Method for tightening high-strength bolts

Abstract

To provide a fastening method of a high strength bolt capable of stabilizing bearing pressure on a contact surface of a friction plate and a sliding plate constituting a friction damper.SOLUTION: In the method of fastening the high-strength bolt 20 of the friction damper 1, the friction damper 1 includes the friction plate 13, the sliding plate 12 laminated on the friction plate 13, and the high-strength bolt 20 and the nut 21 that penetrate and fasten the friction plate 13 and the sliding plate 12, and when the high-strength bolt 20 is fastened, the high-strength bolt 20 is fastened in three stages until the fastening torque reaches the target tension.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for tightening high-strength bolts that constitute a friction damper. [Background technology]

[0002] BACKGROUND ART Conventionally, friction dampers have been provided in some buildings as vibration dampers to suppress shaking of the building due to earthquakes or strong winds. Patent Document 1 shows a friction damper comprising a middle plate, a pair of splice plates sandwiched between the middle plate, a pair of support plates arranged on the outside of the splice plates, and high-strength bolts and nuts that fasten the pair of support plates together. Patent Document 2 shows a friction damper that includes a middle plate, a pair of outer plates sandwiched between the middle plate, a friction plate interposed between the middle plate and the outer plates, and disc springs, bolts, and nuts that fasten the pair of outer plates together. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-142329 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-266828 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a method for tightening a high-strength bolt that can stabilize the surface pressure on the contact surface between the friction plate and the sliding plate that constitute a friction damper. [Means for solving the problem]

[0005] The method for tightening a high-strength bolt of a friction damper of the first invention is a method for tightening a high-strength bolt (e.g., high-strength bolt 20 described below) of a friction damper (e.g., friction damper 1 described below), in which the friction damper comprises a friction plate (e.g., friction plate 13 described below), a sliding plate (e.g., sliding plate 12 described below) laminated on the friction plate, and a high-strength bolt and nut (e.g., nut 21 described below) that penetrate the friction plate and the sliding plate and tightens them, and is characterized in that when tightening the high-strength bolt, it is tightened in three stages until the tightening torque reaches a target tension.

[0006] Conventionally, when tightening high-strength bolts, the process is carried out in two stages: first, a primary tightening, and then final tightening. In contrast, according to this invention, when tightening the high-strength bolts attached to a friction damper, the tightening torque of the high-strength bolts is divided into three stages until the target tension is reached. Therefore, according to this invention, the increment of the tightening torque introduced in the final stage (third stage) is smaller than in conventional high-strength bolt tightening methods, so the variation in tension introduced to the high-strength bolts can be reduced. As a result, the tension applied by the high-strength bolts becomes approximately uniform, and the surface pressure on the contact surface (friction surface) between the friction plate and sliding plate that make up the friction damper can be stabilized.

[0007] The second invention is a method for tightening high-strength bolts of a friction damper, characterized in that the first stage of tightening is tightened with a torque value corresponding to the nominal diameter of the high-strength bolt, the second stage is tightened with a tightening torque of 80% to 90% of the tightening torque of the target tension, and the third stage is tightened with the tightening torque of the target tension.

[0008] According to this invention, when a high-strength bolt is tightened in three stages, the second stage is tightened with a tightening torque of 80% to 90% of the tightening torque of the target tension, and the third stage is tightened with a tightening torque of the remaining 10% to 20% of the tightening torque of the target tension. This reduces the increment in the tightening torque introduced in the third stage, making it possible to further reduce variation in the tension finally introduced into the high-strength bolt.

[0009] The third invention is a method of tightening a high-strength bolt for a friction damper, characterized in that the friction damper comprises a middle plate (for example, middle plate 10 described below) that can move in a predetermined direction, a pair of splice plates (for example, splice plate 11 described below) that are arranged across the middle plate and can move in the opposite direction to the middle plate in the predetermined direction, a sliding plate (for example, sliding plate 12 described below) and a friction plate (for example, friction plate 13 described below) that are sandwiched between the middle plate and the splice plates, and a pair of support plates (for example, first support plate 14 and second support plate 15 described below) that are arranged on the outside of the splice plates, and the pair of support plates are tightened together with the high-strength bolt and the nut.

[0010] In a friction damper, the sliding plate and friction plate are pressed against each other by the tension of high-strength bolts. According to this invention, the high-strength bolts are tightened in three stages, so the surface pressure on the contact surface between the friction plate and sliding plate can be controlled with high precision, allowing the friction damper to stably demonstrate its vibration-damping performance. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for tightening a high-strength bolt that can stabilize the surface pressure on the contact surface between the friction plate and the sliding plate that constitute a friction damper. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view of a friction damper to which a method for tightening a high-strength bolt according to an embodiment of the present invention is applied. FIG. [Figure 2] FIG. 2 is a vertical cross-sectional view of the friction damper. [Figure 3] FIG. 4 is a perspective view of a second support plate that constitutes the friction damper. [Figure 4] 4 is a flowchart of a procedure for assembling the friction damper. [Figure 5] 1A and 1B are a plan view and a side view of a test specimen used in a tension measurement test. [Figure 6] FIG. 10 is a diagram showing the tightening torque of the primary tightening in a tension measurement test. [Figure 7] FIG. 10 is a diagram showing test results (tension of each bolt) for the comparative example and the example. [Figure 8] FIG. 10 is a diagram showing test results (tension of each bolt) for a comparative example. [Figure 9] FIG. 10 is a diagram showing test results (tension of each bolt) for Example 1. [Figure 10] FIG. 10 is a diagram showing test results (tension of each bolt) for Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0013] This invention is a method for tightening high-strength bolts that make up a friction damper, and involves applying tension to the high-strength bolts in three stages. In the first stage, the bolts are tightened to the conventionally recommended tightening torque to eliminate backlash. In the second stage, the bolts are tightened to a tightening torque that is 80 to 90% of the target tension. In the third stage, the bolts are tightened to a tightening torque that is the target tension. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is a perspective view of a friction damper 1 to which a method for tightening a high-strength bolt according to one embodiment of the present invention is applied. FIG. 2 is a vertical cross-sectional view of the friction damper 1. Friction damper 1 is used as a vibration control device inside a building. This friction damper 1 comprises a middle plate 10 that is movable in a predetermined direction A, a pair of upper and lower splice plates 11 that are provided across the middle plate 10 and are movable in a predetermined direction B opposite to the middle plate 10, a sliding plate 12 and a friction plate 13 that are sandwiched between the middle plate 10 and the upper and lower splice plates 11, a first support plate 14 and a second support plate 15 that are provided on the outside of the splice plate 11, and high-strength bolts 20 and nuts 21 that fasten the first support plates 14 together. Through holes 16, 17, 18 are formed in the middle plate 10, the splice plate 11, and the first support plate 14. Here, the through holes 17, 18 in the splice plate 11 and the first support plate 14 are approximately circular in plan view, but the through hole 16 in the middle plate 10 is an elongated hole. High-strength bolts 20 are inserted through the through holes 16, 17, 18 in the middle plate 10, the splice plate 11, and the first support plate 14, and nuts 21 are tightened.

[0014] The sliding plates 12 and friction plates 13 abut on each other at their contact surfaces and are provided above and below the middle plate 10. The upper sliding plates 12 and friction plates 13 are provided in pairs on both sides of the threaded portion of the high-strength bolt 20. Similarly, the lower sliding plates 12 and friction plates 13 are provided in pairs on both sides of the threaded portion of the high-strength bolt 20.

[0015] A pair of second support plates 15 are provided on the upper side of the upper splice plate 11, one on each side with the threaded portion of the high-strength bolt 20 in between. As shown in Figure 3, a convex portion 19 extending in a predetermined direction is formed on the top surface of the second support plate 15, i.e., the surface facing the first support plate 14. In addition, a pair of second support plates 15 are also provided on the lower side of the lower splice plate 11, one on each side with the threaded portion of the high-strength bolt 20 in between. The first support plate 14 is provided above the upper second support plate 15, and the convex portion 19 of the second support plate 15 abuts against the lower surface of this first support plate 14. In addition, the first support plate 14 is also provided below the lower second support plate 15.

[0016] In the friction damper 1, when the nut 21 is tightened on the high-strength bolt 20 and tension is applied to the high-strength bolt 20, the tension of the high-strength bolt 20 is transmitted to the convex portion 19 of the second support plate 15 via the first support plate 14, and this second support plate 15 applies stress evenly to the contact surface between the sliding plate 12 and the friction plate 13. In addition, in this friction damper 1, due to an earthquake or the like, a tensile force acts on the middle plate 10 in direction A in Fig. 1, and a tensile force acts on the splice plate 11 in direction B in Fig. 1. At this time, the sliding plate 12 and the friction plate 13 slide on their contact surfaces, absorbing the seismic force.

[0017] The procedure for assembling the friction damper 1 will be described below with reference to the flowchart of FIG. In step S1, the middle plate 10, the splice plate 11, the sliding plate 12, the friction plate 13, the first support plate 14, and the second support plate 15 are stacked. In step S2, the first stage of tightening is performed using the high-strength bolts 20 and nuts 21. That is, the high-strength bolts 20 are inserted into the through holes 16-18 of the middle plate 10, the splice plate 11, and the first support plate 14, and the nuts 21 are screwed in to perform the first stage of tightening. In the first stage, tightening is performed with a torque value according to the nominal diameter of the high-strength bolts 20.

[0018] In step S3, the second stage of tightening is performed using the high strength bolt 20 and the nut 21. The second stage of tightening is performed with a tightening torque of 80% to 90% of the tightening torque of the target tension. In step S4, the third stage of tightening is performed using the high strength bolts 20 and nuts 21. The third stage of tightening is performed with a tightening torque of the target tension. According to this high-strength bolt tightening procedure, the first stage of tightening eliminates unevenness in the position of each high-strength bolt, the second stage of tightening eliminates errors in the tension of each high-strength bolt due to elastic deformation of each element, and the third stage of tightening allows for stable introduction of tension.

[0019] [Tension measurement test] For the above friction dampers, a tension measurement test was conducted in which the number of times the high-strength bolts were tightened and the torque of the secondary tightening were changed to measure the tension. Figure 5(a) is a plan view of a specimen used in a tension measurement test, and Figure 5(b) is a side view of the specimen used in a tension measurement test. For this test specimen, the high-strength bolts were M27 (F10T) with a tightening length of 156 mm. There were eight bolts, two per first bearing plate, and the distance between these two bolts was 150 mm for tightening with an electric torque wrench.

[0020] As shown in Fig. 5, the test specimen is provided with two second support plates for one first support plate. The second support plates are provided with protrusions extending in a predetermined direction. The tension acting from the high-strength bolt is transmitted to the convex part of the second bearing plate via the first bearing plate, and stress acts evenly on the contact surface between the sliding plate and the friction plate. Because there is a gap between the first and second bearing plates equal to the height of the convex part, elastic deformation occurs in the first bearing plate. In this test specimen, in order to suppress elastic deformation of the second bearing plate, the thickness of the first bearing plate was set to 36 mm so that it would have bending rigidity approximately 10 times (9.48 times to be exact) the axial rigidity of the high-strength bolt. The high-strength bolts were tightened in order from one end to the other, as shown by the arrows in Figure 5(a). After tightening the bolts on the other end, they were turned back toward the one end.

[0021] In this test, the target tension was set to 270 kN. The relationship between torque Tr and tension N is given by the following formula (1). Tr = k × (d1 × N) (1) Here, k is the torque coefficient and d1 is the nominal diameter. Therefore, if the target tension is 270 kN, the calculated tightening torque at the time of final tightening is 1060 N·m. Additionally, the primary tightening was performed with a torque value according to the nominal diameter of the high-strength bolt, as shown in Figure 6. In this test, M27 high-strength bolts were used, so the primary tightening torque was set to 300 N·m.

[0022] In the comparative example, the high-strength bolts were tightened twice. Specifically, the tightening torque for the primary tightening was 300 N m, and the tightening torque for the final tightening (secondary tightening) was 1060 N m. In Example 1, the high-strength bolts were tightened three times. Specifically, the tightening torque for the primary tightening was 300 N m, the tightening torque for the secondary tightening was 700 N m, which is 66% of the final tightening, and the final tightening (tertiary tightening) was 1060 N m. In Example 2, the high-strength bolts were tightened three times. Specifically, the tightening torque for the primary tightening was 300 N m, the tightening torque for the secondary tightening was 900 N m (85% of the final tightening), and the tightening torque for the final tightening (tertiary tightening) was 1060 N m.

[0023] A strain gauge was attached to the high-strength bolt, and the strain amount at each set torque was measured using the strain gauge. The tension of each bolt was calculated by multiplying this strain amount by the cross-sectional area of ​​the bolt shaft. 7 to 10 are diagrams showing test results (tension of each bolt) for the comparative example and the example. In the comparative example, the variation in tension during final tightening was large, with a maximum error of 8.2% from the target tension of 270 kN during final tightening. On the other hand, in example 1, the variation in tension during final tightening was slightly improved, with an error of 7.6% from the target tension of 270 kN during final tightening. On the other hand, in example 2, the variation was small, with a maximum error of 4.2% from the target tension of 270 kN during final tightening. Therefore, it can be seen that the error is reduced by tightening three times, and that the error can be reduced more effectively by tightening with a torque of about 85% of the final tightening.Furthermore, it can be seen that with the high-strength bolt tightening method of the present invention, the error from the target tension, which was about ±10% in the past, can be reduced to about ±5% without using special devices such as disc springs.

[0024] According to this embodiment, the following effects are obtained. (1) When tightening the high-strength bolts 20 attached to the friction damper 1, the tightening torque of the high-strength bolts 20 is divided into three stages until the target tension is reached. Therefore, compared to conventional high-strength bolt tightening methods, the increment of the tightening torque introduced in the final stage (third stage) is smaller, making it possible to suppress variations in the tension finally introduced to the high-strength bolts 20. As a result, the tension applied by the high-strength bolts 20 becomes approximately uniform, and the surface pressure on the contact surface (friction surface) between the friction plate 13 and sliding plate 12 that make up the friction damper 1 can be stabilized.

[0025] (2) When the high-strength bolt 20 is tightened in three stages, the second stage is tightened with a tightening torque of 80% to 90% of the tightening torque of the target tension, and the third stage is tightened with a tightening torque of the remaining 10% to 20% of the tightening torque of the target tension. This reduces the increment of the tightening torque introduced in the third stage, making it possible to further reduce the variation in the tension finally introduced to the high-strength bolt. (3) In the friction damper 1, the sliding plate 12 and the friction plate 13 are pressed against each other by the tension of the high-strength bolts 20. However, since the high-strength bolts 20 are tightened in three stages, the surface pressure at the contact surface between the sliding plate 12 and the friction plate 13 can be controlled with high precision, and the vibration damping performance of the friction damper 1 can be demonstrated.

[0026] The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. For example, in the above-described embodiment, a method for tightening the high-strength bolts 20 that constitute the friction damper 1 is shown, but this is not limited to this, and the present invention may also be applied to a method for tightening high-strength bolts when joining multiple stacked steel materials together with high-strength bolts. [Explanation of symbols]

[0027] 1...Friction damper 10...Intermediate plate 11...Splice plate 12...Sliding plate 13...Friction plate 14...First support plate 15...Second support plate 16...Through hole 17...Through hole 18...Through hole 19...Convex portion 20...High strength bolt 21...Nut

Claims

1. A method for tightening high-strength bolts of a friction damper, comprising the steps of: the friction damper includes a friction plate, a sliding plate laminated on the friction plate, and a high-strength bolt and nut that penetrate the friction plate and the sliding plate and fasten them together; A method for tightening a high-strength bolt of a friction damper, characterized in that when tightening the high-strength bolt, the bolt is tightened in three stages until the tightening torque reaches the target tension.

2. The first stage of the three-stage tightening is performed with a torque value according to the nominal diameter of the high-strength bolt, The second stage tightening is performed with a tightening torque of 80% to 90% of the tightening torque of the target tension, 2. The method for tightening a high-strength bolt of a friction damper according to claim 1, wherein the third-stage tightening is performed with a tightening torque of a target tension.

3. The friction damper includes a middle plate that is movable in a predetermined direction; a pair of splice plates disposed on either side of the middle plate and movable in a direction opposite to the middle plate in the predetermined direction; a sliding plate and a friction plate sandwiched between the intermediate plate and the splice plate; a pair of support plates provided on the outer sides of the splice plate; 3. The method for tightening a high-strength bolt of a friction damper according to claim 1, wherein the pair of bearing plates are tightened together by the high-strength bolt and the nut.

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