Suspension material replacement method and suspension material replacement device

Abstract

The present invention provides a suspension material replacement method and a suspension material replacement device capable of replacing an existing suspension material with a new suspension material without causing vertical displacement of a suspension structure.　The tension of the lower end side of each existing hanger cable 4 is transferred to a second jack 40 and a first temporary suspension member 10 by applying tension between a part excluding the lower end side of each existing hanger cable 4 and the first temporary suspension member 10 by the second jack 40, the connection between the lower end side of each existing hanger cable 4 and the suspension structure 5 side is released, and tension is applied between the first temporary suspension member 10 and a second temporary suspension member 20 by a first jack 30 while reducing the tension between the part excluding the lower end side of each existing hanger cable 4 and the first temporary suspension member 10 applied by the second jack 40, so that all the tension of each existing hanger cable 4 is transferred to the first and second temporary suspension members 10, 20.

Description

Hanging material replacement method and hanging material replacement device

[0001] The present invention relates to a hanging member replacement method and a hanging member replacement device for replacing hanging members of a suspension bridge.

[0002] Generally, suspension bridges that are erected over straits, rivers, etc. are configured to suspend a suspended structure consisting of a deck slab, steel girders, etc., using hanger cables as suspension members connected to a main cable.

[0003] Many of these suspension bridges have been in operation for a long time, and each component may be suffering from deterioration such as corrosion. In particular, the hanger cables are made of steel with a smaller diameter than the main cables, and are subject to repeated loads from vibrations caused by vehicles traveling and wind pressure, which can cause deterioration and reduced durability. These deteriorated hanger cables must be replaced with new ones.

[0004] Conventionally, a method for replacing a hanger cable involves attaching a length-adjustable temporary hanger cable near the existing hanger cable to connect the main cable and the suspended structure, transferring the tension of the existing hanger cable to the temporary hanger cable, and then removing the temporary hanger cable and attaching a new hanger cable (see, for example, Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2019-143377

[0006] In conventional replacement methods, when transferring the tension of the existing hanger cable to the temporary hanger cable, tension must be applied to the temporary hanger cable using a jack or hoisting device until the existing hanger cable is released from tension. Since the existing hanger cable is stretched by the tension, it shortens by the amount of stretch when the tension is removed. This causes problems, such as vertical displacement of the suspended structure suspended by the temporary hanger cable, which can cause deformation of the suspended structure and significant fluctuations in the tension of other hanger cables.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a hanging member replacement method and hanging member replacement device that can replace existing hanging members with new hanging members without causing any vertical displacement of the suspended structure.

[0008] In order to achieve the above object, the present invention provides a hanging member replacement method for replacing an existing hanging member, the upper end of which is connected to a main cable side and the lower end of which is connected to a suspended structure side, with a new hanging member, using a first temporary hanging member connected to the suspended structure side, a second temporary hanging member connected to the main cable side, a first tensioning device capable of applying tension between the first temporary hanging member and the second temporary hanging member, and a second tensioning device capable of applying tension between the first temporary hanging member and a portion of the hanging member excluding the lower end side, and the second tensioning device applies tension between the first temporary hanging member and the portion of the existing hanging member excluding the lower end side. By applying tension between the first and second temporary hanging members, the tension on the lower end side of the existing hanging member is transferred to the second tensioning device and the first temporary hanging member, the connection between the lower end side of the existing hanging member, which is now in an untensioned state, and the suspended structure side is released, and while the tension between the part of the existing hanging member excluding the lower end side and the first temporary hanging member is reduced by the second tensioning device, tension is applied between the first and second temporary hanging members, thereby transferring all of the tension of the existing hanging member to the first and second temporary hanging members, and the existing hanging member, which is now in an untensioned state overall, is replaced with a new hanging member.

[0009] In addition, in order to achieve the above-mentioned object, the present invention provides a suspension material replacement device for replacing an existing suspension material, the upper end of which is connected to the main cable side and the lower end of which is connected to the suspended structure side, with a new suspension material, the device comprising: a first temporary suspension member connected to the suspended structure side; a second temporary suspension member connected to the main cable side; a first tensioning device capable of applying tension between the first temporary suspension member and the second temporary suspension member; and a second tensioning device capable of applying tension between the first temporary suspension member and a portion of the suspension material excluding the lower end side.

[0010] As a result, when removing the existing hanging material, tension is applied between the part of the existing hanging material excluding the lower end and the first temporary hanging member by the second tensioning device, thereby transferring the tension of the lower end of the existing hanging material to the second tensioning device and the first temporary hanging member, and the connection between the lower end of the existing hanging material, which is now in an untensioned state, and the hanging structure is released.The tension between the part of the existing hanging material excluding the lower end and the first temporary hanging member by the second tensioning device is reduced, while tension is applied between the first and second temporary hanging members by the first tensioning device, thereby transferring all of the tension of each existing hanging material to the first and second temporary hanging members.This makes it possible to transfer tension without changing the total tension between the hanging material and the first temporary hanging member and the tension between the first and second temporary hanging members.

[0011] According to the present invention, tension can be transferred without changing the total tension between the hanging member and the first temporary hanging member and the tension between the first and second temporary hanging members, so that vertical displacement of the suspended structure during tension transfer can be extremely reduced. This significantly reduces deformation of the suspended structure and fluctuations in the tension of other hanging members, which has the advantage of not affecting the durability of the suspended structure or the operation of passing vehicles.

[0012] Schematic side view of a suspension bridge showing one embodiment of the present invention; Overall side view of a hanging material replacement device; Side view of a main part of the hanging material replacement device; Front view of the hanging material replacement device as seen from the A-A arrow direction; Side view showing an existing hanger cable; Side view showing the hanging material replacement process; Side view showing the hanging material replacement process; Side view showing the hanging material replacement process; Side view showing the hanging material replacement process; Side view showing the hanging material replacement process;

[0013] 1 to 13 show an embodiment of the present invention, which illustrates a method for replacing suspension members of a suspension bridge.

[0014] The suspension bridge 1 shown in the figure is equipped with a main cable 3 stretched between main towers 2, and is configured to suspend a suspended structure 5 consisting of a deck slab, steel girders, etc., by a plurality of hanger cables 4 serving as suspension members connected to the main cable 3. In this embodiment, two hanger cables 4 are used at one suspension position.

[0015] As shown in FIG. 5, the hanger cable 4 is provided at its upper and lower ends with sockets 4a, and each socket 4a is provided at its end with a connecting portion 4b.

[0016] The upper end of the hanger cable 4 is connected to the main cable 3 by a connecting pin 4c that passes through a connecting hole 6a of a hanging fitting 6 attached to the main cable 3 and a connecting portion 4b of the socket 4a. A flange portion 4d is provided at the upper end of the lower socket 4a.

[0017] The lower end of the hanger cable 4 is connected to a connecting member 7 provided on the suspended structure 5 side. The connecting member 7 is made of a plate-shaped member that protrudes upward from the suspended structure 5 side, and has two connecting holes 7a provided at an interval in the bridge axis direction. In this case, the lower end of the hanger cable 4 is connected to the suspended structure 5 side by a connecting pin 4c that passes through the connecting hole 7a of the connecting member 7 and the connecting part 4b of the hanger cable 4.

[0018] As shown in Figures 2 to 4, the hanging material replacement device used in the hanging material replacement method of this embodiment comprises a first temporary hanging member 10 whose lower end is connected to the hanging structure 5 side, a second temporary hanging member 20 whose upper end is connected to the main cable 3 side, a pair of first jacks 30 as first tensioning devices that can apply tension between each of the first temporary hanging members 10 and each of the second temporary hanging members 20, a second jack 40 as a second tensioning device that can apply tension between the first temporary hanging member 10 and the flange portion 4d on the lower end side of each hanger cable 4, and a pair of winding devices 50 that wind up each of the second temporary hanging members 20.

[0019] The first temporary suspension member 10 comprises a pair of first beam sections 11 extending in the bridge axis direction of the suspension bridge 1, a plurality of support sections 12 extending downward from each of the first beam sections 11, and a pair of second beam sections 13 extending perpendicular to the bridge axis across the lower ends of each support section 12.

[0020] The first beam sections 11 are spaced apart from one another in the direction perpendicular to the bridge axis, and the support sections 12 are located closer to the center than both ends in the longitudinal direction (bridge axis direction).

[0021] Each support column 12 is provided in pairs on each first beam 11 at intervals in the bridge axis direction, and a connecting portion 12a is provided at the lower end of each support column 12 to connect the second beam 13 in a freely rotatable manner.

[0022] Each second beam section 13 has connecting sections 13a at both ends in the longitudinal direction (perpendicular to the bridge axis) to connect to the support section 12, and each connecting section 13a is rotatably connected to the connecting section 12a of the support section 12. Furthermore, a connecting section 13b that connects to the connecting member 7 of the suspended structure 5 is provided in the longitudinal center of each second beam section 13, and the second beam section 13 is connected to the suspended structure 5 by a connecting pin 13c that passes through the connecting section 13b and the second connecting hole 7b of the connecting member 7.

[0023] In addition, at both ends of each first beam section 11 in the bridge axis direction, a pair of third beam sections 14 are provided at intervals in the bridge axis direction, extending across the underside of each first beam section 11 in a direction perpendicular to the bridge axis, and at the center of each first beam section 11 in the bridge axis direction, a pair of fourth beam sections 15 are provided at intervals in the bridge axis direction, extending across the underside of each first beam section 11 in a direction perpendicular to the bridge axis.

[0024] Each second temporary hanging member 20 is made up of multiple well-known strands of PC steel wire, one end of which is connected to a connecting portion 21 that is connected to the main cable 3. One end of the second temporary hanging member 20 is connected to the main cable 3 by a connecting pin 21a that passes through a connecting hole 22a of a temporary hanging fitting 22 attached to the main cable 3 and the connecting portion 21. The other end of each second temporary hanging member 20 is wound up on a respective winding device.

[0025] Each first jack 30 is a well-known strand jack and is disposed at both longitudinal ends of each first beam portion 11 of the first temporary suspending member 10. The strand jack is a jack device that continuously feeds or rewinds the strand by repeatedly gripping and releasing the strand by hydraulically moving one of a pair of upper and lower clamp mechanisms capable of gripping the strand up and down, and is used for lifting and lowering heavy objects. Each first jack 30 is attached to the longitudinal center of each third beam portion 14 of the first temporary suspending member 10, and each has a second temporary suspending member 20 inserted therein.

[0026] The second jack 40 includes a plurality of hydraulic cylinders 41 and support members 42 that support the lower ends of the hydraulic cylinders 41, and the support members 42 are adapted to engage with the flange portions 4d of the hanger cable 4 from above. Each hydraulic cylinder 41 is adapted to press the corresponding fourth beam portion 15 of the first temporary hanging member 10 upward by its corresponding drive rod 41a.

[0027] Each winding device 50 is a well-known strand winding device installed on the suspended structure 5 and is configured to wind or unwind the second temporary suspension member 20 onto or from a rotatable reel 51 .

[0028] Next, the suspension member replacement method of this embodiment will be described with reference to Figures 6 to 13. In these figures, the tension between the main cable 3 and the suspended structure 5 is indicated by a thick line.

[0029] First, a new connecting member 60 is attached to the connecting member 7 of the suspended structure 5. The connecting member 60 has connecting holes 60a for connecting the first temporary hanging members 10, and the connecting members 60 are joined to both sides of the connecting member 7 in the bridge axis direction. Note that the joining of each connecting member 60 is performed by welding, but it may also be done by bolting.

[0030] Next, a hanging member replacement device is installed on the suspended structure 5. That is, as shown in Figures 6 and 7, each connecting portion 13b of the first temporary hanging member 10 is connected to the connecting hole 60a of each connecting member 60 on the suspended structure 5 side with the connecting pin 13c, and the support member 42 of the second jack 40 is engaged from above with the flange portion 4d of each existing hanger cable 4. Next, temporary hanging fittings 22 are attached to two locations in the bridge axis direction of the main cable 3, and each second temporary hanging member 20 unwound from each reeling device 50 is reeled out upward by each first jack 30, and one end of each second temporary hanging member 20 is connected to each temporary hanging fitting 22.

[0031] Next, by using each first jack 30 to pull down each second temporary hanging member 20 relative to the first temporary hanging member 10, a small tension is applied between the first temporary hanging member 10 and each second temporary hanging member 20, and the first temporary hanging member 10 and the second temporary hanging member 20 are tensioned.

[0032] After this, tension is applied between the first temporary hanging member 10 and the flange portion 4d of each hanger cable 4 by the second jack 40, thereby transferring the tension on the lower end side of each hanger cable 4 (the portion from the flange portion 4d to the connecting portion 4b) to the second jack 40 and the first temporary hanging member 10, as shown in Figure 8.

[0033] This creates a reaction-free state between the connecting portion 4b at the lower end of each hanger cable 4 and the connecting member 7 of the suspended structure 5, so the connecting pin 4c is removed and the connection between the lower end of each hanger cable 4 and the connecting member 7 is released.

[0034] Next, as shown in Figure 9, by gradually lowering the drive rods 41a of each hydraulic cylinder 41 of the second jack 40, the tension on the first temporary hanging member 10 and each existing hanger cable 4 by the second jack 40 is reduced, while the second temporary hanging member 20 is gradually pulled down by the first jack 30, thereby applying tension between the first temporary hanging member 10 and the second temporary hanging member 20, and all of the tension on each existing hanger cable 4 is transferred to the first and second temporary hanging members 10, 20.

[0035] As a result, the tension is transferred without changing the sum of the tension between each hanger cable 4 and the first temporary hanging member 10 and the tension between the first and second temporary hanging members 10, 20. In this case, each hanger cable 4 that had been stretched due to tension becomes untensioned as a whole and shrinks, becoming shorter by length L than when tensioned, as shown in Figure 9. At this time, because the connection between the lower end of each hanger cable 4 and the connecting member 7 is released, the change in length L of each hanger cable 4 does not cause any vertical displacement on the suspended structure 5 side.

[0036] Next, the connecting pins 4c connecting the upper end connecting portions 4b of each existing hanger cable 4, which is now in a tension-free state, to the hanging fittings 6 are removed, and each existing hanger cable 4 is removed from the hanging fittings 6 as shown in Figure 10.

[0037] 11, the upper ends of the new pair of hanger cables 8 are connected to the main cable 3. At this time, the connecting portions 8b of the sockets 8a of each hanger cable 8 are connected to the hanging fittings 6 by connecting pins 8c.

[0038] Next, as shown in Figure 12, the first temporary hanging member 10 is gradually pushed up by the drive rod 41a of each hydraulic cylinder 41 of the second jack 40, and while tension is applied between the first temporary hanging member 10 and the flange portion 8d of each hanger cable 8, the second temporary hanging member 20 is gradually pulled up by the first jack 30, thereby reducing the tension between the first temporary hanging member 10 and the second temporary hanging member 20 and transferring all of the tension between the first temporary hanging member 10 and the second temporary hanging member 20 to the portion excluding the lower end side of each hanger cable 8 (the portion from the flange portion 8d to the connecting portion 8b), the second jack 40, and the first temporary hanging member 10.

[0039] As a result, each hanger cable 8 is stretched by a length L due to tension from its untensioned state, and the connecting portion 8b at the lower end of each hanger cable 8 is connected to the connecting member 7 of the suspended structure 5 by the connecting pin 8c.

[0040] After this, as shown in Figure 13, the drive rod 41a of each hydraulic cylinder 41 of the second jack 40 is lowered to release the tension on the first temporary hanging member 10 by the second jack 40, and the tension on the first temporary hanging member 10 is transferred to the entirety of each hanger cable 8.

[0041] After replacing each existing hanger cable 4 with a new hanger cable 8 in the above manner, the suspension material replacement device is moved to another suspension position, and the next suspension material replacement work is carried out in the same manner as described above. At this time, the length of the hanger cables 4 of the suspension bridge 1 varies depending on the suspension position, but by winding or unwinding each second temporary suspension member 20 with each winding device 50, the length of each second temporary suspension member 20 is adjusted according to the length of the hanger cable 4.

[0042] As described above, according to this embodiment, when removing each existing hanger cable 4, tension is applied between the first temporary suspension member 10 and the portion of each existing hanger cable 4 excluding the lower end side by the second jack 40, thereby transferring the tension on the lower end side of each existing hanger cable 4 to the second jack 40 and the first temporary suspension member 10, releasing the connection between the lower end side of each existing hanger cable 4, which is now in a tension-free state, and the suspended structure 5 side, and removing each existing hanger cable 4 by the second jack 40. By applying tension between the first temporary hanging member 10 and the second temporary hanging member 20 with the first jack 30 while reducing the tension between the portion of the cable 4 excluding the lower end side and the first temporary hanging member 10, all of the tension in each existing hanger cable 4 is transferred to the first and second temporary hanging members 10, 20, so that the tension can be transferred without changing the total of the tension between each hanger cable 4 and the first temporary hanging member 10 and the tension between the first and second temporary hanging members 10, 20. This makes it possible to extremely reduce vertical displacement of the suspended structure 5 during tension transfer, thereby significantly suppressing deformation of the suspended structure 5 and fluctuations in the tension of other hanger cables, with the advantage of not affecting the durability of the suspended structure 5 or the running of passing vehicles.

[0043] Furthermore, when installing new hanger cables 8, each of the existing hanger cables 4, which have been put into a tension-free state as a whole, is replaced with a new hanger cable 8, and then tension is applied between the first temporary hanging member 10 and the part of each new hanger cable 8 excluding the lower end side by the second jack 40, while the tension between the first temporary hanging member 10 and the second temporary hanging member 20 is reduced by the first jack 30. This releases the tension of the first and second temporary hanging members 10, 20 from the part of each new hanger cable 8 excluding the lower end side by the second jack 40. 0 and the first temporary hanging member 10, and after connecting the lower end of each new hanger cable 8 to the suspended structure 5, the tension between the first temporary hanging member 10 and the part of each new hanger cable 8 excluding the lower end thereof is released by the second jack 40, thereby transferring the tension of the first temporary hanging member 10 to the entire new hanger cable 8.Therefore, as described above, the tension can be transferred without changing the total tension between each hanger cable 8 and the first temporary hanging member 10 and the tension between the first and second temporary hanging members 10, 20.

[0044] Furthermore, while the first jack 30 applies a small tension between the first temporary hanging member 10 and the second temporary hanging member 20 to tension the first temporary hanging member 10 and the second temporary hanging member 20, the second jack 40 applies tension between the first temporary hanging member 10 and the second temporary hanging member 20 while reducing the tension between the first temporary hanging member 10 and the portion of each existing hanger cable 4 excluding the lower end side.Therefore, when the tension applied by the second jack 40 begins to be reduced, the descent of the first temporary hanging member 10 can be regulated by the tension between the first temporary hanging member 10 and the second temporary hanging member 20, and vertical displacement during tension transfer can be effectively prevented.

[0045] Furthermore, because a strand is used as the second temporary hanging member 20 and a strand jack is used as the first jack 30, the length of the second temporary hanging member 20 (strand) from the main cable 3 side to the first jack 30 can be changed according to the length of the hanger cable 4. This eliminates the need to prepare temporary hanger cables of different lengths for each hanger cable 4 at each hanging position, thereby reducing the production costs and time required for producing many different types of temporary hanger cables.

[0046] In this case, after replacing each existing hanger cable 4 with a new hanger cable 8, the hanging material replacement device is moved to another hanging position and the length of each second temporary hanging member 20 is adjusted according to the length of the hanger cable 4 at the other hanging position, so that the same hanging material replacement device can be used even at hanging positions where the hanger cable lengths are different, thereby making the hanger cable replacement work extremely efficient.

[0047] In the above embodiment, the second jack 40 is configured by a plurality of hydraulic cylinders 41, but a center hole jack may also be used.

[0048] Furthermore, in the above embodiment, two hanger cables 4, 8 are provided at each suspension position, but one hanger cable may be provided at each suspension position.

[0049] Furthermore, in the above embodiment, the existing hanger cable 4 is replaced with a new hanger cable 8 of the same configuration, but the new hanger cable may be replaced with one having a different configuration from the existing hanger cable 4. For example, by using a hanger cable itself equipped with a length adjustment mechanism and a tension introduction mechanism, the tension of the first and second temporary hanging members 10, 20 may be transferred to the new hanger cable without using the second jack 40.

[0050] Furthermore, in the above embodiment, the new connecting member 60 is attached to the connecting member 7 , but the new connecting member 60 may be attached directly to the suspended structure 5 .

[0051] Furthermore, in the above embodiment, a winding device 50 for winding up the second temporary hanging member 20 is shown to be installed on the suspended structure 5, but if the length of the second temporary hanging member 20 is short, the excess length of the second temporary hanging member 20 may be stretched and placed directly on the suspended structure 5 without using the winding device 50.

[0052] Furthermore, the above embodiment is an example of the present invention, and the present invention is not limited to the above embodiment.

[0053] 1...Suspension bridge, 3...Main cable, 4...Hanger cable, 5...Suspension structure, 7...Connecting member, 8...Hanger cable, 10...First temporary suspension member, 20...Second temporary suspension member, 30...First jack, 40...Second jack, 50...Winding device.

Claims

1. A method for replacing an existing suspension member whose upper end is connected to the main cable side and whose lower end is connected to the suspended structure side with a new suspension member, comprising: using a first temporary suspension member connected to the suspended structure side; a second temporary suspension member connected to the main cable side; a first tensioning device capable of applying tension between the first temporary suspension member and the second temporary suspension member; and a second tensioning device capable of applying tension between the first temporary suspension member and a portion of the suspension member excluding the lower end side; applying tension between the first temporary suspension member and a portion of the existing suspension member excluding the lower end side with the second tensioning device, thereby transferring the tension on the lower end side of the existing suspension member to the second tensioning device and the first temporary suspension member; releasing the connection between the lower end side of the existing suspension member, which is now in an untensioned state, and the suspended structure side; A method for replacing a hanging material, characterized by applying tension between the first temporary hanging member and the second temporary hanging member using the first tensioning device while reducing the tension between the part of the existing hanging member excluding the lower end side using the second tensioning device, thereby transferring all of the tension of the existing hanging member to the first and second temporary hanging members, and replacing the existing hanging member, which is now in an untensioned state, with a new hanging member.

2. A method for replacing a suspension member as described in claim 1, characterized in that, after replacing the existing suspension member with a new one, the tension of the first and second temporary suspension members is transferred to the part of the new suspension member excluding its lower end, the second tensioning device, and the first temporary suspension member by applying tension between the part of the new suspension member excluding its lower end and the first temporary suspension member using the second tensioning device while reducing the tension between the first temporary suspension member and the second temporary suspension member using the first tensioning device, and after connecting the lower end of the new suspension member to the suspended structure, the tension of the first temporary suspension member is transferred to the entire new suspension member by releasing the tension applied by the second tensioning device between the part of the new suspension member excluding its lower end and the first temporary suspension member.

3. A method for replacing a suspension member as described in claim 1, characterized in that, while a small tension is applied between the first temporary suspension member and the second temporary suspension member by the first tensioning device to tension the first temporary suspension member and the second temporary suspension member, tension is applied between the first temporary suspension member and the second temporary suspension member by the first tensioning device while reducing the tension applied by the second tensioning device between the first temporary suspension member and the part of the existing suspension member excluding the lower end side.

4. A method for replacing a hanging material according to claim 1, characterized in that the length of the second temporary hanging member is changed according to the length of the hanging material.

5. A method for replacing a hanging member according to claim 4, characterized in that a strand and a strand jack are used as the second temporary hanging member and the first tension applying device.

6. A suspension material replacement device for replacing an existing suspension material, the upper end of which is connected to the main cable side and the lower end of which is connected to the suspended structure side, with a new suspension material, characterized in that it comprises: a first temporary suspension member connected to the suspended structure side; a second temporary suspension member connected to the main cable side; a first tensioning device capable of applying tension between the first temporary suspension member and the second temporary suspension member; and a second tensioning device capable of applying tension between the first temporary suspension member and a portion of the suspension material excluding the lower end side.

7. A hanging material replacement device according to claim 6, characterized in that the length of the second temporary hanging member can be changed according to the length of the hanging material.

8. A hanging material replacement device according to claim 7, characterized in that the second temporary hanging member and the sixth tension applying device are constituted by a strand and a strand jack.

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