Method of mounting insert washer and insert washer

Abstract

To provide a method for mounting a nest washer applied to a base plate having an enlarged anchor bolt insertion hole, and the nest washer.SOLUTION: An indication point 22,34 is provided on the upper surface of a seat part at a position where the thickness of a cylindrical leg part 23,32 of an upper washer 20 and a lower washer 30 becomes minimum, and a graph showing the relation between an eccentric distance and a rotation angle is prepared for each size of a nest washer. An eccentric reference line BL obtained by extending a line connecting the center D of the expanded hole 4 and the axis C of the anchor bolt 3 in the eccentric direction is set, the rotation angles θ 1 and θ 2 of the washers are checked on a graph in accordance with the eccentric distance E of the anchor bolt 3 measured at the site, and the indication point 34 of the lower washer 30 is aligned with the eccentric reference line BL with the cylindrical leg portion 32 of the lower washer 30 fitted in the expanded hole 4. When the lower washer 30 is positioned by rotating by a rotation angle θ1 and the upper washer 20 is inserted into the anchor bolt and rotated by θ2 in the opposite direction on the upper surface of the lower washer, the cylindrical leg part 23 of the upper washer 20 is fitted into the leg part receiving hole of the lower washer.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a nested washer that is attached to an enlarged hole for inserting an anchor bolt in a base plate fixed to the lower end of a steel column in an exposed-type column base used in buildings such as steel-framed or steel-reinforced concrete structures, and is used to tighten the anchor bolt. [Background technology]

[0002] In exposed-type column bases, anchor bolts are embedded in the foundation concrete at predetermined positions, leaving only their upper ends, and a base plate fixed to the lower end of a steel column is anchored to the foundation concrete by multiple anchor bolts. Specifically, multiple anchor bolt insertion holes are formed in the base plate at predetermined positions, and the anchor bolts are inserted into these insertion holes and fixed by tightening nuts that screw onto them via washers. In this case, the base plate is placed on level mortar applied to the top surface of the foundation concrete, and a grout material such as non-shrink mortar is injected and filled into the space formed between the top surface of the foundation concrete and the underside of the base plate to ensure close contact between them.

[0003] Anchor bolts, acting as a stress transmission medium for the column base, bear tensile and shear forces. At the same time, they are also necessary for positioning during steel frame erection, so high precision is required during installation. In other words, horizontal positioning and perpendicularity are important for anchor bolts. The Building Standards Act stipulates that the anchor bolt insertion holes provided in the base plates of exposed-type column bases must be within 5 mm of the anchor bolt diameter. However, this regulation does not apply when safety is confirmed through structural calculations (including experiments). To address anchor bolt installation errors (misalignment), a technique has been proposed in which the anchor bolt insertion holes are enlarged to a larger inner diameter than the specified value, and a nested washer with a tubular leg whose outer diameter matches the enlarged hole is fitted to the enlarged hole (see Patent Documents 1 to 4).

[0004] These nested washers (hereafter referred to as nested washers), which consist of a pair of large and small washers, each have a flange-shaped portion that serves as a seat at the top of the cylindrical portion (leg portion) with an eccentric hole in the upper and lower washers, and the smaller-diameter top washer fits inside the larger-diameter bottom washer. When the nested washers are installed in the enlarged anchor bolt insertion hole of the base plate, they are designed so that the total clearance between each component is a maximum of 5 mm. Specifically, the total of the gaps between the eccentric hole (anchor bolt receiving hole) of the upper washer and the anchor bolt, the gap between the eccentric hole (leg receiving hole) of the lower washer into which the leg portion of the upper washer fits and the leg portion of the upper washer, and the gap between the anchor bolt insertion hole (enlarged hole) in the base plate and the leg portion of the lower washer must be within 5 mm. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 10-213123 (see Figures 2, 6, and 7) [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-57004 (see FIG. 8) [Patent Document 3] Japanese Patent Application Laid-Open No. 7-292772 (see FIG. 2) [Patent Document 4] Japanese Patent Application Laid-Open No. 6-74227 (see Figure 1)

[0006] The washers are nested, consisting of a pair of disk-shaped washers, one large and one small, stacked one on top of the other. The upper and lower washers have a common shape, with a cylindrical leg on the underside of the disk-shaped seat. The lower washer has a hole for fitting the cylindrical leg of the upper washer, and a hole for inserting the anchor bolt, both at a position eccentric to the center of the seat, penetrating the seat and the cylindrical leg. In this case, the cylindrical leg of the upper washer is fitted into the eccentric hole of the lower washer with a predetermined clearance, allowing relative rotation in the circumferential direction. During steel frame erection work, if the position of the anchor bolt protruding above the foundation concrete is deviated from the design value, the upper and lower washers can be rotated left and right to adjust their relative positions, allowing the washers to be installed into the anchor bolt insertion hole (enlarged hole) in the base plate with the anchor bolt passing through.

[0007] Furthermore, this type of nested washer has a structure in which the cylindrical legs of the upper and lower washers fit almost without any gaps into the anchor bolt insertion hole in the base plate, which is formed as an enlarged hole, so that when a shear force is applied to the base plate due to an earthquake, wind, etc., the shear force can be appropriately transmitted to the anchor bolt via the legs on the underside of the washer, which has the advantage. In other words, by using nested washers, it is possible to eliminate anchor bolt installation errors (deviations from the reference position) within the allowable range of eccentricity, and avoid performance-related measures such as "re-adjusting the base" or "re-drilling the anchor bolt insertion hole in the base plate," which are performed in some cases. Summary of the Invention [Problem to be solved by the invention]

[0008] The nested washers described in Patent Documents 1 to 4 are typically used in column bases, but are also used in earthquake-resistant reinforcement, post-installed anchors, bridges, and bridge fall prevention devices. In the case of column bases, the bottom washer is first rotated in an appropriate direction to find a position where its tubular leg can be fitted into the enlarged hole in the base plate fixed to the bottom end of the steel column. Next, the top washer is inserted into the anchor bolt and rotated in the same way to fit its tubular leg into the leg-receiving hole in the bottom washer. This installation process is performed downward within the visible range, so it is not particularly difficult to install the nested washer. However, since it is done by feel, it is not very efficient, and improvements in workability have been desired.

[0009] Furthermore, upward construction is more difficult than downward construction because it places significant restrictions on the construction location and construction posture. Specifically, because the nested washers must be installed against gravity, it is impossible to perform construction while keeping an eye on the installation position, as in downward construction, where the bottom washer is placed first and then the top washer is placed on top. This is particularly problematic when the construction space is narrow and the construction is done blindly.

[0010] The present invention was created to solve the problems of the conventional technology described above, and has as its object to provide a method for efficiently attaching a nested washer to a base plate in which an anchor bolt insertion hole is formed as an enlarged hole, and a nested washer to be used for this method. [Means for solving the problem]

[0011] As technical means for solving the above-mentioned problems, the invention according to claim 1 of the present application provides a method for installing a nested washer, which comprises a pair of upper and lower washers, each having a concentric cylindrical leg on the underside of the seat, wherein the upper washer has an anchor bolt receiving hole with an inner diameter that matches the outer diameter of the anchor bolt, which passes through the seat and the cylindrical leg at an eccentric position, and the lower washer has a leg receiving hole with an inner diameter that matches the outer diameter of the cylindrical leg of the upper washer, which passes through the seat and the cylindrical leg, whose outer diameter matches the enlarged hole in a base plate, at an eccentric position, and the nested washer is used in a state where the cylindrical leg of the upper washer is inserted into the leg receiving hole of the lower washer and the washers are stacked one on top of the other, and the anchor bolt is inserted into the enlarged hole in the base plate for inserting the anchor bolt, in a state where the anchor bolt is inserted into the upper washer, The lower washer is provided with an indicator point on the peripheral side of the upper surface of the seat portion at a position where the thickness of the cylindrical leg is at its smallest in the circumferential direction, and when the anchor bolt is eccentric with respect to the enlarged hole in the base plate, the eccentric distance is measured and an eccentricity reference line is set by extending a line connecting the center of the enlarged hole in the base plate and the axis of the anchor bolt in the eccentric direction to the upper surface of the base plate, and the indicator point of the bottom washer is aligned with this eccentricity reference line with the cylindrical leg fitted into the enlarged hole in the base plate, and then the bottom washer is rotated to a rotation angle position read from a graph showing the relationship between the eccentric distance and the rotation angle of the bottom washer, and then the top washer is inserted into the anchor bolt and rotated to a predetermined position so that the cylindrical leg of the top washer is fitted into the leg receiving hole of the bottom washer.

[0012] The present invention was made by focusing on the relationship between the eccentricity distance, which is the distance between the center of the enlarged hole in the base plate and the axial center of the anchor bolt, and the rotation angle of the washer. The key point is to prepare a graph showing this relationship in advance for each size of nested washer provided according to the anchor bolt diameter, and to check the rotation angle of each washer according to the eccentricity distance of the anchor bolt measured at the construction site, and to fit it in the appropriate position. In this case, it is necessary to mark an indicator point on the peripheral edge of the upper surface of the seat at the position where the thickness of the tubular leg of the lower washer is smallest (because the leg receiving hole that fits with the tubular leg of the upper washer is formed eccentrically, the opposite side of the center of the seat from the position where the thickness of the tubular leg is largest).

[0013] An eccentricity reference line is then established by extending a line connecting the center of the enlarged hole in the base plate and the axis of the anchor bolt in the eccentric direction to the top surface of the base plate, and the rotation angle corresponding to the eccentricity distance measured on site is confirmed against a pre-prepared graph. Next, with the cylindrical leg of the bottom washer fitted into the enlarged hole in the base plate, the indicator point on the bottom washer is first aligned with the eccentricity reference line, and the bottom washer is positioned by rotating it by the rotation angle corresponding to the eccentricity distance on the graph. The top washer is then inserted onto the anchor bolt and rotated on its top surface. When it reaches the predetermined rotation angle, the cylindrical leg of the top washer naturally fits into the leg-receiving hole of the bottom washer. The method of the present invention allows the nested washer to be easily and reliably fitted into the enlarged hole in the base plate to fill the excessively large gap in the enlarged hole with steel, greatly contributing to improved workability. The position at which the cylindrical leg of the upper washer fits into the leg receiving hole of the lower washer is the same as the rotation angle of the bottom washer on the opposite side of the eccentric reference line, regardless of the direction of rotation.

[0014] The invention according to claim 2 of the present application is characterized in that, in the configuration of claim 1 above, the upper washer has an index point on the periphery of the upper surface of the seat corresponding to the position where the wall thickness of the cylindrical leg is at its smallest in the circumferential direction, and is rotated in the opposite direction by the same rotation angle as the lower washer. In other words, if an index point similar to that on the bottom washer is also provided on the upper washer, a set of upper and lower washers can be prepared in advance in a state where they are stacked at positions rotated in opposite directions by an angle of rotation corresponding to the eccentricity distance. This is an effective means for upward installation where the installation position and installation posture are difficult and the installation is against gravity, or in places with limited installation space, or in installation conditions where installation is done blindly (groping around), etc.

[0015] The invention of claim 3 is a nested washer consisting of a pair of upper and lower washers used in the method of installing a nested washer according to claim 1 or claim 2, wherein at least the lower washer is provided with an index point on the peripheral edge of the upper surface of the seat portion corresponding to the position where the wall thickness of the cylindrical leg is at its smallest in the circumferential direction. When this nested washer is applied to an anchor bolt that is installed eccentrically with respect to the enlarged hole (anchor bolt insertion hole) in the base plate, it can be smoothly fitted into the enlarged hole (anchor bolt insertion hole) in the base plate, leading to improved installation work. [Effects of the Invention]

[0016] In the present invention employing the above configuration, by utilizing the eccentric holes provided in the upper and lower washers for an anchor bolt that is eccentric within the enlarged hole (anchor bolt insertion hole) of the base plate, when fitting nested washers that can continuously accommodate the anchor bolt from a state where there is no eccentricity to a position where it is at its maximum eccentricity, the position where they can fit together can be accurately grasped by utilizing the indication points on the upper surfaces of the seats, and they can be easily fitted into the enlarged hole of the base plate. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of a case in which a nested washer according to the present invention is applied to an exposed-type column base. [Figure 2] 2(a) and 2(b) are a plan view and a cross-sectional view of an upper washer, which is one of the components of a nested washer used in the exposed-type column base of FIG. 1. [Figure 3] 2(a) to 2(c) are a plan view, a perspective view, and an AA cross-sectional view of a bottom washer, which is the other component of the nested washer used in the exposed-type column base of FIG. [Figure 4] 4 is a cross-sectional view showing the state in which an anchor bolt located at the center of an enlarged hole is fitted to a nested washer consisting of the top washer of FIG. 2 and the bottom washer of FIG. 3. FIG. [Figure 5] 4 is a cross-sectional view showing the state in which an anchor bolt that is off-center in an enlarged hole is fitted to a nested washer made up of the top washer of FIG. 2 and the bottom washer of FIG. 3. FIG. [Figure 6]1(a) and 1(b) are explanatory diagrams showing the relationship between the positions of the eccentric holes in the cylindrical legs of the lower washer and the upper washer and the position of the indicator point on the upper surface of the seat for a nested washer according to a first embodiment of the present invention intended for an M27 anchor bolt. [Figure 7] FIG. 7 is an explanatory diagram showing the rotation angle from the eccentricity reference line when the bottom washer and top washer of the nested washer in FIG. 6 are fitted together in a range from a state where the anchor bolt is not eccentric with respect to the enlarged hole in the base plate (eccentric distance 0 mm) to a state where the anchor bolt is at its maximum eccentricity (eccentric distance 11 mm). [Figure 8] 8 is a graph showing the relationship between the rotation angle and the eccentric distance, which is the distance between the center of the enlarged hole in the base plate and the center of the anchor bolt, for each state in FIG. 7. [Figure 9] 9 is an explanatory diagram showing a procedure for attaching the nested washer of FIG. 6 using the graph of FIG. 8. [Figure 10] FIG. 10 is an explanatory diagram showing the rotation angle from the eccentricity reference line when the components are fitted together, in a range from a state where the anchor bolt is not eccentric with respect to the enlarged hole in the base plate (eccentric distance 0 mm) to a state where it is at its maximum eccentricity (eccentric distance 9 mm), for a nested washer according to a second embodiment of the present invention intended for an M16 anchor bolt. [Figure 11] 11 is a graph showing the relationship between the rotation angle and the eccentric distance, which is the distance between the center of the enlarged hole in the base plate and the center of the anchor bolt, for each state in FIG. 10. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view showing the overall appearance of an example in which a nested washer according to the present invention is applied to an exposed-type column base, with some anchor bolt fastening portions disassembled. Note that the nested washer, which is a characteristic feature of the present invention, and its installation method will be described in detail, mainly with reference to Fig. 9, after explaining the overall structure. The exposed-type column base shown in the figure comprises a base plate 2 fixed to the lower end of a steel column 1 and fixed with anchor bolts 3 protruding above the top surface of the foundation concrete (not shown). The base plate 2 has enlarged holes 4 at its four corners, which are approximately 22 to 50 mm larger than the nominal diameter of the anchor bolt 3 to be applied (M12 to M80). Each anchor bolt 3 is then fastened with two nuts 8, 8, with a washer 7 inserted through it, which is a combination of a nested washer 5 and a plain washer 6, which will be described in detail below.

[0019] 2 and 3 show the upper washer 20 and the lower washer 30 that make up a pair of nested washers 5. The upper washer 20 shown in Fig. 2 has a punched depression 22 formed on the upper surface of a disk-shaped seat 21 as a guide point for positioning, which will be described later, and a cylindrical leg 23 formed concentrically on the lower surface. Furthermore, an anchor bolt receiving hole 24, whose inner diameter matches the shank diameter of the anchor bolt 3, penetrates the seat 21 and the cylindrical leg 23 at a position eccentric to the disk-shaped seat 21.

[0020] 3 has a cylindrical leg 32 whose outer diameter matches the inner diameter of the enlarged hole 4 in the base plate 2 formed concentrically with the seat 31 on the underside of the disk-shaped seat 31, the outer diameter of which is larger than the outer diameter of the seat 21 of the upper washer 20, and a leg receiving hole 33 whose inner diameter matches the outer diameter of the cylindrical leg 23 of the upper washer 20 passes through the seat 31 and the cylindrical leg 32 at a position eccentric to the seat 31. Furthermore, similar to the upper washer 20, a punched depression 34 is formed on the upper surface of the seat 31 as an indication point.

[0021] The index point 22 (recess) of the upper washer 20 and the index point 34 (recess) of the lower washer 30 are provided on peripheral edges shifted radially outward from directly above the positions 23a, 32a of the minimum wall thicknesses t1, t2 of the cylindrical leg 23 and cylindrical leg 32, whose inner sides are eccentric holes. These upper washer 20 and lower washer 30 are used as nested washer 5 by inserting the cylindrical leg 23 of the upper washer 20 into the leg receiving hole 33 of the lower washer 30 and stacking the seats 21, 31 one on top of the other.

[0022] Next, the mechanism of the nested washer 5, which addresses misalignment of the anchor bolt by utilizing their respective eccentric holes, will be described with reference to Figures 4 and 5. The figures show the relationship between the anchor bolt 3, the enlarged hole 4 in the base plate, and the nested washer 5, and are cross-sectional views taken at the positions of the respective tubular legs 23 and 32 to clearly show the fit between them. In Figure 4, the anchor bolt 3 is positioned at the center of the enlarged hole 4 in the base plate 2. In other words, the axis C of the anchor bolt 3 and the center D of the enlarged hole 4 in the base plate 2 coincide, and the anchor bolt 3 is installed as designed. In this case, the fit positions of the upper washer 20 and the lower washer 30 are limited, but as long as this fit state (relative position) is maintained, the tubular leg 32 of the lower washer 30 can be fitted and attached to the enlarged hole 4 in the base plate 2 at any position in the circumferential direction.

[0023] However, when the axis C of the anchor bolt 3 is offset from the center D of the enlarged hole 4 as shown in Figure 5, the positional relationship between the enlarged hole 4 in the base plate 2 and the top washer 20 and bottom washer 30 becomes important, and the anchor bolt can only be installed in a specific position. In the conventional installation method, the bottom washer 30 is first rotated to fit its tubular leg 32 into the enlarged hole 4 in the base plate 2. Next, with the top end of the anchor bolt 3 inserted into the anchor bolt receiving hole 24 of the top washer 20, the top washer 20 is rotated, and the bottom washer 30 is also rotated appropriately to find the fitting position. When the fitting position is reached, the tubular leg 23 of the top washer 20 is completely immersed in the leg receiving hole 33 of the bottom washer 30, and at the same time, the top end of the anchor bolt 3 is properly inserted into the anchor bolt receiving hole 24 of the top washer 20. In this state, as shown in Figure 1, when double nuts 8, 8 (single nuts are also acceptable) are screwed onto the anchor bolt 3 and tightened, the anchor bolt 3 is firmly fixed to the base plate 2 without any large gaps being created within the enlarged hole 4 due to the insert washers 5 (upper washer 20 and lower washer 30), and any positional deviation is also absorbed.

[0024] Next, the nested washer 5 according to the present invention will be described using a specific example with reference to Figures 6 and 7. The specifications of the nested washer vary depending on the size of the anchor bolt, but the most important requirement, the maximum allowable eccentricity distance Emax, can be expressed by the following formula. Emax=2×Eh+CL / 2 Eh: Center of the cylindrical legs of the upper and lower washers (in Figure 6, the center of each seat) Distance from the center of the eccentric hole (A1, B1) to the center of the eccentric hole (A2, B2 in Figure 6) CL: Clearance of the nested washer (between the cylindrical leg 23 of the upper washer 20 and the leg of the lower washer 30) The gap between the cylindrical leg portion 32 of the bottom washer 30 and the base plate 2 (Gap between the enlarged hole 4)

[0025] A first embodiment of a nested washer for an M27 anchor bolt will now be described in detail. As shown in Figures 6(a) and 6(b), in the upper washer 20 and the lower washer 30, when the distance Eh (hereinafter also referred to as the hole eccentric distance) from the centers A1, B1 of the respective cylindrical legs 23, 32 (which are also the centers of the seats 21, 31) to the centers A2, B2 of the eccentric holes 24, 33 is set to 4.5 mm and the clearance CL is set to 4.0 mm, the maximum eccentric distance Emax is 4.5 x 2 + 4.0 / 2 = 11 (mm). In this case, the clearance CL is the result of calculating the gap based on the manufacturing (standard) dimensions of each part. An example of OF-(L)17 provided by the present applicant is as follows: (1) Distance between the inner diameter of the enlarged hole in the base plate (±0) and the outer diameter of the cylindrical leg of the bottom washer: 55.0-53.5=1.5(mm) (2) Distance between the inner diameter of the leg receiving hole of the lower washer and the outer diameter of the cylindrical leg of the upper washer: 41.5-40.5=1.0(mm) (3) Distance between the inner diameter of the anchor bolt receiving hole in the upper washer and the outer diameter of the anchor bolt (±0): 28.5-27.0=1.5(mm) Therefore, the total calculated clearance CL is 4.0 mm. Because the clearance CL is distributed from the center, half of this is used as the clearance in one direction, and in addition to dealing with eccentricity due to the rotation of the top and bottom washers (described below), this is added to the allowable eccentricity (maximum eccentricity Emax) due to the linear movement of both.

[0026] Figure 7 shows the fit between the top washer 20 and bottom washer 30 of the nested washer in Figure 6 when the eccentricity distance E is changed in 1 mm increments over the range from no eccentricity of the anchor bolt 3 relative to the enlarged hole 4 in the base plate 2 to the maximum eccentricity. In other words, the figures with the number [0] in the upper right corner of each of the 12 divided boxes represent the case where the eccentricity distance E = 0 mm, and the figures with the number

[11] represent the case where the eccentricity distance E = 11 mm. The diagram also shows the rotation angles θ1 and θ2 of the indicator point 22 (indicated by a triangle in the figure) on the top washer 20 and the indicator point 34 (indicated by a black triangle in the figure) on the bottom washer 30, which correspond to the positions of the minimum-thickness portions 23 a and 32 a of the respective tubular legs 23 and 32, respectively, when the eccentricity reference line BL (simply referred to as the reference line in the figure) provided near the enlarged hole 4 in the base plate 2 is set to 0°.

[0027] In Figure 7, when the eccentric distance E is 9 mm (point [9]) and the axis C of the anchor bolt 3 is displaced 9 mm to the right relative to the center D of the enlarged hole 4, the position is determined by linear movement along the eccentric reference line BL up to the maximum eccentric distance Emax = 11 mm. Under this condition, the indicator point 22 on the upper washer 20 and the indicator point 34 on the lower washer 30 are located on the eccentric reference line BL. On the other hand, when the eccentric distance E is less than 9 mm (points [9] to [1]), the upper washer 20 and the lower washer 30 must rotate in opposite directions across the eccentric reference line BL. As the eccentric distance E decreases, the rotation angles θ1 and θ2 increase. When the eccentric distance E is 8 mm, the rotation angles θ1 and θ2 are 27°, and when the eccentric distance E is 1 mm, the rotation angles θ1 and θ2 are 84°. At this time, the indicator point 22 of the upper washer 20 and the indicator point 34 of the lower washer 30 are at the same angle with the eccentricity reference line BL in between. When the anchor bolt 3 is not eccentric, the indicator point 22 of the upper washer 20 and the indicator point 34 of the lower washer 30 are in symmetrical positions with the center C of the anchor bolt 3 (which coincides with the center D of the enlarged hole 4) in between.

[0028] Figure 8 is a graph showing the relationship between the distance (eccentricity distance E) from the center D of the enlarged hole 4 in the base plate 2 to the center C of the anchor bolt 3 in the fitted (mounted) state shown in [0] to

[11] in Figure 7, and the positions of the indicator point 22 on the upper washer 20 and the indicator point 34 on the lower washer 30 relative to the eccentricity reference line BL at that time, as rotation angles θ1 and θ2. As is clear from this graph, when the anchor bolt 3 is not eccentric (E = 0 mm), the indicator points 22 and 34 are each at 90° with respect to the eccentricity reference line BL when the center D of the enlarged hole 4 is used as the rotation axis. When the eccentricity distance E is in the range from zero to 9.0 mm, the rotation angles θ1 and θ2 decrease as the eccentricity distance E increases, and when the eccentricity distance E = 9.0 mm, the rotation angles θ1 and θ2 become zero. This graph shows that when the eccentricity distance E is in the range from 9.0 mm to the maximum allowable eccentricity distance of 11.0 mm, linear movement occurs along the eccentricity reference line BL when the eccentricity distance E is 9.0 mm (the positions of the indicator point 22 of the upper washer 20 and the indicator point 34 of the lower washer 30 coincide with the eccentricity reference line BL).

[0029] What is noteworthy in Figures 7 and 8 is that when the eccentricity distance E is in the range of 0 to 9 mm (twice the hole eccentricity distance Eh = 4.5 mm), the position is determined by the rotation of the upper washer 20 and the lower washer 30, but for eccentricity greater than this, the maximum horizontal movement is 1 / 2 of the clearance CL mentioned above, in other words, 2 mm (see

[10] and

[11] in the figures).

[0030] 9(a) to 9(c) are explanatory diagrams showing the procedure for fitting the nested washer shown in Fig. 6 into the enlarged hole 4 in the base plate. In the figures, the anchor bolt 3 is eccentric to the upper right relative to the enlarged hole 4 in the base plate, and the positional relationship is shown assuming that the eccentric distance E from the center D of the enlarged hole 4 to the axis C of the anchor bolt 3 is 5 mm.

[0031] In the installation method of the present invention, as shown in (a), first, a line connecting the center D of the enlarged hole 4 and the axial center C of the anchor bolt 3 is extended in the eccentric direction to form an eccentricity reference line BL, and a mark M is made on the top surface of the base plate 2 with a felt-tip pen or the like at a position on this eccentricity reference line BL, just beyond the enlarged hole 4. In addition, the amount of eccentricity (eccentric distance E), which is the distance between the center D of the enlarged hole 4 and the axial center C of the anchor bolt 3, is read as 5 mm.

[0032] Next, as shown in (b), the rotation angle 56° corresponding to E=5 mm is read from the graph (FIG. 8) showing the relationship between the eccentric distance E and the rotation angles θ1 and θ2, and with the cylindrical leg portion 32 of the bottom washer 30 inserted into the enlarged hole 4, the indicator point 34 is rotated counterclockwise from the position of mark M on the eccentric reference line BL to the position of 56°.

[0033] On the other hand, as for the upper washer 20, as shown in (c), when the anchor bolt 3 is inserted into the anchor bolt receiving hole 24 and its cylindrical leg 23 is placed on the seat 32 of the lower washer 30, the indicator point 22 is rotated clockwise from the position of mark M on the eccentric reference line BL to a position of 56°, and the cylindrical leg 23 of the upper washer 20 fits into the leg receiving hole 33 of the lower washer 30, completing the installation.

[0034] Incidentally, when the top washer 20 is inserted into the anchor bolt 3, its tubular leg 23 naturally fits into the leg receiving hole 33 of the bottom washer 30 within one rotation, regardless of the direction in which it is rotated. For this reason, as long as the index point 34 of the bottom washer 30 can initially be set at an appropriate angle with respect to the eccentricity reference line BL, the fitting position can be easily found and the top washer 20 can be installed by rotating in an appropriate direction even if the index point 22 of the top washer 20 does not exist, and therefore the index point 22 of the top washer 20 is not an essential requirement of the present invention (claim 1). In other words, as described above, the only position where the tubular leg 23 of the top washer 20 can ultimately be fitted into the leg receiving hole 33 of the bottom washer 30 is the position at the same rotational angle as the top washer 20 across the eccentricity reference line BL. Therefore, even if the index point 22 of the top washer 20 does not exist or even without relying on the index point 22, the top washer 20 will naturally fit into the leg receiving hole 33 within one rotation, regardless of the direction in which it is rotated, and installation is easy.

[0035] 9(C), the rotation angles θ1 and θ2 relative to the eccentricity reference line BL do not appear to be the same, but this is because the rotation axes of the upper washer 20 and the lower washer 30 are different, and the angles are the same. Also, the clearance created between the installation members due to the rotation of the upper washer 20 and the lower washer 30 is uniform all around, as shown in the figure. The present invention is characterized in that the indicator points 22 and 34 of the upper washer 20 and the lower washer 30, and in particular the indicator point 34 of the bottom washer 30 which is positioned first, are used as a guide for rotation operation during installation, and in that the eccentricity reference line BL is set in the eccentric direction of the anchor bolt 3 and used as a reference line for rotation operation, which improves the installation work.

[0036] 10 and 11 show a second embodiment of a nested washer according to the present invention, which is intended for an M16 anchor bolt. In this nested washer, the distance Eh (hole eccentricity) from the centers A1, B1 of the cylindrical legs 23, 32 of the upper washer 20 and the lower washer 30 to the centers A2, B2 of the eccentric holes 24, 33 is set to 3.5 mm, and the clearance CL is set to 4.0 mm. As a result, the maximum eccentricity Emax is 3.5 x 2 + 4.0 / 2 = 9.0 (mm).

[0037] In Figure 10, [7] indicates the eccentric distance E = 7 mm, where the axis C of the anchor bolt 3 is displaced 7 mm to the right relative to the center D of the enlarged hole 4. The maximum eccentric distance Emax = 9 mm is determined by linear movement along the eccentric reference line BL (simply labeled "reference line" in the figure). Under these conditions, the indicator point 22 on the upper washer 20 and the indicator point 34 on the lower washer 30 are located on the eccentric reference line BL. On the other hand, when the eccentric distance E is less than 7 mm ([7] to [1]), the upper washer 20 and the lower washer 30 must rotate in opposite directions across the eccentric reference line BL. As the eccentric distance E decreases, the rotation angles θ1 and θ2 increase. For example, when the eccentric distance E is 5 mm, the rotation angles θ1 and θ2 are 56° in the first embodiment (anchor bolt with an M27 diameter) and 45° in the second embodiment (anchor bolt with an M16 diameter). FIG. 11 is a graph showing the relationship between the eccentric distance E and the rotation angle θ of each washer when the eccentric distance E is in the range of 0 to 9 mm.

[0038] In this embodiment, when the eccentric distance E is in the range of 0 to 7 mm (twice the hole eccentric distance Eh = 3.5 mm), the position is determined by the rotation of the top washer 20 and bottom washer 30. For eccentricities greater than this (see [8] and [9] in the figure), the maximum horizontal movement is 1 / 2 of the clearance CL mentioned above, i.e., 2 mm, as in the first embodiment. The relationship between this eccentric distance E and the rotation angles θ1 and θ2 differs for each size of nested washer. However, since the relationship is the same for all sizes of anchor bolts as long as Emax is the same, it is sufficient to prepare these graphs for each size of anchor bolt. In Figure 10, "parent" refers to the bottom washer and "child" refers to the top washer.

[0039] In the above embodiments, the cases where index points 22, 34 are provided on both the top washer 20 and the bottom washer 30 are shown, but once the position of the bottom washer 30 is determined, the position of the top washer 20 is also determined, and it can be fitted within the range of one rotation, so simply having index point 22 on bottom washer 30 will lead to improved installation work. Note that while the mortar-shaped recesses made by a punch have been described as specific examples of index points 22, 34, they can be changed to other shapes such as arrow-shaped or linear, and the means of providing them can be coating or cutting other than stamping.

[0040] Incidentally, when installing nested washers, if the worker is facing downwards as in the case of a steel column base and the installation is within a visible range, work efficiency can be improved by providing an indicator point 34 only on the bottom washer 30 as described above, obtaining the required rotation angle from a graph to position the bottom washer 30, and then rotating the top washer 20 as appropriate. The same can be said for installation in a horizontal position.

[0041] However, in upward installation, limitations are placed on the work location and work posture. Furthermore, because installation is performed against gravity, the method of placing the bottom washer 30 and then stacking the top washer 20, as in downward installation, is often not possible. This makes it difficult to monitor the installation position. This becomes even more difficult when the installation space is narrow or installation is performed blindly. Under these circumstances, as shown in the above example, it is effective to provide indicators on both the top washer 20 and the bottom washer 30 (claim 2). For example, nested washers can be prepared in advance with temporary placement based on the estimated eccentricity direction and distance through prior investigation, and then transported to the installation location and installed in their stacked state. The temporarily placed nested washers can be temporarily fixed with adhesive or other means to prevent the relative positions of the top washer 20 and bottom washer 30 from shifting (changing in rotation angle) during transport to the installation location.

[0042] The present invention is not limited to the above embodiment, and the hole eccentricity distance and clearance amount of the insert washer may be set as desired. Furthermore, the application location is not limited to the column base, and various modifications and implementations are possible within the technical concept of the present invention. [Industrial Applicability]

[0043] The nested washer mounting method according to the present invention and the nested washer used therein demonstrate their advantages when used in buildings such as steel-framed structures, and further development is expected as a means of improving mounting work. [Explanation of symbols]

[0044] 1...steel column, 2...base plate, 3...anchor bolt, 4...enlarged hole, 5...nested washer, 6...flat washer, 7...washer, 8...nut, 20...upper washer, 30...lower washer, 21, 31...seat, 23, 32...cylindrical leg, 24...anchor bolt receiving hole, 22, 34...indicator point, 33...leg receiving hole, A1, B1...center of cylindrical leg, B1, B2...center of eccentric hole, BL...eccentric reference line, C...axis center of anchor bolt, D...center of enlarged hole

Claims

1. A nested washer is comprised of a pair of upper and lower washers each having a concentric cylindrical leg on the underside of the seat, the upper washer has an anchor bolt receiving hole with an inner diameter that matches the outer diameter of the anchor bolt, which passes through the seat and the cylindrical leg at an eccentric position, and the lower washer has a leg receiving hole with an inner diameter that matches the outer diameter of the cylindrical leg of the upper washer, which passes through the seat and the cylindrical leg with an outer diameter that matches the enlarged hole in the base plate at an eccentric position, and the cylindrical leg of the upper washer is inserted into the leg receiving hole of the lower washer and used in a state where they are stacked one on top of the other. A method for installing a nested washer, the nested washer being fitted into an enlarged hole in a base plate for inserting an anchor bolt with the anchor bolt inserted through the upper washer, comprising: a method for fitting a nested washer, the method comprising: measuring an eccentricity distance; setting an eccentricity reference line by extending a line connecting the center of the enlarged hole in the base plate and the axis of the anchor bolt in the eccentric direction to the upper surface of the base plate; aligning the indicator point of the bottom washer with this eccentricity reference line with the eccentricity reference line when the tubular leg is fitted into the enlarged hole in the base plate; rotating the bottom washer to a rotation angle position read from a graph showing the relationship between the eccentricity distance and the rotation angle of the bottom washer; and then rotating the top washer to a predetermined position with the top washer inserted onto the anchor bolt, thereby fitting the tubular leg of the top washer into the leg receiving hole of the bottom washer.

2. 2. The method for installing a nested washer according to claim 1, characterized in that the upper washer has an index point on the peripheral edge of the upper surface of the seat portion corresponding to the position where the thickness of the cylindrical leg portion is at its smallest in the circumferential direction, and is rotated in the opposite direction at the same rotation angle as the lower washer.

3. 3. A nested washer comprising a pair of upper and lower washers used in the method for attaching a nested washer according to claim 1 or 2, characterized in that at least the lower washer is provided with an index point on the peripheral edge of the upper surface of the seat portion corresponding to the position where the wall thickness of the cylindrical leg portion is at its smallest in the circumferential direction.

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