JPH06103298B2 - Concrete pull-out test method - Google Patents

Description

Description: [Industrial application] The present invention relates to a test method for determining the pull-out strength of concrete by the pull-out resistance of the embedded metal.

[Prior Art] It has been performed to determine the pull-out strength based on the pull-out resistance of a metal object buried in concrete. Prior art I in this pull-out test is, as shown in FIG. 11A, a test apparatus in which the pull-out shaft 30 is inserted in the center of the pull-out shaft mounting plate 31 and the press-contact plate 32 is attached to the peripheral portion of the pull-out shaft mounting plate 31. To use. A mold 34 is provided around this test device, and concrete 35 is poured or sprayed from the head side of the pull-out shaft 30. No. 11B after concrete 35 hardened
As shown in the figure, the pull-out shaft mounting plate 31 is removed, and the pull-out shaft 30 is pulled out in the direction opposite to the head with a center hole jack 36, etc. Is a method of obtaining the strength by dividing by the shear cross-sectional area.

Prior art II is a test method called a stall torque test, and as shown in FIGS. 12A and 12B, a rotary bolt is used.
After the spindle protrusion 41 attached to 40 is embedded in the concrete 35 and the concrete hardens, the head of the rotating bolt
This is a method in which a rotating torque is applied to 42, the concrete is sheared by the spindle protrusion 41 at the shear fracture surface indicated by the slanted line 43, and the rotation torque obtained at this time is divided by the fracture area to obtain the strength.

Prior art III is a rotary shear test method as shown in FIGS. 13A and 13B. By embedding a rotating cone 46 having several grooves 45 from the top to the bottom of the outer circumference of the cone in concrete, and after the concrete hardens, by giving a rotating torque to the shaft 47 to rotate the rotating cone 46, The strength is obtained by dividing the rotational torque when the concrete in the groove portion 45 is constrained and sheared at a dotted line 48 connecting the protrusions between the groove portions by the fracture area.

[Problems to be Solved by the Invention] Disadvantages of Prior Art I As shown in FIGS. 11B and 11A, in the method of extracting the extraction shaft 30, a test body different from the original structure such as a wall, a pillar, or a digit is used. (Specimen) The concrete 35 of 39 is cast, and after the concrete is hardened, the pull-out shaft mounting plate 31 is removed to pull out the pull-out shaft 30, but when pulling it out, the pressure-contact plate 32, which is a part of the formwork, is pulled out. A large lateral load is applied along with the bending load, causing cracks and the like. Therefore, in order to control the lateral load, it is necessary to provide an outer peripheral ring or a protrusion 38 on the press contact plate 32 (Fig. 11B). This test method does not require the strength of concrete structures such as walls, columns, and digits, but the pull-out strength of the test body 39.

When the pull-out shaft 30 is pulled out from concrete, stress is concentrated from the head of the pull-out shaft, and the structure begins to break from the head, and the structure is liable to be totally destroyed. Depending on the concrete strength development state, the shear fracture surface has various shapes, and there is no problem for strength determination, but there may be some difference between when the concrete strength is low and when it is high.

Although it is possible to improve the pull-out test equipment and use it to judge the strength of concrete structures, the fracture surface caused by pulling out is damaged in a cone shape over the front surface, so it is quite necessary for repair after the test. It has the drawback of requiring repair work.

Prior art II Disadvantages of stall torque test It was developed to judge the internal strength of concrete structures, but it is not possible to remove the spindle protrusion 41 embedded in concrete, and the spindle protrusion 41 Concrete that has been destroyed by shear cannot be removed, and must be repaired by a special repairing method such as hardening with an injection agent.

When the concrete is sheared and broken by rotating the spindle protrusion 41, the concrete is destroyed while expanding. Therefore, the flexible tape 44 is wrapped around the spindle protrusion 41 (Fig. 12B) to reduce the expansion. Although some measures are required, there is a drawback that the degree of tape winding thickness affects the concrete.

In concrete shearing, the size of concrete aggregate affects the strength, but in this method, a wire mesh 28 is provided around the spindle protrusion 41 to prevent the aggregate 29 from entering. Not (Fig. 12A).

Prior art III Disadvantages of rotary shear test method A cone having a groove 45 formed on the surface of a conical rotary cone 46 is embedded in concrete, and the rotary cone 46 is rotated by a rotary torque shaft 47, whereby the rotary cone is rotated. The strength is obtained by shearing the concrete constrained in the groove portion of 46 and the concrete around the rotating cone 46, but since the aggregate 49 is sheared when a hard aggregate is present in the groove portion,
There was a defect such as the shearing of aggregate rather than the original strength of concrete, causing variations.

When rotationally sheared, it expands when it is sheared and broken, but the expansive force is transmitted to the outer peripheral concrete, causing cracks in the outer peripheral concrete, resulting in variations in strength and damage to the outer peripheral concrete. was there.

The present invention eliminates the disadvantages of the prior art, such as biting of aggregates, increased repair of concrete structures due to shear fracture, variations in concrete strength due to changes in shear fracture surface, and indirect measurement of concrete. Has an aim.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention embeds a pull-out cone having concave portions at several peripheral positions of a pyramid in a generatrix direction in a concrete structure that is not yet solidified to harden the concrete. After that, the pulling-out cone is pulled out toward the bottom, and the pulling-out strength when the concrete constrained by the recesses from the concrete structure is sheared and broken is characterized.

[Operation] By embedding the extraction cone in a structure that is a hardened body such as concrete according to the depth, and by extracting the extraction cone,
The strength of the structure itself can be obtained by pulling and shearing the concrete constrained by the drawing cone from the structure to obtain the strength.

Shear failure affects strength due to the condition of the aggregate across the shear plane. Since the present invention is designed not to directly shear the aggregate but to tighten the concrete in the recesses at the time of extraction, and to shear the aggregate at a certain angle in the extraction direction, eliminate the direct influence of the aggregate. did.

A strength test is carried out by embedding a drawing cone in a concrete structure, but concrete is soundly secured in the shearing convex part when viewed from the drawing cone, and the fracture surface due to the concave part is very small, so repair is easy. .

Since the pull-out cone forms a recess along the surface of the cone, shear does not concentrate on the weak portion or short-circuit, and it breaks along the pull-out cone, compressing due to the strength of concrete etc. There is no difference in the relationship with the strength.

[Example] FIG. 1 is a perspective view of a drawing cone used in the present invention, and FIGS. 2 and 3 are cross-sectional views showing a procedure of a drawing test method.

As shown in FIG. 1, the extraction cone 10 which is a cone having an apex angle θ ₁ has recesses 12 formed in several generatrix directions, that is, in the inclined portions between the heights H of the cones. Each recess 12 has an opening angle θ ₂ in the generatrix direction and has a predetermined depth h. Recess
Between 12 and 12 is a convex portion 13 formed on the outer peripheral surface of the cone. Further, the pulling-out cone 10 has a pulling-out hole 14 at the center of the bottom thereof for pulling out.

The above is the basic shape of the drawing cone. Next, Fig. 2 and 3
The pull-out test method is shown based on the figure.

The bottom of the extraction cone (10) is brought into close contact with the frame (17), and the fixing bolt (16) is screwed into the extraction hole (14) to be fixed.

Concrete and spray concrete 18 are placed and sprayed on the extraction cone 10 (Fig. 2).

After the concrete 18 has hardened, the fixing bolt 16 is removed and the form 17 is removed.

A pressure contact plate 19 is applied to the outer periphery of the bottom of the pull-out cone 10.

The pull-out bolt 20 is fixed to the pull-out hole 14 of the pull-out cone 10, and the pull-out cone 10 is pulled out by attaching the pull-out bolt 20 to the center hole jack 21 by using the pressure contact plate 19 as a reaction force (Fig. 3).

The withdrawal cone 10 in the concrete 18 breaks along the concrete shear plane. The maximum breaking load at this time is divided by the shearing area to obtain the pulling shear strength.

FIG. 4 is a perspective view showing, with diagonal lines, the concrete portion 22 that has been shear fractured by the pull-out cone 10 after the pull-out and the pull-out test.

Modified Example The extraction cone may be a polygonal cone 11 as shown in FIGS. 5A and 5B. The concave portions are not limited to those having an opening angle, and may be parallel concave grooves 12a as shown in FIG. If the surface of the recess has fine irregularities and the frictional resistance of the surface of the recess is greater than the shear strength of the concrete, the concrete is sheared without slipping.

The shape of the depth of the recess is not limited to a uniform depth, but may be a recessed groove 23 whose depth is arbitrarily increased toward the bottom as shown in FIG. 7A.

The number of the recessed portions 12 or the recessed grooves 12a and 23 may be arbitrarily selected as needed. For example, in the case of a polygon, any number may be set as long as it is a pyramid that is set according to the number of corners (Fig. 7B).

Caps 24 and 25 may be provided when the concrete in the recesses of the pull-out cones 10 and 11 is to be constrained in a certain amount (No. 8A).
(Fig. 8B).

The shape of the concave portion of the pulling-out cone is not limited to the fan-shaped cross-section because the concrete of the concave portion is constrained, and may be a concave shape 26 having a tapered cross-section and a rough surface (FIG. 9).

When the extraction cone is buried deep in the concrete structure, the resistance of the outer periphery of the bottom of the extraction cone is large, so that it is possible to design without using a pressure contact plate or the like.
In that case, the resistance wire 27 is formed on the extension line in the bus-line direction from the bottom (FIGS. 10A and 10B).

[Effects of the Invention] 1 Since a concavity is provided in a cone, and concrete is constrained by the concavity and pulled and sheared, the concrete in the convexity is sound and has very little effect on the concrete structure.

2 Since the concrete that corresponds to the convex portion of the pyramid is sound, the hole due to the removal of the extraction cone has a small fracture surface and is easy to repair.

3 It is only necessary to embed the extraction cone, which is a pyramid, in the concrete and extract it.
The strength of the structure itself can be obtained.

4 The concave portion of the cone has a gentle apex angle θ ₂ ,
The setting of the structure of the recess can be changed and the biting of the aggregate can be eliminated, so that the salient corners of the recess and the aggregate are not bited, and there is no effect of variations in the strength of the aggregate.

5 In the conventional method, as shown in FIGS. 11A to 13, there is a drawback that stress concentrates on concrete in the recesses of the extraction shaft, the spindle projections, and the rotary cone during extraction, but in the present invention, the entire surface is Since the constrained concrete moves integrally with the pull-out cone, stress is not concentrated on a part of the concrete, and variations in strength do not occur.

[Brief description of drawings]

FIG. 1 is a perspective view of a drawing cone used in the present invention, and FIG.
FIG. 3 and FIG. 3 are sectional views showing a procedure for carrying out the method of the present invention, FIG. 4 is a perspective view showing a drawing direction and a portion which is sheared and broken, and FIGS. 5A to 9 are modification examples of a drawing cone. Figure,
FIG. 10A and FIG. 10B are sectional views showing the resistance wire around the bottom outer circumference of the drawing cone in another example of the test method, and FIGS. 11A to 13B are sectional views of the conventional method. 10, 11 Drawout cone, 12 ...... Recess, 12a, 23 ...... Groove, 14 ...... Extraction hole, 16 ...... Fixing bolt, 20 ...... Extraction bolt.

Claims (2)

[Claims] 1. Recesses (12) in the generatrix direction at several locations on the outer circumference of the cone.
The extraction cones (10) and (11) formed with (12a) are embedded in a concrete structure that has not solidified yet, and after the concrete (18) has hardened, the extraction cones (10) and (11) are directed toward the bottom of the cone. A pull-out test method for concrete, characterized in that the pull-out strength when the concrete constrained by the recesses (12) (12a) is subjected to shear failure is drawn. 2. The pull-out test method for concrete according to claim 1, wherein the recesses (12) (12a) gradually increase in width from the top to the bottom of the cone.