JP6909581B2 - Construction method of concrete members - Google Patents

Description

The present invention relates to a method of constructing a concrete member.

In the construction of concrete members with a large volume and member thickness such as mass concrete, cracks are likely to occur due to the temperature rise due to the heat of hydration of cement. Therefore, in the construction of concrete members, temperature cracks may be suppressed by cooling the cast concrete by pipe cooling.
For example, Patent Document 1 discloses a concrete cooling method for suppressing a temperature rise of concrete by passing a refrigerant through a sheath pipe piped in concrete. The sheath pipe has a predetermined extension by connecting pipe materials having a length of about 10 m to each other by welding or a screw type joint.

Japanese Unexamined Patent Publication No. 63-50378

When pipe materials are joined by welding, the construction takes time and the work is affected by the weather. Further, since the screw type joint needs to be processed into a pipe material in advance, the processing of the pipe material is costly. In addition, when piping the sheath pipe to an arbitrary shape due to the shape of the concrete member and the buried object embedded in the concrete, it is necessary to process the sheath pipe (pipe material), and the material cost is high. become.
An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to propose a construction method of a concrete member having excellent workability and economy.

In order to solve the above problems, the present invention comprises a preparatory step of assembling a formwork and piping a cooling pipe in the formwork, a placing step of placing concrete in the formwork, and curing of the concrete. It is a method of constructing a concrete member including a curing step, and in the preparatory step, one corrugated hard polyethylene pipe having an inner diameter of 50 mm or less extending from a water storage tank to a drainage tank is piped as the cooling pipe. The curing step is characterized in that a refrigerant is allowed to flow through the cooling pipe. When there is a buried object such as a reinforcing material in the concrete, the corrugated hard polyethylene pipe may be piped while being bent in an arbitrary linear shape.

According to the construction method of the concrete member, since the corrugated hard polyethylene pipe that can be carried in the bundled state is used as the cooling pipe, the piping work of the cooling pipe can be performed easily and inexpensively. That is, since the cooling pipe can be piped in a wide range by one corrugated rigid polyethylene pipe, the labor and cost for connecting the pipe materials can be reduced, and the cost for forming the pipe joint is also reduced. unnecessary. Further, since the corrugated rigid polyethylene pipe can be bent into an arbitrary shape as appropriate, the cost of processing the cooling pipe into an arbitrary shape can be reduced. Further, the corrugated hard polyethylene pipe is lightweight and easy to handle, so that it is excellent in workability.

According to the construction method of the concrete member of the present invention, the concrete member can be constructed with high quality easily and inexpensively.

(A) is a schematic view showing an above-ground LNG tank, and (b) is an enlarged cross-sectional view of a wall body. (A) is a cross-sectional view taken along the line AA of FIG. 1A, and FIG. 1B is a cross-sectional view taken along the line BB. It is a figure which shows a part of the corrugated hard polyethylene pipe. (A) is a cross-sectional view showing the construction status of the first lot, and (b) is a cross-sectional view showing the construction status of the second lot. It is a cross-sectional view which shows the analysis model, (a) is Example, (b) is Comparative Example 1, and (c) is Comparative Example 2. It is the maximum temperature distribution map of each analysis model, (a) is Example, (b) is Comparative Example 1, and (c) is Comparative Example 2. It is the minimum crack exponential distribution map of each analysis model, (a) is Example, (b) is Comparative Example 1, and (c) is Comparative Example 2.

In the present embodiment, a case where a cylindrical wall body (concrete member) W in a plan view constituting the liquid barrier of the above-ground LNG tank shown in FIG. 1A is constructed will be described.
The wall body W is a structure having a prestressed concrete structure that rises from the bottom slab B, and is left on the concrete wall portion 1 made of cast-in-place concrete and the inner surface of the concrete wall portion 1 as shown in FIG. 1 (b). It is provided with a remaining form (inner form) 2. The lower part of the wall body W (1st and 2nd lots W _L1 and W _L2 ) has a larger wall thickness than the other parts. The lower of the wall W, as shown in FIG. 2 (a), is formed in plan view C-shape in a state of having an opening W _O for materials such loading. The opening W _O shields after construction of the other portions of the wall W (other than the bottom). The wall W of the present embodiment, four pilasters W _P are formed at regular intervals in the circumferential direction of the wall W. It should be noted that the number and arrangement of pilasters W _P is not limited.

As shown in FIG. 1 (b), a wall bar 11, a circumferential PC steel material 12, a vertical PC steel material 13, and the like are embedded in the concrete wall portion 1. The wall bar 11 is a combination of vertical bars and horizontal bars in a grid pattern. The circumferential PC steel material 12 is composed of PC steel strands extending from one pilaster to another pilaster, and is inserted through a sheath (not shown) extending in the circumferential direction. The sheath is arranged along the wall bar 11 on the outer peripheral side (opposite side of the remaining formwork 2). The vertical PC steel material 13 is made of a PC steel rod extending from the lower end portion to the upper end portion of the concrete wall portion 1.
Further, a cooling pipe 3 is piped under the concrete wall portion 1. The cooling pipe 3 of the present embodiment is composed of a corrugated rigid polyethylene pipe P having an inner diameter of 30 mm (see FIG. 3). The inner diameter of the cooling pipe 3 is not limited as long as it is 50 mm or less.

The remaining form (inner form) 2 is formed by connecting a plurality of segments (not shown) in the circumferential direction and the vertical direction. The segment is a precast concrete product having a rectangular shape in a front view and an arc shape in a plan view. Although not shown, the segment includes a joint box that opens to the concrete wall 1 side, an insert nut for the outer tank liner plate, an insert nut for the separator, and the concrete wall 1 for integration. Shear transmission members and the like are buried.

The construction of the wall body W is _{divided into multiple lots (W L1} , _WL2 , ...) And started up several meters at a time. The construction method of the wall body W includes a preparatory step, a placing step, and a curing step.
In the preparatory step, the formwork (inner formwork and outer formwork) is assembled, and the wall reinforcement 11, the PC steel materials 12, 13 and the cooling pipe 3 are arranged in the formwork. First, as shown in FIG. 4A, a plurality of segments 21 are connected in the circumferential direction on the upper surface of the bottom plate B to form the remaining formwork (inner formwork) 2. The remaining formwork 2 of the lower lot (for example, the 1st and 2nd lots W _L1 and W _L2 ) has a C-shape in a plan view due to the formation of the opening 22 for carrying in materials and the like (for example, the 1st and 2nd lots W L1 and W L2). See FIG. 2 (a)). In the lots other than the lower lot (for example, the third and subsequent lots), the remaining formwork 2 is formed in an annular shape (ring shape in a plan view) as shown in FIG. 2 (b). The segment 21 of the remaining form 2 is arranged on the upper surface of the bottom plate B and then connected to another adjacent segment 21. The segments 21 are bolted together using a joint box (not shown) provided in each segment 21.
After the inner formwork (remaining formwork) 2 is formed, the necessary wall reinforcements 11 are arranged and the circumferential PC steel material 12 and the vertical PC steel material 13 are installed (see FIG. 1B). The wall reinforcing bar 11 may be built in the state of a reinforcing bar net or a reinforcing bar cage assembled at a reinforcing bar processing plant or the like in the construction site.

In the lower lot (in this embodiment, the 1st and 2nd lots W _L1 and W _L2 ), the cooling pipe 3 is also piped along with the arrangement of the wall reinforcement 11 and the PC steel materials 12 and 13. As shown in FIG. 1A, in the first lot W _L1 , one cooling pipe 3 is piped inside and one outside the wall body W (four in total). The number and arrangement of the cooling pipes 3 are not limited. The cooling pipe 3 is piped so as not to interfere with buried objects such as wall bars 11 and PC steel materials 12 and 13. That is, the cooling pipe 3 is piped while bending a corrugated hard polyethylene pipe in an arbitrary linear manner so as to avoid buried objects such as wall bars 11 and PC steel materials 12 and 13. In the present embodiment, as shown in FIG. 2A, a first cooling pipe 31 extending from the water storage tank to the drainage tank by one corrugated rigid polyethylene pipe P and two corrugated rigid polyethylene pipes. By connecting the pipes P and P, a second cooling pipe 32 extending from the water storage tank to the drainage tank is connected. The corrugated hard polyethylene pipe is carried in a bundle with a maximum length of 200 m. First cooling pipe 31, along the outer surface of the remaining mold 2, piping from the opening W _O up to the pilasters W _P of second clockwise _(hereinafter referred to as "second pilasters W _P2"). On the other hand, the second cooling pipe 32, along the outer surface of the remaining mold 2, piping _(through the opening 22 pilasters W _P of the third _{counter-clockwise)} the second pilasters W _P2 up to. That is, at the lower part of the wall body W, the cooling pipe 3 is piped over the entire length of the wall body W. Incidentally, the second cooling pipe 32, a corrugated rigid polyethylene pipe P together, between the fourth pilasters W _P4 and the third pilasters W _P3, we are joined. End of the cooling pipe 3, at the position of the opening W _O and the second pilasters W _P2, protrudes from the wall W.

Next, as shown in FIG. 4A, the outer form 4 is installed outside the inner form 2 with a gap from the inner form 2. The outer mold 4 is connected to the inner mold 2 via the separators 5 and 5. In the present embodiment, the upper and lower separators 5 and 5 are arranged, but the number of stages of the separator 5 and the arrangement pitch are not limited. The outer formwork 4 has a strength that does not deform due to the lateral pressure of the concrete C.

In the placing process, concrete C is placed between the inner formwork 2 and the outer formwork 3. The concrete C is placed using a concrete pumping pipe.
In the curing process, the concrete C placed between the inner formwork 2 and the outer formwork 4 is cured. At this time, the refrigerant is passed through the cooling pipe 3 to cool the concrete C. One end of the cooling pipe 3 (the end on the opening 22 side) is inserted (connected) into the water tank via a submersible pump, and the other end of the cooling pipe 3 (the end on the pilaster side) is connected to the drain tank. ing. When the submersible pump is driven, the water stored in the water tank is supplied to the cooling pipe 3. The refrigerant is not limited to water, and may be, for example, cold air. Further, the timing at which the refrigerant is passed through the cooling pipe 3 is not limited, and may be started at the same time as the start of placing the concrete C, for example.

When the construction of the first lot W _L1 is completed, the second and subsequent lots W _L2 are formed. In the second and subsequent lots, as shown in FIG. 4B, after forming the upper inner formwork by connecting a plurality of segments 21 in the circumferential direction and the vertical direction on the upper surface of the inner formwork 2, the wall reinforcement 11 , PC steel materials 12, 13 and, if necessary, cooling pipes are arranged. In the second lot, in the second lot, three stages (six in total) of cooling pipes are piped to the inner surface side and the outer surface side of the wall body W, respectively. On the other hand, the cooling pipe shall not be piped in the third and subsequent lots. Then, after opening a gap from the upper inner form 22 and installing the upper outer form 31 on the outside of the upper inner form 22, concrete is poured between the upper inner form and the upper outer form.
When all the lots are completed, a tensile force is applied to the circumferential PC steel material 12 and the vertical PC steel material 13, and prestress is introduced into the wall body W.

According to the construction method of the wall body W (concrete member) of the present embodiment, the piping work of the cooling pipe 3 can be performed easily and inexpensively. Since the cooling pipe 3 uses a corrugated hard polyethylene pipe carried in in a bundled state, one pipe material can be piped in a wide range. Therefore, there is no need for the cost of forming the pipe joint. Further, by eliminating or reducing the number of joints between the pipe materials, there is no concern about water leakage.

Further, since the corrugated rigid polyethylene pipe P can be appropriately bent into an arbitrary shape, it is possible to reduce the labor and cost for processing the cooling pipe 3 into an arbitrary shape. That is, when piping a cooling pipe with a sheath pipe or the like, it is necessary to combine the straight pipe and the bent pipe while appropriately joining them, but in the present embodiment, the trouble is saved by using the corrugated hard polyethylene pipe P. can do. Further, the corrugated hard polyethylene tube P is lightweight and easy to handle, so that it is excellent in workability.

Further, according to the construction method of the wall body W (concrete member) of the present embodiment, the concrete can be cooled more efficiently by arranging the cooling pipes in two rows. Further, the flow rate of the cooling water (refrigerant) can be reduced as compared with the conventional cooling pipe using a sheath pipe or the like. Therefore, it is possible to reduce the space and container for storing the cooling water, and it is also possible to save labor (reduce the scale) of the pumping means such as the cooling water cooling device and the pump.

Hereinafter, the results of analyzing the temperature distribution and the crack exponential distribution when the concrete member is constructed by the construction method of the concrete member of the present embodiment are shown. In this analysis (Example), as shown in FIG. 5A, a wall is formed on _{the outer surface of the residual formwork 2 having a wall thickness t 1} = 140 mm with a moderate heat Portland cement having a design standard strength f'ck = 40 N / mm ^2. A concrete wall portion 1 having a thickness t ₂ = 1360 mm, a first lot height h ₁ = 1800 mm, and a second lot height h _{2 = 3000 mm was formed.} The concrete wall 1, the first lot W _L1 in this 4 have been pipe cooling pipes 3 of the (2 × 2 stages), the second lot W _L2 cooling of this 6 (2 × 3 stages) The pipe is piped. A corrugated hard polyethylene pipe having a diameter of 30 mm was used for the cooling pipe 3. The temperature of the cooling water to be passed through the respective cooling pipe 3, a first lot _{W L1} is 28 ° C., the second lot _{W L2} and 24 ° C., water flow rate of the cooling water was 60cm / sec.

Further, as Comparative Example 1, as shown in FIG. 5 (b), an analysis was also performed in the case where the cooling pipe was not piped.
Further, as Comparative Example 2, as shown in FIG. 5 (c), and five pipes cooling pipe 3 made of a sheath tube of φ90mm First lot W _L1 in a row arrangement, one row disposed on the second lot W _L2 The analysis was also performed for the case where 9 pipes were installed in.

6 (a) to 6 (c) show the maximum temperature distributions of Examples and Comparative Examples 1 and 2, and FIGS. 7 (a) to 7 (c) show the minimum crack exponential distribution. As shown in FIGS. 6 (a) to 6 (c), in the embodiment (FIG. 6 (a)), the _{maximum temperature in the first lot WL1} is 48 ° C., the maximum temperature in the second lot is 47 ° C., and cooling is performed. If pipe not pipe (as compared in FIG. 6 (b), in the first lot W _L1 3 ° C., resulted capable to decrease 6 ° C. temperature with a second lot W _L2. the first lot W _L1 Even when compared with Comparative Example 2 (FIG. 6 (c)) in which the maximum temperatures of the second lot _{WL2 were 49 ° C. and 46 ° C., respectively, the same cooling effect was obtained.}

Further, as shown in FIG. 7 (a), the minimum cracking index of embodiment, the first lot _{W L1} 2.76, is a target value of the second lot _{W L2} at 2.49, and the minimum cracking index The result was that we could clear 1.85. Incidentally, as shown in FIG. 7 (b), in Comparative Example 1 without piping cooling pipe, a minimum cracking index in the first lot _{W L1} 1.75, the second lot _{W L2} 1.66, and the minimum cracking The index (1.85) could not be cleared. Further, as shown in FIG. 7 (c), in Comparative Example 2, the minimum crack index in the first lot _{W L1} 2.75, 2.35 becomes the second lot _{W L2,} examples and results comparable was gotten.
The water flow rate of ^{Example 2 was 15 m 3} / hour, whereas the water flow rate of Comparative Example 2 was 215 m ³ / hour. Therefore, according to the examples, it was demonstrated that the cooling effect of concrete and the crack suppressing effect can be obtained with a smaller water flow rate (water flow rate of 10% or less) as compared with Comparative Example 2.

The embodiment according to the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and each of the above-mentioned components can be appropriately modified without departing from the spirit of the present invention.
In the above embodiment, the case of constructing the wall body W of the liquid barrier of the above-ground LNG tank has been described, but the concrete member to be constructed by the method of constructing the concrete member of the present invention is not limited.

1 Concrete wall 2 Remaining formwork (inner formwork)
3 Cooling pipe 4 Outer formwork B Bottom slab C Concrete W Wall body

Claims (2)

The preparatory process of assembling the formwork and piping the cooling pipe in the formwork,
The casting process of placing concrete in the formwork and
A method of constructing a concrete member including a curing process for curing the concrete.
In the preparatory step, one corrugated hard polyethylene pipe having an inner diameter of 50 mm or less extending from the water storage tank to the drainage tank is piped as the cooling pipe.
A method for constructing a concrete member, which comprises passing a refrigerant through the cooling pipe in the curing step. The method for constructing a concrete member according to claim 1, wherein in the preparatory step, the corrugated hard polyethylene pipe is piped while being bent in an arbitrary linear manner.

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