Bridge and exterior cable replacement methods

Abstract

To provide a bridge or the like requiring fewer spare holes.SOLUTION: In a PC box girder bridge, prestress in the bridge axial direction is introduced by outer cables located on both sides of a transverse girder 3 in the bridge axial direction. In the transverse girder 3, spare holes 11 are provided through the transverse girder 3 in the bridge axial direction for anchoring spare cables to introduce prestress in the bridge axial direction to the PC box girder bridge. At both ends of the spare hole 11, a rib-cast anchor 14 is provided, which is a receiving member for an anchorage body to anchor the spare cable.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a bridge and an external cable replacement method, etc. [Background technology]

[0002] In PC (prestressed concrete) box girder bridges, cables are installed as tendons in the bridge axis direction, which introduces prestress in the box girder in the bridge axis direction. The box girder is mainly made of concrete, and the cables are made of prestressing steel. Prestressing steel is divided into external cables and internal cables depending on its location. External cables are placed outside the concrete members of the box girder, and internal cables are buried inside the concrete members of the box girder.

[0003] Figure 5(a) is a simplified cross-section of a PC box girder bridge in the bridge axis direction, and Figure 5(b) is a diagram showing range a in Figure 5(a). As shown in the figure, the external cable 5 is installed in the bridge axis direction inside the box girder 100. The bridge axis direction corresponds to the left-right direction in Figures 5(a) and (b).

[0004] In a PC box girder bridge, a box girder 100 is supported by multiple piers 2 in the bridge axis direction, and on each pier 2, a cross girder 3, which is a concrete member perpendicular to the bridge axis, is installed inside the box girder 100. The direction perpendicular to the bridge axis is the direction that forms a right angle with the bridge axis direction on a plane, and corresponds to the direction normal to the paper surface in Figures 5(a) and (b).

[0005] The outer cable 5 is arranged between the cross beams 3, and both ends of the outer cable 5 are fixed to these cross beams 3. As shown in Fig. 5(b), the ends of the outer cable 5 pass through the cross beams 3 in the bridge axis direction and are fixed to the side surfaces 31 of the cross beams 3 by fixing devices 7 (for example, Patent Documents 1 and 2, etc.).

[0006] The cross beam 3 shown in Figure 5(b) has the ends of the outer cables 5 (5a, 5b) fixed to both the left and right sides of the cross beam 3. The outer cable 5a on the right side of the cross beam 3 is fixed to the left side surface 31a of the cross beam 3 by a fixing device 7a, and is arranged in two layers, one above the other. The outer cable 5b on the left side of the cross beam 3 is fixed to the right side surface 31b of the cross beam 3 by a fixing device 7b, and is arranged below the outer cable 5a.

[0007] Figure 5(c) shows a cross section taken along line AA in Figure 5(b) in the direction perpendicular to the bridge axis. As shown in Figure 5(c), a manhole 9 and a spare hole 110 are provided in the cross girder 3. The manhole 9 and spare hole 110 are provided so as to penetrate the cross girder 3 in the direction of the bridge axis. The manhole 9 is a passageway for workers to move around, and the spare hole 110 is provided for future replacement of the outer cable 5. In the example of Figure 5(c), the manhole 9 is provided in the center of the cross girder 3 in the direction perpendicular to the bridge axis, and the spare holes 110 are provided on both sides of the manhole 9, in two rows, one above the other.

[0008] Figure 6 is a diagram for explaining the replacement of the outer cable 5, and shows a cross-sectional perspective view of the box girder 100 in the bridge axis direction. When replacing the outer cable 5a on the right side of the cross girder 3, first, as shown in Figure 6(a), a spare cable 6 is placed on the right side of the cross girder 3, and its end is passed through the spare hole 110 in the upper row of the cross girder 3, and the end is tensioned and fixed to the left side surface 31a of the cross girder 3.

[0009] This temporarily introduces prestress in the bridge axis direction to the box girder 100, then the tension in the external cable 5a is released and replaced with a new external cable 5a, and prestress in the bridge axis direction is reintroduced to the box girder 100 by the tension in the new external cable 5a.

[0010] With prestress introduced by the spare cable 6, the above-described replacement work of the outer cables 5a is carried out one by one to replace all the outer cables 5a to be replaced with new outer cables 5a.

[0011] On the other hand, when replacing the outer cable 5b on the left side of the cross girder 3, as shown in Figure 6(b), a spare cable 6 is placed on the left side of the cross girder 3, its end is passed through the spare hole 110 in the lower row of the cross girder 3, and the end is tensioned and fixed to the right side surface 31b of the cross girder 3. This temporarily introduces prestress in the bridge axis direction to the box girder 100, and then the outer cable 5b is replaced in the same manner as above. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Patent No. 5405889 [Patent Document 2] Patent No. 5014236 Summary of the Invention [Problem to be solved by the invention]

[0013] 6(a) and 6(b), conventionally, different spare holes 110 are used when replacing the left and right outer cables 5 (5a, 5b) of the cross beam 3. Each spare hole 110 is designed to be used only when replacing one of the left and right outer cables 5 (5a, 5b) of the cross beam 3.

[0014] That is, at the end of the spare hole 110, a receiving material such as a rib cast anchor is provided to receive a fixing body for fixing the spare cable 6, but the receiving material is provided at only one end of the spare hole 110, depending on whether the spare hole 110 is to be used when replacing the outer cable 5 (5a, 5b) on the left or right side of the cross beam 3 (i.e., whether the spare cable 6 is placed on the left or right side of the cross beam 3).

[0015] For example, in the case of a spare hole 110 used when replacing the outer cable 5a on the right side of the cross beam 3, the spare cable 6 is placed on the right side of the cross beam 3, so a receiving material is provided only on the left end of the spare hole 110. On the other hand, in the case of a spare hole 110 used when replacing the outer cable 5b on the left side of the cross beam 3, the spare cable 6 is placed on the left side of the cross beam 3, so a receiving material is provided only on the right end of the spare hole 110.

[0016] Therefore, each spare hole 110 can only be used when replacing one of the outer cables 5 (5a, 5b) on the left or right side of the cross girder 3, and in an environment where future replacement of both outer cables 5 (5a, 5b) is expected, the number of spare holes 110 provided in the cross girder 3 will inevitably increase. As a result, when many outer cables 5 are arranged, when a large manhole 9 is installed in the cross girder 3, or when the girder height of the box girder 100 is low, it becomes difficult to secure space for installing the outer cables 5, manholes 9, and spare holes 110, and the degree of freedom in design becomes low.

[0017] The present invention has been made in consideration of the above-mentioned problems, and has as its object to provide a bridge or the like that requires a small number of preliminary holes. [Means for solving the problem]

[0018] The first invention for achieving the above-mentioned object is a bridge having concrete members in its girders, in which prestress in the bridge axis direction is introduced to the bridge girders by external cables arranged on both sides of the concrete members in the bridge axis direction, preliminary holes used to fasten spare cables for introducing prestress in the bridge axis direction to the bridge girders are provided so as to penetrate the concrete members in the bridge axis direction, and support members for receiving anchors for fastening the spare cables are provided at both ends of the preliminary holes.

[0019] In the first aspect of the present invention, because the support members for the anchoring body are provided at both ends of the spare hole, the spare cable can be fixed to the concrete member using the same spare hole regardless of where the spare cable is placed in the concrete member when replacing the external cable, etc. This makes it possible to reduce the number of spare holes required compared to conventional methods.

[0020] The bridge girder is, for example, a box girder, and the concrete member is, for example, a cross girder provided inside the box girder. This allows the number of pre-holes in the cross beams of a box girder bridge to be reduced, increasing the degree of freedom in the design of the cross beams.

[0021] It is desirable that the spare cable be fixed by the fixing body at one end of the spare hole, and that an anti-chafing spacer be installed between the receiving material and the spare cable at the other end of the spare hole. The anti-chafing spacer described above can prevent damage to the spare cable when the spare cable is fixed.

[0022] The second invention is a method for replacing external cables in a bridge according to the first invention, comprising the steps of: passing an end of the spare cable arranged on one side of the concrete member in the bridge axis direction through the spare hole and tensioning the end to fix it to the other side of the concrete member in the bridge axis direction; replacing the external cable arranged on one side of the concrete member in the bridge axis direction with a new external cable; releasing the tension on the spare cable and removing it from the spare hole; passing the end of the spare cable arranged on the other side of the concrete member in the bridge axis direction through the same spare hole and tensioning the end to fix it to one side of the concrete member in the bridge axis direction; and replacing the external cable arranged on the other side of the concrete member in the bridge axis direction with a new external cable. A second invention is a method for replacing an outer cable in a bridge according to the first invention. [Effects of the Invention]

[0023] According to the present invention, a bridge or the like can be provided that requires a small number of preliminary holes. [Brief explanation of the drawings]

[0024] [Figure 1] A diagram showing box girder 1 of a PC box girder bridge. [Figure 2] FIG. [Figure 3] 10A and 10B are diagrams for explaining replacement of an external cable 5. FIG. [Figure 4] 4A and 4B are diagrams for explaining the fixing of the spare cable 6. FIG. [Figure 5] A diagram showing a box girder 100 of a PC box girder bridge. [Figure 6] 10A and 10B are diagrams for explaining replacement of an external cable 5. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. The following description focuses on differences from the conventional structure described in Figure 5, etc. Similar features will be denoted by the same reference numerals in the drawings, etc., and a description thereof will be omitted.

[0026] (1.PC box girder bridge) Figure 1 shows a PC box girder bridge according to an embodiment of the bridge of the present invention, and Figures 1(a) and (b) are respectively views showing a cross section of a box girder 1 (bridge girder) of the PC box girder bridge in the bridge axis direction and a cross section perpendicular to the bridge axis, similar to Figures 5(b) and (c) above.

[0027] As shown in Figure 1, the box girder 1 of the PC box girder bridge of this embodiment has cross girders 3, which are concrete members, similar to the box girder 100 described in Figure 5 etc., but the number of spare holes 11 is fewer than that of the box girder 100. This is because the same spare holes 11 can be used both when replacing the outer cable 5a arranged on the right side of the cross girder 3 and when replacing the outer cable 5b arranged on the left side of the cross girder 3. The spare holes 11 will be described in detail below.

[0028] (2. Spare hole 11) Figure 2 is a partial cross-sectional view in the bridge axis direction of the preliminary hole 11. As shown in Figure 2, the preliminary hole 11 is composed of a recess tube 12, an outer trumpet 13, a rib cast anchor 14, etc., which are embedded in the concrete of the cross beam 3.

[0029] The recess tube 12 is a cylindrical member located in the center of the preliminary hole 11 in the bridge axis direction. The recess tube 12 is made of, for example, but not limited to, metal. One end of the outer trumpet 13 in the bridge axis direction is fitted over each of the two ends of the recess tube 12 in the bridge axis direction. Waterproof tape 17 is wrapped around the boundary between the outer trumpet 13 and the recess tube 12.

[0030] The other end of the outer trumpet 13 in the bridge axis direction is provided with a male thread, and this other end is screwed into a female thread provided at one end of the rib-cast anchor 14 in the bridge axis direction. The other end of the rib-cast anchor 14 in the bridge axis direction is positioned so that it is flush with the side surface 31 of the cross beam 3.

[0031] The outer trumpet 13 and the rib-cast anchor 14 are cylindrical members whose diameter gradually increases as they approach the side surface 31 of the cross beam 3. The rib-cast anchor 14 functions as a support member to bear the pressure from the anchoring body when the end of the spare cable 6 is anchored. The anchoring body will be described later. The outer trumpet 13 is made of resin, for example, and the rib-cast anchor 14 is made of metal, but the materials are not limited to these.

[0032] In the figure, reference numeral 16 denotes a spiral reinforcement, which is embedded in the concrete surrounding the outer trumpet 13 and the rib cast anchor 14 for reinforcement. When the pre-hole 11 is not in use, both ends of the pre-hole 11 are closed with lids (not shown).

[0033] (3. How to replace external cable 5) In this embodiment, when replacing the outer cable 5a on the right side (one side in the bridge axis direction) of the cross beam 3 shown in Figure 1(a), first, a spare cable 6 is placed on the right side of the cross beam 3 as shown in Figure 3(a), and its end is passed through the spare hole 11 of the cross beam 3, and the end is tensioned and fixed to the side surface 31a on the left side (the other side in the bridge axis direction) of the cross beam 3.

[0034] When fixing the end of the spare cable 6 to the side surface 31a, the cover is removed, and then the inner trumpet 18 is placed in the spare hole 11 as shown in FIG. 4(a).

[0035] The inner trumpet 18 has a body 181, which is a long cylindrical member, and a flange 182 that protrudes outward from the end face of the body 181. The inner trumpet 18 is made of, for example, but is not limited to, resin. The body 181 of the inner trumpet 18 is inserted into the left end (one end) of the rib-cast anchor 14a of the preliminary hole 11, and the flange 182 of the inner trumpet 18 is positioned on the other end of the rib-cast anchor 14a.

[0036] The body 181 of the inner trumpet 18 passes through the inside of the chafing prevention spacer 19 and protrudes to the right from the auxiliary hole 11. The chafing prevention spacer 19 is installed inside the rib-cast anchor 14b at the right end (other end) of the auxiliary hole 11, and has a configuration in which a flange 192 protruding outward is provided on the end face of the cylindrical body 191. The length of the body 191 in the bridge axis direction is shorter than that of the rib-cast anchor 14b. The chafing prevention spacer 19 is made of, for example, resin, but is not limited to this.

[0037] The chafing prevention spacer 19 is installed by inserting the body 191 into the rib-cast anchor 14b, and the flange 192 is located on the other end of the rib-cast anchor 14b. The annular retaining metal fitting 20 is placed on the flange 192, and the retaining metal fitting 20 is bolted to the other end of the rib-cast anchor 14b, thereby fixing the chafing prevention spacer 19 to the rib-cast anchor 14b.

[0038] After the inner trumpet 18 and chafing spacer 19 are installed as described above, the end of the spare cable 6 is inserted into the inner trumpet 18 from the right side of the cross beam 3, as shown in Figure 4(b). The end is then tensioned and anchored to the left side surface 31a of the cross beam 3 (the left end of the spare hole 11) using the anchor disk 22. At this time, the pressure from the anchor disk 22 is supported by the rib-cast anchor 14a. The chafing spacer 19 prevents damage to the spare cable 6 caused by rubbing against the rib-cast anchor 14b if the inner trumpet 18 is torn.

[0039] The anchor disk 22 is a fixing body for fixing the end of the spare cable 6 to the side surface 31a of the cross beam 3, and is placed on the other end of the rib-cast anchor 14a, sandwiching the flange 182 of the inner trumpet 18 and a gasket (not shown), and is fixed to the rib-cast anchor 14a with a bolt.

[0040] The spare cable 6 is formed, for example, by bundling multiple prestressing strands, and the position of the end of each prestressing strand in the cross section of the spare hole 11 is determined by spacers 21 inside the inner trumpet 18. The end of each prestressing strand is inserted into a through-hole in the anchor disk 22 at a corresponding position, and in this embodiment, the ends of these prestressing strands are tensioned using a jack or the like (not shown) and fixed to the anchor disk 22 by wedges 23. After the spare cable 6 is fixed in place, grout material is filled inside the inner trumpet 18.

[0041] In this way, the spare cable 6 is tensioned and prestress in the bridge axis direction is temporarily introduced to the box girder 1, after which the tension in the outer cable 5a is released and it is replaced with a new outer cable 5a. Then, prestress in the bridge axis direction is reintroduced to the box girder 1 by tensioning the outer cable 5a. By performing this operation one outer cable 5a at a time, all outer cables 5a to be replaced are replaced with new outer cables 5a. After that, the tension in the spare cable 6 is released and it is removed from the spare hole 11, returning it to the state shown in Figure 2.

[0042] Thereafter, when replacing the outer cable 5b on the left side of the cross beam 3 in Fig. 1(a), first, as shown in Fig. 3(b), the end of the spare cable 6 arranged on the left side of the cross beam 3 is passed through the spare hole 11 in the cross beam 3, and the end is tensioned and fixed to the right side surface 31b of the cross beam 3. The method is the same as that explained in Fig. 4 etc.

[0043] This temporarily applies prestress in the bridge axis direction to the box girder 1, and then the outer cables 5b are replaced in the same manner as above. After all of the outer cables 5b to be replaced have been replaced with new outer cables 5a, the tension on the spare cables 6 is released and they are removed from the spare holes 11.

[0044] 3(a) and 3(b), in this embodiment, unlike the conventional method, the same spare holes 11 are used when replacing the outer cable 5a arranged on the right side of the cross beam 3 and when replacing the outer cable 5b arranged on the left side of the cross beam 3. Therefore, the number of spare holes 11 provided in the cross beam 3 can be reduced compared to the conventional method.

[0045] As described above, according to this embodiment, rib-cast anchors 14 are provided at both ends of the spare hole 11 of the cross girder 3 as receiving materials for receiving the anchor disks 22 for fixing the spare cable 6. Therefore, whether the left or right outer cable 5 (5a, 5b) of the cross girder 3 is to be replaced, that is, whether the spare cable 6 is arranged on the left or right side of the cross girder 3, the spare cable 6 can be fixed to the cross girder 3 using the same spare hole 11. Therefore, compared to the conventional case in which separate spare holes 11 are used when replacing the left and right outer cables 5 (5a, 5b) of the cross girder 3, the number of spare holes 11 required can be reduced, making it easier to secure space for the outer cable 5, manhole 9, and spare hole 11, and increasing the degree of freedom in designing the cross girder 3.

[0046] Furthermore, in this embodiment, when the end of the spare cable 6 is fixed at one end of the spare hole 11, an anti-chafing spacer 19 is placed between the spare cable 6 and the rib-cast anchor 14 at the other end of the spare hole 11, thereby preventing damage to the spare cable 6 due to rubbing between the spare cable 6 and the rib-cast anchor 14.

[0047] However, the present invention is not limited to the above-described embodiments. For example, the arrangement of the external cable 5 is not limited to that shown in Figure 1, etc. Furthermore, the backup cable 6 does not have to be a bundle of multiple prestressing steel members, and is not particularly limited as long as it can introduce prestress into the box girder 1 through tension. The configuration of the anchor disk 22 as the fixing body and the configuration of the rib-cast anchor 14 as the receiving material are also not limited to those described above. Furthermore, the box girder 1 may be constructed of a composite type made of concrete and other materials.

[0048] In addition, in this embodiment, a case has been described in which the spare holes 11 are formed in the cross girders 3 of a PC box girder bridge. This allows the number of spare holes 11 in the cross girders 3 of the PC box girder bridge to be reduced, increasing the degree of freedom in the design of the cross girders 3, but the location of the spare holes 11 is not limited to this, and they may be formed in any concrete member of the box girder 1. For example, they may be members provided separately from the cross girders 3 inside or outside the box girder 1 for anchoring the external cables 5. Furthermore, the application of the present invention is not limited to PC box girder bridges, and it can be applied to bridge girders of various types of bridges.

[0049] Furthermore, in this embodiment, prestressing by the spare cable 6 is temporarily introduced when the outer cable 5 is replaced, but prestressing by the spare cable 6 may also be introduced for the purpose of additional reinforcement of the box girder 1 regardless of the replacement of the outer cable 5, and in this case too, the spare hole 11 can be used to secure the spare cable 6.

[0050] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the technical ideas disclosed in this application, and it is understood that these modifications and alterations also fall within the technical scope of the present invention. [Explanation of symbols]

[0051] 1, 100: Box girder 2: Bridge pier 3: Crossbeam 5, 5a, 5b: External cable 6: Spare cable 7, 7a, 7b: Fixing device 9: Manhole 11, 110: spare holes 12: Recess tube 13: Outer Trumpet 14, 14a, 14b: Rib cast anchor 17:Waterproof tape 18: Inner trumpet 19: Anti-friction spacer 20: Clamp 21: Spacer 22: Anchor disc 23: Wedge

Claims

1. A bridge having concrete members in its girders, Prestress in the bridge axis direction is introduced to the bridge girder by external cables arranged on both sides of the concrete member in the bridge axis direction, A preliminary hole used for fixing a preliminary cable for introducing prestress in the bridge axis direction to the bridge girder is provided so as to penetrate the concrete member in the bridge axis direction, A bridge characterized in that a support member for receiving an anchor for fixing a spare cable is provided at both ends of the spare hole.

2. The bridge girder is a box girder, 2. The bridge according to claim 1, wherein the concrete member is a cross beam provided inside the box girder.

3. The spare cable is fixed by the fixing body at one end of the spare hole, 3. The bridge according to claim 1, wherein a chafing prevention spacer is installed between the support member and the spare cable at the other end of the spare hole.

4. 3. The method for replacing an external cable in a bridge according to claim 1 or 2, a step of passing an end of a backup cable arranged on one side of the concrete member in the bridge axis direction through the backup hole, tensioning the end and fixing it to the other side of the concrete member in the bridge axis direction; a step of replacing an outer cable arranged on one side of the concrete member in the bridge axis direction with a new outer cable; releasing tension on the spare cable and removing it from the spare hole; a step of passing an end of the backup cable arranged on the other side of the concrete member in the bridge axis direction through the same backup hole and tensioning the end to fix it to one side surface of the concrete member in the bridge axis direction; replacing the outer cable disposed on the other side of the concrete member in the bridge axis direction with a new outer cable; A method for replacing an external cable, comprising:

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