Sheath connection structure and concrete structure construction method

Abstract

To provide a technology that enables the construction of a concrete structure extending in the height direction by easily connecting sheaths.SOLUTION: Provided is a connection structure via a joint 2 between sheaths 1, through which tendons of a prestressed concrete structure are inserted. The joint 2 is a funnel-shaped one having a parallel portion 21 and an expanded diameter portion 22. One sheath 1 to be connected is inserted into the interior of the joint 2 through the opening of the parallel portion 21 of the joint 2, and the other sheath 1 is inserted into the interior of the joint 2 through the opening of the expanded diameter portion 22 of the joint 2. Each sheath 1 and joint 2 are sealed at the parallel portion 21 of the joint 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to the connection of a sheath through which a tendon is inserted during construction of a concrete structure. [Background technology]

[0002] As shown in Figure 5, a PC cable-stayed bridge has a prestressed concrete (PC) main girder 53 suspended by cables 52 strung from a reinforced concrete main tower 51. This is a rational structure that combines concrete that is strong against compression forces with PC steel that is strong against tension forces, making it suitable for bridging long spans and aesthetically pleasing.

[0003] When constructing such a PC cable-stayed bridge, the main towers 51 are assembled in order from bottom to top using formwork divided in the height direction, and concrete is poured (see the dotted lines in Figure 5). Compressive stress is imparted to the concrete by applying tensile force to the PC steel members 54 that act as tension members extending from the bottom to the top of the main towers 51.

[0004] As shown in Fig. 6, the PC steel members 54 are inserted into sheaths 56 erected inside formwork 55 stacked in multiple stages. The sheaths 56 are usually connected via short, straight-tube joints 57, but it is difficult to insert such straight-tube joints 57 into the sheaths 56.

[0005] As a countermeasure to this problem, Patent Document 1 listed below describes a method of connecting a trumpet-shaped joint 62 to the end of a sheath 61, as shown in Figure 7. In Patent Document 1 listed below, the connection between the sheath 61 and the joint 62 is achieved by heating the end of the sheath 61, pushing a jig into the softened end of the sheath 61 to expand the diameter of the end of the sheath 61, and then removing the jig and inserting the base of the joint 62 into the expanded end of the sheath 61. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-92167 Summary of the Invention [Problem to be solved by the invention]

[0007] However, connecting the sheath 61 and the joint 62 using the procedure described in Patent Document 1 is extremely time-consuming, and when applied to connecting a sheath erected inside a concrete structure that extends vertically, such as the main tower of a PC cable-stayed bridge, the work becomes extremely difficult.

[0008] Therefore, an object of the present invention is to provide a technology that enables sheaths to be easily connected and concrete structures that extend vertically to be constructed. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides a connection structure via a joint between sheaths through which tendons of a prestressed concrete structure are inserted, comprising: The joint is funnel-shaped having a parallel portion and an enlarged portion, one sheath to be connected is inserted into the inside of the joint from an opening in the parallel portion of the joint, and the other sheath is inserted into the inside of the joint from an opening in the enlarged diameter portion of the joint, The sheaths and the joints are sealed at the parallel portions of the joints.

[0010] Furthermore, the installation direction of the sheath is vertical.

[0011] Furthermore, the sheath and the parallel portion of the joint are sealed with a cloth-like sealing material.

[0012] Furthermore, the sheath and the parallel portion of the joint are sealed with a water-swellable sealing material.

[0013] Furthermore, the sheath inserted from the parallel portion of the joint is extendable in the length direction.

[0014] In this case, the sheath inserted from the parallel part of the joint is made up of a straight tube having a spiral convex ridge on its outer surface and a straight tube having a spiral concave ridge on its inner surface that are screwed together, and expands and contracts in the longitudinal direction as the sheath is screwed in.

[0015] In the method for constructing a concrete structure, formwork is stacked in a plurality of stages, a sheath pipe body erected inside the formwork of each stage is connected, and concrete is poured inside the formwork. The sheath tubular body has an expanded diameter portion on the distal end side, a step of vertically erecting the sheath tubular body in a lower mold so that the enlarged diameter portion faces upward; a step of vertically placing the sheath tubular body, the base end of which has been wrapped with a cloth-like sealing material around its outer periphery, in an upper mold with the base end facing downward, and inserting the expanded diameter portion on the tip side of the sheath tubular body in the lower mold; A step of repeating the above steps a predetermined number of times and then pouring concrete into the formwork; The present invention aims to provide a method for constructing a concrete structure having the above features. [Effects of the Invention]

[0016] In this invention, when constructing a concrete structure that extends vertically, such as the main tower of a PC cable-stayed bridge, the tip of the sheath is inserted in advance through the opening in the parallel part of the funnel-shaped joint to form a sheath pipe body, and the sheaths that are erected inside the lower and upper formwork are connected.

[0017] At this time, the base end of the sheath of the upper sheath tubular body is guided by the enlarged diameter portion of the joint, enters the inside of the joint, and reaches the parallel portion of the joint of the lower sheath tubular body.

[0018] Furthermore, the spaces between the lower sheath, the upper sheath, and the parallel parts of the lower joints that connect them are sealed with sealing material, so the sheaths can be easily connected to each other, preventing concrete from seeping into the sheaths and joints when pouring concrete. [Brief explanation of the drawings]

[0019] [Figure 1] As an embodiment of the present invention, an elevation view showing the sheath connection process during construction of a concrete structure. [Figure 2] Enlarged elevation of the main part of the same [Figure 3] FIG. 10 is an elevation view showing the connection state of the sheath of the same [Figure 4] Schematic diagram showing the construction process of the above-mentioned concrete structure extending in the height direction [Figure 5] Schematic elevation showing a PC cable-stayed bridge [Figure 6] Schematic diagram showing the construction process of a conventional vertically extending concrete structure [Figure 7] Cross-sectional view showing the connection structure between the sheath and the joint described in Patent Document 1 DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Here, an example will be given of constructing a concrete structure extending in the height direction, such as a main tower 51 of a PC cable-stayed bridge shown in FIG.

[0021] <Summary> As shown in Figure 1, in this construction, a funnel-shaped joint 2 is attached to the tip of each sheath 1 to be connected, forming a sheath tube body 10 in advance, and then the sheaths 1 erected inside the lower formwork F and the upper formwork F are connected.

[0022] <Components of the sheath tube> (sheath) As shown in Figure 2, sheath 1 is composed of a long straight pipe 11 made of polyethylene and having a spiral ridge on its outer surface, a short straight pipe 12 made of polyethylene and having a larger diameter than straight pipe 11 and a spiral recess on its inner surface, and a short straight pipe 13 made of polyethylene and having the same diameter as straight pipe 11 and having a spiral ridge on its outer surface. Straight pipe 12 is screwed onto the outer periphery of the tip of straight pipe 11, and straight pipe 13 is screwed onto the inner periphery of straight pipe 12, so that it can expand and contract in the longitudinal direction as it is screwed in and out.

[0023] (joint) The joint 2 is made of vinyl chloride and has a straight parallel section 21 and a trumpet-shaped expanded diameter section 22 that gradually increases in diameter from the parallel section 21. The base end of the parallel section 21 and the large diameter end, which is the tip of the expanded diameter section 22, are open, and the openings at both ends are connected. The inner diameter of the parallel section 21 is larger than the outer diameter of the straight tubes 11, 13 of the sheath 1.

[0024] (sealing material) A sealing material 3 is wrapped around the inner periphery of the base end of the parallel portion 21 of the lower joint 2 and the outer periphery of the base end of the upper sheath 1 below the straight tube 11. The sealing material 3 is a cloth-like material that has water-swelling properties and expands when wet.

[0025] <Sheath tube manufacturing> When manufacturing the sheath tubular body 10, the straight pipe 13 at the tip of the sheath 1 is inserted into the opening of the parallel portion 21 of the joint 2 to join the sheath 1 and the joint 2. The straight pipe 13 is fastened midway along the length of the parallel portion 21 of the joint 2.

[0026] In this state, the gap between the outer periphery of the straight pipe 13 and the inner periphery of the parallel section 21 of the joint 2 is sealed by the sealing material 3 wrapped around the inner periphery of the base end of the parallel section 21 of the joint 2. In addition, the boundary between the outer periphery of the tip end of the straight pipe 12 and the outer periphery of the base end of the parallel section 21 of the joint 2 is sealed by wrapping vinyl tape 4 around it.

[0027] <Concrete structure construction> To construct a vertically extending concrete structure such as the main tower 51 of a PC cable-stayed bridge shown in Figure 5 using the sheath pipe body 10 manufactured in this manner, first, as shown in Figure 1, one of the sheath pipe bodies 10 to be connected is fixed vertically inside the lower formwork F with the expanded diameter portion 22 of the joint 2 facing upward.

[0028] At this time, the straight pipe 12 is rotated appropriately relative to the straight pipe 11 of the sheath 1 to adjust the length of the sheath 1 so that the height of the opening of the expanded diameter portion 22 of the joint 2 is aligned with the height of the upper end of the lower formwork F. The boundary between the outer periphery of the upper end of the straight pipe 12 of the sheath 1 and the outer periphery of the lower end of the parallel portion 21 of the joint 2 is sealed by wrapping vinyl tape 4 around it.

[0029] Next, the other sheath tube 10 to be connected is placed vertically inside the formwork F stacked on the upper side so that the base end of the straight tube 11 faces downward, and the base end of the straight tube 11 of that sheath tube 10 is inserted through the opening of the expanded diameter portion 22 of the joint 2 of the sheath tube 10 in the lower tier.

[0030] 3, the upper sheath tube 10 is lowered and the lower end of its straight tube 11 is inserted so as to be pushed into the parallel portion 21 of the joint 2 of the lower sheath tube 10. The lowering of the upper sheath tube 10 stops when the lower end of the straight tube 11 hits the upper end of the straight tube 13 of the lower sheath tube 10.

[0031] In this state, the gap between the inner circumference of the parallel portion 21 of the lower joint 2 and the outer circumference of the straight tube 11 of the upper sheath 1 is sealed by the sealing material 3 wrapped around the outer circumference of the base end portion, which is the lower end portion of the straight tube 11 of the upper sheath 1.

[0032] This process is repeated a predetermined number of times, as shown in Figure 4, and then concrete is poured into the formwork F stacked from the lower formwork F to the upper formwork F, so that the connected sheaths 1 communicate vertically inside the concrete.

[0033] <Effects> When constructing a concrete structure as described above, the base end of the sheath 1 of the upper sheath tube body 10 is guided into the expanded diameter portion 22 of the joint 2 and reaches the parallel portion 21 of the joint 2 of the lower sheath tube body 10, so that the sheaths 1 can be easily connected to each other.

[0034] Furthermore, the spaces between the lower sheath 1 and the upper sheath 1 and the parallel portion 21 of the lower joint 2 connecting them are sealed with sealing material 3, thereby preventing concrete from seeping into the sheath 1 and the joint 2 when pouring concrete.

[0035] <Other> In the above embodiment, a concrete structure that extends vertically, such as the main tower of a cable-stayed bridge, was given as an example. However, the sheath connection structure and construction method of the present invention are not limited to application to concrete structures that extend vertically, and can also be applied to concrete structures that extend horizontally, such as bridge girders and floor slabs. [Explanation of symbols]

[0036] 1 sheath 2 Joint 3. Sealing material 4 vinyl tape 10 Sheath tube body 11,12,13 straight pipe 21 Parallel section 22 Expanded diameter part F-formwork

Claims

1. In a connection structure via a joint (2) between sheaths (1) through which tendons of a prestressed concrete structure are inserted, The joint (2) is funnel-shaped and has a parallel portion (21) and an expanded diameter portion (22), One sheath (1) to be connected is inserted into the inside of the joint (2) through the opening of the parallel portion (21) of the joint (2), and the other sheath (1) is inserted into the inside of the joint (2) through the opening of the enlarged diameter portion (22) of the joint (2); A sheath connection structure characterized in that each of the sheaths (1) and the joint (2) is sealed at the parallel portion (21) of the joint (2).

2. 2. The sheath connection structure according to claim 1, wherein the sheath (1) is installed in a vertical direction.

3. 2. The sheath connection structure according to claim 1, wherein the sheath (1) and the parallel portion (21) of the joint (2) are sealed with a cloth-like sealing material (3).

4. 2. The sheath connection structure according to claim 1, wherein the sheath (1) and the parallel portion (21) of the joint (2) are sealed with a water-swellable sealing material (3).

5. 2. The sheath connection structure according to claim 1, wherein the sheath (1) inserted from the parallel portion (21) of the joint (2) is extendable in the longitudinal direction.

6. 6. The sheath connection structure according to claim 5, wherein the sheath (1) inserted from the parallel portion (21) of the joint (2) is a straight tube (11, 13) having a spiral convex ridge on its outer surface and a straight tube (12) having a spiral concave ridge on its inner surface that are threaded together, and expands and contracts in the longitudinal direction as the sheath advances.

7. A method for constructing a concrete structure includes stacking formwork (F) in a plurality of stages, connecting sheath pipes (10) erected inside the formwork (F) of each stage, and pouring concrete inside the formwork (F), The sheath tubular body (10) has an expanded diameter portion (22) on the distal end side, a step of vertically erecting the sheath tubular body (10) in a lower mold (F) so that the enlarged diameter portion (22) faces upward; a step of placing the sheath tubular body (10) with the cloth-like sealing material (3) wrapped around the outer periphery of the base end portion vertically in an upper mold (F) with the base end portion facing downward, and inserting the expanded diameter portion (22) on the tip side into the sheath tubular body (10) in the lower mold (F); After repeating the above steps a predetermined number of times, pouring concrete into the formwork (F); A method for constructing a concrete structure, comprising:

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