JP6428150B2 - Prestressed concrete structure - Google Patents

Description

  The present invention relates to a prestressed concrete structure that is used, for example, in an outer tank of a double-shell cryogenic tank that stores liquefied natural gas.

  A large-sized low temperature tank for storing liquefied natural gas (hereinafter referred to as LNG) is composed of a double shell tank in which a heat insulating material is disposed between an outer tank made of concrete and an inner tank made of steel. The concrete outer tub is generally made of prestressed concrete (hereinafter referred to as PC).

  The outer tank of the LNG low temperature tank serves as a liquid barrier to prevent diffusion when LNG leaks from the inner tank. This outer tub is known as a prestressed concrete structure having at least a disk-shaped bottom plate and a cylindrical side wall, and is manufactured by the following steps.

  First, a plurality of foundation piles are constructed on the ground, and a disk-shaped bottom plate is rigidly connected to the foundation piles. Next, a mold for forming the inner peripheral surface and the outer peripheral surface of the cylindrical side wall is installed over the circumferential direction of the disk-shaped bottom plate. Then, reinforcing bars are assembled in the mold and the sheath tube is arranged in the horizontal direction and the vertical direction, and concrete is placed in the mold by in-situ casting and solidified. Thereby, the annular concrete unit which comprises a part in the height direction of a side wall is shape | molded. Then, the mold is moved upward to form an annular concrete unit in the same manner, and a cylindrical side wall is manufactured by repeating this process.

  Then, a PC steel material is inserted into the sheath tube embedded in the side wall and a tension (hereinafter referred to as prestress) is applied, and in this state, the ground material is filled between the inner wall of the sheath tube and the PC steel material. As a result, the PC steel is integrated with the cylindrical side wall made of concrete and is prevented from being corroded and damaged by the influence of rainwater.

  As prior art document information related to the prestressed concrete structure described above, for example, there is Patent Document 1 below.

Japanese Patent Laid-Open No. 10-238697

  However, the prestressed concrete structure described above has been troublesome because it is necessary to arrange a plurality of sheath tubes in each of the horizontal direction and the vertical direction in the process of manufacturing the cylindrical side wall as described above.

  Then, this invention aims at providing the prestressed concrete structure which reduced the number of sheath pipe | tubes, reduced the effort which arrange | positions a sheath pipe | tube, and suppressed the cost.

The present invention provides a prestressed structure including a concrete structure, a plurality of sheath tubes embedded in the concrete structure, and a tension member that is inserted into the sheath tube and introduces prestress to the concrete structure. In concrete structures,
The concrete structure is manufactured by stacking a plurality of hollow concrete units in the height direction,
Wherein the plurality of sheath tube is Rutotomoni embedded in the concrete structure so as to intersect obliquely with respect to said hollow concrete units, without leading to the upper and lower stages, embedded so as to intersect obliquely to each number And
The tendon is arranged in the sheath tube so as to introduce prestress into the concrete structure in a state of being arranged so as to obliquely intersect the concrete structure.

Before SL plurality of sheath tube is characterized in that the inclination angle for each number of stages for the previous SL hollow concrete unit is changed.

  The concrete structure is characterized by being an outer tank of a cryogenic tank for storing a cryogenic liquid.

  According to the prestressed concrete structure of the present invention, an object of the present invention is to provide a prestressed concrete structure in which the number of sheath tubes is reduced, the labor for arranging the sheath tubes can be reduced, and the cost is suppressed.

It is the perspective view which looked at the low temperature tank which stores LNG from diagonally upward. It is sectional drawing which shows a mode that the low-temperature tank was cut along the perpendicular direction. (A) is a perspective view which shows a mode that the 1st step | paragraph concrete unit was manufactured on the bottom slab. (B) is a perspective view showing a state in which a second-stage concrete unit is overlaid on the first-stage concrete unit. It is the side view which showed a mode that the low temperature tank was seen from the side. It is sectional drawing of the side wall which showed the prestress introduce | transduced by the leak pressure produced in a side wall when LNG leaks from an inner tank, and a tension material.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “this embodiment”) will be described with reference to FIGS. FIG. 1 is a perspective view of a low temperature tank 1 for storing LNG as viewed obliquely from above. FIG. 2 is a cross-sectional view showing a state in which the low-temperature tank 1 is cut along the vertical direction.

  In this embodiment, a prestressed concrete structure will be described with an outer tub 2 of a low-temperature tank 1 for storing LNG. As shown in FIG. 1 and FIG. 2, the low temperature tank 1 includes an inner tank 3 for storing LNG, an outer tank 2 serving as a liquid barrier to prevent diffusion when LNG leaks from the inner tank 3, and an inner tank 3 and a heat insulating material 12 disposed between the outer tub 2.

  The outer tub 2 of the low-temperature tank 1 is a concrete structure including a bottom slab 5, side walls 6, and a roof 7. This outer tub is a prestressed concrete structure in which a sheath tube 4 is embedded in a side wall 6 and prestress is introduced by a tension member 8 inserted into the sheath tube 4.

  The bottom plate 5 is a disk-shaped member made of concrete. The bottom plate 5 is supported at a predetermined height position from the ground by a plurality of foundation piles 10 embedded in the ground.

  The side wall 6 is made of concrete on the bottom plate 5. The side wall 6 has a substantially cylindrical shape having an outer peripheral surface and an inner peripheral surface. And the buttress 6a which is a retaining wall which plays the role which receives and reinforces a lateral load is formed in the outer peripheral surface so that four (plural) may be protruded in radial direction at equal intervals with respect to the circumferential direction.

  The side wall 6 is formed by stacking three short cylindrical concrete units 11a, 11b, and 11c in the height direction. And inside this concrete unit 11a, 11b, 11c, the sheath pipe | tube 4 is arrange | positioned so that it may cross | intersect diagonally.

  Hereinafter, a method for manufacturing the concrete units 11a, 11b, and 11c will be described with reference to FIG. FIG. 3A is a perspective view showing a state in which the first-stage concrete unit 11 a is manufactured on the bottom plate 5. (B) is a perspective view showing a state in which the second-stage concrete unit 11b is overlaid on the first-stage concrete unit 11a.

  In the concrete unit 11 a, first, a process of assembling a reinforcing bar that is a framework over the circumferential direction of the bottom plate 5 and arranging the sheath tube 4 is performed. Here, the sheath tube 4 includes one arranged along the vertical direction and one arranged obliquely along the circumferential direction of the concrete unit 11a.

  A large number of sheath tubes 4 arranged along the vertical direction of the concrete unit 11a are arranged at equal intervals along the circumferential direction so as to penetrate the concrete unit 11a in the vertical direction.

  The sheath tube 4 disposed obliquely along the circumferential direction of the concrete unit 11a is disposed radially outward of the concrete unit 11a than the sheath tube 4 disposed along the vertical direction. And this sheath pipe | tube 4 is diagonally arrange | positioned with respect to the half circumference among the circumferential directions of the side wall 6. FIG. The end portion of the sheath tube 4 extends from one of the four buttresses 6a formed in the circumferential direction to the buttress 6a at a position half a circumference away from the circumferential direction. From the one buttress 6a to the buttress 6a located at a half circumference, the two sheath tubes 4 and 4 are arranged so as to cross each other. That is, two sheath tubes 4 are arranged so as to cross each other obliquely every half circumference, and a total of four sheath pipes 4 are arranged on the entire circumference in the circumferential direction of the concrete unit 11a. Here, the sheath tube 4 being disposed obliquely means that the sheath tube 4 is disposed obliquely so as to intersect the horizontal direction and is also oblique to the concrete bottom.

  Next, a process of assembling a mold for forming the outer peripheral surface and the inner peripheral surface of the concrete unit 11a over the circumferential direction of the bottom plate 5 is performed. Then, a molding process is performed in which concrete is cast into the mold to form a shape.

  And the reinforced concrete shape | molded by the short cylindrical shape is solidified through a curing process, and the demolding process which removes a formwork is performed. Through this series of steps, the first-stage concrete unit 11a is manufactured as shown in FIG. In FIG. 3A, the four sheath tubes 4 disposed so as to intersect the inside of the concrete unit 11a and the plurality of sheath tubes 4 disposed in the vertical direction are indicated by dotted lines.

  The side wall 6 is manufactured by repeating this series of steps three times. Here, as shown in FIG. 3B, when the second-stage concrete unit 11b is manufactured, the sheath pipe 4 in which the inclination angle of the second-stage sheath pipe 4 with respect to the horizontal direction is arranged in the first stage. And the end of the second-stage sheath tube 4 is arranged so as to be shifted by a quarter of the circumference in the circumferential direction with respect to the end of the sheath tube 4 arranged at the first stage. .

  Similarly, when the third-stage concrete unit 11c is manufactured, the inclination angle of the third-stage sheath tube 4 with respect to the horizontal direction is larger than the inclination angle of the sheath pipe 4 arranged in the second-stage, and three It arrange | positions so that the edge part of the sheath pipe | tube 4 of a step | paragraph may shift | deviate by 1/4 turn in the circumferential direction with respect to the edge part of the sheath pipe | tube 4 arrange | positioned in the 2nd step | paragraph. That is, in this embodiment, the sheath tubes 4 arranged in the concrete units 11a, 11b, and 11c are arranged so that the inclination angle increases from the first stage to the third stage.

  The side walls 6 are manufactured by making the concrete units 11a, 11b, and 11c described above in three stages. Moreover, when the side wall 6 is manufactured, a dome-shaped roof 7 is manufactured on the concrete.

  With reference to FIG. 4, a state in which prestress is introduced into the side wall 6 by, for example, PC steel as the tension member 8 will be described. FIG. 4 is a side view showing the low temperature tank 1 as viewed from the side. In FIG. 4, the tendon material 8 disposed so as to obliquely intersect the inside of the side wall 6 is indicated by a dotted line.

  In the side wall 6 shown in FIG. 4, the tendon 8 is inserted into the sheath tube 4 and prestress is introduced. This tendon 8 introduces prestress in a state where it is arranged so as to cross obliquely with respect to the horizontal direction. The tendon 8 introduces prestress in the circumferential direction and the vertical direction of the side wall 6 by being arranged obliquely with respect to the horizontal direction.

  Moreover, the sheath pipe | tube 4 arrange | positioned at concrete unit 11a, 11b, 11c is arrange | positioned so that an inclination angle may become large as it goes to the 3rd step from the 1st step. That is, the tendon material 8 arranged in the sheath tube 4 is also arranged so that the inclination angle with respect to the horizontal direction increases as it goes from the first stage to the third stage. Accordingly, the tension material 8 has a larger prestress CS in the circumferential direction and a smaller prestress VS in the vertical direction from the third stage to the first stage.

  Here, with reference to FIG. 5, the relationship between the leak pressure S1 generated in the side wall 6 when LNG leaks from the inner tank 3 and the prestress introduced by the tendon 8 will be described. FIG. 5 is a cross-sectional view of the side wall 6 showing the leakage pressure S1 generated in the side wall 6 when LNG leaks from the inner tank 3 and the prestress introduced by the tendon 8.

  As shown in FIG. 5, when LNG leaks from the inner tank 3, a high leak pressure S <b> 1 is generated as stress on the side wall 6 toward the bottom, and the stress due to the leak pressure S <b> 1 decreases toward the top. . As described above, the tendon 8 is arranged so that the inclination angle with respect to the horizontal direction increases as it goes upward, and the circumferential prestress CS increases as it goes downward. As a result, it is possible to introduce a prestress S2 that is stronger toward the bottom from the top of the side wall 6 so as to oppose the leakage pressure S1 generated at the side wall 6.

  According to the prestressed concrete structure of the present invention, the plurality of sheath tubes 4 are embedded in the concrete structure so as to cross each other diagonally, and the tension members 8 are arranged in the sheath tube 4 so as to be concrete structures. Prestress is introduced into the side wall 6 which is a concrete structure in a state where the side wall 6 is arranged so as to cross obliquely. That is, the tension material 8 introduces prestress not only in the horizontal direction but also in the vertical direction by being disposed obliquely. As a result, the sheath tube 4 arranged in the vertical direction can reduce the number of the sheath tubes 4 arranged in the vertical direction and can reduce the cost as compared with the conventional arrangement in the vertical direction and the circumferential direction. Further, the tension members 8 are arranged so as to cross each other, so that prestress can be introduced evenly to the side walls 6.

  Moreover, according to the prestressed concrete structure of the present invention, the side wall 6 that is a concrete structure is manufactured by stacking hollow concrete units 11a, 11b, and 11c in the height direction. The plurality of sheath tubes 4 are embedded so as to obliquely intersect each hollow concrete unit 11a, 11b, 11c, and the inclination angle is changed for each hollow concrete unit 11a, 11b, 11c. Thereby, a prestress can be changed according to the height position in the side wall 6, and a prestress can be changed according to the stress which generate | occur | produces in a concrete structure.

  Moreover, according to the prestressed concrete structure of this invention, a concrete structure is the outer tank 2 of the low temperature tank 1 which stores a low temperature liquid (low temperature fluid). The outer tub 2 which is a prestressed concrete structure can counteract the liquid pressure (fluid pressure) generated in the side wall 6 even if the low temperature liquid leaks from the inner tub 3, and can prevent the low temperature liquid from diffusing.

  In addition, the prestressed concrete structure of this invention is not limited to the above-mentioned Example. For example, the side wall 6 has been described with a structure in which three concrete units are stacked, but the present invention is not limited to this. The side wall 6 may have a single-stage structure with a single concrete unit, or may have a plurality of stages such as a two-stage, a four-stage, and a five-stage.

  In addition to the heat insulating material 12 on the bottom side between the outer tub 2 and the inner tub 3, a TCP plate (thermal corner protection) is arranged, and when the low temperature liquid leaks from the inner tub 3, the thermal stress is small. If it is, the inclination angle of the tendon 8 may be increased accordingly.

  Moreover, the upper part of the side wall 6 generates a greater stress than other parts for the purpose of supporting the roof 7. Therefore, in order to cope with this stress, the inclination angle of the tendon member 8 may be reduced at the upper position on the outer peripheral surface of the side wall 6.

  The prestressed concrete structure of the present invention can be changed without departing from the gist of the present invention.

1 Low temperature tank 2 Outer tank (Prestressed concrete structure)
4 Sheath tube 6 Side wall 6a Buttress 8 Tension material

Claims (3)

In a prestressed concrete structure comprising: a concrete structure; a plurality of sheath pipes embedded in the concrete structure; and a tension member that is inserted into the sheath pipe and introduces prestress to the concrete structure. ,
The concrete structure is manufactured by stacking a plurality of hollow concrete units in the height direction,
Wherein the plurality of sheath tube is Rutotomoni embedded in the concrete structure so as to intersect obliquely with respect to said hollow concrete units, without leading to the upper and lower stages, embedded so as to intersect obliquely to each number And
Prestressed concrete characterized in that the stress material introduces prestress to the concrete structure in a state of being arranged so as to obliquely intersect the concrete structure by being arranged in the sheath tube. Structure. Wherein the plurality of sheath tube is prestressed concrete structure according to claim 1, the inclination angle for each number of stages for the previous SL hollow concrete unit, characterized in that it is changed.   The prestressed concrete structure according to claim 1 or 2, wherein the concrete structure is an outer tank of a low-temperature tank that stores a low-temperature liquid.

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