JP2017036553A - Wall body and wall body construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prestressed wall body which can be rapidly constructed, with less problems in design or construction.SOLUTION: A dike 2a is a concrete cylindrical wall body and vertically prestressed with a tendon 13a in a lower part 21. An upper end of the tendon 13a is fastened at a cutout part 20 on an inner side face of the dike 2a. The concrete of the dike 2a is continuously casted upward regardless of tensing operation of the tendon 13a. The tendon 13a can be tensed when the strength of the concrete in a range up to a height of the cutout part 20 appears.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cylindrical wall body and a construction method thereof.

  A PC (prestressed concrete) tank is a facility for storing liquids such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas). FIG. 8 shows an example of an LNG tank 100 that stores LNG as a PC tank. The LNG tank 100 of FIG. 8 is provided with a liquid breakwater 2 on a bottom slab 5 supported by a pile 4 in the ground 7 and an inner tank 3a and an outer tank 3b made of a steel plate or the like inside. The roof portion of the outer tub 3b is made of steel or a composite structure of steel plate and reinforced concrete, and the side portion of the outer tub 3b is formed by attaching a steel liner plate to the liquid barrier 2. The bottom of the outer tub 3b has a shape in which a liner plate is pasted on the bottom plate. LNG is stored in the inner tank 3a, and a heat insulating material is disposed between the inner tank 3a and the outer tank 3b to perform cold insulation.

  The breakwater 2 is a concrete cylindrical wall provided to prevent leakage of LNG to the outside when the inner tank 3a is damaged, and is usually cylindrical. The breakwater 2 needs to have a structure capable of withstanding the hydraulic pressure of LNG, so that prestress is introduced by the tension of the circumferential and longitudinal tension members.

  FIG. 9 is a diagram illustrating an example of a cross section of the liquid breakwater 2. Although the hydraulic pressure can be resisted by introducing a prestress by the circumferential tension material 11 to the liquid breakwater 2, the liquid breakwater 2 is always in a state where no liquid pressure is applied from the inside of the tank. For this reason, a bending moment in the vertical plane due to circumferential prestress is applied to the breakwater 2. A longitudinal tension member is provided mainly to resist this bending moment, and a long tension member (not shown) extending from the lower portion 21 of the breakwater 2 to the top through the upper portion 22 and below the breakwater 2. In many cases, a short tension member 13 provided in the portion 21 is used in combination. By introducing eccentric prestress in the breakwater 2 with these tendons, the bending moment in the opposite direction to the bending moment in the vertical plane is generated, and the bending moment in the vertical plane is canceled out. be able to.

  Since the hydraulic pressure applied to the breakwater 2 generally increases at the lower portion 21, the circumferential tension material 11 is more disposed at the lower portion 21 and less disposed at the upper portion 22. As a result, the bending moment in the vertical plane is large in the lower part 21 of the liquid barrier 2 and is small in the upper part 22 thereof. Therefore, in the lower portion 21 of the breakwater 2, the short tension members 13 are added and the longitudinal tension members are densely arranged. In the upper portion 22 of the breakwater 2, the above-described long tendon exists, but the arrangement of the tendon is relatively rough due to the absence of the short tendon 13. In some cases, the above-described long tendon may not be arranged. is there.

  In order to effectively cancel the bending moment in the vertical plane described above, it is desirable that the longitudinal tension member 13 of the lower portion 21 of the breakwater 2 be arranged as eccentric as possible. Therefore, in the example of FIG. 9, the lower portion 21 of the breakwater 2 is widened outwardly in a taper shape, and the tension material 13 is inclined and disposed along this taper.

  The lower end portion of the tension material 13 is fixed by the fixing portion 131 embedded in the bottom plate 5. The upper end portion of the tension member 13 is fixed by the fixing portion 131 in the middle of the liquid breakwater 2, and this fixing portion 131 is often provided in a range of 3 to 10 m from the bottom end of the liquid breakwater 2. Conventionally, after the concrete in this range is placed and the strength is developed, the tension member 13 is tensioned and the upper end portion is fixed by the fixing portion 131, and then the liquid breakwater 2 above the fixing portion 131 is fixed. Concrete was cast.

  As another method, Patent Document 1 discloses that the upper end portion of the longitudinal tension material in the lower part of the breakwater is obliquely drawn out to the cutout portion on the outer side surface of the breakwater, and the tension material is removed at the cutout portion. After tension and fixing of the upper end, the notch is filled with concrete.

JP 2007-303101 A

  In the conventional method, since the concrete of the liquid bank cannot be placed only after the tension work of the longitudinal tension material is performed in the lower part of the liquid bank, the entire construction period is extended by the tension work, The period is 1.5 to 2.0 months for a 200,000 KL class tank.

  If it is the method of patent document 1, it is not necessary to interrupt construction of a breakwater by tension work, and the whole construction period can be shortened. However, in the method of Patent Document 1, it is necessary to bend the upper end portion of the tendon material outward in order to pull out the upper end portion of the tendon material obliquely to the notch portion on the outer side surface of the breakwater.

  PC steel used for the tension material can be bent and arranged only with a minimum curvature of about R = 3 m, and the PC steel material is arranged in a straight line near the anchoring part. It is necessary to avoid interference with other reinforcing bars and the design becomes difficult. In addition, in order to avoid such interference, the reinforcing reinforcing bars in the circumferential direction of the interference range may be cut once, and reinforcement of the range may be performed afterwards, but the range becomes large and construction is troublesome. In addition, if the tendon is bent and disposed, the frictional resistance force during tension is large and the introduction force is small, and as a result, an additional tendon must be disposed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a wall body or the like that can quickly build a wall body into which prestress has been introduced and has few problems in design and construction.

  A first invention for solving the above-described problem is a concrete cylindrical wall body in which prestress due to a longitudinal tension member is introduced into a lower portion, and at least one end portion of the tension member The wall body is fixed at a fixing position on the inner side surface of the wall body.

  The tendon is preferably inclined in a substantially straight line so as to go outward as it goes downward. The fixing position is, for example, a notch provided on the inner side surface of the wall body. Or the protrusion part provided in the inner side surface of the said wall body may be sufficient.

  The outer side surface of the lower part of the wall body is preferably widened outward with respect to the upper part. For example, the outer side surface of the lower portion of the wall body is inclined in a substantially straight line so as to go outward as it goes downward, and the tension material is centered in the thickness direction at the lower portion of the wall body. It is eccentric to the outside.

  A second invention is a wall construction method for constructing a concrete cylindrical wall body in which prestress due to a longitudinal tension material is introduced into a lower portion, and at least one end of the tension material is attached to the wall construction method. The wall construction method is characterized in that fixing is performed at a fixing position on the inner side surface of the wall body.

  In the second invention, after the placement of the concrete above the fixing position in the wall body is started, the tension material is tensioned.

  It is desirable that the tendon be inclined substantially linearly so as to go outward as it goes downward. The fixing position is, for example, a notch provided on the inner side surface of the wall body. Or the protrusion part provided in the inner side surface of the said wall body may be sufficient.

  The outer side surface of the lower part of the wall body is preferably widened outward with respect to the upper part. For example, the outer side surface of the lower portion of the wall body is inclined in a substantially straight line so as to go outward as it goes downward, and the tension material is lower than the center in the thickness direction at the lower portion of the wall body. It is arranged eccentrically on the outside.

  The tension material is arranged in a substantially U shape, for example, and the other end portion is tensioned in a state where one end portion is fixed to the fixing position on the inner side surface of the wall body, so that the fixing position on the inner side surface of the wall body is determined. To settle.

  In the present invention, since the end portion of the tension member is pulled out to the fixing position on the inner side surface of the wall body, the tension work can be performed after the placement of the concrete above the fixing position is started. Therefore, it is possible to shorten the overall construction period. In addition, it is possible to draw out the tension material linearly in an oblique direction while arranging the tension material as far as possible in the lower part of the wall body, so it is effective for the bending moment in the vertical plane described above by the tension material. While being resisted, it can be arranged so that it does not easily interfere with the circumferential tension material inside the wall, reinforcing reinforcing bars, etc., and the design is easy. Further, when the reinforcing reinforcing bars in the circumferential direction of the interference range are once cut, the range can be reduced. In addition, since the tendon is arranged in a substantially straight line, a decrease in tension due to friction is less than that in the curved arrangement, and the amount of the tendon can be reduced.

  The shape of the fixing position may be a notch or a protrusion. In the former case, the inner side surface of the wall can be smoothed by filling the notch with a filler, and in the latter case, no filling work is required.

  Furthermore, in the present invention, the outer side surface of the lower portion of the wall body is widened outward with respect to the upper portion, so that the tendon can be arranged on the outer side. For example, when the outer side surface is inclined in a substantially straight line so as to go outward as it goes downward, and the tension material is decentered outward from the center in the thickness direction at the lower part of the wall, the tension material as described above. It is effective as an arrangement.

  In addition, the vertical tension material in the lower part of the wall body can be arranged in a substantially U shape. In this case, if one end is fixed and only the other end is tensioned and prestress is introduced, the tension work is performed. Can be made more efficient.

  According to the present invention, a wall body in which prestress is introduced can be quickly constructed, and a wall body or the like with few problems in design and construction can be provided.

Diagram showing breakwater 2a The figure shown about the notch part 20 The figure which shows the construction method of the breakwater 2a The figure which shows the construction method of the breakwater 2a Diagram showing breakwater 2b The figure which shows the breakwater 2c The figure which shows another example of a notch Diagram showing LNG tank 100 Diagram showing breakwater 2

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

(1. Breakwater 2a)
FIG. 1 is a view showing a breakwater 2a according to the first embodiment of the present invention. The breakwater 2a is a breakwater for the LNG tank described with reference to FIG. 8 and is a concrete cylindrical wall body fixedly provided on the bottom plate 5. The breakwater 2a has a substantially cylindrical shape, for example. The configuration of the LNG tank other than the breakwater 2a is the same as that described with reference to FIG.

  In addition to the circumferential tension member 11 and the reinforcing steel bars (not shown), the breakwater 2a resists bending moment in the vertical plane caused by the prestress by the circumferential tension member 11, so As the tension material, a long tension material (not shown) reaching the top from the lower portion 21 of the breakwater 2a through the upper portion 22 and a short tension material 13a provided on the lower portion 21 of the breakwater 2a are arranged. The tendon members 11, 13a are disposed through the corresponding sheath tube 30. A gap between the tendon members 11 and 13a and the sheath tube 30 is filled with a filler such as cement milk.

  The lower part (bottom part) 21 of the breakwater 2a is widened outward with respect to the upper part 22, and in this embodiment, the outer side surface of the lower part 21 is substantially linear so that it goes outward as it goes downward. It has an inclined tapered shape. The outside means the outside of the tank, and the center side of the tank is the inside.

  A vertical tension member 13a is disposed in the lower portion 21 of the breakwater 2a. The upper end of the tension member 13a is formed in a notch 20 (fixing position) provided on the inner side surface of the breakwater 2a. The fixing unit 131 fixes the image. The tension member 13a is arranged in a substantially linear shape so as to go outward as it goes downward along the inclination of the outer side surface of the lower portion 21 of the liquid barrier 2a.

  In the lower part 21 of the breakwater 2a, the tendon 13a is arranged eccentrically outside the center line (see the dotted line in the figure) in the thickness direction of the lower part 21, and the cover on the outer side surface is about 20 to 25 cm. ing. The lower end portion of the tension material 13 a is fixed by the fixing portion 131 in the bottom plate 5.

  PC steel materials such as PC steel rod, PC steel wire (single strand), PC steel stranded wire, unbonded PC steel stranded wire can be applied as the tension material 13a. Easy to place steel bars. When an unbonded PC steel stranded wire is used, the sheath tube 30 can be omitted.

  As shown in FIG. 2A, the notch 20 has a shape in which the inner side surface of the breakwater 2a is notched in a substantially L shape, and the lower surface 200 is in the longitudinal direction (inclination direction) of the tension member 13a. It is almost orthogonal. Note that reference numeral 301 in FIG. 2A denotes a filler in the sheath tube 30.

  FIG. 2B is a view of the vicinity of the lower portion of the breakwater 2 as viewed from the inside. In this embodiment, a notch 20 is formed for each tension member 13a. Each notch 20 is filled with a filler 201 such as concrete or mortar, and smoothed so as to be flush with the inner side surface of the liquid barrier 2a.

(2. Construction method of the breakwater 2a)
When constructing the breakwater 2a, for example, as shown in FIG. 3A, after the bottom plate 5 is constructed, the concrete of the breakwater 2a is placed in order from the bottom to the top.

  A fixing portion 131 for fixing the lower end portion of the tension member 13a is embedded in the bottom plate 5, and a sheath tube 30 for passing the tension members 11, 13a is embedded in the concrete of the bottom plate 5 and the liquid breakwater 2a. The sheath tube 30 is provided with a filler inlet and a hose (not shown) for air removal and filling confirmation as required. In the present embodiment, the tension member 13a is disposed in advance in the corresponding sheath tube 30 and the lower end portion is attached to the fixing portion 131 in the bottom plate 5 before placing the concrete on the breakwater 2a.

  A notch 20 for fixing the upper end of the tension member 13a is formed at a predetermined location on the inner side surface of the liquid barrier 2a by boxing or the like so that the upper end of the tension member 13a protrudes into the notch 20. Keep it.

  The concrete of the breakwater 2a is placed in several lots, but it is continuously launched up to the top without interruption. About the tension material 13a, after starting the placement of the concrete above the notch 20 in the breakwater 2a, the strength of the concrete up to the height of the notch 20 is expressed and reaches a predetermined value Tension work is now possible, and there is a high degree of freedom when you are nervous. In the present embodiment, it is assumed that the tension work is performed at a relatively early stage during construction of the breakwater 2a. In this case, the internal facilities of the breakwater 2a are not so advanced, and there is no problem even if the tension work is performed from the inside.

  At the time of the tension work, as shown in FIG. 3B, the upper end portion of the tension member 13a is tensioned as shown by an arrow A at the notch portion 20 and fixed at the fixing portion 131, and the tension member 13a and the sheath tube 30 are Fill the gap between them. The notch 20 is filled with a filler 201 as shown in FIG. In this embodiment, the tension work of the circumferential tension material 11 in the range up to the height of the notch 20 is also performed at this stage.

  During tension work, the concrete of the breakwater 2a can be continuously cast without any breaks. If the concrete is cast to the top and strength is developed, as shown in FIG. 4 (b), the remaining circumferential direction Arrangement and tension of the tension members 11 are performed in the same manner as before, and the construction of the breakwater 2a is completed. In addition, about the above-mentioned long longitudinal tension material (not shown), since arrangement | positioning and tension | tensile_strength in a sheath pipe | tube (not shown) can be performed during construction of the breakwater 2a as usual, description is abbreviate | omitted here. did.

  As described above, in the present embodiment, the upper end portion of the tension member 13a is pulled out to the cutout portion 20 on the inner side surface of the liquid barrier 2a, so that even after the placement of concrete above the cutout portion 20 is started. Tension work can be performed, and it is not necessary to interrupt the construction of the breakwater 2a by the tension work, and the entire construction period can be shortened. For example, in the case of a breakwater for a 200,000 KL class LNG tank, the construction of the breakwater is interrupted by tension work as in the conventional case, but it takes about 10.5 to 11 months to build the breakwater. Then, this can be shortened to about 1.5 to 2.0 months and to about 9 months.

  Further, the tension member 13a can be pulled out linearly in an oblique direction while arranging the tension member 13a as far as possible in the lower portion 21 of the liquid barrier 2a. While effectively resisting the bending moment, it can be arranged so that it does not easily interfere with the circumferential tension members 11 and reinforcing reinforcing bars in the breakwater 2a, and the design is easy. Further, when the reinforcing reinforcing bars in the circumferential direction of the interference range are once cut, the range can be reduced. Moreover, since the tension material 13a can be arrange | positioned substantially linearly, compared with curve arrangement | positioning, there is little fall of the tension force by friction and the quantity of the tension material 13a can be decreased.

  Moreover, in this embodiment, the fixing position of the upper end part of the tension member 13a is the notch part 20, and the inner side surface of the liquid barrier 2a can be smoothed by filling the notch part 20 with the filler 201 after the tension work. It is suitable in terms of workability when installing the liner plate and prevention of stress concentration.

  However, the fixing position is not limited to this, and the inner side surface of the breakwater 2b may be formed in a protruding shape as shown in the breakwater 2b in FIG. In this case, the above filling operation is not necessary. In any case, when the tendon 13a is pulled out obliquely in a substantially straight line, it is possible to increase the inclination (close to the horizontal) as compared with the case where the tendon is bent. It becomes possible to do.

  Further, since the outer side surface of the lower portion 21 of the liquid breakwater 2a is widened outward with respect to the upper portion 22, the tension member 13a can be disposed on the outer side. In the present embodiment, the outer side surface of the lower portion 21 is inclined substantially linearly so as to go outward as it goes downward, and the tension members 13a are inclined substantially linearly along the inclination. By decentering outward from the center in the thickness direction, it is effective as an arrangement of the tendon material 13a as described above.

  However, the shape of the lower part 21 and the arrangement of the tendon are not limited to this. For example, the lower part 21 may be widened stepwise outward with respect to the upper part 22, or the lower part 21 may not be widened with respect to the upper part 22. It is also possible to arrange the tension material 13a by bending it inward as required, and it is also possible to omit the long tension material in the longitudinal direction described above.

  In addition, in the present embodiment, the lower end portion of the tension member 13a is fixed in the bottom plate 5, but the tension member 13a ′ is arranged in a substantially U shape, for example, as shown in the liquid barrier 2c of FIG. An example in which fixing in the bottom plate 5 is not performed is also conceivable. FIG. 6B is a view of the breakwater 2c from the inside, and the tension members 13a 'and the like are illustrated by dotted lines.

  In this case, both ends of the tension material 13 a ′ are fixed by the fixing part 131 at the notch part 20, and the U-shaped folded part 132 is embedded in the bottom plate 5. The tension material 13a ′ may be simultaneously tensioned from both ends, but one end may be fixed to the fixing portion 131 of the notch 20 and only the other end may be tensioned to introduce prestress. . Thereby, the tension work can be made efficient.

  In the present embodiment, as shown in FIG. 2B, the notches 20 are provided for the tension members 13a, and the notches 20 are arranged in a line in the circumferential direction of the liquid barrier 2a. This is not a limitation. For example, when the tension members 13a are densely arranged and adjacent tension members 13a are close to each other, as shown in FIG. 7A, slits that are continuous in the circumferential direction of the breakwater (corresponding to the horizontal direction in the figure). A notch 20b may be provided. Furthermore, when the fixing position of the upper end portion of the tension member 13a is a plurality of upper and lower steps, fixing notches 20 may be provided on the upper and lower steps as shown in FIG.

  In the present embodiment, an example of constructing the LNG tank breakwater 2a has been described. However, the present invention is not limited to this, and can be applied to a liquid breakwater of other tanks such as an LPG tank, In addition, a cylindrical wall body can be used other than the tank. Further, in this embodiment, the breakwater 2a is constructed by placing concrete on site, but the present invention can also be applied to the construction of a breakwater using precast blocks. In this case, a through-hole for passing the tension material 13a and the like, the notch 20 and other necessary things are formed in the precast block in advance.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

2, 2a, 2b, 2c; Breakwater 3a; Inner tank 3b; Outer tank 4; Pile 5; Bottom slab 7; Ground 11, 13, 13a, 13a ′; Tensile material 20, 20b; 21; lower part 22; upper part 30; sheath tube 131; fixing part 200; notch lower surface 201, 301; filler

Claims (14)

A concrete cylindrical wall body in which prestress due to a longitudinal tension material is introduced in the lower part,
A wall body, wherein at least one end of the tendon is fixed at a fixing position on an inner side surface of the wall body.   The wall body according to claim 1, wherein the tendon is inclined in a substantially straight line so as to go outward as it goes downward.   The wall body according to claim 1, wherein the fixing position is a notch provided on an inner side surface of the wall body.   The wall body according to claim 1, wherein the fixing position is a protrusion provided on an inner side surface of the wall body.   The wall according to any one of claims 1 to 4, wherein an outer side surface of a lower portion of the wall is widened outward with respect to an upper portion thereof. The outer side surface of the lower part of the wall body is inclined in a substantially straight line so as to go outward as it goes downward,
The wall body according to claim 5, wherein the tendon is eccentric to the outside of the center in the thickness direction in a lower portion of the wall body. A wall construction method for constructing a concrete cylindrical wall body in which prestress due to a longitudinal tension material is introduced in a lower part,
A wall construction method characterized in that at least one end of the tendon is fixed at a fixing position on an inner side surface of the wall.   8. The wall construction method according to claim 7, wherein tensioning of the tendon is performed after starting placing concrete above the fixing position in the wall.   9. The wall construction method according to claim 7, wherein the tendon is arranged to be inclined substantially linearly so as to go outward as it goes downward.   The wall body construction method according to claim 7, wherein the fixing position is a notch provided on an inner side surface of the wall body.   The wall body construction method according to claim 7, wherein the fixing position is a protrusion provided on an inner side surface of the wall body.   The wall construction method according to any one of claims 7 to 11, wherein the outer side surface of the lower part of the wall is widened outward with respect to the upper part. The outer side surface of the lower part of the wall body is inclined in a substantially straight line so as to go outward as it goes downward,
13. The wall construction method according to claim 12, wherein the tendon is arranged eccentrically outside the center in the thickness direction in a lower portion of the wall.   The tendon is arranged in a substantially U-shape, and one end of the tendon is fixed to the fixing position on the inner side surface of the wall body, and the other end is set to the fixing position on the inner side surface of the wall body. The wall construction method according to any one of claims 7 to 13, wherein the wall is constructed.

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