JP2020172776A - Structure, and construction method of structure - Google Patents

Abstract

To provide a structure and the like allowing segments to be easily constructed and transported.SOLUTION: A digestion tank is a structure constructed with precast segments and comprising side walls 3 forming a closed area in a plane surface. Pre-stress is introduced to the side wall 3 by tension of a PC steel member 17 in a circumferential direction, the PC steel member 17 in the circumferential direction being arranged on an outer part of the side wall 3. Both ends 17a, 17b of the PC steel member 17 in the circumferential direction are fixed to one binding tool 40, the binding tool 40 being received in a concave part 37 arranged in the outer surface of a precast segment body without being buried in the precast segment body.SELECTED DRAWING: Figure 7

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, which makes it difficult to create dead water areas and has high agitation. 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 oval digestive tub.

When constructing a PC egg-shaped digestion tank using conventional cast-in-place concrete, it is necessary to place concrete, install heat insulating material, and apply anticorrosion coating. 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 and meridian directions 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

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. In this case, a pilaster for fixing the outer cable is provided on the side wall.

When constructing a side wall using segments, it is necessary to specially increase the thickness of the pilaster part and embed a fixing tool, so a separate formwork different from other segments is required to manufacture the segment. Alternatively, it is necessary to separately prepare the fixing tool in the mold. In addition, the thickening of the pilaster part increases the size and weight of the segment, and although the segment without the pilaster part can be transported by a small trailer, the segment with the pilaster part is included. May require a large trailer.

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 facilitates the manufacture and transportation of segments.

The first invention for solving the above-mentioned problems is a structure constructed by precast segments and having a side wall forming a closed region in a plane, and the side wall is peripherally connected by tension of a tensioning material in the circumferential direction. Directional prestress was introduced, the tensioning material was provided outside the side wall, both ends of the tensioning material were fixed to one fastener, and the tensioning member was provided on the outer surface of the precast segment body. It is a structure characterized in that it is housed in a recess without being embedded in a precast segment main body.

In the present invention, when a tension material (outer cable) in the circumferential direction is arranged outside the side wall and prestress in the circumferential direction is introduced into the side wall by the tension, both ends of the tension material are fixed to one binding tool. The binding tool is housed in a recess provided on the outer surface of the segment body, and is not embedded in the segment body. In such a structure, the pilaster as described above is not required, and the segment having the recess uses the same formwork as when manufacturing the other segment, except that the box must be removed to form the recess. It can be manufactured in the same way as the segment of No., and there is no need to put a binding tool in the formwork, and no large trailer is required for transportation.

One end of the tensioning material is passed through a hole in the binding tool and fixed at one side of the binding tool, and the opposite end of the tensioning material is inserted into another hole of the binding tool. It is desirable that it be passed through and fixed on the opposite side of the fastener.
As the binding tool, as described above, a device having a plurality of holes and fixing both ends of the tensioning material passed through the respective holes at both sides of the binding tool is used to tension and fix the tensioning material. Becomes easier.

The side wall is constructed by arranging a plurality of precast segments in the circumferential direction, the tensioning material is arranged in a plurality of stages in the vertical direction, and the precasting segment having a recess for accommodating the binding tool of the tensioning material may differ depending on the tensioning material. desirable.
As a result, the arrangement of the recesses is not overcrowded, and prestress can be introduced into the side wall in a well-balanced manner.

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.
As a result, it is 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 recess 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, the tensioning material is provided outside the side wall, both ends of the tensioning material are fixed to one binding tool, and the binding member is the outer surface of the precast segment main body. It is a construction method of a structure characterized in that it is housed in a recess provided in the precast segment without being embedded in the main body of the precast segment.
The second invention is the construction method of the structure of the first invention.

When the circumferential prestress is introduced into the side wall, one end of the tensioning material is passed through the hole of the binding tool and fixed by one side of the binding tool, and the other of the binding tool is fixed. It is desirable to tension the opposite end of the tensioning material, which is passed through the hole and pulled out from the opposite side of the binding, and is fixed at the opposite side of the binding.
As a result, the tensioning material can be easily tensioned and fixed.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a structure or the like that facilitates the production and transportation of segments.

The figure which shows the digestion tank 1. The figure which shows the outline of the side wall 3. The figure which shows the outline of segments 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 arrangement of the PC steel material 17 in the circumferential direction. The figure which shows the depression 30. The figure which shows the recess 37. The figure explaining the tension work of the circumferential PC steel material 17. 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 formation of segment 32 and the installation of segment 31. The figure which shows the gap between the segments 32 adjacent in the circumferential direction.

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 vertical cross section of the digestion tank 1. 2A and 2B are views showing an outline of the side wall 3, FIG. 2A is a perspective view of the side wall 3, and FIG. 2B 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 portion 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 apex 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 in 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 apex 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 divided 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 in 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 also has a pseudo-circumferential shape (substantially circular) formed by reducing the outer polygonal polygon (see FIG. 5 to be described later).

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.

FIG. 3A is a diagram showing an outline of the segment 31, the left figure is a view of the segment 31 along the vertical plane, and the right figure is an elevation 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.

FIG. 3B is a diagram showing an outline of the segment 32 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 surfaces 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, a tension material such as a PC steel wire can be used as a single strand.

FIG. 5 is a view showing the arrangement of the 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 this embodiment, the circumferential PC steel materials 17 are arranged in a circumferential shape. The circumferential PC steel material 17 makes one round along the outer circumference of the side wall 3, and both ends thereof are fixed (fixed) to the fastener 40 provided at one place in a state where a tension force is applied.

FIG. 6A is a diagram showing details of the range a in FIG. The segment 31 is provided with a groove-shaped recess 30 for accommodating the circumferential PC steel material 17 along the width direction of the segment 31.

FIG. 6B 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 a circumferential shape by the groove-shaped recess 30 (end surface described later). 301) 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. 6 (c) shows a cross section in the vertical direction along the line AA of FIG. 6 (a). 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. 6B). The upper surface 302 and the lower surface 303 are substantially horizontal planes arranged above and below the recess 30, respectively.

FIG. 7A is a diagram showing details of the range b of FIG. The binding tool 40 is housed in a recess 37 formed on the outer surface of the main body of the segment 31, and both ends 17a and 17b of the circumferential PC steel material 17 are fixed to both side portions of the binding tool 40, respectively. The binding tool 40 is floating from the segment 31 main body, is not embedded in the segment 31 main body, and is not fixed to the segment 31 main body.

FIG. 7B is a perspective view showing a part of the upper portion 3b of the side wall 3. The circumferential PC steel 17 is arranged in a plurality of stages in the vertical direction, but the segment 31 having the recess 37 for accommodating the binding tool 40 of the circumferential PC steel 17 can be different depending on the circumferential PC steel 17. For example, when the binding tool 40 of the circumferential PC steel material 17 in a certain stage is housed in the recess 37 of the segment 31 (31A), the binding tool 40 of the circumferential PC steel material 17 in the upper and lower stages is the segment 31 (31A). ) Can be accommodated in the recess 37 of the segment 31 at a position 180 degrees different from the above.

When the circumferential PC steel 17 is tense, as shown in FIG. 8, one end 17a of the circumferential PC 17 is passed through one hole 401 of the binder 40 and the fastener 40 is passed through a wedge (not shown) or the like. Jacking the opposite end 17b of the circumferential PC steel 17 that is passed through another hole 402 of the fastener 40 and pulled out from the opposite side of the fastener 40 while being fixed by one side. 41 makes me nervous. After that, the end portion 17b is fixed at the side portion on the opposite side of the binding tool 40, and extra length cutting is performed. The end portion 17b is fixed by using a wedge (not shown) or the like as described above. In this way, the tension work can be completed only once, and the work itself can be easily performed.

When the PC steel material 17 in the circumferential direction is tense, the binder 40 slightly moves on the recess 37 in the direction indicated by the arrow B. The length of the recess 37 (the length in the circumferential direction of the side wall 3) is determined in consideration of this movement length so that the movement of the fastener 40 is not hindered by the wall surface of the recess 37.

The moving length of the binder 40 when the circumferential PC steel material 17 is tense becomes smaller as the circumferential length of the circumferential PC steel material 17 becomes shorter. At the upper portion 3b of the side wall 3, the peripheral length of the PC steel material 17 in the circumferential direction becomes shorter as it goes to the apex, and the moving length of the binder 40 also becomes smaller. Therefore, the length of the recess 37 can be shortened toward the top end of the side wall 3.

FIGS. 5 to 8 show an example 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 also provided as an outer cable in the range on the ground surface of the lower portion 3c of the side wall 3. Be done. Therefore, the same recesses 30 and 37 as above are formed in the range on the ground surface of the segment 32, and the tensioning work of the circumferential PC steel material 17 is also performed in the same manner as above. In FIGS. 2 and 3 above, the recesses 30 and 37 are not shown.

FIG. 9 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 end portion on the opposite side 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 on the outer surfaces of 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 outer 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, etc. 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. 10A is a view showing a steel shell 60, and FIG. 10B 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. 10B, 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. 10A) 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. 11 to 13 and the like. When constructing the digestion tank 1, first, as shown in FIG. 11A, 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. 11B, 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. 14A, 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 prestress in the meridian direction is introduced into the upper and lower small segments 321 and 322 by temporary tension and fixing thereof to connect them. Adhesives (not shown) are also used 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 to form the bottom member 6 as shown in FIG. 11 (c). 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. 15A, joint members 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. 15B, 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. 12A, 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 tensioning procedure of the circumferential PC steel material 17 is as described above. Further, the notch 35 (see FIG. 9) 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 the tensioning work of the circumferential PC steel materials 17 and 18 is performed in this way, concrete is cast on the leveled concrete 13 as shown in FIG. 12 (a) 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. 12B, the excavated portion around the lower portion 3c of the side wall 3 is backfilled with 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. 13A, 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. 14B, 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. The segment 31 is arranged on the segment 32, and 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. 15A, 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. 13 (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. The tensioning procedure of the circumferential PC steel 17 is as described above.

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 the lid 7 and the steel scaffold 8 are attached to the top end of the side wall 3 as shown in FIG. The digestive tub 1 is completed by attaching the remaining necessary members. A heat insulating material or an exterior plate (not shown) is attached to the outer surface of the side wall 3, the recess 37 or the binding tool 40 is not exposed to the outside, and no separate treatment is required for the recess 37 or the binding tool 40. However, urethane spraying or a rust preventive material may be applied to the binder 40 to prevent rust, and a solidifying material such as mortar or concrete is provided in the recess 37, and the binder 40 is embedded in the solidifying material. Is also possible.

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 in 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, and the tension causes the circumferential prestress to be introduced into the side wall 3, but both ends of the circumferential PC steel material 17 are It is fixed to one binding tool 40, and the binding tool 40 is housed in a recess 37 provided on the outer surface of the main body of the segments 31 and 32, and is not embedded in the segments 31 and 32. Therefore, in the digestive tank 1 of the present embodiment, the pilaster as described above becomes unnecessary, and the segment 31 (32) having the recess 37 is another segment except that the box for forming the recess 37 needs to be removed. It can be manufactured in the same way as the other segments 31 (32) using the same formwork as when the 31 (32) was manufactured, there is no need to put the binding tool 40 in the formwork, and a large trailer is required for transportation. There is no such thing.

Further, in the present embodiment, it is not necessary to provide a bearing plate or the like on the wall surface of the recess 37 to fix the end portion of the circumferential PC steel material 17, so that the recess 37 can be made shallow. Therefore, it can be applied even to the side wall 3 having a thin wall thickness, eliminating the need for work such as burying reinforcing bars or the like near the bearing plate, and also causing interference between the jack 41 and the segment 31 when the circumferential PC steel material 17 is tense. It is unlikely to occur. Further, in the present embodiment, since the circumferential PC steel material 17 is provided so as to go around the side wall 3 once, the tensioning work can be performed at one place. Further, using the circumferential PC steel material 17 as the outer cable as in the present embodiment 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.

The binding tool 40 has a plurality of holes 401 and 402 as described above, and both ends 17a and 17b of the circumferential PC steel material 17 passed through the holes 401 and 402 are formed on both side portions of the binding tool 40, respectively. By using the one to be fixed and performing the tensioning work in the above procedure, the tension and fixing of the circumferential PC steel material 17 can be facilitated.

Further, in the present embodiment, the circumferential PC steel materials 17 are arranged in a plurality of stages in the vertical direction, and the segment 31 having the recess 37 for accommodating the binding tool 40 of the circumferential PC steel material 17 differs depending on the circumferential PC steel material 17, so that the concave portions 37 are arranged. Is not overcrowded, and prestress can be introduced into the side wall 3 in a well-balanced manner.

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, the outer cable is applied to the circumferential PC steel material 17 on the ground surface, and the recess 37 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. In addition, as described above, the inner cable may be applied to the part above the ground surface, and the outer cable can be applied to the part below the ground surface, and the fixing of the end of the inner cable is segmented. It is also possible to perform this in the recess provided on the inner surface of the main body.

Further, the structure of the binding tool 40 and the arrangement state of the binding tool 40 in the recess 37 are not limited to those described above. For example, in the present embodiment, as shown in FIG. 8, the binding tool 40 is vertically arranged so that the positions of the holes 401 and 402 are aligned in the thickness direction of the segment, but the positions of the holes 401 and 402 are vertically arranged (in FIG. 8). The binding tool 40 may be placed horizontally so as to line up (corresponding to the paper normal direction). The depth and width of the recess 37 can be determined in consideration of the arrangement state of the binding tool 40. For example, when the binding tool 40 is placed horizontally, the recess is higher than when the binding tool 40 is placed vertically as shown in FIG. The 37 is made shallow and the width of the recess 37 is increased. The width of the recess 37 means the vertical length of the recess 37.

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 cylindrical shape. Further, this 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 or 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 scaffolding 9: Foundation pile 15, 16: Longitudinal PC steel 17, 18: Circumferential PC steel 30: Depression 31, 32: Precast segment 35: Notch 36: Filler 37: Recess 40: Fastener 41: Jack 50: Fixing part 401, 402: Hole

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 tension material is provided outside the side wall and
Both ends of the tension material are fixed to one binding tool,
A structure characterized in that the binding tool is housed in a recess provided on the outer surface of the precast segment body without being embedded in the precast segment body. One end of the tensioning material is passed through a hole in the binding tool and fixed at one side of the binding tool.
The structure according to claim 1, wherein the opposite end of the tensioning material is passed through another hole of the binding and fixed at the opposite side of the binding. The side wall is constructed by arranging a plurality of precast segments in the circumferential direction.
The tension material is arranged in a plurality of stages vertically and vertically.
The structure according to claim 1 or 2, wherein the precast segment having a recess for accommodating the binding tool of the tension material differs depending on the tension material. The structure according to any one of claims 1 to 3, wherein the structure is a sludge digestion tank, and the intermediate portion in the height direction 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 4, wherein a part of the side wall is below the ground surface, and the recess is provided at a portion of the side wall on the ground surface. A method of constructing a structure having a side wall forming a closed region on a flat surface.
The step of constructing the side wall by the precast segment and
A step of introducing a circumferential prestress into the side wall due to the tension of the circumferential tension material, and
Have,
The tension material is provided outside the side wall and
Both ends of the tension material are fixed to one binding tool,
A method for constructing a structure, wherein the binding tool is housed in a recess provided on an outer surface of the precast segment body without being embedded in the precast segment body. When introducing circumferential prestress into the side wall
In a state where one end of the tensioning material is passed through the hole of the binding tool and fixed by one side of the binding tool.
To tension the opposite end of the tensioning material, which is passed through another hole in the binding and pulled out from the opposite side of the binding, and is fixed at the opposite side of the binding. 6. The construction method of the structure according to claim 6.

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