Jacket unit for intermediate fixing device of tensioning material

Abstract

The present invention provides a jacket unit that can suppress the reduction in fixing force caused by the wedge being pressed in. [Solution] The jacket unit 1 of the present invention consists of a pair of jacket pieces 2 that can be assembled together by a plurality of connecting bolts B, and each jacket piece 2 comprises a main body block 21, a tapered groove 22 provided along the length direction in the center of the width direction of the bottom surface of the main body block 21, and bolt holes 23 extending in the height direction of the main body block 21, with a plurality of bolt holes 23 arranged in pairs on both sides of the width direction of the main body block 21 and along the length direction of the main body block 21, wherein one of the two bolt holes 23 that form a pair in the width direction of the main body block 21 is a threaded hole 23b and the other is a through hole 23a without a thread, and when the pair of main body blocks 21 are assembled, the orientation of the connecting bolts B is point symmetric with respect to the axis of the tensioning member D.

Description

Technical Field

[0001] The present invention relates to a jacket unit used for an intermediate fixing tool of a prestressing tendon in a prestressed concrete structure.

Background Art

[0002] In the renovation work of prestressed concrete structures such as T-girder bridges and I-girder bridges, it may be necessary to replace some of the existing PC steel materials (prestressing tendons). In such cases, in order to maintain the functions of the entire structure, especially the performance of the girder, and to remove the girder step by step while keeping traffic flowing, an intermediate fixing method may be adopted. By the intermediate fixing method, the girder, floor slab, and prestressing tendons embedded therein to be removed can be safely and surely removed. Patent Document 1 discloses an intermediate fixing tool comprising a frustum-shaped wedge and a pair of jacket members (jacket pieces) for accommodating the wedge. With the intermediate fixing tool, with the split-structured wedge attached to the prestressing tendon, the wedge is sandwiched from both sides by a pair of jacket pieces and integrally fastened by a plurality of bolts, thereby firmly fixing the jacket pieces to the prestressing tendon via the wedge (Fig. 5). Specifically, the bolt holes of one jacket piece consist of insertion holes without screw grooves, the bolt holes of the other jacket piece consist of screw groove holes, the bottom surfaces of the two jacket pieces are opposed, the tip of the bolt is inserted from the upper surface of one jacket piece into the insertion hole, and screwed into the screw groove hole of the other jacket piece and fastened to integrate the two jacket pieces.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional intermediate anchoring devices have a problem where the bolt insertion direction is limited to one direction, and the bolt heads are concentrated on one jacket piece side, resulting in an uneven transmission of reaction force between the two jacket pieces. In other words, when the two jacket pieces are assembled and the wedge is pressed between them, a force is generated between the two jacket pieces in the direction of separation, and an axial tensile force acts on the bolt. At this time, the reaction force of the bolt is concentrated in the thread grooves near the assembly surface (bottom surface) of the jacket piece on the tip side, while in the jacket piece on the bolt head side, it is distributed within the jacket piece via the seating surface of the bolt head (Figures 6 and 7). As a result, the jacket piece on the bolt head side experiences relatively insufficient tightening force near the bottom surface, leading to an uneven tightening force between the jacket pieces. This makes it easier for gaps to form at the assembly surfaces of the two jacket pieces. These gaps between the jacket pieces can cause uneven wire gripping force in the wedge, potentially leading to a decrease in the wedge's anchoring force. This risk becomes more pronounced as the tension force increases. [Means for solving the problem]

[0005] The jacket unit of the present invention consists of a pair of jacket pieces that can be assembled together by a plurality of connecting bolts, each jacket piece comprising a main body block, a tapered groove provided along the length direction in the center of the width direction of the bottom surface of the main body block, and a plurality of bolt holes extending in the height direction of the main body block, which are arranged in pairs on both sides of the width direction of the main body block and along the length direction of the main body block, wherein one of the two bolt holes that form a pair in the width direction of the main body block is a threaded hole and the other is a through hole without a thread, and when the bottom surfaces of the pair of main body blocks are facing each other with their length directions aligned, and the tip of the connecting bolt is inserted through the through hole of one main body block and screwed into the threaded hole of the other main body block, the orientation of the connecting bolt is point-symmetric with respect to the axis of the tensioning member in each cross section in the length direction of the pair of main body blocks.

[0006] In the jacket unit of the present invention, through holes and screw grooves may be arranged alternately along the length of the main body block. This configuration allows the unevenness of reaction forces caused by the fastening of connecting bolts to cancel each other out in the longitudinal direction, further improving the function of suppressing gap formation.

[0007] The jacket unit of the present invention may have a main body block that includes a recessed receiving recess on its upper surface, and an insertion hole may be provided on the bottom surface of the receiving recess. This configuration avoids interference with the outside by housing the bolt heads of the connecting bolts within the recessed areas, and also reduces the dispersion of reaction forces by bringing the seating surface of the bolt heads closer to the bottom surface.

[0008] The jacket unit of the present invention may consist of a pair of jacket pieces that are identical in shape. This configuration makes inventory management and on-site handling of jacket pieces easier. [Effects of the Invention]

[0009] The jacket unit of the present invention, by arranging the insertion direction of the connecting bolts in opposite directions in the widthwise cross-section, allows the uneven distribution of reaction forces caused by the fastening of the connecting bolts to be mutually compensated for, thereby eliminating the uneven distribution of tightening force between a pair of jacket pieces. This reduces the occurrence of gaps between jacket pieces due to the press-fitting of the wedge and suppresses the decrease in fixing force due to uneven tensioning force of the wedge. [Brief explanation of the drawing]

[0010] [Figure 1] Diagram illustrating the intermediate fixing device and jacket unit. [Figure 2] Explanation diagram of the jacket piece [Figure 3] Cross-sectional view of the jacket unit in the width direction [Figure 4] Diagram illustrating Example 2 [Figure 5]Explanatory drawing of a conventional intermediate fixing tool [Figure 6] Width-direction cross-sectional view of a conventional jacket unit [Figure 7] Axial-direction cross-sectional view of a conventional jacket unit

Modes for Carrying Out the Invention

[0011] Hereinafter, a jacket unit for an intermediate fixing tool of a prestressing tendon of the present invention (hereinafter referred to as "jacket unit") will be described in detail with reference to the drawings. In the present invention, the "length direction" means the direction parallel to the axial direction of the prestressing tendon in a state where the jacket unit is assembled to the prestressing tendon and the wedge, the "width direction" means the direction orthogonal to the length direction along the bottom surface of the jacket piece, and the "height direction" means the direction orthogonal to the length direction and the width direction.

Examples

[0012] <1> Jacket unit (FIG. 1) The jacket unit 1 of the present invention is a member used for an intermediate fixing tool A of a prestressing tendon D in the construction of a prestressed concrete structure. The jacket unit 1 is formed by integrally assembling a pair of jacket pieces 2 arranged with their bottom surfaces facing each other with a plurality of connecting bolts B. The jacket unit 1 is characterized in that in a state where a pair of jacket pieces 2 are integrally assembled, the direction of the connecting bolts B is point-symmetrical about the axis of the prestressing tendon D in each cross-section in the length direction of the jacket piece 2.

[0013] <2> Jacket piece (FIG. 2) The jacket piece 2 is a divided body constituting the jacket unit 1. The jacket piece 2 includes at least a main body block 21, a tapered groove 22 provided along the length direction at the center in the width direction of the bottom surface of the main body block 21, and a plurality of bolt holes 23 extending in the height direction of the main body block 21. In this example, a total of eight bolt holes 23 are provided in each jacket piece 2. In this example, a pair of jacket pieces 2 constituting the jacket unit 1 are made of members having the same shape. This facilitates inventory management and on-site handling of the jacket pieces 2.

[0014] <2.1> Body block The body block 21 is the main body member of the jacket piece 2. The body block 21 has a bottom surface at the bottom that serves as an assembly surface with another body block 21. In this example, a steel material having a substantially cubic outer shape is adopted as the body block 21. In this example, a plurality of receiving recesses 21a for receiving the bolt heads of the connecting bolts B are formed on the upper surface of the body block 21.

[0015] <2.1.1> Receiving recess The receiving recess 21a is a structure for receiving the bolt head of the connecting bolt B. The receiving recess 21a is formed by forming the upper surface of the body block 21 into a concave shape with a predetermined depth. The receiving recess 21a has a height and width capable of receiving the bolt head of the connecting bolt B, and an insertion hole 23a is provided in the bottom surface. By accommodating the bolt head of the connecting bolt B in the receiving recess 21a, interference with the outside can be avoided, and the seating surface of the bolt head can be brought closer to the bottom surface side to reduce the dispersion of the reaction force. However, the receiving recess 21a is not an essential component of the body block 21. [[ID= thirty]]

[0016] [[ID= thirty-one]] [[ID= thirty-two]]<2.2> Taper groove [[ID= thirty-three]] [[ID= thirty-four]]The taper groove 22 is a groove for accommodating the wedge C. [[ID= thirty-five]] [[ID= thirty-six]]The taper groove 22 is continuously provided along the length direction at the center in the width direction of the bottom surface of the body block 21. [[ID= thirty-seven]] [[ID= thirty-eight]]The inner surface of the taper groove 22 expands in diameter from one end in the length direction to the other end so as to correspond to the outer shape of the wedge C. [[ID= thirty-nine]] [[ID= forty]]

[0017] [[ID= forty-one]] [[ID= forty-two]]<2.3> Bolt hole [[ID= forty-three]] The bolt hole 23 is a hole for inserting and screwing in the connecting bolt B. The bolt holes 23 are provided outside the tapered grooves 22 in the width direction of the main block 21. The bolt hole 23 consists of a combination of a through hole 23a and a screw groove hole 23b. The through hole 23a is the hole on the side into which the connecting bolt B is inserted, and is a non-threaded hole without screw threads. The through hole 23a connects both sides of the jacket piece 2. The screw groove hole 23b is a hole on the side into which the connecting bolt B is screwed, and is a screw hole equipped with a screw groove. The screw groove hole 23b is drilled to a predetermined depth from the bottom surface to the top surface of the jacket piece 2. However, both sides of the jacket piece 2 may be connected. When the pair of jacket pieces 2 are assembled, the insertion hole 23a of one jacket piece 2 and the screw groove hole 23b of the other jacket piece 2 are arranged coaxially. When screwing the connecting bolt B into the jacket unit 1, the tip of the connecting bolt B is inserted into the insertion hole 23a from the upper surface of one jacket piece 2, and then screwed into the threaded hole 23b from the bottom surface of the other jacket piece 2.

[0018] <2.3.1> Bolt hole arrangement (Figure 3) The bolt holes 23 are arranged in a row on each side in the width direction of the main body block 21, and at predetermined intervals along the length direction of the main body block 21. In the jacket unit 1 of the present invention, of the two bolt holes 23 arranged in a pair in the width direction of the main body block 21, one is a through hole 23a and the other is a screw groove hole 23b. Therefore, in the width direction cross-section when the pair of jacket pieces 2 are assembled, the insertion direction of the connecting bolts B is in opposite directions, that is, the arrangement is point-symmetric with respect to the axis of the tensioning member D. In this example, through holes 23a and screw groove holes 23b are arranged alternately along the length of the main body block 21. As a result, in the longitudinal cross-section of the assembled pair of jacket pieces 2, the insertion directions of adjacent connecting bolts B in the longitudinal direction are reversed.

[0019] <3> Assembly method The jacket unit 1 of the present invention is assembled, for example, by the following method. A pair of jacket pieces 2 are positioned with their tapered grooves 22 facing each other, and a tensioning member D is sandwiched between them from both sides. At this time, the insertion holes 23a and screw groove holes 23b of the two jacket pieces 2 are aligned coaxially. The tensioning member D includes PC steel materials such as multi-wire, steel rod, and stranded wire. The connecting bolt B is inserted into the through hole 23a from the upper surface of one jacket piece 2 and then screwed into the threaded hole 23b of the other jacket piece 2 to secure it. The two jacket pieces 2 are turned inside out using the tensioning material D as the axis, and the connecting bolt B is similarly screwed into the other jacket piece 2 to secure it. As a result, the pair of jacket pieces 2 are assembled together using connecting bolts B, completing the jacket unit 1.

[0020] <4> Effects (Figure 3) When the wedge C is attached to the tensioning member D and pressed into the tapered groove 22 with a jack, a separating force is generated between the two jacket pieces 2, and an axial tensile force acts on the connecting bolt B. In the jacket unit 1 of the present invention, the insertion direction of the connecting bolt B is arranged in opposite directions in the widthwise cross-section. Therefore, when observed from the axial direction of the tensioning member D, the reaction force concentrated in the screw groove hole 23b due to the fastening of the connecting bolt B and the reaction force distributed on the seating surface of the bolt head mutually compensate for each other, resulting in an extremely rational structure. This eliminates the uneven distribution of tightening force between the two jacket pieces 2 and suppresses the occurrence of gaps due to the press-fitting of the wedge C. Furthermore, in this example, the connecting bolt B is positioned in the opposite direction vertically in the longitudinal cross-section. As a result, the bias in reaction force generated by fastening the connecting bolt B is canceled out in the longitudinal direction as well, further improving the function of suppressing gap formation.

[0021] <5> Features of the present invention The configuration described above was conceived for the first time through a novel approach that considers the distribution of the tightening force of the connecting bolt B acting on the jacket unit 1 and the resulting reaction force from the axial direction of the tensioning member D, and is a remarkable feature not found in conventional technology. In other words, in conventional technology, it was common to align the bolt heads of the connecting bolts with one of the jacket pieces, and the idea of ​​inserting the connecting bolts in the opposite direction (up or down) did not exist. Furthermore, such a structure is disadvantageous from the standpoint of workability because the insertion directions of the connecting bolts are mixed during the assembly of jacket piece 2. For this reason, there is no motivation for a person skilled in the art to redesign the jacket unit in the conventional technology to reverse the insertion direction of the connecting bolts. [Examples]

[0022] [Other structures of the jacket unit] (Figure 4) The jacket unit 1 is not limited to the configuration of Embodiment 1, but may have configurations such as the following. The number of bolt holes 23 in each jacket piece 2 is not limited to 8; it may be 6, 10, or any other number. The main body block 21 may not have a receiving recess 21a, and the upper surface of the main body block 21 may be used as a seating surface for the bolt head (Figure 4(a)). In the longitudinal direction of the main body block 21, the through holes 23a and screw groove holes 23b may not be arranged alternately, but rather continuously, for example, as follows: through hole 23a, through hole 23a, screw groove hole 23b, screw groove hole 23b (Figure 4(b)). The main block 21 does not have to be a roughly cubic shape externally; it may be a roughly semi-cylindrical shape with a curved top surface or other shapes (Figure 4(c)). [Explanation of Symbols]

[0023] 1 Jacket Unit 2 jacket pieces 21 Main block 21a Receiving recess 22 Tapered grooves 23 bolt holes 23a Through hole 23b Screw groove hole A Intermediate fixing device B Connecting bolt C Wedge D Tensile material

Claims

1. A jacket unit used as an intermediate fixing device for tensioning material, It consists of a pair of jacket pieces that can be assembled together by multiple connecting bolts, Each of the aforementioned jacket pieces is The main block and A tapered groove is provided along the length direction at the center in the width direction of the bottom surface of the main body block, The main body block comprises a plurality of bolt holes extending in the height direction, arranged in pairs on both sides in the width direction of the main body block and aligned along the length direction of the main body block, The two bolt holes that form a pair in the width direction of the main body block are, one of which is a threaded hole and the other is a through hole without a thread. The connection is characterized in that, when a pair of main body blocks are aligned in their longitudinal directions and their bottom surfaces are facing each other, and the tip of the connecting bolt is inserted through the insertion hole of one of the main body blocks and screwed into the threaded hole of the other main body block, the orientation of the connecting bolt is point-symmetric with respect to the axis of the tensioning member in each cross-section along the longitudinal direction of the pair of main body blocks. Jacket unit.

2. The main body block is characterized in that the through holes and screw grooves are arranged alternately along its length. The jacket unit according to claim 1.

3. The main body block is provided with a recessed receiving recess on its upper surface, The insertion hole is provided on the bottom surface of the receiving recess, The jacket unit according to claim 1 or 2.

4. The pair of jacket pieces are characterized by having the same shape. The jacket unit according to claim 1 or 2.

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