an end face 301 orthogonal to the direction B (see FIGS. 5C and 5D) in which the circumferential PC steel 17 tends to be displaced inward when the circumferential PC steel 17 is tense, the circumferential PC steel 17 is tense. It is possible to prevent the displacement of time. It should be noted that using the circumferential PC steel 17 as an outer cable is excellent not only in workability but also in that the compressed cross section of the side wall 3 at the time of introducing prestress can be increased.

Since the present embodiment has a simple configuration in which the recess 30 is formed on the outer surface of the main bodies of the segments 31 and 32, the shapes of the segments 31 and 32 are not complicated. In addition, it does not take time and effort to arrange the PC steel material 17 in the circumferential direction through the through hole, and the construction is easy.

Further, the segments 31 and 32 have an inclined surface that is inclined with respect to the vertical direction. In the present embodiment, the recess 30 is provided on the inclined surface, so that the circumferential PC steel material 17 is directly arranged on the inclined surface. It is particularly effective in that it is possible to prevent the circumferential PC steel material 17 from being displaced along the inclined surface when tension is applied.

Further, since the recess 30 is formed in a concave shape having an upper surface 302 and a lower surface 303, the upper surface 302 and the lower surface 303 can also prevent the displacement of the PC steel material 17 in the circumferential direction during tension, and the upper surface 302 and the lower surface 303 can prevent the recess 30 from being displaced. Since the directional PC steel material 17 can be positioned at the time of arrangement, the construction accuracy is also improved.

Further, in the present embodiment, the outer circumference of the side wall 3 is polygonal, which makes it easy to manufacture the segments 31 and 32, and the end face 301 of the recess 30 is formed in an arc shape on a flat surface. Even so, the circumferential PC steel 17 can be arranged in an arc shape without requiring a separate jig.

Further, the digestive tank 1 of the present embodiment has a substantially oval shape in which the intermediate portion 3a of the side wall 3 narrows in a curved shape toward the top end and the bottom end, so that a dead water area is hard to be formed and the agitation is high, and scum and the like can be removed. It has advantages such as being easy. Further, in the present embodiment, since a part of the side wall 3 of the digestion tank 1 is located below the ground surface, it is decided to apply the outer cable to the circumferential PC steel material 17 on the ground surface, and the recess 30 is the side wall. It is formed in the part on the ground surface of 3.

However, the present invention is not limited to this. For example, in the digestion tank 1, the entire side wall 3 may be located on the ground surface, and in such a case, the outer cable can be applied to the entire side wall 3 in the height direction.

Further, the shape of the recess 30 is not limited to that described above, and may be, for example, one without an upper surface 302 or one without a lower surface 303 as shown in FIG. 13 (a). Further, the outer surface of the side wall 3 is not limited to the inclined surface, and may be formed in the vertical direction as shown in FIG. 13 (b).

In addition, as shown in the left figure of FIG. 13C, the end face 301 may have an arc shape along the outer circumference of the circumferential PC steel material 17. The right figure of FIG. 13C is an enlargement of the intersection D between the direction B and the end face 301 where the circumferential PC steel 17 tends to move inward when tensioned. In this case as well, it is almost the same as the direction B. Orthogonal planes are formed near the intersection D of the direction B and the end face 301. In the present invention, "having substantially orthogonal planes" means that such an arcuate end face 301 is also included.

Further, the shapes of the segments 31 and 32 are determined in consideration of the minimum bending radius of the PC steel materials 17 and 18 in the circumferential direction, the required cover of the PC steel material, the required strength of the segment, the transportability, the workability, etc., and are limited to the above. There is nothing. For example, by making these segments 31 and 32 have the same shape, the segments 31 and 32 can be manufactured using one type of mold, and the mold cost required for manufacturing the segments 31 and 32 can be reduced.

Further, in the present embodiment, the joint material 33 and the grout 34 made of resin or the like are provided in the gaps between the segments adjacent to each other in the circumferential direction, and prestress in the circumferential direction is introduced after the grout 34 is cured, but water is used as the joint material 33. It is also possible to provide an expandable waterproof rubber, narrow the gap between adjacent segments by introducing prestress in the circumferential direction, crush the waterproof rubber, and then fill the grout 34. ..

Further, in the present embodiment, the meridian direction PC steel materials 15 and 16 are formed by connecting the PC steel materials 150 and 160 with the joints 151 and 161. However, the meridian direction PC steel materials 15 and 16 are formed by one PC steel material. You may. For example, when the meridian direction PC steel material 15 is composed of one PC steel material, the protruding portion of the meridian direction PC steel material 15 protruding from the lower end of the segment 31 is passed through the through hole of the widening portion 321a of the segment 32 when the segment 31 is installed. It is possible to place it. Further, when the meridian direction PC steel material 16 is composed of one PC steel material, the protruding portion of the meridian direction PC steel material 16 protruding from the upper end of the small segment 322 is the sheath pipe of the small segment 321 when the small segments 321 and 322 are grounded. It is possible to connect the upper and lower small segments 321 and 322 by passing through (not shown) and temporarily tensioning and fixing the segments.

Further, although the example of the PC oval digestive tank has been described in this embodiment, the shape of the side wall 3 is not limited to the oval shape, and may be, for example, a spherical shape. Further, the present embodiment can be applied not only to the digestion tank 1 but also to various storage tanks, and can be applied to structures other than the storage tank as long as it has a side wall 3 forming a closed region on a flat surface.

Further, in the present embodiment, the lower portion 3c of the side wall 3 and the pedestal concrete 5 are connected by a gibber or the like to form a rigid connection, but the lower portion 3c of the side wall 3 may be non-rigid to the pedestal concrete 5. .. The non-rigid state means a state in which shear force and moment are not substantially transmitted between the lower portion 3c of the side wall 3 and the pedestal concrete 5, and "substantially" means friction and adhesion of concrete. It means, except for the transmission of minute force through.

Further, in the present embodiment, the segment 32 of the lower portion 3c of the side wall 3 is divided into upper and lower small segments 321 and 322, and the segment 32 becomes large in the large-sized digestion tank 1 and there is a problem in terms of transportation and installation. It is effective for such things. However, if there is no such problem, the segment 32 may be manufactured as an integral unit from the beginning. On the other hand, it is also possible to divide the segment 31 of the upper portion 3b of the side wall 3 into upper and lower small segments as in the segment 32.

Although preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the technical idea disclosed in the present application, and these also naturally belong to the technical scope of the present invention. Understood.

1: Digestion tank 2: Ground 3: Side wall 5: Pedestal concrete 6: Bottom member 7: Lid 8: Steel scaffold 9: Foundation pile 13: Leveling concrete 15, 16: Warp direction PC steel material 17, 18: Circumferential direction PC steel 30: dent 31, 32: precast segment 33: joint material 34: grout 35: notch 36, 662: filler 40, 50: fixing part 60: steel shell 66: concrete 70: bag 301: end face 302: Upper surface 303: Lower surface 321 and 322: Small segments 321a and 322a: Widening portion 641: Hole 661: Boxing portion

Claims (7)

A structure constructed of precast segments and having side walls forming a closed region in a plane.
Circumferential prestress is introduced into the side wall by the tension of the circumferential tension material.
The outer surface of the precast segment body is provided with a recess for accommodating the tension material in the circumferential direction.
The recess is a structure having a surface substantially orthogonal to the direction in which the tension material in the circumferential direction tends to be displaced inward at the time of tension. The structure according to claim 1, wherein the outer surface of the precast segment main body has an inclined surface that is inclined with respect to the vertical direction, and the recess is provided on the inclined surface. The structure according to claim 1 or 2, wherein the recess is formed in a concave shape from the outer surface to the inside, and has an upper surface and a lower surface. The structure according to any one of claims 1 to 3, wherein the outer periphery of the side wall has a polygonal shape, and the surface of the recess is formed in an arc shape in a plane. The structure is any of claims 1 to 4, wherein the structure is a sludge digestion tank, and the height-wise intermediate portion of the side wall is narrowed in a curved shape toward the top end and the bottom end. The structure described. The structure according to claim 5, wherein a part of the side wall is below the ground surface, and the depression is provided at a portion on the ground surface of the side wall. A method of constructing a structure having a side wall forming a closed region on a flat surface.
The process of constructing the side wall with precast segments and
A step of introducing a circumferential prestress into the side wall due to the tension of the circumferential tension material, and
Have,
The outer surface of the precast segment body is provided with a recess for accommodating the tension material in the circumferential direction.
A method for constructing a structure, wherein the recess has a surface substantially orthogonal to the direction in which the tension material in the circumferential direction tends to be displaced inward at the time of tension.

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