JP2011084960A - Storage tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a horizontal tensile force itself caused by flexure near the upper side center of a construction opening of a storage tank formed with the construction opening in a sidewall in construction. <P>SOLUTION: The storage tank having the cylindrical sidewall made of prestressed concrete with prestressed concrete steel members arranged inside, is formed with the construction opening K in the sidewall in construction, wherein the amount of prestress per unit area vertically introduced into an existing region of the construction opening in a plan view is set larger than the other region. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a storage tank in which a construction opening is formed on a side wall during construction.

Conventionally, for example, a large storage tank for storing liquefied natural gas (LNG) fluid is a double shell tank in which a heat insulating material is inserted between a concrete outer tank and a steel inner tank. It is configured.
When manufacturing such a storage tank, a construction opening is provided in a part of the side wall of the outer tub near the ground (see Patent Document 1). And, for example, the equipment for the inner tank is carried in through the construction opening, and the workers are also moved in and out from the construction opening.

  This construction opening is closed with the same material as the outer tub after the inner tub is completed, and the region where the construction opening exists is also part of the outer tub. Although this construction opening depends on the size of the tank, for example, if the storage tank is a large ground tank for LNG and its diameter reaches 100 meters, the equipment to be carried inside will also be enlarged. Therefore, the height is about 4 to 5 meters and the width is about 6 to 8 meters.

In addition, generally the prestressed concrete (Prestressed Concrete) is used for the said outer tank made from concrete.
For this reason, inside the side wall of the outer tub, a PC steel material extending in the circumferential direction with a predetermined interval in the height direction, and a PC steel material extending in the height direction with a predetermined interval in the circumferential direction And are buried.
Such PC steel is inserted into a sheath tube embedded in the outer tub and then tensioned by a jack, thereby compressing concrete and introducing prestress.

Now, the bending strength and watertightness of the outer tub depend on the load caused by the weight of the tank itself and the weight of the roof supported by the sidewall, that is, the axial force due to the so-called dead load, in addition to the pre-stress and the installed reinforcement. is doing.
However, the construction opening and its surroundings are constructed under conditions that do not affect the dead load that should act. For this reason, even after the concrete is placed in the construction opening and closed, the dead load acting on the area where the construction opening exists is smaller than in other areas. That is, the region where the construction opening is present is in a state where the axial force is insufficient with respect to the other regions, and the bending strength and water tightness are insufficient.
For this reason, conventionally, measures have been taken to ensure the bending strength and water tightness of the area where the construction openings existed by arranging the construction openings with reinforcing reinforcing bars or closing them using expanded concrete. .

Japanese Patent Publication No. Sho 63-31634

However, a tensile force is generated in the horizontal direction due to the bending up to the vicinity of the upper portion of the upper side of the opening for construction up to about 3.5 m. Such a tensile force in the horizontal direction remains even when the above-described measures are taken and the construction opening is closed, and acts as harmful stress. For this reason, the probability of occurrence of cracks in the region where the construction opening is present and the peripheral region thereof is increased.
For this reason, it is desired to reduce the horizontal tensile force itself caused by the deflection near the center of the upper side of the opening for construction.

However, if the tank is constructed without providing a construction opening in the outer tub, the above-mentioned concerns are eliminated. However, constructing a double-shell tank constructed by inserting a heat insulating material between the outer tank made of the PC method and the inner tank made of steel, without providing a construction opening in the outer tank, It cannot be employed at all because of a significant decrease in work efficiency.

  The present invention has been made in view of the above-described problems, and in a storage tank in which a construction opening is formed on a side wall during construction, the horizontal direction caused by the deflection near the center of the opening upper side of the construction opening. The purpose is to reduce the tensile force itself.

  The present invention adopts the following configuration as means for solving the above-described problems.

  1st invention is a storage tank which has a cylindrical-shaped side wall which consists of prestressed concrete by which PC steel material is arrange | positioned inside, and the construction opening is formed in the said side wall at the time of construction, Comprising: A configuration is adopted in which the prestress amount per unit area introduced in the vertical direction in the region where the construction opening is present is set larger than that in the other regions. Here, the amount of prestress means the magnitude of the compression pressure acting on the concrete.

  According to a second invention, in the first invention, the amount of prestress is increased by arranging additional vertical PC steel materials between vertical PC steel materials arranged at equal intervals over the entire circumference of the side wall. A configuration that is twice as large as the area is adopted.

  3rd invention employ | adopts the structure that the lower end of the said additional vertical direction PC steel material is located in the upper side of the said construction opening in the said 2nd invention.

  4th invention employ | adopts the structure provided with the outer tank containing the said side wall, and the steel inner tank in any one of said 1st-3rd invention.

  A fifth aspect of the present invention is the storage tank according to any one of the first to fourth aspects, wherein the liquefied natural gas is stored.

According to the present invention, the amount of prestress per unit area introduced in the vertical direction in the region where the construction opening is present in plan view is set larger than that in the other regions.
For this reason, the force (axial force) which supports the area | region where the construction opening existed becomes higher than another area | region, and this suppresses the bending near the center of the opening top of a construction opening, and originates in the said bending. It is possible to reduce the horizontal tensile force itself.

It is a front view of the tank to which the storage tank concerning one embodiment of the present invention is applied. It is an expanded vertical sectional view for the opening for construction of the tank to which the storage tank concerning one embodiment of the present invention is applied. FIG. 3 is a cross-sectional view taken along line X1-X1 of FIG. FIG. 3 is a cross-sectional view taken along line X2-X2 of FIG.

  Hereinafter, an embodiment of a storage tank according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

FIG. 1 is a front view of a tank T to which a storage tank according to this embodiment is applied. Here, the tank T is shown as a large ground tank for storing a liquefied natural gas (LNG) fluid.
This tank T includes an outer tank Ta constructed by a PC method and a steel inner tank (see reference numerals “Tb” in FIGS. 3 and 4 to be described later) similarly to the known liquefied natural gas tank. It consists of a double shell tank. The slab 1 hitting the base of the tank T is joined to the pile heads of a plurality of foundation piles 2, 2... Driven into the ground G.

  A part of the outer tank Ta of the tank T that is slightly higher than the ground is provided with a construction opening K that has a horizontally long rectangle. Since the construction opening K is closed when the tank T is completed and apparently does not appear, the construction opening K is indicated by a two-dot chain line in the drawing.

Note that the size of the construction opening K is formed in accordance with the largest equipment to be carried into the tank T.
As the largest equipment in the tank T of the present embodiment, a plate material forming the inner tank of the tank T can be considered. For this reason, the size of the construction opening K is determined so that the plate material can be easily carried in. For example, when the tank T is a large ground tank for LNG and its diameter reaches as much as 100 meters, the equipment to be carried inside is also enlarged, so the construction opening K has a height of 4-5. Meters and width will be 6-8 meters.

Next, FIG. 2 which is an enlarged longitudinal sectional view of the construction opening K region of the tank T, FIG. 3 which is a sectional view taken along line X1-X1 of FIG. 2 and FIG. 4 which is a sectional view taken along line X2-X2 of FIG. It explains using.
Since these drawings are cross-sectional views, the drawings originally require hatching, but are omitted in order to clarify a sheath tube to be described later. Further, reinforcing bars are arranged in the outer tank Ta and the slab 1, but these reinforcing bars are also omitted except for the upper part of FIG. 3 in order to clarify the sheath tube. Moreover, the inner tank Tb shown in FIGS. 3 and 4 is made of steel, and is provided in the outer tank Ta with a heat insulating material (not shown) interposed therebetween. Moreover, in FIG.3 and FIG.4, in order to improve visibility, PC steel materials are abbreviate | omitted.

As shown in these drawings, a plurality of sheath tubes are embedded in the outer tub Ta. This sheath tube is inserted with a PC steel material, and is composed of vertical sheath tubes VC1, VC2,... Extending in the vertical direction and circumferential sheath tubes HC1, HC2,. Yes.
Each sheath tube is injected with a grout material composed of a cement mill or the like in which aluminum powder is mixed, with the strained PC steel material 10 inserted.

The vertical sheath tubes VC1, VC2,... Are embedded in the vertical direction at a predetermined interval with respect to the circumferential direction of the outer tub Ta.
Among these vertical sheath tubes VC1, VC2,..., Four of the vertical sheath tubes VC2 to VC5 are located in the region where the construction opening K exists, and the vertical sheath tubes VC2 to VC5 are arranged with respect to each other. The interval is determined to be equal to the arrangement interval of the vertical sheath tubes VC1, VC6 to VCn (see FIG. 4 for VCn) provided in the region (other regions) where the construction opening K is not provided. Yes. That is, the arrangement interval of these four vertical sheath tubes VC2 to VC5 located in the region where the construction opening K is provided is maintained at the original arrangement interval of the vertical sheath tubes.

Further, additional vertical sheath tubes AVC1, AVC2, and AVC3 that characterize the present embodiment are provided between the vertical sheath tubes VC2 and VC3, between VC3 and VC4, and between VC4 and VC5. When the outer tub Ta is viewed in plan, the arrangement density of the directional sheath tubes is set to be twice as high as the other regions in the region where the construction opening K exists.
That is, in this embodiment, the PC steel material 10 (inserted through the additional vertical sheath tubes AVC1, AVC2, AVC3) between the PC steel materials 10 (vertical PC steel materials) inserted through the vertical sheath tubes VC1, VC2,. When the additional vertical PC steel material) is arranged, the amount of prestress introduced per unit area is larger than the other regions in the region where the construction opening K exists when the outer tank Ta is viewed in plan. Is set.

The circumferential sheath pipes HC1, HC2,... Are outside the vertical sheath pipes VC1, VC2,... And the additional vertical sheath pipes AVC1, AVC2, AVC3 (on the outer circumferential side of the outer tank Ta) and are related to the height direction of the outer tank Ta. It is provided in the circumferential direction at a predetermined interval.
Among these circumferential sheath tubes HC1, HC2,..., The circumferential sheath tubes HC2 to HC8 are located in the region where the construction opening K was provided.
Note that the dead load of these circumferential sheath tubes HC1, HC2,... Decreases with increasing distance from the slab 1. Therefore, the installation interval is determined to be reduced accordingly (HC6 to HC17 in FIG. 2). reference).

As shown in FIG. 3, the slab sheath tube KC is a sheath tube provided in the slab 1 and is provided in the circumferential direction of the slab 1.
The slab sheath tube KC, the above-described vertical sheath tubes VC1, VC2,..., The additional vertical sheath tubes AVC1, AVC2, AVC3 and the circumferential sheath tubes HC1, HC2,. The PC steel material 10 which consists of high-tensile steel material as a tension material is inserted in this steel pipe.
And each PC steel material 10 is being fixed using the well-known fixing apparatus 3, such as a single strand system, at the both ends of the sheath tube.

  As shown in FIG. 3, the fixing device 3 is attached to a reinforcing bar 5 arranged in the outer tank Ta. Further, the fixing device 3 at the lower end of the other additional vertical sheath tubes AVC1 and AVC3 is also configured similarly to the additional vertical sheath tube AVC2.

In the fixing device 3 used at both ends of the sheath tube, the fixing devices 3 in the vertical sheath tubes VC1, VC2,... And the additional vertical sheath tubes AVC1, AVC2, AVC3 are the vertical sheath tubes VC1, VC2,. The directional sheath tubes AVC1, AVC2, and AVC3 are provided at the upper end and the lower end (the fixing device 3 at the upper end is omitted in FIGS. 2 and 3).
That is, these additional vertical sheath tubes AVC1, AVC2, AVC3 are positioned at the upper side where the lower end portion forms the construction opening K, and the upper end portion (not shown) is the upper end portion of each vertical sheath tube VC1, VC2,. It is located at the same position.
For this reason, in this embodiment, the lower end of the PC steel material 10 (additional vertical PC steel material) inserted into the additional vertical sheath tubes AVC1, AVC2, and AVC3 is positioned on the upper side of the construction opening K.

  Although not shown, the fixing device 3 used in the circumferential sheath tubes HC1, HC2,... And the slab sheath tube KC is provided on both ends obtained by dividing the circumferential direction of the outer tub Ta into a plurality of 180 degrees or the like. It has been.

  It should be noted that the construction of the vertical sheath pipes VC2 to VC5 and the circumferential sheath pipes HC1, HC2,... Positioned in the region where the construction opening K of the vertical sheath pipes VC1, VC2,. The circumferential sheath tubes HC2 to HC8 located in the region where the opening K is provided are used until the construction in the outer tub Ta is completed (that is, the construction of the inner tub Tb and the like is completed, The area exposed to the construction opening K is kept in a cut-out state (until the role is completed). Then, when the role of the construction opening K is finished and the closing timing of the construction opening K has come, the cut-out sheath tube is joined by welding or the like. After joining the sheath tube, the PC steel material is inserted into the sheath tube.

  .., AVC1, AVC2, AVC3 and HC1, HC2,... Provided in the outer tank Ta are arranged according to the construction of the outer tank Ta. That is, the concrete that forms the outer tub Ta is sequentially placed from the slab 1 that hits the base of the tank toward the top, and is disposed accordingly.

  In the tank T of this embodiment, liquefied natural gas (LNG) can be stored in the inner tank Tb after completion, for example.

According to the tank T in the present embodiment as described above, the amount of prestress introduced in the vertical direction per unit area in the region where the work opening K is present in plan view is set larger than in other regions. .
For this reason, the force (axial force) that supports the region where the construction opening K is present is higher than the other regions, thereby suppressing the deflection near the center of the upper side of the opening of the construction opening K. The resulting horizontal tensile force itself can be reduced.
Therefore, it can suppress that the crack which arises in the area | region where the opening for construction existed, and its peripheral region.

Moreover, in the tank T in this embodiment, the structure which the lower end of PC steel material 10 penetrated by additional vertical direction sheath pipe | tube AVC1, AVC2, AVC3 is located in the upper side of the opening K for construction was employ | adopted.
For this reason, the length of the additional vertical sheath tubes AVC1, AVC2, and AVC3 can be shortened, which can be carried out at a low cost, and the fixing device 3 can be arranged without considering the position of the foundation pile 2. It is possible to effectively reduce the tensile force in the horizontal direction due to the bending that occurs in the vicinity of the center of the upper side of the opening K for use.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

For example, in the above-described embodiment, by increasing the arrangement density of the PC steel members 10 extending in the vertical direction, prestress is introduced in the vertical direction per unit area in the region where the construction opening K exists in plan view. A configuration that increases the amount was adopted.
However, the present invention is not limited to this, and for example, adopting a configuration in which the amount of prestress introduced in the vertical direction is increased by increasing the strength of the PC steel material and tensioning the PC steel material more strongly. You can also.

  For example, it is also possible to employ a configuration in which a larger number of vertical PC steel materials 10 are installed.

Moreover, in the said embodiment, the large sized tank T which stores liquefied natural gas (LNG) was mentioned and demonstrated as a storage tank of this invention.
However, the present invention is not limited to this, and can be applied to a tank storing other fluids.

  T ... tank (storage tank), Ta ... outer tank (including side wall), Tb ... inner tank, G ... ground, K ... construction opening, VC1 to VC6, VCn ... vertical sheath tube, AVC1, AVC2, AVC3 ... Additional vertical sheath tube, HC1 to HC17 ... circumferential sheath tube, KC ... sheath tube for slab, 1 ... slab, 2 ... foundation pile, 3 ... fixing device, 4 ... positioning member, 5 ... rebar, 10 ... PC steel (Vertical PC steel, additional vertical PC steel)

Claims (5)

A storage tank having a cylindrical side wall made of prestressed concrete in which PC steel is disposed, and a construction opening is formed in the side wall during construction,
A storage tank, wherein a prestress amount per unit area introduced in a vertical direction in a region where the construction opening is present in a plan view is set larger than that in other regions.   The amount of pre-stress is increased by twice the amount of the other region by arranging additional vertical PC steel between vertical PC steel arranged at equal intervals over the entire circumference of the side wall. The storage tank according to claim 1.   The storage tank according to claim 2, wherein a lower end of the additional vertical direction PC steel material is located on an upper side of the construction opening.   The storage tank according to claim 1, further comprising an outer tank including the side wall and a steel inner tank.   The storage tank according to any one of claims 1 to 4, wherein liquefied natural gas is stored.

Images