Spiral reinforcing bar for joint part

Abstract

To provide a spiral reinforcing bar for joint parts capable of being smoothly arranged in a joint part between concrete slabs and enlarging a scope to which the restraining effect of concrete extends.SOLUTION: A spiral reinforcement bar, being arranged in a joint part 22 between a pair of adjoining precast PC floor slabs 20 and forming a bar arrangement structure 15 of the joint part 22 with joint reinforcement bars 21 protruding from edge faces 20a of the precast PC floor slabs 20 on both sides, has a spiral shape in which a plurality of unit spiral reinforcement bars 11 having a rectangular front shape resulting from a bending processing of one reinforcement bar are made to continue at a prescribed pitch. The continuing unit spiral reinforcement bars 11 result in diagonal connection reinforcement where, in the rectangular front shape, a pair of left and right vertical sides 11a, 11b and one horizontal side 11c are arranged along a virtual base surface P and the other horizontal side 11d extends in a direction tilted with respect to the virtual base surface P, and have a Z-spiral shape.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spiral reinforcing bar for a joint, and more particularly to a spiral reinforcing bar for a joint that is arranged in the joint between a pair of adjacent concrete slabs to form a reinforcement structure at the joint. [Background technology]

[0002] In recent years, many large-scale renovation projects have been ordered, for example, to address the deterioration of concrete decks of existing road bridges by replacing the decks. Furthermore, for renovation work involving concrete deck replacement, rectangular precast PC decks made of precast concrete are commonly used to reduce construction labor and shorten construction time. In renovation work using precast PC decks, for example, on existing road bridges, the road bridge piers have columns extending vertically from the ground and beams extending to the left and right from the columns. Multiple girders are installed between the beams of adjacent piers in the bridge axis direction. The precast PC deck, which forms the main part of the road, is supported by multiple girders installed at predetermined intervals in a direction perpendicular to the bridge axis direction, with its long sides preferably aligned perpendicularly to these girders and installed in a continuous manner in the bridge axis direction.

[0003] In addition, the precast PC deck slabs are supported by multiple bridge girders and installed in a series in the bridge axis direction, and are integrated by placing steel bars and pouring concrete at the joints along the long sides between each pair of adjacent precast PC deck slabs in the bridge axis direction.

[0004] For this reason, in the conventional general joint structure, multiple loop-shaped joint reinforcements (loop joints) are preferably used as joint reinforcement from the end face along the long side of the installed precast PC deck slab. These loop joint reinforcements are then attached to adjacent pairs of precast PC floors. The loop joint reinforcement bars are arranged alternately at the joint between the slabs, and long, straight connecting main reinforcement bars that connect the loop joint reinforcement bars are inserted inside the annular parts of the alternately arranged loop joint reinforcement bars that overlap when viewed from the length direction of the joint reinforcement, in the length direction of the joint reinforcement along the long side part, and after arranging the reinforcement in the specified position, concrete is poured into the joint reinforcement, which is a joint reinforcement structure that is formed.

[0005] On the other hand, in the conventional general joint structure described above, the work of inserting long main reinforcement bars inside the ring-shaped portion where the alternately arranged, preferably loop joint reinforcement bars, overlap, and the work of arranging the inserted long main reinforcement bars in the designated position in the ring-shaped portion require a special overhanging scaffolding to be set up on the side of the bridge girder, and the work of holding long, straight reinforcing bars from the overhanging scaffolding to insert them inside the ring-shaped portion, inserting the reinforcing bars through reinforcing bar insertion ports set up at the bridge girder position, and tying the reinforcing bars inserted inside the ring-shaped portion in the designated position while lifted up, so a technology has been proposed that makes this work unnecessary (see, for example, Patent Document 1).

[0006] According to the joint structure of the precast deck in Patent Document 1, the joint reinforcing bars are arranged alternately between a pair of adjacent precast PC decks, and preferably spiral reinforcing bars are dropped from above to be fitted into the gaps between each of the loop-shaped reinforcing bars, thereby making it possible to pre-install long, straight connecting main bars that connect the loop-shaped reinforcing bars outside the annular portion where the alternately arranged loop joint reinforcing bars overlap. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-49621 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the joint structure of the precast deck in Patent Document 1, the spiral reinforcing bars have a constant angle of spiral relative to the central axis, and when viewed from the outside in the axial direction (lengthwise), they have a circular front shape. This makes it time-consuming to position them on site when arranging them in the joint, and the range of the concrete restraining effect of the spiral reinforcing bars is limited to the circular area, preferably inside the ring-shaped part, where the alternately arranged joint reinforcing bars, for example, loop joint reinforcing bars, overlap. Therefore, it is no longer possible to omit the straight connecting main reinforcing bars, which are arranged, for example, outside the ring-shaped part where the loop joint reinforcing bars overlap.

[0009] The present invention aims to provide a spiral reinforcing bar for a joint that allows smooth positioning and reinforcement at the joint between a pair of adjacent concrete slabs, preferably precast PC deck slabs, and that widens the range over which the restraining effect of the concrete extends, thereby making it possible to omit the linear connecting main bars that connect the joint reinforcing bars to each other. [Means for solving the problem]

[0010] The present invention provides a spiral reinforcing bar for a joint that is arranged in the concrete pouring space of a joint between a pair of adjacent concrete slabs and forms a reinforcement structure at the joint together with joint reinforcing bars that each protrude from the end faces of the concrete slabs on both sides facing each other in the pouring space.The spiral reinforcing bar has a spiral shape in which a plurality of unit spiral reinforcing bars, each having a rectangular front view, are connected at a predetermined pitch in the axial direction of the spiral by bending a single reinforcing bar.Each of the continuous unit spiral reinforcing bars has a pair of left and right vertical side portions and one horizontal side portion of the rectangular front view that are arranged on an imaginary base plane, and the other horizontal side portion is an oblique connecting bar that extends in a direction inclined at an angle of 10 to 35 degrees when viewed from above relative to the imaginary base plane on which these three side portions are arranged.This has achieved the above-mentioned object by providing a spiral reinforcing bar for a joint that has a Z-spiral shape with a continuous Z shape when viewed from above.

[0011] In the spiral reinforcing bar for a joint of the present invention, it is preferable that the imaginary base surface is a surface perpendicular to the axial direction of the spiral.

[0012] Furthermore, in the spiral reinforcement for the joint section of the present invention, the joint reinforcement bars protruding from the end faces of the concrete slabs on both sides are arranged in two stages, including upper reinforcement and lower reinforcement, and the joint reinforcement bars protruding from one end face of the concrete slab and the joint reinforcement bars protruding from the other end face of the concrete slab are arranged alternately in a staggered pattern along the length of the joint section, and it is preferable that the three side portions arranged on the imaginary base surface are arranged in the spaces between the alternately arranged joint reinforcement bars, and the diagonal connecting bars are arranged so as to intersect with the upper reinforcement bars, so that reinforcement can be arranged in the joint section.

[0013] Furthermore, it is preferable that the spiral reinforcing bar for joint parts of the present invention is configured so that the three side portions arranged on the virtual base surface are arranged every other one in the gaps between the alternately arranged joint reinforcing bars.

[0014] Furthermore, it is preferable that the spiral reinforcing bar for the joint portion of the present invention is a loop reinforcing bar in which the end of the upper reinforcing bar and the end of the lower reinforcing bar are connected via an arc-shaped portion.

[0015] Furthermore, it is preferable that the spiral steel bar for joints of the present invention is such that the joint between a pair of adjacent concrete slabs is a joint between a pair of adjacent precast PC deck slabs. [Effects of the Invention]

[0016] The spiral reinforcing bars for joints of the present invention can be smoothly positioned and arranged at the joints between a pair of adjacent concrete slabs, and by expanding the range over which the restraining effect of the concrete extends, it is possible to omit the straight connecting main bars that connect the joint reinforcing bars to each other. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a perspective view of a spiral reinforcing bar for a joint according to a preferred embodiment of the present invention. FIG. [Figure 2] 1 from the Z direction, and FIG. 1(b) is a side view of FIG. 1 from the Y direction. [Figure 3] FIG. 2 is a front view of FIG. 1 as seen from the X direction, which is the axial direction of the spiral. [Figure 4] 1(a) to 1(c) are perspective views illustrating a reinforcement structure for a joint using a spiral reinforcing bar for a joint according to a preferred embodiment of the present invention. [Figure 5] (a) is a cross-sectional view of a key part illustrating joint reinforcing bars that each protrude from the end face of a concrete slab, and (b) is a cross-sectional view of a key part illustrating the reinforcement structure using the joint reinforcing bars of (a). [Figure 6] (a) is a cross-sectional view of a key part illustrating other joint reinforcing bars each protruding from the end face of a concrete slab, and (b) is a cross-sectional view of a key part illustrating the reinforcement structure using the other joint reinforcing bars of (a). [Figure 7] 10(a) to 10(c) are schematic plan views illustrating a state in which a spiral reinforcing bar for a joint is bound to a joint reinforcing bar. [Figure 8] FIG. 10 is a simplified perspective view illustrating a joint between multiple precast PC deck slabs installed in series. DETAILED DESCRIPTION OF THE INVENTION

[0018] A spiral reinforcing bar 10 for a joint according to a preferred embodiment of the present invention shown in Fig. 1 is used, for example, in repair work on an existing road bridge, when replacing an aged concrete slab with a precast PC slab 20, preferably made of precast concrete. As shown in Fig. 8, the spiral reinforcing bar 10 is arranged at each of the joints 22 of the precast PC slabs 20, which are arranged in a row in the bridge axis direction, and is used together with the joint reinforcing bars 21 protruding from the end faces 20a of the precast PC slabs 20 to form a reinforcement structure 15 (see Figs. 4(a) to (c)) for the joints 22 prior to pouring concrete into the joints 22. The spiral reinforcing bar 10 for a joint according to this embodiment allows for smooth positioning and reinforcement at the joints 22 between a pair of adjacent precast PC slabs 20, and also functions to omit the linear connecting main bars that connect the joint reinforcing bars 21 by expanding the range of the concrete's restraining effect.

[0019] As shown in Figures 1 to 4, the spiral reinforcing bar 10 for the joint section in this embodiment is arranged in the concrete pouring space of the joint section 22 between a pair of adjacent concrete slabs, preferably a pair of adjacent precast PC deck slabs 20, and together with the joint reinforcing bars 21 protruding from the end faces 20a of the precast PC deck slabs 20 on both sides facing each other in this pouring space, it is a spiral-shaped reinforcing bar that forms the reinforcement structure 15 in the joint section 22. The spiral reinforcing bar 10 for joints in this embodiment has a spiral shape in which a plurality of unit spiral reinforcing bars 11 having a rectangular front view (see Figure 3) are connected at a predetermined pitch in the spiral axial direction X by bending a single reinforcing bar (see Figures 1, 2(a), and (b)). Each continuous unit spiral reinforcing bar 11 has a pair of short side portions 11a and 11b, which are the left and right vertical side portions of the rectangular front view, and a long side portion 11c, which is one horizontal side portion, arranged along an imaginary base plane P (see Figures 2(a) and (b)), and the other horizontal side portion, the long side portion 11d, is an oblique connecting bar that extends in an inclined direction at an angle θ of 10 to 35 degrees, more preferably 10 to 20 degrees (see Figure 2(a)), when viewed from above, relative to the imaginary base plane P on which these three side portions are arranged, thereby forming a Z-spiral shape in which Z shapes are continuous when viewed from above.

[0020] In addition, in this embodiment, the joint reinforcing bars 21 protruding from the end faces 20a of the precast PC deck 20 on both sides are arranged in two stages, including upper reinforcing bars 21a and lower reinforcing bars 21b, as shown in Figure 5(a), and the joint reinforcing bars 21 protruding from the end face 20a of one precast PC deck 20 and the joint reinforcing bars 21 protruding from the end face 20a of the other precast PC deck 20 are arranged alternately in a staggered pattern in the longitudinal direction X of the joint portion 22 (see Figure 7(a)).The spiral reinforcing bar 10 can be arranged in the joint portion 22 with its three side portions 11a, 11b, and 11c arranged on the imaginary base surface P arranged in the spaces between the alternately arranged joint reinforcing bars 21, and the diagonal connecting bar 11d of the other long side portion arranged so as to intersect with the upper reinforcing bars 21a.

[0021] Furthermore, in this embodiment, the joint reinforcing bar 21 is preferably a loop reinforcing bar in which the end of the upper reinforcing bar 21a and the end of the lower reinforcing bar 21b are connected via an arc-shaped portion 21c (see Figure 5(a)).

[0022] In this embodiment, the spiral reinforcing bar 10 for a joint is a deformed reinforcing bar with a diameter of, for example, about 10 mm. Using a special reinforcing bar bending machine, it can be easily bent into a spiral shape from a single reinforcing bar. As shown in FIGS. 1 and 2(a) and (b), the spiral reinforcing bar 10 for a joint has a spiral shape in which multiple unit spiral reinforcing bars 11, each having a rectangular front view, are connected in the spiral axial direction X at a predetermined pitch s (half the pitch of the joint reinforcing bars 21 protruding from either end surface 20a of one or the other precast PC deck 20), for example, about 62.5 mm. The imaginary base plane P on which the pair of left and right short side portions 11a, 11b and one long side portion 11c of the unit spiral reinforcing bar 11 are arranged is preferably perpendicular to the spiral axial direction X.

[0023] Furthermore, in this embodiment, when the thickness of the precast PC deck 20 is, for example, about 220 mm and the width of the joint portion 22 is about 280 mm, each unit spiral reinforcing bar 11, when viewed from the front from outside the axial direction X of the spiral, has a horizontally elongated rectangular frame shape, as shown in Figure 3, with the short side portions 11a, 11b, which are the vertical side portions on both the left and right sides, having a length (height) of, for example, about 120 mm, and the long side portions 11c, 11d, which are the horizontal side portions on the top and bottom, having a length of, for example, about 230 mm, and the four corner portions are curved so that the inner radius of curvature is, for example, about R25. The other long side, the upper long side 11d, acts as a diagonal connecting reinforcement and extends at an angle θ of, for example, 15.2 degrees when viewed from above relative to the imaginary base plane P on which the pair of left and right short side portions 11a, 11b and one long side portion 11c are arranged (see Figure 2(a)), resulting in a length of, for example, about 240 mm when viewed from above. The length of these unit spiral reinforcing bars 11 can be changed as appropriate depending on the designed thickness of the precast PC deck 20, the width of the joint portion 22, etc.

[0024] If the spiral reinforcing bar 10 for the joint section cannot be formed from only one reinforcing bar to ensure a length equivalent to the extension of the joint section 22, multiple spiral reinforcing bars 10 for the joint section can be formed from multiple reinforcing bars, and the ends can be overlapped and tied together as a lap portion, for example, to connect them together in the axial direction X of the spiral, thereby forming a spiral reinforcing bar 10 for the joint section with a length equivalent to the extension of the joint section 22.

[0025] On the other hand, in this embodiment, the joint reinforcing bars 21 are loop reinforcing bars in which the ends of the upper reinforcing bars 21a and the lower reinforcing bars 21b are connected via the arc-shaped portion 21c, as described above. The joint reinforcing bars 21 protruding from the end face 20a of one precast PC deck 20 and the joint reinforcing bars 21 protruding from the end face 20a of the other precast PC deck 20 are alternately arranged in a staggered pattern in the length direction X of the joint 22, which is the axial direction X of the spiral of the joint spiral reinforcing bar 10, as shown in Figure 7(a). The upper reinforcing bars 21a and the lower reinforcing bars 21b of these joint reinforcing bars, which are loop reinforcing bars, are preferably arranged so as to protrude perpendicularly from the end face 20a of the precast PC deck 20, which is a concrete slab, when viewed from above.

[0026] 7(a), the spiral reinforcing bar 10 for a joint of this embodiment has three sides, consisting of a pair of left and right short side portions 11a, 11b and one long side portion 11c, arranged on an imaginary base plane P, which are arranged in the spaces between the joint reinforcing bars 21, preferably loop reinforcing bars, which are alternately arranged at a predetermined pitch s', preferably the same as the pitch s of the unit spiral reinforcing bars 11 of the spiral reinforcing bar 10 for a joint, and the diagonal connecting bar of the other long side portion 11d is arranged so as to cross the upper reinforcing bar 21a of the joint reinforcing bar 21, and then tied together with, for example, a tie wire 12, to arrange reinforcement in the joint 22. This makes it easy to form the reinforcing bar arrangement structure 15 for the joint together with the joint reinforcing bars 21, preferably loop reinforcing bars, which are alternately arranged.

[0027] That is, in this embodiment, the reinforcing bar structure 15 of the joint portion is a reinforcing bar structure using spiral reinforcing bars 10 provided in the concrete pouring space of the joint portion 22 between a pair of adjacent concrete slabs, preferably a pair of precast PC floor slabs 20, and the joint reinforcing bars 21 protrude from the end faces of the precast PC floor slabs 20 on both sides facing each other in the concrete pouring space of the joint portion 22, and the joint reinforcing bars 21 are arranged in a state where a plurality of joint reinforcing bars 21 protruding from the end face 20a of one precast PC floor slab 20 and a plurality of joint reinforcing bars 21 protruding from the end face 20a of the other precast PC floor slab 20 are alternately arranged in a staggered pattern in the longitudinal direction X of the joint portion, and the joint reinforcing bars 21 are loop-shaped reinforcing bars in which the ends of the upper reinforcing bars 21a and the lower reinforcing bars 21b arranged in two stages above and below are connected via arc-shaped portions 21c, and the spiral reinforcing bars 10 are arranged on the imaginary base surface P of the spiral reinforcing bars 10. The spiral reinforcing bars 10 are attached to the joint section 22 with the three side sections 11a, 11b, and 11c of each unit spiral reinforcing bar 11 arranged in the spaces between the alternatingly arranged joint reinforcing bars 21, and the diagonal connecting bars 11d arranged so as to intersect with the upper reinforcing bars 21a of the joint reinforcing bars 21. When the attached spiral reinforcing bars 10 are projected from outside in the axial direction X, the area where the loop-shaped joint reinforcing bars 21 protruding from the end face 20a of one precast PC deck 20 and the loop-shaped joint reinforcing bars 21 protruding from the end face 20a of the other precast PC deck 20 overlap is positioned so as to be surrounded by a rectangular frame shape formed by the unit spiral reinforcing bars 11, as shown in Figure 5(b). The attached spiral reinforcing bars 10 and the joint reinforcing bars 21 are preferably tied together using tie wires 12 (see Figure 7) so that they can be installed in the concrete pouring space of the joint section 22.

[0028] As a result, with the spiral reinforcing bar 10 for joints of this embodiment, by smoothly positioning and arranging the reinforcement at the joint between a pair of adjacent precast PC decks 20, it becomes possible to easily form the joint reinforcement structure 15 together with the joint reinforcing bars 21, and by expanding the range over which the restraining effect of the concrete reaches, it becomes possible to omit the linear connecting main reinforcements that connect the joint reinforcing bars 21 to each other. This also makes it possible to effectively prevent the thickness of the precast PC deck slab 20 from becoming thicker than necessary.

[0029] Here, when the installed spiral reinforcing bar 10 is projected from the outside in the axial direction X, the positional relationship in which the area where the loop-shaped joint reinforcing bar 21 protruding from the end face 20a of one precast PC deck 20 and the loop-shaped joint reinforcing bar 21 protruding from the end face 20a of the other precast PC deck 20 overlap is surrounded by a rectangular frame shape made up of the unit spiral reinforcing bar 11 can preferably be a positional relationship in which the inner space portion surrounded by these reinforcing bars in the area where the loop-shaped joint reinforcing bar 21 of one precast PC deck 20 and the loop-shaped joint reinforcing bar 21 of the other precast PC deck 20 overlap is surrounded by the inner edge of the reinforcing bars arranged in a rectangular frame shape made up of the unit spiral reinforcing bar 11 of the spiral reinforcing bar 10.

[0030] In addition, in this embodiment, as shown in Figure 7(b), the spiral reinforcing bar 10 for the joint section is arranged in the concrete pouring space of the joint section 22 by arranging the three side portions 11a, 11b, and 11c arranged on the virtual base surface P of the unit spiral reinforcing bar 11 in the gaps between the alternately arranged joint reinforcing bars 21, and arranging the diagonal connecting bar 11d so as to intersect with the upper reinforcing bar 21a of the joint reinforcing bar 21, and tying the spiral reinforcing bar 10 and the joint reinforcing bar 21 together using a binding wire 12 in a state where the three side portions 11a, 11b, and 11c arranged on the virtual base surface P are close to or in contact with one of the joint reinforcing bars 21 on both sides of the gap, and then biasing them to one side.

[0031] As a result, when viewed from above, the reinforcing bars arranged to cross the gaps between the joint reinforcing bars 21 are generally only diagonal connecting bars 11d, and the space into which a vibrator can be inserted is increased, making it possible to efficiently compact the concrete poured into the joint section 22 in a later process.

[0032] When the spiral reinforcing bar 10 and the joint reinforcing bar 21 are connected together with the three side portions 11a, 11b, and 11c arranged on the imaginary base plane P biased toward one of the joint reinforcing bars 21 on either side of the gap portion, the spiral reinforcing bar 10 can be installed in a positioned state, for example, by connecting the base end and tip end of the diagonal connecting bar 11d to the base end side or tip end side of each of the adjacent joint reinforcing bars 21 that protrude alternately.

[0033] Furthermore, as shown in Figure 7(c), the three-sided spiral reinforcing bar 10 for a joint can be arranged on a virtual base plane P, with the pair of left and right short side portions 11a, 11b and one long side portion 11c, alternately positioned at the intervals between the splice reinforcing bars 21, preferably loop reinforcing bars. In this case, the pitch s of the unit spiral reinforcing bars 11 is 125 mm, which is twice the pitch s' at which the splice reinforcing bars 21 are alternately positioned. The diagonal connecting bar formed by the other long side portion 11d extends in a direction inclined at an angle θ of 28.5 degrees relative to the virtual base plane P when viewed from above. The diagonal connecting bar formed by the one long side portion 11c positioned above is tied to the splice reinforcing bars 21 where the three-sided portions formed by the pair of left and right short side portions 11a, 11b and one long side portion 11c are not positioned off-center. In this case, the amount of reinforcing bar in the spiral reinforcing bar 10 for the joint portion is reduced, so the length formed from one reinforcing bar can be increased, and preferably the number of points tied together by tie bars can be reduced.

[0034] In this embodiment, the joint reinforcing bars 21 protruding from each end face 20a of a pair of precast PC deck slabs 20 do not necessarily have to be loop reinforcing bars in which the end of the upper reinforcing bar 21a and the end of the lower reinforcing bar 21b are connected via an arc-shaped portion 21c, and can also be two-tiered reinforcing bars, for example, as shown in Figure 6(a), consisting of a straight-shaped upper reinforcing bar 21d arranged in the upper tier and a hook-shaped lower reinforcing bar 21e arranged in the lower tier, with the tip of the straight portion curved in a hook shape.

[0035] In this case, the reinforcement structure 15' of the joint portion is arranged such that the three side portions 11a, 11b, 11c arranged on the virtual base surface P of the unit spiral reinforcing bar 11 of the spiral reinforcing bar 10 are arranged in the intervals of the joint reinforcing bar 21' which is a two-stage arrangement of straight upper reinforcing bars 21d and hooked lower reinforcing bars 21e arranged alternately (see Figures 7(a) and (b)), and the diagonal connecting bars 11d are arranged so as to intersect with the straight upper reinforcing bars 21d of the joint reinforcing bars 21', and are arranged When viewed from outside in the axial direction X of the spiral reinforcing bar 10, as shown in Figure 6(b), the area surrounded by the lower reinforcing bars 21e on both the left and right sides made of hook reinforcement and the straight-shaped upper reinforcing bar 21d is further surrounded by the rectangular frame shape of the unit spiral reinforcing bar 11, and by tying the spiral reinforcing bar 10 and the joint reinforcing bar 21' using a tie wire 12, the spiral reinforcing bar 10 can be installed in the concrete pouring space of the joint part 22.

[0036] In this embodiment, the joint reinforcing bars that protrude from the end surface 20a of the precast PC deck 20 that constitutes the reinforcement structure of the joint portion into the concrete pouring space of the joint portion 22 do not have to be the loop reinforcing bars or those that consist of the straight upper reinforcing bars 21d and the hooked lower reinforcing bars 21e described above. The joint reinforcing bars may be reinforcing bars in which the upper reinforcing bars 21d are hooked and the lower reinforcing bars 21e are straight, or the upper and lower reinforcing bars of the two-stage reinforcement arrangement may both be straight reinforcing bars (not shown).

[0037] Furthermore, the joint section to which the spiral reinforcing bars 10 are attached and the reinforcement structure of the joint section is established does not necessarily have to be the joint section 22 between multiple precast PC deck slabs 20 installed in a continuous line in the bridge axis direction, but may also be, for example, the joint section between a pair of adjacent concrete slabs formed by cast-in-place concrete.

[0038] Therefore, in this embodiment, the reinforcement structure of the joint section is a reinforcement structure using spiral reinforcing bars 10 that is installed in the concrete pouring space of the joint section between a pair of adjacent concrete slabs, and the joint reinforcing bars each protrude from the end faces of the concrete slabs on both sides facing each other in the concrete pouring space of the joint section, and are arranged in two stages of reinforcement including upper reinforcing bars and lower reinforcing bars, with the joint reinforcing bars protruding from the end face of one concrete slab and the joint reinforcing bars protruding from the end face of the other concrete slab being arranged alternately in a staggered pattern along the length of the joint section, and the three sides of the spiral reinforcing bars 10 arranged on the imaginary base surface P are arranged in the spaces between the alternately arranged joint reinforcing bars, and the spiral reinforcing bars 10 are attached to the joint section 22 in a state where the diagonal connecting bars are arranged so as to intersect with the upper reinforcing bars of the joint reinforcing bars, and the attached spiral reinforcing bars 10 and the joint reinforcing bars are tied together using tie wires 12, so that they can be installed in the concrete pouring space of the joint section.

[0039] The spiral reinforcing bar for joints of the present invention is not limited to the above-described embodiment and can be modified in various ways. For example, the rectangular front shape of a unit spiral reinforcing bar, consisting of a pair of vertical sides and a pair of horizontal sides, does not necessarily have to be a horizontally elongated rectangular frame shape with the vertical sides as short sides and the horizontal sides as long sides. For example, the horizontally elongated rectangular frame shape can include a horizontally elongated oval shape with the short sides curved in an arc. The same effects can be achieved even when the short sides are curved in a horizontally elongated oval shape. The inclination angle of the diagonal continuous reinforcing bars (diagonal connecting reinforcing bars), which are preferably extended in a direction inclined at an angle of 10 to 35 degrees when viewed from above, can be either a right- or left-hand oblique angle, and the spiral shape, which has a continuous Z-shape when viewed from above, can be an inverted Z pattern. [Explanation of symbols]

[0040] 10 Spiral reinforcing bars for joints 11 units spiral rebar 11a, 11b Short side part (vertical side part) 11c One long side (horizontal side) 11d Diagonal connecting bars (one long side, horizontal side) 12 Binding wire 15,15' Reinforcement structure 20 Precast PC deck 20a end face 21,21' Reinforced concrete joint 21a Upper reinforcing bar 21b Bottom rebar 21c Arc-shaped part 21d Straight top rebar 21e Bottom reinforcement with hook bars 22 Joint P Virtual base plane θ Angle between the diagonal connecting bar and the virtual base surface when viewed from above s unit spiral rebar pitch s' Pitch of joint rebar X Spiral axial direction (longitudinal direction of joint)

Claims

1. A spiral reinforcing bar for a joint is arranged in a concrete pouring space of a joint between a pair of adjacent concrete slabs, and forms a reinforcement structure in the joint together with joint reinforcing bars protruding from the end faces of the concrete slabs on both sides facing each other in the pouring space. By bending a single rebar, a plurality of unit spiral rebars each having a rectangular frontal shape are arranged in a spiral shape in the axial direction of the spiral at a predetermined pitch. Each of the continuous unit spiral rebars has a pair of vertical side portions and one horizontal side portion of its rectangular front shape that are arranged on an imaginary base surface, and the other horizontal side portion is an oblique connecting bar that extends in a direction inclined at an angle of 10 to 35 degrees when viewed from above relative to the imaginary base surface on which these three side portions are arranged, resulting in a spiral rebar for joints that has a Z-spiral shape with a continuous Z shape when viewed from above.

2. 2. A spiral reinforcing bar for a joint according to claim 1, wherein the imaginary base plane is a plane perpendicular to the axial direction of the spiral.

3. 3. A spiral reinforcing bar for a joint portion according to claim 1 or 2, wherein the joint reinforcing bars protruding from each end face of the concrete slabs on both sides are arranged in two stages including upper reinforcing bars and lower reinforcing bars, and the joint reinforcing bars protruding from one end face of the concrete slab and the joint reinforcing bars protruding from the other end face of the concrete slab are arranged alternately in a staggered pattern in the longitudinal direction of the joint portion, and the three side portions arranged on the imaginary base surface are arranged in the spaces between the alternately arranged joint reinforcing bars, and the diagonal connecting bars are arranged so as to intersect with the upper reinforcing bars, so that reinforcement can be arranged in the joint portion.

4. 4. A spiral reinforcing bar for a joint section as described in claim 3, wherein the three side portions arranged on the virtual base plane are arranged alternately in the spaces between the alternately arranged joint reinforcing bars.

5. 4. The spiral reinforcing bar for a joint portion according to claim 3, wherein the joint reinforcing bar is a loop reinforcing bar in which the end of the upper reinforcing bar and the end of the lower reinforcing bar are connected via an arc-shaped portion.

6. 3. A spiral reinforcing bar for a joint as claimed in claim 1 or 2, wherein the joint between a pair of adjacent concrete slabs is a joint between a pair of adjacently installed precast PC deck slabs.

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