JPS5921877A - Construction of prestressed concrete tank - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] This invention relates to a construction method for a prestressed concrete tank, and in particular to a construction method for a prestressed concrete tank that effectively utilizes the sheath for inserting tendons buried in the side walls and bottom slab. be.

In general, concrete tanks constructed with a bottom slab and side walls are constructed by first constructing the bottom slab and then forming the side walls on top of it.

In this case, when the concrete poured to form the side wall first expands due to its heat of hydration and then contracts due to the temperature drop, the volume changes in the vicinity of the joint between the side wall and the bottom slab. It was restrained by the bottom plate formed by pouring, and vertical cracks usually appeared from the lower end of the side wall.

These cracks often occur through the side wall, shortening the life of the tank container and causing fatal defects in cases where liquid tightness is required. Ta.

For this reason, in order to prevent the above cracks from occurring, construction methods have been proposed such as adjusting the mix of concrete for forming side walls and placing horizontal reinforcing bars within the side walls to suppress the width of cracks. It was done.

However, in reality, these construction methods lack reliability because it is difficult to assume various factors such as the internal stress caused by the volume change of the concrete 1, which is the cause of the cracks mentioned above, and the resistance to it at the planning stage. be.

In addition, we introduced Press 1 to Reska on the bottom plate and side wall of the tank,
A construction method has also been proposed that suppresses the occurrence of cracks by maintaining the bottom slab and side walls in a compressive stress state.

However, with this construction method, the introduction of 3-Press 1 to Resca into the bottom slab and side walls is done after the bottom slab and side walls have been assimilated, so although it is possible to effectively deal with the expansion of cracks that have occurred, was difficult to suppress.

′? As shown in I'i'Niwachi', the cracks are caused by the heat of hydration of the concrete 1 for forming the side walls, and the introduction of the press 1~reska was done after the concrete 1~ had solidified. This is because it does not act as a restraining force when cracks occur.

By the way, if the cracks that occur on the side wall of the tank are caused by the heat of hydration in the concrete as described above, the fundamental problem can be solved by installing cooling piping inside the side wall with cloth to absorb the heat of hydration. This is a solution.

However, since the side wall thickness of a prestressed concrete tank is relatively thin, it is difficult and uneconomical to install cooling piping, so it cannot be used in reality.

This invention was made in view of the problems mentioned above.
The aim is to create a structure that can reliably control the occurrence of cracks in the side walls of prestressed concrete tanks without sacrificing economic efficiency by effectively using conventional structural members. It is a place that provides construction methods.

In order to achieve the above object, the present invention sequentially connects prestress force introduction/output sheaths buried in the side wall in advance to form a series path of continuous sheaths in the side wall, and forms a side wall in this path. Immediately after concrete is poured, cool liquid is passed through the sheath, and after the side wall concrete has solidified, the liquid inside the sheath is removed.
It is characterized by introducing a prestress force into the side wall by inserting tendons.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a tank constructed by the prestressed concrete tank construction method according to the present invention.

The prestressed concrete tank shown in the figure is constructed of a bottom plate 1 and side walls 2, and a plurality of sheaths 3a are provided at the peripheral end of the disc-shaped bottom plate 1.

3al, 3a31. 3a113 is buried in advance in the cylindrical side wall 2 formed on the bottom plate 1, so that it goes around the side wall 2 once in a state where it is divided into four parts in the circumferential direction, and at a predetermined length in the vertical direction. Sheath 3b in multiple stages at intervals,
3b', 3b'', 311'', etc. are buried in advance.

When constructing a prestressed concrete tank with a J-shaped structure, in the present invention, first, one end of the sheath 3a buried in the bottom plate 1 is connected to a flexible hose 4 as shown in FIG. 1(C). The sheath 3a in the bottom plate 1 is connected to one end of the adjacent sheath 3a' using the flexible hose 4, and the other end of the sheath 3a' is connected to one end of the next adjacent sheath 38'' using the flexible hose 4. , 3a+, 3au, 3ay+7, etc. are connected in series to form an annular series path 5 with both ends open.

A first liquid feeding pump 6 is connected to one end of this annular series line 5.
The hot liquid is sent into the annular series line 5 and discharged from the other end.

The liquid is fed into the annular series line 5 before the concrete 1 is poured to form the side wall 2 on the bottom slab 1. Since it is cold, hot liquid is passed through it to warm the bottom plate 1 to a certain temperature.

Thereafter, the sheath 3b is buried within the side wall 2.

Place 3h', 3+)'', 3h'ri,
Similarly to the bottom plate 1, as shown in FIG. 1(a), the sheath 3
Connect one end of 1) and one end of sheath 31)', and
1]' and one end of the other sheath with the flexible boce 4, the sheaths 3b, 3b', 3b'',
31) By connecting ``'' etc. in series, a spiral series line 7 is created.
A second liquid pump 8 is connected to one end of this spiral series line 7, and a cold liquid is fed into the spiral series line 7 and discharged from the other end.

After that, concrete 1 to 3 is poured and the side wall 2 is constructed.

The liquid is sent to the spiral series line 7 immediately after the concrete is poured to form the side wall 2, and this cool liquid absorbs the heat of hydration of the concrete generated within the side wall 2. It is something.

7- Then, after assimilating the concrete for forming the side wall 2, the liquid supply to the annular series line 5 and the spiral series line 7 is stopped. sheath 3
a, 3a', 3a'', 311, 3b
The flexible bows 4 and liquid pumps 6.8 for connections between the sheaths 3a, 3b'', etc. are removed, and tension materials for prestressed concrete such as steel rods and stranded steel wires are attached to each sheath 3a, 3a', 3.
a'', 3b, 3b', 31+'' are inserted in the same direction and tensioned to complete the construction of the press 1 to rest concrete tank.

Cocote sheath 3a, 3a', 3b
.

3b' etc. may be a conventionally used flexible sheath made of a thin silk plate or one having performance and resistance equal to or higher than that, and there is no need to use a particularly high quality and high performance one.

Also, as shown in FIG. 3, sheaths 3a, 3a'.

3a", 3b, 31)', 3b"
etc. (7) Each Oi end door 1. The connection between the xipul hose and the xipul hose is made using a bolt nut 9 that firmly fixes the two and a rubber backing 10 that increases liquid tightness.

If a tank made of concrete is constructed in the press 1 in the manner described above, the heat of hydration generated from the concrete of the side wall 2 will be reliably absorbed by the cold liquid fed into the spiral series line 7. As a result, the volume change of the concrete 1 becomes extremely small, and when the side wall 2 is formed on the bottom plate 1-), vertical cracks that occur from the lower end of the side wall 2 of C1 are reliably prevented.

The temperature in each of the series circuits 5.7 can be controlled by installing temperature sensors such as thermistors at appropriate locations, or by measuring with a thermometer, etc. to prevent cracks from occurring. It is.

In addition, as in this embodiment, when the temperature inside the bottom plate 1 and the side wall 2 is controlled at the same time, it is possible to keep the temperature of the joint surface of the bottom plate 1 and the side wall 2 at the same level by warming the bottom plate 1 in advance. Moreover, cracks occurring in the side wall 2 can be more completely and precisely prevented and controlled.

In this embodiment, the method 6 for constructing a tank in which a prestress force is introduced into both the bottom plate 1 and the side wall 2 has been described, but the present invention can also be applied to a tank in which a prestress force is introduced only into the side wall 2. Needless to say.

Furthermore, the method of connecting each sheath in the bottom plate 1 and the side wall 2 is not limited to the above embodiment.

As described above, the method for constructing a prestressed concrete tank according to the present invention involves embedding a plurality of sheaths in advance at appropriate locations within the side wall, and sequentially connecting one end of the sheath to the other end of the other adjacent sheath. , forming a series line of continuous sheaths in the side wall, passing cold liquid through the concrete 1 to form the side wall immediately after pouring into this line, and after assimilating the concrete into the side wall, forming a series line of sheaths; After removing the cold liquid of By doing so, it becomes possible to eliminate the volume change difference caused by the humidity difference between the side wall and the bottom slab caused by the heat of hydration of the concrete for forming the side wall. can be prevented and controlled.

In addition, the present invention allows the use of the sheath that has been conventionally used in the construction method of prestressed concrete tanks, and is an extremely useful invention that can achieve the above-mentioned effects without any economic burden. be.

[Brief explanation of the drawing]

Fig. 1 shows a circular tank constructed by the press 1 to rest concrete tank construction method according to the present invention.
1) is a front view, and (C) is a bottom view. FIG. 2 is a schematic diagram showing a state in which the bottom plate and the sheath in the side wall are joined. FIG. 3 is a sectional view showing a state in which the sheath and flexible hose are joined. 1...Bottom plate 2...Side walls 3a, 3a', 3a'', 3a'''
, 3b, 3b', 3b'', 3b・
・・・・・・・・・・・・Sheath 4・・・・・・・・・・・・
...Flexible hose 5 ......... Annular series line 6 ...... First liquid pump 7 ...... ...Spiral series line 8...
......Second liquid feeding pump 9...
...Pol 1 to Natsuto 10...Rubber packing patent applicant Obayashi Co., Ltd. Delivery
Patent Attorney - Ken Iro
＼Figure 1 (C) @Figure 2 Figure 3 1/1

Claims (2)

[Claims] (1) In a construction method for constructing a prestressed concrete circular tank in which a side wall is formed on the bottom slab, a plurality of sheaths are placed in m stages at appropriate locations in advance in the side wall, and one end of the sheath is connected to the other adjacent sheath. One end is sequentially connected to form a series line of continuous sheaths in the side wall, and a cold liquid is passed through the line immediately after pouring the concrete forming the side wall to solidify the concrete on the side wall. A tank made of prestressed concrete, characterized in that after the cold liquid in the contact line is removed and the connection between the sheaths is removed, a tendon material is inserted into the sheath and tensioned to introduce a prestress force to the side wall. construction method. (2) A plurality of sheaths are buried at appropriate locations in the bottom slab in advance to form a series line similar to the side wall, and wet liquid is passed through the line before concrete is poured for the side wall. , after the concrete of the side wall has solidified, the wet liquid in the sheath is removed, the connection between the sheaths is removed, and a tendon material is inserted into the sheath and tensioned to introduce a prestress force to the bottom plate. A construction method for a prestressed concrete tank according to claim 1.