JPH0320548B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for constructing a circular prestressed concrete tank, and particularly relates to a method for constructing a prestressed concrete tank constructed above ground or semi-underground with foundation piles, bottom slabs, side walls, etc. .

Conventionally, this type of prestressed concrete tank constructed above ground or semi-underground has a foundation pile 1 and a bottom slab 2, and a bottom slab 2 and a side wall 3, as shown in Figure 1.
Rigid joints were used for each joint.

Therefore, it included the following problems.

That is, the first problem is that during the concrete construction of the side wall 3, volume changes due to temperature changes due to the generation of heat of hydration of the concrete, drying shrinkage of the concrete, etc. have already been formed by pouring the concrete. By being constrained by the bottom slab 2 and the foundation piles 1 rigidly connected to the bottom slab 2, cracks 4 occur in the vertical direction of the side wall 3 as shown in FIG.

This crack 4 occurs on both the inside and outside of the side wall 3,
Frequently penetrating the inner and outer surfaces, not only did it reduce the durability of the concrete, but it also caused corrosion of the steel for prestressed concrete buried in the side wall 3, shortening the life of the tank itself.

In order to prevent this crack 4, it is necessary to install a large amount of reinforcing bars near the lower end of the side wall 3, and it is extremely difficult to completely repair the crack 4 that has occurred. The amount of money spent is enormous, and if cracks 4 are left untreated, they will gradually expand due to vibrations such as earthquakes, so it is important to eliminate cracks 4 from this type of tank or make them less likely to occur. was an extremely important technical issue.

The second problem is that in this type of prestressed concrete tank, a sheath such as a steel pipe is buried circumferentially in the side wall 3 in advance when the side wall 3 is formed. A steel material or the like is inserted into this sheath, and this steel material is tensed to introduce prestress force in the circumferential direction to the side wall 3. In this case, in the conventional construction method, the bottom plate 2 and The side wall 3 and the bottom plate 2 are rigidly connected to the foundation pile 1, and the bottom plate 2 cannot be displaced or rotated. Therefore, as shown in FIG. An extremely large vertical bending moment occurs near the joint.

Therefore, in order to resist this huge bending moment, the side wall 3 requires a large thickness of concrete members, steel material for prestressed concrete, etc., which also poses an economical problem.

This invention was made in view of the problems of the conventional construction method as described above, and its purpose is to make it possible to economically construct a prestressed concrete tank without causing cracks in the side wall of the constructed tank. Our goal is to provide a new construction method.

In order to achieve the above-mentioned object, this invention rigidly connects a foundation pile buried underground and a bottom slab formed on the top of the foundation pile, and forms a side wall on the bottom slab. A construction method for a circular tank, in which a bottom slab divided into an outer peripheral edge and an inner peripheral part is separately formed on the foundation pile, and then a side wall with a sheath embedded in advance on the outer peripheral edge is formed. , After introducing a prestress force to the side wall by inserting a tension material into the sheath and tensioning it, concrete is poured between the outer peripheral edge and the inner peripheral part of the bottom plate to form an integral part. It is characterized by becoming

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

In the drawings, the same or corresponding parts will be described using the same reference numerals as in the conventional construction method described above.

FIG. 3 shows an embodiment of a circular tank constructed by the prestressed concrete tank construction method according to the present invention.

The prestressed concrete tank shown in the figure has a bottom plate 2 divided into an outer peripheral edge 2a and an inner peripheral part 2b separately formed on a foundation pile 1, and then a side wall with a sheath embedded in advance on the outer peripheral edge 2a. 3 and introducing a prestress force to the side wall 3, concrete or the like is poured into the bottom part 2c between the outer peripheral edge part 2a and the inner peripheral part 2b.

The foundation piles 1 are cast-in-place concrete piles such as reinforced concrete, and are buried in the ground at appropriate locations, taking into consideration the surrounding soil environment, the size of the tank to be constructed, etc.

The bottom plate 2 consisting of the outer circumferential edge 2a and the inner circumferential edge 2b is made of concrete or the like with reinforcing bars placed at appropriate locations, and it is desirable that the outer circumferential edge 2a be as narrow as possible.

In order to introduce a prestress force into the side wall 3, a steel sheath is buried in the circumferential direction within the side wall 3 in advance, and after the side wall 3 is formed by pouring concrete, etc., at an appropriate time. This is done by inserting a tension material such as a steel rod into the sheath and tensioning this tension material.

A portion 2c between the outer peripheral edge 2a and the inner peripheral portion 2b
It is desirable to secure the minimum necessary width to allow construction of reinforcing bar joints for post-cast concrete.

Next, to explain the construction order, first, as shown in Fig. 4a, after driving the foundation pile 1 as described above into the ground to a predetermined depth, the bottom slab 2 is placed on the foundation pile 1 with the outer peripheral edge 2a. It is divided into inner peripheral portions 2b and formed as shown in FIG. 4b.

Thereafter, a side wall 3 in which a sheath is embedded in advance is formed on the outer peripheral edge 2a, as shown in FIG. 4c.

Next, after introducing a prestress force to the side wall 3 at an appropriate time, as shown in FIG. 4d, the outer peripheral edge 2a and the inner peripheral part 2b are integrated by pouring concrete into the outer part 2c. The construction is completed.

Concrete pouring for the above-mentioned gap 2c should not be carried out until at least the prestressing in the inner circumferential direction of the side wall 3 has been completed, and should be delayed as much as possible without affecting other construction work. It is desirable that the construction be carried out after the deformation of the side wall 3 due to the introduction of the stress force has been completely completed.

In this way, the bottom plate 2 is connected to the outer circumferential edge 2a and the inner circumferential edge 2b.
By dividing the side wall 3 into two parts, the members that restrain volume changes such as drying shrinkage of concrete that occur during the formation of the side wall 3 and deformation due to bending moment due to the introduction of prestress force are the outer peripheral edge 2a of the bottom slab 2 and the foundation pile 1 directly below it. Only 1 foundation pile, 1 foundation pile, as before.
Compared to the case where both the bottom plate 2 and the side walls 3 are rigidly connected, the degree of restraint is significantly reduced, and the occurrence of cracks and vertical bending moments are significantly reduced.

This also significantly reduces the amount of reinforcement in the circumferential direction of the side wall 3 required to prevent cracking, the thickness of the concrete members of the side wall 3 required to resist vertical bending moments, and the steel material for prestressed concrete in the vertical direction. It is also economically advantageous.

FIG. 5 compares the construction method according to the present invention with the conventional construction method, and the displacement of the side wall 3 when the same prestress force is introduced into the side wall 3 is shown by the broken line.The effect of the present invention is the same. As shown on the left side of the figure, this is extremely effective.

As described above, according to the method of constructing a prestressed concrete tank according to the present invention, it is possible to significantly reduce the binding force, effectively prevent cracks from occurring in the side wall of the tank, and introduce prestress force into the side wall. This is an extremely useful construction method that alleviates the bending moment caused by this process, and enables economical design of wall thickness of side walls, such as steel materials for prestressed concrete.

[Brief explanation of drawings]

Figure 1 is a cross-sectional perspective view showing a prestressed concrete tank constructed using the conventional construction method, and Figure 2 shows the moment of inertia when prestress force is introduced to the side wall.
1 shows the case of the conventional construction method, and FIG. 1B shows the construction method of the present invention. FIG. 3 is a cross-sectional view showing a prestressed concrete tank constructed by the construction method of the present invention, and FIG. 4 is a cross-sectional view showing the order of construction, in which construction is performed in order from a to d. FIG. 5 is a cross-sectional view showing the displacement of the side wall when a prestress force is introduced to the side wall. 1...Foundation pile, 2...Bottom slab, 2a...Outer periphery, 2b...Inner periphery, 2c...Between part, 3...Side wall, 4...Crack.

Claims (1)

[Claims] 1. A construction method for a circular tank built above ground or semi-underground, in which a foundation pile buried underground is rigidly connected to a bottom slab formed on the top of the foundation pile, and a side wall is formed on the bottom slab. After separately forming a bottom slab divided into an outer peripheral edge and an inner peripheral part on the foundation pile, a side wall with a sheath embedded in advance is formed on the outer peripheral edge, and a tendon is inserted into the sheath. Made of prestressed concrete characterized by introducing prestress force into the side wall by tensioning the sidewall, and then pouring concrete between the outer peripheral edge and the inner peripheral part of the bottom plate to integrate the base plate. Tank construction method.