JP2001200652A - Prestressing method for egg-shaped concrete vessel structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give a predetermined tension force in the peripheral direction even if an amount of PC tension material and the number of anchor devices are reduced, in an egg-shaped concrete vessel structure 1. SOLUTION: A plurality of grooves 20 are provided in the direction of meridian on a wall face, and a spiral PC tension member insertion duct is formed in a shell wall thickness so as to pass through the grooves 20. A PC tension member 10 is inserted over the whole length of the duct, one end of the PC tension member 10 is fixed, the PC tension member is gripped in the grooves 20 to tense it sequentially, and it is finally fixed at a terminal of the other end of the PC tension member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for introducing prestress into an egg-shaped concrete container structure suitably used for a sewage digestion tank or the like.

[0002]

2. Description of the Related Art In recent years, the use of a concrete egg type digestion tank having excellent shape and function as a digestion tank in a treatment plant for domestic sewage and sewage in urban areas has increased. ing. This digestion tank is composed of a drooping bottom buried in the ground and an upper standing part standing on the ground with the remaining part being constructed on a ring base supported by foundation piles.

[0003] The wall, which is the shell of the digestion tank in the upper standing portion, has a PC structure in which prestress is introduced into the wall in order to counter hoop tension due to the internal pressure of sewage. When prestress is introduced into this wall, a plurality of boat-shaped depressions are formed on the outer surface of the wall of the upper standing portion, and the circumference PC in one parallel direction is formed.
A structure in which a tension member is disposed within the shell wall thickness, and both ends of the PC tension member are crossed by the recessed portion, and tension is fixed at both ends of the PC tension member, thereby introducing circumferential prestress into the container wall. It has become. In this structure, the prestress introduction efficiency is reduced due to the friction between the PC tendon and the insertion duct, so that a large amount of PC steel is used, and the fixing is performed for each rotation, so that a large number of expensive fixing tools are required. . In addition, the need for a reinforcing steel material to withstand the stress concentration in the fixing portion, and the necessity of filling in the recessed portion of the fixing portion have caused the construction cost to rise.

On the other hand, since the bottom wall of the hanging bottom is buried in the ground and the outer surface of the wall is in contact with the ground, it is not possible to provide a fixing portion on the outer surface of the wall like the upper standing portion. Therefore, many P
There is known a PC structure in which a C steel material is arranged in a helical shape, and a fixing portion is provided in concrete and inside the wall.

Japanese Patent Application Laid-Open No. Sho 62-271881 proposes a technique in which a hanging bottom portion is changed to a structure that can be easily constructed and a reinforced concrete structure is formed. In other words, the egg-shaped wall has a prestressed concrete structure, the foundation has a reinforced concrete structure, and the middle frame has a prestressed reinforced concrete structure. However, the reinforced concrete structure requires huge concrete, the wall thickness is increased, and the stress transmission is complicated, and it cannot be said that the structure has always been improved.

[0006] On the other hand, the present applicant has disclosed Japanese Patent Application Laid-Open No. 9-31918.
Japanese Patent Application Laid-Open Publication No. H11-157, discloses a tension fixing method of a PC tension member that can be used with a minimum number of fixing tools. The technique is a technique for reinforcing an existing columnar structure. A curved panel is provided around the columnar structure via a mortar, and a PC tendon is spirally inserted into and wound around the curved panel plate, and the PC is wound. Attach one end of the tendon (cable) to the lower or upper part of the curved panel,
This is a technique in which a jack is inserted into a slit between curved panels from a locking point, and a PC tendon material exposed in the slit is sequentially tensioned toward the other end of the cable to introduce a tightening force to a structure. In the above technique, the use of expensive fixing tools is minimized, and the tension can be reliably fixed. The above technique is a technique for tightening a structure serving as a core to reinforce the core structure.

[0007]

SUMMARY OF THE INVENTION The present invention basically follows the superior technology that the egg-shaped structure is a prestressed concrete structure, and uses as little PC tendon material and fixing device as possible. This has led to the creation of a pre-stress introduction technology that can be reduced in cost without requiring reinforcement of individual fixing sections and filling in the many traces of depressions. That is, as a result of earnest research on a technique for introducing a prestress in the circumferential direction of the wall, the technique disclosed in Japanese Patent Application Laid-Open No. 9-31918 is referred to, and a circumferential prestress that can be constructed with a minimum number of fixing tools is referred to. The introduction method was developed. An object of the present invention is to provide such a technique.

[0008]

SUMMARY OF THE INVENTION The present invention has been developed to solve the above problems. The technical means, when constructing an egg-shaped concrete container structure, forms a spiral PC tendon insertion duct in the shell wall thickness, forms a number of intermediate tension portions in the middle, and establishes a PC tension in this duct. One end of the PC tendon material is fixed to the fixing portion, and the PC is sequentially inserted from the fixing portion toward the other end by the intermediate tension portion.
Provided is a method for introducing prestress into an egg-shaped concrete container structure, wherein a tendon is strained and finally set at the other end of the PC tendon.

The present invention is applied to an upright-constructed egg-shaped concrete container structure, and basically comprises the following (a),
(B). (A) To form a PC tendon insertion duct having a spiral shape in the circumferential direction (lattice) continuous over the entire length of the prestress introduction area of the shell wall. (B) A long PC tendon is inserted into the duct, one end of the PC tendon is fastened to the terminal fixing body at one end of the prestress introduction area, and the PC is moved toward the other end of the prestress introduction area.
Tensioning the tendon sequentially, and finally fixing the PC tendon at the other end.

In order to achieve the above (b), an intermediate tension portion is provided in the middle of the PC tension member insertion duct. In the present invention, the term "intermediate tension portion" refers to a portion that grips the middle portion of the PC tendon material with a jack or the like to partially apply tension to the PC tendon material. For example, a concave portion provided on a wall surface, which has a size capable of exposing the PC tendon material therein and operating the jack, and having a reaction force support portion of the jack formed on the inner surface.

The intermediate tension portion can be constituted by one or a plurality of grooves provided in the meridian direction of the eggshell wall surface. When formed in this way, the intermediate tension portion having an appropriate shape and arrangement can be extremely easily formed. It can be formed and is suitable.

Further, the prestress introduction area is divided into an upper standing portion of the egg-shaped structure and a drooping bottom buried in the ground, and tension is introduced by at least two separate strain members for PC. It is preferable that In that case, the first system is
One or more grooves are provided in the meridian direction of the outer surface of the wall of the upper standing portion, and a long helical PC tension which is open to the side surface of the groove within the wall thickness and is continuous over the entire length of the upper standing portion. A material insertion duct is formed, and a continuous PC strainer is inserted into the duct, one end of the PC strainer is fastened to the terminal fixing body, and the other end of the PC strainer is inserted into the groove. The PC tendons exposed to the outside are grasped sequentially by a plurality of jacks inserted at different positions in the groove, and the jacks are alternately actuated and gradually tensioned sequentially, and the other end of the PC tendon The system will be the one that finally fixes at the end. In the second system, one or a plurality of grooves are provided in the meridional direction of the inner wall of the hanging bottom buried in the ground, and the wall is opened to the side surface of the groove within the wall thickness and extends over the entire length of the wall of the hanging bottom. And a continuous spiral PC tendon insertion duct is formed, a continuous long PC tendon is inserted into the duct, one end of the PC tendon is attached to the terminal fixing member, and the other end of the PC tendon is inserted. , The PC tendon material exposed in the groove is gripped by a plurality of jacks inserted in the groove at different positions, and is gradually and stepwise tensioned.
The system is to be finally fixed at the other end of the C tendon material. With such two systems, it is possible to introduce prestress into the entire structure with a minimum of four fixing members. The term “meridian” as used herein refers to a vertical line along the wall surface of the egg-shaped structure, and is orthogonal to the latitude line (a circular line of the wall surface cut horizontally in a circle).

Further, in order to preferably carry out the present invention, it is necessary to use a portable pinch roller for inserting a PC strand disclosed in Japanese Patent Application Laid-Open No. Hei 9-37953, which has been separately proposed by the present applicant. It is easy to insert the tendon into the spiral duct.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 14 is a partial sectional side view of the egg-shaped concrete container structure 1 to which the present invention is applied. An underground pile 5 is driven into the ground 6, an upper standing portion 2 on the ground is erected on a ring base 3 formed thereon, and a hanging bottom portion 4 is formed on the underground side. This egg-shaped concrete structure 1 stores sewage 7 as a digestion tank, and the wall is subjected to hoop tension. The sediment has a shape suitable for collecting and discharging intensively at the center of the lower bottom.

Hereinafter, as an embodiment, an example will be described in which the prestress introduction region is set to be divided into an upper standing portion and a hanging bottom portion. FIG. 1 omits illustration of the meridian-direction PC steel and rebar in this description. FIG. 1 is a wiring diagram of the PC tendon 10 of the egg-shaped concrete container structure 1 (digestion tank). P
The PC strand 10 is used as the C tension member, and has two systems of an upper standing portion and a hanging bottom portion, both of which are shown to be spirally arranged.

FIG. 2 is a sectional view taken along the line AA of FIG.
This shows that the PC strands 10 disposed inside are exposed in the tension slits (concave grooves) 20 which are opened on the outer surface of the wall. In this example, the grooves 20 are shown as four grooves along the meridian from the top end to the lower end of the upper standing portion, but the present invention is not limited to this, and the number, arrangement, length, etc. It can be determined according to the design. In some cases, the concave portions may be dispersed separately.

FIG. 3 is an explanatory view of a step of introducing a prestress into the upper standing wall. One end of the PC strand 10 is fastened by the terminal fixing body 12, and the first jack 31 is mounted on the part of the PC strand 10 exposed in the groove 20, and the first jack 31 is operated to fix the PC strand 10. A tension is applied to the PC strand 10 between the body 12 and the jack 31. Next, the second jack 32 is attached to the PC strand 10 in the groove 20 where the PC strand 10 is exposed next, and the second jack 32 is operated while maintaining the tension of the first jack 31. Tension is introduced into the PC strand 10 between the jacks 31 and 32. afterwards,
While maintaining the tension of the second jack 32, the tension of the first jack 31 is released, and then the third jack 33 is applied to the PC strand 10 in the exposed groove 20.
Is mounted and actuated to introduce tension into the PC strand 10 between the jacks 32,33. Third jack 33
The tension of the second jack 32 is released while the tension of the second jack 32 is maintained. The third jack 33 is preferably used by moving the first jack 31.

Next, in the same manner, the fourth jack 34 is mounted on the PC strand exposed in the groove 20, and the same operation as described above is repeated to sequentially introduce prestress to the other end of the PC strand 10. .

In the description of FIG. 3, the grooves 20 for inserting the tensioning jacks are located at the same position, but are actually shifted by 1/4 turn or 1/2 turn. The position may be determined such that the prestress can be introduced most effectively while taking into consideration the friction between the insertion duct and the PC strand. FIG. 3 is a diagram in which the prestress is introduced from the bottom up, but the same applies when the prestress is introduced from the top down. If the number of laps is large and the length of the PC strand supplied by the manufacturer is insufficient, the other end is fixed at a position in the middle of the spiral and connected to another PC strand, or another position is set at that position. P
It is also possible to fix one end of the C strand and start the same tension as above.

FIG. 4 is a sectional view of the wall showing the tension jack 31 mounted in the concave groove 20 of the wall 11. The tension jack 31 is inserted into the groove 20 from the outside of the groove, and can be mounted so as to cover the PC strand 10 exposed in the groove 20 from the side, so that it can be easily attached and detached and moved. ing.

FIG. 5 is a front view showing the tension slit (concave groove 20) and the tension jack 31 mounted in the concave groove 20 as viewed in the direction of arrows BB in FIG. The PC strand 10 is inserted into a duct formed by the sheath 13 in the wall 11. The PC strand 10 is exposed in the concave groove 20 and is gripped and tensioned by the wedge of the tension jack 31.
After the prestress of the wall body 11 is introduced into the concave groove 20, grout is applied to the inside of the sheath 13 and at the same time, concrete is filled with traces.

FIG. 6 is a detailed view of the drooping bottom portion 4 and shows a state in which a PC strand 10 of a different system from the upper standing portion 2 is provided. FIG. 7 is a view taken in the direction of arrows CC in FIG. 6, and a tension slit formed by a concave groove 20 is formed radially from the vicinity of the center of the lower bottom toward the periphery of the ring base on the inner surface of the wall of the hanging bottom 4. The concave groove 20 serves as an intermediate tension portion that grips and tensions an intermediate portion of the PC strand 10 with a jack. In the example of FIG. 7, four concave grooves 20 are formed. PC strand 10 near center of hanging bottom 4
Is fixed to the fixing body 12, and the PC strand 10 is arranged upwardly from here in a spiral shape in a side view (a spiral shape in a plan view). The other end of the PC strand 10
It is fixed to the fixing section 14 at the upper end of the concave groove 20.

FIG. 8 is an explanatory view of the introduction of prestress in the hanging bottom part 4, and is an enlarged plan view of the central part of FIG. One end of the PC strand 10 is fastened by the terminal fixing body 12, and the first jack 31 is mounted on the PC strand 10 exposed in the recess 20 at a position half a circumstance therefrom, and the first jack 31 is operated. Between the fixing body 12 and the jack 31
The tension is introduced into the C strand 10, and then the second jack 32 is attached to the PC strand 10 that is further exposed from the first jack 31 in the concave groove 20 at a half circumferential position,
The second jack 32 is operated while maintaining the tension of the first jack 31 to introduce a tension between the jacks 31 and 32. Thereafter, the tension of the first jack 31 is released while the tension of the second jack 32 is maintained. Next, the third jack 33 is inserted into the jack mounting position in the front groove 20, and the third jack 33 is mounted on the PC strand 10 exposed in the groove 20,
Activate the third jack 33 to introduce tension between the jacks 32,33. What is necessary is just to transfer the said 1st jack 31 to the 3rd jack 33. Next, while the tension of the third jack 33 is maintained, the fourth jack 34 is maintained.
Is inserted into the groove to tension the PC strand 10 between the jacks 33 and 34, and then the third jack 33 is released. This is alternately repeated to the other end of the PC strand, so that the prestress is reliably introduced into the PC strand 10.

The operating position of the jack in this case may be determined by appropriately changing the frictional coefficient based on the curvature of the PC strand. Also, a PC supplied with a large number of laps
If the length of the strand is insufficient, the other end may be fixed at an intermediate position of the spiral, and the PC strands may be connected to each other or one end of the PC strand may be started from that position.

FIG. 9 is a side view of the tension jack 33 mounted in the concave groove 20 as viewed in the direction of the arrow DD in FIG. FIG. 10 is a front view of the concave groove 20 and the tension jack 33 mounted in the concave groove 20 as viewed in the direction of the arrow E-E in FIG. 8. The PC strand 10 is inserted into a duct formed by the sheath 13 in the wall body 11 of the hanging bottom 4, and is exposed in the concave groove 20.
She is grasped and tensioned by the wedge of a tension jack. After the prestress of the hanging bottom 4 is introduced, grout is applied to the sheath 13 and at the same time, the groove 20 is filled with the concrete.

FIG. 11 shows an example of a tension jack 31 suitable for introducing prestress according to the present invention, and has a machine length as short as possible which can be attached to the intermediate tension portion (the concave groove 20).
Wedge structure 3 so that the middle of PC strand 10 can be grasped
7, the two cylinders 35 and the ram 36 work together to apply tension to the PC strand 10. FIG. 11 is a plan view, FIG.
2 and 13 are views taken along arrows FF and GG in FIG. 11, respectively.

In this embodiment, the egg-shaped concrete container structure has been described. However, the present invention can be applied to a vertical part of an abacus ball-shaped container, which is a similar technique. Also, an example has been described in which the intermediate tension portion is four concave grooves, but the present invention is not limited to this. For example, by considering the friction between the PC strand and the duct, the effectiveness of introducing the prestress, and the like, it is possible to determine the appropriate shape, position, arrangement, and number of the intermediate tension parts by design.

[0028]

According to the method of the present invention, circumferential prestress can be effectively introduced into an egg-shaped concrete container structure with a minimum number of fixing parts. In addition, even if the amount of the PC tendon material and the number of fixing devices, which have been the causes of the soaring construction cost, can be easily given a predetermined tension,
Further, it is not necessary to use a reinforcing steel material at the anchoring portion or fill in the traces, so that the number of construction steps can be reduced and the construction period can be shortened.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional side view of an embodiment.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is an explanatory view of a tensioning step.

FIG. 4 is a sectional view of an intermediate tension portion.

FIG. 5 is a sectional view taken along the line BB of FIG. 4;

FIG. 6 is a partial cross-sectional side view of a hanging bottom portion.

FIG. 7 is a sectional view taken along the line CC of FIG. 6;

FIG. 8 is a partial enlarged view of FIG. 6 and is an explanatory view of tension.

FIG. 9 is a sectional view taken along the line DD in FIG. 8;

FIG. 10 is a sectional view taken along the line EE in FIG. 8;

FIG. 11 is an explanatory view of a jack.

FIG. 12 is an explanatory diagram of a jack.

FIG. 13 is an explanatory diagram of a jack.

FIG. 14 is a partial cross-sectional side view of an egg-shaped concrete container structure to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Egg type concrete container structure 2 Upper standing part 3 Ring base 4 Hanging bottom part 5 Pile 6 Ground 7 Sewage 10 PC tension material (PC strand) 11 Wall 12 Terminal fixing body 13 Sheath 14 Fixing part 20 Groove (for tension) Slits) 31, 32, 33, 34 Jack 35 Cylinder 36 Ram 37 Wedge structure

Claims (3)

[Claims] 1. An egg-shaped concrete container structure,
A spiral PC tendon insertion duct is formed within the shell wall thickness, and a number of intermediate tension portions are formed in the middle of the duct.
The tension member is inserted, one end of the PC tension member is fixed to the fixing portion, the PC tension member is sequentially tensioned at the intermediate tension portion from the fixing portion to the other end, and finally fixed at the other end of the PC tension member. A method for introducing prestress into an egg-shaped concrete container structure, characterized in that: 2. The egg-shaped concrete according to claim 1, wherein the prestress introduction area by the PC tendon is divided into an upper standing portion and a drooping bottom, and tension is introduced by another PC tendon. A method for introducing prestress in a container structure. 3. The method for introducing prestress into an egg-shaped concrete container structure according to claim 1, wherein said intermediate tension portion comprises one or more grooves provided in a meridian direction of an eggshell wall surface. .