JPH0329937B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention effectively improves the strength and toughness of reinforced concrete columns in a simple manner.

In the first place, reinforced concrete construction (hereinafter referred to as “RC construction”)
(abbreviated as ) columns are generally compared to steel-framed columns, etc.
Although it is strong against compressive loads, it is weak against tensile, bending, and shear loads, and is hard and brittle, so it has the disadvantage that once a crack occurs, its yield strength decreases rapidly. On the other hand, steel-framed columns have the disadvantage that although they are strong in tension and bending, they are susceptible to compression buckling, and that fire-resistant coatings and anti-corrosion coatings are time-consuming and costly.
Generally speaking, steel reinforced concrete columns are often used in high-rise buildings to take advantage of the advantages of both and compensate for their disadvantages, but this is more labor-intensive and considerably more expensive than RC columns. Another option is to use prestressed concrete columns (hereinafter referred to as "PC construction"), but this requires large-scale equipment and setup, strict quality and construction management, and special technology that makes full use of them. Because of the high construction cost and construction time, it is currently rarely used in general construction, except in special cases with particularly long spans and enormous stress.

In order to remove this barrier, in addition to the conventional full-scale PC structures that introduce large prestresses, namely full pre-stressing (FPC) and partial pre-stressing (PPC) structures, RC structures and
Prestressed reinforced concrete (PRC) construction has been considered as an intermediate structure to PC construction, and its design standards and construction guidelines have recently been established in Ministry of Construction notifications and other publications. Although this method only introduces a mild prestress and does not require large-scale equipment or setup, and quality and construction management are relatively easy, if it is used well, reinforced cocrete construction can be improved. It has remarkable effects on improving strength and toughness, preventing cracks and deflection, reducing beam/slab thickness and weight, securing long span spaces, and improving the quality of buildings.Moreover, it does not cost much. Future development is expected as an easy-to-use and effective structural method.

The present invention further streamlines the design and simplifies construction by devising the arrangement of PC steel strands or PC steel bars (hereinafter collectively referred to as "PC tendons") and the method of tensioning them. This is intended to double the above merits, and will be described in detail below based on embodiments.

First, install PCs in the reinforced concrete foundation or foundation beam 2, and then at the four corners of the pillar 1 that will rise.
The lower end fixing portion 4a of the tendon is buried with a fixing fitting 4b attached to its lower end and a joint fitting 4j attached to its upper end. After pouring concrete for the foundation and foundation beams,
Inside the main reinforcement 1a and hoop 1b of the pillar 1 on the lowest floor,
Bending each floor into an X-shape in the diagonal direction of the column cross section, multiple floors are successively bent, a steel pipe sheath 5 with a built-in PC tendon 4 is built, and the lower end of the PC tendon 4 is connected to a fitting 4.
j to hold the steel pipe sheath 5 in its proper position, and concrete for the lowest floor is poured. In this case, at the junction with the large burr 3 at the top of the lowest floor column,
Generally, as shown in Figs. 1 and 2, the steel pipe sheath 5 rises vertically on the outside of the intersecting large beam main reinforcements 3a just inside the main reinforcements at the four corners of the column 1, and then similarly on the upper floor. Fold in the diagonal direction of
Place it in a shape.

The arrows (--→) in FIG. 1 indicate the direction of this X shape in the horizontal projection plane. On the upper floor as well, the steel pipe sheath 5 containing the PC tendons 4 is held in its proper position, and the required reinforcement and concrete pouring are carried out, and the same operations are repeated to construct a desired plurality of floors. After the required strength of the concrete has been achieved, the upper end of the PC tendon inside the steel pipe sheath is tightened with a jack or the like at the top of the multiple floors and fixed with a fixing fitting, and the steel pipe sheath is attached from the base of the column on the lowest floor. By press-fitting the grout into the PC tendon 4 with a pump until it overflows from the upper end,
The gap between the inner surface of the steel pipe sheath 5 and the inner surface of the steel pipe sheath 5 is completely filled with the grout material over the entire length. This introduces vertical prestress into the concrete of this multi-story column.

Note that by selecting the type and diameter of the PC tendon and the magnitude of its tension, the amount of prestress introduced can be freely adjusted. When building a high-rise building with many floors, tension is created by dividing the 2nd or 3rd floor or several floors at a time, and then connecting PC tendons with fittings to build the frame and tensioning the second and subsequent floors. All you have to do is go. In this case, the tension force of the PC tendons on multiple floors of each stage does not have to be the same; for example, the PC tendons are made thinner as they go up to reduce the tension force, and the amount of prestress introduced on each floor is set to a desired value. It can be adjusted to It is well known that the introduction of prestress improves the tensile, bending, and shear strength of reinforced concrete columns and prevents cracks from occurring, so the explanation will be omitted. However, for compressive force, it is necessary to increase the compressive stress level of the concrete by the amount of prestress caused by the tension of the PC tendons, but this value is generally 10 to 50.
Since it is approximately Kgf/cm ² , it can be easily achieved by adjusting the mixture of concrete used, such as by slightly increasing the amount of cement per unit, or by making the cross section of the column slightly thicker.

Next, one of the features of the present invention is that the PC tendons are arranged in an X-shape in the diagonal direction of the cross section of each floor column, and the significance and advantages thereof will be listed, and the synergistic effect of the X-shape arrangement and prestressing will be explained. To summarize, (1) First, by arranging each floor in an X-shape,
The PC tendons simultaneously act as braces or trusses, increasing the column's shear and bending strength accordingly.

(2) Furthermore, by placing them in the diagonal direction of the column cross section, each tendon effectively acts as a brace or truss against horizontal loads in both the X-X direction and the y-y direction, so the minimum number of tendons can be Four PC tendons can handle earthquake loads from all directions.

(3) In general, thin braces such as PC strands or steel rods buckle easily under compressive loads and become ineffective, so only one tension-side brace is effective, but in this case, due to tension, Since the initial tension is applied to the horizontal external force, not only the extension side brace but also the contraction side brace are used only in the tension region, and no compressive stress is generated. The reduction in tension on the contraction side brace also contributes to the horizontal proof stress in the same way as if a compression brace were being stretched, so it is twice as effective as a general brace that does not have tension.

(4) Since the yield load and tensile strength of PC tendons are several times higher than that of reinforcing bars or general steel materials, the effect as a brace requires only a small amount of steel material, and it can fit comfortably within the cross section of a column with normal dimensions. Economical.

(5) Reinforced concrete structures have the disadvantage of being hard, brittle, and lacking in toughness, but by applying this tension brace, it is possible to control cracks in the columns, suppress the growth of cracks even after they occur, and prevent the cracks from occurring once the external force is removed. Since the crack width closes and restores its shape, the toughness of the column is dramatically improved.

(6) Therefore, if prestressed concrete columns with omnidirectional braces and PC tendons are properly designed, high-rise or ultra-high-rise buildings that are generally difficult to design without steel reinforced concrete or steel structures can also be constructed using steel frames. It can be constructed economically and in a short construction period.

(7) Even from the perspective of construction, the 4 parts built into the steel pipe sheath
Just insert the PC tendons in the book and tension and grout multiple floors at once, so it takes only a small amount of effort compared to its great effect.

This is a construction method that can economically increase the strength and toughness of reinforced concrete columns in buildings and other structures using a small amount of steel and simple construction.

Although the most typical embodiment has been described above, the direction of the PC tendon is not necessarily limited to the diagonal direction of the cross section of the column, and all variations are included in the direction and quantity. In other words, if you want to reinforce only one direction of a building, for example, you can tension it by arranging the PC tendons in one direction relative to the cross-section of the columns, on each floor in a single or multiple X-shape, as shown in Figure 3a. , also x-x
−． When reinforcing both the y and y directions, PC tendons may be inserted in the required amount in an X shape parallel to the x, x, and y axes, as shown in Figure 3b.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a tensile prestressed concrete column incorporating PC tendons in an X shape according to the present invention, FIG. 2 is a vertical cross-sectional view thereof, and FIG. 3 is a cross-sectional view of a different embodiment. 1...Column, 1a...Column main reinforcement, 1b...Hoop,
2...Foundation burr, 3...Large burr, 3a...Large burr main reinforcement, 4...PC tendon, 4a...Lower end anchoring part of PC tendon, 4b...Fixer fitting, 4j...Joint metal fitting, 5...... Steel pipe sheath.

Claims (1)

[Claims] 1. For a reinforced concrete column, bury the anchoring part of the lower end of the PC tendon in the foundation or foundation beam directly under the column foot of the lowest floor, and then extend each floor in the diagonal direction of the column cross section or in other directions. A steel pipe sheath with a built-in PC tendon is placed inside the main reinforcement of the column and the hoop, and after concrete is poured and the required strength is achieved, the PC tendon is installed at the top of the multiple floors. Tension the upper edge of the
A prestressed concrete column with an X-shaped built-in PC tendon, which is characterized by press-fitting grout into the steel pipe sheath.