Bar arrangement structure for joint part using spiral reinforcement

Abstract

To provide an arrangement structure for joint parts capable of smoothly arranging reinforcement bars in a joint part between concrete slabs, enlarging a scope to which the restraining effect of concrete extends, and avoiding damage to the joint part due to negative bending.SOLUTION: A bar arrangement structure of a joint part using spiral reinforcement extending between a pair of adjoining precast PC floor slabs in a direction crossing a main girder protruding from edge faces 20a of the precast PC floor slabs 20 on both sides is provided in a concrete placing space of the joint part 22 in a state where the cover thickness of a lower part of a lower reinforcement bar 21b is not invaded due to binding of the spiral reinforcement 10 to a joint reinforcement bar 21 by a binding wire 12 in a positional relationship where one horizontal side part 11c of each unit spiral reinforcement bar 11 constituting the spiral reinforcement 10 is arranged at the same height position as the lower reinforcement bar 21b of the joint reinforcement bar 21 protruding from an edge face 20a of the precast PC floor slabs 20 on both sides.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reinforcement structure of a joint section using spiral reinforcing bars, and in particular to a reinforcement structure of a joint section using spiral reinforcing bars that is provided in the concrete pouring space of a joint section extending in a direction intersecting the main girder in the section between each pair of adjacent precast PC deck slabs. [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 decks, which form the main body of the road, are supported by multiple girders installed at predetermined intervals in a direction perpendicular to the bridge axis direction, with their long sides preferably aligned perpendicularly to the girders. The precast PC decks are 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] Furthermore, concrete decks made up of multiple precast PC decks are susceptible to positive bending near the midpoint between the pier and the pier or abutment. For this reason, the joints between a pair of precast PC decks installed near the midpoint between the pier and the pier or abutment are at risk of damage due to tensile stress caused by bending, especially in the lower part.

[0010] The present invention aims to provide a reinforcement structure for a joint using spiral reinforcing bars that allows spiral reinforcing bars to be smoothly positioned and arranged at the joint between a pair of adjacent concrete slabs, preferably made of precast PC deck slabs, and that makes it possible to omit the linear connecting main bars that connect the joint reinforcing bars to each other by expanding the range over which the restraining effect of the concrete extends, and that ensures the bending strength and strength of the joint against positive bending, thereby preventing the joint from being damaged by positive bending. [Means for solving the problem]

[0011] The present invention provides a reinforcement structure for a joint using spiral reinforcing bars, which is provided in the concrete pouring space of a joint extending in a direction intersecting with the main girders in the portion between each pair of adjacent precast PC deck slabs, and which is made of a plurality of precast PC deck slabs that are supported by a plurality of main girders erected between a pair of abutments and attached in a continuous manner in the extension direction of the main girders. The spiral reinforcing bars are provided by bending a single reinforcing bar to form a spiral shape in which a plurality of unit spiral reinforcing bars, each having a rectangular frontal shape, are connected at a predetermined pitch in the axial direction of the spiral. Each of the continuous unit spiral reinforcing bars has a pair of vertical side portions and one horizontal side portion of the rectangular frontal shape 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 in top view relative to the imaginary base plane on which these three side portions are arranged, thereby forming a Z-spiral shape with a continuous Z shape in top view. The spiral reinforcing bars are provided in the concrete pouring space of the joint, and the spiral reinforcing bars are provided in the concrete pouring space of the joint, and the spiral reinforcing bars are provided in the spiral shape with a predetermined pitch in the axial direction of the spiral to form a spiral shape in which a pair of vertical side portions and one horizontal side portion of the rectangular frontal shape 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 in top view relative to the imaginary base plane on which these three side portions are arranged. The joint reinforcing bars protrude from the end faces of the concrete slabs on both sides of the concrete slab, and are arranged in two stages including upper 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 in a staggered pattern in the length direction of the joint part, and the three side parts of the spiral reinforcing bar arranged on the virtual base face are arranged in the spaces between the alternately arranged joint reinforcing bars, and the diagonal connecting bars are arranged in the spaces between the alternately arranged joint reinforcing bars. The above-mentioned object has been achieved by providing a reinforcement structure for a joint section using a spiral reinforcing bar that is installed in the concrete pouring space of the joint section without eroding the cover thickness below the lower reinforcing bar, by connecting the spiral reinforcing bar and the joint reinforcing bar in a positional relationship in which the spiral reinforcing bar is arranged so as to intersect with the upper reinforcing bar of the joint reinforcing bar and one horizontal edge portion of each unit spiral reinforcing bar that constitutes the spiral reinforcing bar is arranged at the same height position as the lower reinforcing bar of the joint reinforcing bar.

[0012] Furthermore, in the reinforcement structure of the joint section using the spiral reinforcing bars of the present invention, it is preferable that the upper reinforcing bars of the joint reinforcing bars are arranged at a position lower than the thickness of the diagonal connecting bars, and that the diagonal connecting bars are arranged so as to intersect above the upper reinforcing bars of the joint reinforcing bars.

[0013] In addition, it is preferable that the reinforcement structure of the joint section using the spiral reinforcing bar of the present invention has the virtual base surface be a surface perpendicular to the axial direction of the spiral, and that the upper reinforcing bar and the lower reinforcing bar of the joint reinforcing bar protrude in a direction perpendicular to the end face of the concrete slab when viewed from above.

[0014] Furthermore, it is preferable that the reinforcement structure of the joint section using the spiral reinforcement of the present invention is such that the three side portions arranged on the virtual base surface are arranged alternately in the spaces between the alternately arranged joint reinforcement bars.

[0015] Furthermore, in the reinforcement structure of the joint section using the spiral reinforcing bar of the present invention, it is preferable that 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.

[0016] In addition, in the reinforcement structure of the joint portion using the spiral reinforcing bar of the present invention, it is preferable that the spiral reinforcing bar and the joint reinforcing bar are connected by binding them with binding wire. [Effects of the Invention]

[0017] According to the reinforcement structure of the joint section using the spiral reinforcing bars of the present invention, the spiral reinforcing bars can be smoothly positioned and arranged at the joint section 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 linear connecting main bars that connect the joint reinforcing bars to each other, and by ensuring the bending strength and strength of the joint section against positive bending, it is possible to prevent the joint section from being damaged by positive bending. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view of a spiral reinforcing bar 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 of a joint using a spiral reinforcing bar 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] 1(a) to 1(c) are schematic plan views illustrating a state in which a spiral reinforcing bar is bound to a joint reinforcing bar in a joint reinforcement structure according to a preferred embodiment of the present invention. [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

[0019] A reinforcing bar structure 15 for a joint using a spiral reinforcing bar according to a preferred embodiment of the present invention is a reinforcing bar structure in which a spiral reinforcing bar 10, as shown in Fig. 1, is arranged in a joint extending in a direction intersecting the main girder in a portion between a pair of adjacent precast PC decks. For example, in the repair work of an existing road bridge, when an aging concrete deck is replaced with a precast PC deck 20, preferably made of precast concrete, the spiral reinforcing bar 10 shown in Fig. 1 is arranged in each of a plurality of joints 22 of the precast PC deck 20, which are installed in a continuous manner in the bridge axis direction as shown in Fig. 8, and is used as reinforcing bars for forming a reinforcing bar structure 15 for the joints 22 (see Figs. 4(a) to 4(c)) together with the joint reinforcing bar 21 protruding from the end face 20a of the precast PC deck 20, prior to pouring concrete into the joints 22. The joint reinforcement structure 15 using the spiral reinforcing bars 10 of this embodiment allows for smooth positioning and reinforcement at the joint 22 between a pair of adjacent precast PC deck slabs 20, and by expanding the range over which the concrete's restraining effect extends, it is possible to omit the straight connecting main reinforcements that connect the joint reinforcing bars 21 to each other, and by ensuring the bending strength and strength of the joint against positive bending, it is possible to prevent the joint from being damaged by positive bending.

[0020] The spiral reinforcing bar 10 used in the reinforcement structure 15 of the joint section using the spiral reinforcing bar of 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 precast PC deck slabs 20 installed adjacently, as shown in Figures 1 to 4, and is a spiral-shaped reinforcing bar that forms the reinforcement structure 15 at the joint section 22 together with the joint reinforcing bars 21 that each protrude from the end faces 20a of the precast PC deck slabs 20 on both sides facing each other in this pouring space. The spiral reinforcing bar 10 used in the reinforcement structure 15 of the joint section using the spiral reinforcing bar of this embodiment has a spiral shape in which a plurality of unit spiral reinforcing bars 11 having a rectangular front shape (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 shape, 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.

[0021] In addition, in this embodiment, the joint reinforcing bars 21 protruding from the end face 20a of each of the precast PC deck slabs 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 slab 20 and the joint reinforcing bars 21 protruding from the end face 20a of the other precast PC deck slab 20 are arranged alternately in a staggered pattern in the longitudinal direction X of the joint portion 22 (see Figure 7(a)).The three side portions 11a, 11b, and 11c arranged on the imaginary base surface P are arranged in the spaces between the alternately arranged joint reinforcing bars 21, and the diagonal connecting bars 11d of the other long side portion are arranged so as to intersect with the upper reinforcing bars 21a, so that the joint portion 22 can be arranged in a state where reinforcement is provided.

[0022] 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)).

[0023] In this embodiment, the spiral reinforcing bar 10 is a deformed reinforcing bar with a diameter of, for example, about 10 mm. A special reinforcing bar bending machine can easily be used to bend a single reinforcing bar into a spiral shape. As shown in FIGS. 1 and 2(a) and (b), the spiral reinforcing bar 10 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 slab 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 each unit spiral reinforcing bar 11 are arranged is preferably perpendicular to the spiral axial direction X.

[0024] 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.

[0025] When viewed from the front outside the spiral axial direction X, each unit spiral reinforcing bar 11 has a horizontally elongated rectangular frame shape with short side portions 11a and 11b (vertical side portions) on both the left and right sides (height) of approximately 121 mm and long side portions 11c and 11d (horizontal side portions) of approximately 230 mm, as shown in Figure 3. The four corners are curved so that the inner radius of curvature is approximately R25. The other long side portion, the upper long side portion 11d, acts as a diagonal connecting reinforcement and extends in a direction inclined at an angle θ of, for example, 15.2 degrees when viewed from above with respect to the imaginary base plane P on which the pair of short side portions 11a and 11b and one long side portion 11c are arranged (see Figure 2(a)), resulting in a length of approximately 238 mm when viewed from above.

[0026] If the spiral reinforcing bar 10 cannot be formed from a single reinforcing bar to a length equivalent to the extension of the joint portion 22, multiple spiral reinforcing bars 10 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 spiral axial direction X, thereby forming a spiral reinforcing bar 10 with a length equivalent to the extension of the joint portion 22.

[0027] On the other hand, in this embodiment, the joint rebars 21 are loop rebars in which the ends of the upper rebars 21a and the lower rebars 21b are connected via the arc-shaped portions 21c, as described above. The joint rebars 21 protruding from the end face 20a of one precast PC deck 20 and the joint rebars 21 protruding from the end face 20a of the other precast PC deck 20 are alternately arranged in a staggered pattern in the longitudinal direction X of the joint portion 22, which is the axial direction X of the spiral of the spiral rebar 10, as shown in FIG. 7(a). The upper rebars 21a and lower rebars 21b of these joint rebars 21, which are loop rebars, 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.

[0028] As shown in Figure 7(a), the spiral reinforcing bar 10 used in the reinforcement structure 15 of the joint section using the spiral reinforcing bar of this embodiment has three side portions 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, and the diagonal connecting bar of the other long side portion 11d is arranged so as to intersect with the upper reinforcing bar 21a of the joint reinforcing bar 21.In addition, one horizontal side portion 11c of each unit spiral reinforcing bar 11 that makes up the spiral reinforcing bar 10 is arranged at the same height position as the lower reinforcing bar 21b of the joint reinforcing bar 21, and is tied together using, for example, a binding wire 12, so that the reinforcement can be arranged in the joint section 22 without eroding the cover thickness below the lower reinforcing bar 21b. This makes it easy to form the reinforcement structure 15 of the joint section together with the joint reinforcing bars 21, preferably loop reinforcing bars, arranged alternately. Furthermore, as described above, one horizontal edge portion 11c of the unit spiral reinforcing bar 11 is arranged at the same height as the lower reinforcing bar 21b of the joint reinforcing bar 21 and does not encroach on the cover thickness below the lower reinforcing bar 21b. This allows the lower reinforcing bar 21b of the joint reinforcing bar 21, which has high tensile stiffness, to be arranged at the lowest possible height position that ensures a predetermined cover thickness. Therefore, the reinforcement structure of the joint section using the spiral reinforcing bar of this embodiment ensures the bending strength and strength of the joint section 22 against positive bending, which generates tensile stress on the downward side, and makes it possible to prevent the joint section 22 from being damaged by positive bending.

[0029] 5(b), the upper reinforcing bars 21a of the joint reinforcing bars 21 are arranged at a position lower by the thickness of the diagonal connecting bars 11d, and the diagonal connecting bars 11d are arranged so as to cross above the upper reinforcing bars 21a of the joint reinforcing bars 21. By arranging the upper reinforcing bars 21a at a position lower by the thickness of the diagonal connecting bars 11d, the lower reinforcing bars 21b of the joint reinforcing bars 21, which have high tensile stiffness, are also arranged at a position lower by the thickness of the diagonal connecting bars 11d. This makes it easier to ensure the bending strength and strength of the joint part 22 against positive bending, which generates tensile stress on the downward side, and makes it possible to effectively prevent the joint part 22 from being damaged by positive bending.

[0030] 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 each of the joint reinforcing bars 21 arranged on the imaginary base surface P of the spiral reinforcing bars 10 is arranged in a staggered pattern in the longitudinal direction X of the joint portion. The spiral reinforcing bar 10 is attached to the joint portion 22 in such a state that the three side portions 11a, 11b, and 11c of the unit spiral reinforcing bar 11 are arranged in the spaces between the alternately arranged joint reinforcing bars 21, and the diagonal connecting bar 11d is arranged so as to intersect with the upper reinforcing bar 21a of the joint reinforcing bar 21. When the attached spiral reinforcing bar 10 is projected from the outside in the axial direction X, the loop-shaped joint reinforcing bar 2 protruding from the end surface 20a of one of the precast PC deck slabs 20 is 5(b), the area where the spiral reinforcing bar 10 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 of the unit spiral reinforcing bars 11, and the attached spiral reinforcing bar 10 and the joint reinforcing bar 21 are connected by binding them preferably with binding wires 12 (see FIG. 7 (see FIG. 7)), and are installed in the concrete pouring space of the joint part 22. The connection between the spiral reinforcing bar 10 and the joint reinforcing bar 21 can be achieved by binding them with binding wires 12, as well as by various other connecting means such as clips and spacers.

[0031] As a result, the joint reinforcement structure 15 using spiral reinforcing bars of this embodiment allows for smooth positioning and reinforcement at the joint between a pair of adjacent precast PC deck slabs 20, making it easy to form the joint reinforcement structure 15 together with the joint reinforcement bars 21. Furthermore, by expanding the range of the concrete's restraint effect, it becomes possible to omit the linear connecting main reinforcements that connect the joint reinforcement bars 21 to each other. Furthermore, the joint reinforcement structure 15 using spiral reinforcing bars of this embodiment ensures the bending strength and strength of the joint 22 against positive bending, which generates tensile stress on the downward side, and prevents the joint 22 from being damaged by positive bending. This also effectively prevents the precast PC deck slab 20 from becoming thicker than necessary.

[0032] 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 unit spiral reinforcing bars 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 unit spiral reinforcing bars 11 of the spiral reinforcing bar 10.

[0033] In addition, in this embodiment, as shown in Figure 7(b), the spiral reinforcing bar 10 can be installed in the concrete pouring space of the joint portion 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, 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 with the three side portions 11a, 11b, and 11c arranged on the virtual base surface P in a state where they are close to or in contact with one of the joint reinforcing bars 21 on both sides of the gaps and biased to one side.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Furthermore, in this embodiment, the joint reinforcing bars that protrude from the end surface 20a of the precast PC deck 20 that constitutes the joint reinforcement structure 15 into the concrete pouring space of the joint 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 both the upper reinforcing bars and the lower reinforcing bars of the two-stage reinforcement arrangement may be straight reinforcing bars (not shown).

[0040] Furthermore, the joint section to which the spiral reinforcing bars 10 are attached and the joint section reinforcement structure 15 is provided does not necessarily have to be the joint section 22 between multiple precast PC deck slabs 20 installed in a row 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.

[0041] Therefore, in this embodiment, the reinforcement structure 15 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. 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 are arranged 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. The attached spiral reinforcing bars 10 and the joint reinforcing bars are tied together using tie wires 12, so that the spiral reinforcing bars can be installed in the concrete pouring space of the joint section.

[0042] The spiral reinforcing bars used in the reinforcement structure of the joint using the spiral reinforcing bars of the present invention are 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 left and right vertical sides and a pair of top and bottom horizontal sides, does not necessarily have to be a horizontally elongated frame shape with the vertical sides as short sides and the horizontal sides as long sides. For example, the horizontally elongated frame shape can include a horizontally elongated oval shape with the short sides curved in an arc. Even if the short sides are elongated in an oval shape, the same effects can be achieved. The inclination angle of the diagonal continuous reinforcing bars (diagonal connecting reinforcing bars), which preferably extend 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]

[0043] 10 Spiral Reinforcement Bars 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 reinforcement structure for joints using spiral reinforcing bars is provided in the concrete pouring space of joints extending in a direction intersecting the main girders in the portion between each pair of adjacent precast PC slabs, which are supported by a plurality of main girders erected between a pair of abutments and attached in a continuous manner in the extension direction of the main girders, The spiral rebar has a spiral shape in which a plurality of unit spiral rebars having a rectangular frontal shape are connected at a predetermined pitch in the axial direction of the spiral by bending a single rebar, and each of the continuous unit spiral rebars has a pair of left and right vertical side portions and one horizontal side portion of the rectangular frontal shape arranged on an imaginary base surface, and the other horizontal side portion is an oblique connecting bar extending in a direction inclined at 10 to 35 degrees when viewed from above relative to the imaginary base surface on which these three side portions are arranged, thereby having a Z-spiral shape with a continuous Z shape when viewed from above, The joint reinforcing bars protrude from the end faces of the concrete slabs on both sides facing each other in the concrete pouring space of the joint portion, and 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 in a staggered pattern alternately in the length direction of the joint portion, The three side portions of the spiral reinforcing bar arranged on the virtual base surface are arranged in the spaces between the alternatingly arranged joint reinforcing bars, and the diagonal connecting bar of the other horizontal side portion is arranged so as to intersect with the upper reinforcing bar of the joint reinforcing bar, and one horizontal side portion of each of the unit spiral reinforcing bars that make up the spiral reinforcing bar is arranged at the same height position as the lower reinforcing bar of the joint reinforcing bar, thereby connecting the spiral reinforcing bar and the joint reinforcing bar in a positional relationship such that the cover thickness below the lower reinforcing bar is not eroded.This is a reinforcement structure of a joint section using a spiral reinforcing bar that is arranged in the concrete pouring space of the joint section without eroding the cover thickness below the lower reinforcing bar.

2. 2. A reinforcement structure of a joint section using spiral reinforcing bars as described in claim 1, wherein the upper reinforcing bars of the joint reinforcing bars are arranged at a position lower than the thickness of the diagonal connecting bars, and the diagonal connecting bars are arranged so as to cross above the upper reinforcing bars of the joint reinforcing bars.

3. A reinforcement structure of a joint section using spiral reinforcement as described in claim 1 or 2, wherein the virtual base plane is a plane perpendicular to the axial direction of the spiral, and the upper reinforcement and the lower reinforcement of the joint reinforcement protrude in a direction perpendicular to the end face of the concrete slab when viewed from above.

4. A reinforcement structure of a joint section using spiral reinforcement as described in claim 1 or 2, wherein the three side portions arranged on the virtual base plane are arranged alternately in the spaces between the alternately arranged joint reinforcement bars.

5. A reinforcement structure of a joint section using spiral reinforcing bars as described in claim 1 or 2, wherein the joint reinforcing bars are loop reinforcing bars in which the ends of the upper reinforcing bars and the lower reinforcing bars are connected via an arc-shaped portion.

6. 3. A reinforcement structure for a joint using a spiral reinforcing bar according to claim 1 or 2, wherein the spiral reinforcing bar and the joint reinforcing bar are connected by binding them with a binding wire.

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