Tension measurement method, tension measurement system, and tension reduction method

Abstract

Disclosed herein is a tension measurement method wherein: the actual length of a cable attached to two support bodies is calculated from a load measured at a center point of the cable and the unit weight of the cable; the degree of slack of the cable is calculated from the calculated actual length and the span length of the two support bodies; and the tension of the cable on the support bodies with respect to the amount of extension when the center point of the cable is pushed up from the lowest point at the center point is calculated from relationships between the calculated actual length of the cable, the unit weight, the span length, the calculated degree of slack, the amount of extension, and the tension of the cable on the support bodies.

Description

Tension measurement method, tension measurement system, and tension reduction method 【0001】 The present disclosure relates to a method for measuring the tension of a cable mounted on two supports, a tension measurement system, and a tension reduction method. 【0002】 In order to reduce the tension exerted by a cable mounted on two supports such as utility poles on the supports, between the two supports, the cable is pushed upward from below by a support bar. On the other hand, as a method for measuring the tension of a cable, there is a method of measuring the tension by vibration (see, for example, Patent Document 1). This measures the tension of the cable by applying a high-frequency signal to the end of the cable, measuring and demodulating the high-frequency signal at the opposite end, and analyzing the attenuation of the high-frequency signal. 【0003】 JP 2002-090241 【0004】 However, in this method, it is necessary to install a high-frequency signal generator at the end of the cable and a high-frequency signal measuring device at the opposite end. For this reason, the measurement system becomes complicated. Furthermore, when a point in the middle of the cable mounted on two supports is pushed upward, the high-frequency signal is attenuated in the middle, making it difficult to measure the tension of the cable. 【0005】 Therefore, an object is to provide a tension measurement method and a tension measurement system that calculate the tension of a cable with respect to the amount of elongation when the central point of the cable mounted on two supports is pushed upward with a simple configuration. Another object is to provide a method for reducing the tension of a cable using the above tension measurement method or tension measurement system. 【0006】 To achieve the above object, in the tension measurement method and the tension measurement system according to the present disclosure, the load is measured at the central point of the cable mounted on two supports, and the tension of the cable with respect to the amount of elongation when the central point of the cable is pushed upward is calculated. 【0007】Specifically, this disclosure is a tension measurement method that calculates the actual length of a cable from the load measured at the midpoint of a cable attached to two supports and the unit weight of the cable, calculates the sag of the cable from the calculated actual length and the span length of the two supports, and calculates the tension relative to the elongation amount from the relationship between the calculated actual length of the cable, the unit weight, the span length, the calculated sag, the amount of elongation when the midpoint of the cable is pushed upward from the lowest point at the midpoint, and the tension of the cable at the supports. 【0008】 Specifically, the present disclosure provides a tension measuring system comprising: a tension measuring device having a contact portion that allows an attached cable to be easily moved in the longitudinal direction of the cable; a load measuring portion for measuring the load on the cable; and an elongation measuring portion for measuring the amount of elongation that pushes up the contact portion; and a tension calculating device for calculating the tension with respect to the aforementioned amount of elongation. 【0009】 To achieve the above objective, the cable tension reduction method described herein utilizes the above-described tension measurement method or tension measurement system to reduce the tension of a cable attached to two supports. 【0010】 Specifically, this disclosure is a tension reduction method that pushes up the central point of the cable between two elongation amounts where the tension calculated above reaches a predetermined value. 【0011】 Specifically, the present disclosure is a tension reduction method that pushes up the center point of the cable until the amount of elongation becomes equal to the sag calculated above. 【0012】 Furthermore, the above disclosures can be combined as much as possible. 【0013】 This disclosure provides a tension measurement method and tension measurement system for calculating the tension of a cable with a simple configuration, based on the amount of elongation when the midpoint of a cable attached to two supports is pushed upward. Furthermore, a method for reducing the tension of a cable attached to two supports can be provided using the above tension measurement method or tension measurement system. 【0014】This is a cable attached to two supports. This is an example illustrating how to use the tension measuring device of this disclosure. This is an example of the configuration of the tension measuring device of this disclosure. This is an example illustrating how to find the center point of the cable of this disclosure. This is an example of how to calculate tension of this disclosure. This is an example illustrating how to use the tension measuring device of this disclosure. This is an example illustrating how to use the tension measuring device of this disclosure. This is an example of tension calculated by the tension calculation method of this disclosure. This is an example of how to reduce tension of this disclosure. This is an example of tension reduced by the tension reduction method of this disclosure. 【0015】 Embodiments of this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments shown below. These examples are illustrative, and this disclosure can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. In this specification and in the drawings, components with the same reference numerals refer to the same components. 【0016】 Figure 1 shows the state of cable laying work. In Figure 1, 21 is a support structure to which the cable is attached, and 22 is the cable to be laid. When laying a cable, two support structures 21 are used, for example, to stretch the cable 22 between utility poles, and then the cable 22 is fixed to the support structures 21. At this time, the support structures 21 are subjected to a large tension due to the weight of the cable 22. 【0017】 A method for finding the center point of an attached cable will be explained. The method for finding the center point of an attached cable is shown in Figures 2 and 4, and the configuration of the tension measuring device used in the method is shown in Figure 3. In Figure 3, the tension measuring device 10 has a contact part 11 that allows the attached cable 22 to move easily in the longitudinal direction of the cable 22, a load measuring part 12 that measures the load Wg of the cable 22, and an elongation amount measuring part 13 that measures the elongation amount Dh that pushes up the contact part 11. 【0018】If the contact portion 11 has, for example, a pulley, as shown in Figure 2, when the cable 22 is pushed up, the cable 22 will move more easily in the longitudinal direction of the cable. Instead of a pulley, the contact portion 11 may have a groove that has been processed to reduce sliding friction. The load measuring portion 12 has, for example, a pressure sensor and can measure the load Wg applied to the cable 22 downwards (in the direction of weight). The elongation measuring portion 13 measures the elongation Dh when the contact portion 11 is pushed up from the rod 14. 【0019】 Figure 4 illustrates the method for finding the center point of the attached cable. The center point is the center of gravity where the tension of the cable 22 is balanced. As shown in Figure 2, the tension measuring device 10 pushes up the cable 22 (S31). It is determined whether the cable 22 at the contact point 11 moves in the longitudinal direction of the cable 22 (S32). If it moves ("Y" in S32), the position of the tension measuring device 10 is changed (S33), and the tension measuring device 10 pushes up the cable 22 (S31). It is determined whether the cable 22 at the contact point 11 moves in the longitudinal direction of the cable 22 (S32). If the cable 22 does not move ("N" in S32), that position is determined to be the center point of the cable (S34). If the tension of the cable 22 is balanced on both sides of the tension measuring device 10, the cable 22 at the contact point 11 will no longer move in the longitudinal direction of the cable 22. 【0020】 According to this embodiment, the center point of a cable can be determined even if the span length S of the two supports or the center of gravity of the cable is unknown. Furthermore, the center point of a cable can be determined even when it is difficult to measure the actual distance at a construction site. 【0021】 If the center point of the cable 22 is already known, it is desirable that the contact portion 11 of the tension measuring device 10 also has the function of fixing the cable 22. 【0022】A method for measuring the tension of an attached cable and a tension measurement system will be explained using Figures 3, 5, 6, and 7. As shown in Figure 5, in the tension measurement method of this embodiment, the actual length L of the cable 22 is calculated from the load Wg measured at the center point of the cable 22 attached to two support bodies 21 and the unit weight Wu of the cable 22. The sag Dd of the cable 22 is calculated from the calculated actual length L and the span length S of the two support bodies 21. The tension Tn relative to the elongation Dh is calculated from the relationship between the calculated actual length L of the cable 22, the unit weight Wu of the cable 22, the span length S of the cable 22, the calculated sag Dd of the cable 22, the elongation Dh when the center point of the cable 22 is pushed upward from the lowest point at the center point, and the tension Tn of the cable 22 at the support body 21. 【0023】 As shown in Figures 3, 6, and 7, the tension measuring system of this embodiment comprises a tension measuring device 10 having a contact portion 11 that is easily movable in the longitudinal direction of the attached cable 22, a load measuring portion 12 for measuring the load Wg of the cable 22, and an elongation amount measuring portion 13 for measuring the elongation amount Dh when the contact portion 11 is pushed up, and a tension calculation device (not shown) for calculating the tension Tn for the above elongation amount Dh. 【0024】 As shown in Figure 6, the load Wg of the cable 22 is measured at the midpoint of the cable 22 attached to the two supports using the tension measuring device 10 (S41). The actual length L of the cable 22 is calculated from the measured load Wg (N) and the unit weight Wu (N / m) of the cable 22 already obtained, according to equation (1) (S42). N is a Newton and m is a meter. L = Wg / Wu (1) 【0025】 As shown in Figure 6, the sag Dd (m) of the cable 22 is calculated according to equation (2) using the actual length L calculated by equation (1) and the span lengths S (m) of the two support bodies 21 that have already been obtained (S43). ２ = 3S(L-S) / 8 (2) The sag Dd is the difference between the height of the fixing point of the cable 22 to the support 21 and the height of the lowest point of the cable 22. 【0026】Next, as shown in Figure 7, if the tension measuring device 10 pushes the cable 22 upward from its lowest point at the center point, the amount of elongation is Dh (m), and the tension of the cable 22 in the support 21 is Tn (N), then the following relationship holds: L / 2 = C(sinh(M / C) + sinh((S-M) / C)) where, C = Tn / Wu M = (S / 2) / 2 - Csinh －１ ((Dd-Dh) / (2Csinh(S / 2C)) (3) 【0027】 In equation (1), if the measured load Wg and the obtained unit weight Wu are as follows: Wg = 480.128 (N) and Wu = 16 (N / m), then L = 30.008 (m). In equation (2), when the obtained span length S is S = 30 (m), then Dd = 0.3 (m). 【0028】 The tension Tn is calculated for the elongation Dh from the relationship between the actual cable length L, unit weight Wu, span length S, sag Dd, elongation Dh, and tension Tn shown in equations (1) to (3) (S44). The obtained result is shown in Figure 8. Steps S42 to S44 shown in Figure 5 may be performed by the tension calculation device. Alternatively, the tension calculation device may automatically acquire the load Wg measured by the tension measuring device in S41 of Figure 5. 【0029】 If the relationship between tension Tn and elongation Dh, as shown in Figure 8, can be obtained, the tension Tn for any given elongation Dh can be calculated, and conversely, the elongation Dh required for any given tension Tn can also be calculated. 【0030】 As shown in Figure 6, if the tension of the cable 22 before its center point is pushed upward is the initial tension Ti, then from Figure 8, we obtain Ti = 6000 (N). As the elongation amount Dh increases, the tension Tn decreases, and it can be seen that when Dh = Dd = 0.3 (m), the tension Tn is at its minimum, which is half of the initial tension Ti. At this time, Tn = Ti / 2 = 3000 (N). 【0031】Therefore, according to this embodiment, a tension measurement method and tension measurement system can be provided that calculate the tension of a cable with respect to the amount of elongation when the central point of a cable attached to two supports is pushed upward, with a simple configuration. 【0032】 Using the relationship between elongation amount Dh and tension Tn obtained in the previous embodiment, a tension reduction method for reducing the tension of a cable attached to two supports will be explained with reference to Figures 9 and 10. If it is unclear to what extent the tension Tn of the cable can be reduced by pushing the cable upward at its center point, first determine the target tension (S51). From the relationship between elongation amount Dh and tension Tn obtained in the previous embodiment, determine whether the target tension Tn is achievable (S52). For example, in Figure 8, it is 3000 N or more and 6000 N or less. Set the target value as a predetermined value, and if possible ("Y" in S52), calculate the elongation amount Dh at which the tension Tn becomes the predetermined value. If not possible ("N" in S52), consider other methods such as pushing the cable up at two or more locations in addition to the center point (S54). Steps S52 to S53 in Figure 9 may be performed by a tension calculation device. 【0033】 Figure 10 shows the relationship between tension Tn and elongation amount Dh obtained in this embodiment. For example, in Figure 10, the initial tension Ti at Dh = 0 is 6000 (N). From the previous embodiment, it has been shown that this can be reduced to tension Tn = Ti / 2 = 3000 (N). When carrying out cable work, if the target tension Tn is between 3000 N and 6000 N, it is feasible and the tension reduction method of this embodiment is effective. Therefore, for example, the elongation amount Dh that results in tension Tn = 4000 (N) (Dh corresponding to points A and A' in Figure 10) is determined. As a result, the cable is pushed up from the center point of the attached cable to any position between Dh corresponding to point A in Figure 10 and Dh corresponding to point A' in Figure 10 (any position in the section indicated by the double arrows in Figure 10). In the example in Figure 10, this is a position between Dh = 0.08 m and 0.52 m. 【0034】Therefore, by pushing up the center point of the cable between two elongation amounts Dh where the tension Tn reaches a predetermined value, cable installation can be carried out with a tension Tn within the set range. 【0035】 From the previous embodiment, it was found that the tension can be reduced to the minimum when the cable is pushed up until the elongation Dh is equal to the sag Dd, resulting in a tension Tn = Ti / 2 = 3000 (N). Therefore, by pushing up the center point of the cable until the elongation Dh is equal to the sag Dd, the load on the support structure can be reduced to the minimum during cable installation, making the cable installation safe and easy. 【0036】 According to this embodiment, the tension on the cables attached to the two supports can be reduced. 【0037】 As described above, this disclosure provides a tension measurement method and a tension measurement system for calculating the tension of a cable with respect to the amount of elongation when the central point of a cable attached to two supports is pushed upward, using a simple configuration. Furthermore, a method for reducing the tension of a cable attached to two supports can be provided using the above tension measurement method or tension measurement system. 【0038】 The tension calculation device included in the tension measurement system of the present invention can also be implemented using a computer and a program, and the program can be recorded on a recording medium or provided via a network. 【0039】 The tension measurement method, tension measurement system, and tension reduction method disclosed herein can be applied to the information and communication industry. 【0040】 10: Tension measuring device 11: Contact part 12: Load measuring part 13: Elongation measuring part 14: Rod 21: Support 22: Cable S: Span length Dd: Sag Dh: Elongation Tn: Tension Ti: Initial tension

Claims

1. A tension measurement method comprising: calculating the actual length of a cable from the load measured at the midpoint of a cable attached to two supports and the unit weight of the cable; calculating the sag of the cable from the calculated actual length and the span length of the two supports; and calculating the tension relative to the elongation amount from the relationship between the calculated actual length of the cable, the unit weight, the span length, the calculated sag, the amount of elongation when the midpoint of the cable is pushed upward from its lowest point, and the tension of the cable on the supports.

2. A tension reduction method that pushes up the central point of the cable between two elongation amounts where the tension calculated in claim 1 reaches a predetermined value.

3. A tension reduction method for pushing up the central point of the cable until the amount of elongation equals the sag calculated in claim 1.

4. A tension measuring system comprising: a tension measuring device having a contact portion that allows the attached cable to move easily in the longitudinal direction of the cable, a load measuring portion for measuring the load on the cable, and an elongation measuring portion for measuring the amount of elongation that pushes up the contact portion; and a tension calculating device for calculating the tension with respect to the elongation amount described in claim 1.

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