JP7812309B2 - Temporary structure and anchoring method for anchoring tendons - Google Patents

Description

The present invention relates to a temporary structure for securing tendons inserted into through-holes in a concrete structure, and a method for securing tendons using the temporary structure.

After tensioning, the tendons are anchored into the concrete frame, thereby introducing prestress into the frame. Conventionally, it has been known to anchor tendons into the concrete frame using metal wedges. However, in areas where salt damage is expected, it is desirable to avoid using metal wedges. For example, Patent Document 1 describes a method in which, instead of using metal wedges, a tapered sheath that expands in diameter near the concrete surface is embedded into the concrete frame, and the tapered section is filled with a filler to tension the tendons.

However, when prestressing an existing concrete frame during seismic reinforcement work, etc., it is difficult to create tapered through-holes in the concrete frame. One example of an anchoring method used in such cases involves inserting hoses into both ends of a through-hole of a certain diameter through which the tendon has been inserted after tensioning the tendon, then filling both ends with thickened mortar as a water-stopping material. After the thickened mortar has hardened, filler is injected through one hose and discharged through the other hose, and the tendon is fixed in place as the filler hardens.

Japanese Patent Application Publication No. 6-330631

However, with the above-mentioned method of applying excess thickened mortar, the position and orientation of the hose fixed to the thickened mortar were not always correct, and skilled workers were required to ensure accurate construction. Furthermore, filler could not be injected until the thickened mortar had developed its strength, and excess thickened mortar could sometimes result in longer construction times. Furthermore, if there was a problem with the installation of the thickened mortar, the filler would leak, adversely affecting the anchoring performance of the tensioning material. Therefore, in order to detect filler leakage early and prevent adverse effects, it was desirable to monitor the filler until it hardened.

In light of the above background, the present invention aims to provide a temporary structure and anchoring method for anchoring tendons that allows preparation for filling with filler material to be completed in a short period of time and ensures high reliability in filling with filler material.

In order to solve the above-mentioned problems, one aspect of the present invention is a temporary structure (1) for fixing a tendon (4) inserted into a through hole (3) provided in a concrete frame (2), the temporary structure comprising a support wall (10) having an outer surface to be brought into contact with the concrete frame perpendicular to the axial direction and an inner surface facing the opposite side to the outer surface, legs (11) extending from the support wall in the axial direction, and a retaining wall (12) supported on the tip of the legs to support the tendon, the support wall having an opening (10a) that is at least partially aligned with the through hole when viewed from the axial direction, and a temporary frame having an injection and discharge port disposed within the opening of the temporary frame and penetrating in the axial direction, the temporary frame having an injection and discharge port that at least partially surrounds the tendon. the first gasket (14) disposed in the opening; a plate member (15) abutting against the first gasket and having a hole (15a) through which the tendon is tightly inserted; a ring-shaped second gasket (16) through which the tendon is inserted and abutting against the inner surface of the support wall; a first closing plate (17) fixed to the inner surface of the support wall via the second gasket; and a second closing plate (18) fixed to the inner surface of the support wall via the second gasket and having a hose attachment port (18c) that opens to align with the injection and discharge port (14a) between both circumferential ends of the first gasket when viewed from the axial direction, and which cooperates with the first closing plate to have a ring shape when viewed from the axial direction and engage the first gasket and the plate member.

In this embodiment, the structure for waterproofing both ends of the through hole is strong enough to hold back the filler when assembled. This shortens the construction period compared to using thick mortar as a waterproofing material and waiting for it to develop strength. Furthermore, there is little variation in waterproofing performance due to worker skill, resulting in a high degree of reliability in waterproofing.

In the above aspect, the first gasket (14) may have a C-shape with the injection and discharge port (14a) formed between both circumferential ends.

According to this aspect, even if the first gasket is constructed as a single component, it is possible to place the first gasket in the specified position after the tendon is secured to the temporary framing.

One aspect of the present invention is a method for fixing the tendons (4) to the concrete frame (2) using the temporary structure (1) of the above aspect, comprising the steps of: inserting the tendons into the holes in the plate member (15) so that they are in close contact with each other; installing the temporary frame on the concrete frame so that the central axis of the opening (10a) in the support wall (10) is aligned with the central axis of the through-hole (3) in the concrete frame; tensioning the tendons to engage with the temporary frame (5); placing the first gasket (14) in the opening in the support wall; and sliding the plate member. abutting the second gasket (16) against the inner surface of the support wall; fixing the first and second blocking plates (17) to the support wall via the second gasket so that the hose attachment port (18c) of the second blocking plate (18) is aligned with the injection and discharge port (14a) of the first gasket when viewed from the axial direction; attaching a hose (9) to the hose attachment port and filling the through hole with a filler material (20) via the hose; and removing the temporary structure after the filler material has hardened.

In this embodiment, the structure for waterproofing both ends of the through hole is strong enough to hold back the filler when assembled. This shortens the construction period compared to using thick mortar as a waterproofing material and waiting for it to develop strength. Furthermore, there is little variation in waterproofing performance due to worker skill, resulting in a high degree of reliability in waterproofing.

In the above aspect, the tendon (4) may include fiber-reinforced plastic, and the plate member (15) may be flexible.

In this embodiment, the tendons contain fiber-reinforced plastic, which does not rust, making them suitable for use in areas where salt damage is expected, and the plate members are flexible, so the tendons are not damaged when the plate members are installed or slid.

In the above aspect, the concrete body (2) may be an existing concrete structure, and the method may further include a step of providing the through hole (3) in the concrete body.

This method makes it easier to introduce prestress into existing concrete structures in areas where salt damage is expected.

The above aspects make it possible to provide a temporary structure and anchoring method for anchoring tendons that allows preparation for filling with filler material to be completed in a short period of time and ensures high reliability in filling with filler material.

FIG. 1 is a longitudinal cross-sectional view showing a temporary structure according to an embodiment; FIG. 1 is a perspective view showing details and construction procedures of a temporary structure according to an embodiment. FIG. 1 is a perspective view showing details and construction procedures of a temporary structure according to an embodiment. FIG. 1 is a perspective view showing details and construction procedures of a temporary structure according to an embodiment. FIG. 1 is a perspective view showing details and construction procedures of a temporary structure according to an embodiment. FIG. 1 is a perspective view showing details and construction procedures of a temporary structure according to an embodiment.

The following describes the temporary structure 1 according to the embodiment and the anchoring method using the temporary structure 1, with reference to the drawings.

Figure 1 is a vertical cross-sectional view showing a temporary structure 1 for anchoring a tendon 4 inserted into a through-hole 3 in a concrete body 2. The through-hole 3 is drilled into the concrete body 2, which is an existing concrete structure, and extends linearly with a constant diameter. This embodiment can also be applied to a newly constructed concrete body 2. In this case, the through-hole 3 is formed by a sheath (not shown) installed before the concrete is poured, and may be curved or have a diameter that varies in part or all of its direction of extension. The tendon 4 contains fiber-reinforced plastic (FRP) such as aramid fiber, carbon fiber, or glass fiber.

As shown in Figure 1, the temporary structure 1 comprises a temporary base 5 abutting against the concrete frame 2, a temporary attachment 6 to which the end of the tension member 4 is fixed, a nut 7 that supports the temporary attachment 6 on the temporary base 5, a watertight section 8 that seals off the end of the through-hole 3, and a hose 9 connected to the watertight section 8.

The temporary support 5 includes a support wall 10 that abuts against the concrete frame 2 perpendicular to the axial direction, which is the extension direction of the tendons 4; a pair of legs 11 that extend from the support wall 10 on the opposite side of the concrete frame 2 in the axial direction; and a retaining wall 12 that is supported at the tips of the pair of legs 11 and supports the temporary mounting body 6.

When viewed from the axial direction, the support wall 10 is composed of a steel flat plate in the shape of a ring with an opening 10a penetrating through the center. It has an outer surface that abuts against the concrete body 2 for support, and an inner surface facing the anchoring wall 12 on the opposite side. A tendon 4 is inserted into the opening 10a. When viewed from the axial direction, the temporary mounting base 5 is positioned so that the central axis of the opening 10a roughly coincides with the central axis of the through-hole 3, and it is preferable that the outline of the opening 10a be located outside the outline of the through-hole 3. The shape of the opening 10a when viewed from the axial direction may be other than circular, for example, rectangular.

The legs 11 are made of plate- or rod-shaped steel material extending in the axial direction. The distance between a pair of legs 11 is preferably longer than the diameter of the opening 10a to facilitate installation of the watertight section 8. There may be three or more legs 11.

When viewed from the axial direction, the retaining wall 12 is composed of a flat steel plate that is annular in shape and has an opening 12a penetrating through the center. The temporary mounting body 6 is inserted into the opening 12a. The temporary stand 5 may be a casting in which the support wall 10, pair of legs 11, and retaining wall 12 are integrally formed, or the pair of legs 11 may be joined to the support wall 10 and retaining wall 12 by welding or the like.

The temporary attachment 6 is a cylindrical steel member extending in the axial direction. After the tendon 4 is inserted into the temporary attachment 6, a filler 13 such as non-shrink mortar is filled inside, temporarily attaching the tendon 4 to the temporary attachment 6. The outer surface of the temporary attachment 6 is provided with a thread onto which a nut 7 is threaded.

The nut 7 is threadedly engaged with the temporary attachment 6 and is then engaged with the retaining wall 12 from the side opposite the concrete body 2. As a result, the temporary attachment 6 is supported by the retaining wall 12 via the nut 7.

Figures 2 to 6 show the details and construction procedure of the watertight section 8. As shown in Figures 2 to 6, the watertight section 8 includes a first gasket 14 that is C-shaped when viewed from the axial direction and is placed within the opening 10a of the support wall 10; a plate member 15 that is positioned to block the center of the first gasket 14 when viewed from the axial direction; a second gasket 16 that is annular when viewed from the axial direction and abuts against the support wall 10; and a first closing plate 17 and a second closing plate 18 that are semi-annular when combined with each other to form an annular shape when viewed from the axial direction and that cooperate with the support wall 10 to sandwich the second gasket 16.

As shown in Figures 3 and 4, the first gasket 14 is a member made of a material such as rubber with water-stopping properties. When viewed from the axial direction, the first gasket 14 has an injection and discharge port 14a formed by the gap between the circumferential ends of the C-shape. The first gasket 14 is positioned within the opening 10a of the support wall 10 so that its outer peripheral edge abuts the inner peripheral surface that defines the opening 10a of the support wall 10 and its inner peripheral edge surrounds the tendon 4. Instead of a C-shape, the first gasket 14 may be a member having a hole that forms the injection and discharge port 14a, and may have a ring shape including a radially cut portion, or the tendon 4 may be surrounded by two or more members.

The plate member 15 is a flat, circular member when viewed axially and has a hole 15a through which the tendon 4 is inserted in a tight fit. To ensure tight contact with the tendon 4 and to prevent damage to the tendon 4 when slid, the plate member 15 is preferably flexible, and may contain, for example, polytetrafluoroethylene. The plate member 15 abuts against the inner periphery of the C-shaped first gasket 14. Therefore, the circular plate member 15 when viewed axially generally matches the diameter of the inner periphery of the first gasket 14. The plate member 15 may have a shape other than circular when viewed axially and have an outline that generally matches the inner periphery of the first gasket 14. The plate member 15 may also have an outline that is larger than the inner periphery of the first gasket 14 but smaller than the outer periphery of the first gasket 14 when viewed axially, and abut against the first gasket 14 so as to cover the inner periphery of the first gasket 14.

As shown in Figure 5, the second gasket 16 is a member made of a material such as rubber with water-stopping properties. When viewed from the axial direction, the second gasket 16 has a ring shape, preferably a circular ring shape. The second gasket 16 preferably has a radially cut portion so that it can be attached to surround the tendon 4 after the tendon 4 is fastened to the temporary framing 5. When viewed from the axial direction, the inner peripheral edge of the second gasket 16 approximately coincides with the inner peripheral surface that defines the opening 10a of the support wall 10.

As shown in Figures 5 and 6, the first and second closing plates 17 and 18 combined with each other have a ring shape, preferably a circular ring shape, surrounding the tendon 4 when viewed from the axial direction. The first and second closing plates 17 and 18 each include a main plate portion 17a, 18a that is semi-ring shaped when viewed from the axial direction, and flange portions 17b, 18b erected at both circumferential ends of the main plate portions 17a, 18a. The first and second closing plates 17 and 18 have higher rigidity than the first gasket 14, the plate member 15, and the second gasket 16, and are preferably made of steel or resin. The support wall 10 of the temporary gantry 5 is provided with a screw hole 10b (see FIG. 4) extending axially from its inner surface near the opening 10a, the second gasket 16 is provided with a through hole 16a that penetrates in the axial direction and aligns with the screw hole 10b, and the first closing plate 17 and the second closing plate 18 are provided with through holes (not shown) that penetrate in the axial direction and align with the through hole 16a. The first closing plate 17 and the second closing plate 18 are fixed to the inner surface of the support wall 10 via the second gasket 16 by inserting bolts 19 through the through holes of the first closing plate 17 and the second closing plate 18 and the through hole 16a of the second gasket 16 and fastening them to the screw hole 10b, thereby locking the first gasket 14 and the plate member 15. Since the tendon 4 rotates around the central axis, it is preferable to provide more threaded holes 10b than bolts 19 so that the circumferential attachment angle of the first closing plate 17 and the second closing plate 18 can be adjusted. In the illustrated example, eight threaded holes 10b are provided for four bolts 19, and are arranged at equal intervals in the circumferential direction. It is preferable that the number of through holes in the second closing plate 18 and the number of through holes 16a in the second gasket 16 each match the number of bolts 19 and be arranged at equal intervals in the circumferential direction. The flange portions 17b of the first closing plate 17 and the flange portions 18b of the second closing plate 18 are fixed to each other by inserting fasteners 21 such as bolts and nuts into holes provided in the flange portions 17b, 18b and fastening them while they are in contact with each other. The annular outer periphery of the combined first and second closing plates 17 and 18 preferably coincides with or is slightly radially inward of the annular outer periphery of the second gasket 16 when viewed axially. The second closing plate 18 is provided with a hose attachment port 18c that opens to align with the injection and discharge port 14a of the first gasket 14 when viewed axially. The temporary structure 1 is provided at both ends of the through-hole 3 in the concrete skeleton 2 (see FIG. 1). At one end, the injection and discharge port 14a and hose attachment port 18c are preferably provided below the tendon 4 to inject a filler 20 (see FIG. 1), such as non-shrink mortar. At the other end, the injection and discharge port 14a and hose attachment port 18c are preferably provided above the tendon 4 to discharge the filler 20.

A groove 10c is provided on the outer surface of the support wall 10 of the temporary platform 5, extending radially upward from the opening 10a to the outer periphery of the support wall 10. The groove 10c and the surface of the concrete skeleton 2 define an exhaust port that communicates with the through-hole 3 in the concrete skeleton 2, and a wedge member 22 is inserted into the upper part of the exhaust port. The wedge member 22 is preferably made of wood or rubber.

With reference to Figures 1 to 6, the anchoring method for tendons 4 using a temporary structure 1 will be explained.

As shown in Figure 2, workers drill through-holes 3 in the concrete structure 2 and insert tendons 4 into the through-holes 3. From then on, similar work is carried out near both ends of the through-hole 3 until the filling work of the filler material 20 is performed.

Workers insert both ends of the tendon 4 into the holes 15a in the plate member 15 and temporarily attach the portion of the tendon 4 closer to the end than the plate member 15 with the temporary attachment 6. Then, workers install the temporary base 5 on the concrete structure 2 so that the tendon 4 is inserted through the opening 10a in the support wall 10, the temporary attachment 6 is inserted through the opening 12a in the retaining wall 12, and the plate member 15 is positioned axially between the support wall 10 and the temporary attachment 6.

Next, the worker places the first gasket 14 in the opening 10a of the support wall 10, as shown in Figure 3, and slides the plate member 15 so that it abuts against the first gasket 14, as shown in Figure 4.

Next, as shown in Figure 5, the worker abuts the second gasket 16 against the inner surface of the support wall 10 and attaches the first closing plate 17 to the support wall 10 with bolts 19 so that the second gasket 16 is sandwiched between them. Next, as shown in Figure 6, the worker attaches the second closing plate 18 to the support wall 10 with bolts 19 so that the second gasket 16 is sandwiched between them, and attaches the flange portion 18b of the second closing plate 18 to the flange portion 17b of the first closing plate 17 with fasteners 21.

Next, as shown in Figure 1, the worker attaches the hose 9 to the hose attachment port 18c and injects the filler material 20 from the hose 9 located at one end of the through-hole 3, continuing the injection until the filler material 20 is discharged from the hose 9 located at the other end. At this time, air present in the through-hole 3 is discharged through the groove 10c. Once sufficient air has been discharged, the wedge member 22 is inserted into the top of the groove 10c to close the exhaust port defined by the groove 10c and the surface of the concrete body 2, preventing the filler material 20 from flowing out of the groove 10c. After the injection is complete and a predetermined period has passed and the filler material 20 has hardened, the temporary structure 1 is removed and the tendon 4 is cut near the surface of the concrete body 2.

The effects of the anchoring method using temporary structure 1 are explained.

The water-stopping section 8 is designed so that it can be assembled to provide the strength to block the filler material 20, which shortens the construction period compared to using thick mortar as a water-stopping material and waiting for it to develop its strength.

Because the watertight portion 8 is formed by assembling components with a predetermined shape, there is little variation in watertight performance due to the skill of the worker, and the watertight portion 8 is highly reliable in stopping water.

By positioning the contour of the opening 10a outside the contour of the through-hole 3, the first gasket 14 can be placed within the opening 10a so that the outer edge of the first gasket 14 abuts the surface of the concrete body 2, making it easy to position the first gasket 14.

The first gasket 14 has a C-shape when viewed from the axial direction, so it can be attached to partially surround the tendon 4 using the injection and discharge port 14a, even after the tendon 4 has been secured to the temporary frame 5.

Because the first and second closing plates 17, 18 are separate components, they can cooperate to surround the tendon 4, and the flange portions 17b, 18b can abut against each other, allowing them to be tightly connected to each other.

Because the FRP tendons 4 can be fixed without using metal fasteners, the fixing method using the temporary structure 1 is suitable for use in areas where salt damage is expected.

The anchoring method using the temporary structure 1 can be applied to through holes 3 that extend linearly with a constant diameter, making it suitable for reinforcing existing concrete structures.

This concludes the description of specific embodiments, but the present invention is not limited to the above embodiments and modifications, and can be implemented in a wide variety of ways. Instead of FRP, PC steel materials such as PC steel rods, PC steel wires, or PC steel strands may be used as tendons. For example, when PC steel rods are used as tendons, a thread may be provided on the outer surface of the PC steel rod, and a nut threaded onto this thread may be engaged by the retaining wall of the temporary framing structure, rather than using a temporary setting attachment. The first and second gaskets may be a single, continuous, ring-shaped member. In this case, the tendon is inserted through the gasket and placed inside the temporary framing structure before being tensioned and secured to the temporary framing structure. The first and second closing plates do not need to have flanges.

DESCRIPTION OF SYMBOLS 1: Temporary structure 2: Concrete body 3: Through hole 4: Tendon 5: Temporary frame 9: Hose 10: Support wall 10a: Opening 11: Leg 12: Locking wall 14: First gasket 14a: Injection/discharge port 15: Plate member 15a: Hole 16: Second gasket 17: First closing plate 18: Second closing plate 18c: Hose attachment port 20: Filler

Claims (5)

A temporary structure for fixing a tendon inserted into a through-hole provided in a concrete skeleton,
a temporary cradle including: a support wall having an outer surface to be brought into contact with the concrete skeleton perpendicular to the axial direction and an inner surface facing the opposite side to the outer surface; legs extending from the support wall in the axial direction; and anchoring walls supported by the tips of the legs to support the tendons, wherein the support wall has an opening that is at least partially aligned with the through-hole when viewed from the axial direction;
a first gasket disposed within the opening of the temporary cradle, the first gasket having an injection and discharge port penetrating in the axial direction, the first gasket disposed within the opening so as to at least partially surround the tendon;
a plate member having a hole through which the tendon is to be inserted in close contact and abutting against the first gasket;
a second gasket having an annular shape through which the tendon is inserted and which abuts against the inner surface of the support wall;
a first closing plate fixed to the inner surface of the support wall via the second gasket;
A temporary structure comprising: a second blocking plate that is fixed to the inner surface of the support wall via the second gasket, has a hose attachment port that opens to align with the injection and discharge port of the first gasket when viewed from the axial direction, and cooperates with the first blocking plate to have a ring shape when viewed from the axial direction and engage the first gasket and the plate member. The temporary structure described in claim 1, wherein the first gasket has a C-shape with the injection and discharge ports formed between both circumferential ends. A method for fixing the tendon to the concrete skeleton using the temporary structure according to claim 1,
inserting the tendon into the hole of the plate member so as to be in close contact with the hole;
installing the temporary pedestal on the concrete skeleton so that a central axis of the opening of the support wall is aligned with a central axis of the through hole of the concrete skeleton;
a step of tensioning the tendons and fastening them to the temporary framing;
placing the first gasket within the opening in the support wall;
a step of sliding the plate member to bring it into contact with the first gasket disposed in the opening;
abutting the second gasket against the inner surface of the support wall;
fixing the first and second closing plates to the support wall via the second gasket so that the hose attachment port of the second closing plate is aligned with the injection and discharge port of the first gasket when viewed from the axial direction;
attaching a hose to the hose attachment port and filling the through hole with a filler material via the hose;
and removing the temporary structure after the filling material has hardened. the tendon includes fiber-reinforced plastic;
The method according to claim 3 , wherein the plate member is flexible. The concrete skeleton is an existing concrete structure,
The method according to claim 4 , further comprising the step of providing the through-hole in the concrete body.