Fastening mechanism

Abstract

To recover a fastening function easily, even if a fastening mechanism has first bolts buried and fixed in a concrete part or a foundation.SOLUTION: A fastening mechanism 11 includes: first bolts 110 each of which is buried at one end side 112 in a foundation part 50 and protrudes at the other end side 114 from the foundation part 50; a connection member 130 detachably connected to the other end 116 of each first bolt 110; and second bolts 120 each of which is detachably connected at one end 122 to the connection member 130 and fastens a post leg part 22 to the foundation part 50. The second bolt 120 has a yield load smaller than that of the first bolt 110.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fastening system. [Background technology]

[0002] Patent Document 1 discloses a technology related to a fuse bolt whose fastening portion breaks when an external force exceeding a predetermined load is applied. In this prior art, the fuse bolt is formed with a constricted portion that breaks under a predetermined load.

[0003] Patent Document 2 discloses a technique for a nut that weakens the strength of its connection with a bolt so that it will come off the bolt when a predetermined or greater external force is applied. In this prior art, a weakening means is provided in a part of the nut body so that the nut body can easily deform and release the screwing engagement with the bolt. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-98119 A [Patent Document 2] Japanese Patent Application Publication No. 10-281133 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, in a fastening mechanism in which the base of a steel column is fastened to the foundation with a bolt whose one end is embedded and fixed in concrete, if the bolt yields or breaks, the fastening function cannot be restored unless large-scale construction work, such as chipping away at the concrete, is carried out to replace the bolt.

[0006] In view of the above, an object of the present invention is to provide a fastening mechanism capable of easily restoring fastening function even if it has a bolt buried and fixed in a concrete part or the ground. [Means for solving the problem]

[0007] The first aspect is a fastening mechanism comprising: a first bolt having one end buried and fixed in a concrete part or the ground and the other end protruding from the concrete part or the ground; a connecting member removably connected to the other end of the first bolt; and a second bolt having one end removably connected to the connecting member and fastening a fastened member to the concrete part or the ground, wherein one of the connecting member and the second bolt is set to have a smaller yield load than that of the first bolt.

[0008] In the fastening mechanism of the first aspect, the yield load of the connecting member or the second bolt is smaller than the yield load of the first bolt. Therefore, when an excessive tensile force acts on the anchor bolt due to a major earthquake or the like, the connecting member or the second bolt, which has a smaller yield load, yields or breaks before the first bolt. Therefore, the fastening function can be restored by replacing the yielded or broken connecting member or second bolt that is not buried, while leaving the first bolt with one end embedded and fixed in the concrete part or ground as it is.

[0009] A second aspect is the fastening mechanism described in the first aspect, in which the fastened member is the base of a steel column having a lower base plate and an upper base plate above the lower base plate, and the other end of the first bolt and one end of the second bolt are detachably connected to the connecting member between the lower base plate and the upper base plate.

[0010] In the second aspect of the fastening mechanism, the other end of the first bolt and one end of the second bolt are detachably connected by a connecting member between the lower base plate and the upper base plate of the column base portion, facilitating the replacement of a yielded or broken connecting member or second bolt.

[0011] A third aspect is the fastening mechanism according to the first or second aspect, wherein the second bolt has a smaller diameter than the first bolt in whole or in part.

[0012] In the fastening mechanism of the third aspect, the second bolt can be designed to have a smaller yield load than the first bolt by making the diameter of the second bolt smaller than that of the first bolt in whole or in part. Effect of the Invention

[0013] According to the present invention, even if there is a first bolt that is buried and fixed in a concrete portion or in the ground, it is possible to easily recover the fastening function. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a vertical cross-sectional view of the fastening mechanism of the first embodiment. [Diagram 2] FIG. 2 is a horizontal cross-sectional view of a column base of a steel column of the fastening mechanism of the first embodiment. [Diagram 3] FIG. 2 is a perspective view of a connecting member of the fastening mechanism of the first embodiment. [Figure 4] FIG. 2 is a vertical sectional view showing a state in which a second bolt of the anchor bolt in FIG. 1 is broken. [Diagram 5] FIG. 11 is a vertical cross-sectional view of a fastening mechanism according to a second embodiment. [Figure 6] FIG. 11 is a longitudinal sectional view of a connecting member of the fastening mechanism of the second embodiment. [Figure 7] FIG. 11 is a vertical cross-sectional view of a fastening mechanism according to a third embodiment. [Figure 8] FIG. 13 is a perspective view of a spacer of the fastening mechanism of the third embodiment. [Figure 9] FIG. 13 is a longitudinal sectional view of a connecting member of the fastening mechanism of the third embodiment. [Figure 10] FIG. 13 is a vertical cross-sectional view of a fastening mechanism according to a fourth embodiment. [Figure 11] FIG. 13 is a vertical cross-sectional view of a fastening mechanism according to a fifth embodiment. [Figure 12] FIG. 12 is an enlarged longitudinal sectional view of a main part of FIG. [Figure 13] FIG. 11 is a vertical cross-sectional view of a connecting member according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] First Embodiment A fastening mechanism according to a first embodiment of the present invention will be described. Two directions perpendicular to the horizontal direction are defined as the X direction and the Y direction, and are indicated by the arrows X and Y, respectively. The vertical direction perpendicular to the X direction and the Y direction is defined as the Z direction, and is indicated by the arrow Z. The view from the Y direction is defined as a front view.

[0016] [Overall structure] The overall structure of the fastening mechanism of this embodiment will be described.

[0017] As shown in FIG. 1, the fastening mechanism 11 of this embodiment is a mechanism for fastening a column base 22 of a steel column 20 made of H-shaped steel to a foundation 50 made of reinforced concrete using an anchor bolt 101 of this embodiment.

[0018] The column base 22 of the steel column 20 is composed of a rectangular lower base plate 30, an upper base plate 40, and vertical plate portions 23, 25 (see also FIG. 2). The lower base plate 30 of the column base 22 is installed on the upper surface 52 of the foundation portion 50 via a filler material 54 such as non-shrink mortar. Four lower insertion holes 32 are formed in the lower base plate (see also FIG. 2). Four upper insertion holes 42 are also formed in the upper base plate 40 at the same positions as the lower insertion holes 32 in a plan view.

[0019] The vertical plate portions 23, 25 are provided between the lower base plate 30 and the upper base plate 40, and are joined to the lower end portion of the steel column 20, the lower base plate 30, and the upper base plate 40. As shown in Fig. 2, in this embodiment, the vertical plate portion 23 is provided along the X direction of the steel column 20, and the vertical plate portion 25 is provided along the Y direction. Note that the anchor bolts 101 are not shown in Fig. 2.

[0020] As shown in Fig. 1, the anchor bolt 101 is configured to include a first bolt 110, a connecting member 130, and a second bolt 120. In this embodiment, the first bolt 110 and the second bolt 120 are steel bars having threads cut on the circumferential surface. In this embodiment, the second bolt 120 has a smaller overall diameter than the first bolt 110. In addition, the first bolt 110 and the second bolt 120 are made of the same material. Therefore, the second bolt 120 has a smaller yield load due to a tensile force than the first bolt 110.

[0021] As shown in Fig. 3, the connecting member 130 is a member made of a short square steel pipe that opens in the horizontal direction, in the Y direction in this embodiment. Specifically, it is made up of an upper surface portion 132 and a lower surface portion 134 that are plate-shaped and arranged in parallel with a gap between them vertically, and a side wall portion 136 that connects both ends of the upper surface portion 132 and the lower surface portion 134. An upper through hole 133 is formed in the center of the upper surface portion 132 in a plan view. Similarly, a lower through hole 135 is formed in the center of the lower surface portion 134 in a plan view.

[0022] As shown in Fig. 1, one end 112 of a first bolt 110 is embedded in a corresponding position of the four lower insertion holes 32 (see also Fig. 2) of the lower base plate 30 of the column base portion 22 in the foundation portion 50, and the other end 114 protrudes from the upper surface 52. The other end 114 of the first bolt 110 protruding from the upper surface 52 of the foundation portion 50 is inserted into the lower insertion hole 32 of the lower base plate 30 of the column base portion 22. The other end 116 of the first bolt 110 is inserted into a lower through hole 135 of a lower surface portion 134 of the connecting member 130 and fastened with a nut 70.

[0023] The second bolt 120 is inserted into the upper insertion hole 42 of the upper base plate 40 of the column base portion 22, and one end 122 is inserted into the upper through hole 133 of the upper surface portion 132 of the connecting member 130 and fastened with a nut 72. The other end 124 of the second bolt 120 protrudes above the upper base plate 40 of the column base portion 22, and two nuts 74, 75 are screwed into it. Then, by tightening the nuts 74, 75, the column base portion 22 is bolted to the foundation portion 50.

[0024] From another perspective, the other end 116 of the first bolt 110 and one end 122 of the second bolt 120 are each detachably connected to a connecting member 130 between the lower base plate 30 and the upper base plate 40 of the column base 22. Nuts 74, 75 are screwed onto the other end 124 of the second bolt 120 protruding above the upper base plate 40 of the column base 22, and are tightened, whereby the column base 22 is bolted to the foundation 50.

[0025] The yield load of the connecting member 130 is greater than the yield load of the second bolt 120. In this embodiment, the yield load of the connecting member 130 is greater than the yield load of the first bolt 110.

[0026] [Effect] Next, the operation of this embodiment will be described.

[0027] The yield load of the second bolt 120, which is not buried, is smaller than the yield load of the first bolt 110, one end side 112 of which is buried and fixed in the foundation part 50. Therefore, when an excessive tensile force acts on the anchor bolt 101 due to a major earthquake or the like, the second bolt 120, which has a smaller yield load, will yield or break before the first bolt 110, as shown in Figure 4 (Figure 4 shows the broken state).

[0028] After an earthquake, the nut 72 is removed to remove a part of the second bolt 120 remaining in the connecting member 130, a new second bolt 120 is inserted into the upper insertion hole 42 of the upper base plate 40 of the column base 22, and one end 122 is fastened to the upper surface part 132 of the connecting member 130 with the nut 72. Then, by tightening the nuts 74, 75, the column base 22 is again fastened to the foundation 50 with the bolt. In other words, the fastening function of the first bolt 110, one end side 112 of which is embedded and fixed in the foundation 50, is restored by replacing the yielded or broken second bolt 120.

[0029] Second Embodiment Next, a fastening mechanism according to a second embodiment of the present invention will be described. Note that the same members as those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted or simplified.

[0030] [Overall structure] The overall structure of the fastening mechanism of this embodiment will be described.

[0031] As shown in Fig. 5, the fastening mechanism 12 of this embodiment is a mechanism for fastening a column base 22 of a steel column 20 made of H-shaped steel to a foundation 50 made of reinforced concrete using an anchor bolt 102 of this embodiment. The anchor bolt 102 has a first bolt 110, a second bolt 120, and a connecting member 230. The fastening mechanism 12 of this embodiment is similar to that of the first embodiment except for the connecting member 230 constituting the anchor bolt 102, and therefore detailed description of the components other than the connecting member 230 will be omitted.

[0032] 5 is configured with a joint nut into which the other end 116 of the first bolt 110 and one end 122 of the second bolt 120 are screwed, as shown in Fig. 6. A first screw hole 232 on one end side of the connecting member 230 is sized to allow the first bolt 110 to be screwed in, and a second screw hole 234 on the other end side is sized to allow the second bolt 120 to be screwed in. Note that within the connecting member 230, a gap is formed between the other end 116 of the first bolt 110 and one end 122 of the second bolt 120.

[0033] 5, the other end 116 of the first bolt 110 (see FIG. 6) and one end 122 of the second bolt 120 (see FIG. 6) are each detachably connected to a connecting member 230 between the lower base plate 30 and the upper base plate 40 of the column base 22. Nuts 74, 75 are screwed onto the other end 124 of the second bolt 120 protruding above the upper base plate 40 of the column base 22, and are tightened, whereby the column base 22 is bolted to the foundation 50.

[0034] The yield load of the connecting member 230 is greater than the yield load of the second bolt 120. In this embodiment, the yield load of the connecting member 230 is greater than the yield load of the first bolt 110.

[0035] [Effect] Next, the operation of this embodiment will be described.

[0036] The yield load of the second bolt 120, which is not buried, is smaller than the yield load of the first bolt 110, one end side 112 of which is buried and fixed in the foundation part 50. Therefore, when an excessive tensile force acts on the anchor bolt 101 due to a major earthquake or the like, the second bolt 120, which has a smaller yield load, yields or breaks before the first bolt 110 (see FIG. 4).

[0037] After an earthquake, a part of the second bolt 120 remaining in the connecting member 230 is removed, and a new second bolt 120 is inserted into the upper insertion hole 42 of the upper base plate 40 of the column base 22, and one end 122 is screwed into the second screw hole 234 of the connecting member 230 to connect the new bolt. Then, the nuts 74, 75 are tightened to fasten the column base 22 to the foundation 50 again. In other words, the fastening function is restored by replacing the yielded or broken second bolt 120 while leaving the first bolt 110 with its one end 112 embedded and fixed in the foundation 50 as it is.

[0038] <Third embodiment> A fastening mechanism according to a third embodiment of the present invention will be described below. Note that the same members as those in the first and second embodiments are given the same reference numerals, and duplicated descriptions will be omitted or simplified.

[0039] [Overall structure] The overall structure of the fastening mechanism of this embodiment will be described.

[0040] As shown in FIG. 7, the fastening mechanism 13 of this embodiment is a mechanism that fastens the column base 26 of a steel column 24 made of a square steel pipe to a reinforced concrete foundation 50 using the anchor bolt 103 of this embodiment and a spacer 350.

[0041] The column base 26 of the steel column 24 has a square base plate 34. The base plate 34 of the column base 26 is installed on the upper surface 52 of the foundation 50 via a filler 54 such as non-shrink mortar. An insertion hole 36 is formed in each of the four corners of the base plate 34. A steel spacer 350 is placed on each of the four insertion holes 36 of the base plate 34. In this embodiment, the spacer 350 is simply placed on the base plate 34 and is not joined by welding or the like.

[0042] 8, spacer 350 of this embodiment has a cylindrical portion 352 and a lid portion 354, and a through hole 356 is formed in lid portion 354. Spacer 350 is sized to accommodate connecting member 330 (described later) therein (see FIG. 7).

[0043] 9, the anchor bolt 103 has a first bolt 110, a second bolt 320, and a connecting member 330 (see also FIG. 7). Note that the first bolt 110 of this embodiment is similar to that of the first embodiment, and therefore a detailed description thereof will be omitted.

[0044] It is configured to include a first bolt 110, a connecting member 330, and a second bolt 320 (see also FIG. 7). In this embodiment, the first bolt 110 and the second bolt 320 are steel rods having threads cut on their circumferential surfaces. In this embodiment, the first bolt 110 and the second bolt 320 have the same diameter at the threaded portions. However, the second bolt 320 has a necked portion 326 formed in the axial middle portion, making the diameter partially narrow.

[0045] The connecting member 330 is composed of a joint nut into which the other end 116 of the first bolt 110 and one end 322 of the second bolt 320 are screwed onto either side of a screw hole 332. Since the threaded portions of the first bolt 110 and the second bolt 320 have the same axial diameter, the screw hole 332 has the same hole diameter in the axial direction. In the connecting member 330, a gap is formed between the other end 116 of the first bolt 110 and one end 322 of the second bolt 320.

[0046] 7, the other end 114 of the first bolt 110 protruding from the upper surface 52 of the foundation portion 50 is inserted into the insertion hole 36 of the base plate 34 of the column base portion 26. The other end 116 of the first bolt 110 and one end 322 of the second bolt 320 are screwed into a screw hole 332 of a connecting member 330 within a spacer 350. In other words, the other end 116 of the first bolt 110 and one end 322 of the second bolt 320 are each detachably connected to the connecting member 330 within the spacer 350.

[0047] The other end 324 of the second bolt 320 is inserted into a through hole 356 (see also FIG. 8 ) of a lid portion 354 of a spacer 350, and a nut 75 is screwed in. Then, by tightening the nut 75, the column base portion 26 is fastened to the base portion 50 by the bolt.

[0048] As described above, second bolt 320 has necked portion 326 as an example of a weak portion formed in the axial middle portion, and has a partially narrowed diameter. Therefore, when first bolt 110 and second bolt 320 are pulled in both axial directions while first bolt 110 and second bolt 320 are connected by connecting member 330, necked portion 326 of second bolt 320 yields or breaks first. In other words, second bolt 320 has a smaller yield load in the tensile direction than first bolt 110.

[0049] [Effect] Next, the operation of this embodiment will be described.

[0050] The yield load of the second bolt 320, which is not buried, is smaller than the yield load of the first bolt 110, one end side 112 of which is buried and fixed in the foundation part 50. Therefore, when an excessive tensile force acts on the anchor bolt 103 due to a large earthquake or the like, the necked part 326 of the second bolt 320 yields or breaks before the first bolt 110.

[0051] After an earthquake, a part of the second bolt 320 remaining in the connecting member 330 is removed, and one end 122 of a new second bolt 320 is screwed into the threaded hole 332 of the connecting member 330 to connect it. Then, the nut 75 is tightened, so that the column base 26 is again bolted to the foundation 50. In other words, the fastening function is restored by replacing the yielded or broken second bolt 320 while leaving the first bolt 110 with one end 112 embedded and fixed in the foundation 50 in that state.

[0052] <Fourth embodiment> A fastening mechanism according to a fourth embodiment of the present invention will be described below. Note that the same members as those in the first to third embodiments are given the same reference numerals, and duplicated descriptions will be omitted or simplified.

[0053] [Overall structure] The overall structure of the fastening mechanism of this embodiment will be described.

[0054] As shown in Fig. 10, the fastening mechanism 14 of this embodiment is a mechanism for fastening the column base 26 of a steel column 24 made of a square steel pipe to a reinforced concrete foundation 50 using the anchor bolt 103 of this embodiment and the recess 450. The column base 26 of the steel column 24 and the anchor bolt 103 are similar to those in the third embodiment, so a detailed description will be omitted.

[0055] Recesses 450 are formed below the four insertion holes 36 of the base plate 34 in the foundation portion 50. Holes are also formed in the filler 54 at locations corresponding to the recesses 450. The recesses 450 in this embodiment have a circular cross section and are sized so that the connecting member 330 can be accommodated within the recesses 450.

[0056] One end 112 of the first bolt 110 is embedded in the foundation 50, and the other end 114 of the first bolt 110 protrudes from the bottom 452 of the recess 450. The second bolt 320 is inserted into the insertion hole 36 of the base plate 34 of the column base 26. The other end 116 of the first bolt 110 and one end 322 of the second bolt 320 are each detachably connected to a connecting member 330 within the recess 450.

[0057] The other end 324 of the second bolt 320 is inserted into the insertion hole 36 of the base plate 34, and a nut 75 is screwed into it. Then, by tightening the nut 75, the column base 26 is fastened to the base 50 by the bolt.

[0058] [Effect] Next, the operation of this embodiment will be described.

[0059] The yield load of the second bolt 320, which is not buried, is smaller than the yield load of the first bolt 110, one end side 112 of which is buried and fixed in the foundation part 50. Therefore, when an excessive tensile force acts on the anchor bolt 103 due to a large earthquake or the like, the necked part 326 of the second bolt 320 yields or breaks before the first bolt 110.

[0060] After an earthquake, a part of the second bolt 320 remaining in the connecting member 330 is removed, and one end 122 of a new second bolt 320 is screwed into the screw hole 332 of the connecting member 330 to connect it. The new second bolt 320 is inserted into the insertion hole 36 of the base plate 34 of the column base 26, and the nut 75 is tightened, thereby fastening the column base 26 to the foundation 50 again with the bolt. In other words, the fastening function is restored by replacing the yielded or broken second bolt 320 while leaving the first bolt 110 with one end 112 embedded and fixed in the foundation 50 in that state.

[0061] <Fifth embodiment> A fastening mechanism according to a fifth embodiment of the present invention will be described below. Note that the same members as those in the first to fourth embodiments are given the same reference numerals, and duplicated descriptions will be omitted or simplified.

[0062] [Overall structure] The overall structure of the fastening mechanism of this embodiment will be described.

[0063] 11, the fastening mechanism 15 of this embodiment is a mechanism for fastening the reinforced concrete foundation bottom plate 60 of a building 66 to the ground 500 made of bedrock using a plurality of anchor bolts 101 and spacers 550. In this embodiment, there is a soil layer (not shown) on the bedrock in the ground 500, but this is not limiting.

[0064] Although the thickness and length of the first bolt 110, the thickness and length of the second bolt 120, and the size and plate thickness of the connecting member 130 constituting the anchor bolt 101 are different from those of the first embodiment, the overall shape and function are the same as those of the first embodiment, so the same reference numerals are used and the description is omitted. Similarly, the shape and function of the nuts 70, 72, 74, and 75 are the same as those of the first embodiment, so the same reference numerals are used.

[0065] The foundation base plate 60 is formed with a plurality of through holes 64 through which the first bolts 110 of the anchor bolts 101 are inserted. Although there are two anchor bolts 101 and through holes 64 in Fig. 11, the number of such holes is provided according to the planar shape of the foundation base plate 60 and the size of the building 66. Although not shown in the figure, a sheath pipe is provided in the through hole 64.

[0066] As shown in Figs. 11 and 12, steel spacers 550 are provided above the through holes 64 of the foundation base plate 60. As shown in Fig. 12, the spacer 550 of this embodiment is a member made of channel steel. Specifically, it is made up of an upper flange 552, a lower flange 554, and a web 556 connecting the upper flange 552 and the lower flange 554. An upper insertion hole 553 is formed in the center of the upper flange 552. Similarly, a lower insertion hole 555 is formed in the center of the lower flange 554 in a plan view.

[0067] 11, one end side 112 of a first bolt 110 is buried in the ground 500 at positions corresponding to the multiple through holes 64 of the foundation base plate 60, and the other end side 114 protrudes from the ground surface 502. The other end side 114 of the first bolt 110 protruding from the ground surface 502 passes through the through hole 64 of the foundation base plate 60 and protrudes from the upper surface 62 of the foundation base plate 60. An anchor body that transmits a tensile force to the ground 500 may be constructed at one end of the one end side 112.

[0068] 12, the other end 114 of the first bolt 110 protruding from the upper surface 62 of the foundation base plate 60 is inserted into a lower insertion hole 555 of a lower flange 554 of a spacer 550. The other end 116 of the first bolt 110 is inserted into a lower through-hole 135 of a lower surface portion 134 of a connecting member 130 and fastened with a nut 70.

[0069] The second bolt 120 is inserted into the upper insertion hole 553 of the upper flange 552 of the spacer 550, and one end 122 is inserted into the upper through hole 133 of the upper surface portion 132 of the connecting member 130 and fastened with a nut 72. The other end 124 of the second bolt 120 protrudes above the upper surface portion 132 of the connecting member 130, and two nuts 74, 75 are screwed in. Then, by tightening the nuts 74, 75, the foundation base plate 60 is fastened to the ground 500 with the bolts.

[0070] From another perspective, the other end 116 of the first bolt 110 and one end 122 of the second bolt 120 are each detachably connected to the connecting member 130 between the lower flange 554 and the upper flange 552 of the spacer 550. Nuts 74, 75 are screwed onto the other end 124 of the second bolt 120 protruding above the upper flange 552 of the spacer 550, and are tightened, whereby the foundation base 60 is bolted to the ground 500.

[0071] [Effect] Next, the operation of this embodiment will be described.

[0072] The yield load of the second bolt 120, which is not buried, is smaller than the yield load of the first bolt 110, one end side 112 of which is buried and fixed in the ground 500. Therefore, when an excessive tensile force acts on the anchor bolt 101 due to a major earthquake or the like, the second bolt 120 will yield or break.

[0073] After an earthquake, nuts 72 are removed to remove a portion of second bolt 120 remaining in connecting member 130, a new second bolt 120 is inserted into upper insertion hole 553 of upper flange 552 of spacer 550, and one end 122 is fastened to upper surface portion 132 of connecting member 130 with nut 72. Then, nuts 74, 75 are screwed into the other end 124 and tightened, whereby foundation base plate 60 is again fastened to ground 500 with the bolt. In other words, the fastening function is restored by replacing the yielded or broken second bolt 120 while leaving one end side 112 of first bolt 110 buried and fixed in ground 500 as it is.

[0074] <Modification> Next, modified examples of the connecting member will be described. In the first to fifth embodiments, the yield load of the second bolts 120, 320 is made smaller than that of the first bolt 110, but in this modified example, the yield load of the connecting member is made smaller than that of the first bolt 110. The second bolt in the first to fifth embodiments may be the same as the first bolt 110, and the connecting member of this modified example may be applied.

[0075] 13 is configured with a coupling nut into which the other end 116 of the first bolt 110 and one end 622 of the second bolt 620 are screwed into either side of a screw hole 634. Note that the second bolt 620 is the same as the first bolt 110 except for its length.

[0076] A constricted portion 632 is formed in the axial middle portion of the connecting member 630, so that the outer diameter is partially narrowed. The other end of the constricted portion 632 in the axial direction is designated as L1, one end is designated as L2, and the center is designated as L3.

[0077] The other end 116 of the first bolt 110 and one end 622 of the second bolt 620 are screwed into the connecting member 630. In other words, the other end 116 of the first bolt 110 and one end 622 of the second bolt 620 are each detachably connected to the connecting member 630.

[0078] The other end surface 117 of the first bolt 110 and one end surface 623 of the second bolt 620 are positioned between the other end L1 and one end L2 of the constricted portion 632. Furthermore, the intermediate position between the other end surface 117 of the first bolt 110 and one end surface 623 of the second bolt 620 is preferably near the center L3. Within the connecting member 630, a gap is formed between the other end surface 117 of the first bolt 110 and one end surface 623 of the second bolt 620.

[0079] Since the connecting member 630 has a narrowed portion 632 formed therein, when the first bolt 110 and the second bolt 620 are fastened and pulled in both axial directions, the yield load is smaller than the yield loads of the first bolt 110 and the second bolt 620.

[0080] [Effect] Next, the operation of this embodiment will be described.

[0081] When an excessive tensile force acts on the anchor bolt 104 due to a major earthquake or the like, the connecting member 630 yields or breaks at the necked portion 632. After the earthquake, the broken connecting member 630 is removed and replaced with a new connecting member 630, and the fastening function is restored.

[0082] <Other> The present invention is not limited to the above embodiment.

[0083] For example, in the above embodiment and modified examples, the base of a steel column, which is an example of a fastened member, is fastened to a foundation, which is an example of a concrete portion, by bolts, but this is not limited to this.

[0084] For example, one end side 112 of first bolt 110 may be embedded in a concrete portion other than foundation portion 50, such as a slab of reinforced concrete construction, or may be embedded in a wall.

[0085] In the case of a slab, one end 112 of the first bolt 110 may be embedded in the ceiling slab and the other end may protrude downward. For example, the present invention may be applied to bolt fastening of the upper end of a stud that connects and reinforces a floor slab or foundation with a ceiling slab to the ceiling slab as a measure against flooding inside a building. Measures against flooding inside a building include measures to prevent damage to the ceiling slab when steam fills a room and pressure inside the building increases.

[0086] In the case of a wall, examples of the fastened portion include stairs or walkways fixed to the wall.

[0087] In addition, for example, in the above embodiment, the diameter of the second bolt is made smaller in part or in whole to make the yield load smaller than that of the first bolt, but this is not limited to this. For example, even if the diameters of the two are the same, the second bolt may be made of a material having a lower strength than the first bolt, so that the yield load of the second bolt is smaller than that of the first bolt.

[0088] In addition, for example, in the above-described modified example, the connecting member is provided with a constricted portion to make the yield load smaller than that of the first bolt, but this is not limited to this. The connecting member may be made of a low-strength material to make the yield load smaller than that of the first bolt without providing a constricted portion.

[0089] Also, for example, one end side 112 of the first bolt 110 in the above-described fifth embodiment is embedded and fixed in the ground 500, which is a bedrock, but this is not limited thereto. One end side 112 of the first bolt 110 may be embedded and fixed in a ground other than a bedrock.

[0090] Furthermore, the present invention can be embodied in various forms without departing from the spirit and scope of the present invention. A plurality of embodiments and modifications can be implemented in appropriate combination. [Explanation of symbols]

[0091] 11 Fastening mechanism 12 Fastening mechanism 13 Fastening mechanism 14 Fastening mechanism 15 Fastening mechanism 22 Column base (an example of a fastened member) 26 Column base (an example of a fastened member) 30 Lower Base Plate 40 Upper Base Plate 50 Foundation (Example of concrete) 60 Foundation base plate (an example of a fastened member) 101 Anchor bolt 102 Anchor bolt 103 Anchor bolt 104 Anchor bolt 110 First Bolt 112 One end side 114 Other end side 116 Other end 120 Second Bolt 122 One end 124 Other end 130 Connecting member 230 Connecting member 320 Second Bolt 322 One end 324 Other end 330 Connecting members 500 ground 620 Second Bolt 622 One end 630 Connecting members

Claims

1. A first bolt, one end of which is embedded and fixed in a concrete portion or the ground and the other end of which protrudes from the concrete portion or the ground; A connecting member detachably connected to the other end of the first bolt; A second bolt, one end of which is detachably connected to the connecting member and which fastens the fastened member to the concrete portion or the ground; having One of the connecting member and the second bolt is set to have a smaller yield load than the first bolt. Fastening mechanism.

2. The fastened member is a column base of a steel column having a lower base plate and an upper base plate above the lower base plate, The other end of the first bolt and the one end of the second bolt are detachably connected to the connecting member between the lower base plate and the upper base plate. The fastening system of claim 1 .

3. The second bolt has a smaller diameter than the first bolt in whole or in part. The fastening mechanism according to claim 1 or 2.

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