JP3031530B2 - How to build a concrete pier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for constructing a concrete pier and a precast formwork.

[0002]

2. Description of the Related Art Conventionally, when constructing a reinforced concrete structure, it is common practice to assemble a band reinforcing bar by directly binding it to a main reinforcing bar arranged at a site with a binding wire or the like.

On the other hand, in the case of a steel frame concrete structure or a steel frame reinforced concrete structure, since it is difficult to directly bind a steel bar to a steel frame, the steel bar is assembled using a special steel bar or steel material for assembly. Was done by site adjustment.

[0004]

However, in the above-mentioned conventional method, assembling of the reinforcing bar requires a lot of labor and labor and occupies much of the construction period. In particular, when a steel frame is used, it is difficult to assemble the strip reinforcing bar, which causes an increase in the construction period. It is dangerous to perform such a work at a site such as a high place, and it is not preferable from the viewpoint of work safety.

[0005] Further, in the conventional method, there is a problem that the covering accuracy of the concrete cannot be obtained because the positional accuracy of the concrete formwork and the reinforcing bar is not sufficient. It has also been pointed out that sufficient assembling accuracy such as the arrangement interval of reinforcing bars cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a method for constructing a concrete structure capable of shortening a construction period, increasing work safety, and improving cover accuracy and assembly accuracy. And to provide a precast formwork used for the construction.

[0007]

The present invention employs the following method to solve the above technical problems. In other words, the pre
A steel frame is built up to the required height on the foundation of the formed pier.
And a reinforcing bar is arranged inside via a reinforcing bar
Forming a frame-shaped precast formwork; and
Stack this precast formwork to surround
And casting concrete into the precast formwork.
Set and harden, the steel frame, the band rebar and precast
And a step of integrating the formwork.

The precast formwork used in this method is:
A belt reinforcement is fixed to an inner surface on which concrete is cast, and a reinforcement is attached to the reinforcement.

Hereinafter, the components will be described. [Concrete bridge pier] Steel reinforced concrete constructed by precast formwork, and steel reinforced concrete using both steel bars and steel frames. [Precast formwork] It is mainly formed of mortar, and is usually manufactured in a factory or the like and assembled on site. After the cast-in-place concrete is hardened, it is part of the structure without demolding. The surface may be decorated or left untouched.
Since this is an industrial product, the durability and aesthetics of a structure constructed using the product can be improved at the manufacturing stage.

Further, various reinforcing materials such as steel fiber, stainless fiber, aramid, vinylon, carbon fiber, glass fiber and the like can be mixed during the production. By incorporating these reinforcing materials, the tensile strength of the precast formwork can be increased. The base mortar of the precast mold has a water-cement ratio of 20 to
It is preferable to use a 60% cement mortar. When a mortar having such a low water cement ratio is used, the resistance to corrosion factors such as salt, carbon dioxide, oxygen, and water is increased, and the durability of the structure can be improved.

When the precast form reinforced as described above is used, it is possible to solve problems such as a large crack width and excessive deformation which are usually a problem in a steel concrete structure. [Band Reinforcing Bar] Also called a shear reinforcing bar, which has a bar-shaped or plate-shaped cross-section, and is fixed via a band-bar reinforcing member to be installed away from the inner surface of the formwork 1. The filling concrete is cast in a state where the belt reinforcing bar does not come into contact with the steel frame or the reinforcing bar installed inside. [Band Reinforcement Attachment] The band rebar attachment can use, for example, an L angle or a small H steel, and supports the band rebar and forms an appropriate gap between the formwork and the band rebar. is there. After casting concrete, this gap becomes the concrete cover. [Steel Frame] The steel frame is preferably an H-shaped steel, but an L-shaped steel can also be used. It is connected to a steel frame or an anchor projecting from the upper surface of the foundation. In addition, if irregularities are provided on the flange surface or the like of the steel frame, the adhesiveness of the concrete is improved, and the integrity with the concrete is obtained. The irregularities may be not only retrofitted ones but also irregularities formed on the surface at the manufacturing stage.

By using the steel frame having the projections formed on the surface as described above, it is possible to suppress the crack width of the structure and improve the toughness.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for constructing a concrete pier according to the present invention will be further described with reference to FIGS.

In the present embodiment, as shown in FIG. 1, a precast member 7 made of a precast concrete formed in a cylindrical shape is provided at the center of a portion surrounded by the formwork 1. Before performing the above, it is erected in the center part of the foundation 2 in advance. However, the installation of the precast member 7 is not essential. The precast member 7 is formed in a circular shape, and has an inner diameter of 3.1 meters and a thickness of 0.1 meters.

The formwork 1 finally becomes the outer wall of the pier, and is made of annularly formed precast concrete. The mold 1 contains a stainless steel reinforcing material in a volume ratio of 1% to 4%, and is formed by connecting curved plates to form an integral annular body. Its cross section is circular, 4.5 meters in diameter, 2.5 meters in height and 5 cm in thickness. The form 1 is suspended by a crane (not shown) and stacked on a foundation 2.
Get the desired height.

As shown in FIG. 4, on the inner surface of the precast form 1, mounting strip reinforcing members 5a formed of an L-shaped steel material are arranged at intervals of 1.2 meters (accordingly, every other one of the precast forms 1). Installed. The band reinforcing bar attachment 5 a is fixed on a ring-shaped flat steel 37 provided at a constant interval on the inner circumference of the precast form 1. Reference numeral 35 denotes a hanging flat steel, and reference numeral 36 denotes a hanging hole. Assembled reinforcing bars 6 are attached to the band reinforcing bar attachment 5a at predetermined intervals. As shown in FIG. 4, the rebar 6 is provided along the height of the pier. Then, the band reinforcing bar 3 is attached to the assembled reinforcing bar 6 so as to be orthogonal to the assembly reinforcing bar 6, and these are formed in a lattice shape. The band reinforcing bars 3 are provided at intervals of approximately 15 cm in the height direction of the precast formwork 1, and are arranged as shown in FIG.

Before or after this step, the steel frame 4 is erected around the precast member 7. A structure (not shown) equal to or more than the steel frame 4 is embedded in the foundation 2 as an anchor in advance, and the steel frame 4 is connected to this structure by bolting. The steel frame 4 is an H-shaped steel (H-318 x 313 x 15 x 2
4) is used, and as shown in FIG. 1, it is erected at a position where it does not come into contact with any of the strip reinforcing bar 3 and the precast member 7. The step of erecting the steel frame 4 may be performed before or after the step of stacking the formwork 1 or the step of installing the precast material 7 and the execution thereof.

By performing the above construction, a semi-finished state as shown in FIG. 2 is obtained. After the formwork 1 and the steel frame 4 are connected to each other by the required number of steps to make the pier a desired height, concrete is poured between the precast member 7 and the formwork 1 and the concrete is hardened to complete. [Test Example 1] A bending-shear test was performed on the steel frame precast concrete structure of the present invention and a conventional reinforced concrete structure. (Specimen) Each specimen was a concrete beam 12 having a length of 4.6 meters, a width of 0.5 meters, and a height of 0.8 meters as shown in FIG.

The test body 1 is a conventional reinforced concrete structure (RC), in which a belt reinforcing bar 11 is arranged in close contact with a main reinforcing bar 10 as shown in FIG. Specimen 2 is a steel precast concrete structure (SC + PC) of the present invention.
FIG. 7A shows a steel bar (H-shaped steel) in which a reinforcing steel strip is arranged as shown in FIG. (Test Method) In the test, two points 1.1 m inward were pressed from bearings provided at 0.4 m from both ends. (Test Results) FIG. 8 shows the relationship between the load of the test piece 1 and the shear reinforcing strain. FIG. 9 shows the relationship between the load of the test body 2 and the shear reinforcing strain. A comparison of the two shows that the steel precast concrete structure has the same shear reinforcing effect as the reinforced concrete structure, despite the arrangement of the strip reinforcing steel away from the steel material. Test Example 2 Positive and negative alternating loading tests were performed on a concrete structure manufactured by the same method as the concrete pier of the present invention. (Specimen) As shown in FIG. 10, a base 2 having a height of 0.75 meters
A hollow cylindrical column 21 having an outer diameter of 0.9 meters, an inner diameter of 0.3 meters, and a height of 2.6 meters was formed on the top of the cylinder.

FIG. 11 is a cross-sectional view showing the internal structure, in which eight H-section steels 23 are provided inside, and a strip rebar 25 is arranged so as not to contact them. (Test Method) An axial force loading jack 30 is provided on the upper surface of the test body, and a PC steel rod 31 is hung from the jack 30 and the lower end thereof is connected to an anchor 32 embedded and fixed in the base 20. . An actuator 35 is provided between the upper end stub 33 and the reaction wall 34, and one end of the actuator 35 is connected to the stub 33.
It is fixed to.

In such a state, the axial force loading jack 3
By applying a predetermined axial force to the entire test piece by pulling the PC steel bar 31 by 0, the actuator 35 was operated to repeatedly apply a horizontal positive / negative force to the stub 33 portion. (Test Results) FIG. 12 shows the horizontal displacement of the loading point of the test piece 1 and FIG. 13 shows the shear reinforcement strain.

From the above results, in the bridge pier according to the present invention, the band reinforcing bar sufficiently exerts the reinforcing effect on the core concrete,
It is recognized that it contributes to improvement in toughness.

As described above, it is understood that the structure of the present invention has strength equal to that of the conventional reinforced concrete structure. In addition, since the pre-cast formwork is used together, the construction period can be significantly shortened and safety can be ensured.

[0024]

According to the present invention, at the time of building a pier, a band reinforcing bar is provided inside the precast formwork, a steel frame is built inside the band reinforcing bar, and concrete is cast inside the formwork. As a result, the assembling of the reinforcing bar and the steel frame becomes extremely easy.

Further, since no scaffolding or formwork is required, the construction period can be greatly reduced, and the work at high places is reduced, so that the safety of workers is high. Moreover, since the reinforcing bar is fixed to the inside of the form via the reinforcing bar attachment, it is possible to improve the covering accuracy of the concrete cover and the reinforcing bar and to improve the strength of the pier.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a pier showing an embodiment of the present invention.

FIG. 2 is a perspective view of a pier construction process showing the embodiment of the present invention.

FIG. 3 is a schematic view showing a precast formwork to which a band reinforcing bar is attached.

FIG. 4 is a side view showing a precast formwork to which a band reinforcing bar is attached.

FIG. 5 is a side view of a beam as a test body in Test Example 1.

FIG. 6 is a cross-sectional view of the test body 1.

FIG. 7 is a sectional view of a test body 2.

FIG. 8 is a graph showing a relationship between a load of a test piece 1 and a shear reinforcing bar strain.

FIG. 9 is a graph showing a relationship between a load of a test body 2 and a shear reinforcing bar strain.

FIG. 10 is a view showing a test body and a test method in Test Example 2.

FIG. 11 is a cross-sectional view of a test body in Test Example 2.

FIG. 12 is a graph showing a relationship between a load and a displacement of a test body in Test Example 2.

FIG. 13 is a graph showing a relationship between a load of a test body and a shear reinforcing bar strain in Test Example 2.

[Explanation of symbols]

 1. Formwork, 2. Foundation, 3. Band reinforcement, 4. Steel frame, 5. Concrete, 5a.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Minoru Tabata 2-10-26 Fujimi, Chiyoda-ku, Tokyo Maeda Construction Industries Co., Ltd. (72) Inventor Kazunori Kawano 2- 10-26 Fujimi, Chiyoda-ku, Tokyo Maeda Within Construction Industry Co., Ltd. (72) Inventor Fuminori Sato 2--10-26 Fujimi, Chiyoda-ku, Tokyo Maeda Construction Industry Co., Ltd. (72) Inventor Toshiya Nagasaki 2--10-26, Fujimi, Chiyoda-ku, Tokyo (72) Inventor Yugo Oka 2-3-2 Uchisaiwai-cho, Chiyoda-ku, Tokyo Kawasaki Steel Corporation (56) References JP-A-61-155521 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) E04C 3/00-3/46 E01D 1/00-23/00

Claims (2)

(57) [Claims] 1. A step of laying a steel frame to a required height on a preformed pier foundation, and a step of forming a frame-shaped precast formwork on which a reinforcing steel bar is arranged via a reinforcing steel fastener inside. A step of stacking a plurality of the precast formwork so as to surround the steel frame, and a step of casting concrete in the precast formwork and hardening to integrate the steel frame, the band reinforcing bar and the precast formwork. How to build concrete piers. 2. The method for constructing a concrete pier according to claim 1, wherein a steel frame having irregularities formed on a surface in contact with the concrete is used.