JPH09304354A - Method for detecting disconnection of cable element wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect disconnection of the element wires of a parallel-wire cable that is a hanging member of a bridge, such as a cable stayed bridge or a suspension bridge, or of a construction. SOLUTION: Part of a cover 5 at a position that is 5m or so away from the end 3 of cable is peeled, an ultrasonic probe 7 is contacted with the side of an element wire 2 for examination, and ultrasonic pulses of a predetermined frequency are input to the element wire 2 by an ultrasonic flaw detector 8. The input ultrasonic pulses propagate within the element wire 2 toward a socket 3 and, if the element wire 2 is ruptured, are reflected at the rupturing point; if the element wire 2 is not ruptured, they are reflected at an element wire terminal point 3 inside the socket. The reflected pulses are detected by the ultrasonic probe 7 and converted into voltage signals by the ultrasonic flaw detector 8, and a display device 9 is used to determine whether or not there is a rupture and displays the rupturing position. If there are no reflected waves, the element wire 2 is judged to be ruptured diagonally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a break in a wire of a cable used as a suspension material for bridges such as cable-stayed bridges and suspension bridges, and construction materials.

[0002]

2. Description of the Related Art As a tension member used for suspension materials for bridges such as cable-stayed bridges and suspension bridges, and construction materials, there is a parallel cable as shown in FIG. 1, for example. The parallel cable 1 is
It is a pulling member in which strands 2 made of steel wire having a diameter of about 5 to 7 mm are bundled, and the space between the strands 2 is cast into the socket portion 3 with a zinc alloy 4 or the like. The outer layer of the cable is covered with plastic 5 or the like so that rainwater does not directly hit the inner wire of the cable. However, during long-term use, it may be covered by external factors such as earthquakes and cars.
It is conceivable that the wire is damaged, cracks occur, rainwater penetrates into the cable, stress corrosion occurs on the wire 2, and it grows and finally breaks. Also, over the years,
It is conceivable that a part of the strands in the cable may be fatigue fractured because the cable is repeatedly subjected to excessive tension and bending due to repeated passage of a heavy vehicle and strong wind. These wire breakages rarely occur, and even if there is a breakage, it does not affect the entire structure because the safety factor is expected. It is important to detect non-destructively the presence or absence of wire breakage that occurs in.

Conventionally, as a method for detecting a wire rope breakage, a magnetic flaw detection method has been used in which a wire is magnetized to detect a leakage magnetic flux due to a defect. However, with cables having large wire diameters and bundle diameters used for long bridges and the like, it becomes difficult to detect defects due to magnetic flaw detection as these dimensions increase.

Therefore, the socket portion 3 is disclosed in JP-A-61-111460 and JP-A-63-47653.
A method of injecting an ultrasonic wave from the end face of the wire and detecting a reflected pulse from the breaking point of the wire is presented. However, in order to carry out this method, it is necessary for an inspector to enter the cable fixing part and bring the ultrasonic probe into contact with the end face of the wire exposed on the rear surface of the socket. However, it is difficult to enter the fixing section. Furthermore, since the end face of the wire is a face cut by a wire cutter, the cut end is not flat, and processing for producing flatness is required in advance for flaw detection. Also, in some cases, since the alloy is cast up to the end face of the strand, it is necessary to process to expose the end face, and considering these working spaces, the measurement method in which ultrasonic waves are incident from the end face of the strand is applied. The bridges that can be made are quite limited.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and an object thereof is to make a cable by injecting an ultrasonic wave into a wire and detecting a reflected pulse from a breaking point. A method for detecting wire breaks is to provide a method in which the inspection work is not restricted in space. Further, as a completely different method from the conventional method, it is possible to check the existence of the reflection pulse and the arrival time of the reflection pulse. It is to provide a method of detecting a disconnection.

The cables referred to in the present invention include parallel wire cables in which element wires are bundled, as well as those with some twist.

[0007]

In order to solve the above-mentioned problems, a method for detecting a break in a cable wire according to the present invention is designed so that a part of the coating of the cable is peeled off to expose the wire and the cable is exposed from the side surface of the wire. A feature of the present invention is that a wire break is detected by injecting an ultrasonic wave into an end portion and detecting a reflected pulse from a wire break point or a wire end point.

In one embodiment of the present invention, a part of the cable coating is peeled off at a position where a reflected wave from the cable end can be detected, for example, at a position about 5 m away, for example, near the bridge surface, to expose the bare wires. A wire breakage is detected by injecting ultrasonic waves from the side surface of the wire and propagating the ultrasonic wave in the socket direction of the cable fixing portion to detect a reflection pulse from the wire break point or the wire end point. In this aspect, if the reflected wave is detected before the timing of receiving the reflected wave from the cable end, it is the reflected wave from the wire breaking point, and thus the wire breaking point can be known. When only the reflected wave from the end of the cable is detected, it can be seen that the strand does not break. When the reflected wave from the end of the cable is not detected, it can be determined that the strand has an oblique break. In this embodiment, the object that can be inspected is the wire around the outer circumference of the cable, and the range is limited to about 10 m from the end of the cable due to the attenuation of ultrasonic waves. Since fatigue rupture due to load can be expected to occur in the cable outer peripheral wire near the socket,
It is important to detect the wire breakage at the outer circumference of the cable at an early stage.

It should be noted that, when carrying out the present invention, it is necessary to peel off the coating 5 of the cable by a length of several cm, but a technique for re-coating is currently established, and peeling the coating 5 does not affect the cable. .

[0010]

The present invention will be described in detail with reference to the drawings. FIG. 2 is an explanatory view showing an embodiment of the present invention, in which both sides of the cable 1 to be inspected are fixed to the cable fixing portion 6 by the sockets 3 on the bridge surface and on the tower (only one side is shown). An ultrasonic probe 7 is brought into contact with the side surface of the strand 2 to be inspected by peeling off a part of the coating 5 in the middle of the cable, and an ultrasonic pulse of a predetermined frequency is applied to the strand by an ultrasonic flaw detector 8. The injected ultrasonic pulse travels through the wire toward the socket, and if the wire is broken, it is reflected at the break point, but the reflected pulse is scattered and returns depending on the shape of the broken surface. May not be. On the other hand, if the wire is not broken, it reflects at the end point of the wire in the socket. These reflected pulses are detected by the ultrasonic probe 7, converted into a voltage signal by the ultrasonic flaw detector 8, and the presence or absence of breakage and the breakage position are determined and displayed by the display device 9.

[0011]

[Example] For a parallel bridge cable at the level of a real bridge provided with various simulated wire breaks, the wire breaks were experimentally inspected by the apparatus configuration of FIG. The coating of the cable was peeled off with a width of 5 cm at a position of 5 m from the outlet on the bridge side socket, and the ultrasonic probe 7 shown in FIG.
The ultrasonic probe 7 used is a 5 MHz longitudinal wave bevel probe, and is composed of a piezoelectric element 7A and a contact shoe 7B. The tip shape of the contact shoe 7B determines the efficiency of ultrasonic wave incidence on the wire. In order to improve it, the curved surface is made to match the diameter of the wire.
Further, the incident angle θ on the wire is designed under the condition that the ultrasonic wave propagates best in the wire. FIG. 4 is a representative example of the inspection result, (a) shows the time interval T between the incident pulse P and the reflected pulse R.
An example in which it is estimated that there is a break at a distance of 2.5 m from the incident point of the ultrasonic wave from 1; (b) is a time interval T2; a pulse R is a reflection pulse from the end point of the wire in the socket This is an example estimated to be absent. On the other hand, (c) is an example in which no reflected pulse was detected at all, and it was presumed that the reflected pulse was not scattered and returned because the fracture surface of the wire was oblique.

After the experiment was completed, the parallel cable was stripped over its entire length and inspected in detail. As a result, the strand whose inspection result was as shown in FIG. It was confirmed that the wire was broken at the position of, and that the strand shown in FIG. 4B was not broken. On the other hand, the strand shown in FIG. 4 (c) is obliquely disconnected at a position 2.1 m away from the ultrasonic wave incident point, and since the cut surface is oblique, the ultrasonic wave is scattered and the breaking point. It was confirmed that the reflected pulse from could not be detected.

[0013]

As described above, according to the present invention, during the actual operation of the parallel cable, the coating in the middle of the cable is partly peeled off and the ultrasonic pulse is injected from the side surface of the wire, from the break point and the termination point. The broken strands in the parallel cable can be reliably detected by detecting the reflected pulse of. The present invention is applicable to all cables in operation because it does not require a particularly wide inspection space, and the wire breakage of the outer peripheral wire that is likely to cause wire breakage is not affected by the shape of the breakage part Since it can be inspected, it is an extremely effective method in terms of maintenance management of the structure.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a parallel wire cable.

FIG. 2 is a block diagram showing an embodiment of the present invention.

3A is an enlarged side view showing an enlarged view around the ultrasonic probe 7 shown in FIG. 2, and FIG. 3B is a cross-sectional view of the wire 2 shown in FIG. 3A.

FIG. 4 shows observed voltages of emitted and received pulses of the ultrasonic probe 7 in the embodiment shown in FIGS. 2 and 3, and (a) shows an example in which ultrasonic reflected pulses from a break point are detected. , (B)
Is an example in which the reflected pulse from the wire end point is detected,
(C) shows an example in which no reflected pulse was detected.

[Explanation of symbols]

1: Parallel wire cable 2: Element wire 3: Socket part 4: Zinc alloy 5: Coating 6: Cable fixing part 7: Ultrasonic probe 7A: Piezoelectric element 7B: Contact shoe 8: Ultrasonic flaw detector 9: Display device

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroyuki Okada Inventor Hiroyuki Okada 2-6-3 Otemachi, Chiyoda-ku, Tokyo Within Nippon Steel Corp. (72) Inventor, Tsuguo Ishida 5-chome Fuchinobe, Sagamihara City, Kanagawa Prefecture 10-1 Incorporated Nippon Steel Techno-Research (72) Inventor Ken Udagawa 5-10 Fuchinobe, Sagamihara City, Kanagawa 10-1 Incorporated Nippon Steel Techno-Research

Claims (2)

[Claims] 1. An ultrasonic wave is incident from the side surface of a bare wire exposed by peeling off a part of the cable coating to detect breakage of the wire from a detection signal of a reflected pulse. Method for detecting disconnection of cable wires. 2. A wire breakage is detected from the presence or absence of a reflected pulse and the arrival time of the reflected pulse by injecting an ultrasonic wave toward the end of the cable from the side surface of the bare wire that is exposed by partially removing the coating of the cable. A method for detecting disconnection of a cable wire, which is characterized in that