Method for removing an existing hollow floor board

Abstract

A method for removing an existing hollow floor slab supported from below by a lower structure, which can be safely removed without restricting the space below the existing hollow floor slab and can improve workability, is provided. 【Solution means】The method for removing an existing hollow floor slab according to the embodiment is a method for removing an existing hollow floor slab 1 supported by piers 8, and is a method for removing an existing hollow floor slab, which comprises attaching fixing brackets 21, 21 to the lower surfaces near each of the piers 8, 8 of the existing hollow floor slab 1 between a pair of piers 8, 8, attaching an outer cable 3 to the fixing brackets 21, 21, and a mounting step of tensioning the outer cable 3; a cutting step of cutting the existing hollow floor slab 1 in the bridge axis direction X after tensioning the outer cable 3 to form a first block 71 having the outer cable 3; and a removal step of removing the first block 71 by lifting devices 83, 84.

Description

Technical Field

[0001] The present invention relates to a method for removing an existing hollow floor slab supported at both ends in the bridge axis direction by a lower structure.

Background Art

[0002] There are many construction works to remove an aging bridge girder and update it to a new bridge girder. When removing a bridge girder, if there is sufficient space around, the entire existing bridge girder can be lifted and removed by a large crane. On the other hand, if there is not enough space around, a large crane cannot be installed, so the entire existing bridge girder cannot be lifted. Therefore, in some cases, the bridge girder is cut and removed so that it can be removed by a small crane.

[0003] In a conventional method of cutting and then removing an existing hollow floor slab supported at both ends in the bridge axis direction by piers, first, shoring for supporting the existing hollow floor slab to be removed from below is installed near both ends in the bridge axis direction and at the central part in the bridge axis direction. Then, the existing hollow floor slab is cut near the central part in the bridge axis direction so that the extension of the existing hollow floor slab in the bridge axis direction is about 6 to 7 m. Also, the existing hollow floor slab is cut so that the width in the direction orthogonal to the bridge axis is about 0.5 m to 1 m. In this way, the existing hollow floor slab is cut in the bridge axis direction and the direction orthogonal to the bridge axis to be divided into small blocks. Then, the divided small blocks are removed by a crane. Although the number of existing steel bars and the damage state of the members of the existing hollow floor slab to be removed are unknown, by dividing it into small blocks, the bending moment acting when lifted can also be reduced, so the existing hollow floor slab can be safely removed.

[0004] However, in the conventional method for removing an existing hollow floor slab, it may be difficult to install shoring in the central part in the bridge axis direction, such as when an intersecting road is installed below the existing hollow floor slab to be removed. When shoring cannot be installed in the central part, since cutting cannot be performed near the central part in the bridge axis direction, the span of the block of the existing hollow floor slab to be removed in the bridge axis direction becomes long. When a block with a long span in the bridge axis direction is lifted at both ends with a crane, a large bending moment acts on the central part of the divided block, and the displacement of the central part increases. Furthermore, although the strength of the existing hollow floor slab as a whole is ensured by steel bars arranged inside, there are some parts where the amount of reinforcement is small when divided into blocks, so ensuring safety when lifting the blocks is required. Also, in the conventional method for removing an existing hollow floor slab, there is a situation where it takes time to install the intermediate shoring in the central part.

[0005] As techniques for cutting and removing girders, for example, Patent Documents 1 and 2 are disclosed.

[0006] In the disclosed technique of Patent Document 1, in at least the girder part near the pier, a drilling step of drilling driving openings communicating with the hollow part, a support part forming step of forming a support part for supporting PC steel wires to be installable in the hollow part by driving concrete from the driving openings, a tension applying step of applying tension to the girder part between a pair of support parts by tensioning the PC steel wires and maintaining the tension state, a cutting step of cutting the girder part between the support part and the pier in a state where both end sides of the girder part are supported from below, and a carrying out step of carrying out the cut girder part are included.

[0007] However, in the disclosed technique of Patent Document 1, since PC steel wires are arranged in the hollow part, the construction takes time. Also, in the disclosed technique of Patent Document 1, it only cuts along the direction orthogonal to the bridge axis, and does not cut the girder to be removed along the bridge axis direction. For this reason, the width of the girder to be removed in the direction orthogonal to the bridge axis is wide, and a large space for installing a large crane is required for removal.

[0008] In the disclosed technology of Patent Document 2, in an indeterminate concrete structure made of PC concrete such as continuous digits, additional tensile force is introduced to the upper part of the structure near the point where the bending moment changes from (+) to (-), and then it is cut near the support point of the structure.

[0009] However, in the disclosed technology of Patent Document 2, since it is necessary to grasp in advance the point where the bending moment changes from (+) to (-), it takes time to select the installation location.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] Therefore, the present invention has been devised in view of the above-described problems, and an object thereof is to provide a method for removing an existing hollow floor slab supported from below by a lower structure, which can be safely removed without restricting the space below the existing hollow floor slab and can improve workability.

Means for Solving the Problems

[0012] The method for removing an existing hollow floor slab according to the present invention is a method for removing an existing hollow floor slab supported by a substructure, the method comprising: an attachment step of attaching an extension member extending in the bridge axis direction from the vicinity of one substructure to the vicinity of the other substructure to at least one of the upper surface and the lower surface of the existing hollow floor slab between the pair of substructures; a cutting step of cutting the existing hollow floor slab to form a block having the extension member; and a removal step of removing the block by a hoisting device.

Advantages of the Invention

[0013] According to the present invention, there are provided an attachment step of attaching an extension member to at least one of the upper surface and the lower surface of the existing hollow floor slab, and a cutting step of cutting the existing hollow floor slab to form a block having the extension member. Thereby, the resistance of the block to bending can be improved. Therefore, when the block is removed by a hoisting device in the removal step, it is possible to resist the downwardly convex bending moment acting on the central portion of the block. As a result, breakage of the existing hollow floor slab can be suppressed and it can be safely removed.

[0014] According to the present invention, there is provided a cutting step of cutting the existing hollow floor slab to form a block having the extension member. Thereby, since the central portion in the bridge axis direction of the existing hollow floor slab is not cut as in the prior art, the intermediate shoring work in the central portion in the bridge axis direction, which was necessary in the prior art, becomes unnecessary. Therefore, even when there is an intersecting road or the like below the existing hollow floor slab, it can be safely removed without restricting the space below the existing hollow floor slab. Further, since the intermediate shoring work in the central portion becomes unnecessary, the workability can be improved.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0016] Hereinafter, a method for removing an existing hollow floor slab according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0017] As shown in Fig. 1, the bridge 100 includes a pair of bridge piers 8 which are substructures, and an existing hollow floor slab 1 supported by the pair of bridge piers 8. The existing hollow floor slab 1 is a continuous girder supported by a bearing (not shown) installed on the bridge pier 8. A crossroad (not shown) is provided below the existing hollow floor slab 1.

[0018] As shown in Fig. 2, the existing hollow floor slab 1 is made of concrete and has a hollow portion 13. The existing hollow floor slab 1 has a main girder portion 11 disposed at the center in the direction Y perpendicular to the bridge axis, and a pair of overhanging portions

[0019] The main girder part 11 has a plurality of cylindrical hollow parts 13 extending in the bridge axis direction X. The hollow parts 13 are arranged side by side in the direction Y orthogonal to the bridge axis. The main girder part 11 has one side surface 11a and the other side surface 11b. The main girder part 11 has a solid connecting part 14 connected to the overhanging part 12 outside the hollow part 13 at the end in the direction Y orthogonal to the bridge axis.

[0020] Next, the method for removing the existing hollow floor slab 1 in this embodiment will be described.

[0021] The method for removing the existing hollow floor slab 1 includes an attachment step, a cutting step, and a removal step.

[0022] <Attachment step> As shown in Fig. 3(a), in the attachment step, fixing brackets 21 are attached to the lower surfaces on both end sides in the bridge axis direction X of the existing hollow floor slab 1. In the attachment step, deflection brackets 22 are attached to the lower surface of the existing hollow floor slab 1 between the pair of fixing brackets 21, 21. The fixing bracket 21 is for fixing the outer cable 3 as an extension member to the existing hollow floor slab 1 and applying a tension force to the existing hollow floor slab 1. The deflection bracket 22 is for deflecting the outer cable 3.

[0023] Specifically, as shown in Figs. 4(a), 4(b), 5(a) and 5(b), in the attachment step, a first through hole 15 penetrating from the upper surface to the lower surface of one overhanging part 12a of the existing hollow floor slab 1 is drilled, and the fixing bracket 21 and the deflection bracket 22 are attached to the lower surface of the overhanging part 12 of the existing hollow floor slab 1 by the first PC steel bar 23 arranged in the first through hole 15.

[0024] The fixing bracket 21 is composed of a mounting plate 21a along the lower surface of the overhanging part 12, a supporting pressure plate 21b erected with respect to the mounting plate 21a, etc. The first PC steel bar 23 is attached to the mounting plate 21a. The outer cable 3 is attached to the supporting pressure plate 21b. Anchor plates, washers, nuts, etc. are provided on the first PC steel bar 23.

[0025] The deflection part bracket 22 is composed of a mounting plate 22a along the lower surface of the overhanging part 12, a deflection part 22b attached to the mounting plate 22a, and the like. A first PC steel bar 23 is attached to the mounting plate 22a. The deflection part 22b deflects the outer cable 3.

[0026] The fixing part bracket 21 and the deflection part bracket 22 are attached to the overhanging part 12a by applying a tension force of, for example, about 10 kN to 560 kN to the first PC steel bar 23. For the first PC steel bar 23 used for attaching the fixing part bracket 21, for example, a PC deformed bar steel of D36 is used. For the first PC steel bar 23 used for attaching the deflection part bracket 22, for example, a PC deformed bar steel of D25 is used.

[0027] Then, in the mounting process, the outer cable 3 is attached to the fixing part bracket 21 and the deflection part bracket 22 attached to the lower surface of the overhanging part 12 of the existing hollow floor slab 1. The outer cable 3 is, for example, made of a PC deformed steel bar and extends in the bridge axis direction X. The outer cable 3 is, for example, a PC deformed bar steel of D22. The deflection part bracket 22 is arranged between the fixing part brackets 21, 21. As shown in Fig. 7(a), the outer cable 3 as an extension member extends in the bridge axis direction X from near one pier 8 to near the other pier 8 on the lower surface of the overhanging part 12 of the existing hollow floor slab 1 between a pair of piers 8, 8. That is, the extension member extends from one end to the other end in the bridge axis direction of the existing hollow floor slab 1 to be removed.

[0028] In the mounting process, the outer cable 3 to which the fixing part bracket 21 and the deflection part bracket 22 are attached is tensioned. A tension force of, for example, about 150 kN to 190 kN is applied to the outer cable 3.

[0029] Also, as shown in FIGS. 3(b), 5(a), and 5(b), in the attachment step, a second through-hole 16 penetrating from the upper surface to the lower surface of the main girder portion 11 is drilled, and a first reinforcing member 25 extending in the bridge axis direction X on the upper surface of the main girder portion 11 and a second reinforcing member 26 having a lower rigidity than the first reinforcing member 25 extending in the bridge axis direction X on the lower surface of the main girder portion 11 are attached by the second PC steel bar 24 disposed in the second through-hole 16. As shown in FIG. 7(b), the first reinforcing member 25 and the second reinforcing member 26 as extension members extend in the bridge axis direction X from near one pier 8 to near the other pier 8 on the upper surface and the lower surface of the main girder portion 11 of the existing hollow floor slab 1 between the pair of piers 8, 8.

[0030] The first reinforcing member 25 and the second reinforcing member 26 are made of, for example, channel steel. The first reinforcing member 25 and the second reinforcing member 26 are attached to the main girder portion 11 by applying a tensile force of about 20.5 kN to the second PC steel bar 24, for example. The first reinforcing members 25 are arranged in a pair with the second PC steel bar 24 interposed therebetween in the direction Y orthogonal to the bridge axis. The pair of first reinforcing members 25 are joined to each other by a steel plate. The second reinforcing members 26 are arranged in a pair with the second PC steel bar 24 interposed therebetween in the direction Y orthogonal to the bridge axis. The pair of second reinforcing members 26 are joined to each other by a steel plate.

[0031] The first reinforcing member 25 is disposed on the upper surface of the main girder portion 11 above the hollow portion 13. The second reinforcing member 26 is disposed on the lower surface of the main girder portion 11 below the hollow portion 13.

[0032] Also, as shown in Fig. 3(b), in the mounting process, reinforcing bodies 27 made of non-shrinking mortar may be provided on both end sides in the bridge axis direction X of the hollow portion 13 of the main girder portion 11. The reinforcing body 27 may be a pipe support. It is preferable to mount the reinforcing body 27 before mounting the first reinforcing member 25 and the second reinforcing member 26. By providing the reinforcing body 27, the main girder portion 11 including the hollow portion 13 can be reinforced. For this reason, for example, when a tensile force is applied to the second PC steel bar 24 when the first reinforcing member 25 and the second reinforcing member 26 are mounted, or when the main girder portion 11 is cut to form a second block 74 including the hollow portion 13 described later, the destruction of the second block 74 can be prevented and the cross-sectional shape of the second block 74 can be maintained.

[0033] As shown in Figs. 7(a) and 7(b), in the mounting process, lifting pieces 7 for lifting with a hoisting device are mounted on the upper surface side of the main girder portion 11 and the upper surface side of the overhanging portion 12. The lifting piece 7 mounted on the main girder portion 11 is mounted on, for example, the second PC steel bar 24. The lifting piece 7 mounted on the overhanging portion 12 is mounted on, for example, the first PC steel bar 23.

[0034] As shown in Fig. 5, in the mounting process, a lifting piece (not shown) is also mounted on the upper surface of the connecting portion 14.

[0035] As shown in Figs. 3(a), 3(b), 5(a), 5(b) and Fig. 6, cutting positions 61 to 65 for forming the first blocks 71, 72 and the second blocks 73, 74 described later are set on the respective existing hollow floor slabs 1 of the lower line 18 and the upper line 19. The pair of cutting positions 61 extend in the direction Y orthogonal to the bridge axis. The cutting positions 62 to 65 are connected to the pair of cutting positions 61 and extend in the bridge axis direction X.

[0036] As shown in FIGS. 3(a), 3(b), 5(a), 5(b) and 6, the cutting position 61 is set on the support side in the bridge axis direction X rather than the fixing part bracket 21. The cutting position 62 is set on the main girder part 11. The cutting position 63 is set on the overhanging part 12. The cutting position 63 is separated from the connecting part 14. The cutting position 64 is set at the boundary between the overhanging part 12 and the connecting part 14 along one side surface 11a of the main girder part 11. The cutting position 65 is set on the main girder part 11.

[0037] Thus, in the mounting step, on the upper surface of the main girder part 11, the lower surface of the main girder part 11, and the lower surface of the overhanging part 12 of the existing hollow floor slab 1 between the pair of piers 8, 8, a stretching member extending in the bridge axis direction X from near one pier 8 to near the other pier 8 is mounted. Note that in the mounting step of the present invention, a stretching member extending in the bridge axis direction X from near one pier 8 to near the other pier 8 may be mounted on at least one of the upper surface and the lower surface of the existing hollow floor slab 1 between the pair of piers 8, 8.

[0038] <Cutting Step> In the cutting step, after tensioning the outer cable 3, the existing hollow floor slab 1 is cut in the bridge axis direction X to form the first blocks 71, 72 having the outer cable 3.

[0039] Specifically, as shown in FIGS. 3(a), 3(b) and 6, in the cutting step, first, cutting is performed along a pair of cutting positions 61 which are set on the support side in the bridge axis direction X rather than the fixing part bracket 21 of the existing hollow floor slab 1 and extend along the bridge axis orthogonal direction Y. The cutting position 61 extends in the bridge axis orthogonal direction Y across the overhanging part 12 (12a) and the main girder part 11. Also, in the cutting step, cutting is performed along a cutting position 62 which is set on the main girder part 11 of the existing hollow floor slab 1 and extends along the bridge axis direction X. The cutting position 62 is connected to the pair of cutting positions 61. Thereby, in the existing hollow floor slab 1, the first region 1a surrounded by the cutting position 61 and the cutting position 62 can be separated.

[0040] As shown in FIGS. 7(a) and 7(b), the separated first region 1a is supported from below by a pair of end support members 81 and 82 that were installed in advance before separation. The pair of end support members 81 and 82 are arranged between the piers 8 and 8 that support both ends of the existing hollow floor slab 1 in the bridge axis direction X. The pair of end support members 81 and 82 support both ends of the first region 1a in the bridge axis direction X. The end support members 81 and 82 may be installed below the existing hollow floor slab 1 before cutting the existing hollow floor slab 1. The end support members 81 and 82 may be installed, for example, in the installation process or in the cutting process.

[0041] Then, as shown in FIGS. 3(a), 3(b) and 6, in the cutting process, cutting is performed along the cutting positions 63 and 64 that connect to the pair of cutting positions 61 and extend in the bridge axis direction X, and the first blocks 71 and 72 composed of the overhanging portions 12 are formed. The first blocks 71 and 72 include the central portion of the first region 1a of the existing hollow floor slab 1 in the bridge axis direction X. The length of the first blocks 71 and 72 in the bridge axis direction X is, for example, about 13.5 m. The width of the first blocks 71 and 72 in the direction Y orthogonal to the bridge axis is, for example, about 0.5 to 1 m.

[0042] The lower surfaces of the first block 71 and the first block 72 each have the outer cable 3. Here, when the existing hollow floor slab 1 is cut, the tension acting on the first blocks 71 and 72 by the outer cable 3 may vary. Therefore, in the cutting process, after forming the first blocks 71 and 72, the outer cables 3 of the first blocks 71 and 72 may be tensioned again with a predetermined tension. Thereby, even when the tension acting on the first blocks 71 and 72 varies due to the cutting of the existing hollow floor slab 1, an appropriate tension can be applied in the removal process.

[0043] Also, in the cutting process, cutting is performed along a cutting position 65 that leads to a pair of cutting positions 61 and extends in the bridge axis direction X, forming second blocks 73 and 74 composed of the main girder portion 11. The second block 73 does not include the hollow portion 13 and is composed of the connecting portion 14. The second block 74 includes the hollow portion 13. A first reinforcing member 25 is attached to the upper surface of the second block 74. A second reinforcing member 26 is attached to the lower surface of the second block 74. The second blocks 73 and 74 include the central portion in the bridge axis direction X of the first region 1a of the existing hollow floor slab 1, and the length of the second blocks 73 and 74 in the bridge axis direction X is, for example, about 13.5 m. The width of the second blocks 73 and 74 in the direction Y orthogonal to the bridge axis is, for example, about 0.5 to 1 m. In the cutting process of the present invention, a plurality of second blocks having the first reinforcing member 25 and the second reinforcing member 26 may be formed. In this case, in the removal process of the present invention, the plurality of second blocks may be removed sequentially.

[0044] Thus, in the cutting process, the existing hollow floor slab 1 is cut to form a plurality of blocks having extension members.

[0045] <Removal process> As shown in Fig. 7(a), in the removal process, the formed first block 71 is lifted and removed by lifting devices 83 and 84. The lifting devices 83 and 84 are, for example, cranes of about 70 t that cannot lift the entire existing hollow floor slab 1 alone. The lifting devices 83 and 84 are respectively arranged on the existing hollow floor slabs 1 on both sides in the bridge axis direction X with the first region 1a to be removed sandwiched therebetween. When removing the first block 71, the lifting piece 7 at one end of the first block 71 in the bridge axis direction X is lifted by one of the lifting devices 83, and the lifting piece 7 at the other end of the first block 71 in the bridge axis direction X is lifted by one of the lifting devices 84. In this way, the first block 71 is removed by being lifted by the lifting devices 83 and 84 in a counterbalanced manner.

[0046] Since the first block 71 is under tension by the outer cable 3 and a convex upward bending moment is acting on it, when removing the first block 71 by the lifting devices 83 and 84 in the removal process, the convex downward bending moment acting on the central portion of the first block 71 can be reduced. As a result, damage to the central portion of the first block 71 can be suppressed and it can be safely removed.

[0047] In the removal process, similarly for the formed first block 72, it is lifted and removed by the lifting devices 83 and 84.

[0048] In the removal process, similarly for the formed second block 73, it is lifted and removed by the lifting devices 83 and 84.

[0049] As shown in FIG. 7(b), in the removal process, the formed second block 74 is lifted and removed by a lifting device 83, 84 such as a crane.

[0050] Since the second block 74 is reinforced by the first reinforcing member 25 and the second reinforcing member 26, when removing the second block 74 by the lifting devices 83 and 84 in the removal process, the convex downward bending moment acting on the central portion of the second block 74 can be reduced. As a result, damage to the central portion of the second block 74 can be suppressed and it can be safely removed.

[0051] In this way, in the removal process, the blocks are removed by the lifting devices 83 and 84.

[0052] As described above, the removal of the first region 1a including one overhanging portion 12a at the underline 18 is completed.

[0053] As shown in FIG. 8, the first region 1a including the other overhanging portion 12b at the overline 19 is removed by the same procedure. And for other regions of the existing hollow floor slab 1 other than the first region 1a, they may be cut to a predetermined size and then removed by a lifting device.

[0054] The method for removing the existing hollow floor slab 1 is thus completed. Before removing the existing hollow floor slab 1, a displacement meter may be installed in advance on the existing hollow floor slab 1, and the removal method of the existing hollow floor slab 1 may be carried out while measuring the displacement. By removing while measuring the displacement, the existing hollow floor slab 1 can be removed more safely.

[0055] According to this embodiment, an attachment step of attaching an extension member extending in the bridge axis direction X from near one pier 8 to near the other pier 8 to at least one of the upper surface and the lower surface of the existing hollow floor slab 1, and a cutting step of cutting the existing hollow floor slab 1 to form a block having the extension member are provided. Thereby, the resistance of the block against bending can be improved. For this reason, when removing the block by the lifting devices 83 and 84 in the removal step, it is possible to resist the downward convex bending moment acting on the central portion of the block. As a result, breakage of the block of the existing hollow floor slab 1 can be suppressed and it can be removed safely.

[0056] Further, according to this embodiment, since the central portion of the existing hollow floor slab 1 in the bridge axis direction X is not cut, the intermediate shoring work at the central portion in the bridge axis direction, which was necessary in the past, becomes unnecessary. For this reason, even when there is an intersecting road or the like below the existing hollow floor slab, it can be removed safely without restricting the space below the existing hollow floor slab. Also, since the intermediate shoring work at the central portion becomes unnecessary, the workability can be improved.

[0057] According to this embodiment, a fixing part bracket 21 is attached to the lower surface of the overhanging part 12 of the existing hollow floor slab 1, an outer cable 3 is attached to the fixing part bracket 21, and an attachment step of tensioning the outer cable 3, and after tensioning the outer cable 3, a cutting step of cutting the existing hollow floor slab 1 to form first blocks 71 and 72 having the outer cable 3 are provided. Thereby, an upward convex bending moment can be made to act on the first blocks 71 and 72 at the central portion in the bridge axis direction X. For this reason, when removing the first blocks 71 and 72 by the lifting devices 83 and 84 in the removal step, it is possible to resist the downward convex bending moment acting on the central portion of the first blocks 71 and 72. As a result, breakage of the first blocks 71 and 72 of the existing hollow floor slab 1 can be suppressed and it can be removed safely.

[0058] According to this embodiment, after tensioning the outer cable 3, a cutting step is provided of cutting the existing hollow floor slab 1 to form the first blocks 71, 72 having the outer cable 3. Since the central portion of the existing hollow floor slab 1 in the bridge axis direction X is not cut, the intermediate support work in the central portion in the bridge axis direction, which was necessary in the prior art, becomes unnecessary. Therefore, even when there is an intersecting road or the like below the existing hollow floor slab, it can be safely removed without restricting the space below the existing hollow floor slab. Also, since the intermediate support work in the central portion becomes unnecessary, the workability can be improved.

[0059] According to this embodiment, an attachment step is provided of attaching the fixing portion bracket 21 to the lower surface of the overhanging portion 12 of the existing hollow floor slab 1 and attaching the outer cable 3 to the fixing portion bracket 21. Since a tension member is not installed in the hollow portion as in the prior art, the attachment of the outer cable 3 becomes easy. Therefore, the workability can be improved.

[0060] According to this embodiment, in the attachment step, a first through hole 15 penetrating from the upper surface to the lower surface of the existing hollow floor slab 1 is drilled, and the fixing portion bracket 21 is attached to the lower surface of the existing hollow floor slab 1 by the first PC steel bar 23 disposed in the first through hole 15. Thereby, the fixing portion bracket 21 can be attached to the lower surface of the existing hollow floor slab 1 without placing concrete. Therefore, the workability can be further improved.

[0061] According to this embodiment, the existing hollow floor slab 1 has a main girder portion 11 and an overhanging portion 12 formed by protruding from the end portion of the main girder portion 11 in the direction Y orthogonal to the bridge axis and having a thickness thinner than that of the main girder portion 11. In the attachment step, the fixing portion bracket 21 is attached to the lower surface of the overhanging portion 12, and in the cutting step, the overhanging portion 12 is cut in the bridge axis direction X to form the first blocks 71, 72. Thereby, the tension of the outer cable 3 can be applied to the first blocks 71, 72 having a thin thickness that is difficult to resist the bending moment. Therefore, breakage of the first blocks 71, 72 of the existing hollow floor slab 1 can be effectively suppressed and it can be safely removed.

[0062] According to this embodiment, in the attachment step, a second through hole 16 penetrating from the upper surface to the lower surface of the main girder portion 11 is drilled, and a first reinforcing member 25 extending in the bridge axis direction X on the upper surface of the main girder portion 11 and a second reinforcing member 26 having a lower rigidity than the first reinforcing member 25 extending in the bridge axis direction X on the lower surface of the main girder portion 11 are attached by the second PC steel bar 24 disposed in the second through hole 16. Since the second block 74 is reinforced by the first reinforcing member 25 and the second reinforcing member 26, when the second block 74 is removed by the lifting devices 83 and 84 in the removal step, it can resist the downward convex bending moment acting on the central portion of the second block 74. As a result, breakage of the central portion of the second block 74 of the existing hollow floor slab 1 can be suppressed, and it can be safely removed.

[0063] According to this embodiment, the first reinforcing member 25 and the second reinforcing member 26 are attached to the second block 74 including the hollow portion 13. Thereby, the second block 74 including the hollow portion 13 that is difficult to resist the bending moment can be reinforced by the first reinforcing member 25 and the second reinforcing member 26. For this reason, breakage of the second block 74 of the existing hollow floor slab 1 can be effectively suppressed, and it can be safely removed.

[0064] In addition, since the relatively large first reinforcing member 25 is attached to the upper surface side of the existing hollow floor slab 1 that is easy to work on, and the small second reinforcing member 26 is attached to the lower surface side of the existing hollow floor slab 1 that is difficult to work on, the first reinforcing member 25 and the second reinforcing member 26 can be efficiently attached.

[0065] The embodiments of the present invention have been described above, but these embodiments are presented as examples and are not intended to limit the scope of the invention. Furthermore, the present invention can be implemented in various novel forms in addition to the above embodiments. Therefore, the above embodiments can be variously omitted, replaced, and changed without departing from the gist of the present invention. Such novel forms and modifications are included in the scope and gist of the present invention, and are also included in the scope of the invention described in the claims and the scope of equivalents of the invention described in the claims.

Explanation of Reference Numerals

[0066] 1: Existing hollow floor slab 11: Main girder part 12: Protruding part 13: Hollow part 14: Connecting part 15: First through hole 16: Second through hole 21: Fixing bracket 22: Deflection part bracket 23: First PC steel bar 24: Second PC steel bar 25: First reinforcing member 26: Second reinforcing member 3: Outer cable 71: First block 72: First block 73: Second block 74: Second block 8: Bridge pier 81: End support structure 82: End support structure

Claims

1. A method for removing an existing hollow floor slab supported by a lower structure, comprising: an attachment step of attaching an extension member extending in the bridge axis direction from near one of the lower structures to near the other of the lower structures to at least one of the upper and lower surfaces of the existing hollow floor slab between the pair of lower structures; a cutting step of cutting the existing hollow floor slab to form a block having the extension member; a removal step of removing the block by a lifting device. A method for removing an existing hollow floor slab, characterized by the above.

2. The existing hollow floor slab has a main girder portion and a projecting portion that projects from an end portion of the main girder portion in a direction orthogonal to the bridge axis and has a thickness thinner than that of the main girder portion. In the attachment step, a fixing portion bracket is attached to the lower surface of the projecting portion, an outer cable extending in the bridge axis direction is attached to the fixing portion bracket, and the outer cable is tensioned. In the cutting step, after tensioning the outer cable, the existing hollow floor slab is cut to form a first block having the outer cable. In the removal step, the first block is removed. A method for removing an existing hollow floor slab according to claim 1, characterized by the above.

3. In the attachment step, a first through hole penetrating from the upper surface to the lower surface of the projecting portion is drilled, and the fixing portion bracket is attached to the lower surface of the projecting portion by a first PC steel bar disposed in the first through hole. A method for removing an existing hollow floor slab according to claim 2, characterized by the above.

4. In the cutting step, after forming the first block, the outer cable in the formed first block is tensioned again. A method for removing an existing hollow floor slab according to claim 2, characterized by the above.

5. In the cutting step, a plurality of the first blocks are formed. In the removal step, the plurality of first blocks are sequentially removed. A method for removing an existing hollow floor slab according to claim 2, characterized by the above.

6. The existing hollow floor slab has a main girder portion and a projecting portion that projects from an end portion of the main girder portion in a direction orthogonal to the bridge axis and has a thickness thinner than that of the main girder portion. In the attachment step, a first reinforcing member extending in the bridge axis direction is attached to the upper surface of the main girder portion, and a second reinforcing member having a lower rigidity than the first reinforcing member extending in the bridge axis direction is attached to the lower surface of the main girder portion. In the cutting step, the main girder portion is cut to form a second block having the first reinforcing member and the second reinforcing member. In the removal step, removing the second block The method for removing an existing hollow floor slab according to claim 1, characterized by the above.

7. In the attachment step, drilling a second through hole that penetrates from the upper surface to the lower surface of the main girder portion, and attaching the first reinforcing member and the second reinforcing member with a second PC steel bar disposed in the second through hole The method for removing an existing hollow floor slab according to claim 6, characterized by the above.

8. In the cutting step, forming a plurality of the second blocks In the removal step, sequentially removing the plurality of second blocks The method for removing an existing hollow floor slab according to claim 6, characterized by the above.

9. In the attachment step, attaching a reinforcing body to both ends in the bridge axis direction of the hollow portion of the main girder portion In the cutting step, cutting the main girder portion to form a second block having the first reinforcing member, the second reinforcing member, and the reinforcing body The method for removing an existing hollow floor slab according to claim 6, characterized by the above.

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