JPS648156B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of constructing cylindrical concrete structures.

Traditionally, concrete structures such as silos and prestressed concrete (hereinafter referred to as PC) tanks have been constructed by assembling steel forms with a height of approximately 1.5 to 1.8 m and pouring concrete into them. It was being implemented. A specific example thereof will be explained in detail with reference to FIGS. 1 and 2.

In the case of FIG. 1, in order to maintain the required distance between the inner and outer formworks 1 and 2, which are arranged radially opposite to each other so as to form a double cylindrical shape, these formworks 1 and 2 are Separator 3 consisting of bolts crossing between
and nuts 4 and 5 screwed onto the separator 3 on the outer surfaces of both formworks 1 and 2, and concrete is poured with reinforcing bars, etc. (not shown) placed between these formworks 1 and 2. A cylindrical concrete structure 6 was constructed.

However, in this construction method, when the concrete structure 6 is completed, the separators 3 remain across the walls of the concrete structure 6, so water leaks easily occur along each separator 3. There was a defect. Also, each separator 3
If a water stop treatment was applied to prevent water leakage in this area, the disadvantage was that it would cost a large amount of money.

In the case of Fig. 2, in order to maintain the required distance between the inner and outer formworks 1 and 2, which are arranged radially opposite each other to form a cylindrical shape, the inner surface of the inner formwork 1 and , Steel materials 7 and 8 such as steel pipes are applied to the outer surface of the outer formwork 2 to hold down these formworks 1 and 2, and reinforcing bars, etc. (not shown) are placed between these formworks 1 and 2. A cylindrical concrete structure 6 was being constructed by pouring concrete.

However, in such a construction method, since there is no separator 3 that connects both formworks 1 and 2, when concrete is poured, the weight of the concrete acts largely on the lower part between both formworks 1 and 2, As a result, the pressure of this concrete acts on the inner formwork 1 to reduce the diameter of the cylindrical body formed by the inner formwork 1, so that the contact surfaces between adjacent formworks 1 are brought into close contact with each other. The force works and there is no problem, but the pressure of this concrete acts on the outer formwork 2 to expand the outer diameter of the cylindrical body formed by the outer formwork 2, so the pressure causes the lower formwork 2 and Steel material 8 stretches,
The outer diameter of the lower part of the outer formwork 2 became larger, and a defect occurred in which a difference in level formed on the outer side of the upper and lower joints 9 of the concrete structure 6.

An object of the present invention is to provide a method for constructing a cylindrical concrete structure that does not cause water leakage or steps.

In the method of constructing a cylindrical concrete structure by arranging inner and outer formwork oppositely at a required interval to form a double cylindrical mold, and pouring concrete between the inner and outer cylindrical molds, Wrap a prestressing steel material around the outer periphery of the outer cylindrical mold, tighten the prestressing steel material in the lower part as concrete is placed in the lower part between the inner and outer cylindrical molds, and then tighten the prestressed steel material in the lower part. When pouring concrete, the PC of that part is
It is characterized by tightening steel materials.

Embodiments of the present invention will be described in detail below with reference to FIGS. 3 and 5. As shown in the figure, in this embodiment, double cylindrical molds 11 and 12 are formed by arranging formworks 1 and 2 facing each other inside and outside at a required interval. Formworks 12' for forming protrusions are provided intermittently, and these cylindrical molds 11, 12
In between, reinforcing bars (not shown) are placed together with the prestressed concrete steel material 13 inserted into the sheath. The inner periphery of the inner cylindrical mold 11 is fixed with a steel material 7 such as a steel pipe, and the outer periphery of the outer cylindrical mold 12 is covered with a PC steel material 14 such as steel wire, stranded steel wire, or steel rod in multiple stages. Both ends of these PC steel materials 14 are fixed with jacks 16 passed through the retaining block 15.
be installed on each.

In this state, concrete is first placed in the lower part between the two cylindrical molds 11 and 12 as shown in FIG. At this time, the outer formwork 2 expands outward due to the weight of the concrete, but by tightening the PC steel material 14 using jacks 16, the original position is maintained and no steps are formed. PC steel material 14
Since it is difficult to stretch compared to ordinary steel, it is possible to minimize the outward expansion of the formwork 2, and it is also difficult to stretch when tightening with the jacks 16, making it easier to hold the formwork 2. can be done. Next, as shown in FIG.
Concrete is poured for the second time, and the PC steel members 14 at that height are similarly tightened to prevent the formwork 2 from expanding outward and to hold the formwork 2 in its original position. The height of each concrete pour is low, and the more times you pour concrete, the lower the lateral pressure, so the tightening effect is more effective.
Accuracy is also good.

Note that the PC steel material 14 is not limited to wire rods, and may be stranded wire rods, bars, or the like.

As explained above, in the method for constructing a cylindrical concrete structure according to the present invention, a prestressing steel material is wrapped around the outer periphery of the outer cylindrical mold, and the prestressing steel material is tightened in parallel with concrete pouring. Since the outer formwork is prevented from expanding due to its own weight and the formwork is held in its original position, a cylindrical concrete structure can be constructed without creating a step in the concrete joint. In addition, compared to regular steel, PC steel can minimize the outward expansion of the formwork, and is also less likely to stretch when tightened in parallel with concrete pouring.
The work of holding the formwork in its original position can also be carried out easily. Furthermore, since the present invention does not use a separator, it is suitable for constructing silos, tanks, etc. where airtightness is important. Furthermore, since a separator is not used, there is an advantage that the cost thereof and the cost required for water stop treatment can be omitted.

[Brief explanation of drawings]

FIGS. 1 and 2 are sectional views showing two examples of implementation states of a conventional method for constructing a cylindrical concrete structure, and FIG. 3 is an example of a method for constructing a cylindrical concrete structure according to the present invention. FIGS. 4 and 5 are cross-sectional views of main parts of the concrete casting mold shown in the construction state, and FIGS. 4 and 5 are cross-sectional views showing the concrete casting state in the construction method of this embodiment. 1, 2...Formwork, 6...Concrete structure,
7... Steel material, 9... Seam, 11, 12... Cylindrical type, 14... PC steel material, 16... Jacket.

Claims (1)

[Claims] 1. A method of constructing a cylindrical concrete structure by arranging inner and outer formwork oppositely at a required interval to form a double cylindrical mold, and pouring concrete between the inner and outer cylindrical molds, A prestressing steel material is wrapped around the outer periphery of the outer cylindrical mold, concrete is poured in the lower part between the inner and outer cylindrical molds, and the prestressed steel material in the lower part is tightened, and then concrete is poured in the lower part. When placing more concrete on top, the area is
A method of constructing a cylindrical concrete structure characterized by tightening prestressing steel.