JPH0439926Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to a technology for countermeasures against cracks that occur in the walls of multi-story buildings made of reinforced concrete, and in particular,
This invention relates to a building structure that prevents diagonal cracks that occur due to deformation of concrete slabs in walls whose peripheries are constrained by columns and beams.

Conventional technology When constructing a reinforced concrete building with a frame of columns and beams, especially in the direction of the girder of the building, a shear wall is installed between the columns at the outermost end or near the end. A structure that burdens the force is adopted. At this time, this shear wall acts as a rigid slab restrained by the upper and lower beams and the columns on both sides, and the force that attempts to deform the slab into a parallelogram is applied to one side according to the properties of the concrete. It is treated by compressive stress along the diagonal. However, due to this deformation, the concrete elongates in the direction along the other diagonal, and the tensile stress of the concrete cannot follow the wall, which is constrained on all four sides by columns and beams, and in the direction that intersects with the direction of elongation. cracks occur.
Since the horizontal force is applied in the plane of the plate in the vibration direction, the elongation deformation appears in both diagonal directions, and the usual countermeasure for this is to arrange reinforcing bars along the diagonals within the plate. It happened. However, since reinforcing concrete with reinforcing bars depends on the ultimate strength of the steel and includes the allowable elongation of the steel, cracks cannot be avoided in the concrete.

On the other hand, in general reinforced concrete structures, there is a prestressed concrete structure technology that reduces or offsets the tensile stress by applying compressive stress in advance to the tensile stress that occurs in concrete. A wire-shaped steel material is placed inside, and this is tensed to near the allowable value, and the restoring force of the steel material is applied as compressive stress to the concrete. Therefore, cracks will not occur in concrete under tensile stress that does not exceed this prestress.

However, prestressed concrete construction
It is applied to concrete columnar bodies such as columns and beams, and has recently been applied to thick floor slabs, but there are few examples of its application to walls, and it is applied to concrete in the circumferential direction of cylindrical structures. It was limited to the tensile force (ring tension) of

Problems that the invention aims to solve As mentioned above, although it is possible to reinforce concrete by placing reinforcing bars, it is impossible to prevent concrete from cracking. It is.

Furthermore, even if the concept of prestressing is introduced into such reinforced concrete walls, it is unreasonable to apply the prestressing method for columnar concrete, etc., as described above, when trying to control the cracks inherent in the walls. be. In other words, in the case of walls, the distribution of crack stress differs even within the plane of the same wall, and especially in multi-story buildings, the conditions in which crack stress occurs in the wall differ between upper and lower floors. When introducing prestress, it is desirable to provide a rational arrangement of prestress cables accordingly.

Means to Solve the Problems This invention was developed with the aim of preventing cracks that occur due to deformation in walls that are constrained on all sides by columns and beams in multi-story buildings made of reinforced concrete. It is something. The crack prevention structure of the present invention introduces prestress to the concrete wall, which is subject to severe tensile elongation when the constrained wall deforms, across the top and bottom of the frame to apply compressive stress in advance. The gist is that. In the present invention, prestress cables are fixed to the lower surface of the lower beam and the outer upper surface of the upper beam, and are arranged linearly and at a steeper angle than the diagonal direction of the wall, and diagonally inside the wall. It is characterized by introducing compressive force in the direction, changing the amount of prestress for each floor of the building, and on the upper floors, the cable arrangement is crossed in an X shape to introduce even more prestress. As a result, the building of the present invention has achieved a structure in which the countermeasure against cracks, which is provided by reinforcing bars at predetermined positions of the wall, is completely avoided by applying prestress within the wall.

Embodiments The crack prevention structure of the present invention will be explained in detail based on drawings of embodiments.

In Figure 1, 1 shows the entire three-story reinforced concrete building. 2 is a column, 3 is a beam, and the many columns and beams are 2 in order from the end and the bottom.
1, 22, 23...31, 32, 33, 34, each floor has a wall 4 between the pillars 21 and 22, and this wall is 4 from the lower one.
1, 42, 43. Middle pillars 22, 23
The structure of the wall surface between the pillars between... can be arbitrary, such as walls and openings, but between the pillars at the other end of building 1, the structure of the wall surface is arbitrary.
It is the same as Hashirama of 1 and 22, and the detailed number is omitted because it is considered symmetrical.

As shown in FIG. 2, the wall bodies 41, 42, and 43 have reinforced reinforcing bars 5 arranged in multiple reinforcements to increase wall thickness, and are introduced as earthquake-resistant elements in the row direction as earthquake-resistant walls.

In the walls of each floor, prestressing steel members 6 are arranged diagonally and linearly at a steeper angle than the diagonal direction of the walls and at an angle of 45° from the horizontal, as shown in Figure 2. It is located on the center line. Although the steel materials 6 are used as a set of two in FIG. 2, it goes without saying that they can be used as a set of one or two or more depending on the design. In this embodiment, a prestressed twisted steel wire is used as the steel material 6, and an unbonded or bonded method is used with the concrete. Since the prestress cable 6 is set at a steeper angle than the diagonal direction of the wall, two cables 61 and 62 are arranged on the second layer wall 42, and the cable 61
is the column 2 extending from the bottom surface of beam 32 to the top surface of beam 33.
It extends linearly through the inside of the wall 42 toward the outside of the beam 2, is taut from both ends, and is fixed to the lower surface of the beam 32 and the upper surface of the beam 33. Similarly, the cable 62 passes through the wall 42 from the lower surface of the beam 32 to the upper surface of the beam 33 in parallel with the cable 61, and is tensioned and fixed from both ends. The outer surface of the column 21, the inner surface of the column 22, etc. are also associated with these fixing positions, respectively.

In the wall 41 on the first floor, there are three cables 6 with one added in the middle, and the middle cable 63 is fixed only to the upper and lower surfaces of the beams 33 and 32.

The number of cables 6 has further increased in the wall 43 on the third floor, and newly added cables 64, 64
In this case, the upper and lower fixing positions of the cables 61 and 62 on the second floor are reversed. That is, the cables 61 and 62 are crossed in an X-shape from the upper fixing position downward, and from the downward direction are opposite directions outward and inward.

Due to the arrangement of these cables 6, based on the amount of steel for the cables 6 on the second intermediate floor, one will be added on the lower first floor, and two will be added on the upper third floor.
Books are increasing. Of course, the above-mentioned quantities, angles, etc. change according to the design and do not limit the configuration of the invention.

Function The function of the present invention will be explained using the construction method of this building and stress analysis during an earthquake.

The construction of the pillars 2, beams 3, and walls 4 of the building 1 as a reinforced concrete structure is a conventional method and does not require detailed explanation.

The prestress cable 6 is placed in the underground beam 3.
At the time of construction 1, a fixed end 65 is provided on the lower surface of the beam 31, and the cable 6 is extended linearly into the concrete formwork of the wall 41, and is extended to the upper surface of the beam 32 to cover the concrete of the wall 41. Then, the cable 6 is buried in a penetrating state. If the cable 6 is of the bond type, unbond and
In the case of a cable, a predetermined tension is applied after the concrete hardens to introduce compressive prestress into the wall concrete, and the other end is used as a fixed end 65.

Concrete pouring for the structural frame is performed on each floor, and emergency prestressing cables 6 are also placed on each floor.

As an example, if the height of each floor is 4 m, the thickness of the wall is 20 cm as a seismic wall, and two stranded steel wires with a diameter of 17.8 mm are used as the cable 6, concrete with a normal compressive strength of 240 m/cm ² is used. The calculation for introducing prestress to prevent cracking is as follows.

Wall cross-sectional area 400 x 20 = 8000 cm ² Allowable tensile strength of concrete 240 x 1/10 x 1/3 = 8 m/cm ² If prestress is applied using 2/3 of the strength as a guide, 8 x 2/3 = 5.33≒ 5 m/cm ² Required prestress in the wall cross section 5 x 8000 = 40000 Kg = 40 tons Given the yield strength of 33.6 tons for a cable with a diameter of 17.8 mm, 33.6 x planned strain rate 0.8 x effective ultimate proof stress 0.85 x 2
45.7 tons > 45 tons > 40 tons, and it can be seen that the present invention can be implemented with a set of two cables as described above.

Based on the principle like the calculation above, each cable 6
1, 62, 63, and 64, it is possible to introduce prestress according to each wall portion.

When a horizontal force is applied to the building 1 from the left side as shown in Fig. 1, the horizontal force is cumulatively added to the lower floors, and the upper floors are deformed and the tensile stress generated in the walls 41 and 43 is large, so the same It is necessary to increase the amount of prestress applied to the wall cross section. Also, since shrinkage occurs on the upper floors, the arrangement of the cables 6 is doubled on the upper floors.
The additional cable 64 at the other end of the building 1 contributes to the direction in which compressive stress is applied.

Effects of the invention The crack-prevention structure of the invention effectively applies internal compressive force using prestress cables arranged linearly inside the wall, making it possible to prevent cracks.

Moreover, as explained in the section of the function, the arrangement of the prestressing cables is rational, eliminating the need for stress treatment on individual wall surfaces, and stress treatment on the building wall at high speed using structural shaft members. It also represents a new development in prestressed concrete construction.

[Brief explanation of the drawing]

FIG. 1 is an elevational view of a frame structure taking a three-story reinforced concrete building as an example, and FIG. 2 is a detailed sectional view of a wall. 1... Building, 2, 21, 22, 23... Pillar,
3, 31, 32, 33, 34... Beam, 4, 41,
42, 43... Wall, 5... Rebar, 6, 61, 6
2...Steel material, prestress, cable, 63,6
4...Additional cable, 65...Fixed end, fixing end.

Claims (1)

[Scope of utility model registration request] In a multi-story building made of reinforced concrete with a frame structure of columns and beams, and with reinforced concrete walls restrained by columns and beams between the columns near the ends in the girder direction, each floor between the columns is Prestress cables are installed on the center line of the thickness of the wall from the lower surface of the lower beam to the upper surface of the upper beam, running in a straight line at a steeper angle than the diagonal direction of the wall. increase on the lower floor based on the floor,
On the upper floor, the number of cables is increased by adding cables in an X-shaped cross direction from above to below, and a compressive prestress is introduced into the plane of the wall from both ends of each cable. Anti-crack structure on the body.