Method for removing the deck slab of a composite girder
The method of forming annular cuts and lifting the deck slab using jacks addresses the inefficiencies of conventional methods, enabling efficient and safe removal of bridge deck slabs in composite girders.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- IHI INFRASTRUCTURE SQUARE CO LTD
- Filing Date
- 2025-01-08
- Publication Date
- 2026-07-21
AI Technical Summary
Conventional methods for removing bridge deck slabs in composite girders require extensive cutting and crushing, leading to significant concrete waste, noise, vibration, and dust, making them unsuitable for urban areas.
Form annular cuts around shear-preventing members on the deck slab using a core drill, and lift the slab using jacks to minimize concrete remaining on the girder, ensuring uniform displacement to prevent bending stress.
Efficient removal of the deck slab without dividing it perpendicular to the bridge axis, reducing concrete waste and noise, vibration, and dust, while ensuring safe lifting without damage.
Smart Images
Figure 2026119823000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for removing a floor slab of a composite girder for removing an existing floor slab from a bridge composed of composite girders and replacing it with a new floor slab.
Background Art
[0002] Conventionally, for bridges such as general roads and highways, there are known ones using composite girders in which concrete is placed on a steel girder to provide a floor slab, or a floor slab is provided by placing concrete on a part of a factory-produced floor slab. In the composite girder, a plurality of anti-slip members are provided on the upper surface of the steel girder, and the concrete of the floor slab is placed in a state where the anti-slip members are embedded, or by placing concrete on a part of the factory-produced floor slab, the girder and the floor slab are coupled by the anti-slip members. When the floor slab deteriorates, a floor slab replacement construction for removing the existing floor slab and reconstructing a new floor slab is carried out (see, for example, FIGS. 11 to 14 of Patent Document 1).
[0003] In the conventional floor slab removal method, first, the floor slab to be removed is cut in a direction perpendicular to the bridge axis and divided in the bridge axis direction. However, since the anti-slip members of the main girder are firmly bonded to the concrete of the floor slab, the floor slab cannot be lifted as it is. Therefore, the floor slab is cut in the bridge axis direction on both sides of the upper flange of the main girder, and the part other than the concrete on the main girder is lifted and removed with a crane or the like while leaving the concrete on the upper flange. After that, the concrete remaining on the main girder is crushed by mechanical work using a large breaker or manual work using a hand breaker, etc., and the removal and collection of the concrete debris generated in the crushing work are carried out. Then, the cutting and removal of the anti-slip members, the removal of the remaining concrete debris, the surface finishing of the main girder, etc. are carried out.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
[0005] However, conventional methods for removing bridge decks involve cutting the deck in multiple locations along the bridge axis so that concrete remains on the main girders, and then dividing it into multiple sections perpendicular to the bridge axis. This requires removing each divided concrete block, resulting in a large amount of work for removing the concrete blocks. Furthermore, because the concrete of the deck cut along the bridge axis remains on the main girders, the crushing of the remaining concrete generates a large amount of concrete waste, which requires considerable effort to collect. In addition, the noise, vibration, and dust generated by the large-scale concrete crushing work continue for a long time, making it unsuitable for work in urban areas.
[0006] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a method for removing the deck slab of a composite girder that can improve the efficiency of deck slab removal work and reduce the amount of concrete remaining on the girder. [Means for solving the problem]
[0007] To achieve the above objective, the present invention provides a method for removing a concrete deck slab from a composite girder in which a concrete deck slab is installed on a steel girder and the steel girder and deck slab are connected by a shear-preventing member provided on the upper surface of the steel girder. In this method, annular cuts are formed at multiple locations on the deck slab from the upper surface side so as to surround a portion including at least a part of the shear-preventing member, and the concrete outside the area enclosed by each cut is lifted by a plurality of jacks installed at intervals in the bridge axis direction and perpendicular to the bridge axis of the deck slab, respectively, and each jack is operated so that the difference in the relative displacement of the upper end surfaces of the concrete in the area enclosed by each cut at multiple locations in the bridge axis direction and perpendicular to the bridge axis of the deck slab is within a predetermined range.
[0008] As a result, the resistance force between the shear-preventing member and the concrete of the deck slab against tensile load is reduced by the cuts, making it possible to easily separate the deck slab from the steel girder. Furthermore, since each jack is operated so that the difference in the relative displacement of the upper surface of the concrete in the area enclosed by each cut is within a predetermined range compared to the upper surface of the concrete outside the area enclosed by each cut, unnecessary bending stress due to uneven reaction forces is not generated in the deck slab during lifting. [Effects of the Invention]
[0009] According to the present invention, the deck slab can be easily separated from the steel girder, eliminating the need to cut the deck slab in the bridge axis direction so that concrete remains on the girder as in conventional methods. The deck slab on the girder can be lifted and removed in one go without being divided perpendicular to the bridge axis. This improves the efficiency of the removal work. Furthermore, since the amount of concrete remaining on the girder can be significantly reduced, there is the advantage of not needing large-scale concrete crushing work. As a result, the removal and collection of large amounts of concrete debris does not take a long time, and the generation of noise, vibration, and dust from concrete crushing work can be significantly reduced, thus minimizing adverse effects on the surrounding area even when working in urban areas. Moreover, since no unnecessary bending stress is generated in the deck slab due to uneven reaction forces during lifting, the deck slab can be safely removed without being damaged during lifting. [Brief explanation of the drawing]
[0010] [Figure 1] Partial perspective view of a composite girder showing one embodiment of the present invention. [Figure 2] Partial front cross-section of the composite girder [Figure 3] Partial front cross-sectional view of the composite girder showing the deck slab removal process. [Figure 4] Enlarged front cross-sectional view of the main part of the composite girder showing the deck slab removal process. [Figure 5] Partial plan view of the floor slab showing the cuts. [Figure 6] Partial side cross-sectional view of a composite girder showing the deck slab removal process. [Figure 7] Partial front cross-sectional view of the composite girder showing the process of removing the floor slab [Figure 8] Partial side cross-sectional view of the composite girder showing the process of removing the floor slab [Figure 9] Enlarged front cross-sectional view of the main part of the composite girder showing the process of removing the floor slab [Figure 10] Partial enlarged perspective view of the floor slab showing the displacement of the part surrounded by the notch [Figure 11] Partial perspective view of the composite girder showing the process of removing the floor slab [Figure 12] Partial side cross-sectional view of the composite girder showing the process of removing the floor slab [Figure 13] Enlarged front cross-sectional view of the main part of the composite girder showing the process of removing the floor slab [Figure 14] Partial plan view of the floor slab showing a modified example of the notch [Figure 15] Partial plan view of the floor slab showing another modified example of the notch
Mode for Carrying Out the Invention
[0011] Figs. 1 to 13 show an embodiment of the present invention, and show a method for removing the deteriorated floor slab from an existing bridge composed of composite girders.
[0012] The composite girder 1 shown in the figure consists of a plurality of main girders 2 arranged in parallel to each other and a concrete floor slab 3 installed on each main girder 2.
[0013] Each main girder 2 consists of a steel girder having upper and lower flanges 2b and 2c at the upper and lower ends of the web 2a, respectively, and is arranged at intervals in a direction perpendicular to the bridge axis. Further, a plurality of displacement preventing members 4 for connecting the main girder 2 and the floor slab 3 are provided on the upper surface of the upper flange 2b.
[0014] The floor slab 3 is formed by the concrete placed on the upper flange 2b of each main girder 2, and wall height fences 3a are integrally formed on both sides in the width direction thereof. In the floor slab 3, by placing the concrete so that each displacement-preventing member 4 is embedded, the main girder 2 and the floor slab 3 are joined by each displacement-preventing member 4.
[0015] The displacement-preventing member 4 is formed of a metal rod-shaped member extending in the vertical direction and consists of a so-called stud dibel having a head with a larger outer diameter than other parts at the upper end. A plurality of these displacement-preventing members 4 (for example, four) are arranged in the direction perpendicular to the bridge axis, and are provided at predetermined intervals in the bridge axis direction from one end side to the other end side in the longitudinal direction of the main girder 2.
[0016] In the method for removing the floor slab of the present embodiment, a core drill 10 for drilling holes at the locations where the displacement-preventing members 4 are arranged in the floor slab 3 and a floor slab peeling device 20 for peeling the cut floor slab 3 from the main girder 2 are used.
[0017] The core drill 10 uses a well-known electric tool for drilling holes by drilling the concrete into a cylindrical shape. In the present embodiment, by drilling the concrete of the floor slab 3 with the cylindrical blade portion 11 of the core drill 10, an annular cut 5 having a desired depth is formed in the floor slab 3.
[0018] The floor slab peeling device 20 includes a pair of first legs 21 arranged at intervals in the bridge axis direction, a second leg 22 arranged below one of the legs 21 in the bridge axis direction, a beam portion 23 whose longitudinal ends are respectively supported by the first legs 21, a pair of fastening members 24 for fastening to the floor slab 3, and a plurality of jacks 25 for raising the fastening members 24 with respect to the beam portion 23. The fastening member 24 includes an upper rod 24a supported by the jack 25 and a lower rod 24b for fastening to the floor slab 3, and the upper rod 24a and the lower rod 24b are detachably connected to each other by a coupling member 24c. Further, a connecting portion 24d for connecting a lifting wire 30 is provided on the lower rod 24b.
[0019] Here, the method for removing the bridge deck in this embodiment will be described with reference to Figures 3 to 13. In this embodiment, the bridge deck 3 to be removed is divided in the direction of the bridge axis by cutting it perpendicular to the bridge axis, and as shown in Figure 2, the bridge deck 1 is cut in the direction of the bridge axis at a predetermined position C perpendicular to the bridge axis (for example, the center perpendicular to the bridge axis), and a part of the bridge deck 3 including the wall parapet 3a is removed.
[0020] First, as shown in Figure 3, a core drill 10 is used to form annular cuts 5 around each of the shear prevention members 4. At the same time, as shown in Figure 4, the core drill 10 is used to drill a hole in the concrete from the upper surface of the deck slab 3 downwards, leaving a predetermined height h, up to slightly above the upper flange 2b of the main girder 2, thereby forming cuts 5 that extend in the vertical direction. Furthermore, as shown in Figure 5, the cuts 5 of the four shear prevention members 4, which are arranged perpendicular to the bridge axis, are formed without any gaps so that a portion of the circumferential surface of adjacent cuts 5 is continuous. The positions of the shear prevention members 4 can be determined from the design drawings of the existing bridge, etc.
[0021] Next, as shown in Figures 6 and 7, a deck slab removal device 20 is installed on the composite girder 1, and the deck slab 3 in the removal section is removed from each main girder 2 by the deck slab removal device 20. As shown in Figure 6, the deck slab removal device 20 has first legs 21 arranged at intervals in the bridge axis direction with the deck slab 3 in the removal section in between, and the beam section 23 is supported by the first legs 21 on both sides in the bridge axis direction. At this time, one of the first legs 21 in the bridge axis direction is placed on the deck slab 3 outside the removal section, and the other first leg 21 in the bridge axis direction is placed on the main girder 2 from which the deck slab has been removed via a second leg 22. In addition, fastening rods 24 and jacks 25 are arranged at two locations on the beam section 23 at intervals in the longitudinal direction (bridge axis direction), and the lower rod 24b of the fastening rod 24 penetrates the deck slab 3 in the removal section vertically and is fastened to the deck slab 3.
[0022] Furthermore, the deck slab removal device 20 is installed at two locations at intervals perpendicular to the bridge axis, as shown in Figure 7. As a result, the deck slab 3 in the section to be removed is lifted by four jacks 25 at a total of four locations: two in the direction of the bridge axis and two perpendicular to the bridge axis.
[0023] Next, as shown in Figure 8, the deck slabs 3 are separated from the main girders 2 by raising each fastening rod 24 of each deck slab separation device 20 using each jack 25. At this time, since the cylindrical portion 3b surrounded by each cut 5 is separated from the rest of the deck slab 3 by each cut 5, the resistance force between the shear prevention member 4 and the concrete of the deck slab 3 against tensile load is reduced. As a result, only the concrete in the small portion between the lower end of each cut 5 and the upper flange 2b of the main girder 2 is fractured, and the deck slab 3 is lifted up while each cylindrical portion 3b remains attached to the upper flange 2b, as shown in Figure 9.
[0024] As a result, the upper surface of the floor slab 3 rises relative to the upper end surfaces of each cylindrical portion 3b, creating a step difference in the height direction between the upper surface of the floor slab 3 and the upper end surfaces of each cylindrical portion 3b. Furthermore, the displacement amount H of the floor slab 3 during lifting can be visually confirmed by observing the height position of the upper end surfaces of the cylindrical portions 3b relative to the upper surface of the floor slab 3, as shown in Figure 10. In this case, the fracture energy of the concrete during lifting is generated only by a small portion below each cut 5, so the impact of fracture energy is minimal, and it becomes possible for workers to approach the cut 5 and confirm the displacement amount H.
[0025] Furthermore, when lifting the deck slab 3, the reaction force at each cut 5 may differ from the lifting force of each jack 25 due to differences in the resistance force when the concrete on the upper flange 2b fractures.
[0026] Therefore, as shown in Figure 11, by visually checking the displacement H of the deck slab 3 at positions P1 to P4 of the cuts 5 formed at four locations on the upper surface of the deck slab 3, both perpendicular to the bridge axis and both axially, and by operating the jacks 25 at lifting positions L1 to L4 adjacent to each of the cuts 5 so that the difference in each displacement H is within a predetermined range (for example, within 10 mm), it becomes possible to prevent unnecessary bending stress from being generated in the deck slab 3 due to uneven reaction forces during lifting. It is desirable that each displacement H be uniform or nearly uniform.
[0027] Next, after the removal of the deck slab 3 is completed by each deck slab removal device 20, a crane lifting wire 30 (not shown) is connected to the connecting portion 24d of the lower rod 24b of each deck slab removal device 20, the connection between the upper rod 24a and the lower rod 24b is released, and all parts of the deck slab removal device 20 except the lower rod 24b are removed. Then, as shown in Figure 12, the deck slab 3 is lifted by the wire 30 and removed by the crane.
[0028] After this, as shown in Figure 13, the removal of the existing deck slab 3 is completed by removing the small amount of concrete remaining as each cylindrical portion 3b on each main girder 2 and each shear prevention member 4.
[0029] As described above, according to this embodiment, an annular cut 5 is formed from the upper surface of the deck slab 3 so as to surround the shear prevention member 4, and the deck slab 3 with the cut 5 formed is pulled upward from the main girder 2 and removed. This reduces the resistance force between the shear prevention member 4 and the concrete of the deck slab 3 against tensile loads, and the deck slab 3 can be easily separated from the main girder 2.
[0030] This eliminates the need to cut the deck slab 3 in the direction of the bridge axis while leaving concrete on the main girder 2, as was done in the past. As a result, the deck slab 3 on the main girder 2 can be removed without dividing it at multiple points perpendicular to the bridge axis, thus improving the efficiency of the removal work. In addition, the amount of concrete remaining on the main girder 2 can be significantly reduced, so the amount of concrete crushing work can be greatly reduced. This means that it does not take a long time to remove and collect large amounts of concrete waste, and does not generate noise, vibration, or dust from concrete crushing work, so adverse effects on the surrounding area can be greatly reduced even when working in urban areas.
[0031] Furthermore, by using multiple jacks 25 installed at intervals in the bridge axis direction and perpendicular to the bridge axis direction, respectively, the concrete of the deck slab 3, excluding the cylindrical portions 3b surrounded by each cut 5, is lifted. At the same time, each jack 25 is operated so that the difference in relative displacement H between the upper surface of the concrete of the cylindrical portions 3b surrounded by each cut 5 and the upper surface of the concrete of the cylindrical portions 3b surrounded by each cut 5 is within a predetermined range. As a result, the deck slab 3 is not subjected to unnecessary bending stress due to uneven reaction forces during lifting, and the deck slab 3 can be safely removed without being damaged during lifting.
[0032] Furthermore, since each cut 5 is formed in an annular shape by the core drill 10, the cuts 5 can be easily formed, and the removal work of the floor slab 3 can be carried out efficiently.
[0033] Furthermore, the shear prevention member 4 consists of stud dowels extending in the vertical direction and is arranged perpendicular to the bridge axis on the upper surface of the upper flange 2b of the main girder 2, and is also provided at intervals in the bridge axis direction. Therefore, an annular cutout 5 surrounding the shear prevention member 4 can be easily formed by the core drill 10.
[0034] In this case, multiple notches 5 surrounding each of the anti-slip members 4 arranged perpendicular to the bridge axis are formed without spacing so that a portion of their circumferential surfaces is continuous. This has the advantage that the holes formed by each notch 5 are connected to each other perpendicular to the bridge axis, making it easier to visually inspect the upper end surface of each cylindrical portion 3b.
[0035] Furthermore, since each cut 5 is formed leaving a predetermined height h from the upper surface of the main girder 2, the core drill 10 does not come into contact with the upper flange 2b of the main girder 2 when forming the cut 5, thereby reliably preventing damage to the upper flange 2b.
[0036] In the above embodiment, an annular notch 5 was shown to be formed by the core drill 10 so as to surround each of the anti-slip members 4. However, for example, the pitch of each notch 5 and the pitch of each anti-slip member 4 may be offset, so that the anti-slip member 4 is cut lengthwise by the cutting edge 11 of the core drill 10, and a part of the cut anti-slip member 4 is surrounded by one of the notches 5. In other words, as long as at least a part of the anti-slip member 4 is in the portion surrounded by the notches 5, the same effect as in the above embodiment will be achieved.
[0037] Alternatively, as shown in the modified example in Figure 14, multiple notches 6 surrounding the anti-slip member 4 may be formed using a large-diameter core drill, or the anti-slip member 4 may be surrounded by multiple linearly formed annular notches 7 using a diamond cutter or the like, as shown in another modified example in Figure 15.
[0038] Furthermore, although the above embodiment shows the deck slab 3 being removed by dividing it in half at the center perpendicular to the bridge axis, the present invention can also be applied when the deck slab is removed without dividing it perpendicular to the bridge axis, or when it is removed by dividing it at multiple points perpendicular to the bridge axis.
[0039] Furthermore, although a stud dowel was shown as the anti-slip member 4 in the above embodiment, the anti-slip member is not limited to a stud dowel, and may be an anti-slip member of another shape, such as a block dowel. In this case, an annular notch may be formed to surround the anti-slip member, or an annular notch may be formed to cut a part of the anti-slip member.
[0040] Furthermore, in the above embodiment, the main girder 2 is shown as a steel girder having an upper flange 2b and a lower flange 2c at the upper and lower ends of the web 2a, respectively, but it may be a steel girder of other shapes, such as a box girder. [Explanation of Symbols]
[0041] 1... Composite girder, 2... Main girder, 2b... Upper flange, 3... Deck slab, 3b... Cylindrical section, 4... Anti-slip member, 5, 6, 7... Notches.
Claims
1. In a method for removing a concrete deck slab from a composite girder, in which the concrete deck slab is installed on top of a steel girder and the steel girder and deck slab are connected by a shear-preventing member provided on the upper surface of the steel girder, Annular cuts are formed at multiple locations on the floor slab from the upper surface side so as to surround a portion of the aforementioned anti-slip member, Multiple jacks, placed at intervals in both the bridge axis direction and perpendicular to the bridge axis direction, are used to lift the concrete outside the area enclosed by each cut, Each jack is operated so that, relative to the upper surface of the concrete outside the area enclosed by each cut, the difference in the relative displacement of the upper surface of the concrete in the area enclosed by each cut at multiple locations in the bridge axis direction and perpendicular to the bridge axis of the deck slab is within a predetermined range. A method for removing a composite girder deck slab, characterized by the above.
2. The aforementioned shear prevention members consist of stud dowels extending in the vertical direction, arranged perpendicular to the bridge axis on the upper surface of the steel girder, and provided at intervals in the bridge axis direction. The method for removing the deck slab of a composite girder according to feature 1.
3. The aforementioned cut is formed in an annular shape using a core drill. A method for removing a composite girder deck according to claim 1 or 2, characterized by the present invention.
4. Multiple annular notches are formed without spacing between them, surrounding at least one of the anti-slip members arranged perpendicular to the bridge axis, such that a portion of their circumferential surfaces is continuous. The method for removing the deck slab of a composite girder according to feature 3.
5. The aforementioned cut is formed leaving a predetermined height from the upper surface of the steel girder. The method for removing the deck slab of a composite girder according to feature 1.