JP2007297777A - Cable for suspension structure and measurement system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure the temperature distribution, tension, and moisture content of a cable used for a suspension structure such as a cable-stayed bridge by a simple structure. <P>SOLUTION: This suspension structure such as a cable-stayed bridge comprises cables 5 for suspension structure for supporting a bridge girder 3 and an optical fiber sensor 40 having an optical fiber-incorporated line 25 in which an optical fiber 25a is incorporated. The optical fiber-incorporated line 25 of the optical fiber sensors 40 is installed in each cable 5 along the longitudinal direction of the cable body 21 of the cable. The temperature, deformation, or humidity is detected by these optical fiber sensors 40. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cable for a suspension structure used for a suspension structure such as a bridge and a roof of a building, and a measurement system.

  For example, as a bridge built on a river, a strait, a road or the like, a cable using a cable for a suspension structure such as a cable-stayed bridge or a suspension bridge is known. When constructing a bridge having such a suspended structure or during maintenance after construction, it is necessary to appropriately manage the shape, length, tension, etc. of the cable. Conventionally, as a method of measuring the cable shape change, length, tension, etc., the surface temperature at multiple locations in the length direction of the cable is measured, and the temperature distribution inside the cable is estimated from the measured surface temperature. A method of indirectly measuring the shape change, length, tension, etc. of the cable has been proposed (see Patent Documents 1 and 2). Various tension measurement methods such as a load cell method, a strain gauge measurement method, and a vibration method measurement method have been proposed (see Patent Documents 3 and 4). In bridge maintenance management, a method for managing the humidity in the cable has been proposed in order to prevent the cable from being corroded by moisture (see Patent Document 5).

JP-A-5-98609 JP-A-5-164630 JP 2000-155059 A JP 2001-255222 A Japanese Patent Laid-Open No. 10-159019

  However, in the conventional cable temperature measurement method, only the surface temperature of the cable can be measured, and the temperature inside the cable cannot be directly measured. In addition, it was difficult to measure the continuous temperature distribution over the entire length of the cable. In order to improve the measurement accuracy of the temperature distribution, the number of temperature sensor installation points, that is, the number of measurement points, should be increased. If the temperature is to be measured over the entire length of the cable, the total length of the cable However, in this case, since a great number of sensors are necessary, there is a problem that the wiring of the sensors becomes complicated. Furthermore, there was a problem that the weather resistance of the sensor was bad. In other tension measurement methods and humidity measurement methods, it was difficult to perform measurement with high accuracy and efficiency.

  The present invention has been made in view of the above points, and provides a cable for a suspension structure and a measurement system that can accurately measure the temperature distribution, tension, humidity, and the like of the cable with a simple structure. Objective.

  In order to solve the above problems, according to the present invention, there is provided a cable for a suspension structure including a cable body that supports a structural member, wherein an optical fiber is provided along a length direction of the cable body. A cable for a suspended structure is provided.

  The cable body may include a plurality of wires and the optical fiber. Moreover, the parallel wire strand may be comprised with the said some wire.

  One or more optical fibers may be provided inside the cable body. The optical fiber may be provided along at least a central portion of the cable body. The cable for the suspension structure may be used for a bridge.

  Furthermore, according to the present invention, the optical fiber provided in any one of the above suspension structure cables and a measuring device that detects predetermined information using light emitted from the optical fiber are provided. A characteristic measurement system is provided.

  The predetermined information may be a temperature distribution, a strain distribution, and / or a humidity distribution of the optical fiber. Moreover, you may provide the calculating part which calculates the shape and / or tension | tensile_strength of the said cable main body based on the said predetermined information.

  According to the present invention, it is possible to accurately and efficiently measure information such as temperature, tension, and humidity at a plurality of locations of a cable only by using at least one optical fiber. Continuous temperature distribution, strain distribution, humidity distribution, etc. inside the cable can be measured over the entire length of the cable. Simple structure and good durability. Since it is not necessary to replace the optical fiber sensor, the labor and cost required for maintenance can be reduced.

  Hereinafter, an embodiment according to the present invention will be described based on a cable used for a cable-stayed bridge as a bridge which is an example of a suspended structure. 1 and 2 show an example of a cable-stayed bridge. The cable-stayed bridge 1 illustrated in FIGS. 1 and 2 is formed between a pair of towers 2A and 2B that are erected at a predetermined interval between both banks of the river (in the width direction of the river). A bridge girder 3 as a structural member spanned between two and a plurality of cables 5 as cables for a suspension structure. Furthermore, a measurement system 6 for measuring the temperature, tension, and length of each cable 5 is provided.

  Each tower 2A, 2B is provided with two columns 10, 11, respectively. The column 10 is provided on the upstream side of the river (left side in FIG. 2), and the column 11 is provided on the downstream side of the river (right side in FIG. 2). The bridge girder 3 is provided so as to pass between the column 10 and the column 11 at the lower part of each tower 2A, 2B. A plurality of cables 5 are bridged diagonally between the columns 10 and 11 of the towers 2A and 2B and the bridge girder 3, respectively.

  For example, in the column 10 of the tower 2A, a plurality of cables 5, for example, the same number, are provided on both sides of the column 10 (both sides of the river). Above the bridge girder 3, one end (upper end, a socket 22 described later) of each cable 5 is attached to both sides of the column 10 side by side in the height direction of the column 10. Further, the cable 5 attached to the upper side is inclined more outward with respect to the support column 10, and the other end (lower end, socket 23 described later) is arranged at a position farther from the support column 10. It has become. The lower end of each cable 5 is attached in a line with respect to one edge of the bridge girder 3 (edge on the upstream side of the river). That is, the cable 5 having the upper end attached upward is attached so as to support the bridge girder 3 at a portion away from the support column 10. Thus, a plurality of cables 5 are arranged on the support column 10 so as to extend toward the both sides centering on the upper portion of the support column 10 and substantially symmetrical with respect to the support column 10. As shown in FIG. 3, each cable 5 has sockets 22, 23 to be described later attached to the side edge of the column 10 and one edge of the bridge girder 3, and the side edge of the column 10 and one edge of the bridge girder 3. The cable main body 21 to be described later is provided in a stretched state.

  Similarly, a plurality of cables 5 are attached to both sides of the column 11 of the tower 2A. The other end of each cable 5 is connected to the other edge of the bridge girder 3 (the edge on the downstream side of the river). It is attached. Further, the columns 5 and 11 of the tower 2B are provided with cables 5 similarly to the tower 2A, and the other ends of the cables 5 are respectively attached to both edges of the bridge girder 3.

  The bridge girder 3 is suspended by the cable body 21 of the plurality of cables 5 and supported in a state where it is lifted above the river. Each cable 5 is provided with a tension applied to the cable body 21 by applying a load of the bridge girder 3 to the cable body 21 described later.

  Next, an example of the structure of the cable 5 will be described in detail. As shown in FIG. 4, the cable 5 includes, for example, a cable main body 21, sockets 22 and 23 provided at both ends of the cable main body 21, and a plurality of light components that are constituent elements of an optical fiber temperature sensor 40 described later. A fiber built-in line (optical fiber cable) 25 is provided.

  As the cable body 21, for example, a parallel wire strand (PWS) is used. The cable body 21 includes an assembly (strand) 31 composed of a plurality of steel wires (wires) 30 and optical fiber built-in wires 25 as a plurality of wires, a coating layer 32 that covers the outside of the assembly 31, and a coating layer 32. A coating layer 33 that covers the outside is provided.

  The steel wire 30 is an elongated wire having a substantially circular cross-sectional shape having an outer diameter of about 7 mm, for example, and is, for example, a steel material whose outer peripheral surface is coated with zinc (Zn), that is, a galvanized steel wire. The steel wire 30 is disposed along the length direction of the cable body 21 from the socket 22 to the socket 23 inside the coating layers 32 and 33. Further, in the coating layers 32 and 33, for example, one or two or more optical fiber built-in wires 25 having an outer diameter almost equal to that of the steel wire 30 are provided from the socket 22 to the socket 23, and the length of the cable body 21. It is provided along the direction. Each optical fiber built-in line 25 includes an optical fiber (optical transmission line) 25a and an outer tube 25b that protects the optical fiber 25a. The plurality of steel wires 30 and the optical fiber built-in wire 25 are arranged substantially parallel to each other, and are bundled in a state where the outer peripheral surface of the adjacent steel wire 30 and the outer peripheral surface of the optical fiber built-in wire 25 are in close contact with each other. Yes.

  The plurality of steel wires 30 and the optical fiber built-in wire 25 are in a slightly twisted state. For example, as viewed from the socket 22 side, the central portion of the cable body 21 is moved toward the socket 23 side. It is twisted to the left as the center. That is, a single cord-like assembly 31 is formed by twisting and bundling the optical fiber built-in wires 25 in a mixed state in a plurality of steel wires 30. Therefore, the steel wire 30 and the optical fiber built-in wire 25 (excluding those provided in the central portion of the cable body 21) are wound slightly spirally around the central portion of the cable body 21, and the cable It is provided along the length direction of the main body 21. Therefore, the optical fiber built-in line 25 (optical fiber 25a) provided at the center of the cable body 21 is provided along the length direction at the center of the cable body 21, and the center of the cable body 21 is also provided. The optical fiber built-in line 25 (optical fiber 25a) arranged around the cable body 21 is provided along the length direction of the cable body 21 while being slightly spirally wound around the central portion of the cable body 21. It has been.

  As shown in FIG. 5, the optical fiber built-in line 25 is provided inside the covering layers 32 and 33, for example, along at least the central portion of the cable main body 21, and further around the central portion of the cable main body 21. Also, a plurality of them are arranged. For example, in the cross section of the cable main body 21, the cable main body 21 is arranged side by side on a concentric circle with the central portion of the cable main body 21 as the center. In the illustrated example, the steel wires 30 arranged on the outermost side are arranged on a concentric circle having a radius R at substantially equal intervals in the circumferential direction of the concentric circle, and further on a concentric circle having a radius R / 2. Moreover, they are arranged at almost equal intervals in the circumferential direction of the concentric circles. Further, as shown in FIG. 4, the end of each optical fiber built-in line 25 is led out from the end of the socket 23 and can be connected to a measuring device 42 to be described later.

  The covering layer 32 is provided so as to cover the entire outside of the aggregate 31. The covering layer 32 is constituted by a tape 32a such as a filament tape, for example. That is, the tape 32a is wound around the outer periphery of the assembly 31 along the length direction of the assembly 31, so that the steel wire 30 and the optical fiber built-in wire 25 are held in a bundled state, and the tape 32a A covering layer 32 made of is formed.

  The covering layer 33 is provided so as to cover the entire outside of the covering layer 32. As the material of the covering layer 33, a material having high weather resistance, for example, a synthetic resin such as polyethylene or fluororesin is used.

  Next, an example of the measurement system 6 will be described in detail. As shown in FIG. 3, the measurement system 6 includes an optical fiber temperature sensor 40 as a plurality of optical fiber sensors having the above-described optical fiber built-in line 25, and a control computer 41 that controls each of the optical fiber temperature sensors 40. It has.

  A plurality of optical fiber temperature sensors 40 are provided for each cable 5 (that is, the same number as the number of optical fiber built-in lines 25 provided for each cable 5). Each optical fiber temperature sensor 40 makes the light incident on one optical fiber built-in line 25 and the optical fiber 25a in the optical fiber built-in line 25, and detects the reflected light, whereby the temperature distribution over the entire length of the optical fiber 25a. And a measuring device 42 for obtaining As shown in FIG. 3, the measuring device 42 is attached to the end of each optical fiber built-in line 25 on the lower end side of the cable 5 provided in the cable-stayed bridge 1, for example.

  The measuring device 42 of each optical fiber temperature sensor 40 is electrically connected to the control computer 41, and a control signal related to temperature measurement is transmitted from the control computer 41 to each measuring device 42. It is configured as follows. In addition, information regarding the temperature distribution detected in each measuring device 42 is transmitted from each measuring device 42 to the control computer 41. Furthermore, the control computer 41 includes a calculation unit 41a that calculates the shape, length, tension, and the like of each cable body 21 based on the received information on the temperature distribution.

  Next, a method for measuring the temperature of the cable 5 in the cable-stayed bridge 1 configured as described above will be described. First, a control signal is transmitted from the control computer 41 to the measuring device 42 of any one of the optical fiber temperature sensors 40 provided on the cable 5 that is a temperature measurement target, and light is transmitted from the measuring device 42 to the optical fiber 25a. Make it incident. Then, the light is scattered in the optical fiber 25a and emitted from the end of the optical fiber 25a, and the measuring device 42 determines the temperature at a plurality of locations in the length direction of the optical fiber 25a based on the light emitted from the optical fiber 25a. That is, a continuous temperature distribution over the entire length of the optical fiber 25a is detected. Information on the temperature distribution thus obtained is transmitted from the measuring device 42 to the control computer 41, and the control computer 41 detects the temperature distribution of the optical fiber 25a provided in the optical fiber temperature sensor 40.

  As described above, each control signal is transmitted from the control computer 41 to each optical fiber temperature sensor 40 provided on each cable 5, whereby the measurement is performed by each optical fiber temperature sensor 40. The temperature distribution information is detected by the control computer 41. Thereby, in the control computer 41, the temperature distribution of the optical fiber 25a provided at the center of each cable 5, the temperature distribution of the optical fiber 25a provided on the concentric circle of radius R / 2, and the concentric circle of radius R. The temperature distribution of the optical fiber 25a provided above is detected. That is, the temperature distribution in the central portion of each cable body 21, the temperature distribution on the concentric circle of radius R / 2 in the cable body 21, and the temperature distribution on the concentric circle of radius R in the cable body 21 are detected. In this way, the temperature inside each cable body 21 can be measured at a plurality of locations in both the length direction and the radial direction (cross section) of the cable body 21, and the temperature distribution of the entire cable body 21 can be accurately measured. Can be investigated.

  Furthermore, in the calculation part 41a of the control computer 41, the shape, length, etc. of each cable main body 21 can be calculated based on the measured temperature distribution of each cable main body 21. That is, it is possible to indirectly detect the deformation of the cable main body 21 caused by the temperature change, and it is possible to calculate the tension of the cable main body 21 and the like. By referring to these calculation results and determining whether the shape, length, tension, stress distribution, etc. of each cable body 21 is within the design range, it is necessary to perform tension work etc. of each cable body 21. It can be determined whether or not there is.

  According to such a configuration, by providing at least one optical fiber 25a, that is, the optical fiber temperature sensor 40, in the cable 5, the temperature distribution in the length direction of the cable 5 can be reliably measured. Compared to the conventional temperature measurement method, the temperature at a plurality of locations on the cable 5 can be measured easily and efficiently, and more precisely at many locations. That is, a continuous temperature distribution can be measured over the entire length of the cable 5. Furthermore, the temperature distribution of the cable 5 can be measured more accurately by providing two or more optical fibers 25a. Further, by providing the optical fiber 25a inside the cable 5 and directly measuring the temperature inside the cable 5, the temperature inside the cable 5 can be measured easily and accurately. Therefore, the shape, length, tension, stress distribution, etc. of the cable 5 can be accurately measured based on the temperature distribution, and the maintenance of the cable-stayed bridge 1 can be appropriately performed.

  Further, the optical fiber temperature sensor 40 has a simple structure and good durability of the optical fiber built-in line 25 as compared with a conventional device used for temperature measurement. For example, unlike a temperature sensor such as a thermocouple, it is not necessary to replace it, so that the labor and cost required for maintenance can be reduced. In particular, since the optical fiber built-in line 25 is built in the cable 5 and disposed integrally with the cable 5, damage and deterioration of the optical fiber built-in line 25 can be reliably prevented. In addition, devices such as a temperature sensor and wiring are not exposed on the surface of the cable 5, the structure of the surface of the cable 5 can be simplified, and the weather resistance and design of the cable 5 can be improved.

  The exemplary embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious for those skilled in the art that various changes and modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  In the above embodiment, the optical fiber temperature sensor 40 and the measurement system 6 for measuring the temperature of the cable 5 have been described. However, the predetermined information measured by the optical fiber sensor or the measurement system is not limited to the temperature. For example, an optical fiber strain sensor may be provided as the optical fiber sensor. That is, a measurement system that detects the strain distribution of the optical fiber using an optical fiber strain sensor and detects the tension, stress distribution, shape, length, and the like of the cable 5 from the strain distribution may be configured. In this case as well, strain can be accurately detected over the entire length of the optical fiber, and the tension, stress distribution, shape, length, etc. of the cable 5 can be measured efficiently and accurately.

  The optical fiber sensor may be an optical fiber humidity sensor that measures humidity as predetermined information, and may constitute a measurement system that measures the humidity distribution in the cable 5 using such an optical fiber humidity sensor. . In this case, the humidity in the cable 5 can be adjusted appropriately based on the measured humidity distribution.

  Furthermore, a plurality of types of optical fiber sensors that detect different types of information may be provided for one cable 5. For example, any two or more of an optical fiber temperature sensor 40, an optical fiber strain sensor, and an optical fiber humidity sensor may be provided. By doing so, it is possible to measure information on any two or more of the temperature, strain, and humidity of the cable 5 and to investigate the state of the cable 5 in more detail. Therefore, it is useful for the maintenance management of the cable 5. Further, the optical fiber sensor may be configured to detect two or more different types of information. For example, an optical fiber temperature strain sensor, that is, a configuration capable of measuring both temperature and strain information may be used.

  The arrangement of the optical fiber sensors in the cable main body 21 is not limited to the arrangement of concentric circles as shown in the above embodiment, and it is sufficient that at least one optical fiber is provided in the cable 5. Further, the configuration of the optical fiber, the optical fiber built-in line, the optical fiber sensor, etc., the principle of the measurement method, and the like are not limited to those exemplified in the above description, and various types can be applied.

  The structure of the cable is not limited to the parallel wire strand described in the above embodiment. For example, the steel wire 30 and the optical fiber built-in wire 25 constituting the aggregate 31 do not necessarily have to be twisted together. Further, for example, a multi-strand structure, that is, a structure in which a plurality of cable main bodies 21 as shown in the embodiment are further converged into a single cord shape may be used.

  The structure of the cable-stayed bridge 1 and the mode of arrangement of the cables 5 are not limited to those shown in the above embodiments, and the present invention can be applied to cable-stayed bridges having various structures. Furthermore, the present invention can be applied to other types of bridges, for example, cables (main cables) used for suspension bridges. Further, the bridge is not limited to a bridge built on a river, but may be a bridge built on a strait, a road, or the like.

  Further, the present invention is not limited to the cable used for the bridge, and the structural member supported by the cable body is not limited to the bridge girder. For example, a cable for a suspended structure used for a suspended roof structure in a building structure may be used, and the structural member supported by the cable body may be a roof. In this case, for example, when there is snow on the roof, the load applied to the roof by the snow, the stress distribution generated in the roof, the temperature distribution, etc. can be detected by an optical fiber sensor provided in the cable. That is, it is possible to determine whether or not work such as snow removal is necessary based on the measurement result of the optical fiber sensor.

  The present invention can be applied to a cable for a suspension structure used in a building structure or a civil engineering structure such as a bridge and a suspended roof.

It is the schematic side view which showed the structure of the cable-stayed bridge. It is a schematic front view of a cable-stayed bridge. It is explanatory drawing explaining the structure of a cable and a temperature measurement system. It is explanatory drawing which showed the structure of the cable. It is a cross-sectional view of a cable main body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cable-stayed bridge 5 Cable 6 Measurement system 21 Cable main body 25 Optical fiber built-in line 25a Optical fiber 30 Steel wire 31 Assembly 40 Optical fiber temperature sensor 41 Control part 42 Measuring apparatus

Claims (8)

A cable for a suspension structure having a cable body for supporting a structural member,
A cable for a suspension structure, wherein an optical fiber is provided along a length direction of the cable body. The cable body includes a plurality of wires and the optical fiber,
The cable for a suspension structure according to claim 1, wherein a parallel wire strand is constituted by the plurality of wires. The suspension cable according to claim 1 or 2, wherein one or more of the optical fibers are provided inside the cable body. The said optical fiber is provided along the at least center part of the said cable main body, The cable for suspension structures in any one of Claims 1-3 characterized by the above-mentioned. The cable for a suspension structure according to any one of claims 1 to 4, wherein the cable is used for a bridge. An optical fiber provided in the suspension structure cable according to any one of claims 1 to 5;
A measurement system comprising: a measurement device that detects predetermined information using light emitted from the optical fiber. The measurement system according to claim 6, wherein the predetermined information is a temperature distribution, a strain distribution, and / or a humidity distribution of the optical fiber. The measurement system according to claim 6 or 7, further comprising a calculation unit that calculates the shape and / or tension of the cable body based on the predetermined information.

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