JP2773621B2 - Tensile anchor anchor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is a deformed steel bar in the ground Gras
Buried in the outgoing material, and by the adhesive force between the deformed steel bar and the grouting material.
The present invention relates to a structure of a fixing portion of a tension type anchor that resists pull-out .

[0002]

2. Description of the Related Art The anchoring portion of an anchor is roughly classified into a tension type and a compression type, and the tension type is such that a deformed steel bar or a stranded wire is embedded and fixed in a grout material in the ground.
The tension type is widely used for ground anchors and the like because of its simple structure and good workability.

[0003]

SUMMARY OF THE INVENTION A conventional tension type anchor
The fixing portion of the chromatography, the increase in such tensile force to the anchor, such as for fatigue grout, as the time has passed the fixing unit
Circumferential cracks occur in the grout material around the rear end , from which groundwater or the like invades and rusts the steel material, reducing the frictional force between the grout material and the steel material. This cracking progresses to the fixing tip from the fixing unit rear end in a short time, finally resulting in the anchor comes off. In this application,
(Before) and after are expressions of anchors sent into the ground
The deep side is the front (front) and the ground side is the back. Thus, once resistant to grout around the fixing portion rear end with respect to pulling vent the fixing portion and a crack occurs becomes while lowering, pulling unplug resistance of the fixing portion is when the first crack occurs Almost the largest. Therefore, in order to increase the pull vent resistance of the fixing unit, even after the fixing unit to a load of prolonged high tensile strength
It is necessary to prevent cracks from being generated in the grout material around the end . When using a steel stranded wire as a steel material, the diameter of the steel stranded wire becomes small due to a large tensile force, and it is separated from the grout material, so the contact part gradually decreases,
Since the frictional force concentrates on the contact portion, a crack is also easily generated.

In the anchoring portion of the conventional tension type anchor, in order to cope with poor durability due to cracking, the diameter of the deformed steel rod is increased to increase the contact area with the grout material to distribute stress. However, this method leads to an increase in cost.

[0005] The present invention relates to a fixing device for a tension type anchor.
Kicking are those aimed at solving the problems as described above, by different fixing mechanism than conventional fixing mechanism, the abrupt pullout resistance force caused by the occurrence of a circumferential crack grout low
The purpose is to prevent the bottom.

[0006]

According to the present invention, there is provided a method for forming a surface on a surface.
Buried deformed steel bars buried in grout material in the ground
Resistance to pulling out due to the adhesive force between the deformed steel bar and the grout material
At the anchoring part of the tension type anchor , a plastic or rubber coating is provided on the surface of the deformed steel rod .
The pull-out resistance generated between the deformed steel bar and the grout material.
Characterized in that they are dispersed in the longitudinal direction of the fixing section.
You.

The grout used in the present invention is:
In addition to hardened cement milk and mortar injected into the fixing part after installing the deformed steel rod, and hardened substances such as cement milk, mortar and concrete injected or poured into the fixing part before installing the deformed steel rod And for simplicity,
It is collectively called grout material. When the grout material is injected or cast into the fixing portion before the installation of the deformed steel bar, it is of course necessary to embed the deformed steel bar in the grout material while the grout material is not hardened.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a tension anchor anchoring section according to the present invention.

FIG. 1A is a longitudinal sectional view of a deformed steel bar serving as a fixing portion of the tension type anchor according to the present invention.
(b) is a longitudinal sectional view showing a connecting portion between the deformed steel bar and the steel stranded wire of the anchoring portion of the tensile anchor of the present invention.

FIG. 2 is a distribution diagram of the axial force applied to the anchoring portion of the tension type anchor, in which the present invention is compared with the conventional one.

As shown in FIG. 1 (a), a bar 3 is usually provided on the deformed steel bar 1 with a bar in a spiral shape. It is not necessary that the peaks 3 are completely continuous in a spiral shape, and they may be connected while being interrupted on the way. In addition, the barn 3 may not have a spiral shape, but may have a shape in which a number of rings are fitted. The surface of the deformed steel bar 1 is covered with a plastic or rubber coating 2 along the uneven surface. In order to cover the surface of the deformed steel bar 1 with the irregularities along the uneven surface, a method of covering a normal heat-shrinkable film tube on the deformed steel bar 1 with the heat and heating the synthetic resin emulsion or rubber latex can be used. A method of forming a relatively thick coating by dipping the deformed steel bar 1 is efficient, but a plastic or rubber film coated with an adhesive may be wound around the surface of the shaped steel bar 1. Alternatively, it may be applied in the form of a paint. The bar-shaped deformed steel bar 1 is buried directly in the grout material 8 in the ground in accordance with a usual anchor anchoring method. When embedding a plurality of barbed deformed steel bars 1 in one grout material, a usual spacer having a plurality of holes is used. In the case of ground anchors steel wire strands in the rear end section with profiled steel bar 1 as shown in FIG. 1 (b) (wires) 4
Are buried in the grout material 8 while being connected via the connection fitting 7. A sheath 5 is used as the steel stranded wire 4 to be connected.
It is preferable to use an unbonded steel stranded wire having
The use of the connection fitting 7 causes a variable cross section to appear at the connection portion. Due to the tension, a large bearing pressure is generated on the rear surface of the deformed section, and there is a possibility that the surrounding grout material 8 may be broken. Therefore, the case of connecting the advance consideration to absorb displacement of by winding a buffer material 6 such as urethane foam to the steel strand 4 side is preferred. If the anchoring portion of the anchor is relatively shallow and do not connect steel strands, etc.
Structure is connected directly to an end after.

The fixing portion of the present invention has the above-mentioned structure, and the surface of the deformed steel bar 1 is covered with a coating 2, and the tensile force applied to the deformed steel bar 1 is applied through the wipe 3 and the coating 2. And transmitted to the grout material 8. The fixing mechanism according to this embodiment will be described with reference to FIG.

[0013] (1) bearing capacity occurs pull tension force to the anchor is concentrated in the rear distrust of 3 to act. The bearing force is transmitted to the grout material 8 while causing the displacement of the coating film 2 to reduce the rigidity. (Because the barbed deformed steel bar 1 and the grout material 8 do not directly adhere to each other, the pull-out resistance based on the frictional force between the two greatly decreases.) (2) Even if the tensile force applied to the anchor increases, the tensile force Since the mechanism of transmission to the grout material 8 does not change,
It can withstand an increase in the tensile force until the entire area of the rear surface can resist.

If the tensile force further increases and exceeds the allowable range, the anchor comes off the grout material 8 along the plane passing through the top of the barn 3.

In any case, in the fixing section of the present invention, there is no phenomenon that the pull-out resistance force sharply decreases due to the generation of the circumferential crack due to the increase in the tensile force, and the fixing portion is proportional to the fixing length. Since the pull-out resistance can be increased or decreased, the range of choice of the design of the tensile force and the choice of the deformed steel rod as the material is greatly expanded.

FIG. 2 is an example of an axial force distribution diagram of the fixing unit, in which the present invention is compared with the conventional one. The dotted line indicates the present invention, and the solid line indicates the conventional fixing portion, but when used stably for a long period of time, when the operation ends in a relatively short time such as the anchor of a temporary structure, and when the anchor is pulled out, the axial force distribution diagram immediately before the anchor is withdrawn. It is. Here, P is the axial force, Pc is the axial force of the conventional type in the circumferential crack generation, and L1 is the fixing length (fixing length )
Part) and L2 indicate a wire length (free length part) . As shown in FIG. 2, the axial force in the conventional fixing unit is almost the frictional force due to the adhesion between the deformed steel bar and the grout material, and the axial force in the fixing length direction drops sharply. Since the axial force in the fixing portion of the present invention is almost the bearing stress on the rear surface of the wiping member 3, the axial force in the fixing length direction gradually decreases. For this reason, in the fixing section of the present invention, the axial force per unit fixing length is considerably lower than that of the conventional type, but it can be sufficiently compensated for by increasing the fixing length, and in the conventional type, the generation of circumferential cracks is reduced. Therefore, it is possible to reach an axial force that could not be reached.

[0017]

According to the present invention, a plastic or rubber coating is interposed between a barbed deformed steel rod and a grout material to prevent the two from sticking to each other, and the main resistance depends on the bearing pressure on the rear surface of the bar. ) It can transmit to the grout material while reducing the rigidity of the tensile stress of the fixing part.

(2) It is possible to gradually reduce the tensile stress of the fixing section in the longitudinal direction of the fixing section.

(3) The design value of the tensile force can be easily followed by increasing or decreasing the length of the fixing length.

(4) Even if a crack occurs in the grout material,
The generation of rust due to infiltration of groundwater can be prevented.

(5) Anchoring in a conventional tension type anchor
Abruptly caused by circumferential cracks in the grout
A reduction in pull-out resistance can be prevented.

There are the following effects.

[Brief description of the drawings]

FIG. 1 (a) is a longitudinal sectional view of a deformed steel rod with a barb serving as a tensile anchor anchoring part of the present invention, and FIG. 1 (b) is a deformed steel rod and steel of a tensile anchor anchoring part of the present invention. It is a longitudinal section showing the connection part with a strand.

FIG. 2 is a distribution diagram of axial force applied to a tension type anchor fixing portion, in which the present invention is compared with a conventional one.

[Explanation of symbols]

1 .... deformed steel bar with swelling, 2 .... coating, 3 .... stiffening, 4
... steel strands, 5 ... sheath, 6 ... cushioning material 7 ... connecting metal fitting, 8 ... grout, ... long design axial force, -
・ Short-term design axial force ・ ・ ・ Axial force immediately before anchor withdrawal,
··· Axial force, Pc ··· Axial force for circumferential crack initiation, L1 ···
Fixing length, L2 ... wire length.

Claims (1)

(57) [Claims] (1) A deformed steel bar with a ditch having a ditch on its surface is provided.
Embedded in grout material in the ground,
Tensile anchor that resists pull-out due to adhesive force
In the fixing section, by providing a plastic or rubber coating on the surface of the deformed steel bar,
The pullout resistance generated between the grout material and the fixing part longitudinal direction
A tension-type anchor anchoring section characterized by being dispersed in the anchor.