Method for evaluating shear strength of rotation prevention key, method for manufacturing steel pipe connection device, and steel pipe connection device

Abstract

To provide an evaluation method capable of accurately evaluating the shear strength of a rotation prevention key in a steel pipe connecting device.SOLUTION: On an outer surface of a rotation preventing key 20, a first imaginary line V1 overlapping with a boundary line B between a box joint 13 and a pin joint 14 in a fitting recess 19 to which the rotation preventing key 20 is attached, and a second imaginary line V2 and a third imaginary line V3 respectively connecting both ends of the first imaginary line V1 with the center C of a counterbore 222 of a counterbore bolt hole 19 for a bolt that fixes the rotation preventing key 20 are assumed, and the distance from one end of the first imaginary line V1 to an intersection point of the second imaginary line V2 and an edge of the counterbore 222 is defined as b1, and the distance from the other end of the first imaginary line V1 to an intersection point of the third imaginary line V3 and the edge of the counterbore 222 is defined as b2. The shear strength TS is calculated using the following formula, where t and σ1 are the thickness and yield stress of the rotation preventing key 20, respectively, and k is a correction coefficient.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a steel pipe connecting device for connecting the ends of steel pipes that constitute a steel pipe pile so that they cannot rotate relative to each other. [Background technology]

[0002] A known example of the above-mentioned steel pipe connecting device is one in which a rotation prevention key is fixed with a bolt to a fitting recess provided across the outer circumferential surface of a box joint welded to the upper steel pipe and the outer circumferential surface of a pin joint welded to the lower steel pipe (Patent Document 1).When a steel pipe pile connected by the steel pipe connecting device of Patent Document 1 is installed, the rotational torque applied to the upper steel pipe is transmitted to the lower steel pipe via the box joint and pin joint, whose relative rotation is prevented by the rotation prevention key.

[0003] In manufacturing the above steel pipe connecting device, the shape parameters of the rotation restraining key are determined so that it has the shear strength to transmit the rotation torque without breaking. S The following formula was used to calculate

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[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-65525 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the inventors of the present application verified the shear strength of the rotation prevention key, they found that there was a certain degree of difference between the value calculated using the above formula and the actual value. Due to the existence of this difference, the settings of the shape parameters of the rotation prevention key during the manufacture of the steel pipe connecting device were not sufficiently appropriate, and there was room for improvement.

[0006] Therefore, an object of the present invention is to provide a method for evaluating the shear strength of a rotation prevention key, a method for manufacturing a steel pipe connecting device, and a steel pipe connecting device that solve the above-mentioned problems. [Means for solving the problem]

[0007] To achieve the above object, the evaluation method according to the present invention comprises: A box joint and a pin joint that can be connected to each other so as to have the same axis; a rotation prevention key that is attached to a fitting recess provided across both the outer peripheral surface of the box joint and the outer peripheral surface of the pin joint and that prevents relative rotation between the box joint and the pin joint around the axis; A method for evaluating the shear strength of a rotation restraint key in a steel pipe connecting device, the method comprising: inserting a bolt mounting hole with a counterbore provided in either a region of the rotation restraint key on the box joint side or a region of the pin joint side of the rotation restraint key, screwing the bolt into the box joint or the pin joint, and fixing the rotation restraint key in the fitting recess; On the outer surface of the rotation prevention key, a first imaginary line overlapping a boundary line between the box joint and the pin joint in the fitting recess; a second imaginary line connecting one end of the first imaginary line and the center of the counterbore; A third imaginary line is assumed to connect the other end of the first imaginary line and the center of the counterbore; a distance from the one end of the first imaginary line to an intersection point between the second imaginary line and an edge of the counterbore is defined as b1; When the distance from the other end of the first imaginary line to the intersection point between the third imaginary line and the edge of the countersink is b2, Shear strength T of the rotation prevention key S is calculated using the following formula:

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[0008] When rotational torque is transmitted through the rotation restraining key, shear stress acts on the rotation restraining key. Conventionally, it was thought that shear stress acts along the width direction of the rotation restraining key, but the inventors of the present application discovered that when the rotation restraining key is provided with a counterbore bolt mounting hole, the shear stress acts from a portion of the edge of the rotation restraining key near the boundary between the box joint and the pin joint toward the counterbore. Therefore, the inventors of the present application calculated the shear strength T S The calculation formula for is defined as above.

[0009] The above formula incorporates "(b1 + b2) × t" which represents the area closer to the area of ​​the surface on which the shear stress actually acts. Furthermore, the above formula incorporates a correction coefficient k to make the uncorrected value closer to the actual value. Therefore, according to the above formula, the shear strength T of the rotation prevention key is S can be more accurately evaluated.

[0010] In order to achieve the above object, the manufacturing method according to the present invention comprises the steps of: A box joint and a pin joint that can be connected to each other so as to have the same axis; a rotation prevention key that is attached to a fitting recess provided across both the outer peripheral surface of the box joint and the outer peripheral surface of the pin joint and that prevents relative rotation between the box joint and the pin joint around the axis; A method for manufacturing a steel pipe connecting device comprising: a bolt that is inserted through a countersunk bolt mounting hole provided in either the box joint side region or the pin joint side region of the rotation restraint key and threadedly engages with the box joint or the pin joint, and fixes the rotation restraint key in the fitting recess, On the outer surface of the rotation prevention key, a first imaginary line overlapping a boundary line between the box joint and the pin joint in the fitting recess; a second imaginary line connecting one end of the first imaginary line and the center of the counterbore; A third imaginary line is assumed to connect the other end of the first imaginary line and the center of the counterbore; a distance from the one end of the first imaginary line to an intersection point between the second imaginary line and an edge of the counterbore is defined as b1; When the distance from the other end of the first imaginary line to the intersection point between the third imaginary line and the edge of the countersink is b2, Shear strength T of the rotation prevention key S Calculating using the following formula:

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[0011] As described above, the shear strength T S The calculation formula for shear strength T S Therefore, this shear strength T S According to the above manufacturing method using the calculation formula, the desired shear strength T SThis makes it possible to more appropriately set the shape parameters of the rotation restraint key required to obtain this, namely the thickness t of the rotation restraint key and the distances b1 and b2 from the part of the edge of the rotation restraint key near the boundary between the box joint and the pin joint to the countersink.

[0012] In the manufacturing method according to the present invention, the rotation prevention key is substantially rectangular and has a box joint side edge portion entirely located on the box joint side, a pin joint side edge portion entirely located on the pin joint side, and two bearing edge portions spanning the box joint and the pin joint, the rotation restraint key is arranged so that the box joint side edge portion and the pin joint side edge portion are parallel to the boundary line and the two bearing edge portions are parallel to the axis, A fourth imaginary line is assumed to be parallel to the axis on the outer surface of the rotation prevention key; The distance from the intersection of the fourth virtual line and the box joint side edge portion to the intersection of the fourth virtual line and the first virtual line is L1, When the distance from the intersection of the fourth imaginary line and the pin joint side edge portion to the intersection of the fourth imaginary line and the first imaginary line is L2, The bearing strength T of the first bearing portion located on the box joint side of each of the bearing edge portions B1 Calculating using the following formula:

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[0013] When rotation torque is transmitted through the rotation restraining key, not only shear stress but also bearing stress acts on the rotation restraining key. The total strength of the rotation restraining key against these stresses is the shear strength against shear stress T S and the bearing strength T against the bearing stress B1 , T B2 Therefore, b1, b2, L1, L2 and t of the rotation prevention key are determined according to the minimum value of the shear strength T S , bearing strength T B1 and bearing strength T B2 The minimum value of L1 and L2 is set to be equal to or greater than the threshold value required to obtain the desired overall strength. However, depending on the values ​​of L1 and L2, the shear strength T S and the bearing strength of the area where no bolt mounting holes are provided (bearing strength T B1 and bearing strength T B2 may not match.

[0014] Here, the rotation restraint key has a bolt mounting hole in the pin joint side area, and the shear strength T S , bearing strength T B1 and bearing strength T B2 Of which, shear strength T S The adjustment of L1 and L2 will be explained using the case where is the minimum value as an example.

[0015] As an example, the shear strength T S increases and the bearing capacity T B1 To reduce the bearing capacity T B1 is constant and the shear strength T SL2 can be increased without changing L1 so that the shear strength T S , bearing strength T B1 and bearing strength T B2 The minimum shear strength T S In other words, the above manufacturing method can provide a rotation preventing key with a higher overall yield strength.

[0016] Another example is the shear strength T S is constant and the bearing capacity T B1 L1 can be reduced without changing L2 so that the shear strength T S , bearing strength T B1 and bearing strength T B2 The minimum shear strength T S In other words, the above manufacturing method makes it possible to obtain a rotation preventing key that is compact while maintaining the overall strength.

[0017] In the manufacturing method according to the present invention, it is preferable that in the adjustment, both L1 and L2 are adjusted so that the sum of L1 and L2 is constant.

[0018] According to the manufacturing method configured as above, it is possible to obtain a rotation preventing key having a higher overall strength while maintaining the height dimension.

[0019] In the manufacturing method according to the present invention, it is preferable that only one of L1 and L2 is adjusted.

[0020] According to the above configuration, it is only necessary to adjust either L1 or L2, so the settings for L1 and L2 are simplified.

[0021] In the manufacturing method according to the present invention, it is preferable that the bolt mounting hole is provided in a region of the rotation preventing key on the pin joint side.

[0022] In the case of this configuration, when L1 is adjusted to be small, the mating recess in the box joint, in which the rotation prevention key is attached, is positioned away from the groove provided on the inner surface of the box joint, in which the load transmission key for preventing the box joint and the pin joint from coming loose is attached, and therefore the strength of the area between the mating recess and the groove increases and cross-sectional defects are less likely to occur.

[0023] In the manufacturing method according to the present invention, it is preferable that the bolt mounting holes are provided at positions where b1=b2.

[0024] According to the above configuration, the shear strength of the portions of the rotation preventing key located on both the left and right sides of the bolt mounting hole is uniform, which is preferable.

[0025] In order to achieve the above object, the steel pipe connecting device according to the present invention comprises: A box joint and a pin joint that can be connected to each other so as to have the same axis; a rotation prevention key that is attached to a fitting recess provided across both the outer peripheral surface of the box joint and the outer peripheral surface of the pin joint and that prevents relative rotation between the box joint and the pin joint around the axis; a bolt that is inserted through a bolt mounting hole with a counterbore provided in one of the box joint side region and the pin joint side region of the rotation restraint key and threadedly engages with the box joint or the pin joint, thereby fixing the rotation restraint key in the fitting recess, the rotation prevention key is substantially rectangular and has a box joint side edge portion entirely located on the box joint side, a pin joint side edge portion entirely located on the pin joint side, and two bearing edge portions spanning the box joint and the pin joint, the rotation prevention key is arranged so that the box joint side edge portion and the pin joint side edge portion are parallel to the boundary line between the box joint and the pin joint in the fitting recess, and so that the two bearing edge portions are parallel to the axis, On the outer surface of the rotation prevention key, a first imaginary line that overlaps the boundary line; a second imaginary line connecting one end of the first imaginary line and the center of the counterbore; a third imaginary line connecting the other end of the first imaginary line and the center of the counterbore; a fourth imaginary line parallel to the axis; a distance from the one end of the first imaginary line to an intersection point between the second imaginary line and an edge of the counterbore is defined as b1; a distance from the other end of the first imaginary line to an intersection point between the third imaginary line and an edge of the countersink is defined as b2; The distance from the intersection of the fourth virtual line and the box joint side edge portion to the intersection of the fourth virtual line and the first virtual line is L1, When the distance from the intersection of the fourth imaginary line and the pin joint side edge portion to the intersection of the fourth imaginary line and the first imaginary line is L2, Shear strength T of the rotation prevention key S is expressed by the following formula:

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[0026] According to the above configuration, a steel pipe connecting device equipped with a rotation prevention key having a higher overall strength can be obtained. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a partial cross-sectional view showing a steel pipe pile equipped with a steel pipe connecting device according to the present invention. [Figure 2] FIG. [Figure 3] FIG. 10 is a diagram schematically illustrating the strain distribution of a rotation prevention key. [Figure 4] 10 is a graph showing the relationship between the engagement length of the rotation prevention key and the bearing strength of the rotation prevention key. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of the steel pipe connecting device and the related evaluation method and manufacturing method of the present invention will be described with reference to the drawings.

[0029] [Steel pipe connection device] FIG. 1 shows a steel pipe pile 10 constructed by connecting the opposing ends of vertically adjacent steel pipes 11 using a steel pipe connecting device 12. The steel pipe connecting device 12 is equipped with a female box joint 13 welded to the lower end of the upper steel pipe 11A and a male pin joint 14 welded to the upper end of the lower steel pipe 11B. The upper steel pipe 11A and the lower steel pipe 11B can be connected via the box joint 13 and the pin joint 14 so as to have the same axis X. Specifically, after inserting the pin joint 14 into the box joint 13, a load transmission key 15 incorporated in an inward groove 131 formed on the inner circumferential surface of the box joint 13 is pushed out by operating a set bolt 16 to a position spanning an outward groove 141 formed on the outer circumferential surface of the pin joint 14 so as to face the inward groove 131. This secures the upper steel pipe 11A and the lower steel pipe 11B in a non-disconnected state.

[0030] As shown in Figure 2, a downward notch 17 is provided on the lower edge of the outer peripheral surface of the box joint 13. An upward notch 18 is provided on the upper edge of the outer peripheral surface of the pin joint 14 at a position corresponding to the downward notch 17. When the pin joint 14 is inserted into the box joint 13, the downward notch 17 and the upward notch 18 form a fitting recess 19 that is generally rectangular in front view and cross section.

[0031] The upper steel pipe 11A and the lower steel pipe 11B are prevented from rotating relatively around the axis X by fitting a rotation prevention key 20 in the fitting recess 19. The rotation prevention key 20 is configured to have a generally rectangular shape in front view and cross section, and has a box joint side edge 201 located entirely on the box joint 13 side, a pin joint side edge 202 located entirely on the pin joint 14 side, and two support edges 203 that straddle the box joint 13 and the pin joint 14. In this embodiment, the rotation prevention key 20 is arranged so that the box joint side edge 201 and the pin joint side edge 202 are parallel to the boundary line B between the box joint 13 and the pin joint 14 in the fitting recess 19, and so that the two support edges 203 are parallel to the axis X.

[0032] The rotation restraint key 20 is fixed in the fitting recess 19 by a bolt 21. The rotation restraint key 20 is provided with a bolt mounting hole 22 having a through hole 221 through which the shank 211 of the bolt 21 is inserted and a counterbore 222 into which the head 212 of the bolt 21 is accommodated. In this embodiment, the bolt mounting hole 22 is provided in an area of ​​the rotation restraint key 20 on the pin joint 14 side so that the rotation restraint key 20 can be fixed to the pin joint 14. The bolt 21 is threaded into a bolt hole 142 provided in an upward notch 18 provided in the pin joint 14.

[0033] [Evaluation of the resistance of rotation prevention keys] In a steel pipe pile 10 configured as described above, when a rotational torque is applied to the upper steel pipe 11A, the downward notch 17 of the box joint 13 abuts against the first support portion 203A located on the box joint 13 side of the support edge portion 203 of one side of the rotation prevention key 20 (the right side in the example of Figure 2), thereby transmitting the rotational torque from the upper steel pipe 11A to the rotation prevention key 20 via the box joint 13; and the second support portion 203B located on the pin joint 14 side of the support edge portion 203 of the other side of the rotation prevention key 20 (the left side in the example of Figure 2) abuts against the upward notch 18 of the pin joint 14, thereby transmitting the rotational torque from the rotation prevention key 20 to the lower steel pipe 11B via the pin joint 14.

[0034] As described above, when rotation torque is transmitted through the rotation restraining key 20, compressive loads and shear loads are applied to the rotation restraining key 20, and shear stress and bearing stress act on the rotation restraining key 20. The total strength T of the rotation restraining key 20 against these stresses is a can be expressed by the following formula (1), for example.

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[0035] Below, bearing capacity T B1 , bearing strength T B2 and shear strength T S We will explain how to calculate this.

[0036] <Shear strength T S 〉 As mentioned above, when rotational torque is transmitted through the rotation restraining key 20, shear stress acts on the rotation restraining key 20, and it is known that the magnitude of the shear strength of the rotation restraining key 20 against this shear stress is determined mainly by the area of ​​the surface on which the shear stress acts and the yield strength of the rotation restraining key 20. Therefore, in the past, it was assumed that the shear stress acts along a surface of the rotation restraining key 20 that is parallel to the boundary line B and at the same height, and the shear strength T of the rotation restraining key 20 was calculated. S The formula for calculating is defined as follows:

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[0037] Incidentally, the inventors of the present application analyzed the strain distribution when a rotational torque was applied to the rotation prevention key 20 using a digital image correlation method, and obtained the strain distribution shown in Figure 3. As shown in Figure 3, a relatively large strain was generated from the portion of the bearing edge 203 near the boundary line B to the counterbore 222 of the bolt mounting hole 22. This shows that the shear stress was acting from the portion of the bearing edge 203 near the boundary line B toward the counterbore 222. As such, there is a discrepancy between the area of ​​the surface on which the shear stress actually acts and the area used in the conventional formula, and therefore the shear strength T calculated by the conventional formula Sis thought to differ to some extent from the actual figures.

[0038] Therefore, the inventor of the present application has developed a shear strength T S The calculation formula was newly defined as follows: That is, as shown in Figure 2, A first imaginary line V1 overlapping the boundary line B between the box joint 13 and the pin joint 14 in the fitting recess 19 on the outer surface of the rotation preventing key 20; a second imaginary line V2 connecting one end of the first imaginary line V1 and the center C of the counterbore 222; A third imaginary line V3 is assumed to connect the other end of the first imaginary line V1 and the center C of the counterbore 222. The distance from one end of the first imaginary line V1 to the intersection of the second imaginary line V2 and the edge of the counterbore 222 is defined as b1, When the distance from the other end of the first imaginary line V1 to the intersection point between the third imaginary line V3 and the edge of the counterbore 222 is b2, Shear strength T of rotation prevention key 20 S is calculated using the following formula (2).

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[0039] In the above formula (2), instead of "b × t" in the conventional formula, "(b1 + b2) × t" is used, which represents an area closer to the area of ​​the surface on which the shear stress actually acts, as shown in FIG. 3. Furthermore, in the above formula (2), a correction coefficient k is used to make the uncorrected numerical value closer to the actual numerical value. The correction coefficient k is set based on the correlation between the uncorrected numerical value and a numerical value obtained by an experiment or the like. In this embodiment, k is set to 0.9, but this is not limited to this.

[0040] For verification purposes, Table 1 shows the shear strength T obtained by the conventional formula, the above formula (2), and experiments for a number of samples of the steel pipe connecting device 12 having the above structure. SIn these samples, the bolt mounting holes 22 of the rotation prevention keys 20 are positioned so that b1 = b2. The t of the rotation prevention keys 20 is 13 mm in all cases, and σ1 is 980 N / mm 2 It was. [Table 1]

[0041] The experimental values ​​in Table 1 were obtained using the SF method. Specifically, the yield load was determined when the gradient of the load-displacement curve reached one-third of the initial gradient.

[0042] As can be seen from Table 1, for all samples, the values ​​calculated using the formula (2) of the present invention were closer to the experimental values ​​than the values ​​calculated using the conventional formula. That is, according to the formula (2) of the present invention, the shear strength T of the rotation prevention key 20 used in the steel pipe connecting device 12 having the above-mentioned structure can be calculated. S can be more accurately evaluated.

[0043] <Bearing strength T B1 , bearing strength T B2 〉 As described above, a bearing stress acts on each bearing edge portion 203 of the rotation preventing key 20. The bearing stress resistance T B1 and the bearing strength T of the second bearing portion 203B B2 The magnitude of the bearing stress T is determined mainly depending on the area of ​​the surface on which the bearing stress acts and the yield strength of the rotation preventing key 20. B1 , bearing strength T B2 is defined as follows: That is, as shown in Figure 2, A fourth imaginary line V4 is assumed to be parallel to the axis X on the outer surface of the rotation preventing key 20, The distance from the intersection of the fourth imaginary line V4 and the box joint side edge 201 to the intersection of the fourth imaginary line V4 and the first imaginary line V1 (substantially the same as the engagement length of the rotation restricting key 20 with the box joint 13) is defined as L1, When the distance from the intersection of the fourth imaginary line V4 and the pin joint side edge 202 to the intersection of the fourth imaginary line V4 and the first imaginary line V1 (substantially the same as the engagement length of the rotation restricting key 20 with the pin joint 14) is L2, The bearing strength T of the first bearing portion 203A located on the box joint 13 side of each bearing edge portion 203 B1 is calculated using the following formula (3), and the bearing strength T of the second bearing portion 203B located on the pin joint 14 side of each bearing edge portion 203 is calculated. B2 is calculated using the following formula (4).

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[0044] [Method for manufacturing steel pipe connecting device] In manufacturing the steel pipe connecting device, the total strength T of the rotation restraint key 20 is set to 1 / 20 so that the rotation restraint key 20 can transmit the rotation torque without breaking. a must be greater than or equal to the expected rotational torque.

[0045] Overall strength T a In the above formula (1) for calculating "min(T S , T B1 , T B2 ) is the desired total strength T a , diameter D, number N, premium coefficient γ ex and safety factor γ s The threshold is determined depending on the shear strength T S , bearing strength T B1 and bearing strength T B2 By setting the minimum value of these to a threshold value or greater, the desired overall strength T a The shear strength T S , bearing strength T B1 and bearing strength T B2 The minimum value of the threshold is the shear strength T S , bearing strength T B1 and bearing strength TB2 This means that all of the above are equal to or greater than the threshold.

[0046] Therefore, in the manufacturing method according to the present invention, the shear strength T of the rotation preventing key 20 is calculated using the above formulas (2), (3), and (4). S , bearing strength T B1 and bearing strength T B2 Calculate the shear strength T S , bearing strength T B1 and bearing strength T B2 is the desired total strength T a b1, b2, L1, L2 and t of the rotation restraint key 20 are set so that they are equal to or greater than threshold values ​​determined based on the above factors. Then, the rotation restraint key 20, box joint 13 and pin joint 14 are manufactured based on the set b1, b2, L1, L2 and t.

[0047] Furthermore, in the manufacturing method according to the present invention, the set lengths L1 and L2 of the rotation prevention key 20 may be adjusted as described below.

[0048] FIG. 4 shows the bearing pressure resistance T according to the engagement length L1 when the installation position of the bolt mounting hole 22 in the rotation prevention key 20 is constant. B1 and shear strength T according to the applied length L2 S and bearing strength T B2 In the example of Figure 4, the shear strength T S and bearing strength T B2 Both of these increase with increasing L2, and when L2 is between 15mm and 35mm, the shear strength T S is the bearing strength T B2 On the other hand, the bearing strength T B1 increases with increasing L1, and the bearing capacity T when L1 is 17.5 mm B1 is the shear strength T when L2 is 32.5 mm S When L1 is 25mm, the bearing capacity T B1 is the bearing capacity T when L2 is 25 mm B2 is equal to

[0049] As shown in Figure 4, depending on the values ​​of L1 and L2, the shear strength T S and the bearing pressure resistance T of the area where the bolt mounting holes 22 are not provided (in this embodiment, the area on the box joint 13 side). B1 In such a case, at least one of L1 and L2 is adjusted so that the two come closer to each other.

[0050] Here, L1 and L2 are both set to 25 mm (i.e., the rotation prevention keys 20 with a height of 50 mm are arranged symmetrically above and below the boundary line B), and the shear strength T S than the bearing strength T B1 and bearing strength T B2 However, it goes without saying that the following methods can be applied even when L1 and L2 are set to other dimensions.

[0051] One method is to use the shear strength T S Increase L2 to more than 25mm and increase bearing capacity T B1 L1 is set to be less than 25mm so that the shear strength T S , bearing strength T B1 and bearing strength T B2 The smallest shear strength T S rises, so "min(T S , T B1 , T B2 The total strength T of the rotation prevention key 20 is determined according to a will also rise.

[0052] In this method, adjustment may be made so that the sum of L1 and L2 is constant, i.e., L1 is reduced by the amount that L2 is increased. In this case, the rotation restraining key 20 after adjustment will be positioned closer to the pin joint 14 side (positioned asymmetrically above and below the boundary line B) while maintaining its height dimension. This reduces the overall strength T aNot only does this increase the shear strength T S and bearing strength T B1 (In the example in Figure 4, L1 is 17.5 mm and L2 is 32.5 mm) S , T B1 , T B2 )" is the maximum value, which is preferable.

[0053] In other methods, by making only L1 smaller than 25 mm without changing L2, the bearing capacity T B1 is the shear strength T S In this case, the rotation prevention key 20 after adjustment will have a smaller height, but it will be closer to "min(T S , T B1 , T B2 )" does not decrease, so the overall strength T a is the same as before adjustment. Therefore, according to this method, the total strength T a This reduces the height of the rotation preventing key 20, thereby reducing production costs, without lowering the operating temperature. Furthermore, even with this method, the cross-sectional area of ​​the thin-walled portion between the downward notch 17 and the inward groove 131 increases, as described above, making it less likely that cross-sectional loss will occur in the box joint 13.

[0054] On the other hand, by increasing only L2 to more than 25 mm without changing L1, the shear strength T S is the bearing strength T B1 In this case, the rotation restraining key 20 after adjustment may be adjusted to approach the minimum shear strength T S rises, so "min(T S , T B1 , T B2 The total strength T of the rotation prevention key 20 is determined according to a will also rise.

[0055] In the manufacturing method according to the present invention, at least one of the adjusted L1 and L2 is taken into consideration when manufacturing the rotation prevention key 20, the box joint 13, and the pin joint 14.

[0056] The desired total strength T of the rotation prevention key 20 a can be determined according to the maximum rotational torque of the construction machine, for example.

[0057] [Another embodiment] (1) In the above-described embodiment, the method for evaluating the strength of the rotation prevention key 20 and the method for manufacturing the steel pipe connection device 12 were described using as an example a steel pipe connection device 12 in which the bolt mounting hole 22 is provided in the region of the rotation prevention key 20 on the pin joint 14 side, but the present invention is not limited to this. In the steel pipe connection device 12, the bolt mounting hole 22 may be provided in the region of the rotation prevention key 20 on the box joint 13 side. In this case, the bolt 21 for fixing the rotation prevention key 20 is threaded into a bolt mounting hole (not shown) provided in communication with both the box joint 13 and the pin joint 14, for example.

[0058] The method for evaluating the strength of the rotation prevention key 20 and the method for manufacturing the steel pipe connecting device 12 can also be applied to the steel pipe connecting device 12 of this embodiment, as described above. However, the shear strength T calculated using the above formula (2) S In the above-mentioned embodiment, the bearing strength T B2 In this embodiment, the bearing strength T B1 , and the area of ​​the rotation preventing key 20 where the bolt mounting holes 22 are not provided is the area on the pin joint 14 side. S and the bearing capacity T of the area on the pin joint 14 side B2 If they do not match, at least one of L1 and L2 is adjusted.

[0059] (2) In the above-described embodiment, the method for evaluating the strength of the rotation prevention key 20 and the method for manufacturing the steel pipe connecting device 12 were explained using the steel pipe connecting device 12 in which the bolt mounting holes are provided at positions where b1 = b2. However, the present invention is not limited to this.<b2またはb1> In this case, the value of (b1 + b2) may differ from that of the above embodiment, so the shear strength T calculated using the above formula (2) S Although the shear strength T S Bearing strength T B1 and bearing strength T B2 Since the correlation between the above is the same as that shown in Figure 4, the method for evaluating the strength of the rotation prevention key 20 and the method for manufacturing the steel pipe connection device 12 can also be applied to the steel pipe connection device 12 of this embodiment, as described above. [Explanation of symbols]

[0060] 10: Steel pipe pile 11, 11A, 11B: Steel pipe 12: Steel pipe connection device 13: Box joint 131: Inward groove 14: Pin joint 141: Outward groove 142: Bolt hole 15: Load transmission key 16: Set bolt 17: Downward notch 18: Upward notch 19: Fitting recess 20: Rotation suppression key 201: Box joint side edge 202: Pin joint side edge 203: Bearing edge 203A: First bearing section 203B: Second bearing section 21: Bolt 211: Shaft 212: Head 22: Bolt mounting hole 221:Through hole 222: Counterbore B: Boundary line C: Center V1: First virtual line V2: Second virtual line V3: Third virtual line V4: Fourth virtual line X: Axial center

Claims

1. A box joint and a pin joint that can be connected to each other so as to have the same axis; a rotation prevention key that is attached to a fitting recess provided across both the outer peripheral surface of the box joint and the outer peripheral surface of the pin joint and that prevents relative rotation between the box joint and the pin joint around the axis; A method for evaluating the shear strength of a rotation restraint key in a steel pipe connecting device, the method comprising: inserting a bolt mounting hole with a counterbore provided in either a region of the rotation restraint key on the box joint side or a region of the pin joint side of the rotation restraint key, screwing the bolt into the box joint or the pin joint, and fixing the rotation restraint key in the fitting recess; On the outer surface of the rotation prevention key, a first imaginary line overlapping a boundary line between the box joint and the pin joint in the fitting recess; a second imaginary line connecting one end of the first imaginary line and the center of the counterbore; A third imaginary line is assumed to connect the other end of the first imaginary line and the center of the counterbore; a distance from the one end of the first imaginary line to an intersection point between the second imaginary line and an edge of the counterbore is defined as b1; When the distance from the other end of the first imaginary line to the intersection point between the third imaginary line and the edge of the countersink is b2, Shear strength T of the rotation prevention key Ｓ and calculating the value using the following formula: [Equation 1] (where t is the thickness of the rotation restraint key, and σ １ is the yield stress of the rotation restraint key, and k is a predetermined correction factor.

2. A box joint and a pin joint that can be connected to each other so as to have the same axis; a rotation prevention key that is attached to a fitting recess provided across both the outer peripheral surface of the box joint and the outer peripheral surface of the pin joint and that prevents relative rotation between the box joint and the pin joint around the axis; A method for manufacturing a steel pipe connecting device comprising: a bolt that is inserted through a countersunk bolt mounting hole provided in either the box joint side region or the pin joint side region of the rotation restraint key and threadedly engages with the box joint or the pin joint, and fixes the rotation restraint key in the fitting recess, On the outer surface of the rotation prevention key, a first imaginary line overlapping a boundary line between the box joint and the pin joint in the fitting recess; a second imaginary line connecting one end of the first imaginary line and the center of the counterbore; A third imaginary line is assumed to connect the other end of the first imaginary line and the center of the counterbore; a distance from the one end of the first imaginary line to an intersection point between the second imaginary line and an edge of the counterbore is defined as b1; When the distance from the other end of the first imaginary line to the intersection point between the third imaginary line and the edge of the countersink is b2, Shear strength T of the rotation prevention key Ｓ Calculating using the following formula: [Equation 2] (where t is the thickness of the rotation restraint key, and σ １ is the yield stress of the rotation restraint key, and k is a predetermined correction factor. The shear strength T Ｓ b1, b2 and t are set so that b1, b2 and t are equal to or greater than a predetermined threshold value; and manufacturing the rotation restraining key, the box joint, and the pin joint based on the set b1, b2, and t.

3. the rotation prevention key is substantially rectangular and has a box joint side edge portion entirely located on the box joint side, a pin joint side edge portion entirely located on the pin joint side, and two bearing edge portions spanning the box joint and the pin joint, the rotation restraint key is arranged so that the box joint side edge portion and the pin joint side edge portion are parallel to the boundary line and the two bearing edge portions are parallel to the axis, A fourth imaginary line is assumed to be parallel to the axis on the outer surface of the rotation prevention key; The distance from the intersection of the fourth virtual line and the box joint side edge portion to the intersection of the fourth virtual line and the first virtual line is L1, When the distance from the intersection of the fourth imaginary line and the pin joint side edge portion to the intersection of the fourth imaginary line and the first imaginary line is L2, The bearing strength T of the first bearing portion located on the box joint side of each of the bearing edge portions Ｂ１ Calculating using the following formula: [Equation 3] The bearing strength T of the second bearing portion located on the pin joint side of each of the bearing edge portions Ｂ２ Calculating using the following formula: [Equation 4] The bearing pressure resistance T Ｂ１ and the bearing strength T Ｂ２ L1, L2 and t are set so that is equal to or greater than a predetermined threshold value; The shear strength T Ｓ and the bearing strength T Ｂ１ and the bearing strength T Ｂ２ and adjusting at least one of L1 and L2 so that the value of L1 approaches the value of L2 corresponding to the bearing capacity of the area where the bolt mounting holes are not provided. The manufacturing method according to claim 2 , further taking into consideration at least one of the adjusted L1 and L2 when manufacturing the rotation restraint key, the box joint, and the pin joint.

4. 4. The manufacturing method according to claim 3, wherein in the adjustment, both L1 and L2 are adjusted so that the sum of L1 and L2 is constant.

5. The manufacturing method according to claim 3 , wherein only one of L1 and L2 is adjusted in the adjustment.

6. The manufacturing method according to claim 2 , wherein the bolt mounting hole is provided in a region of the rotation preventing key on a side of the pin joint.

7. The manufacturing method according to any one of claims 2 to 5, wherein the bolt mounting holes are provided at positions where b1 = b2.

8. A box joint and a pin joint that can be connected to each other so as to have the same axis; a rotation prevention key that is attached to a fitting recess provided across both the outer peripheral surface of the box joint and the outer peripheral surface of the pin joint and that prevents relative rotation between the box joint and the pin joint around the axis; A steel pipe connecting device comprising: a bolt that is inserted through a countersunk bolt mounting hole provided in either the box joint side region or the pin joint side region of the rotation restraint key and threadedly engages with the box joint or the pin joint, and fixes the rotation restraint key in the fitting recess, the rotation prevention key is substantially rectangular and has a box joint side edge portion entirely located on the box joint side, a pin joint side edge portion entirely located on the pin joint side, and two bearing edge portions spanning the box joint and the pin joint, the rotation prevention key is arranged so that the box joint side edge portion and the pin joint side edge portion are parallel to the boundary line between the box joint and the pin joint in the fitting recess, and so that the two bearing edge portions are parallel to the axis, On the outer surface of the rotation prevention key, a first imaginary line that overlaps the boundary line; a second imaginary line connecting one end of the first imaginary line and the center of the counterbore; a third imaginary line connecting the other end of the first imaginary line and the center of the counterbore; a fourth imaginary line parallel to the axis; a distance from the one end of the first imaginary line to an intersection point between the second imaginary line and an edge of the counterbore is defined as b1; a distance from the other end of the first imaginary line to an intersection point between the third imaginary line and an edge of the countersink is defined as b2; The distance from the intersection of the fourth virtual line and the box joint side edge portion to the intersection of the fourth virtual line and the first virtual line is L1, When the distance from the intersection of the fourth imaginary line and the pin joint side edge portion to the intersection of the fourth imaginary line and the first imaginary line is L2, Shear strength T of the rotation prevention key Ｓ is expressed by the following formula: [Equation 5] The bearing strength T of the first bearing portion located on the box joint side of each of the bearing edge portions Ｂ１ is expressed by the following formula: [Equation 6] The bearing strength T of the second bearing portion located on the pin joint side of each of the bearing edge portions is Ｂ２ is expressed by the following formula: [Equation 7] where t is the thickness of the rotation prevention key, and σ １ is the yield stress of the rotation restraint key, k is a predetermined correction factor, The shear strength T Ｓ , the bearing pressure resistance T Ｂ１ and the bearing strength T Ｂ２ is equal to or greater than a predetermined threshold, and The shear strength T Ｓ and the bearing strength T Ｂ１ and the bearing strength T Ｂ２ A steel pipe connecting device in which L1, L2, b1, b2 and t are set so that the bearing capacity of the area where the bolt mounting holes are not provided is substantially equal to the bearing capacity of the area where the bolt mounting holes are not provided.

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