JP7507634B2 - sheath - Google Patents

Description

This invention relates to a sheath for inserting steel material that applies prestress to concrete members.

Decks used in bridges, highway viaducts, etc. are formed by connecting concrete members (e.g. precast concrete segments) of a certain rectangular parallelepiped size (e.g. a few meters in length and width, and a thickness of several tens of centimeters to one meter). Concrete members are generally strong in compression but weak in tension, so steel (PC steel) is inserted into the segments and tensioned to apply a compressive force (prestress) to the segments (decks) in advance to ensure their strength.

The steel is placed inside a hollow cylindrical sheath that is embedded in the segment beforehand. After compressive force is applied by the steel, the sheath is filled with grout to prevent corrosion of the steel.

For example, the sheaths described in the following Patent Documents 1 and 2 have been proposed.

The sheath according to Patent Document 1 has an exhaust port 30 formed in the sheath body 21, which is filled with grout, for discharging the internal air when filling with grout 6, and an exhaust pipe 31 for connecting an exhaust hose 7 is connected to this exhaust port 30. This exhaust pipe 31 protrudes from the pipe wall of the sheath body 21 in a direction perpendicular to the pipe axis direction (see paragraph 0016, Figure 1, etc. of Patent Document 1).

In addition, the sheath according to Patent Document 2 has a hollow hole 37 drilled in the peripheral wall of the connection sheath 33, and a pipe erection section 39 is formed. The end face 26 of the connection pipe 21 constituting the grout injection pipe 20 abuts against the pipe erection section 39 via a packing 23, and a packing 24 is inserted into the back surface of the pipe erection section 39 from the inside of the connection sheath 33, and the fixed pipe 22 is inserted from above toward the countersunk hole 27 of the connection pipe 21. Furthermore, the protrusion 32 of the fixed pipe 22 engages with the recessed rib 28 of the connection pipe 21, thereby sandwiching the connection sheath 33 between the edge section 30. In this way, instead of engaging the protrusion 32 with the recessed rib 28, the female thread 46 formed on the grout injection pipe 40 and the male thread 50 formed on the pipe erection section 39 can be screwed together (see paragraphs 0031 to 0033, 0043 to 0046, Figures 2 and 4, etc., of Patent Document 2).

Japanese Patent No. 3933986 JP 2002-129705 A

In the sheath disclosed in Patent Document 1, the exhaust pipe 33 is already connected to the sheath body 21, so there is little freedom in the connection position of the hose 7 to the sheath body 21. This may cause problems in handling the hose 7 at the site.

The sheath according to Patent Document 2 allows the position of the hollow hole 37 in the connection sheath 33 to be changed, so it has a higher degree of freedom than the sheath according to Patent Document 1. However, packings 23, 24 must be interposed between the connection sheath 33 and the fixed tube 22 and between the connection sheath 33 and the connection tube 21, respectively, which increases the number of parts and reduces workability.

Therefore, the objective of this invention is to provide a sheath that allows high positional freedom when injecting grout, has a small number of parts, and is easy to work with.

In order to solve the above problems, this invention provides a sheath having a hollow cylindrical sheath body with a through hole formed on its circumferential surface penetrating from the inner surface to the outer surface, and a tubular member that is inserted into the through hole and has one end that fits into the inner edge of the through hole, or a sheath having a hollow cylindrical sheath body with a through hole formed on its circumferential surface penetrating from the inner surface to the outer surface, and a tubular member that is inserted into the through hole, and one end of the tubular member has an expanded portion that expands radially outward and fits into the inner edge of the through hole.

In this way, by changing the position of the through hole formed in the sheath body, a high degree of positional freedom can be ensured when injecting a filler such as grout. In addition, since it is only necessary to fit the tubular member into the through hole formed in the sheath body, workability is very good. Moreover, since the inner edge of the through hole fits into one end of the tubular member, a high level of watertightness can be ensured.

In a configuration having this expanded diameter portion, it is preferable to further have a tubular expanding member that is inserted into the inside of the one end of the tubular member to expand the one end radially outward to form the expanded diameter portion.

In this way, it is possible to use a general tubular member (such as a commercially available hose) that has a constant outer diameter over its entire length, thereby reducing the procurement costs of this tubular member.

In a configuration using this expanding member, it is preferable that a tapered surface that is inclined with respect to the axial direction is formed on the outer peripheral surface of the expanding member, and that the expanding member is inserted into the one end from the small diameter side of the tapered surface.

This allows the expansion member to be smoothly inserted into one end of the tubular member, ensuring high workability.

In each of the above configurations, it is preferable that at least one of the sheath body or the tubular member is made of a flexible material, and that the one end of the tubular member can be pulled out of the through hole by applying a pulling force to the other end of the tubular member opposite to the one end, thereby elastically deforming at least one of the sheath body or the tubular member.

This ensures that no unwanted material remains inside the segment (sheath), further improving the quality of the segment.

In each of the above configurations, it is preferable that the sheath body has connection ends at both axial ends to which a hollow cylindrical tube can be connected.

This makes it easy to extend the tube through which the steel material passes into the sheath body.

In this invention, the sheath is constructed by fitting one end of a tubular member onto the inner edge of a through hole formed in the sheath body, allowing for high positional freedom when injecting grout, and with a small number of parts, it is easy to work with.

FIG. 1 is a partially cutaway front view showing a first embodiment of a sheath according to the present invention. FIG. 1 is a perspective view showing an example of a diameter expanding member; FIG. 11 is a cross-sectional view showing a state in which a diameter expanding member is inserted into a tubular member. FIG. 4 is a cross-sectional view showing a state in which the tubular member shown in FIG. 3 is pulled toward the other end. FIG. 5 is a cross-sectional view showing a state in which the tubular member shown in FIG. 4 is pulled further strongly toward the other end. A side view showing the steel member inserted into the sheath embedded in the concrete segment. FIG. 1 is a partially cutaway front view showing a second embodiment of a sheath according to the present invention.

A first embodiment of the sheath 1 according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the main components of the sheath 1 are a sheath body 10 and a tubular member 20. The sheath 1 is embedded in a precast concrete segment 40 (see FIG. 6), and is a member for inserting steel material 41 (PC steel material) that applies prestress to the deck of a bridge or highway viaduct formed by connecting the segments 40. The sheath 1 according to the present invention can be applied not only to precast concrete segments 40, but also to concrete segments that are cast on-site.

The sheath body 10 is a hollow cylindrical member with through holes 11 formed on its circumferential surface, penetrating from the inner surface to the outer surface. The sheath body 10 has connection ends 12, 13 (receptacles for the tube 42) at both axial ends to which the hollow cylindrical tube 42 can be connected. By forming the connection ends 12, 13 in this manner, the sheath body 10 functions as a core-shaped joint (connecting tube) that connects the tubes 42 together.

The through holes 11 are basically formed by drilling in a factory, but to further increase the freedom of selection of the installation position of the tubular member 20 on-site, a drilling tool may be brought to the site, and the through holes 11 may be formed on-site according to the work conditions, and the sheath 1 may be assembled.

In this embodiment, polyethylene is used as the material for the sheath body 10, but this material is not particularly limited, and other resin materials or metal materials can also be used.

The tubular member 20 is a tubular member that extends from one end 21 that fits into the through hole 11 to the other end 22 opposite the one end 21. In this embodiment, a commercially available flexible nylon hose is used as the tubular member 20, but the material can be changed as appropriate. The tubular member 20 is long enough that the other end 22 is exposed on the surface of the segment 40 when the one end 21 is fitted into the through hole 11 formed in the sheath body 10 (see FIG. 6).

A tubular diameter expanding member 30 shown in FIG. 2 is inserted into the tube at one end 21 of the tubular member 20. This diameter expanding member 30 is a member with a tapered surface 31 formed on its outer circumferential surface that is inclined with respect to its axial direction, and its outer diameter gradually expands from the other end side toward the one end side in the axial direction. In this embodiment, polyethylene is used as the material for the diameter expanding member 30, but this material is not particularly limited, and other resin materials such as polypropylene or metal materials such as brass can also be used.

As shown in Figure 3, when the expanding member 30 is inserted into one end 21 of the tubular member 20 from the small diameter side of its tapered surface 31 (see the outline arrow in Figure 3), the outer diameter of the one end 21 is expanded radially outward (see arrow e in Figure 3), forming the expanded diameter section 23. By forming the expanded diameter section 23 in this way, the outer periphery of the tubular member 20 is tightly and firmly attached to the inner edge of the through hole 11 formed in the sheath body 10, ensuring high watertightness.

When the diameter expanding member 30 is inserted into one end 21 of the tubular member 20 and the tubular member 20 is pulled slightly toward the other end as shown in FIG. 4 (see the outlined arrow in FIG. 4), the diameter expanding member 30 is slightly pulled toward the through hole 11 formed in the sheath body 10 together with the tubular member 20. At this time, the diameter expanding member 30 acts as a wedge, and the outer periphery of the tubular member 20 is tightly fitted even more firmly against the inner edge of the through hole 11, completely eliminating any gap between the inner edge of the through hole 11 and the tubular member 20, and the pass criteria for the internal water pressure test, which is an indicator of the watertightness of the sheath 1, can be fully met.

In this embodiment, the sheath body 10, the tubular member 20, and the diameter expansion member 30 are all made of a resin material, and by pulling the tubular member 20 toward the other end 22, these members 10, 20, and 30 are elastically deformed little by little. Then, as shown in FIG. 5, by further increasing the pulling force toward the other end 22 (see the white arrow in FIG. 5), the one end 21 of the tubular member 20 can be pulled out of the sheath body 10. In this way, by pulling out the tubular member 20, the quality of the segment 40 (see FIG. 6) can be further improved.

In order to make this removal possible, at least one of the materials of the sheath body 10, the tubular member 20, or the diameter expansion member 30 must be made of a flexible material that can be elastically deformed by a strong removal force. In addition, if a lubricant such as grease or a mold release agent is applied to the surface of the tubular member 20 in advance, the tubular member 20 can be removed smoothly.

When forming a structure such as a deck, as shown in FIG. 6, the separated sheaths 1 (hereinafter referred to as the first sheath 1a and the second sheath 1b) are connected to each other by a tube 42, and grout is filled in through the tubular member 20 of the first sheath 1a, while simultaneously evacuating the air in the sheath 1 and the tube 42 through the tubular member 20 of the second sheath 1b. This allows the grout filling operation to be carried out smoothly. When grout is discharged from the tubular member 20 of the second sheath 1b instead of air, it can be determined that almost all of the air in the sheath 1 and the tube 42 has been discharged.

When filling the sheath 1 with grout, the grout starts to accumulate from the bottom, and air remains on the top of the sheath 1. Therefore, it is preferable to insert the tubular member 20 of the first sheath 1a into the side of the sheath body 10, and the tubular member 20 of the second sheath 1b into the top of the sheath body 10. In this way, the grout can be smoothly filled into the sheath body 10, while the air can be removed from within the sheath body 10.

In particular, as shown in FIG. 6, when the sheath 1 and the pipe body 42 are embedded in the segment 40 at an angle from the horizontal direction, the grout filling operation can be performed more smoothly by filling the lower sheath 1 (first sheath 1a) while evacuating the air from the upper sheath 1 (second sheath 1b).

A second embodiment of the sheath 1 according to the present invention is shown in Figure 7. The configuration according to this second embodiment is the same as the configuration according to the first embodiment in that one end 21 of a tubular member 20 is inserted into a through hole 11 formed in a sheath body 10, but differs in that an expanded diameter portion 23 is formed at one end of the tubular member 20 from the beginning.

This expanded diameter portion 23 has an outer diameter slightly larger than the inner diameter of the through hole 11 formed in the sheath body 10. In this way, when the other end 22 of the tubular member 20 is passed through the through hole 11 from the inside of the sheath body 10 and the tubular member 20 is pulled outward, the inner edge of the through hole 11 and the expanded diameter portion 23 engage just before the tubular member 20 is completely removed from the through hole 11, providing a retaining effect for the tubular member 20 and a watertight effect between the inner edge of the through hole 11 and the expanded diameter portion 23.

When the pulling force toward the other end 22 of the tubular member 20 is further increased, the expanded diameter portion 23 passes through the through hole 11, and the tubular member 20 is pulled out from the sheath body 10. According to the configuration of the second embodiment, it is not necessary to fit the expanded diameter member 30 into one end 21 of the tubular member 20, so that the operation time can be shortened. In addition, by pulling out the tubular member 20, the quality of the segment 40 (see FIG. 6) can be further improved. Note that, in order to enable this pulling out, at least one of the sheath body 10 or the tubular member 20 needs to be made of a flexible material that can be elastically deformed by a strong pulling out force.

The sheath 1 described above is an example in every respect, and the shape, materials, etc. of the components of this sheath 1 can be modified as appropriate as long as it achieves the object of the present invention, which is to provide a sheath 1 that has a high degree of positional freedom when injecting grout, a small number of parts, and good workability.

REFERENCE SIGNS LIST 1 sheath 1a first sheath 1b second sheath 10 sheath body 11 through hole 12, 13 connection end 20 tubular member 21 one end 22 other end 23 enlarged diameter portion 30 enlarged diameter member 31 tapered surface 40 segment 41 steel material 42 tube body

Claims (3)

a hollow cylindrical sheath body (10) having a through hole (11) formed on a peripheral surface thereof, the through hole (11) penetrating from an inner surface to an outer surface;
A tubular member (20) to be inserted into the through hole (11);
one end of the tubular member (20) has an expanded diameter portion (23) that expands radially outward and fits into the inner edge of the through hole (11);
The present invention further includes a tubular expanding member (30) that is inserted into the inside of the one end (21) of the tubular member (20) to expand the one end (21) radially outward to form the expanded portion (23),
The sheath body (10) has connection ends (12, 13) at both axial ends to which a hollow cylindrical tube body (42) can be connected, a steel material (41) that is embedded in concrete to apply prestress to the concrete is inserted through the sheath, and grout is filled from the tubular member (20) or air is evacuated from the sheath body (10) and the tube body (42) from the tubular member (20) during the filling . 2. The sheath according to claim 1, wherein a tapered surface (31) inclined with respect to an axial direction is formed on an outer peripheral surface of the diameter expansion member (30), and the diameter expansion member (30) is inserted into the one end (21) from the small diameter side of the tapered surface (31). 3. The sheath according to claim 1 or 2, wherein at least one of the sheath body (10) and the tubular member (20) is made of a flexible material, and by applying a pulling force to the other end side of the tubular member (20) opposite to the one end, at least one of the sheath body (10) and the tubular member (20) is elastically deformed, making it possible to pull out the one end from the through hole (11).

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