Bearing replacement method

Abstract

To provide a bearing replacement method which can contribute to shorten a construction period of bearing replacement construction.SOLUTION: A bearing replacement method for replacing an existing bearing 50 with a new bearing, in a bridge having a lower steel member 60 which is a steel member constituting at least a part of a lower structure, an upper steel member 62 which is a steel member constituting at least a part of an upper structure, and the bearing 50 which is placed 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 includes a weld-bond releasing step of releasing connection between the existing bearing 50 connected onto the lower steel member 60 by welding and the lower steel member 60, by cold machining a welded-bonded part between the existing bearing 50 and the lower steel member 60.SELECTED DRAWING: Figure 2

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 maintenance work has become increasingly common in various parts of the country, and one of the most common types of bridge maintenance work is bearing replacement work.

[0003] In many cases, the existing bearings installed on the tops of steel piers have their lower shoes attached to the top surface of the steel pier by fillet welding, and when replacing the existing bearings installed on the tops of steel piers with new bearings, it is necessary to release the connection between the existing bearings and the steel pier. As a method for removing existing welds between steel members in bridges, gouging is commonly used, as described in Non-Patent Document 1.

[0004] However, in the gouging method 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 into 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 As shown in Figure 7), the strain-stress curve of steel differs significantly between room temperature (shown by the solid line in Figure 7) and high temperature (shown by the two-dot chain line in Figure 7), with the yield point dropping significantly at high temperatures. For this reason, if gouging is used to remove the existing weld between the existing bearing and the top surface of the steel pier when the existing bearing is connected to the steel main girder (the load due to the weight of the steel main girder is being applied to the top surface of the steel pier via the existing bearing), the heat from the gouging will cause the steel pier to become very hot, significantly lowering the yield point of the steel 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 method is to jack up the steel main girder to cut the connection between the steel main girder and the bearing, so that the load due to the weight of the steel main girder is not applied to the steel pier, and then gouge to remove the existing weld between the existing bearing and the top surface of the steel pier. The steel main girder and the existing bearing are generally connected using bolts with set bolts, and the connection between the steel main girder and the existing bearing can be released by removing the set bolts, and the connection between the steel main girder and the bearing can be cut by removing the set bolts and jacking up the steel main girder. Once the connection between the steel main girder and the bearing is cut, even if the yield point of the steel pier is lowered by the heat from gouging, the load due to the weight of the steel main 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 main girder is jacked up to cut the connection between the steel main girder and the support, and then the existing weld 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 aiming to become maintenance engineers," Japan Bridge Construction Association Bridge Technology Presentation Materials, Japan Bridge Construction Association Maintenance Committee Maintenance Technology Subcommittee, FY2012 Technology Presentation, [survey conducted 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 main girder to cut the edge between the steel main girder and the bearing, 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 bearing 50 (see Fig. 3) (step S104), the steel bracket 30 (see Fig. 6) is manufactured in a 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. Preparations were made on site to jack up the steel main girder 62 (see Figure 3) (step S102, see Figure 9), and the steel main girder 62 was jacked up (step S103). Only after completing the work of severing the connection between the steel main girder 62 and the existing bearing 50 could the process of removing the welded joint of the existing bearing 50 (step S104), in which the existing welded section 52 was removed by gouging, begin. 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 is a bearing replacement method as follows.

[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 that constitutes at least a part of the substructure, an upper steel member, which is a steel member that constitutes at least a part of the superstructure, and a bearing that 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 is characterized in that it includes a welded joint release step of cold cutting the welded joint 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 constituting 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 upper structure" includes not only steel members constituting at least a part of the upper structure, but also steel members fixed to the upper structure.

[0015] In this application, cold cutting refers to cutting a metal to be cut without melting it by heating, and also includes making a cut in the 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 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 that 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 that the jack directly contacts the upper steel member that is in contact with the existing support and jacks up the upper steel member, thereby severing the connection between the upper steel member and the existing support, but also that the jack does not directly contact the upper steel member that is in contact with the existing support, 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, thereby severing 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 of 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 of 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 bur is such that its outer diameter becomes smaller in the region near the tip of the carbide bur as it approaches the tip.

[0021] A sixth aspect of the bearing replacement method according to the present invention is the bearing replacement method of 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 of 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 portion.

[0023] An eighth aspect of the bearing replacement method of the present invention is a bearing replacement method of the second aspect, characterized in that it includes a jack-up preparation step before 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 characterized in that, in the eighth aspect of the bearing replacement method, the jacking-up preparation process includes a steel bracket manufacturing process for manufacturing steel brackets 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 in which preparations are made on site for jacking up the upper steel member.

[0026] An eleventh aspect of the bearing replacement method according to 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. [Effects 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 explanation 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. [Figure 2] Process chart of a bearing replacement method according to an embodiment of the present invention [Figure 3] FIG. 1 is a perspective view showing a typical process of the bearing replacement method according to an embodiment of the present invention, in which a welded joint removal process of the existing bearing 50 by cold cutting is being performed. [Figure 4] 1 is a front view schematically illustrating a state in which cold cutting is performed on an existing welded portion 52 using a carbide bar 12 in a welded joint release step of a support replacement method according to an embodiment of the present invention. [Figure 5] 1 is a front view schematically illustrating a state in which cold cutting is performed on an existing welded portion 52 by an end mill 22 in a welded joint release step of a bearing replacement method according to an embodiment of the present invention. [Figure 6] FIG. 10 is a perspective view schematically showing a state in which preparations for jacking up the steel main girder 62 have been completed in the bearing replacement method according to the embodiment of the present invention. [Figure 7] Schematic 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 the procedure for a conventional bearing replacement method using gouging. [Figure 9] An example of a process chart for a conventional bearing replacement method using gouging DETAILED DESCRIPTION OF THE INVENTION

[0030] A bearing replacement method according to an embodiment of the present invention will be described in detail below with reference to the drawings. In describing the bearing replacement method according to this embodiment, a case will be described in which 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. 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 weld 52 (see FIG. 3), which is a welded joint made by fillet welding. Note that the following description of the bearing replacement method according to an embodiment of the present invention assumes that the existing bearing 50 is welded to the top surface of the steel pier 60 via the existing weld 52 and installed on the top of the steel pier 60, without any other joining besides welding.

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

[0032] The bearing replacement method according to the embodiment of the present invention includes eight main steps, steps S1 to S8, as shown in the flowchart of FIG. 1 and the process chart of FIG.

[0033] (Step S1) In the bearing replacement method according to the embodiment of the present invention, first, in step S1, the production of the steel bracket 30 begins in a factory. The steel bracket 30 is a component used when jacking up the steel main girder 62 and is a component that is required early in the implementation of this embodiment, and the period required to produce the steel bracket 30 is approximately three months as shown in step S1 of the process chart in Figure 2, which is longer than the periods required for the other processes. Therefore, in the bearing replacement method according to this embodiment, the steel bracket 30 is produced in a factory in step S1, which is the first process 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 situation when this step S2 is being performed is shown schematically in Figure 3. The time required for this step S2 is about 0.5 months, as shown in the process chart in Figure 2.

[0035] As mentioned 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, the existing weld 52 is cold cut using a carbide burr 12 attached to the tip of the rotating main shaft of the portable grinder 10, thereby removing the existing weld 52 and releasing the welded connection between the existing bearing 50 and the steel pier 60.

[0036] The shape of the carbide bur 12 is preferably such that it is easy to cut the existing weld 52. Specifically, for example, as shown in FIG. 4, the shape of the carbide bur 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 bur 12 as it approaches the tip.

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

[0038] This step S2 starts after the start or before the end of step S1 (the factory manufacturing process of the steel bracket 30), and is carried out in parallel with step S1 (the factory manufacturing process of the steel bracket 30), so that this step S2 is completed before or at the same time as the end of step S1 (the factory manufacturing process of the steel bracket 30). In this way, once the factory manufacturing of the steel bracket 30 is completed in step S1, it is possible to immediately move on to the next step S3 of installing the steel bracket 30 on the steel pier 60, and the approximately 0.5 month period 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 required for step S2 compared to the conventional gouging method (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 gouging method 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 joint 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 manufactured in step S1 is attached to the side of the steel pier 60 so that it is positioned below the steel main girder 62, and a sander material 32 for height adjustment is placed on the top 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 in which preparations for jacking up the steel main girder 62 are complete (the state in which this step S3 is completed) is shown in Figure 6. The period required for this step S3 is about one month, as shown in the schedule in Figure 2.

[0044] Note that 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 preparations for jacking up the steel main girder 62 in step S3, in step S4, the cylinder of the hydraulic jack 34 placed in step S3 is extended upward to jack up the steel main girder 62, thereby breaking the connection between the existing bearing 50 and the sole plate 56 attached to the underside of the steel main girder 62. As described in step S3-c above, the set bolt 54 is removed to release the connection between the existing bearing 50 and the steel main girder 62. Therefore, when the steel main girder 62 is jacked up, the connection is broken between the upper shoe 50B (see Figures 4 and 5) of the existing bearing 50 and the sole plate 56 attached to the underside of the steel main girder 62 (the sole plate 56 is attached to the underside of the steel main girder 62 via the existing weld 58). As shown in the schedule in Figure 2, the time required for step S4 is approximately 0.5 months.

[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, so that the existing bearing 50 can now be removed.

[0048] Therefore, in this step S5, the existing bearings 50 are removed. A commonly used known method can be used to remove the existing bearings 50 in this step S5. The time required for this step S5 is about 0.5 months, as shown in the schedule in Figure 2.

[0049] (Step S6) After the existing bearing 50 is removed in step S5, a new bearing (not shown) is placed in a predetermined position on the top of the steel pier 60 in step S6. A commonly used known method can be used to place the new bearing (not shown) in a predetermined position on the top of the steel pier 60 in step S6. 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) in a predetermined position on the top end of the steel pier 60 in step S6, in step S7 the new bearing (not shown) is welded to the top end of the steel pier 60 by on-site welding, thereby fixing the new bearing (not shown) to the top end of the steel pier 60. When welding 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 on the top of the steel pier 60, so steps S5, S6 and S7 together can be considered as a bearing replacement process in which the existing bearing 50 is replaced with a new bearing.

[0052] (Step S8) In step S7, a new bearing (not shown) is welded and fixed to the top of the steel pier 60 by on-site welding, and then the steel main girder 62 is jacked down. Then, the bottom flange of the jacked-down steel main girder 62 is connected to the upper shoe of the new bearing (not shown) with set bolts 54. When carrying out the above steps in step S8, a commonly used known method can be used. The time 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 releasing the welded joint of the existing bearing 50) of the bearing replacement method of this embodiment, the existing weld 52 is removed by cold cutting to release the welded joint between the existing bearing 50 and the top face of the steel pier 60. Therefore, step S2 (process of releasing the welded joint of the existing bearing 50) of the bearing replacement method of this embodiment can be carried out 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. This can be carried out in parallel with step S1, which is the process of factory-fabricating the steel bracket 30, a component required for jacking up. In the bearing replacement method of this embodiment, step S2 (process of releasing the welded joint of the existing bearing 50) is completed before or at the same time as the completion of step S1 (factory-fabrication process of the steel bracket 30).

[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 Figure 2) compared to the overall construction period required when using the conventional method of gouging (about 7 months) (see Figure 9).

[0055] (3) Supplementary information In the above description of "(1) Bearing Replacement Method According to an Embodiment of the Present Invention," we focused on the case where an existing bearing 50 located under a steel main girder 62 is welded to the top surface of a steel pier 60 via an existing weld 52. However, the application of the bearing replacement method according to the present invention is not limited to this case and can be broadly applied to the following case: an existing bearing is located between a lower steel member that is at least a part of the substructure or is fixed to the substructure, and an upper steel member that is 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, and is welded to the lower steel member and installed on the lower steel member. An example of a lower steel member that is fixed to the substructure is a steel bracket attached to the side of a pier. In addition, the steel cross girders that connect adjacent steel main girders 62 can be considered to be components that constitute at least a part of the superstructure or components that are fixed to the superstructure, and are included in the upper steel components.

[0056] Furthermore, 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, thereby severing 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 and jack up a bracket separately attached to the steel main girder 62, or another steel main girder 62 or a bracket attached thereto, 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] Furthermore, the bearing replacement method according to the present invention is applicable not only to cases where the existing bearing 50 is welded to the top surface of the steel pier 60 via the existing weld 52 and installed on the top of the steel pier 60 without any other joint other 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 weld 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 the jacking-up process is carried out to jack up the steel main girder 62.

[0058] In the description of "(1) Bearing Replacement Method According to an Embodiment of the Present Invention," the tools used in step S2 (the process of releasing the welded connection of the existing bearing 50) are a portable grinder 10 using a carbide burr 12 and a portable milling machine 20 using an end mill 22. When using these tools, the existing weld 52 is removed by cold cutting to release the welded connection between the existing bearing 50 and the steel pier 60. However, if the steel pier 60 is not damaged, the welded connection between the existing bearing 50 and the steel pier 60 may be released by cutting a slit in the existing weld 52 rather than removing it. Cutting the slit in the existing weld 52 can be done with, for example, a chip saw, a metal saw, or a water jet, depending on the situation. When cutting the existing weld 52 to release the welded connection between the existing bearing 50 and the steel pier 60, it is preferable to remove the remaining existing weld 52 before installing the new bearing.

[0059] Furthermore, if step S2 (the step of releasing the welded joints of the existing bearings 50) of removing the existing welded portions 52 by cold cutting can be carried out simultaneously with step S3 (the step of preparing the site for jacking up) without causing any problems (for example, if there is sufficient space above the top of the steel pier 60), part or all of step S2 may be carried out in parallel with step S3 so that step S2 is completed by the time step S3 is completed. In other words, step S1 (the step of manufacturing the steel brackets 30 at a factory) and step S3 (the step of preparing the site for jacking up) may be broadly regarded as the jacking up preparation step, and step S2 (the step of releasing the welded joints of the existing bearings 50) of removing the existing welded portions 52 by cold cutting may be carried out in parallel with the jacking up preparation step (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 overall length of the bearing replacement work, and the effect of shortening the overall work period by approximately 0.5 months compared to the conventional method using gouging is obtained.

[0060] In the explanation of "(1) Bearing Replacement Method According to an Embodiment of the Present Invention," it was stated that step S2 (the step of releasing the welded connection of the existing bearing 50) should be completed before or simultaneously with the completion of step S1 (the step of fabricating the steel bracket 30 at a factory). However, from the viewpoint of improving safety, it is considered preferable to shorten the period from releasing the welded connection between the existing bearing 50 and the top face of the steel pier 60 to replacing the existing bearing 50 with a new bearing. Therefore, as shown in FIG. 2, it is preferable to complete step S2 simultaneously with the completion of step S1 (the step of fabricating the steel bracket 30 at a factory). If there are no problems with proceeding with step S2 (the step of releasing the welded connection of the existing bearing 50) by cold cutting simultaneously with step S3 (the step of preparing the site for jacking up), it is preferable to complete step S2 simultaneously with the completion of step S3 (the step of preparing the site for jacking up).

[0061] Furthermore, 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, but the period of approximately 0.5 months specifically described as the effect of shortening the overall construction period is just one example, and the length of the specific period of shortening the overall construction period will vary depending on the size of the bridge to which it is applied and other conditions, etc. [Explanation of symbols]

[0062] 10. Portable grinder 12...Carbide burr 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 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, the method comprising: The existing bearing is connected to the lower steel member by welding, A bearing replacement method characterized by including a welded joint removal process in which cold cutting is performed on the welded joint between the existing bearing and the lower steel member to release the connection between the existing bearing and the lower steel member.

2. a jacking-up step of jacking up the upper steel member so as to cut off an edge between the upper steel member and the existing support, 2. The bearing replacement method according to claim 1, wherein the welded connection releasing step is performed before the jacking up step.

3. 2. The bearing replacement method 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.

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

5. 5. The bearing replacement method according to claim 4, wherein the shape of the carbide bur is such that the outer diameter of the carbide bur in the region near the tip thereof becomes smaller as it approaches the tip.

6. 4. The method for replacing a bearing according to claim 3, wherein the cold cutting is performed using an end mill.

7. 2. The bearing replacement method 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 portion.

8. A jack-up preparation step is included, which prepares for jacking up the upper steel member before the jack-up step, 3. The bearing replacement method according to claim 2, wherein the welding connection releasing step is carried out in parallel with the jack-up preparation step.

9. 9. The bearing replacement method according to claim 8, wherein the jacking-up preparation step includes a steel bracket manufacturing step of manufacturing a steel bracket to be used when jacking up the upper steel member.

10. 9. The bearing replacement method according to claim 8, wherein the jack-up preparation step includes a jack-up site preparation step of making preparations on site for jacking up the upper steel member.

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

12. A bearing replacement method according to any one of claims 1 to 10, characterized in that the upper steel member is a steel bridge girder or a steel cross girder.

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