JPH07311104A - Cable tensile force measuring method with gauge wire - Google Patents

Abstract

PURPOSE:To provide a method which enables easy measurement of the tensile force of a cable, of a structure using a cable as a structural member in part or for all of structure body. CONSTITUTION:Single or multiple gauge wires are attached along the total length or a part of a cable. In an unstressed state where tensile force does not act, middle points B and C, corresponding to the end points a and b of the gauge wire, are provided on the cable. The end point b of the gauge wire is fixed to the middle point c of the cable, and the portion between a and b and the end point a of the gauge wire are allowed to move independently of the cable, then, the distance Z between the end point a of the gauge wire and the middle point B of the cable is measured when tensile force acts. The distance Z between the end point a of the gauge wire and the middle point B of the cable, in a stressed state, is measured, and cable distortion s is obtained from Z, and further, the tensile force T acting upon the cable is obtained from s.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the tension of a cable of a structure which uses the cable as a structural member for a part or all of the structure.

[0002]

2. Description of the Related Art The following method has been put into practical use as a method for measuring cable tension. 1) A method of directly measuring the cable tension with a load cell or the like. 2) A method of determining the cable tension by measuring the natural frequency of the cable. 3) A method in which a strain gauge is attached to the cable strand and the tension is determined by strain of the strand. 4) A method of obtaining the cable tension by measuring the distance between the fixing points of the cable and the cable sag. However, the conventional method has the following problems. 5) In the method of 1), the load cell is expensive and the equipment cost is high. 6) In the method of 2), when there is a fixed point (including an elastic fixed point) in the middle of the cable, it becomes difficult to measure the natural frequency. 7) According to the method of 3), it is difficult to attach the strain gauge when the cable is covered (on anticorrosion). 8) In the method of 3), an optical distance meter is used to measure the distance between fixing points and the cable sag, but it may not be possible depending on the installation location of the cable.

[0003]

SUMMARY OF THE INVENTION In order to solve the above problems, it is an object of the present invention to provide a cable tension measuring method which is simple in measuring method, has few restrictions on measurement, and does not require measurement cost. And

[0004]

Means for solving the problems of the present invention will be described with reference to FIG. In the present invention,
A gauge wire whose cross-sectional area is very small compared to the cross-sectional area of the cable is placed along the cable for measuring tension, and tension does not act, and the length of the gauge wire is used as a reference for the cable under tension. The amount of change in length (difference between the length of the cable in the state where no tension is applied and the length of the cable in the state where tension is applied) is obtained, and the tension of the cable is measured. The principle of the cable tension measuring method using the gauge wire of the present invention will be described below.
For balanced cables, according to Hooke's law,
The relationship between cable tension and cable strain is T = E × F ×
denoted by s. Here, T is the tension of the cable, F is the cross-sectional area of the cable, E is the elastic modulus of the cable, and s is the strain of the cable. If the amount of change in the cable length is Q and the cable length in the stress-free state is L, s =
It is represented by Q / L. If the cable length when the cable tension T is acting is set as R, the change amount of the cable length is Q.
= RL can be obtained. Therefore, the cable tension T
If the cable strain or the amount of change in the cable length can be measured, the cross-sectional area A and the elastic modulus E are constant for each cable, and therefore T = E × F × s. The present invention is based on the length of the gauge wire,
The present invention relates to a method of directly measuring the change amount Q of the cable length, obtaining the cable strain s from Q, and obtaining the cable tension from s.

[0005]

The concrete method of measuring the cable tension using the gauge wire of the present invention will be described with reference to FIGS. 2 and 3.
FIG. 2 shows the relationship between the cable and the gauge wire when no stress is generated in the cable and when there is no stress. Let G be the length of the gauge wire when there is no stress and L be the length of the cable that has no stress, and let the gauge wire run along the middle of the cable. The fixing points of the cable are A and D, and the end points of the gauge wire are a and b, respectively. Intermediate points B and C corresponding to the end points a and b of the gauge wire are installed on the cable side. Here, the stress-free length between the intermediate points B and C of the cable is G. Next, when the movement of the end point b of the gauge wire and the intermediate point C of the cable is restrained, and it is considered that the frictional force does not act between the gauge wire and the cable, the tension of the cable and the gauge wire in the stress state acts on the gauge wire. The relationship can be shown in "Figure 3". Here, R is the length of the cable when the tension T is acting, and H is the length of the cable between the intermediate points B and C of the cable when the tension T is acting. If the amount of change in the length of the cable between the intermediate points B and C of the cable is set as Z, Z does not act on the gauge wire, and Z satisfies Z = HG. If the strain of the cable between the intermediate points B to C of the cable is set as g, the strain of the cable is expressed by g = Z / G. Here, since the strain s of the entire cable is considered to be constant over the entire length of the cable, s = g can be set. Therefore, the cable tension T can be obtained from T = E × F × s, where s = g. Since Z can be measured as the length between the cable intermediate point B and the gauge wire end point a, it is not necessary to measure the length H between the intermediate points of the cable.

[0006]

[Example] Omission

[0007]

【The invention's effect】

1) The method of the present invention can obtain the tension T of the cable by measuring the length Z of the end point a of the gauge wire and the intermediate point B of the cable in FIG. The Z measurement can be easily read with a scale tape or the like provided at the end point a of the gauge wire shown in FIG. 2) In the method of the present invention, it is not necessary to attach the gauge wire to the entire length of the cable, and the tension of the cable can be obtained by attaching the gauge wire to the middle part of the cable.
Therefore, the length of the gauge wire can be made shorter than the length of the cable, so that the installation cost of the measuring device can be reduced. 3) In the method of the present invention, the gauge wire is installed in the middle of the cable, but the mounting position can be set arbitrarily. Therefore, since the end point a of the gauge wire shown in FIG. 1 can be provided at a position where the cable can be easily measured, the measurement work can be easily performed.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a cable tension measuring device using a gauge wire of the present invention.

FIG. 2 is a diagram showing a relationship between a cable and a gauge wire in a stress-free state in which no tension is generated in the cable.

FIG. 3 is a diagram showing a relationship between a cable and a gauge wire in a stress state where tension is generated in the cable.

[Explanation of symbols]

A: Cable fixing point B: Cable middle point C: Cable middle point D: Cable fixing point a: Gauge wire end point b: Gauge wire end point T: Tension acting on cable L: In stress-free state Length between anchor points AD of cable G: Length between intermediate points BC of cable in non-stress state and length of gauge wire R: Length between anchor points AD of cable in stress state H: In stress state Between the intermediate points BC of the cable of Z: Elongation between the intermediate points BC of the cable under stress: Cable: Gauge wire: Scale

Claims (1)

[Claims] 1. A single or a plurality of gauge wires is attached along the entire length or a part of the cable, the amount of change in the cable length is measured with reference to the length of the gauge wire, and the cable tension is determined. A method for measuring the tension of a cable characterized by.