JP2006083572A - Prestressed concrete structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prestressed concrete structure capable of easily reducing bending moment acting to deform a sidewall inward near the lower end of the sidewall. <P>SOLUTION: A vertical tendon 4 disposed within the sidewall 1 is disposed to bend at an intermediate part of the sidewall 1 and to incline outward in a wall thickness direction toward the lower end of the sidewall. With this constitution, prestress force is introduced to the tendon 4. Bending moment Mb that is going to deform the sidewall outward, can thereby be generated against bending moment Ma that is going to deform the sidewall inward, generated when prestress force is introduced to a circumferential tendon 5, and the bending moment at the lower end of the sidewall 1 can be relatively reduced. Furthermore, the sidewall 1 may be provided with a portion 1a enlarged in wall thickness, from the intermediate part of the sidewall 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a prestressed concrete structure, and in particular, easily reduces a bending moment that is generated on a side wall by a prestressing force introduced in the circumferential direction of the side wall and is about to deform the side wall near the lower end of the side wall. It is related with the prestressed concrete structure which can be used.

  Conventional container structures such as LNG and LPG storage ground tanks and underground tanks are composed of a bottom plate, a side wall standing on the bottom plate, and a flat or dome-shaped ceiling connected to the upper end of the side wall. Yes. The bottom plate has a larger cross-sectional force (bending moment, shearing force, etc.) compared to other parts at the part where it is joined to the side wall and at the lower end of the side wall. Measures such as over-barreling have been taken. Although the container structure described above has various constituent materials and structural forms depending on its use and scale, reinforced concrete structures such as above-ground tanks and underground tanks that require relatively large-scale durability are required. It is common to be constructed on site.

  By the way, when constructing the bottom plate, side walls, ceiling, etc. constituting the container structure with reinforced concrete, a tension material such as PC steel is used inside or outside the reinforced concrete for the purpose of reducing the amount of reinforcing bars or preventing cracks, The mainstream is to use prestressed concrete structures. That is, a sheath tube is embedded in the bottom plate and the side wall in advance, and after constructing the bottom plate and the side wall, the tension material is inserted into the sheath tube and the end of the tension material is pulled (hereinafter referred to as prestressing force). This is introduced into the sheath tube, and compressive force is applied to the bottom plate and the side wall (post-tension method). In addition, pre-tension that pre-stressed pre-stress force is embedded in the bottom plate and side walls, and the pre-stress force is applied to the side walls by releasing the pre-stress force from the tension material after the bottom plate and side walls are constructed. There are also methods.

  Even in the case of a prestressed concrete structure, as described above, there is no change in that a relatively large cross-sectional force is generated at the lower end of the side wall. The amount of tension material and the amount of reinforcing bars increase. In the side wall of the conventional prestressed concrete structure, a plurality of vertical tension members extending from the lower end of the side wall to the vicinity of the upper end are arranged at predetermined intervals in the circumferential direction of the side wall, and the vertical tension members are surrounded by the vertical direction. In such a manner, a plurality of circumferential tension members are arranged. Note that the vertical tension member is generally disposed at the center of the wall thickness of the side wall when there is no restriction of the reinforcing bar arrangement condition or the circumferential tension member (sheath tube).

  The prestressing force introduced into the circumferential tension material is generally designed assuming that the storage liquid (liquefied natural gas, water, etc.) is full in the tank. Yes, such pre-stress force is introduced at the time of tank construction. That is, the tensile force is offset by generating a compressive force corresponding to the tensile force in the circumferential direction of the side wall caused by the hydraulic pressure when the stock solution is full. Therefore, when the storage liquid is not stored in the tank, such as when the tank is completed, a bending moment that tends to deform the side wall in the vicinity of the lower end of the side wall due to the prestressing force introduced in the circumferential direction. Will occur excessively. This bending moment is borne by the vertical reinforcing bars.

  In the design of tanks (prestressed concrete structures) described above, the prestressing force and the amount of reinforcing bars at the lower end (near the side wall) of the tank are not only during normal operation when the tank is empty or full, but also during earthquakes. Of course, it may be determined by a particularly large level 2 earthquake. However, the plastic deformation performance of structural members can be taken into account during Level 2 earthquakes, but it is necessary to study in the elastic region of structural members (permissible stress design) at all times and during Level 1 earthquakes. The introduction prestress force and the amount of reinforcing bars can be determined at any time.

  Thus, conventionally, the amount of reinforcing bars in the vertical direction of the side wall may be determined with respect to the excessive bending moment at the time of air-liquid caused by the circumferential prestress force designed at the time of full liquid, An uneconomic structure was built. In addition, due to the close-packed reinforcement in the vicinity of the lower end of the side wall, there have been problems such as deterioration in workability, increase in construction cost, and structural failure due to poor wraparound of concrete.

  Then, the method of constructing | assembling the center part of a bottom plate after dividing and constructing the peripheral part and center part of a bottom plate, and integrally constructing the peripheral part and side wall of a bottom plate is performed. According to this construction method, the peripheral edge portion of the bottom plate can be handled as an extended portion of the side wall, and even when a prestressing force is introduced in the circumferential direction of the side wall, the side wall is not restrained by the bottom plate. Therefore, it is possible to prevent an excessive bending moment (a bending moment that tends to deform the side wall inward) from occurring at the lower end of the side wall. After introducing the prestressing force to the side wall, the center portion of the bottom plate can be constructed to integrate the peripheral portion and the center portion of the bottom plate. Patent Document 1 also discloses an invention relating to such a construction method. According to this method, the circumferential prestress force introduced into the lower end portion of the side wall can be effectively introduced in the circumferential direction of the side wall. Such effects can be obtained.

JP 2002-188164 A

  According to the tank construction method disclosed in Patent Document 1, the prestress force introduced in the circumferential direction of the side wall does not enter the bottom plate, and can be effectively introduced in the circumferential direction of the side wall. In addition, according to such a construction method, the problem described above, that is, the problem that an excessive bending moment is generated at the lower end of the side wall when the tank is empty due to the prestressing force in the circumferential direction of the side wall determined when the tank is full. Can be eliminated.

  However, when the peripheral portion and the central portion of the bottom plate are divided and constructed, the problem of deterioration of the structure and the problem of deterioration of workability arise. The deterioration in the quality of the structure is particularly related to liquid-tightness (leakage resistance), and even if it is subjected to external waterproofing or internal waterproofing, the liquid-tightness is reduced compared to the bottom plate that is built integrally. I can't deny that. Moreover, even if liquid-tightness equivalent to that of integral construction can be obtained, it is considered difficult to obtain a sense of security and reliability on the construction order side equivalent to that of integral construction. On the other hand, the deterioration of workability means that when building the center part of the bottom slab, the side walls have already risen, and work efficiency such as material loading, bar arrangement, and concrete placement during the construction of the bottom slab center part is reduced. is there. In addition, the construction period is prolonged by performing the divided construction, resulting in an increase in construction cost.

  The prestressed concrete structure of the present invention has been made in view of the above-mentioned problems, and is a bending that is caused by the prestressing force in the circumferential direction of the structure designed at the time of full liquid to deform the side wall inward. It aims at providing the prestressed concrete structure which can reduce a moment effectively. Moreover, it aims at providing a prestressed concrete structure with good quality by constructing the entire bottom plate integrally. Furthermore, it aims at providing the prestressed concrete structure which can reduce the amount of reinforcement of a side wall rather than the conventional cylindrical or substantially cylindrical prestressed concrete structure.

  In order to achieve the above object, a prestressed concrete structure according to the present invention is a cylindrical or substantially cylindrical prestressed concrete structure composed of at least a bottom plate and a side wall standing on the bottom plate. The vertical and circumferential tension members capable of introducing a pre-stress force are disposed, and the pre-stress force is introduced into the vertical tension material. Means is provided for generating a bending moment to be deformed outward.

  A prestressed concrete structure is a container structure composed of a bottom plate, a side wall standing on the bottom plate, a ceiling connected to the upper end of the side wall, and the bottom plate is a direct foundation supported directly on the ground. Even if it is a form, the pile foundation form supported by a pile etc. may be sufficient. Furthermore, as the shape of the ceiling, an appropriate shape such as a flat plate shape or a dome shape can be selected. Further, PC steel wire or PC steel wire can be used as the tension material in the circumferential direction, and PC steel wire or PC steel wire, PC steel bar, or the like can be used as the tension material in the vertical direction.

  The connecting portion between the bottom plate and the side wall forms a rigid coupling structure by burying vertical tension members and reinforcing bars arranged inside the side wall into the bottom plate for a predetermined length. Therefore, in the side wall, the portion where the cross-sectional force generated by the external force is maximized is generally the lower end of the side wall, which is a connection portion with the bottom plate. In particular, in a cylindrical prestressed concrete structure, when a prestressing force is introduced into the circumferential tension material of the side wall, the side wall is restrained by the bottom plate, so that the side wall is deformed inward at the lower end of the side wall. An excessive bending moment (positive bending moment generated outside the side wall) is generated. That is, as the moment distribution, from the lower end of the side wall toward the upper end, the negative bending moment is shifted from the excessive positive bending moment at the lower end to the negative bending moment, and converges to the moment zero at the upper end of the side wall. Conventionally, since a tension material such as a PC steel bar is disposed in the center of the wall thickness of the side wall, the tension material in the vertical direction has not been a member that bears the bending moment. Therefore, by introducing a pre-stress force after adjusting the arrangement position of the tension members in the vertical direction, at least near the lower end of the side wall, a bending moment (which is generated inside the side wall) tries to deform the side wall outward. Negative bending moment). The bending moment (positive bending moment) that tries to deform the side wall inward when prestressing force is introduced in the circumferential direction of the side wall (positive bending moment) is the bending moment that tries to deform the side wall (negative bending moment). The magnitude of the moment is reduced by this amount. Therefore, the amount of reinforcing bars in the vicinity of the lower end of the side wall can be reduced, and the overcrowded arrangement can be relaxed. Furthermore, since it is possible to effectively reduce the bending moment near the lower end of the side wall, it is not necessary to divide the bottom plate, so that the liquid-tightness of the structure can be secured, and a high-quality prestressed concrete structure can be constructed. Become.

  The vertical tension members are disposed at predetermined intervals in the circumferential direction, and the circumferential tension members are disposed outside the vertical tension members so as to surround the vertical tension members. . This circumferential tension material has its specifications and height direction according to the height level of the side wall so that a compressive force equivalent to the tensile force generated by the hydraulic pressure acting on the side wall when the stock solution is full can be obtained. The arrangement pitch is adjusted. As a construction method, the side wall is raised after the entire bottom plate is built in one piece. Prior to the concrete placement of the bottom plate, one end of a vertical tension member (sheath tube) on the side wall is embedded in the bottom plate by a predetermined length. A predetermined number of tension members in the vertical direction and circumferential direction of the side wall are arranged, and after the predetermined reinforcing bars are assembled, the side wall concrete is placed. In the case of the post-tension method, the prestressing force is introduced after waiting for the development of the predetermined strength of the side wall concrete. In the case of the pretensioning method, the side wall concrete is placed in a state where the prestressing force is introduced in advance. Release the pre-stress power after waiting for strength.

  Further, in another embodiment of the prestressed concrete structure according to the present invention, the means is arranged such that the vertical tension material is inclined outward from the middle of the side wall toward the lower end of the side wall in the wall thickness direction. Is made up of.

  Just by arranging the same vertical tension material as in the past so as to incline outward in the wall thickness direction from the middle of the side wall toward the lower end of the side wall, especially in the vicinity of the lower end of the side wall, the side wall is deformed outward. A bending moment to be generated can be generated. From the upper end of the side wall to the middle of the side wall, the vertical tension material is arranged at the center (near) of the wall thickness as in the conventional case, and is bent so as to incline from the middle of the side wall to the outside of the wall thickness. Thus, it comes closest to the outer peripheral surface of the side wall at the lower end (near) of the side wall. Here, the level in the middle of the side wall where the tension material in the vertical direction bends can be adjusted to an appropriate level according to the design bending moment generated in the vertical surface of the side wall, the concrete specification, or the like. According to the present invention, a bending moment (when a prestressing force is introduced in the circumferential direction of the side wall) that effectively deforms the side wall with only a configuration in which the tension material in the vertical direction is bent halfway is effective. Can be reduced. Therefore, it is possible to reduce the amount of reinforcing bars near the lower end of the side wall, and it is possible to eliminate overcrowding.

  Further, in another embodiment of the prestressed concrete structure according to the present invention, the means has a portion in which the side wall has a wall thickness that increases from the middle toward the lower end of the side wall, and the tension in the vertical direction. It is characterized in that the material is arranged so as to be inclined outward in the wall thickness direction from the middle of the side wall toward the lower end of the portion where the wall thickness is increased.

  Here, as an embodiment of a portion where the side wall becomes thicker from the middle toward the lower end of the side wall, a constant member thickness (hereinafter referred to as a side wall general portion) is provided from the upper end of the side wall to the middle of the side wall. There is a form (a form in which a multi-stage part is added to the outside of the general side wall of the side wall) that is formed in one or two or more stages from the side toward the lower end of the side wall. An appropriate level is selected as the intermediate level of the side wall where the wall thickness is increased depending on the design bending moment generated in the vertical plane of the side wall, the concrete specification, and the like.

  According to the present invention, it is possible to ensure a sufficient cover thickness even when there is no portion where the wall thickness becomes large and a predetermined cover thickness cannot be secured near the lower end of the side wall. . Usually, a circumferential tension member is arranged outside the vertical tension member, and further, vertical and circumferential reinforcing bars are arranged, and at the lower end of the side wall, the outermost reinforcing bar and It is necessary to secure a predetermined cover thickness of about several centimeters to 10 centimeters between the side wall and the outer peripheral surface. When the tension material in the vertical direction is inclined outward in the wall thickness direction toward the lower end of the side wall, it is assumed that it is difficult to ensure a sufficient cover thickness particularly at the lower end of the side wall. Therefore, by providing a portion having a wall thickness of an appropriate shape corresponding to the inclination of the tension material in the vertical direction, it is possible to ensure a sufficient cover thickness in the vicinity of the lower end of the side wall. In addition, by providing a portion where the wall thickness is increased, it becomes possible to dispose the vertical tension material near the lower end of the side wall to the outside of the side wall, and therefore, to deform the larger side wall to the outside. A bending moment can be obtained. The wall thickness of the portion where the wall thickness is increased can be set to an appropriate wall thickness depending on the degree of reduction of the bending moment and the required cover thickness.

  Further, in another embodiment of the prestressed concrete structure according to the present invention, the means has a portion in which the side wall has a wall thickness that increases from the middle toward the lower end of the side wall, and the wall thickness is increased. This is because a vertical tension material is disposed in the portion, and a prestress force is introduced into the tension material.

  A vertical tension member extending from the upper end to the lower end of the side wall is disposed in the side wall general portion, and a separate vertical tension member is disposed in a portion where the wall thickness is increased. By introducing a prestressing force to the tendon disposed in the portion where the wall thickness is increased, it is possible to generate a bending moment that tends to deform the side wall outward. Therefore, it is possible to reduce a bending moment that is generated when the prestressing force is introduced into the circumferential tension material and the side wall is deformed inward.

  As another embodiment of the prestressed concrete structure according to the present invention, the prestressed concrete structure is an above-ground tank or underground tank for storing LNG or LPG.

  A prestressed concrete structure (container structure) having a cylindrical or substantially cylindrical side wall that is relatively large and requires durability is applied to an above-ground tank or an underground tank for storing LNG or LPG. In many cases, the prestressed concrete structure having the joint structure of the bottom plate and the side wall of the present invention is also preferably applied to the tank described above. However, it goes without saying that it does not exclude container structures applied to small-scale tanks and other uses, for example, water storage tanks and farm ponds.

  As can be understood from the above description, according to the prestressed concrete structure of the present invention, the bending moment that is caused by the prestressing force in the circumferential direction of the structure designed at the time of full liquid is caused to deform the side wall inward. Can be effectively reduced. Moreover, according to the prestressed concrete structure of the present invention, the generated bending moment can be kept within a relatively small value while the entire bottom slab is integrally constructed, and the amount of reinforcing bars in the vertical direction can be reduced. Therefore, it is possible to prevent overcrowding in the vicinity of the lower end of the side wall, and to provide a high-quality prestressed concrete structure. Furthermore, according to the prestressed concrete structure of the present invention, it is possible to improve the workability and reduce the construction cost.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are longitudinal sectional views showing an embodiment of the prestressed concrete structure of the present invention. FIG. 4 is a diagram illustrating the bending moment distribution when the liquid is full in the embodiment of FIG. 3, and is a schematic diagram showing a pressure distribution corresponding to the hydraulic pressure distribution generated by the circumferential prestress force, and when the liquid is full It is the schematic diagram which showed the bending moment distribution. FIG. 5 is a schematic diagram showing a bending moment distribution when a prestress force is introduced into a portion where the wall thickness is increased in FIG. 4, and FIG. 6 shows a bending moment distribution of FIG. 4 and a bending moment distribution of FIG. Schematic diagrams showing the bending moment distribution obtained by synthesis are shown. FIG. 7 is a diagram for explaining the bending moment distribution at the time of air-liquid in the embodiment of FIG. 3, and a schematic diagram showing the prestressing force in the circumferential direction, and a schematic diagram showing the bending moment distribution at the time of air-liquid. It is. FIG. 8 is a schematic diagram showing a bending moment distribution obtained by combining the bending moment distribution of FIG. 7 and the bending moment distribution of FIG. Illustration of the sheath tube and the reinforcing bar is omitted.

  FIG. 1 shows a container structure 10 which is a prestressed concrete structure. The container structure 10 includes a bottom slab 2 constructed on the ground, a cylindrical side wall 1 standing on the bottom slab 2, and a dome-shaped ceiling 3 connected to the upper end of the side wall 1. The A ground tank or the like is assumed as the container structure 10 constructed on the ground.

  In the side wall 1, PC steel rods 4 which are vertical tension members are arranged at a predetermined pitch in the circumferential direction, and PC steel wires 5 which are circumferential tension materials are arranged at a predetermined pitch in the vertical direction on the outer periphery thereof. It is arranged by. The PC steel bar 4 is disposed at the center of the wall thickness of the side wall 1 from the upper end of the side wall 1 to a predetermined height (from the lower end of the side wall 1 to the height h1), and is bent at the height h1. From the side wall 1 to the outside of the wall thickness.

  By introducing a prestressing force to the PC steel wire 5 that is a tension material in the circumferential direction, a bending moment Ma is generated on the side wall 1 so as to deform the side wall inward as shown in FIG. On the other hand, since the PC steel bar 4 below the height h1 of the side wall 1 is disposed outside the center of the cross section of the side wall 1, by introducing a prestressing force to the PC steel bar 4 (FIG. In the middle X direction), a bending moment Mb is generated on the side wall 1 so as to deform the side wall outward.

  The bending moment Ma that tries to deform the side wall inward and the bending moment Mb that tries to deform the side wall outwardly reverse the direction of the moment. The bending moment is relatively small.

  In the embodiment shown in FIG. 1, reinforcing bars (not shown) are arranged on the outer periphery of the PC steel wire 5, so that it is necessary to arrange the tension members as shown while securing a predetermined cover thickness. The height h1 can be selected at an appropriate level according to the design bending moment generated in the vertical plane of the side wall 1 or the concrete specifications.

  FIG. 2 shows a container structure 10a according to another embodiment. The container structure 10a is a container structure that includes a portion 1a having a wall thickness that increases from the height h2 of the side wall 1 and has a stepped side wall in the longitudinal section. The PC steel bar 4 disposed inside the side wall 1 is bent in the vicinity of the height h2, and the lower end of the PC steel bar 4 passes through the lower end of the portion 1a where the wall thickness increases and enters the inside of the bottom plate 2. Has become established. A PC steel wire 5 is disposed in the circumferential direction on the outer periphery of the PC steel rod 4.

  In the container structure 10a, the vicinity of the lower end of the PC steel bar 4 can be disposed outside the side wall as much as possible, and a bending moment for deforming the large side wall as necessary can be obtained. It becomes. Moreover, it becomes easy to ensure a sufficient cover thickness between a reinforcing bar (not shown) arranged outside the PC steel wire 5 and the outer periphery of the side wall. Note that the portion 1a where the wall thickness increases may be not only a single stepped shape but also a two or more step shape (not shown).

  FIG. 3 shows a container structure 10b according to another embodiment. The container structure 10b includes a portion 1a where the wall thickness is increased, and a PC steel rod 4a, which is a vertical tension material, is disposed in the container structure 10b. A straight PC steel rod 4 is provided. In this container structure 10b, it is not necessary to bend the PC steel bar 4 in the middle of the container structure 10b, and only a straight PC steel bar is used as in the prior art, and a bending moment to deform the side wall inward is used. It becomes possible to reduce. Hereinafter, based on FIGS. 4-8, reduction of the bending moment in the case of the container structure 10b is demonstrated.

  In FIG. 4, the pressure corresponding to the hydraulic pressure is increased by the side wall 1 due to the hydraulic pressure when the storage liquid 6 such as liquefied natural gas and water is full in the container structure 10b and the prestress force introduced in the circumferential direction. The situation acting on is shown as a schematic diagram. The hydraulic pressure Pa acts in a triangular distribution from the inside of the side wall 1, and at least a circumferential prestressing force that causes a pressure Pp equal to or higher than the hydraulic pressure Pa is applied to the circumferential tension material. Therefore, the prestress force to be introduced is different at the height level of the side wall 1, and the magnitude increases as it goes downward.

  Next to the schematic diagram of the container structure 10b in FIG. 4, an example of the bending moment distribution when the circumferential prestressing force is introduced into the side wall 1 and the storage liquid 6 is accommodated in the container structure 10b is shown. ing. In this state, the pressure pushing the side wall 1 from the left and right is almost balanced, so that an excessive bending moment is not generated at the lower end of the side wall 1. In the figure, + (plus) is a positive bending moment (bending moment that attempts to deform the side wall inward), and − (minus) indicates a negative bending moment (to deform the side wall outward). Bending moment).

  FIG. 5 shows a bending moment distribution when a prestressing force is introduced into the PC steel bar 4a disposed in the portion 1a where the wall thickness of the container structure 10b is increased (in the direction of the arrow X). . By tensioning the PC steel rod 4a, a bending moment (negative bending moment) is generated on the side wall 1 so as to deform the side wall outward.

  4 is introduced into the PC steel rod 4a in the portion 1a where the wall thickness is increased, and the hydraulic pressure when the stock solution 6 is full in FIG. 4, the bending moment caused by the prestressing force introduced in the circumferential direction of the side wall 1. FIG. 6 shows the combined bending moment with the bending moment generated by the applied prestressing force.

  On the other hand, the bending moment distribution during air-liquid is shown in FIG. This bending moment distribution chart is a bending moment distribution chart when no prestressing force is introduced into the PC steel bar 4a. Since the prestressing force introduced into the circumferential tension material is assumed to be full as shown in FIG. 4, when the liquid is empty such as immediately after the container structure 10b is completed, as shown in the figure, the side wall An excessive bending moment (a bending moment that tends to deform the side wall inward) is generated at the lower end of 1.

  Therefore, a prestress force is introduced into the PC steel bar 4a (refer to FIG. 5 for the bending moment distribution at that time), and the bending moment distribution obtained by combining the bending moment distribution of FIG. 7 and the bending moment distribution of FIG. Shown in According to the composite bending moment distribution diagram of FIG. 8, the excessive bending moment (bending moment that tends to deform the side wall inward) generated at the lower end of the side wall is reduced, resulting in a relatively small bending moment. I understand that.

  The composite bending moment distribution diagram of FIG. 8 is schematically shown. In the actual structural design, the positive and negative values (absolute values) of the composite bending moment in the air-liquid state while taking the liquid-full state into consideration. The optimum structural design (tensile material, prestressing force, height of the part where the wall thickness is increased, wall thickness, etc.) is performed so that the value becomes as small as possible.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention. For example, in the case where the container structure is a double-shell type cryogenic tank for storing LNG or LPG, the illustrated side wall may be an outer tank, and an inner tank made of a cold insulating material or the like may be provided on the inner side.

The longitudinal cross-sectional view which showed one Embodiment of the prestressed concrete structure of this invention. The longitudinal cross-sectional view which showed other embodiment of the prestressed concrete structure of this invention. The longitudinal cross-sectional view which showed other embodiment of the prestressed concrete structure of this invention. FIG. 4 is a diagram illustrating a bending moment distribution when the liquid is full in the embodiment of FIG. 3, and is a schematic diagram illustrating a pressure distribution corresponding to a hydraulic pressure distribution caused by a prestressing force in the circumferential direction; The schematic diagram which showed. The schematic diagram which showed the bending moment distribution at the time of introduce | transducing prestress force in the part where the wall thickness in FIG. 4 becomes large. The schematic diagram which showed the bending moment distribution formed by synthesize | combining the bending moment distribution of FIG. 4 and the bending moment distribution of FIG. FIG. 4 is a diagram illustrating a bending moment distribution at the time of air-liquid in the embodiment of FIG. 3, a schematic diagram illustrating a pressure distribution generated by a circumferential prestress force, and a schematic diagram illustrating a bending moment distribution at the time of air-liquid. . The schematic diagram which showed the bending moment distribution formed by synthesize | combining the bending moment distribution of FIG. 7, and the bending moment distribution of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Side wall, 1a ... Wall thickness increase part, 2 ... Bottom plate, 3 ... Ceiling, 4, 4a ... PC steel rod (vertical tension material), 5 ... PC steel wire (circumferential tension material), 10 10a, 10b: Prestressed concrete structure (container structure), 6: Stock solution, Ma: Bending moment for deforming the side wall inward, Mb: Bending moment for deforming the side wall outward

Claims (5)

In a cylindrical or substantially cylindrical prestressed concrete structure composed of at least a bottom plate and a side wall standing on the bottom plate,
A vertical and circumferential tension material capable of introducing a prestressing force is disposed inside the side wall, and a prestressing force is introduced into the vertical tension material. A prestressed concrete structure characterized in that means for generating a bending moment to deform the side wall in the vicinity is taken. The means is
The prestressed concrete structure according to claim 1, wherein the tension material in the vertical direction is arranged so as to be inclined outward in the wall thickness direction from the middle of the side wall toward the lower end of the side wall. The means is
The side wall has a portion in which the wall thickness increases from the middle toward the lower end of the side wall, and the vertical tension material extends from the middle of the side wall toward the lower end of the portion in which the wall thickness increases. The prestressed concrete structure according to claim 1, wherein the prestressed concrete structure is disposed so as to be inclined outward in the thickness direction. The means is
The side wall has a portion in which the wall thickness increases from the middle toward the lower end of the side wall,
The prestressed concrete structure according to claim 1 or 2, wherein a tension member in a vertical direction is disposed in a portion where the wall thickness is increased, and a prestressing force is introduced into the tension material.   The prestressed concrete structure according to any one of claims 1 to 4, wherein the prestressed concrete structure is a ground tank or an underground tank for storing LNG or LPG.

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