JP5604760B2 - Tension member - Google Patents

Description

  The present invention relates to a tension member for causing a load to act on a bearing surface by being fixed to the bearing surface of a ground or a concrete structure in a tensioned state. In particular, the present invention relates to a tension member that can accurately detect distortion generated in the tension member.

  As a means for managing the load of the ground anchor installed on the slope or the like, there is a method using an optical fiber. For example, Patent Document 1 discloses a configuration in which an optical fiber serving as a strain sensor is wound around a tension member having an anchor structure, and an OTDR (Optical Time Domain Reflectmeter) device is connected to the optical fiber. When changes in underground conditions such as landslides or signs of landslides or changes in groundwater occur in the anchor construction construction ground, the strain generated in the tension member is detected with an optical fiber, and the strain is output as a detection result with OTDR. . Thereby, the load variation of the anchor accompanying the change of underground conditions can be monitored.

Japanese Patent Laid-Open No. 9-21661

  In the above technique, the optical fiber is wound around the tension member as it is or stored in a thin stainless steel tube. On the other hand, there are a lot of concrete, metal members, gravel and rocks around the tension member at the construction site of the anchor structure, and it is necessary to be careful when handling the tension member so as not to damage the optical fiber. is there. Moreover, the soundness of the optical fiber is not known unless a detection test is performed after the construction of the anchor structure is completed.

  The present invention has been made in view of the above circumstances, and one of its purposes is that a tension member used in an anchor structure or the like includes an optical fiber that detects strain generated in the tension member, and the optical fiber is damaged. It is in providing the structure of the tension member which is hard to do.

  Another object of the present invention is to provide a strain detection system for a tension member fixing structure using the tension member of the present invention.

  The tension member according to the present invention relates to a tension member for applying a load to the bearing surface by being fixed on the bearing surface in a state where a tension force is applied. The tension member is a hollow body, an optical fiber housed in the hollow body and used as a strain sensor, and filled between the hollow body and the optical fiber to hold the position of the optical fiber in the hollow body. It is characterized by comprising an agent and a plurality of tension wires arranged to surround the outer periphery of the hollow body and bearing the tension force.

  According to this configuration, it is possible to prevent the optical fiber from being damaged when the tension member is used by housing the optical fiber serving as the strain sensor in the hollow body arranged to be covered with the tension wire group. . Further, by filling the space between the hollow body and the optical fiber with a filler, the strain generated in the tension member can be reliably transmitted sequentially through the tension element wire, the hollow body, and the filler.

  As one form of this invention tension | tensile_strength member, it is mentioned that a some tension | tensile_strength wire is twisted around the outer periphery of a hollow body.

  The tension members can be easily bent by twisting the plurality of tension wires around the outer periphery of the hollow body. Further, according to this configuration, since each tension strand is in a state along the oblique direction with respect to the hollow body, the contact area with the strand per unit length of the hollow body increases, and the hollow body at the fixing point Is hard to be crushed.

  As one form of the tension member of the present invention, the hollow body may be a corrugated tube or a spiral body.

  According to this structure, the tension member excellent in flexibility can be constructed | assembled by making a hollow body into a corrugated pipe | tube or a helical body.

  As one form of the tension member of the present invention, an anticorrosion coating is provided on the outer periphery of the hollow body.

  According to this configuration, the hollow body itself can have high anticorrosion properties. In particular, since the inside of the hollow body is filled with a filler, if the anticorrosion coating is provided on the outer periphery of the hollow body, both the inside and outside of the hollow body can have an anticorrosion structure.

  As one form of this invention tension member, providing the anti-corrosion coating | cover which covers the outer surface of a tension | tensile_strength strand group collectively is mentioned.

  According to this structure, since the tension | tensile_strength strand is collectively covered with the anti-corrosion coating, the tension member which has high anti-corrosion property can be comprised. Moreover, formation of anticorrosion coating is also easy.

  As one form of the tension member of the present invention, an anticorrosion coating is provided on the outer periphery of each tension wire.

  According to this structure, since each tension | tensile_strength strand is equipped with the anticorrosion coating | cover, the perimeter of each strand is covered with an anticorrosion coating | cover, and the tension member which has high anticorrosion property can be comprised.

  One form of the tension member of the present invention is that the filler is an epoxy resin.

  Epoxy resin is a resin that is rich in fluidity before curing and has sufficient hardness after curing, so that the optical fiber is held in the hollow body and the strain acting on the tension member is reliably transmitted to the optical fiber. It is suitable for.

  On the other hand, the strain detection system of the present invention is generated in a tension member to which a tension force is applied, a fixing tool for fixing an end portion of the tension member to the bearing surface, and applying a load to the bearing surface, and the tension member. A strain detection system for a tension member fixing structure, which includes a strain sensor that detects strain and a strain detection device that outputs a detection result of the strain sensor. The tension member is a hollow body, an optical fiber housed in the hollow body and used as a strain sensor, and filled between the hollow body and the optical fiber to hold the position of the optical fiber in the hollow body. An agent and a plurality of tension wires arranged to surround the outer periphery of the hollow body and bearing the tension. The strain detection device is an OTDR device connected to an optical fiber.

  According to this configuration, by using the above-described tension member of the present invention as the tension member, it is possible to suppress damage to the optical fiber and reliably transmit the strain acting on the tension member to the optical fiber. Then, by outputting the strain transmitted to the optical fiber by OTDR, the strain distribution along the optical fiber can be easily monitored.

  According to the tension member of the present invention, a structure in which an optical fiber serving as a strain sensor is hardly damaged can be obtained.

  In addition, according to the strain detection system for the fixing structure of the tension member of the present invention, the strain sensor of the present invention can be used to make the optical fiber a strain sensor, and the strain distribution along the tension member can be easily achieved. Can be monitored.

  The tension member of the present invention includes a tension wire, a hollow body, an optical fiber, and a filler as components. Hereinafter, each component will be described in more detail, and a fixing structure using a tension member and a distortion monitoring system will also be described.

<Tension wire>
The tension strand bears a tension force applied to the tension member. Therefore, the strand which comprises a PC steel strand is used suitably for this tension strand. The tension strand may be a bare strand without an anticorrosion coating or may be provided with an anticorrosion coating. Moreover, although the arrangement | positioning form to the hollow body of a tension | tensile_strength wire may be added vertically, it is preferable to wind helically. What is necessary is just to select suitably the specific composition of a tension | tensile_strength strand, a cross-sectional area, and the number according to the tension | tensile_strength introduced into a tension | tensile_strength member.

  However, the number of tension wires is a number that can substantially surround the outer periphery of the hollow body. In that case, it is preferable that the arrangement | positioning of the tension | tensile_strength wire which surrounds the outer periphery of a hollow body arranges substantially uniformly in the cross section of a tension member. Typically, the number of tension wires is 5 or more.

  Moreover, it is preferable that the clearance gap between adjacent tension | pulling strands shall be 0.2 mm or more in total. By securing such a gap between the tension wires, when the tension member is bent, the movement allowance of the strands is secured between the strands arranged on the outer periphery of the hollow body, and the flexibility of the strand Can be improved. In particular, by providing such a gap, when the grout or the like is filled around the tension member, compared to the case where there is no gap between the tension elements, the adhesion between the grout and the tension element can be increased. it can. This is because the grout is filled also between the tension wire and the hollow body through the gap, so that the surface area of the strand in contact with the grout increases.

  On the other hand, when the tension wire interval is too large, the arrangement of the strands surrounding the outer periphery of the hollow body tends to be biased. When the strands are biased, the force that presses the hollow body from the outer periphery is biased. Therefore, when the tension member is gripped by a wedge or the like constituting the fixing tool, the hollow body disposed at the center of the tension member is crushed. There is a risk that. In addition, when the spacing between the wires is too large, there may be a problem that the hollow body protrudes from between the wires, particularly when the tension member is bent. For this reason, it is desirable that the total wire spacing is smaller than the outer diameter of the hollow body, in particular, the outer diameter of the strained strand so that the hollow body does not jump out between the strands.

<Hollow body>
The hollow body has a function of accommodating an optical fiber and protecting the optical fiber from an external force. The tension member of the present invention is fixed to the bearing surface with a fixing tool. Therefore, the material, thickness, etc. may be selected so that the hollow body is not crushed even when the tension wire is compressed from the outer periphery with fixing. A metal such as steel is suitable as the material of the hollow body, but a resin hollow body may be used as long as there is no problem in strength.

  Examples of the shape of the hollow body include a pipe material and a spiral body. In the case of a pipe material, a straight pipe may be used, but in consideration of the flexibility of the tension member, a corrugated pipe is preferable. Also, the spiral body has excellent flexibility. The linear body forming the spiral may be a wire having a circular cross-sectional shape, or may be a belt-like material having a flat cross-sectional shape. A typical example of a spiral body using a wire is a spring material, and a typical example of a hollow body using a strip is a spiral steel strip. If adjacent turns of the spiral are in close contact with each other, a spiral having high mechanical strength can be obtained, and thus the optical fiber has excellent protection. Conversely, if there is a gap between adjacent turns, when the filler is filled into the hollow body, the filler leaks out from the gap, and the gap is also filled in the gap between the tension wire and the hollow body. Can do. In particular, when this hollow body is combined with a tension wire, the bending diameter of the tension member can be bent at 12 times the envelope diameter of the tension wire (the circumscribed circle of a plurality of strands surrounding the hollow body). It is preferable that the flexibility which can be obtained is obtained. A tension member having such a bending characteristic is very easy to handle in an actual site. This hollow body may be a bare hollow body without an anticorrosion coating, or may be one provided with an anticorrosion coating on the outer periphery. Examples of the anticorrosion coating include a resin coating such as epoxy and a corrosion-resistant metal coating such as chrome plating.

<Optical fiber>
The optical fiber is used as a sensor for detecting strain acting on the tension member. More specifically, it is used by being connected to a strain detection device such as an OTDR device. As long as it can be used for this OTDR device, the type, configuration, and material are not particularly limited.

  In general, a single mode optical fiber is used as an optical fiber that is connected to an OTDR device. Of course, any multimode optical fiber may be used as long as it can be used as a strain sensor.

  The material of the optical fiber may be a glass fiber such as quartz, or a plastic fiber such as a fully fluorinated polymer, polymethyl methacrylate, or polycarbonate.

  Further, this optical fiber can be used with any configuration of an optical fiber core wire and an optical fiber cord. The optical fiber core is generally a structure having a coating layer on the clad of the optical fiber. In some cases, a buffer layer is interposed between the cladding and the coating layer. If necessary, it may be a multicore tape core wire in which a plurality of cores are coated in parallel. If there are a plurality of optical fibers, it can be used as a backup in case any optical fiber is damaged. Further, the optical fiber cord has a structure in which a high-strength fiber such as aramid is vertically attached on the optical fiber core and a sheath such as PVC is further formed thereon. If it is an optical fiber cord, it can be made a structure still more resistant to damage.

  Moreover, it is preferable that this optical fiber is kept coaxial with the hollow body as much as possible. By arranging the optical fiber substantially along the hollow body, distortion can be detected with a shorter length than an optical fiber wound in a spiral shape.

<Filler>
The filler is preferably hardened after filling into the hollow body, and has a hardness that can sufficiently transmit strain applied to the tension member to the optical fiber after hardening. More specifically, a resin material, particularly an epoxy resin (for example, a two-component mixed type) is preferable. In addition, it is conceivable to use grouts that are constructed on site as fillers.

  When the filler is shipped by winding the tension member around a drum, it is preferable that the curing is completed before the winding. When the filler is cured after winding on the drum, the tension member is likely to be curled, so that curling can be mitigated by curing the filler before winding.

<Method for producing tension member>
(Composite tension wire and hollow body)
The above tension members are prepared as components such as a tension wire, a hollow body, an optical fiber, and a filler, and first, the strand and the hollow body are combined. Before and after the composite or during the composite, an anticorrosive coating is formed on at least one of the tension wire and the hollow body as necessary. A known electrostatic powder coating method can be suitably used for forming the anticorrosion coating. Specific examples of complex forms include the following. In the following embodiments, a bare wire without a corrosion-resistant coating, a bare wire with a tensile wire with an anti-corrosion coating, a bare wire with a hollow body without an anti-corrosion coating, and a hollow body with an anti-corrosion coating. The body.

(1) A bare wire is twisted on a bare hollow body and no anticorrosion coating is formed.
In this case, since both the tension wire and the hollow body do not have the anticorrosion structure, it is preferable to use it for a structure in which the outer side of the tension member is covered with grout or the like.

(2) Twist the coated strand on the bare hollow body.
In this case, each tension | strength strand has an anticorrosion structure individually, and it can be set as the structure excellent in the anticorrosion property of the strand.

(3) Twist the bare wire on the coated hollow body.
In this case, the hollow body itself has a configuration excellent in anticorrosion properties, with the inside being a filler and the outside being protected by an anticorrosion coating.

(4) Twist the coated wire on the coated hollow body.
In this case, since each tension | tensile_strength wire and hollow body itself are made into an anticorrosion structure individually, it can have an extremely high anticorrosion characteristic as the whole tension member.

(5) A bare strand is twisted on a bare hollow body or a covered hollow body, and an anticorrosion coating is formed collectively from the outer periphery of the bare strand group.
In this case, there is a high possibility that the anticorrosion coating is not formed between the tension strands and the hollow body, but the anticorrosion coating is formed on the outer surface of the tension strand group, so the environment inside each strand It prevents water from entering and achieves high anticorrosion properties.

(6) The bare strands are twisted with a bare hollow body, and the bare strands are separated from the bare hollow body by the eye plate to form an anticorrosion coating on the bare strands and the bare hollow body, and the resin of the anticorrosion coating is cured. The strand previously separated from the hollow body is returned to the original position.
In this case, each element wire is covered with the anticorrosion coating, the hollow body is also covered with the anticorrosion coating, and the anticorrosion coating of the element wire and the anticorrosion coating of the hollow body are integrated. Therefore, no gap is formed between each strand and the hollow body, and very high corrosion resistance can be realized.

(Optical fiber insertion)
When the tension wire and the hollow body are combined, an optical fiber is inserted into the hollow body. As specific examples of this insertion, pulling in, feeding out, gas pressure feeding, and the like are conceivable. When drawing in the hollow body in advance, the guide material is inserted into the hollow body in advance and exposed from both ends of the hollow body, an optical fiber is connected to one end of the guide material, and the other end side of the guide material By pulling, the optical fiber is inserted into the hollow body. This method is an easy and practical technique regardless of the form of the hollow body. The feeding is carried out by a feeding roller or the like from the one end side of the hollow body toward the other end side of the hollow body. This method seems to be effective when the hollow body is relatively short or a straight pipe. In gas pressure feeding, an air introduction device is connected to one end of a hollow body, and an optical fiber is fed into the hollow body using the flow of air. This method also seems to be effective when the hollow body is relatively short or a straight pipe.

  In any case, the optical fiber is preferably inserted into the hollow body after the above-described anticorrosion coating is formed. When the anticorrosion coating is formed after the optical fiber is inserted into the hollow body, the hollow body is heated during the formation of the anticorrosion coating, so that the optical fiber core wire or the optical fiber cord coating or the optical fiber is an optical fiber. This is because the fiber itself may be thermally damaged.

(Filler filling)
When the optical fiber is inserted into the hollow body, a filler is filled between the hollow body and the optical fiber. In this case, it is preferable that the optical fiber is filled with tension as much as possible so as to be as coaxial as possible with the hollow body. As a result, the optical fiber can be held at substantially the same position from the inner surface of the hollow body, and the non-uniformity of strain transmission to the optical fiber can be suppressed. When drawing is used as a method of inserting the optical fiber into the hollow body, tension is inevitably applied to the optical fiber along with this drawing, so that it is easy to fill the filler as it is. When the filler is filled in the hollow body, the filler is cured and the optical fiber is held in the hollow body.

(Other)
When the tension member is used for an anchor or the like, one end side of the optical fiber is embedded in the ground. In that case, it is conceivable that the buried side end of the optical fiber is not exposed from the end of the hollow body, or the optical fiber is exposed from the end of the hollow body. In either case, it is preferable to protect the buried side end of the optical fiber by covering the end of the tension member with an appropriate cap.

<Tension member fixing structure>
In the tension member fixing structure, one end side of the tension member is normally a tension side and the other end side is a fixed side. As a specific fixing structure, several configurations can be selected according to the object for which the tension member is used. For example, in the anchor structure, the tension side becomes the end of the free length portion of the tension member, and the fixed side becomes the fixing length portion. Moreover, in the outer cable used for the bridge girder, one end has a tension side fixing structure and the other end side has a fixed side fixing structure.

  In order to fix the tension member, a grip member for gripping the tension member and a support member for supporting the grip member can be used. When a wedge that is formed in a truncated cone shape by combining a plurality of divided pieces and grips the tension member is used as a gripping member, an anchor disk having a conical hole into which the wedge is fitted is used as a supporting member. When a crimping sleeve that is crimped to the end of the tension member is used as the gripping member, an anchor disk having a through hole with an inner diameter that penetrates the tension member but does not pass through the crimping sleeve is used as the bearing member. A male screw is formed on the outer periphery of the crimp sleeve, and a nut is screwed onto the male screw to fix the tension member to the anchor disk.

<Strain detection system>
In order to perform strain monitoring using the tension member of the present invention, a strain detection device is connected to the optical fiber of the tension member constituting the fixing structure. An OTDR device can be suitably used as the strain detection device. The OTDR apparatus measures the wavelength of Brillouin scattered light out of backscattered light that enters a light pulse from one end of the optical fiber and returns from the middle of the optical fiber. When a change occurs around the tension member such as the tension member itself or in the ground, stress is applied to the optical fiber in the tension member, and Brillouin scattered light corresponding to the stress is generated. Therefore, if the generated wavelength of the Brillouin scattered light along the optical fiber is monitored by the OTDR device, it can be detected that the tension member itself or the surrounding environment of the tension member has changed. In addition, the distance from the incidence of the light pulse to the return of the backscattered light can be measured to measure the distance to the distortion occurrence point.

  Note that the temperature distribution along the optical fiber can be monitored by connecting the optical fiber to a DTS (Distributed Temperature Sensor System) device instead of the strain detection device. The DTS measures the intensity of Raman scattered light that enters a light pulse from the end of an optical fiber and returns from the middle of the optical fiber. Since the intensity of the Raman scattered light has a correlation with the temperature, it is possible to measure the temperature distribution along the optical fiber. Further, the position of the temperature change point can be specified by measuring the time from when the light pulse is incident until the Raman scattered light returns.

<Application field>
The tension member of the present invention is expected to be applied to various fields. Specifically, tension members in bridges, for example, diagonal members of cable-stayed bridges, external cables that prestress external cable methods (including extradosed bridges), and prestresses on internal cable methods Various types of anchors such as inner cables and ground anchors, and tension materials for reinforcing dam dams.

  In this example, an example in which a PC structure is formed using the tension member of the present invention will be described with reference to FIGS.

[Tension member]
1A is a partial cross-sectional perspective view showing the tension member of this example, and FIG. 1B is a cross-sectional view taken along line AA of FIG. As shown in FIG. 1B, the tension member 1 has a structure in which tension wires 12 are arranged so as to surround a corrugated tube (hollow body) 11 in a cross section. More specifically, the tension member 1 of this example includes a corrugated pipe 11 and nine strands 12 twisted around the outer periphery of the corrugated pipe 11. Of course, the number of strands is not limited to 9, and may be, for example, a tension member in which 5 or 7 strands are twisted around the corrugated tube. When the number of strands is 9, the total distance between each strand is about 2mm.

  The corrugated tube 11 is made of non-abrasive welding steel (CanExcel: registered trademark) with Cr plating. The corrugated tube 11 made of such a material is excellent in flexibility and is not bent when bent, so that the strength of the tension member 1 does not decrease. Further, the corrugated structure of the corrugated tube 11 is strong against pressure from the outer peripheral side of the tube 11, and is difficult to ablate even when the tension member 1 is gripped by a wedge.

  The tension wire 12 is made of a steel type: SWRS82B (JIS G 3502). Of course, the material of the wire 12 is not limited to the above-mentioned steel types, and a Si-rich material (Si content is more than 0.32% by mass) or the like can be suitably used. These strands are excellent in strength and have appropriate flexibility.

  Table 1 shows the characteristics of the corrugated tube 11 and the tension wire 12. The outer diameter of the corrugated pipe in Table 1 is the outer diameter of the corrugated peak, and the inner diameter of the corrugated pipe 11 is the inner diameter of the corrugated trough.

  Manufacture of the tension member 1 of this example using the corrugated tube 11 and the strand 12 described above is performed as follows.

  First, the wire 12 is wound around the corrugated tube 11 around the corrugated tube 11. Specifically, the strand 12 and the corrugated pipe 11 are set in a stranding machine and twisted together.

  Next, the tension member 1 that has been twisted is subjected to a blueing treatment at about 400 ° C. for about 30 seconds by applying a tension of 10 to 40% of the breaking load of the tension member 1 (the breaking load expected from the material). . By performing the bluing treatment, the toughness of the tension member 1 can be improved and the bending characteristics can be improved. The preferable conditions for bluing are 300 to 450 ° C. and 10 to 90 seconds.

  Next, the optical fiber core wire 30 is inserted into the corrugated tube 11. Here, both ends of the guide material (not shown) inserted in advance in the corrugated tube 11 are exposed from the end of the corrugated tube 11, and the optical fiber core wire 30 is connected to one end of the guide material, The optical fiber core wire 30 is pulled into the corrugated tube 11 by pulling the other end of the guide material. The optical fiber core wire 30 to be drawn is a single-core single mode plastic fiber.

  When the optical fiber core wire 30 can be inserted into the entire length of the corrugated tube 11, the filler 40 is filled between the corrugated tube 11 and the optical fiber core wire 30 with tension applied to the optical fiber core wire 30. At this time, the optical fiber core wire 30 is made to be coaxial with the corrugated tube 11 as much as possible. As the filler 40, a two-component mixed epoxy resin was used. When the epoxy resin is filled from one end side of the corrugated tube 11 and the exposure of the epoxy resin is confirmed from the other end side, the filling of the resin is stopped and the resin is cured. When the tension member 1 is wound around a reel and shipped, the reel is wound after the epoxy resin is cured.

  Table 2 shows the dimensions and mechanical characteristics of the main part of the tension member produced as described above. The diameter of the tension member in Table 2 is the diameter of the envelope circle of the strand 12.

[Formation procedure of PC structure]
The PC structure is formed using the tension member 1 as described above. FIG. 2 is a process explanatory view showing a method of forming a PC structure by post tension. In order to form the PC structure, first, the mold frame 20 is installed (see (A) in the figure), and then the anchor plate P1, the portion of the mold frame 20 where the tension member 1 is to be arranged is previously set. While P2 is fitted, the buried pipe BP is placed in the mold 20 (see (B) in the figure). Although not shown, the anchor plate P2 has a grout inlet communicating with the buried pipe BP, and the anchor plate P1 has a grout inlet communicating with the buried pipe BP.

  Next, the concrete is placed in the mold 20, and after the concrete has hardened, the mold 20 is removed, and a tension member is inserted into the buried pipe BP and tensioned with a jack (FIG. 2 (C) See). Since the allowable limit elongation of the optical fiber core 30 is sufficiently larger than the elongation of the tension strand 12 due to this tension, the optical fiber core 30 is not broken by this tension. When the tension member 1 is tensioned, the tension member 1 is first fixed with the fixing-side fixing tool on one end side (the right side of the drawing) of the concrete block CB, and then the tension member 1 is tensioned on the other end side (the left side of the drawing). The tension member 1 is fixed by the tension side fixing tool.

  More specifically, the fixed-side fixing tool AD1 and the tension-side fixing tool AD2 are configured as shown in FIG. That is, the tension member 1 includes a wedge W1 that grips the tension member 1, an anchor disk D1 having a conical hole in which the wedge W1 is fitted, and an anchor plate P1 interposed between the disk D1 and the surface of the concrete block CB. Fixing is performed by the fixed-side fixing tool AD1 and the tension-side fixing tool AD2 including the same wedge W2, anchor disk D2, and anchor plate P2.

  When the tension member 1 is tensioned, the tension member 1 is extended, and a force (tensile force) is generated for the stretched tension member 1 to return. Then, by fixing the tension member 1, the tension force of the tension member 1 is transmitted as a load to the surface (bearing surface) of the concrete block CB to form a PC structure.

  When tensioning and fixing of the tension member 1 is completed, grout is injected into the buried pipe BP from the grout inlet, and it is confirmed that the grout leaks from the grout outlet, and the grout filling operation is completed. As a result, the buried pipe BP is filled with grout.

  As described above, when the grout filled in the buried pipe BP is cured, an OTDR device (not shown) is connected to the optical fiber core wire 30 exposed from the tension side fixing tool. When cracks occur in the concrete of a PC structure or when the tension member itself deteriorates or damages, the tension member 1 is distorted. This strain is applied to the optical fiber core 30 via the corrugated tube 11 and the filler 40. Communicated. As a result, a portion where the strain increases is generated in the local portion of the optical fiber core wire. Therefore, if the strain is monitored by the OTDR device, a change occurring in the PC structure or the tension member can be detected.

  According to the configuration of this example, the optical fiber core wire 30 is housed in the corrugated tube 11 and is located almost at the center of the tension member 1, and thus is damaged during storage, transportation, and construction after the tension member 1 is manufactured. The possibility can be reduced as much as possible. In addition, by filling the filler 40 between the corrugated tube 11 and the optical fiber core wire 30, the strain generated in the tension member 1 can be reliably transmitted to the optical fiber core wire 30.

<Modification>
In the first embodiment, neither the tension wire nor the corrugated tube has the anticorrosion coating, but an anticorrosion coating such as an epoxy resin may be formed on at least one of them. Thereby, it is possible to realize a fixing structure having further excellent anticorrosion characteristics.

  Next, in this example, a ground anchor formed by using a tension member in which a sheath is further provided on the outer periphery of the tension member in FIG. 1 will be described with reference to FIGS. 4 and 5. In addition, since the tension member of this example is a main difference with the tension member of Example 1 in the point which has a sheath in the outer periphery of a tension | tensile_strength strand group, about the same structure, the code | symbol same as Example 1 is shown. A description thereof will be omitted.

  As shown in FIG. 4, the tension member 2 has a sheath 13 outside the tension element wire 12. The sheath 13 can be a plastic tube such as polyethylene. Of course, the sheath 13 may be made of metal. In addition, the sheath 13 may have a corrugated shape that is more flexible.

  In the corrugated tube 11 of the tension member, a single optical fiber core wire 30 is accommodated in a straight line (see FIG. 5). That is, the optical fiber core wire 30 is introduced from one end side (free length portion side) of the corrugated tube 11, and is exposed from the end portion of the tension member on the other end side (fixing length portion side). The exposed end portion is covered and protected with an appropriate cap 50 or the like. It is preferable to fill the cap 50 with a filler.

  Such a tension member is arranged as a ground anchor (tension member 2) in the natural ground G in which the drilling hole H is formed, and is used to apply tension to the concrete (bearing surface) C covering the natural ground G. .

  To place the tension member 2 in the arrangement state shown in FIG. 5, first, the sheath 13 is peeled off by a predetermined length on one end side of the tension member 2 so that the wire 12 is exposed at that portion. The exposed region of the wire 12 becomes a fixing length portion, and the remaining region of the sheath 13 becomes a free length portion. At the end of the sheath 13 at the boundary between the free length portion and the fixing length portion, a water stop portion 14 that seals the gap between the sheath 13 and the strand 12 is formed.

  Next, in a state where the tension member 2 is inserted through the tension member insertion holes of the anchor disk D3 and the anchor plate P3, both the D3 and P3 are temporarily fixed to the natural ground G, and the hole H is sealed. The anchor disk D3 and the anchor plate P3 are provided with a grout discharge port communicating with the inside of the drilling hole H as well as a grout injection port communicating with the inside of the drilling hole H. The anchor disk D3 and the anchor plate P3 may be separately provided with a communication pipe that leads from the natural ground G to the drill hole H without providing a grout inlet or outlet.

  When the arrangement of the tension member 2, the anchor disk D3, and the anchor plate P3 is completed, the grout is injected into the hole H from the grout inlet. The injected grout fills the hole H. This grout injection is completed when the grout filled in the hole H is discharged through the grout outlet.

  After a predetermined time has elapsed from filling of the grout H with the grout, the grout is hardened. At that time, only the fixing length portion of the tension member 2 is fixed in the hole H.

  Next, the tension member 2 protruding from the anchor disk D3 is tensioned with a jack and fixed to the anchor disk D3 with the wedge W3.

  After the tension member 2 is fixed, the OTDR device 60 is connected to the optical fiber core wire 30 exposed from the free length side end of the tension member. Thereafter, distortion may be monitored in the same manner as in the first embodiment.

  As described above, the tension member of the present invention can also be suitably used as a ground anchor that imparts prestress to natural ground.

  In addition, this invention is not limited to the Example mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably. For example, in the case where the tension wire has an anticorrosion coating, solid particles such as silica sand may be adhered before the constituent resin of the coating is cured to increase the adhesion force with the grout of the tension member.

  The tension member of the present invention can be suitably used for applying a load to a bearing surface such as a concrete structure or the ground. In addition, the strain detection system of the present invention can be used to monitor strain associated with variations in the tension member itself or the tension member in the tension member fixing structure.

(A) is a partial cross-sectional perspective view of the tension member of the present invention, and (B) is a cross-sectional view taken along the line AA of (A). FIG. 3 is a process explanatory view showing the procedure of the prestressed construction method described in Example 1. (A) shows the arrangement state of the formwork, (B) shows the arrangement state of the anchor plate and the buried pipe, (C) shows the arrangement state of the tension member of the present invention, (D) shows the injection state of the grout, (E ) Indicates the finished state of the method. 3 is a partial cross-sectional view of a fixing structure for fixing a tension member according to Embodiment 1. FIG. It is a cross-sectional view of the tension member of the present invention according to Example 2. It is a schematic block diagram of the ground anchor which concerns on Example 2 which uses this invention tension | tensile_strength member which has a sheath in outer periphery.

Explanation of symbols

1,2 Tensile member 11 Corrugated tube 12 Tensile wire 30 Optical fiber core wire
40 Filler 50 Cap 60 OTDR device
13 Sheath 14 Water stop 20 Mold
CB concrete block BP buried pipe
G Ground mountain C Concrete H Drilling hole
AD1 Fixed side fixing device AD2 Tension side fixing device
P1, P2, P3 Anchor plate D1, D2, D3 Anchor disc
W1, W2, W3 wedge

Claims (7)

A tension member for applying a load to the bearing surface by being fixed on the bearing surface in a state where tension is applied,
A corrugated tube or a hollow hollow body;
An optical fiber housed in the hollow body and used as a strain sensor;
A filler filled between the hollow body and the optical fiber to maintain the position of the optical fiber in the hollow body;
The twisted so as to surround the outer periphery of the hollow body, and a plurality of tension wires to bear the tension,
A tension member, wherein the filler is an epoxy resin . The tension member according to claim 1 , further comprising an anticorrosion coating on an outer periphery of the hollow body. Tensioning member according to claim 1 or 2, characterized in that it comprises an anticorrosive coating collectively covering the outer surface of the tensioning strand group. The tension member according to any one of claims 1 to 3 , further comprising an anticorrosion coating on an outer periphery of each tension wire.   The tension member according to claim 3, further comprising solid particles attached to the anticorrosion coating.   6. The tension member according to claim 1, wherein gaps between adjacent tension wires are 0.2 mm or more in total and smaller than an outer diameter of the hollow body.   The tension member according to any one of claims 1 to 6, wherein the optical fiber is held coaxially with the hollow body.

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