How to remove an existing hollow deck
By attaching extension members and cutting the deck to form blocks, the method safely removes hollow deck slabs with reduced bending moments and improved workability, even in confined spaces.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2026-03-12
AI Technical Summary
Conventional methods for removing hollow deck slabs supported by a substructure face challenges when space is restricted, particularly when intersecting roads are present, leading to increased bending moments and the need for intermediate supports, which complicates the removal process and reduces workability.
The method involves attaching extension members to the upper and lower surfaces of the hollow deck between substructures, cutting the deck to form blocks with these members, and using lifting devices to remove the blocks, thereby enhancing resistance to bending moments and eliminating the need for intermediate supports.
This approach allows safe removal of hollow deck slabs without restricting space below, reduces damage, and improves workability by minimizing bending moments and eliminating the need for intermediate supports.
Smart Images
Figure 2026044396000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a method for removing an existing hollow deck slab, the ends of which in the bridge axis direction are supported by a substructure. [Background technology]
[0002] Many bridge construction projects involve removing old bridge girders and replacing them with new ones. When removing a bridge girder, if there is sufficient space around it, it is possible to lift and remove the entire existing bridge girder using a large crane. On the other hand, if there is not enough space around it, it is not possible to install a large crane, and therefore it is not possible to lift the entire existing bridge girder. For this reason, the bridge girder may be cut and removed so that it can be removed with a small crane.
[0003] In the conventional method of cutting and removing an existing hollow deck, both ends of which are supported by piers in the bridge axis direction, shoring is first installed near both ends of the bridge axis direction and at the center in the bridge axis direction to support the existing hollow deck from below. The existing hollow deck is then cut near the center in the bridge axis direction so that its extension in the bridge axis direction is approximately 6 to 7 m. It is also cut so that its width in the direction perpendicular to the bridge axis is approximately 0.5 to 1 m. By cutting in this way in the bridge axis direction and the direction perpendicular to the bridge axis, the existing hollow deck is divided into small blocks. The divided small blocks are then removed by crane. Although the number of existing rebars and the state of damage to the components of the existing hollow deck to be removed are unknown, dividing it into small blocks reduces the bending moment acting when lifting it, allowing the existing hollow deck to be safely removed.
[0004] However, with conventional methods for removing existing hollow slabs, it can be difficult to install shoring in the center of the bridge axis, for example, when an intersecting road is located below the existing hollow slab to be removed. If shoring cannot be installed in the center, cutting near the center of the bridge axis is not possible, resulting in a longer span in the bridge axis direction of the existing hollow slab block to be removed. When a block with a long span in the bridge axis direction is lifted by a crane at both ends, a large bending moment acts on the center of the divided block, resulting in significant displacement in the center. Furthermore, while the overall strength of the existing hollow slab is ensured by reinforcing bars and other materials placed inside, when the block is divided, some areas have less reinforcement, making it necessary to ensure safety when lifting the block. Furthermore, with conventional methods for removing existing hollow slabs, installing intermediate shoring in the center takes time.
[0005] Techniques for cutting and removing girders are disclosed in, for example, Patent Documents 1 and 2.
[0006] The technology disclosed in Patent Document 1 includes a drilling process in which, in at least each bridge girder portion near the pier, a casting opening that communicates with the hollow portion is drilled; a support portion forming process in which concrete is poured through the casting opening to form a support portion that supports the PC steel wire so that it can be installed within the hollow portion; a tensioning process in which tension is applied to the bridge girder portion between a pair of support portions by tensioning the PC steel wire and maintaining the tensioned state; a cutting process in which, while supporting both end sides of the bridge girder portion from below, the bridge girder portion is cut between the support portions and the pier; and a removal process in which the cut bridge girder portion is removed.
[0007] However, the technology disclosed in Patent Document 1 requires the placement of PC steel wires within the hollow space, which takes time to install. Furthermore, the technology disclosed in Patent Document 1 only cuts the bridge girders along the direction perpendicular to the bridge axis, and does not cut the bridge girders to be removed along the bridge axis. As a result, the width of the bridge girders to be removed in the direction perpendicular to the bridge axis is large, and a large space is required to install a large crane during removal.
[0008] In the technology disclosed in Patent Document 2, in a statically indeterminate concrete structure made of PC concrete such as a continuous girder, additional tension is introduced to the upper part of the structure near the point where the bending moment changes from (+) to (-), and then the structure is cut near the support point.
[0009] However, with the technology disclosed in Patent Document 2, it is necessary to know in advance the point at which the bending moment changes from (+) to (-), and therefore it takes time to select the installation location. [Prior art documents] [Patent documents]
[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-131919 [Patent Document 2] Japanese Patent Application Publication No. 197510 / 1983 Summary of the Invention [Problem to be solved by the invention]
[0011] Therefore, the present invention was devised in consideration of the above-mentioned problems, and its purpose is to provide a method for removing an existing hollow deck that is supported from below by a substructure, which can be safely removed without restricting the space below the existing hollow deck and which improves workability. [Means for solving the problem]
[0012] The method for removing an existing hollow deck according to the present invention is a method for removing an existing hollow deck supported by a substructure, and is characterized by comprising an attachment process for attaching an extension member extending in the bridge axis direction from near one of the substructures to near the other substructure on at least one of the upper and lower surfaces of the existing hollow deck between a pair of the substructures, a cutting process for cutting the existing hollow deck to form a block having the extension member, and a removal process for removing the block using a lifting device. [Effects of the Invention]
[0013] According to the present invention, the method includes an attachment process for attaching extension members to at least one of the upper and lower surfaces of an existing hollow deck, and a cutting process for cutting the existing hollow deck to form a block having an extension member. This improves the block's resistance to bending. Therefore, when the block is removed by a lifting device in the removal process, it can resist a downward bending moment acting on the center of the block. As a result, damage to the existing hollow deck can be suppressed, allowing it to be removed safely.
[0014] According to the present invention, the method further comprises a cutting process of cutting the existing hollow deck to form a block having an extension member. This eliminates the need for intermediate support in the center of the bridge axis direction of the existing hollow deck, as was conventionally the case, eliminating the need for intermediate support in the center of the bridge axis direction, as was conventionally required. Therefore, even if there is an intersecting road or the like below the existing hollow deck, the existing hollow deck can be safely removed without restricting the space below. Furthermore, since intermediate support in the center is no longer necessary, workability is improved. [Brief explanation of the drawings]
[0015] [Figure 1] FIG. 1 is a view showing an example of a bridge equipped with an existing hollow deck from a direction perpendicular to the bridge axis. [Figure 2] FIG. 2 is a cross-sectional view of an example of an existing hollow deck taken along a plane perpendicular to the bridge axis. [Figure 3]Figure 3(a) is a cross-sectional view of the protruding portion of an existing hollow deck with an external cable attached, cut along the bridge axis direction, and Figure 3(b) is a cross-sectional view of the main girder portion of an existing hollow deck with a first reinforcing member and a second reinforcing member attached, cut along the bridge axis direction. [Figure 4] FIG. 4(a) is an enlarged view of part A in FIG. 3(a), and FIG. 4(b) is an enlarged view of part B in FIG. 3(a). [Figure 5] Figure 5(a) is a cross-sectional view of the existing hollow deck slab taken near the fixing bracket along a plane perpendicular to the bridge axis, and Figure 5(b) is a cross-sectional view of the existing hollow deck slab taken near the deflection bracket along a plane perpendicular to the bridge axis. [Figure 6] FIG. 6 is a plan view showing the cutting position of the existing hollow deck slab. [Figure 7] Figure 7(a) is a view showing the first block supported by the support from a direction perpendicular to the bridge axis, and Figure 7(b) is a view showing the second block supported by the support from a direction perpendicular to the bridge axis. [Figure 8] FIG. 8 is a plan view showing the cutting position when the outbound track of the existing hollow deck is removed. DETAILED DESCRIPTION OF THE INVENTION
[0016] Hereinafter, a method for removing an existing hollow deck slab according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0017] As shown in Figure 1, the bridge 100 comprises a pair of piers 8, which are substructures, and an existing hollow deck 1 supported by the pair of piers 8. The existing hollow deck 1 is a continuous girder supported by bearings (not shown) installed on the piers 8. Below the existing hollow deck 1, a crossing road (not shown) is provided.
[0018] As shown in Figure 2, the existing hollow deck 1 is made of concrete and has a hollow portion 13. The existing hollow deck 1 has a main girder portion 11 located in the center in the direction Y perpendicular to the bridge axis, and a pair of protruding portions 12 (12a, 12b) formed by protruding from the end of the main girder portion 11 in the direction Y perpendicular to the bridge axis and having a thickness in the height direction Z that is thinner than that of the main girder portion 11.
[0019] The main girder 11 has multiple cylindrical hollow sections 13 extending in the bridge axis direction X. The hollow sections 13 are arranged side by side in the direction Y perpendicular to the bridge axis. The main girder 11 has one side surface 11a and the other side surface 11b. The main girder 11 has a solid connecting section 14 that connects to the protruding section 12 outside the hollow sections 13 at the end in the direction Y perpendicular to the bridge axis.
[0020] Next, a method for removing the existing hollow deck slab 1 in this embodiment will be described.
[0021] The method for removing the existing hollow deck slab 1 includes an attachment process, a cutting process, and a removal process.
[0022] <Installation process> As shown in Figure 3(a), in the installation process, anchoring brackets 21 are attached to the underside of both end portions of the existing hollow deck 1 in the bridge axis direction X. In the installation process, deflection brackets 22, 22 are attached to the underside of the existing hollow deck 1 between the pair of anchoring brackets 21, 21. The anchoring bracket 21 is used to anchor the outer cable 3 as an extension member to the existing hollow deck 1 and apply tension to the existing hollow deck 1. The deflection bracket 22 is used to deflect the outer cable 3.
[0023] In detail, as shown in Figures 4(a), 4(b), 5(a) and 5(b), in the installation process, a first through hole 15 is drilled that penetrates from the top surface to the bottom surface of one of the protrusions 12a of the existing hollow deck slab 1, and the anchoring portion bracket 21 and the deflection portion bracket 22 are attached to the bottom surface of the protrusion 12 of the existing hollow deck slab 1 using a first PC steel rod 23 placed in the first through hole 15.
[0024] The anchorage bracket 21 is composed of a mounting plate 21a that fits along the underside of the overhanging portion 12, and a support plate 21b that stands upright relative to the mounting plate 21a. A first PC steel rod 23 is attached to the mounting plate 21a. An outer cable 3 is attached to the support plate 21b. An anchor plate, a washer, a nut, etc. are provided on the first PC steel rod 23.
[0025] The deflection portion bracket 22 is composed of a mounting plate 22a that fits along the underside of the overhanging portion 12, and a deflection portion 22b that is attached to the mounting plate 22a. A first prestressing steel rod 23 is attached to the mounting plate 22a. The deflection portion 22b deflects the outer cable 3.
[0026] The anchoring portion bracket 21 and the deflection portion bracket 22 are attached to the overhanging portion 12a by applying a tension of, for example, about 10 kN to 560 kN to the first prestressing steel rod 23. The first prestressing steel rod 23 used to attach the anchoring portion bracket 21 is, for example, a D36 prestressed concrete steel bar. The first prestressing steel rod 23 used to attach the deflection portion bracket 22 is, for example, a D25 prestressed concrete steel bar.
[0027] Then, in the installation process, the outer cable 3 is attached to the anchoring bracket 21 and the deflection bracket 22 attached to the underside of the overhanging portion 12 of the existing hollow deck 1. The outer cable 3 is made of, for example, a prestressed concrete (PC) deformed steel bar and is extended in the bridge axis direction X. The outer cable 3 is made of, for example, a D22 prestressed concrete (PC) deformed steel bar. The deflection bracket 22 is placed between the anchoring brackets 21, 21. As shown in Figure 7(a) , the outer cable 3 as an extension member is extended in the bridge axis direction X from near one pier 8 to near the other pier 8 on the underside of the overhanging portion 12 of the existing hollow deck 1 between a pair of piers 8, 8. In other words, the extension member is extended from one end to the other end in the bridge axis direction of the existing hollow deck 1 to be removed.
[0028] In the attachment process, tension is applied to the outer cable 3 to which the fixing portion bracket 21 and the deflection portion bracket 22 are attached. A tension of, for example, about 150 kN to 190 kN is applied to the outer cable 3.
[0029] 3(b), 5(a), and 5(b), in the installation process, second through holes 16 are drilled that penetrate from the top surface of the main girder 11 to the bottom surface, and a first reinforcing member 25 extending in the bridge axis direction X is attached to the top surface of the main girder 11, and a second reinforcing member 26 extending in the bridge axis direction X to the bottom surface of the main girder 11 is attached using second PC steel rods 24 placed in the second through holes 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 top surface and bottom surface of the main girder 11 of the existing hollow deck slab 1 between a 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 11 by applying a tension of, for example, about 20.5 kN to the second PC steel rod 24. The first reinforcing member 25 is arranged in pairs, sandwiching the second PC steel rod 24 in the direction Y orthogonal to the bridge axis. The pair of first reinforcing members 25 are joined to each other with steel plates. The second reinforcing member 26 is arranged in pairs, sandwiching the second PC steel rod 24 in the direction Y orthogonal to the bridge axis. The pair of second reinforcing members 26 are joined to each other with steel plates.
[0031] The first reinforcing member 25 is disposed on the upper surface of the main girder 11 above the hollow portion 13. The second reinforcing member 26 is disposed on the lower surface of the main girder 11 below the hollow portion 13.
[0032] As shown in FIG. 3(b), in the installation process, reinforcement bodies 27 made of non-shrinkage mortar may be provided on both ends of the hollow portion 13 of the main girder portion 11 in the bridge axis direction X. The reinforcement bodies 27 may be pipe supports. The installation of the reinforcement bodies 27 is preferably performed before the installation of the first reinforcing member 25 and the second reinforcing member 26. The provision of the reinforcement bodies 27 reinforces the main girder portion 11, including the hollow portion 13. Therefore, for example, when tension is applied by the second PC steel rod 24 during installation of the first reinforcing member 25 and the second reinforcing member 26, or when the main girder portion 11 is cut to form a second block 74 including the hollow portion 13 (described later), the second block 74 can be prevented from being destroyed and the cross-sectional shape of the second block 74 can be maintained.
[0033] As shown in Figures 7(a) and 7(b), in the installation process, hanging pieces 7 for lifting with a lifting device are attached to the upper surface of the main girder 11 and the upper surface of the overhanging portion 12. The hanging pieces 7 attached to the main girder 11 are attached to, for example, the second PC steel rods 24. The hanging pieces 7 attached to the overhanging portion 12 are attached to, for example, the first PC steel rods 23.
[0034] As shown in FIG. 5, in the attachment step, a hanging piece (not shown) is also attached to the upper surface of the connecting portion 14.
[0035] As shown in Figures 3(a), 3(b), 5(a), 5(b), and 6, cutting positions 61 to 65 are set in the existing hollow deck slab 1 of each of the outbound track 18 and the inbound track 19 to form first blocks 71, 72 and second blocks 73, 74, which will be described later. The pair of cutting positions 61 extend in the direction Y perpendicular 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 Figures 3(a), 3(b), 5(a), 5(b), and 6, cutting position 61 is set on the support side in the bridge axis direction X of the anchoring portion bracket 21. Cutting position 62 is set on the main girder portion 11. Cutting position 63 is set on the protruding portion 12. Cutting position 63 is spaced apart from the connecting portion 14. Cutting position 64 is set at the boundary between the protruding portion 12 and the connecting portion 14 so as to be along one side surface 11a of the main girder portion 11. Cutting position 65 is set on the main girder portion 11.
[0037] In this way, in the installation process, extension members extending in the bridge axis direction X from near one pier 8 to near the other pier 8 are attached to the upper surface of the main girder 11, the underside of the main girder 11, and the underside of the overhanging portion 12 of the existing hollow deck 1 between a pair of piers 8, 8. Note that in the installation process of the present invention, extension members extending in the bridge axis direction X from near one pier 8 to near the other pier 8 may also be attached to at least either the upper surface or the underside of the existing hollow deck 1 between a pair of piers 8, 8.
[0038] <Cutting process> In the cutting process, after tensioning the external cable 3, the existing hollow deck slab 1 is cut in the bridge axis direction X to form first blocks 71, 72 having the external cable 3.
[0039] In detail, as shown in Figures 3(a), 3(b), and 6, in the cutting process, first, cutting is performed along a pair of cutting positions 61 that are set on the support side of the anchorage bracket 21 of the existing hollow deck 1 in the bridge axis direction X and extend along the direction orthogonal to the bridge axis Y. The cutting positions 61 extend in the direction orthogonal to the bridge axis Y, spanning the protruding portion 12 (12a) and the main girder portion 11. In addition, in the cutting process, cutting is performed along cutting positions 62 that are set on the main girder portion 11 of the existing hollow deck 1 and extend along the bridge axis direction X. The cutting positions 62 are connected to the pair of cutting positions 61. This allows the first region 1a surrounded by the cutting positions 61 and 62 to be separated in the existing hollow deck 1.
[0040] As shown in Figures 7(a) and 7(b), the separated first region 1a is supported from below by a pair of end supports 81, 82 that were installed in advance before separation. The pair of end supports 81, 82 are arranged between piers 8, 8 that support both ends of the existing hollow slab 1 in the bridge axis direction X. The pair of end supports 81, 82 support both ends of the first region 1a in the bridge axis direction X. The end supports 81, 82 may be installed below the existing hollow slab 1 before cutting the existing hollow slab 1. The end supports 81, 82 may be installed, for example, during the installation process or during the cutting process.
[0041] 3(a), 3(b), and 6, in the cutting process, cutting is performed along cutting positions 63, 64 that connect to the pair of cutting positions 61 and extend in the bridge axis direction X, to form first blocks 71, 72 composed of the protruding portion 12. The first blocks 71, 72 include the central portion in the bridge axis direction X of the first region 1a of the existing hollow deck slab 1, and the length in the bridge axis direction X of the first blocks 71, 72 is, for example, about 13.5 m. The width of the first blocks 71, 72 in the direction perpendicular to the bridge axis Y is, for example, about 0.5 to 1 m.
[0042] The underside of the first block 71 and the underside of the first block 72 each have an external cable 3. Here, when the existing hollow deck 1 is cut, the tension acting on the first blocks 71, 72 by the external cable 3 may fluctuate. For this reason, in the cutting process, after the first blocks 71, 72 are formed, the external cables 3 of the first blocks 71, 72 may be tensioned again with a predetermined tension. This allows an appropriate tension to be applied in the removal process, even if the tension acting on the first blocks 71, 72 fluctuates due to the cutting of the existing hollow deck 1.
[0043] In the cutting process, cutting is performed along cutting positions 65 that connect the pair of cutting positions 61 and extend in the bridge axis direction X to form second blocks 73 and 74 each composed of a main girder portion 11. The second block 73 does not include a hollow portion 13 and is composed of a connecting portion 14. The second block 74 includes a 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 deck slab 1, and the length in the bridge axis direction X of the second blocks 73 and 74 is, for example, approximately 13.5 m. The width of the second blocks 73 and 74 in the direction perpendicular to the bridge axis Y is, for example, approximately 0.5 to 1 m. Note that in the cutting process of the present invention, multiple second blocks each having a first reinforcing member 25 and a second reinforcing member 26 may be formed. In this case, in the removal step of the present invention, a plurality of second blocks may be removed in sequence.
[0044] In this way, in the cutting step, the existing hollow deck 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 approximately 70 tons that cannot lift the entire existing hollow deck 1 alone. The lifting devices 83 and 84 are, for example, disposed on both sides of the existing hollow deck 1 in the bridge axis direction X, sandwiching the first area 1a to be removed. 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 lifting device 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 lifting device 84. In this way, the first block 71 is removed by mutual lifting by the lifting devices 83 and 84.
[0046] Since the first block 71 is subjected to an upward convex bending moment due to tension applied by the outer cable 3, when the first block 71 is removed by the lifting devices 83, 84 in the removal process, the downward convex 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 the first block 71 can be removed safely.
[0047] In the removal step, the formed first block 72 is similarly lifted by the lifting devices 83 and 84 and removed.
[0048] In the removal step, the formed second block 73 is similarly lifted by the lifting devices 83 and 84 and removed.
[0049] As shown in FIG. 7(b), in the removal step, the formed second block 74 is lifted and removed by lifting devices 83, 84 such as cranes.
[0050] Since second block 74 is reinforced by first reinforcing member 25 and second reinforcing member 26, it is possible to reduce the downward bending moment acting on the central portion of second block 74 when second block 74 is removed by lifting devices 83 and 84 in the removal process. As a result, damage to the central portion of second block 74 can be suppressed, and second block 74 can be removed safely.
[0051] In this manner, in the removal process, the blocks are removed by the lifting devices 83 and 84.
[0052] As a result, removal of the first area 1a including one of the protruding portions 12a on the down line 18 is completed.
[0053] As shown in Figure 8, the first area 1a including the other overhanging portion 12b on the up track 19 is also removed using the same procedure. Then, areas other than the first area 1a of the existing hollow deck slab 1 can also be cut to a predetermined size and then removed using a lifting device.
[0054] This completes the method for removing the existing hollow deck 1. Note that before removing the existing hollow deck 1, a displacement meter may be installed in advance on the existing hollow deck 1, and the method for removing the existing hollow deck 1 may be performed while measuring displacement. By removing the existing hollow deck 1 while measuring displacement, the existing hollow deck 1 can be removed more safely.
[0055] According to this embodiment, the method includes an attachment process for 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 and lower surfaces of the existing hollow deck slab 1, and a cutting process for cutting the existing hollow deck slab 1 to form a block having the extension member. This improves the resistance to bending of the block. Therefore, when the block is removed by the lifting devices 83, 84 in the removal process, it can resist a downward bending moment acting on the center of the block. As a result, damage to the block of the existing hollow deck slab 1 can be suppressed, allowing it to be removed safely.
[0056] Furthermore, according to this embodiment, the center of the existing hollow deck 1 in the bridge axis direction X is not cut, so the intermediate support in the center in the bridge axis direction that was previously required is no longer necessary. Therefore, even if there is an intersecting road or the like below the existing hollow deck, it can be safely removed without restricting the space below it. Furthermore, since the intermediate support in the center is no longer necessary, workability can be improved.
[0057] This embodiment includes an installation process in which an anchorage bracket 21 is attached to the underside of the overhanging portion 12 of the existing hollow deck slab 1, an external cable 3 is attached to the anchorage bracket 21, and tensions the external cable 3; and a cutting process in which, after tensioning the external cable 3, the existing hollow deck slab 1 is cut to form first blocks 71, 72 each having the external cable 3. This allows an upwardly convex bending moment to act on the first blocks 71, 72 at their central portions in the bridge axis direction X. Therefore, when the first blocks 71, 72 are removed by the lifting devices 83, 84 in the removal process, the downwardly convex bending moment acting on the central portions of the first blocks 71, 72 can be resisted. As a result, damage to the first blocks 71, 72 of the existing hollow deck slab 1 can be suppressed, allowing them to be removed safely.
[0058] According to this embodiment, a cutting process is provided in which, after tensioning the external cable 3, the existing hollow deck 1 is cut to form first blocks 71, 72 each having the external cable 3. Since the central portion of the existing hollow deck 1 in the bridge axis direction X is not cut, the intermediate support in the central portion in the bridge axis direction that was previously required is no longer necessary. Therefore, even if there is an intersecting road or the like below the existing hollow deck, it can be safely removed without restricting the space below it. Furthermore, since the intermediate support in the central portion is no longer necessary, workability is improved.
[0059] According to this embodiment, an attachment step is provided in which an anchorage bracket 21 is attached to the underside of the protruding portion 12 of the existing hollow deck slab 1, and the external cable 3 is attached to the anchorage bracket 21. Since no tension members are installed in the hollow portion as in the prior art, the external cable 3 can be easily attached, thereby improving workability.
[0060] According to this embodiment, in the installation process, a first through hole 15 is drilled that penetrates from the top surface to the bottom surface of the existing hollow deck slab 1, and the anchorage bracket 21 is attached to the underside of the existing hollow deck slab 1 using a first PC steel rod 23 placed in the first through hole 15. This allows the anchorage bracket 21 to be attached to the underside of the existing hollow deck slab 1 without pouring concrete, further improving workability.
[0061] According to this embodiment, the existing hollow deck 1 has a main girder 11 and an overhanging portion 12 that is formed by overhanging from the end of the main girder 11 in the direction orthogonal to the bridge axis Y and is thinner than the main girder 11. In the installation process, an anchoring bracket 21 is attached to the underside of the overhanging portion 12, and in the cutting process, the overhanging portion 12 is cut in the bridge axis direction X to form first blocks 71, 72. This allows the tension force of the external cable 3 to be applied to the thin first blocks 71, 72 that have little resistance to bending moments. This effectively prevents damage to the first blocks 71, 72 of the existing hollow deck slab 1, allowing them to be removed safely.
[0062] According to this embodiment, in the installation process, second through holes 16 are drilled through the main girder 11 from its upper surface to its lower surface. Then, using second PC steel rods 24 placed in the second through holes 16, a first reinforcing member 25 extending in the bridge axis direction X is attached to the upper surface of the main girder 11, and a second reinforcing member 26 extending in the bridge axis direction X and having lower rigidity than the first reinforcing member 25 is attached to the underside of the main girder 11. Because the second block 74 is reinforced by the first reinforcing member 25 and the second reinforcing member 26, it can resist a downward bending moment acting on the center of the second block 74 when the second block 74 is removed by the lifting devices 83 and 84 in the removal process. As a result, damage to the center of the second block 74 of the existing hollow deck slab 1 can be suppressed, allowing for safe removal.
[0063] According to this embodiment, a first reinforcing member 25 and a second reinforcing member 26 are attached to the second block 74 including the hollow portion 13. As a result, the second block 74 including the hollow portion 13, which has difficulty resisting bending moments, can be reinforced by the first reinforcing member 25 and the second reinforcing member 26. Therefore, damage to the second block 74 of the existing hollow deck 1 can be effectively suppressed, and it can be removed safely.
[0064] In addition, the relatively large first reinforcing member 25 is attached to the upper surface of the existing hollow deck 1, which is easier to work on, and the small second reinforcing member 26 is attached to the lower surface of the existing hollow deck 1, which is more difficult to work on, so the first reinforcing member 25 and the second reinforcing member 26 can be attached efficiently.
[0065] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. Furthermore, the present invention can be embodied in various novel forms in addition to the above-described embodiments. Therefore, various omissions, substitutions, and modifications are possible in the above-described embodiments without departing from the spirit and scope of the present invention. Such novel forms and modifications are included within the scope and spirit of the present invention, as well as within the scope of the inventions set forth in the claims and equivalents of the inventions set forth in the claims. [Explanation of symbols]
[0066] 1: Existing hollow deck 11: Main girder 12: Overhang 13: Hollow part 14: Joint 15: First through hole 16: Second through hole 21: Fixing bracket 22: Deflection bracket 23: 1st PC steel bar 24: 2nd PC steel bar 25: First reinforcing member 26: Second reinforcing member 3: External cable 71: Block 1 72: 1st Block 73: Second Block 74: Second Block 8: Pier 81: End shoring 82: End shoring
Claims
1. A method for removing an existing hollow deck slab supported by a substructure, comprising: An attachment process of attaching an extension member extending in the bridge axis direction from near one of the substructures to near the other substructure on at least one of the upper and lower surfaces of the existing hollow deck slab between the pair of substructures; a cutting step of cutting the existing hollow deck 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 deck slab, characterized by:
2. The existing hollow deck has a main girder portion and a protruding portion formed by protruding from the end of the main girder portion in the direction perpendicular to the bridge axis and having a thickness thinner than that of the main girder portion, In the mounting step, a fixing bracket is attached to the underside of the overhanging portion, an outer cable extending in the bridge axis direction is attached to the fixing bracket, and the outer cable is tensioned. In the cutting step, after tensioning the external cable, the existing hollow deck slab is cut to form a first block having the external cable; In the removing step, the first block is removed.
2. A method for removing an existing hollow deck slab according to claim 1.
3. In the mounting step, a first through hole is drilled through the protruding portion from the upper surface to the lower surface thereof, and the anchoring portion bracket is mounted on the lower surface of the protruding portion by a first PC steel rod disposed in the first through hole.
3. The method for removing an existing hollow deck slab according to claim 2,
4. In the cutting step, after the first block is formed, the outer cable in the formed first block is tensioned again.
3. The method for removing an existing hollow deck slab according to claim 2,
5. In the cutting step, a plurality of the first blocks are formed, In the removing step, the plurality of first blocks are sequentially removed.
3. The method for removing an existing hollow deck slab according to claim 2,
6. The existing hollow deck has a main girder portion and a protruding portion formed by protruding from the end of the main girder portion in the direction perpendicular to the bridge axis and having a thickness thinner than that of the main girder portion, In the mounting step, a first reinforcing member extending in the bridge axis direction is mounted on the upper surface of the main girder portion, and a second reinforcing member extending in the bridge axis direction and having lower rigidity than the first reinforcing member is mounted on 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 removing step, the second block is removed.
2. A method for removing an existing hollow deck slab according to claim 1.
7. In the attaching step, a second through hole penetrating from the upper surface to the lower surface of the main girder portion is drilled, and the first reinforcing member and the second reinforcing member are attached by a second PC steel rod disposed in the second through hole. The method for removing an existing hollow deck slab according to claim 6,
8. In the cutting step, a plurality of the second blocks are formed, In the removing step, the plurality of second blocks are sequentially removed. The method for removing an existing hollow deck slab according to claim 6,
9. In the attaching step, reinforcing bodies are attached to both ends of the hollow portion of the main girder portion in the bridge axis direction, In the cutting step, the main girder portion is cut 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 deck slab according to claim 6,
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