JP6049365B2 - Repair method for corroded anchor bolt fixing foundation - Google Patents

Description

  The present invention relates to a method for repairing a corroded anchor bolt fixing foundation.

  In the past earthquake disasters, signs and lighting pillars have been confirmed to fall. Such a structure such as an overturned sign / illuminating column is generally designed to have an earthquake resistant structure in which a base plate is fixed to an existing anchor bolt embedded in a foundation concrete with a nut. As a result of reviewing past earthquake disaster cases, structures such as signs and lighting columns have a small mounting load and a minimum coupling structure, so there are many free surfaces with respect to seismic intensity, and stress diffusion can be received by deflection. It has been found that if the anchoring part (anchor fixing) of the rigid structure is as designed, it can withstand future earthquakes as long as the foundation concrete structure is healthy.

  Therefore, it is a problem whether the existing anchor bolt is healthy. Since anchor bolts are generally made of steel, corrosion and cracking occur with long-term use in the installation environment. In general, the soundness is confirmed by visual inspection, hammering sound confirmation, or a corrosion investigation using, for example, a DAB-1 anchor bolt corrosion amount measuring device (Nakanippon Highway Engineering Tokyo Co., Ltd.).

Such corrosion and cracking are, as shown in FIG. 1, a cross-sectional defect at the interface between the base plate and the foundation concrete of the structure, a cross-sectional defect inside the base plate, a crack at the interface between the base plate and the foundation concrete, and the like.
When it is confirmed that the existing anchor bolt is not healthy, it is necessary to repair the anchor bolt fixing foundation.

As such a repair method, a coupler connection method which is an existing method is known. Hereinafter, the existing construction method will be described with reference to FIGS.
As shown in FIGS. 2 and 3, when the existing anchor bolt has a corrosive site, the existing anchor bolt is cut at the location shown in FIG. 3. A predetermined portion of the basic concrete shown in FIG. 4 is demolished (suspended) with a simple concrete crusher, for example, an electric pick. As shown in FIG. 5, the existing anchor bolt is cut at a predetermined position, and as shown in FIG. 6, when corrosion is in progress, if necessary, after threading is cut again with a threading clip, As shown in FIG. 7, connecting couplers with female threads cut inside the ends are attached. Then, as shown in FIG. 8, the suspension part is filled with non-shrink mortar as a filling, and then the base plate of the original structure is attached to the connection coupler as shown in FIG. Fix it.

This coupler connection method can be constructed with a simple machine, simple construction, no special type of work, and by increasing the number of personnel, the construction quantity can be increased, and some existing anchors are defective. However, there are advantages in terms of workability, such as being able to respond flexibly. In addition, if the construction range is small and protective glasses or a mask are attached, work safety is excellent, and because only materials with excellent weather resistance are used, durability is excellent and economic efficiency is also excellent. . In this way, this construction method has a construction track record with the existing construction method and has some weakening in the structure, but it is excellent in workability and economy, so if there is no large-scale earthquake, etc., there is no problem You can say that.
However, such an existing method obtains a pulling stress by mechanical connection to an existing anchor bolt, and cannot be expected to have an adhesive force due to the filling. In addition, assuming a large-scale earthquake expected in the future, if the corrosion of the existing anchor bolt occurs deep inside the foundation concrete or if it is re-threaded, it will be the same as the design pull-out stress by connecting with the connecting coupler. It is difficult to guarantee a degree of stress at all repair points.

As another repair method, a reconstructed anchor bolt method disclosed in Patent Document 1 below is known. Hereinafter, such a reconstructed anchor bolt method will be described with reference to FIGS.
When the existing anchor bolt has a caustic site, cutting the existing anchor bolt is the same as the existing method described above (see FIGS. 2 and 3).
As shown in FIG. 10, minimum boring is performed only to a predetermined depth by core boring. For example, when the existing anchor bolt diameter is D24, the tearing depth is 45 mm, for D22 it is 40 mm, for D20 it is 35 mm, and for D16 it is 30 mm. As shown in FIG. 11, threading is performed by a special threading device (see reference 70 in FIG. 15 and reference 80 in FIG. 18). However, Patent Document 1 also describes a mode in which a special regenerative anchor bolt (see reference numeral 11 connecting metal fitting in FIG. 6 of Cited Document 1) is fixed to the existing anchor bolt 2 by reducing the diameter without performing thread cutting (quoted). (Refer to FIG. 1, FIG. 5, FIG. 8 in Document 1). A special press-fitting device is also used for such fixing (see reference numeral 30 in FIG. 9 of cited document 1). As shown in FIG. 12, a special regenerative anchor bolt is connected to an existing anchor bolt by screwing (screwing fastening) or biting connection (press fitting) by a reduced diameter, and a sealing material is injected into a suspended portion. Thereafter, if necessary, a special packing is put on the special regeneration anchor bolt as shown in FIG. 14, and a liner plate is installed as shown in FIG. Note that resin or mortar may be used in place of the special seal packing or liner plate (see paragraph 0038 of cited reference 1, FIG. 1). After that, as shown in FIG. 16, the base plate of the structure is fixed to the special regeneration anchor bolt with a normal nut.

  The construction method described in Patent Document 1 has a small construction range, is excellent in work safety if wearing protective glasses and a mask, and is excellent in durability because it uses only materials excellent in weather resistance. Although the completeness is high by using the special reproduction anchor bolt which is a precise part, the construction requires complicated and special equipment and work types, and the workability is poor and the economic efficiency is bad. Furthermore, the construction method described in Patent Document 1 obtains a pulling stress by mechanical connection to an existing anchor bolt, and cannot be expected to have an adhesive force due to filling. Further, the pull-out strength by such mechanical connection is not limited to the guarantee in the case of the bite connection (press-fit) due to the reduced diameter. Furthermore, when a large-scale earthquake expected in the future is assumed, if the corrosion of the existing anchor bolt has occurred deep inside the foundation concrete, or if it has been re-threaded, the design pull-out stress can be reduced by connecting with a special regenerative anchor bolt. It is difficult to guarantee the same level of stress at all repair points. Furthermore, although depending on the material of the special seal packing to be used, there is a possibility that water permeates due to aging corrosion and promotes corrosion of existing anchor bolts. Furthermore, since the special regeneration anchor bolt is a special bolt, it is very expensive and can be replaced, but the maintenance cost becomes high.

  In this way, although some repair methods are known, even when large-scale earthquakes are anticipated in the future, even if the corrosion of existing anchor bolts occurs deep inside the foundation concrete, it is designed. There is still a need to provide further repair methods that can assure all repair locations with stresses comparable to pull-out stresses.

JP 2004-183293 A

  In view of the above problems of the prior art, the problem to be solved by the present invention is a case where the corrosion of the existing anchor bolt has occurred deep inside the foundation concrete, assuming a large-scale earthquake expected in the future. However, it is possible to guarantee a stress equivalent to the design pull-out stress at all repair points, and to provide a further repair method that is excellent in workability, work safety, and economy.

As a result of intensive studies and experiments, the inventors of the present application have found that the above problems can be solved by the following repair method, and have completed the present invention.
That is, the present invention is as follows.
[1] A method for repairing the foundation of a structure in which a base plate of the structure is fixed to a surface exposed male thread portion of an existing anchor bolt embedded in the foundation concrete with a nut, and includes the following steps:
(1) removing the concrete around the existing anchor bolt to a predetermined depth from the surface to form a cylindrical hole around the existing anchor bolt;
(2) A step of cutting and removing the upper part of the anchor bolt at a predetermined position from the bottom surface of the cylindrical hole;
(3) internal thread portion possess at one end a, and a predetermined length of the hollow cylindrical connection unit having a hollow cylindrical portion of larger inner diameter than the outer diameter of the existing anchor bolts on the other end, and the internal thread portion upward And inserting into the cylindrical hole so as to cover the exposed existing anchor bolt;
(4) Filling the cylindrical hole with resin, and curing the connector over a predetermined length in at least a gap between the outer surface of the connector and the inner surface of the cylindrical hole. Fixing the tool to the foundation concrete; and (5) fixing the base plate of the structure to the female thread portion of the connector fixed to the foundation concrete with a bolt;
Structural foundation repair methods including

  [2] The repair method according to [1], further including a step of cutting and removing a surface exposed male thread portion of the existing anchor bolt prior to the step (1).

[3] Instead of the steps (3) and (4), the following steps:
(3 ') a step of filling the resin into the cylindrical bore; and (4') internal thread portion possess at one end a, and the other end of the hollow cylindrical portion of larger inner diameter than the outer diameter of the existing anchor bolts the predetermined length of the hollow cylindrical connection unit having a, and the internal thread portion upward, so as to cover covering the existing anchor bolts, the holes in the resin-like cylinder filled, inserted, the resin, at least the Curing the coupling tool over a substantially predetermined length in a gap between the outer surface of the coupling tool and the inner surface of the cylindrical hole to fix the coupling tool to the foundation concrete;
The repair method according to the above [1] or [2].

  [4] The repair method according to any one of [1] to [3], wherein a depth of the cylindrical hole is 150 mm to 400 mm.

  [5] The repair method according to any one of [1] to [4], wherein a gap between an outer surface of the connector and an inner surface of the cylindrical hole is 5 mm to 30 mm.

  [6] The repair method according to any one of [1] to [5], wherein the resin is an epoxy resin.

  [7] In the step (1), before or after forming a cylindrical hole having a predetermined length around the existing anchor bolt, a hole having a diameter larger than the diameter of the hole on the cylinder is formed from the surface of the foundation concrete. The repair method according to any one of [1] to [6], further including forming to a predetermined depth.

  [8] A step of protecting the cured resin by filling a mortar into the hole having a diameter larger than the diameter of the cylindrical hole formed from the surface of the basic concrete to a predetermined depth. The repair method according to [7], further included before (5).

  The repair method of the structure foundation of the present invention can be constructed with a simple machine, and it is possible to increase the number of constructions by increasing the number of personnel that are simple construction and require special work types. . In addition, the construction range is small, and if safety glasses and masks are attached, work safety is excellent, and because only materials with excellent weather resistance are used, durability is excellent and economic efficiency is also excellent. . The structure foundation repair method of the present invention can be applied regardless of the corrosion state of the existing anchor bolts, etc., so that it can withstand large-scale earthquakes assumed in the future. A uniform pulling stress proportional to the fixing length can be guaranteed.

It is a figure explaining the cross-sectional defect | deletion or fatigue crack state of this anchor bolt by corrosion etc. in the foundation in which the base plate of structures, such as a mark and illumination, is being fixed to the existing anchor bolt embed | buried in the concrete foundation with a nut. It is a figure which shows the corrosion state of the existing anchor bolt. It is a figure which shows the cutting | disconnection of the unnecessary location of the existing anchor bolt. It is a figure explaining the demolition (concrete hand hanging) of the existing foundation concrete part in the coupler connection construction method which is an existing construction method. It is a figure explaining the cutting | disconnection of the existing anchor bolt in the coupler connection construction method which is an existing construction method. It is a figure explaining the thread cutting for the connection coupler from a cut location in the coupler connection construction method which is an existing construction method. It is a figure which shows the state which attached the connection coupler to the existing anchor bolt in the coupler connection construction method which is an existing construction method. It is a figure which shows the state which backfilled the suspended part with the non-shrink mortar in the coupler connection construction method which is the existing construction method. It is a figure which shows the state which attached the fixing bolt to the connection coupler in the coupler connection construction method which is an existing construction method. It is a figure explaining the demolition (core boring) of the existing foundation concrete location in the reproduction | regeneration anchor bolt construction method which is a prior art. It is a figure explaining the re-threading of the existing anchor bolt by the special threading machine in the reproduction | regeneration anchor bolt construction method which is a prior art. It is a figure explaining the attachment of the special reproduction | regeneration anchor bolt in the reproduction | regeneration anchor bolt construction method which is a prior art. It is a figure which shows the state which inject | poured the sealing material into the suspended location in the reproduction | regeneration anchor bolt construction method which is a prior art. It is a figure which shows the state which attached the special packing to the special reproduction | regeneration anchor bolt in the reproduction | regeneration anchor bolt construction method which is a prior art. It is a figure which shows the state which attached the liner plate to the special packing in the reproduction | regeneration anchor bolt construction method which is a prior art. It is a figure which shows the state which attached the fixing nut to the special reproduction | regeneration anchor bolt in the reproduction | regeneration anchor bolt construction method which is a prior art. In the construction method of this invention, it is a figure which shows the state which formed the cylindrical hole by core boring. In the construction method of this invention, it is a figure which shows the state which formed the hole of a diameter larger than the diameter of a cylindrical hole by core boring. Prior to the formation of the cylindrical hole, a hole having a large diameter may be formed. It is a figure which shows the state which cut the existing anchor bolt in the predetermined location in the construction method of this invention. It is a figure which shows the state which inserted the hollow cylindrical connection tool in the existing anchor bolt in the construction method of this invention. In the construction method of this invention, it is a figure which shows the state which filled the cylindrical hole with resin, it was made to harden, and the connection tool was fixed to the foundation concrete. In addition, you may fill with resin prior to insertion of a coupling tool. In the construction method of this invention, it is a figure which shows the state which filled the non-shrink mortar in the hole with a large diameter. In the construction method of this invention, it is a figure which shows the state which attached the fixing bolt to the connection tool. It is a figure which shows the specific example of a connector used for the construction method of this invention.

Hereinafter, the present invention will be described in detail.
The present invention is a method for repairing a foundation of a structure in which a base plate of the structure is fixed to a surface exposed male screw portion of an existing anchor bolt embedded in the foundation concrete with a nut, and includes the following steps:
(1) removing the concrete around the existing anchor bolt to a predetermined depth from the surface to form a cylindrical hole around the existing anchor bolt;
(2) A step of cutting and removing the upper part of the anchor bolt at a predetermined position from the bottom surface of the cylindrical hole;
(3) A step of inserting a hollow cylindrical connector having a predetermined length having a female thread portion on one end side into the cylindrical hole so that the female thread portion is upward and the exposed existing anchor bolt is covered.
(4) filling the cylindrical hole with a resin and curing the resin to fix the connector to the foundation concrete; and (5) the female screw portion of the connector fixed to the foundation concrete, Fastening the base plate of the structure with bolts;
This is a repair method for structural foundations.

Hereinafter, with reference to FIGS. 17-23, the repair method of the structure foundation of this invention is demonstrated.
When the existing anchor bolt has a caustic site, cutting the existing anchor bolt is the same as the existing method described above (see FIGS. 2 and 3).
As shown in FIG. 17, a cylindrical hole is formed at a predetermined depth (perforation or drilling length) by core boring. Such perforation or drilling length corresponds to a fixing length for fixing a connector described below to a base with a resin such as an epoxy resin. The depth of the cylindrical hole is preferably 150 mm to 400 mm. For example, if the existing anchor bolt diameter is D24, the perforation length can be 300 mm, D22 can be 270 mm, D20 can be 250 mm, and D16 can be 200 mm. Next, as shown in FIG. 18, if necessary, a hole having a diameter larger than the diameter of the formed cylindrical hole is formed from the foundation concrete surface to a predetermined depth. This may be performed before the formation of the cylindrical hole. Formation of a hole having a diameter larger than the diameter of the cylindrical hole can be performed when a place for the following work needs to be secured.

Next, as shown in FIG. 19, the upper part of the anchor bolt is cut and removed at a predetermined position from the bottom surface of the cylindrical hole. The length to be cut and removed corresponds to the fitting length of the female screw portion and the bolt for fastening and fixing the base plate of the structure to the female screw portion of the connector. For example, when the anchor bolt diameter is D24, the fitting length can be 40 mm, for D22, 35 mm, for D20, 30 mm, and for D16, 25 mm (FIG. 24). reference).
Next, as shown in FIG. 20, a hollow cylindrical connector having a predetermined length having a female threaded portion at one end is formed in a cylindrical hole so that the female threaded portion is covered upward and the existing anchor bolt is exposed. insert. And as shown in FIG. 21, the said connector is fixed to the said foundation concrete by filling resin in a cylindrical hole and making it harden | cure. In addition, after the resin is filled in the cylindrical hole, the resin is placed so that the hollow cylindrical coupler having a predetermined length on the one end side is covered with the existing anchor bolt with the female screw portion facing upward. The connecting tool may be fixed to the foundation concrete by inserting into a filled cylindrical hole and curing the resin. The clearance between the outer surface of the connector and the inner surface of the cylindrical hole is preferably 5 mm to 30 mm. For example, the gap is filled with, for example, epoxy resin and cured over the predetermined fixing length of the above-described connecting device, so that the fixing device is firmly fixed with a strength capable of withstanding an expected earthquake based on the connecting device. Can be made.

Next, as shown in FIG. 22, mortar is filled up to the surface into a hole having a diameter larger than the diameter of the cylindrical hole formed from the surface of the basic concrete to a predetermined depth to protect the cured resin. The mortar is preferably non-shrinkable. When an epoxy resin is used as the resin, the epoxy resin is an organic substance and may be deteriorated by ultraviolet rays. However, the filling of the non-shrink mortar can prevent the ultraviolet ray deterioration and suppress the influence on water erosion.
Finally, as shown in FIG. 23, the repair method of the present invention is completed by fastening and fixing the base plate of the structure to the female thread portion of the connector fixed to the foundation concrete with bolts. However, the base plate of the structure is not shown in FIG.
By fixing the base plate of the structure with bolts, if the bolts are corroded, only the bolts need to be replaced, so maintenance is more advantageous than nut connection.

  FIG. 24 shows a specific example of a connecting tool for an existing anchor bolt, which is D24, and a bolt to be fitted to this, which are used in the construction method of the present invention. By providing the groove on the outer surface of the connector, it is possible to increase the fixing force of the epoxy resin that is filled and cured in the gap with the inner surface of the basic cylindrical hole. The material of the connector and the bolt is not limited, but is preferably stainless steel having corrosion resistance.

  The repair method according to the present invention can be constructed with a simple machine, and although a special work type is required, the number of construction can be increased by increasing the number of personnel. In addition, the construction range is small, and if safety glasses and masks are attached, work safety is excellent, and because only materials with excellent weather resistance are used, durability is excellent and economic efficiency is also excellent. . Furthermore, since the repair method of the present invention does not depend on the existing anchor bolts, it can be constructed regardless of the corrosion state of the existing anchor bolts. The design philosophy is post-installation anchors, which can withstand large-scale earthquakes expected in the future. Most importantly, in the repairing method of the present invention, a uniform pulling stress proportional to the fixing length of the connecting tool is guaranteed at all repair points. This cannot be achieved by the existing method described above or the method using the special recycled anchor bolt described in Patent Document 1. In this respect, the repair method of the present invention is superior to the repair method of the prior art.

  The structure foundation repair method of the present invention can be applied regardless of the corrosion state of the existing anchor bolts, etc., and a uniform pull-out stress proportional to the fixing length of the connector is guaranteed at all repair points. Therefore, the repaired structure can withstand a large-scale earthquake assumed in the future. Therefore, the structure foundation repair method of the present invention can be suitably used for repairing structures such as signs and lighting columns, for example, steel high fences on highways, anchors for securing guard fences, and the like.

Claims (8)

A structure base repair method in which a base plate of a structure is fixed to a surface exposed male thread portion of an existing anchor bolt embedded in the foundation concrete with a nut, and includes the following steps:
(1) removing the concrete around the existing anchor bolt to a predetermined depth from the surface to form a cylindrical hole around the existing anchor bolt;
(2) A step of cutting and removing the upper part of the anchor bolt at a predetermined position from the bottom surface of the cylindrical hole;
(3) internal thread portion possess at one end a, and a predetermined length of the hollow cylindrical connection unit having a hollow cylindrical portion of larger inner diameter than the outer diameter of the existing anchor bolts on the other end, and the internal thread portion upward And inserting into the cylindrical hole so as to cover the exposed existing anchor bolt;
(4) Filling the cylindrical hole with resin, and curing the connector over a predetermined length in at least a gap between the outer surface of the connector and the inner surface of the cylindrical hole. Fixing the tool to the foundation concrete; and (5) fixing the base plate of the structure to the female thread portion of the connector fixed to the foundation concrete with a bolt;
Structural foundation repair methods including   The repair method according to claim 1, further comprising a step of cutting and removing a surface exposed male screw portion of the existing anchor bolt prior to the step (1). Instead of the steps (3) and (4), the following steps:
(3 ') a step of filling the resin into the cylindrical bore; and (4') internal thread portion possess at one end a, and the other end of the hollow cylindrical portion of larger inner diameter than the outer diameter of the existing anchor bolts the predetermined length of the hollow cylindrical connection unit having a, and the internal thread portion upward, so as to cover covering the existing anchor bolts, the holes in the resin-like cylinder filled, inserted, the resin, at least the Curing the coupling tool over a substantially predetermined length in a gap between the outer surface of the coupling tool and the inner surface of the cylindrical hole to fix the coupling tool to the foundation concrete;
The repair method according to claim 1 or 2, comprising   The repair method according to any one of claims 1 to 3, wherein a depth of the cylindrical hole is 150 mm to 400 mm.   The repair method of any one of Claims 1-4 whose clearance gap between the outer surface of the said coupling tool and the inner surface of the said cylindrical hole is 5-30 mm.   The repair method according to any one of claims 1 to 5, wherein the resin is an epoxy resin.   In the step (1), before or after forming a cylindrical hole having a predetermined length around the existing anchor bolt, a hole having a diameter larger than the diameter of the hole on the cylinder is formed from the surface of the foundation concrete to a predetermined depth. The repair method according to any one of claims 1 to 6, further comprising forming.   The step of protecting the cured resin by filling the surface with a mortar into a hole having a diameter larger than the diameter of the cylindrical hole formed from the surface of the basic concrete to a predetermined depth. The repair method according to claim 7, further included before.

Images