Anchor bolt replacement method

Abstract

To restore a state in which a sufficient fixing strength can be obtained by an anchor bolt without installing a new anchor bolt in another place, even when the anchor bolt buried and installed during construction of a concrete structure is deteriorated.SOLUTION: An anchor bolt insertion hole provided in a base plate fixed by an anchor bolt buried and installed in a concrete structure is deformed into an inspection hole with a larger diameter. In an end face of the anchor bolt exposed to the ground surface, a pilot hole including the center point of the end face and with a diameter smaller than the outer diameter of the anchor bolt is drilled. An annular hole with a diameter smaller than the diameter of the inspection hole and larger than the outer diameter of the anchor bolt is drilled around the anchor bolt. The anchor bolt is cut while a drill bit with a diameter approximately equal to the outer diameter of the anchor bolt and smaller than the diameter of the annular hole is inserted into the annular hole, starting from the pilot hole, thereby forming an anchor hole for a newly installed anchor bolt.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for replacing an anchor bolt used for fixing an object to a concrete structure. [Background technology]

[0002] As anchor bolts used to secure an object to a concrete structure, in addition to anchor bolts that are buried and installed when the concrete structure is constructed, post-installed anchors that are installed after the concrete structure is constructed are known.

[0003] Some post-installed anchors are designed to be removed after installation. For example, the undercut anchor disclosed in JP 10-103317 A comprises an anchor rod with an expanding cone-shaped portion and a sleeve that is movable and rotatable relative to the anchor rod, and the cutting blade of the sleeve is expanded in the radial direction by the cone-shaped portion, and even after the anchor is installed by cutting an undercut into the wall of a cylindrical receiving hole (anchor hole), the expanded portion can be narrowed by pulling out the sleeve, and the anchor can be removed from the anchor hole. JP 2000-303461 A also discloses a groove structure of the sleeve that is suitable for pulling out an undercut anchor that has been installed.

[0004] In addition, the anchor bolt disclosed in JP 2020-169472 is similarly inserted into a cylindrical sleeve having an expansion portion on one axial side, and has a tapered portion that expands the expansion portion of the sleeve. Even after being installed once, the anchor bolt can be removed from the anchor hole by pulling the sleeve out of the pilot hole (anchor hole). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 10-103317 [Patent Document 2] Patent Publication No. 2000-303461 [Patent Document 3] Patent Publication No. 2020-169472 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] As mentioned above, post-installed anchors can be removed even after they have been installed. However, if the anchor bolts that were buried and installed when constructing a concrete structure deteriorate due to the effects of rainwater, sea breezes, antifreeze agents, etc., in order to restore the anchor bolts to a state where sufficient fixing strength can be obtained, new anchor bolts must be installed in another location and the object to be fixed must be moved, which requires a lot of time and effort.

[0007] Therefore, an object of the present invention is to provide an anchor bolt replacement method that can restore a state in which a sufficient fixing strength can be obtained by an anchor bolt, even if the anchor bolt buried and installed during the construction of a concrete structure has deteriorated, without having to install a new anchor bolt in another location. [Means for solving the problem]

[0008] In a first anchor bolt replacement method according to the present invention, an anchor bolt insertion hole provided in a base plate fixed by an anchor bolt buried in a concrete structure is transformed into an inspection hole having a larger diameter. Next, a pilot hole including the center point of the end face and having a diameter smaller than the outer diameter of the anchor bolt is drilled in the end face of the anchor bolt exposed to the ground surface, and an annular hole having a diameter smaller than the diameter of the inspection hole and larger than the outer diameter of the anchor bolt is drilled around the anchor bolt. Then, starting from the pilot hole, the anchor bolt is cut while a drill bit having a diameter approximately equal to the outer diameter of the anchor bolt and smaller than the diameter of the annular hole is inserted into the annular hole, thereby forming an anchor hole for a newly installed anchor bolt.

[0009] In a second anchor bolt replacement method according to the present invention, an anchor bolt insertion hole provided in a base plate fixed by an anchor bolt buried in a concrete structure is transformed into an inspection hole with a larger diameter. Then, an annular hole having a diameter smaller than the diameter of the inspection hole and larger than the outer diameter of the anchor bolt, and deeper than the bent portion on the buried tip side of the anchor bolt, is drilled around the anchor bolt. Then, the bent portion separated from the straight portion of the anchor bolt is left in the ground, and the core including the straight portion of the anchor bolt inside the annular hole is pulled out to form an anchor hole for a new post-installed anchor bolt. Effect of the Invention

[0010] According to the first anchor bolt replacement method of the present invention, a post-installed anchor can be newly installed in an anchor hole formed by cutting an anchor bolt installed underground. According to the second anchor bolt replacement method of the present invention, a bent portion separated from the straight portion of the anchor bolt is left in the ground, and a post-installed anchor can be newly installed in an anchor hole formed by pulling out a core including the straight portion of the anchor bolt inside the annular hole. Therefore, even if an anchor bolt installed underground during the construction of a concrete structure deteriorates, it can be restored to a state where sufficient fixing strength can be obtained by the anchor bolt without having to install a new anchor bolt in another location. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 shows steps in an embodiment of a method for replacing an anchor bolt according to the present invention, in which (a) is a diagram showing a process of drilling a pilot hole in an end face of the anchor bolt exposed on the ground surface, (b) is a diagram showing a process of drilling annular holes around the anchor bolt to a depth required for the anchor holes of post-installed anchors, and (c) is a diagram showing a process of cutting the anchor bolt to form the anchor holes. [Diagram 2] FIG. 13 is a diagram showing a state in which an anchor hole for installing a post-installed anchor is formed. [Diagram 3] FIG. 13 is a diagram showing the state in which a post-installed anchor is installed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of an anchor bolt replacing method according to the present invention will be described with reference to FIGS. This embodiment is intended to replace anchor bolts used to fasten road accessories such as signs and lighting fixtures to road sides made of concrete.

[0013] The road side portion 1 corresponds to the concrete structure of the present invention, and the anchor bolt 2 is buried and installed during construction. In addition, in Figures 1 to 3, the portion of the anchor bolt 2 buried in the road side portion 1 (hereinafter referred to as "buried portion 21") is shown in a see-through manner through the road side portion 1 for the sake of convenience of explanation.

[0014] The road attachment 3 has a base plate 3 for fixing to the road side portion 1, and the base plate 3 is provided with an anchor bolt insertion hole 32 through which the bolt portion 22 of the anchor bolt 2 protruding from the surface of the road side portion 1 is inserted. The road attachment is arranged in a state in which the bolt portion 22 is inserted through the anchor bolt insertion hole 32, and is fixed to the road side portion 1 by tightening the base plate 31 against the surface of the road side portion 1 with a fixing nut (not shown) that screws into the bolt portion 22.

[0015] In order to replace the anchor bolt 2, first, the anchor bolt insertion hole 32 is transformed into an inspection hole 33 having a larger diameter. There is no limitation on the method for transforming the anchor bolt insertion hole 32 into the inspection hole 33, but it can be performed, for example, by using a known drilling machine. Note that in the state shown in Figures 1 to 3, only one of the multiple anchor bolt insertion holes 32 is transformed into the inspection hole 33.

[0016] The inspection hole 33 is used for visually inspecting the condition of the anchor bolt 2 through a gap formed around the anchor bolt 2, and its diameter dimension is such that a gap necessary for visual inspection work is formed and is larger than the diameter required for an anchor hole for installing a new post-installed anchor to replace the anchor bolt 2.

[0017] Next, a pilot hole is drilled in the end face of the anchor bolt 2 exposed on the ground surface, i.e., in the end face of the bolt portion 22, including the center point of the end face and having a diameter smaller than the outer diameter of the anchor bolt 2. In this embodiment, the hole is drilled using a known drill, but there is no limitation on the drilling method, and other methods may be used depending on the installation state of the anchor bolt 2, etc. Note that, for convenience of illustration, only the drill bit 4 of the drill used for drilling is shown in Fig. 1(a).

[0018] The diameter of the pilot hole is preferably 40 to 60% of the diameter of the anchor bolt 2. For example, if the diameter of the anchor bolt 2 is 24 mm (M24 bolt), it is preferable to use a drill bit 4 with a diameter of φ10 mm.

[0019] After the pilot hole is formed, next, an annular hole 11 having a diameter smaller than that of the inspection hole 33 and larger than the outer diameter of the anchor bolt 2 is drilled around the anchor bolt 2. A known core drill is suitable for forming the annular hole 11. For convenience of illustration, only the drill bit 5 of the core drill is shown in Fig. 1(b).

[0020] The dimensions of the annular hole 11 are those required for an anchor hole to set a new post-installed anchor bolt. The diameter dimension differs depending on the type of post-installed anchor to be used, but it is formed as an anchor hole 12 for the new post-installed anchor bolt. For example, when using an M24 undercut anchor, it is preferable to use a drill bit 5 with a diameter of φ40 mm.

[0021] After the annular hole 11 is formed, the anchor bolt 2 is cut by inserting a drill bit 6 having a diameter approximately equal to the outer diameter of the anchor bolt 2 but smaller than the diameter of the annular hole 11 into the annular hole 11, starting from the previously formed pilot hole.

[0022] After the anchor hole 12 is formed, the inside of the hole is cleaned, and the post-installed anchor bolt 7 is installed, completing the replacement of the anchor bolt 2.

[0023] The depth dimension of the annular hole 11, which is the depth dimension of the anchor hole 12, must correspond to the fixing strength required for the post-installed anchor bolt and the edge clearance dimension of the inspection hole 33. For example, if the edge clearance dimension is 288 mm or more, an M24 undercut anchor can be used to achieve a strength of 240 N / mm, which is generally considered to be sufficient. 2 In order to realize the required pull-out strength, the depth is preferably 160 mm or more.

[0024] However, when the edge clearance is smaller than 288 mm, the depth must be made larger to achieve the same pull-out strength. For example, the edge clearance of the base plate 31 of the existing road accessory structure 3 may be approximately 100 mm. In this case, it is preferable to use an adhesive anchor as the post-installed anchor bolt 7 and to make the depth of the anchor hole 12 larger than when an undercut anchor is used. For example, when an M24 adhesive anchor is used, a pull-out strength of 240 N / mm is required. 2 In order to realize the required pull-out strength, the depth is preferably 540 mm or more.

[0025] If it is necessary to increase the depth dimension of the anchor hole and the annular hole becomes deeper than the bent portion at the buried tip side of the existing anchor bolt, the bent portion of the existing anchor bolt is cut off from the straight portion of the existing anchor bolt by the drill bit of the core drill during the process of forming the annular hole. Therefore, the anchor hole can be formed by pulling out the core including the straight portion of the existing anchor bolt inside the annular hole. In other words, the process of drilling a pilot hole in the end face of the existing anchor bolt exposed to the ground surface (the process shown in Figure 1(a)) and the process of cutting the existing anchor bolt (the process shown in Figure 1(c)) are not necessary. [Explanation of symbols]

[0026] 1 Road side 2 Anchor bolts 3 Road accessories 4, 5, 6 Drill Bits 7 Post-installed anchor bolts 11 Annular foramen 12 Anchor hole 21 Buried section 22 Bolt section 31 Base Plate 32 Anchor bolt insertion hole 33 Inspection hole

Claims

1. The anchor bolt insertion hole provided in the base plate fixed by the anchor bolt buried in the concrete structure is transformed into an inspection hole with a larger diameter, A pilot hole is drilled in an end surface of the anchor bolt exposed on the ground surface, the pilot hole including the center point of the end surface and having a diameter smaller than an outer diameter of the anchor bolt; An annular hole having a diameter smaller than the diameter of the inspection hole and larger than the outer diameter of the anchor bolt is drilled around the anchor bolt, a drill bit having a diameter substantially equal to an outer diameter of the anchor bolt and smaller than a diameter of the annular hole is inserted into the annular hole starting from the pilot hole to cut the anchor bolt, thereby forming an anchor hole for a newly installed post-installed anchor bolt.

2. The anchor bolt insertion hole provided in the base plate fixed by the anchor bolt buried in the concrete structure is transformed into an inspection hole with a larger diameter, An annular hole having a diameter smaller than the diameter of the inspection hole and larger than the outer diameter of the anchor bolt and deeper than the bent portion on the buried tip side of the anchor bolt is drilled around the anchor bolt, a core including the straight portion of the anchor bolt inside the annular hole is pulled out, and an anchor hole for a newly installed post-installed anchor bolt is formed.

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