JP7125661B2 - Post-construction anchor construction method - Google Patents

Description

The present invention relates to a method for installing a post-installed anchor.

Conventionally, when connecting other members to an existing concrete structure, anchor bars such as reinforcing bars and bolts are attached to holes formed in the surface of the concrete structure, thereby connecting the anchor bars and other members. A post-construction anchor method is used to connect the

As a post-installed anchor method, for example, a filler containing cement or the like is filled between the inner surface of a hole formed on the surface of an existing concrete structure and the anchor bar, and the filler is hardened by a chemical reaction. According to the method, there is an adhesive anchor construction method in which the anchor bar is fixed with the filler. As the filler, an inorganic filler and an organic filler are used. In addition, as a construction method, there are an injection method and a capsule method.

In addition, by drilling a bottom-enlarged hole in the surface of an existing concrete structure and expanding the bottom-enlarged tip of the anchor bar in the bottom-enlarged hole, the tip of the anchor bar is machined to the inner surface of the bottom-enlarged hole. There is a metal expansion anchor construction method that is fixed to the surface.

Furthermore, a construction method combining the adhesive anchor construction method and the metal expansion anchor construction method, that is, expanding the expanded bottom portion at the tip of the anchor bar in the expanded bottom hole formed in the surface of the existing concrete structure, A method of constructing a post-installed anchor by filling a filler between the inner surface of an enlarged bottom hole and the anchor bar has also been reported (Patent Documents 1 and 2).

JP 2017-172168 A Design Registration No. 1192884

In the metal expansion anchor construction method, if there is a slight gap between the inner surface of the expanded bottom hole and the anchor bar, it becomes susceptible to vibration. As a result, there is a problem that the anchor bar is loosened and the anchor bar is easily pulled out from the concrete structure. Therefore, in the surface of the concrete structure, it is required to drill an enlarged bottom hole with high dimensional accuracy in accordance with the shape of the anchor bar. However, since the anchor bar used in the metal expansion anchor construction method has a complicated shape with an enlarged bottom portion at the tip, it was difficult to drill the enlarged bottom hole with good dimensional accuracy according to the shape. .

Conventionally, a filler is filled between the inner surface of the enlarged bottom hole and the anchor bar to reduce the influence of vibration, thereby suppressing pull-out of the anchor bar. However, when the concrete structure cracks after fixing the anchor bar with the filler, there is a problem that the tensile strength of the anchor bar is significantly reduced.

The present invention was made in order to solve such problems, and it is difficult for the anchor bar to be pulled out, and the decrease in the tensile strength of the anchor bar caused by cracks in the concrete structure is suppressed. It is an object of the present invention to provide a method for constructing a post-installed anchor that enables anchors to be constructed.

The present inventors adjusted the size of the expanded bottom hole formed in the surface of the concrete structure and the size of the anchor bar inserted into the expanded bottom hole within a predetermined range, and used an inorganic filler as the filler to post-install the anchor. It has been found that the anchor bar is less likely to be pulled out and that the installed anchor can be obtained after suppressing the decrease in the tensile strength of the anchor bar caused by cracks in the concrete structure. The gist of the present invention is as follows.

The post-installed anchor construction method according to the present invention is to drill _a hole having a diameter of D1 in the surface of a concrete structure, and then form an enlarged _bottom portion having a maximum diameter of D2 at the bottom of the hole, thereby drilling the enlarged bottom hole. a step of filling the expanded bottom hole with an inorganic filler; a step of inserting an anchor bar having a body portion with a diameter of _D3 and an expanded bottom head portion with a maximum diameter of _D4 into the expanded bottom hole; and a step of expanding the maximum diameter of the expanded bottom head to D5 by driving a muscle, satisfying the following formulas (1) to ( ₄ ).
D4 _- D3≧ _4.0 mm (1)
_D5 /D1≧1.10 ( ₂ )
D5/D2<1.10 _{( 3} )
D5/ _D3 ≧1.40 ( ₄ )

With such a configuration, the anchor bar is less likely to be pulled out, and the anchor bar can be installed after the decrease in the tensile strength of the anchor bar caused by cracks in the concrete structure is suppressed.

In the method for constructing the post-installed anchor, the inorganic filler preferably contains fine aggregate having a particle size of 1 mm or more.

With such a configuration, it is possible to reduce the amount of curing shrinkage caused by curing of the filler, and as a result, it is possible to suppress the occurrence of cracks in the filler. In addition, the arch effect of the aggregate improves the tensile strength.

According to the present invention, it is possible to construct a post-installed anchor that is less likely to pull out of the anchor bar and that the anchor bar can be installed after the decrease in the tensile strength of the anchor bar caused by cracks in the concrete structure is suppressed. can provide a method.

FIG. 1 is a cross-sectional side view showing each step in the method of constructing a post-installed anchor according to the present embodiment. FIGS. 2(a) and 2(b) are cross-sectional side views showing an enlarged bottom hole in a method of constructing a post-installed anchor according to another embodiment. It is a schematic diagram showing an apparatus used for a crack adhesion strength test in an example. It is a schematic diagram showing a hydraulic servo type testing device used for repeated tensile tests in Examples. 4 is a graph showing the bone particle size distribution of silica sand used in each example and each comparative example.

Hereinafter, a method for constructing a post-installed anchor according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional side view showing each step in the method of constructing a post-installed anchor according to the present embodiment.

(Drilling process of enlarged bottom hole)
In the construction method of the post-installed anchor according to the present embodiment, first, after drilling _a hole 3 having a diameter of D1 in the surface ₂ of the concrete structure 1, an expanded bottom portion 4 having a maximum diameter of D2 is formed at the bottom of the hole 3. By doing so, the step of drilling the enlarged-bottom hole 5 is performed.

The hole 3 has _a cylindrical shape with a bottom diameter of D1, and can be drilled using, for example, a hammer drill, a core drill, or the like. In the construction method of the post-installed anchor according to the present embodiment, the diameter D1 of the hole ₃ is determined by the _ratio of the diameter D1 to the maximum diameter D5 after expansion of the expanded bottom head of the anchor muscle described later ₍ D5 _/ D ₁ ) is 1.10 or more, preferably 1.20 or more. The depth of the hole 3 to be drilled is not particularly limited, and can be appropriately changed according to the shape of the anchor muscle to be used.

The enlarged bottom portion 4 is formed at the bottom of the hole 3 and has _a diameter larger than the diameter D1 of the hole 3 in a cross section perpendicular to the axial direction of the hole 3 . In the expanded bottom portion ₄ , the largest diameter among the diameters in a cross section perpendicular to the axial direction is defined as a maximum diameter D2. In the construction method of the post-installed anchor according to the present embodiment, the expanded bottom portion 4 has a truncated cone shape. In this case, the diameter of the _bottom of the truncated cone is the maximum diameter D2.

In the construction method of the post-installed anchor according to the present embodiment, the maximum diameter D2 of the expanded _bottom portion ₄ is the ratio ₍ D ₅ /D ₂ ) is less than 1.10, preferably less than 1.0.

The expanded bottom portion 4 can be formed using, for example, an undercutter, a drill bit for expanding the bottom, or the like. The hole 3 in which the enlarged bottom portion 4 is formed is referred to as an enlarged bottom hole 5 .

(Filling process of filling material)
In the construction method of the post-installed anchor according to the present embodiment, the step of filling the expanded bottom hole 5 with the inorganic filler 6 is performed after the step of drilling the expanded bottom hole.

As the inorganic filler 6, for example, one containing cement and fine aggregate as main components and further containing a water-retaining component can be used. The inorganic filler 6 is hardened by being kneaded with water.

The cement is not particularly limited. Examples include hard cement and alumina cement. Moreover, various mixed cements obtained by mixing fly ash, blast furnace slag, etc. with the Portland cement can also be used. Examples of the ultra-fast hardening cement include crystalline or amorphous calcium such as 11CaO.7Al ₂ O ₃ .CaX ₂ (where X is a halogen element), 12CaO.7Al ₂ O ₃ , and calcium sulfoaluminate (Irwin). Those containing aluminate are mentioned. In particular, from the viewpoint of the balance between the fluidity at the time of filling and the hardening property after filling, it is preferable to use the above-mentioned ultra-rapid hardening cement. The content of the cement is preferably 30 parts by mass or more, more preferably 25 parts by mass or more, relative to 100 parts by mass of the inorganic filler. Moreover, the content is preferably 60 parts by mass or less, and more preferably 57 parts by mass or less.

The fine aggregate is not particularly limited, and general fine aggregates used in concrete or mortar (for example, naturally derived, artificial, recycled, etc.) can be used. can. The fine aggregate preferably has a particle size of 1.0 mm or more and preferably 3.0 mm or less from the viewpoint of suppressing cracking of the filler and improving tensile strength. Also, the coarse grain ratio is preferably 1.00 or more, and preferably 2.45 or less. The grain size and coarse grain ratio of the fine aggregate are measured by the method specified in JIS A 1102 "Aggregate sieving test method". The content of the fine aggregate is preferably 75 parts by mass or more, more preferably 90 parts by mass or more, relative to 100 parts by mass of the cement. Moreover, the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less. Further, the fine aggregate/cement component ratio is preferably 0.75 or more, and preferably 2.0 or less.

The water-retaining component is not particularly limited, and a general water-retaining component used for concrete or mortar can be used. Specific examples include methyl cellulose, hydroxymethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, and mixtures of two or more thereof. In particular, it is preferable to use cellulose-based water-soluble polymers such as methyl cellulose, hydroxymethyl cellulose, and carboxymethyl cellulose.

The inorganic filler 6 may contain other components such as expanding agents, polymers, shrinkage reducing agents, setting retarders, curing accelerators, antirust agents, antifreeze agents, and coloring agents.

(Anchor bar insertion process)
In the construction method of the post-installed anchor according to the present embodiment, the anchor bar 9 having the body portion ₇ with a diameter D3 and the expanded bottom head portion ₈ with the maximum diameter D4 is inserted into the expanded bottom hole 5 after the filling material filling step. perform the process of Although the distance between the inner surface of the enlarged bottom hole 5 and the anchor bar 9 is not particularly limited, it is preferably 1.5 mm or more and 5 mm or less. As the anchor bar 9, for example, a high-strength reinforcing bar (yield strength of the reinforcing bar: 585 N/mm ² or more) can be used.

The trunk portion ₇ is a cylindrical portion having a bottom diameter of D3. Part or all of the circumferential surface of the barrel 7 may be threaded. The enlarged bottom head portion 8 is a portion that is in contact with the trunk portion 7 and has a diameter larger than the diameter D3 of the trunk portion ₇ in a cross section perpendicular to the axial direction of the trunk portion 7 . In the expanded bottom head portion 8, the largest diameter among the diameters in a cross section perpendicular to the axial direction of the trunk portion ₇ is defined as a maximum diameter D4.

The difference between the diameter D3 of the trunk portion ₇ and the maximum diameter D4 of the expanded bottom head portion ₈ of the anchor reinforcement 9 used in the method of constructing the post-installed anchor according to the present embodiment is 4.0 mm or more, preferably It is 6.0 mm or more, more preferably 8.0 mm or more.

_In addition, in the construction method of the post-installed anchor according to the present embodiment, the diameter D3 of the trunk portion ₇ is the ratio ₍ D ₅ /D ₃ ) is 1.40 or more, preferably 1.60 or more, more preferably 1.80 or more.

(Anchor bar driving process)
In the method of constructing the post-installed anchor according to the present embodiment, after the step of inserting the anchor bar, the step of driving the anchor bar ₉ to expand the maximum diameter of the expanded bottom head portion 8 to D5 is performed.

The anchor reinforcement 9 is driven by hitting a portion of the body portion 7 of the anchor reinforcement 9 protruding outward from the surface 2 of the concrete structure 1, for example, using an anchor driving rod or the like. When the expanded bottom head portion 8 of the anchor bar 9 contacts the bottom portion of the expanded bottom hole 5 , the expanded bottom head portion 8 is pushed outward and fixed to the inner surface of the expanded bottom portion 4 of the expanded bottom hole 5 .

By the above-described construction method, the anchor bar is less likely to be pulled out, and the anchor bar can be constructed after the decrease in the tensile strength of the anchor bar caused by cracks in the concrete structure is suppressed.

In this embodiment, the shape of the enlarged bottom portion 4 of the hole 3 is a truncated cone shape. However, the shape of the enlarged _bottom portion 4 of the hole 3 is not particularly limited. For example, as shown in FIG. Alternatively, as shown in FIG. 2(b), _two truncated cones may be combined vertically so that the bottom surfaces having the maximum diameter D2 are in contact with each other.

In this embodiment, the step of filling the filler material is performed after the step of drilling the enlarged bottom hole, and then the step of inserting the anchor bar is performed. However, the method of constructing a post-installed anchor according to the present invention is not limited to such an order, and the step of inserting the anchor bar is performed after the step of drilling the enlarged bottom hole, and then the step of filling the filler material is performed. may

Examples of the present invention will be described below, but the present invention is not limited to the following examples.

(Preparation of post-installed anchors)
After drilling a hole with a diameter of D ₁ in the surface of a concrete structure (strength: σB = 24 N/mm ² ) embedded in a steel pipe, an expanded bottom with a maximum diameter of D ₂ is formed at the bottom of the hole to expand the bottom. A hole was drilled. Next, the expanded bottom hole was filled with an inorganic filler. After that, a reinforcing bar ₍ material: _SWCH10R ) having a trunk with a diameter of _D3 and an expanded bottom head with a maximum diameter of D4 is inserted into the expanded bottom hole, and the reinforcing bar is inserted until the expanded bottom head expands to a maximum diameter of D5. I typed. At that time, the effective embedding length of the reinforcing bars was 54 mm (4.5 da). Table 1 shows the values of D ₁ to D ₅ in the construction methods of each example and each comparative example. In addition, in the construction method of Comparative Example 5, the inorganic filler was not filled.

As the inorganic filler, those having the components and blending amounts shown below were used.
(component)
・Cement: Ultra fast hardening cement (Sumitomo Osaka Cement Co., Ltd., Mild Jet Cement)
・ Fine aggregate: Silica sand (No. 5 sand, No. 6 sand and No. 7 sand were blended at a ratio of 2:1:1 for Example 4. For other examples and comparative examples, No. 3 sand and No. 4 Sand, No. 5 sand, No. 6 sand, and No. 7 sand were blended so that the particle size distribution was the same as that of JIS sand.The bone particle size distribution of each silica sand is shown in Fig. 5.)
・ Water retention component: methyl cellulose thickener (2% aqueous solution, viscosity: 4000 mPa S) (manufactured by Shin-Etsu Chemical Co., Ltd., Hymetrose 90)
(Combination amount)
・Mixing ratio of cement to fine aggregate = 1:1
・ Amount of water-retaining component in cement = 0.05%
・Water cement ratio = 40%

(Crack adhesion strength test)
For the post-installed anchors produced by the installation method of each example and each comparative example, first, an adhesion strength test was performed without causing cracks in the concrete. Next, cracks were generated in the concrete by applying force from the side surface of the steel pipe of the post-installed anchor produced by the construction method of each example and each comparative example. The crack width measured with a π gauge was 0.3 mm. The bond strength test was similarly conducted on the anchors installed after cracking. In addition, in the adhesion strength test, the adhesion strength (the force with which the anchor material is pulled out from the concrete structure) was measured based on the "post-construction anchor test method" of JCAA (Japan Construction Anchor Association). The introduction of cracks into concrete and the bond strength test were conducted using the apparatus shown in FIG. Table 2 shows the measured maximum yield strength and the yield strength residual rate calculated from the maximum yield strength. In addition, 65% or more of the yield strength residual rate was judged as acceptable.

(Repeated tensile test)
Repeated tensile tests were performed on the post-installed anchors produced by the installation method of each example and each comparative example. The repeated tensile test was performed using the hydraulic servo type test device shown in FIG. gone. Table 2 shows the number of repetitions and the state of breakage at breakage. In addition, regarding the determination of the state of breakage, those in which the reinforcing bar was broken were accepted, and those in which the adhesion was broken were rejected.

As can be seen from the results in Table 2, the post-installed anchors produced by the construction methods of Examples 1 to 4, which satisfy all the requirements of the present invention, have a yield strength residual rate of 65% or more in the crack adhesion strength test. It can be seen that the decrease in the tensile strength of the anchor bar caused by In particular, since the post-installed anchors produced by the installation methods of Examples 1 to 3 use inorganic fillers containing fine aggregates with a particle size of 1 mm or more, the crack adhesion strength test shows a yield strength residual rate of 70%. From the above, it can be seen that the decrease in the tensile strength of the anchor bar caused by cracking is further suppressed.

In addition, the post-installed anchors produced by the construction methods of Examples 1 to 4, which satisfy all the requirements of the present invention, have a large number of repetitions at the time of breakage in the repeated tensile test, and are broken due to breakage of the reinforcing bars. It can be seen that muscle pull-out is less likely to occur.

On the other hand, the post-installed anchors produced by the installation methods of Comparative Examples 1 and 2 do not satisfy the requirements of the formula (1) defined in the present invention, so the yield strength residual rate is less than 65% in the crack adhesion strength test. It can be seen that the resulting decrease in tensile strength of the anchor bar is not suppressed.

In addition, since the post-installed anchors produced by the installation methods of Comparative Examples 2 to 4 do not satisfy the requirements of any one or more of the formulas (2) to (4) defined in the present invention, they failed in repeated tensile tests. It can be seen that the pull-out of the anchor muscle is likely to occur because the number of repetitions of time is small and it is destroyed by bond failure.

Furthermore, since the post-installed anchor produced by the installation method of Comparative Example 5 does not contain an inorganic filler, the number of repetitions at breakage in the repeated tensile test is small, and the anchor is broken due to bond failure. It can be seen that muscle pull-out is likely to occur.

REFERENCE SIGNS LIST 1 concrete structure 2 surface 3 hole 4 expanded bottom portion 5 expanded bottom hole 6 inorganic filler 7 trunk portion 8 expanded bottom head portion 9 anchor bar

Claims (2)

_A step of drilling a hole having a diameter of D1 in the surface of a concrete structure and then forming an enlarged _bottom portion having a maximum diameter of D2 at the bottom of the hole to drill the enlarged bottom hole;
A step of filling the expanded bottom hole with an inorganic filler;
a step of inserting an anchor bar having a body portion with a diameter of _D3 and an _enlarged bottom head portion with a maximum diameter of D4 into the enlarged bottom hole;
driving the anchor muscle to expand the maximum diameter of the expanded bottom head to _D5 ;
satisfying the following formulas (1) to (4),
A method for installing a post _- installed anchor, wherein D4 is 22.0 mm or more and 28.0 mm or less .
D4 _- D3≧ _4.0 mm (1)
_D5 /D1≧1.20 ( ₂ )
D5/D2<1.10 _{( 3} )
D5/ _D3 ≧1.60 ( ₄ ) The method of constructing a post-installed anchor according to claim 1, wherein the inorganic filler contains fine aggregate having a particle size of 1 mm or more.

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