How to replace bearings

Abstract

To provide a bearing replacement method capable of contributing to shortening the construction period for bearing replacement work. [Solution] In a bridge having a lower steel member 60, which is a steel member that constitutes at least part of the lower structure, an upper steel member 62, which is a steel member that constitutes at least part of the superstructure, and a bearing 50 that is arranged between the lower steel member 60 and the upper steel member 62 and transmits force between the lower steel member 60 and the upper steel member 62, this is a bearing replacement method for replacing the existing bearing 50 with a new bearing, where the existing bearing 50 is connected onto the lower steel member 60 by welding, and the method includes a welded joint release process for cold cutting the welded joint between the existing bearing 50 and the lower steel member 60 to release the connection between the existing bearing 50 and the lower steel member 60.

Description

[Technical field]

[0001] The present invention relates to a bearing replacement method, and more particularly to a bearing replacement method that can contribute to shortening the construction period for bearing replacement work. [Background technology]

[0002] In recent years, bridge preservation work has become more common in many areas, and one of the most common types of bridge preservation work is bearing replacement work.

[0003] In many cases, the lower shoe of an existing bearing installed on the top of a steel pier is attached to the top surface of the steel pier by fillet welding, and when replacing an existing bearing installed on the top of a steel pier with a new bearing, it is necessary to release the connection between the existing bearing and the steel pier. As a method for removing existing welds between steel members in a bridge, gouging is generally used as described in Non-Patent Document 1.

[0004] However, in the gouging described in Non-Patent Document 1, the weld bead of the sole plate fixed to the steel main girder by welding is removed by gouging, and heat from the gouging is input to the steel main girder. When the existing weld between the existing bearing and the top face of the steel pier is removed by gouging as in Non-Patent Document 1, there is a risk that the steel pier will become too hot due to the heat from the gouging. The strain-stress curve of steel material is shown in Figure 7 (horizontal axis is strain (mm) and vertical axis is stress (N / mm 2 ), the strain-stress curve of steel material is significantly different at room temperature (shown by the solid line in Fig. 7) and at high temperatures (shown by the two-dot chain line in Fig. 7), and the yield point drops significantly at high temperatures. For this reason, if the existing weld between the existing bearing and the top surface of the steel pier is removed by gouging when the existing bearing is connected to the steel main girder (the load due to the weight of the steel main girder is applied to the top surface of the steel pier via the existing bearing), the heat from the gouging will heat up the steel pier, significantly lowering the yield point of the steel material that makes up the steel pier, and there is a risk that the steel pier will buckle due to the load due to the weight of the steel main girder.

[0005] On the other hand, if the load due to the weight of the steel main girder is not applied to the steel pier, buckling will not occur in the steel pier even if a certain amount of heat is input into the steel pier due to gouging.

[0006] Therefore, the conventional practice is to jack up the steel girder to cut the edge between the steel girder and the support, so that the load due to the weight of the steel girder is not applied to the steel pier, and then remove the existing weld between the existing support and the top surface of the steel pier by gouging. The steel girder and the existing support are generally connected by bolts using set bolts, and the connection between the steel girder and the existing support can be released by removing the set bolts, and the edge between the steel girder and the support can be cut by removing the set bolts and jacking up the steel girder. If the edge between the steel girder and the support is cut, even if the yield point of the steel pier is lowered by the heat of gouging, the load due to the weight of the steel girder itself is not transmitted to the steel pier, so the steel pier will not buckle.

[0007] An example of a conventional process in which the steel girder is jacked up to cut the edge between the steel girder and the support, and then the existing welded joint between the existing support and the top surface of the steel pier is removed by gouging is shown in the flowchart of Figure 8 and in the process chart of Figure 9. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] "7. Introduction to basic types of work and points to consider in maintenance work - for those who want to become maintenance engineers in the future", Japan Bridge Construction Association Bridge Technology Presentation Materials, Japan Bridge Construction Association Maintenance Committee Maintenance Technology Subcommittee, FY2012 Technology Presentation, [surveyed on December 18, 2023],<https: / / www.jasbc.or.jp / images / imageparts / title / release / ronbun / 2012 / H24_07.pdf> , Page 7-14, right column, lines 10-14 Summary of the Invention [Problem to be solved by the invention]

[0009] In the conventional method of jacking up the steel girder to cut the edge between the steel girder and the support, and then removing the existing welded portion by gouging, as shown in Figs. 8 and 9, before removing the existing welded portion 52 (see Fig. 3) by gouging and releasing the welded connection of the existing support 50 (see Fig. 3) (step S104), the steel bracket 30 (see Fig. 6) is manufactured in the factory (step S101), the steel bracket 30 is installed on the steel pier 60 (see Fig. 3), and the steel main girder 62 is installed. (see Figure 3) was prepared on site (step S102, see Figure 9), and the steel main girder 62 was jacked up (step S103). The work of severing the connection between the steel main girder 62 and the existing bearing 50 was not completed until the process of removing the welded joint of the existing bearing 50 (step S104), in which the existing welded portion 52 was removed by gouging, was completed. This resulted in a waiting period, which extended the construction period for the bearing replacement work.

[0010] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a bearing replacement method that can contribute to shortening the construction period for bearing replacement work.

[0011] In Figures 8 and 9, step S105 is a process of removing the existing bearing 50, step S106 is a process of placing the new bearing in a predetermined position, step S107 is a process of fixing the new bearing by on-site welding, and step S108 is a process of jacking down the steel main girder 62 and connecting the steel main girder 62 to the new bearing. [Means for solving the problem]

[0012] The present invention is an invention that solves the above-mentioned problems, and provides a bearing replacement method as described below.

[0013] In other words, a first aspect of the bearing replacement method of the present invention is a bearing replacement method for replacing an existing bearing with a new bearing in a bridge having a lower steel member which is a steel member constituting at least a part of the substructure, an upper steel member which is a steel member constituting at least a part of the superstructure, and a bearing which is arranged between the lower steel member and the upper steel member and transmits force between the lower steel member and the upper steel member, wherein the existing bearing is connected onto the lower steel member by welding, and the bearing replacement method includes a welded joint release step of performing cold cutting on the welded joint portion between the existing bearing and the lower steel member to release the connection between the existing bearing and the lower steel member.

[0014] Here, "lower steel members which are steel members constituting at least a part of the lower structure" includes not only steel members which constitute at least a part of the lower structure, but also steel members fixed to the lower structure, and "upper steel members which are steel members constituting at least a part of the superstructure" includes not only steel members which constitute at least a part of the superstructure, but also steel members fixed to the superstructure.

[0015] In the present application, cold cutting refers to cutting a metal to be cut without melting it by heating, and cutting also includes making a cut in a part to be cut while leaving all or part of the part to be cut.

[0016] A second aspect of the bearing replacement method of the present invention is a bearing replacement method of the first aspect, characterized in that it further includes a jacking-up process of jacking up the upper steel member so as to sever the connection between the upper steel member and the existing bearing, and the welded joint release process is carried out before the jacking-up process.

[0017] Here, in the jacking up process, "jacking up the upper steel member so as to sever the connection between the upper steel member and the existing support" does not only mean the case where a jack directly contacts the upper steel member that is in contact with the existing support and jacks up the upper steel member to sever the connection between the upper steel member and the existing support, but also the case where the jack does not directly contact the upper steel member that is in contact with the existing bearing, but rather contacts a bracket separately attached to the upper steel member, or another upper steel member or a bracket attached thereto, and jacks up the upper steel member to sever the connection between the upper steel member and the existing support.

[0018] A third aspect of the bearing replacement method of the present invention is a bearing replacement method according to the first or second aspect, characterized in that the cold cutting performed in the welded joint release process is performed so as to remove at least a portion of the welded joint portion.

[0019] A fourth aspect of the bearing replacement method according to the present invention is the bearing replacement method according to the third aspect, characterized in that the cold cutting is performed using a carbide burr.

[0020] A fifth aspect of the bearing replacement method according to the present invention is the bearing replacement method of the fourth aspect, characterized in that the shape of the carbide bar is such that its outer diameter becomes smaller in a region near the tip of the carbide bar as it approaches the tip.

[0021] A sixth aspect of the bearing replacement method according to the present invention is the bearing replacement method according to the third aspect, characterized in that the cold cutting is performed using an end mill.

[0022] A seventh aspect of the bearing replacement method of the present invention is a bearing replacement method according to the first or second aspect, characterized in that the cold cutting performed in the welded joint release process is performed so as to create a cut in at least a portion of the welded joint.

[0023] An eighth aspect of the bearing replacement method of the present invention is a bearing replacement method according to the second aspect, characterized in that it includes a jack-up preparation step prior to the jack-up step, in which the upper steel member is prepared for jacking up, and the welded joint release step is carried out in parallel with the jack-up preparation step.

[0024] A ninth aspect of the bearing replacement method of the present invention is the bearing replacement method of the eighth aspect, characterized in that the jack-up preparation process includes a steel bracket production process of producing a steel bracket to be used when jacking up the upper steel member.

[0025] A tenth aspect of the bearing replacement method of the present invention is a bearing replacement method according to the eighth or ninth aspect, characterized in that the jack-up preparation process includes a jack-up site preparation process of making preparations on site for jacking up the upper steel member.

[0026] An eleventh aspect of the bearing replacement method of the present invention is a bearing replacement method according to any one of the first to tenth aspects, characterized in that the lower steel member is a steel pier or a steel bracket attached to the side of a pier.

[0027] A twelfth aspect of the bearing replacement method of the present invention is a bearing replacement method according to any one of the first to eleventh aspects, characterized in that the upper steel member is a steel bridge girder or a steel cross girder. Effect of the Invention

[0028] According to the present invention, it is possible to provide a bearing replacement method that can contribute to shortening the construction period for bearing replacement work. [Brief description of the drawings]

[0029] [Figure 1]1 is a flowchart showing the steps of a bearing replacement method according to an embodiment of the present invention. [Diagram 2] Process chart of the bearing replacement method according to the embodiment of the present invention [Diagram 3] FIG. 1 is a perspective view showing a typical process of removing a welded joint of an existing bearing 50 by cold cutting, which is a typical process of a bearing replacement method according to an embodiment of the present invention; [Figure 4] FIG. 1 is a front view showing a state in which cold cutting is performed on an existing welded portion 52 by a carbide bar 12 in a welded joint release process of a support replacement method according to an embodiment of the present invention. [Diagram 5] FIG. 1 is a front view showing a state in which cold cutting is performed on an existing welded portion 52 by an end mill 22 in a welded joint release process of a support replacement method according to an embodiment of the present invention; [Figure 6] FIG. 1 is a perspective view showing a state in which preparations for jacking up a steel girder 62 have been completed in a support replacement method according to an embodiment of the present invention. [Figure 7] A diagram showing the strain-stress curves of steel at room temperature and at high temperatures. [Figure 8] 1 is a flowchart showing an example of a procedure for a conventional bearing replacement method using gouging. [Figure 9] Example of a process diagram for a conventional bearing replacement method using gouging DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, the bearing replacement method according to the embodiment of the present invention will be described in detail with reference to the drawings. In the description of the bearing replacement method according to the present embodiment, the case where an existing bearing 50 (see FIG. 3) welded to the top surface of a steel pier 60 (see FIG. 3) is replaced with a new bearing will be described. The existing bearing 50 has a lower shoe 50A (see FIG. 4) welded to the top surface of the steel pier 60 via an existing welded portion 52 (see FIG. 3), which is a welded joint portion by fillet welding. In the following description of the bearing replacement method according to the embodiment of the present invention, it is assumed that the existing bearing 50 is welded to the top surface of the steel pier 60 via the existing welded portion 52 and installed on the top of the steel pier 60 without using any joint other than welding.

[0031] (1) A method for replacing a support according to an embodiment of the present invention FIG. 1 is a flowchart showing the steps of the bearing replacement method according to an embodiment of the present invention, FIG. 2 is a process chart of the bearing replacement method according to an embodiment of the present invention, FIG. 3 is an oblique view showing a typical process of the bearing replacement method according to an embodiment of the present invention, in which a welded joint release process of an existing bearing 50 by cold cutting is being performed, FIG. 4 is a front view showing a typical process of the bearing replacement method according to an embodiment of the present invention, in which cold cutting is being performed on an existing welded portion 52 by a carbide bar 12 in the welded joint release process of the bearing replacement method according to an embodiment of the present invention, FIG. 5 is a front view showing a typical process of the bearing replacement method according to an embodiment of the present invention, in which cold cutting is being performed on an existing welded portion 52 by an end mill 22 in the welded joint release process of the bearing replacement method according to an embodiment of the present invention, and FIG. 6 is an oblique view showing a typical state in which preparations for jacking up a steel main girder 62 have been completed in the bearing replacement method according to an embodiment of the present invention.

[0032] As shown in the flow chart of FIG. 1 and the process chart of FIG. 2, the support replacement method according to the embodiment of the present invention has eight main steps, steps S1 to S8.

[0033] (Step S1) In the bearing replacement method according to the embodiment of the present invention, first, in this step S1, manufacturing of the steel bracket 30 in a factory is started. The steel bracket 30 is a member used when jacking up the steel main girder 62 and is a member that is required early in implementing this embodiment, and the period required to manufacture the steel bracket 30 is about three months as shown in step S1 of the process chart in Fig. 2, which is longer than the periods required for other steps, so in the bearing replacement method according to this embodiment, manufacturing of the steel bracket 30 in a factory is performed in this step S1, which is the first step of the bearing replacement method according to this embodiment.

[0034] (Step S2) This step S2 is a process of removing the existing welded portion 52 by cold cutting to release the connection between the existing bearing 50 and the steel pier 60, and the state in which this step S2 is being performed is shown diagrammatically in Figure 3. The period required for this step S2 is about 0.5 months, as shown in the process chart in Figure 2.

[0035] As described above, in this application, cold cutting refers to cutting the metal to be cut without melting it by heating. As shown in Figures 3 and 4, in this embodiment, a portable grinder 10 is used to perform cold cutting. In detail, cold cutting is performed on the existing welded portion 52 with a carbide bar 12 attached to the tip of the rotating main shaft of the portable grinder 10, and the existing welded portion 52 is removed, and the welded connection between the existing bearing 50 and the steel pier 60 is released.

[0036] The shape of the carbide burr 12 is preferably such that it is easy to cut the existing welded portion 52. Specifically, for example, as shown in FIG. 4, the shape of the carbide burr 12 is preferably such that the outer diameter of the portion where the target object is cut becomes smaller in the region near the tip of the carbide burr 12 toward the tip.

[0037] In this step S2, the portable grinder 10 is used when cold cutting the existing welded portion 52, but other cutting tools can also be used, for example, a portable milling machine 20 can be used as shown in Fig. 5. In this case, for example, an end mill 22 is attached to the spindle of the portable milling machine 20, and the existing welded portion 52 is cold cut using the end mill 22 to remove the existing welded portion 52, and the welded connection between the existing bearing 50 and the steel pier 60 is released.

[0038] This step S2 is started after the start or before the end of the step S1 (factory manufacturing process of the steel bracket 30), and this step S2 is carried out in parallel with the step S1 (factory manufacturing process of the steel bracket 30), and this step S2 is completed before or at the same time as the end of the step S1 (factory manufacturing process of the steel bracket 30). In this way, when the manufacturing of the steel bracket 30 at the factory is completed in the step S1, it is possible to immediately move to the next step S3 of installing the steel bracket 30 on the steel pier 60, and the period of about 0.5 months required for this step S2 does not affect the length of the overall construction period using the bearing replacement method according to this embodiment, as shown in the process chart in Figure 2. In other words, the overall construction period can be shortened by the approximately 0.5 month period required for step S2 compared to the conventional method of gouging (as shown in the schedule in Figure 9, in the conventional method, the process of removing the welded joint of the existing bearing 50 by gouging (step S104) cannot be carried out in parallel with the process of manufacturing the steel bracket 30 at the factory (step S101), and the construction period for gouging affects the overall construction period, so the overall construction period for the conventional method of gouging is approximately 7 months).The overall construction period for the bearing replacement method of this embodiment is approximately 6.5 months, as shown in the schedule in Figure 2.

[0039] (Step S3) This step S3 is a process in which, after cold cutting is performed on the existing welded portion 52 in step S2 to release the welded connection between the existing bearing 50 and the steel pier 60, the following three steps (S3-a, S3-b, S3-c) are performed on site to prepare for jacking up the steel main girder 62 (see Figure 6).

[0040] S3-a) The steel bracket 30 produced in step S1 is attached to the side of the steel pier 60 so that it is positioned below the steel main girder 62, a sander material 32 for height adjustment is placed on the upper surface of the attached steel bracket 30, and a hydraulic jack 34 is placed on top of the placed sander material 32.

[0041] S3-b) A reinforcing member 62A is attached to the portion of the steel main girder 62 above the hydraulic jack 34 to prevent defects such as local deformation from occurring in the portion of the steel main girder 62 above the hydraulic jack 34 due to the load applied during jacking up.

[0042] S3-c) Remove the set bolt 54 (see Figures 4 and 5) that connects the upper shoe 50B (see Figures 4 and 5) of the existing support 50 to the lower flange of the steel main girder 62, and release the connection between the existing support 50 and the steel main girder 62.

[0043] The state where preparations for jacking up the steel main girder 62 are complete (the state where this step S3 is completed) is shown in Fig. 6. The period required for this step S3 is about one month, as shown in the schedule in Fig. 2.

[0044] Incidentally, the manner in which the steel main girder 62 is jacked up is not limited to the manner shown in Figure 6. If it is difficult to attach the steel bracket 30 to the side of the steel pier 60 so that it is positioned below the steel main girder 62, for example, steel brackets can be attached to both sides of the web of the steel main girder 62, and a hydraulic jack 34 can be placed between the steel brackets attached to both sides of the web of the steel main girder 62 and the top surface of the steel pier 60 to jack up the steel main girder 62.

[0045] (Step S4) After completing the preparation for jacking up the steel girder 62 in step S3, in step S4, the cylinder of the hydraulic jack 34 arranged in step S3 is extended upward to jack up the steel girder 62, and the edge is cut between the existing support 50 and the sole plate 56 attached to the underside of the steel girder 62. As described in S3-c, the set bolt 54 is removed to release the connection between the existing support 50 and the steel girder 62, so when the steel girder 62 is jacked up, the edge is cut between the upper shoe 50B (see Figs. 4 and 5) of the existing support 50 and the sole plate 56 attached to the underside of the steel girder 62 (the sole plate 56 is attached to the underside of the steel girder 62 via the existing welded portion 58). The period required for step S4 is about 0.5 months, as shown in the schedule in Fig. 2.

[0046] When jacking up the steel main girder 62, the entire superstructure of the bridge may be jacked up, but if it is possible to jack up only a portion of the superstructure including the steel main girder 62, or only one steel main girder 62, then depending on the situation, only a portion of the superstructure including the steel main girder 62, or only one steel main girder 62 may be jacked up.

[0047] (Step S5) In step S2, the welded connection between the existing bearing 50 and the steel pier 60 is released, and in step S4, the steel main girder 62 is jacked up to cut the edge between the upper shoe 50B of the existing bearing 50 and the sole plate 56 attached to the underside of the steel main girder 62, making it possible to remove the existing bearing 50.

[0048] Therefore, in this step S5, the existing bearing 50 is removed. A commonly used known method can be used when removing the existing bearing 50 in this step S5. The time required for this step S5 is about 0.5 months, as shown in the schedule in FIG. 2.

[0049] (Step S6) After removing the existing bearing 50 in step S5, in step S6, a new bearing (not shown) is placed in a predetermined position on the top end of the steel pier 60. When placing the new bearing (not shown) in a predetermined position on the top end of the steel pier 60 in step S6, a commonly used known method can be used. The time required for step S6 is about 0.5 months, as shown in the schedule in Figure 2.

[0050] (Step S7) After placing the new bearing (not shown) at a prescribed position on the top end of the steel pier 60 in step S6, the new bearing (not shown) is welded to the top end of the steel pier 60 by on-site welding in step S7, and the new bearing (not shown) is fixed to the top end of the steel pier 60. When welding and fixing the new bearing (not shown) to the top end of the steel pier 60 by on-site welding in step S7, a commonly used known method can be used. The time required for step S7 is about 0.5 months, as shown in the process chart in Figure 2.

[0051] In steps S5, S6, and S7, the existing bearing 50 is removed and the new bearing is placed and fixed onto the top of the steel pier 60. Therefore, steps S5, S6, and S7 can be considered together as a bearing replacement process in which the existing bearing 50 is replaced with the new bearing.

[0052] (Step S8) In step S7, the new bearing (not shown) is welded and fixed to the top end of the steel pier 60 by on-site welding, and then the steel main girder 62 is jacked down. Then, the lower flange of the jacked-down steel main girder 62 is connected to the upper shoe of the new bearing (not shown) with a set bolt 54. When carrying out the above-mentioned items in step S8, a commonly used known method can be used. The period required for step S8 is about 0.5 months, as shown in the schedule in Figure 2.

[0053] (2) Effects of the bearing replacement method according to the embodiment of the present invention In step S2 (process of removing the welded joint of the existing bearing 50) of the bearing replacement method of this embodiment, the existing welded portion 52 is removed by cold cutting to remove the welded joint between the existing bearing 50 and the top face of the steel pier 60. Therefore, step S2 (process of removing the welded joint of the existing bearing 50) of the bearing replacement method of this embodiment can be performed in a state where the load due to the weight of the steel main girder 62 is applied to the top face of the steel pier via the existing bearing, without cutting the edge between the steel main girder 62 and the existing bearing 50, and can be performed in parallel with step S1, which is a process of manufacturing the steel bracket 30, a component necessary for jacking up, in the factory. In the bearing replacement method of this embodiment, step S2 (process of removing the welded joint of the existing bearing 50) is completed before or at the same time as the completion of step S1 (process of manufacturing the steel bracket 30 in the factory).

[0054] Therefore, by using the bearing replacement method according to this embodiment, the overall construction period required to replace the existing bearing 50 welded to the top surface of the steel pier 60 with a new bearing can be shortened by about 0.5 months to about 6.5 months (see FIG. 2) compared to the overall construction period required when the conventional method of gouging is used (about 7 months) (see FIG. 9).

[0055] (3) Supplementary Information In the above explanation of "(1) Bearing replacement method according to the embodiment of the present invention", the case where the existing bearing 50 arranged under the steel main girder 62 is welded to the top surface of the steel pier 60 via the existing welded part 52 is taken up and explained, but the application of the bearing replacement method according to the present invention is not limited to this, and the application of the bearing replacement method according to the present invention is also broadly applicable to the following cases, that is, the case where an existing bearing that is arranged between a lower steel member that is a member that constitutes at least a part of the substructure or is fixed to the substructure and an upper steel member that is a member that constitutes at least a part of the superstructure or is fixed to the superstructure and transmits force between the lower steel member and the upper steel member is welded to the lower steel member and installed on the lower steel member. An example of a member that is fixed to the substructure and becomes the lower steel member is a steel bracket attached to the side of the pier. In addition, the steel cross girders connecting adjacent steel main girders 62 can be considered to be members that constitute at least a part of the superstructure or members that are fixed to the superstructure, and are included in the upper steel members.

[0056] In addition, in the explanation of "(1) Bearing replacement method according to an embodiment of the present invention" above, a hydraulic jack 34 is placed below a steel main girder 62 whose underside is supported on an existing bearing 50, and the hydraulic jack 34 is used to jack up the steel main girder 62 to sever the connection between the steel main girder 62 and the existing bearing 50. However, the hydraulic jack 34 may not directly contact the steel main girder 62 whose underside is supported on the existing bearing 50, but may contact a bracket separately attached to the steel main girder 62, or another steel main girder 62 or a bracket attached thereto, and jack it up, thereby severing the connection between the steel main girder 62 whose underside is supported on the existing bearing 50 and the existing bearing 50.

[0057] The bearing replacement method according to the present invention is also applicable not only to cases where the existing bearing 50 is welded to the top surface of the steel pier 60 via the existing welded part 52 and installed on the top of the steel pier 60 without using any other joint than welding, but also to cases where a welded joint and a joint other than welding (for example, a bolted joint) are used in combination and the existing bearing 50 is installed on the top of the steel pier 60. In this case, the existing welded part 52 related to the welded joint is cold cut to release the welded joint between the existing bearing 50 and the steel pier 60, and the joint other than welding (for example, a bolted joint) that is used in combination is released, and then a jacking-up process is performed to jack up the steel main girder 62.

[0058] In addition, in the explanation of "(1) Bearing replacement method according to an embodiment of the present invention", the portable grinder 10 using the carbide burr 12 and the portable milling machine 20 using the end mill 22 are used as tools used in step S2 (process of releasing the welded joint of the existing bearing 50). When using these tools, the existing welded part 52 is removed by cold cutting to release the welded joint between the existing bearing 50 and the steel pier 60. However, if the steel pier 60 is not damaged, the welded joint between the existing bearing 50 and the steel pier 60 may be released by making a cut in the existing welded part 52 instead of removing the existing welded part 52. When making a cut in the existing welded part 52, for example, cutting with a chip saw, metal saw cutting, water jet cutting, or the like may be used appropriately depending on the situation. When making a cut in the existing welded part 52 to release the welded joint between the existing bearing 50 and the steel pier 60, it is preferable to remove the remaining existing welded part 52 before installing the new bearing.

[0059] Furthermore, if there is no problem in proceeding with step S2 (welding release process of existing bearing 50) of removing existing welded portion 52 by cold cutting simultaneously with step S3 (on-site preparation process for jacking up) (for example, when there is sufficient space above the top end of steel pier 60), part or all of step S2 may be proceeded in parallel with step S3, and step S2 may be completed by the time step S3 is completed. In other words, step S1 (factory fabrication process of steel bracket 30) and step S3 (on-site preparation process for jacking up) may be broadly regarded as the jacking up preparation process, and step S2 (welding release process of existing bearing 50) of removing existing welded portion 52 by cold cutting may be proceeded in parallel with the jacking up preparation process (steps S1 and S3). Even in this case, as with the bearing replacement method according to the embodiment described above in "(1) Bearing replacement method according to the embodiment of the present invention," the approximately 0.5 month period required for step S2 does not affect the length of the overall construction period for the bearing replacement, and the effect of shortening the overall construction period by about 0.5 months compared to the conventional method using goussing is obtained.

[0060] In the explanation of "(1) Bearing replacement method according to an embodiment of the present invention", it was described that step S2 (process of releasing the welded joint of the existing bearing 50) is completed before or at the same time as step S1 (process of fabricating the steel bracket 30 at a factory). However, from the viewpoint of improving safety, it is preferable that the period from releasing the welded joint between the existing bearing 50 and the top face of the steel pier 60 to replacing the existing bearing 50 with a new bearing is short. Therefore, as shown in Fig. 2, it is preferable to complete step S2 at the same time as step S1 (process of fabricating the steel bracket 30 at a factory). If there is no problem even if step S2 (process of releasing the welded joint of the existing bearing 50) for removing the existing welded portion 52 by cold cutting is carried out at the same time as step S3 (process of preparing the site for jacking up), it is preferable to complete step S2 at the same time as step S3 (process of preparing the site for jacking up).

[0061] In addition, it has been described that the effect of the bearing replacement method according to the embodiment of the present invention is to shorten the overall construction period of the bearing replacement work by approximately 0.5 months. However, the approximately 0.5 months specifically described as the effect of shortening the overall construction period is only one example, and the actual length of time that the overall construction period is shortened will vary depending on the size of the bridge to which the method is applied and other conditions, etc. [Explanation of symbols]

[0062] 10. Portable grinder 12…Carbide bar 20…Portable milling machine 22...End mill 30…Steel bracket 32…Sandre wood 34...Hydraulic jack 50…Existing bearing 50A…Lower shoe 50B…Kamikutsu 52...Existing welded section 54…Set bolt 56…Sole plate 58...Existing welded section 60…Steel pier 62…Steel main girder 62A…Reinforcing member

Claims

1. A bearing replacement method for a bridge having a lower steel member which is a steel member constituting at least a part of a substructure, an upper steel member which is a steel member constituting at least a part of a superstructure, and a bearing disposed between the lower steel member and the upper steel member and transmitting force between the lower steel member and the upper steel member, comprising the steps of: The existing bearing is connected onto the lower steel member by welding, a welded joint release process for releasing the connection between the existing support and the lower steel member by performing cold cutting on the welded joint portion between the existing support and the lower steel member; a jacking-up process of jacking up the upper steel member so as to cut an edge between the upper steel member and the existing support; having A bearing replacement method, characterized in that the welded connection release step is performed before the jacking up step.

2. 2. The method for replacing a bearing according to claim 1, wherein the cold cutting performed in the welded joint removing step is performed so as to remove at least a part of the welded joint portion.

3. 3. The method of claim 2, wherein the cold cutting is performed with a carbide burr.

4. 4. The method for replacing a bearing according to claim 3, wherein the shape of the carbide burr is such that an outer diameter of the carbide burr in a region near the tip of the carbide burr becomes smaller toward the tip.

5. 3. The method of claim 2, wherein the cold cutting is performed using an end mill.

6. 2. The method for replacing a bearing according to claim 1, wherein the cold cutting performed in the welded joint releasing step is performed so as to make a cut in at least a part of the welded joint.

7. A jack-up preparation step is provided before the jack-up step to prepare for jacking up the upper steel member, 2. The method for replacing a support according to claim 1, wherein the welded connection releasing step is carried out in parallel with the jack-up preparation step.

8. 8. The method for replacing a support according to claim 7, wherein the jack-up preparation step includes a steel bracket manufacturing step of manufacturing a steel bracket to be used when jacking up the upper steel member.

9. The bearing replacement method according to claim 7, wherein the jack-up preparation step includes a jack-up site preparation step of making preparations at the site for jacking up the upper steel member.

10. A bearing replacement method according to any one of claims 1 to 9, characterized in that the lower steel member is a steel pier or a steel bracket attached to the side of a pier.

11. The bearing replacement method according to any one of claims 1 to 9, characterized in that the upper steel component is a steel bridge girder or a steel cross girder.

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