Fixing structure

Abstract

To provide a fixation structure which can prevent sudden breakage of a cable.SOLUTION: A fixation structure 20 includes a rubber elastic body 22 and a body section 21 which is fixed to an end of a cable 10 through the rubber elastic body. The cable may be a fiber-reinforced plastic cable. The fiber-reinforced plastic cable may contain carbon fibers. The body section may be formed of the fiber-reinforced plastic. With these configurations, force applied between the body section and the cable is relaxed by deformation caused by a superelastic behavior of the rubber elastic body provided between the body section and the cable. Thus, sudden breakage can be prevented because tensile force hardly reaches an elastic limit in the cable provided with the fixation structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an anchoring structure for anchoring cables. [Background technology]

[0002] In recent years, extremely lightweight fiber reinforced plastic (FRP) cables have come to be used to support or reinforce structures such as bridges and buildings, while still having strength equal to or greater than that of metal cables (see, for example, Patent Document 1).

[0003] Both ends of an FRP cable are anchored to various structures, stable ground, etc. To enable the FRP cable to be anchored properly, an anchoring structure is provided at both ends of the FRP cable. The anchoring structure described in Patent Document 1 has an inclined portion to prevent tension applied to the FRP cable from concentrating locally. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6586695 Summary of the Invention [Problem to be solved by the invention]

[0005] Unlike metal cables, FRP cables exhibit linear deformation behavior, expanding in proportion to an increase in tension, which has the advantage of making them easier to design.However, FRP cables also have the disadvantage of being difficult to handle, as they suddenly change from linear deformation behavior to fracture when the elastic limit is reached due to an increase in tension.

[0006] In view of the above circumstances, an object of the present invention is to provide a fixing structure that can prevent sudden breakage of a cable. [Means for solving the problem]

[0007] In order to achieve the above object, an anchoring structure according to one aspect of the present invention includes a rubber elastic body and a main body portion fixed to an end portion of a cable via the rubber elastic body. The cable may be a fiber reinforced plastic cable. The fiber reinforced plastic cable may include carbon fiber. The main body may be made of fiber reinforced plastic.

[0008] In these configurations, the force applied between the main body and the cable is alleviated by deformation due to the superelastic behavior of the rubber elastic body provided between the main body and the cable. As a result, in a cable provided with an anchoring structure according to one embodiment of the present invention, the tension is less likely to reach its elastic limit, making it possible to prevent sudden breakage. [Effects of the Invention]

[0009] It is possible to provide a fixing structure that can prevent sudden breakage of the cable. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view showing a cable structure according to an embodiment of the present invention; [Figure 2] 2 is a cross-sectional view of the cable structure taken along line AA' in FIG. 1. [Figure 3] FIG. 10 is a front view of a modified example of the fixing structure of the cable structure. [Figure 4] FIG. 10 is a perspective view of a modified example of the cable of the cable structure. [Figure 5] FIG. 1 is a schematic diagram showing a method for a static tensile loading (unloading) test. [Figure 6] 1 is a graph showing the results of a static tensile load test for Example 1 and Comparative Example 1. [Figure 7] 1 is a graph showing the results of a static tensile load test for Example 1 and Comparative Example 1. [Figure 8]1 is a graph showing the results of a static tensile load-unload test for Example 1 and Comparative Example 1. [Figure 9] 1 is a graph showing the results of a static tensile load-unload test for Example 1 and Comparative Example 1. [Figure 10] 1 is a graph showing the results of a static tensile test for Example 2 and Comparative Example 2. [Figure 11] 1 is a graph showing the results of a static tensile test for Example 2 and Comparative Example 2. [Figure 12] 1 is a graph showing the results of a tensile-tensile fatigue test of Example 2 and Comparative Example 2. [Figure 13] 10 is a photograph showing a state in which the sample according to Comparative Example 2 is broken. [Figure 14] 10 is a photograph showing a state in which the sample according to Example 2 is broken. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Configuration of anchoring structure 20] (Schematic configuration) Fig. 1 is a front view of a cable structure 1 according to one embodiment of the present invention. The cable structure 1 includes a cable 10 and a fixing structure 20. The fixing structures 20 are provided at both longitudinal ends of the cable 10. Although Fig. 1 shows only one fixing structure 20, the other fixing structure 20 has a similar configuration.

[0012] In the cable structure 1, for example, one anchoring structure 20 is anchored to various structures such as bridges or buildings, and the other anchoring structure 20 is anchored to stable ground. This allows the cable structure 1 to support or reinforce the structure by the tension of the cables 10 connecting the structure and the stable ground.

[0013] (Cable 10) In the cable structure 1 according to this embodiment, an FRP cable made of fiber reinforced plastics (FRP) is used as the cable 10. By using an FRP cable as the cable 10, the cable structure 1 can achieve extremely light weight and high strength.

[0014] The resin components of FRP cables can be, for example, epoxy resin, vinyl ester resin, polyester resin, polyimide resin, polypropylene resin, polyamide resin, polycarbonate resin, etc. The fiber components of FRP cables can be, for example, carbon fiber, glass fiber, aramid fiber, boron fiber, etc.

[0015] The cable structure 1 uses rust-free FRP cables, making it particularly suitable for use in marine structures. Examples of marine structures for which the cable structure 1 can be used include tension leg platforms (TLPs) used in marine resource mining and offshore wind power generation.

[0016] The cable structure 1 is also useful for civil engineering applications such as tension cables for pre- and post-tensioned concrete used in viaducts and bridges, tension cables for ground anchors used to prevent the collapse of slopes and facets, etc. Furthermore, the cable structure 1 is also useful as a tension cable used to reinforce buildings.

[0017] FRP cables exhibit linear deformation behavior, stretching in proportion to an increase in tension, but suddenly break when they reach their elastic limit. This phenomenon is more pronounced in FRP cables that contain carbon fiber as a fiber component. The anchoring structure 20 according to this embodiment is configured to be able to suppress sudden breakage of the cable 10.

[0018] (Anchoring structure 20) Fig. 2 is a cross-sectional view of the cable structure 1 taken along line A-A' in Fig. 1. The fixing structure 20 has a main body 21 and a rubber elastic body 22. In the fixing structure 20, the inner circumferential surface of the cylindrical main body 21 is fixed to the end of the cable 10 via the rubber elastic body 22. In other words, the cable 10 and the main body 21 are bonded together by the rubber elastic body 22.

[0019] In the anchoring structure 20, the main body 21 is fixed to a structure, stable ground, etc. via a connecting member. The connecting member may be any member that can favorably connect the main body 21 to the structure, stable ground, etc. In the anchoring structure 20, for example, the outer peripheral surface of the main body 21 may be provided with a male thread so that it can be fixed to a connecting member that has a corresponding female thread member.

[0020] The material for forming the main body 21 can be selected from any structural material having high strength, but is preferably FRP. In the fixing structure 20, by forming both the cable 10 and the main body 21 from FRP, it is possible to realize a cable structure 1 that is very lightweight while ensuring high strength.

[0021] The FRP forming the main body 21 may use, as in the case of an FRP cable, for example, epoxy resin, vinyl ester resin, polyester resin, polyimide resin, polypropylene resin, polyamide resin, polycarbonate resin, etc. as the resin component, and carbon fiber, glass fiber, aramid fiber, boron fiber, etc. as the fiber component.

[0022] The rubber elastic body 22 is formed of a material that has rubber elasticity and exhibits superelastic deformation behavior due to the Mullins effect. Specifically, the material forming the rubber elastic body 22 preferably has an elastic modulus of 15 MPa to 500 MPa, a tensile strength of 5 MPa to 40 MPa, and a tensile elongation of 70% to 700%.

[0023] The material for forming the rubber elastic body 22 is not limited to rubber, as long as it has rubber elasticity. As an example, the rubber elastic body 22 can be formed using a polyurethane-based ductile adhesive. Examples of ductile adhesives suitable for forming the rubber elastic body 22 include BETAFORCE (registered trademark) 2850L (elastic modulus: 21 MPa, tensile strength: 10 MPa, tensile elongation: 150%) manufactured by The Dow Chemical Company and BETAFORCE (registered trademark) 9050 (elastic modulus: 300 MPa, tensile strength: 18 MPa, tensile elongation: 80%) manufactured by The Dow Chemical Company.

[0024] (Action of rubber elastic body 22) In the cable structure 1, a force applied between the main body 21 and the cable 10 acts on the rubber elastic body 22 sandwiched between the cable 10 and the main body 21. Therefore, in the cable structure 1, the cable 10 and the main body 21 do not directly exert force on each other, and the rubber elastic body 22 functions to transmit force between the cable 10 and the main body 21.

[0025] In the cable structure 1, the force applied between the cable 10 and the main body 21 is alleviated by deformation due to the superelastic behavior of the rubber elastic body 22. In the cable structure 1, when a further force is applied to the cable 10 in a state where a force is already applied to the cable 10, the force alleviation effect of the rubber elastic body 22 prevents a further increase in the tension of the cable 10.

[0026] In particular, the rubber elastic body 22, which has rubber elasticity and a nonlinear relationship between load and displacement, tends to deform more significantly as the applied force increases. Therefore, in the cable structure 1, the greater the force applied between the cable 10 and the main body 21, the greater the force-reducing effect of the rubber elastic body 22.

[0027] Therefore, in the cable structure 1, when a further force is applied to the cable 10 in a state where a large force is already applied to the cable 10, an increase in the tension of the cable 10 is particularly effectively suppressed. Therefore, in the cable structure 1, it is possible to prevent the cable 10 from reaching its elastic limit, and thus it is possible to prevent the cable 10 from suddenly breaking.

[0028] In the cable structure 1, the configuration such as the longitudinal dimension of the fixing structure 20 and the thickness of the rubber elastic body 22 can be determined depending on the application. For example, in an application in which a large force is applied between the cable 10 and the main body 21, the longitudinal dimension of the fixing structure 20 can be increased in order to increase the elastic limit of the rubber elastic body 22.

[0029] Furthermore, the greater the thickness of the rubber elastic body 22, the greater the ductility. Therefore, in the cable structure 1, the thickness of the rubber elastic body 22 can be determined depending on the magnitude of the force-relieving effect of the rubber elastic body 22 required for each application. However, making the rubber elastic body 22 excessively thick is not preferable because it reduces the strength of the rubber elastic body 22 itself.

[0030] (Other embodiments) The configuration of the cable structure 1 according to this embodiment can be modified as appropriate. For example, the shape of the main body 21 of the fixing structure 20 in the cable structure 1 can be modified in various ways. As an example, the cross-sectional shape of the main body 21 is not limited to the circular shape of the above embodiment, but can also be, for example, an elliptical shape, a rectangular shape, a polygonal shape, or the like.

[0031] 3, the main body 21 may have a fixed portion 21a and an inclined portion 21b. The fixed portion 21a is a cylindrical portion that is fixed to a connecting member. The inclined portion 21b is provided closer to the central region of the cable 10 than the fixed portion 21a and has a tapered shape that becomes thinner toward the central region of the cable 10.

[0032] 3, the rigidity of the inclined portion 21b provided in the main body 21 decreases toward the central region of the cable 10. Therefore, in this fixing structure 20, the holding force for holding the cable 10 at the inclined portion 21b is reduced, and breakage of the cable 10 near the inclined portion can be suppressed.

[0033] Furthermore, in the cable structure 1, the cable 10 does not have to be an FRP cable, and may be, for example, a metal cable made of metal. Even in this case, the cable structure 1 can prevent sudden breakage of the cable 10 due to the force-relieving effect of the rubber elastic body 22 of the fixing structure 20.

[0034] Additionally, in the cable structure 1, the cable 10 may be a rope formed by bundling a plurality of wires 10a as shown in Fig. 4(a). Also, in the cable structure 1, the cable 10 may be a rope formed by twisting a plurality of wires 10a in a bundled state as shown in Fig. 4(b).

[0035] [Example 1] (Experimental content) As Example 1 of the present invention, a sample of cable structure 1 was produced. Cable 10 was a composite tension rod manufactured by Komatsu Matere Co., Ltd., in which three 24,000 carbon fibers with a tensile modulus of 230 GPa were braided and covered with glass fiber (E-glass) and impregnated with thermoplastic epoxy resin (phenoxy).

[0036] To provide the anchoring structure 20, a rubber elastic body 22 was formed at the end of the cable 10, and an FRP sheet was wound around the rubber elastic body 22 to form the main body 21. A ductile adhesive having rubber elasticity (BETAFORCE (registered trademark) 2850L manufactured by The Dow Chemical Company) was used as the rubber elastic body 22.

[0037] A static tensile load test and a static tensile load-unload test were then carried out on the sample according to Example 1. An electric hydraulic servo tester (Servo Pulser EHF-E series manufactured by Shimadzu Corporation) was used as the static tensile load (unload) test device. The static tensile load (unload) test was carried out in a laboratory atmosphere at room temperature.

[0038] 5 is a schematic diagram for explaining a static tensile load (unload) test. In the static tensile load (unload) test, a pair of fixing structures 20 of the sample are clamped by fixing parts C1U and C1L, respectively. Fixing parts C1U and C1L are configured to use hydraulic chucks, which are less likely to cause misalignment with fixing structure 20 than a normal wedge-shaped chuck.

[0039] In the static tensile loading test, the sample was loaded by raising the upper fixing part C1U while the lower fixing part C1L was fixed. In the static tensile loading / unloading test, the sample was loaded and unloaded by repeatedly raising and lowering the upper fixing part C1U while the lower fixing part C1L was fixed.

[0040] In the static tensile load (unload) test, the strain-stress relationship can be obtained by plotting the strain ε and stress σ at the center of the cable 10. The strain ε and stress σ at the center of the cable 10 were measured using a strain gauge. The strain-stress relationship obtained in the static tensile load (unload) test makes it possible to understand the deformation behavior of the cable 10 alone.

[0041] Furthermore, in the static tensile load (unload) test, the load-displacement relationship can be obtained by plotting the load P applied to the fixing part C1U and the displacement U of the fixing part C1U. The load-displacement relationship obtained in the static tensile load (unload) test makes it possible to understand the overall deformation behavior of the cable 10 and anchoring structure 20 that make up the sample.

[0042] As Comparative Example 1 of the present invention, a sample of a cable structure was produced that did not include the rubber elastic body 22 and was composed only of the cable 10 and the main body 21. In the sample according to Comparative Example 1, the main body 21 was formed by winding an FRP sheet over a general adhesive without rubber elasticity that was applied to the cable 10. The sample according to Comparative Example 1 was also subjected to a static tensile load (unload) test similar to that described above.

[0043] (Evaluation results) 6 is a graph showing the strain-stress relationship obtained in the static tensile load test. Both the samples according to Example 1 and Comparative Example 1 show similar linear deformation behavior. This shows that the cables 10 used in the samples according to Example 1 and Comparative Example 1 both deform with similar linear behavior.

[0044] 7 is a graph showing the load-displacement relationship obtained in a static tensile load test. The sample according to Comparative Example 1 exhibits a linear load-displacement relationship, indicating linear deformation behavior. On the other hand, the sample according to Example 1 exhibits nonlinear deformation behavior, with the load-displacement relationship forming a curve whose slope decreases as the load increases.

[0045] The sample according to Comparative Example 1 is considered to exhibit linear deformation behavior because it is not affected by any components other than the cable 10. In contrast, the sample according to Example 1 is considered to exhibit nonlinear deformation behavior because, in addition to the deformation of the cable 10, the deformation of the rubber elastic body 22 having rubber elasticity also contributes.

[0046] This indicates that the load in the sample according to Example 1 is reduced by an amount corresponding to the increase in displacement due to the deformation of the rubber elastic body 22, compared to the sample according to Comparative Example 1. Therefore, it was confirmed that the provision of the rubber elastic body 22 in the cable structure 1 according to this embodiment provides a force reduction effect.

[0047] 8 is a graph showing the strain-stress relationship obtained in a static tensile loading / unloading test. Both the samples according to Example 1 and Comparative Example 1 exhibit similar linear deformation behavior during both the loading and unloading processes. This indicates that the cables 10 used in the samples according to Example 1 and Comparative Example 1 expand and contract in a linear manner.

[0048] 9 is a graph showing the load-displacement relationship obtained in a static tensile load-unloading test. In the sample of Comparative Example 1, the load-displacement relationship is nearly linear, which suggests that there is almost no influence from components other than the cable 10. In contrast, in the sample of Example 1, the load-displacement relationship forms a hysteresis curve.

[0049] More specifically, the load-displacement relationship of the sample according to Example 1 follows a curve similar to that shown in Fig. 7 during the loading stroke, and follows a curve that passes below the curve of the loading stroke and returns to the vicinity of the origin during the unloading stroke. This indicates that in the sample according to Example 1, when the load becomes zero after the unloading stroke, the rubber elastic body 22 returns to its original shape.

[0050] Therefore, in the rubber elastic body 22 of the cable structure 1 according to this embodiment, even if a force is repeatedly applied between the cable 10 and the main body 21, no permanent set occurs and the force relaxation effect is maintained well. Therefore, the cable structure 1 according to this embodiment can prevent sudden breakage of the cable 10 for a long period of time.

[0051] [Example 2] (overview) To anchor cables, an anchoring structure consisting of a main body made of a steel pipe and an expansion agent placed between the main body and the cable is sometimes used. When such an anchoring structure is used to anchor FRP cables, the compressive load caused by the expansion of the expansion agent tends to cause longitudinal cracks in the FRP cables along the axial direction.

[0052] In this regard, by using the fixing structure 20 of the present invention in which the rubber elastic body 22 is provided inside the expansion agent, it is possible to prevent the breakage of the FRP cable due to the influence of the expansion of the expansion agent as described above. In Example 2 of the present invention, the performance of the cable structure 1 using the fixing structure 20 of such a configuration was verified.

[0053] (Experimental content) In Example 2 of the present invention, a sample of cable structure 1 was produced using an FRP cable made of basalt fiber and polypropylene resin as cable 10, a steel pipe and an expansion agent (static crushing agent Blaster: manufactured by Pacific Materials) as main body 21, and a ductile adhesive (BETAFORCE (registered trademark) 2850L manufactured by Dow Chemical Company) as rubber elastic body 22.

[0054] First, the sample according to Example 2 was subjected to a static tensile test similar to that of Example 1. Next, a tensile-tensile fatigue test was performed on the sample according to Example 2 using the same testing machine as that used for the static tensile test, with load control, a repetition frequency of 10 Hz, a repetition waveform of a sine wave, and a cutoff repetition number of 10 7 The test was carried out under the condition that the stress ratio (minimum stress / maximum stress) R was 0.1.

[0055] As Comparative Example 2 of the present invention, a sample of a cable structure was prepared in which the rubber elastic body 22 was not provided in the sample of Example 2. That is, in the sample of Comparative Example 2, the expansion agent was adhered to the cable 10 via a general adhesive that does not have rubber elasticity. The sample of Comparative Example 2 was also subjected to the same static tensile test and tensile-tensile fatigue test as described above.

[0056] (Evaluation results) 10 is a graph showing the strain-stress relationship obtained in the static tensile test. Both the samples according to Example 2 and Comparative Example 2 show similar linear deformation behavior. This shows that the cables 10 used in the samples according to Example 2 and Comparative Example 2 both deform with similar linear behavior.

[0057] 11 is a graph showing the load-displacement relationship obtained in a static tensile test. The sample according to Comparative Example 2 exhibits slightly nonlinear behavior. In contrast, the sample according to Example 2 exhibits similar behavior to Comparative Example 2 in the range of loads P up to 5 kN, and exhibits more nonlinear behavior than Comparative Example 2 in the range of loads P greater than this.

[0058] 12 is a graph showing the relationship between the maximum stress and the number of cycles until fracture obtained in the tensile-tensile fatigue test. In the sample of Example 2, the number of cycles until fracture at a maximum stress of 0.28 GPa was six times or more that of the sample of Comparative Example 2, and the number of cycles until fracture at a maximum stress of 0.14 GPa was 10 times or more. 7 It did not break until it reached 100 times.

[0059] 13 shows the broken state of the sample according to Comparative Example 2. It can be seen that in the sample according to Comparative Example 2, the cable 10 broke in the portion covered by the fixing structure. From this result, it is considered that in the sample according to Comparative Example 2, the cable 10 became more prone to breakage due to the influence of the expansion of the expansion agent.

[0060] 14 shows the broken state of the sample according to Example 2. It can be seen that in the sample according to Example 1, the cable 10 broke in the center away from the fixing structure 20. From this result, it can be seen that in the sample according to Example 2, the cable 10 is less affected by the expansion of the expansion agent, and therefore the original performance of the cable 10 is obtained. [Explanation of symbols]

[0061] 1...Cable structure 10...Cable 20...Anchoring structure 21...Main body 22...Rubber elastic body

Claims

1. A rubber elastic body; a main body portion fixed to an end portion of a cable via the rubber elastic body; An anchoring structure comprising:

2. The anchoring structure of claim 1 , The cable is a fiber-reinforced plastic cable. Fixed structure.

3. The anchoring structure according to claim 2, The fiber-reinforced plastic cable contains carbon fiber. Fixed structure.

4. The fixing structure according to any one of claims 1 to 3, The main body is made of fiber-reinforced plastic. Fixed structure.

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