carbon fiber composite cable for prestressing and method for introducing prestressing

Abstract

This invention provides a carbon fiber composite cable with an uneven surface that can resist post-tension type prestress through adhesive force, and a method for introducing prestress. [Solution] In a carbon fiber composite cable 1 for prestressing, a core wire 2 made of composite wire 20 made of a composite material of carbon fiber and matrix resin is twisted around a side wire 2' made of composite wire 20, and the tension force that applies prestress to a concrete member is transmitted by the adhesive force with the surrounding cement-based material. In this cable, a resin yarn 3 made of twisted resin fibers is wound around each composite wire 20, and the side wires 2' made of composite wire 20 with the resin yarn 3 wound around the core wire 2 made of composite wire 20 are further twisted around the core wire 2 made of composite wire 20 with the resin yarn 3 wound around it to form surface irregularities that come into contact with the cement-based material.

Description

[Technical Field]

[0001] The present invention relates to a carbon fiber composite cable and a method for introducing prestress, and more particularly to a carbon fiber composite cable for prestressing having a surface irregularity that can withstand the tension of prestress due to its adhesive force, and a method for introducing prestress using the same. [Background technology]

[0002] In recent years, continuous reinforcing fiber materials, which are corrosion-resistant, high-strength, highly elastic, and heat-resistant, have been used as a substitute for steel reinforcement. These continuous reinforcing fiber materials include composite materials that combine carbon fibers, aramid fibers, glass fibers, epoxy resins, vinyl ester resins, and other materials.

[0003] Furthermore, the applicant has developed a two-directional PCaPC slab (MeL slab®) in which prestress is introduced using carbon fiber composite cable (CFCC: registered trademark) as a tensioning member in two directions: the span direction and the bridge axis direction. Such a two-directional PCaPC slab using carbon fiber composite cable is precast, and the carbon fiber composite cable perpendicular to the bridge axis is installed during factory fabrication, and the slab is transported to the site and erected with prestress already introduced.

[0004] After being erected on site, the two-way precast concrete (PCaPC) slab using carbon fiber composite cables is positioned through duct holes provided in the concrete slab, with the carbon fiber composite cables in the bridge axis direction being tensioned and held in place. Subsequently, grout is filled between the duct and the carbon fiber composite cables, and after the grout has reached a predetermined strength, prestress is introduced using a torque wrench method described in Patent No. 7201867, developed by the applicant. At this time, the tension applied to the carbon fiber composite cables introduces prestress into the concrete through adhesion between the grout and the carbon fiber composite cables.

[0005] The aforementioned torque wrench method proposes that by controlling the compressive strength of the grout and the rate at which the tension is released, the anchoring length due to adhesion of typical PC steel materials can satisfy 65φ (65 times the cable diameter). This enables stable prestressing anchoring through the adhesion of carbon fiber composite cables. However, when the tension applied to the carbon fiber composite cable becomes large, there were cases where the adhesion force with the grout was insufficient.

[0006] For example, when using a carbon fiber composite cable with a diameter of 19.3 mm, even when applying a torque wrench method, there were instances where the anchoring length did not satisfy 65 mm in diameter. Therefore, when anchoring by the adhesion of carbon fiber composite cables to grout, there are limitations on the applicable diameter. From the perspective of introducing prestress to two-way PCaPC slabs using carbon fiber composite cables, it becomes necessary to place a large number of small-diameter carbon fiber composite cables, and there is a problem in that the target prestress cannot be secured due to the placement limitations.

[0007] Furthermore, while we have confirmed that a stable anchoring length of 65φ can be provided with small-diameter carbon fiber composite cables, improving the adhesion force is required to further ensure the stability of that anchoring length. In other words, it is necessary to improve the adhesion force of carbon fiber composite cables so that a stable anchoring length can be ensured even with large-diameter carbon fiber composite cables.

[0008] On the other hand, several inventions have been proposed to improve adhesion by imparting an uneven shape to carbon fiber composite cables. For example, Patent Document 1 discloses a concrete reinforcing bar having an uneven surface, proposed by the present applicant, which has a twisted wire structure in which multiple threads are twisted together, and is loosely twisted so as to deform into an outwardly convex semi-elliptical shape when viewed from a cross-section when wrapped around the outer surface of a resin-impregnated fiber bundle (see Claim 1 of the claims in Patent Document 1, paragraphs

[0020] to

[0035] of the specification, and Figures 1 to 10 of the drawings, etc.).

[0009] Furthermore, Patent Document 2 discloses concrete reinforcing fibers having irregularities with a height of 0.1 to 0.5 mm formed on their surface (see Claim 6 of the claims in Patent Document 2, paragraph

[0017] of the specification, etc.).

[0010] However, the concrete reinforcing bars with irregularities described in Patent Document 1 and the concrete reinforcing fibers described in Patent Document 2, unlike the aforementioned carbon fiber composite cables, were not designed to introduce tension into the concrete through adhesion with grout when prestress is applied in a post-tensioning manner. As a result, they could not withstand the tension when prestressing is applied solely through adhesion with grout. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Patent No. 7335924 [Patent Document 2] Japanese Patent Publication No. 2002-137942 [Overview of the project] [Problems that the invention aims to solve]

[0012] Therefore, the present invention was devised in view of the aforementioned problems, and its objective is to provide a carbon fiber composite cable for prestressing having surface irregularities that can resist prestressing with adhesive force, and a method for introducing prestress. [Means for solving the problem]

[0013] The carbon fiber composite cable for prestressing according to the first invention is formed by twisting side wires made of composite wires, which are made of composite wires made of carbon fibers and matrix resin, around a core wire, and transmits the tension force that applies prestress to a concrete member by the adhesive force with the surrounding cement-based material, wherein resin yarn made of twisted resin fibers is wound around each composite wire, and surface irregularities are formed by further twisting the side wires made of composite wires, which are made of composite wires, around the core wire made of composite wires, which are made of composite wires, around which the resin yarn is wound.

[0014] The carbon fiber composite cable for prestressing according to the second invention is characterized in that, in the first invention, the surface irregularities have an irregularity height of 0.16 mm or more and 0.21 mm or less.

[0015] The carbon fiber composite cable for prestressing according to the third invention is characterized in that, in the second invention, the surface irregularities have a spacing between irregularities of 2.5 mm or more and 5.0 mm or less.

[0016] The carbon fiber composite cable for prestressing according to the fourth invention is characterized in that, in the second invention, the surface irregularities have an irregularity difference of 0.11 mm or more and 0.16 mm or less.

[0017] The carbon fiber composite cable for prestressing according to the fifth invention is characterized in that, in the second invention, the resin yarn is a PET yarn in which PET fibers are twisted together.

[0018] The sixth invention relates to a prestress introduction method, which introduces prestress by transmitting the tension force applied to a tensioning material to a concrete member via the adhesive force with the surrounding cement-based material, wherein the tensioning material is a carbon fiber composite cable for prestressing as described in any one of claims 1 to 5.

[0019] The seventh invention is characterized in that, in the sixth invention, the tensile force applied to the tension member is statically transmitted and introduced into the concrete member by using a torque wrench.

[0020] The eighth invention is characterized in that, in the sixth invention, the tensile force applied to the tension member is dynamically transmitted and introduced into the concrete member by cutting the tension member.

[0021] The ninth invention is a post-tensioning prestress introduction method in the seventh invention, in which a sheath is provided in the concrete member, the tension member is inserted into the sheath, grout, which is the cementitious material, is injected into the sheath, and after the grout has hardened, the tensile force is introduced into the concrete member through the grout, and the compressive strength of the grout is 30 N / mm , ,

[0023] , , , 2 , , , It is characterized in that prestress is introduced after reaching the above.

[0022] The tenth invention is a pretensioning prestress introduction method in the seventh invention, in which the tensile force is introduced into the concrete member through the adhesion force with the surrounding cementitious material, and the compressive strength of the cementitious material is 36 N / mm 2 It is characterized in that prestress is introduced after reaching the above.

Advantages of the Invention

[0023] According to the first to ninth inventions, it is possible to provide a prestressed carbon fiber composite cable having surface irregularities capable of countering the target prestress with adhesion force and a prestress introduction method. Further, according to the first to ninth inventions, in a two-way PCaPC floor slab in which prestress is introduced using carbon fiber composite cables as tension members in two directions, the floor slab support span direction and the bridge axis direction, a large number of thin-diameter carbon fiber composite cables have to be arranged, and the problem that the target prestress cannot be ensured due to the arrangement limit is solved, the adhesion force of the carbon fiber composite cable is improved, and a stable fixing length can be ensured even for a thick-diameter carbon fiber composite cable.

Brief Description of the Drawings

[0024] [Figure 1] Figure 1 is a cross-sectional view of a carbon fiber composite cable for prestressing according to an embodiment of the present invention. [Figure 2] Figure 2 is a schematic perspective view showing a composite wire with resin threads wound around it. [Figure 3] Figure 3 is a longitudinal cross-sectional view showing the composite wire material with resin threads wound around it. [Figure 4] Figure 4(a) is a front view of the carbon fiber composite cable shown above, viewed in a direction perpendicular to the cable's axial direction, and Figure 4(b) is a cross-sectional view of a conventional carbon fiber composite cable without irregularities, consisting of composite wire without resin threads wound around it. [Figure 5] Figure 5 shows an overview of the specimen used in the experiment to verify the effect of the uneven surface. [Figure 6] Figure 6 shows the positions of the gauges installed on the side of the test specimen. [Figure 7] Figure 7 is a photograph showing the state of specimen No. 2 after prestressing, with (a) showing the longitudinal end face and (b) showing the side view. [Figure 8] Figure 8 is a photograph showing the condition of the longitudinal end face of specimen No. 3 after prestressing. [Figure 9] Figure 9 is a graph showing the results for the anchorage length of specimen No. 1. [Figure 10] Figure 10 is a graph showing the results for the anchorage length of specimen No. 2. [Figure 11] Figure 11 is a graph showing the results for the anchorage length of specimen No. 3. [Figure 12] Figure 12 is a graph showing the results of the anchorage length when splitting cracks occurred in No. 3. [Figure 13] Figure 13 shows an overview of the specimen used in the adhesion strength evaluation test. [Figure 14] Figure 14 shows an overview of the adhesion strength evaluation test. [Figure 15]Figure 15 shows an overview of the specimen used in the anchorage length evaluation test. [Figure 16] Figure 16 is a graph showing the results of the anchorage length evaluation test for Type C and Type D specimens with uneven surfaces. [Figure 17] Figure 17 is a graph showing the results of an evaluation test of the anchorage length of a specimen without irregularities. [Modes for carrying out the invention]

[0025] Hereinafter, one embodiment of the carbon fiber composite cable for prestressing and the prestressing method according to the present invention will be described in detail with reference to the drawings.

[0026] [Prestressed carbon fiber composite cable] Figures 1 to 4 illustrate the carbon fiber composite cable 1 for prestressing according to an embodiment of the present invention. Figure 1 is a cross-sectional view of the carbon fiber composite cable 1 for prestressing according to an embodiment of the present invention. Figure 2 is a schematic perspective view showing the state in which resin yarn is wound around a composite wire, and Figure 3 is a longitudinal cross-sectional view showing the state in which resin yarn is wound around a composite wire. Figure 4(a) is a front view of the carbon fiber composite cable 1 for prestressing according to this embodiment, viewed in a direction perpendicular to the axial direction of the cable, and Figure 4(b) is a cross-sectional view of a smooth carbon fiber composite cable 1' consisting of a composite wire without resin yarn winding.

[0027] As shown in Figure 1, the carbon fiber composite cable 1 for prestressing according to this embodiment is a large-diameter cable with a diameter of approximately 17.2 mm (or 19.3 mm), consisting of 7 strands of twisted material, with 6 side wires 2' twisted around a single core wire 2. Furthermore, unlike the concrete reinforcement bars with irregularities described in Patent Document 1, the carbon fiber composite cable 1 for prestressing has a compressive strength of 30 N / mm² for concrete slabs and the like. 2This is a prestressing tensioning member for applying prestress to the above-mentioned concrete members, and it is a member that transmits the tensioning force acting on the tensioning member through the adhesion force between the concrete member and the surrounding cement-based material (concrete or grout). On the other hand, the tensile strength of the concrete reinforcing bar with irregularities described in Patent Document 1 is 1770 N / mm². 2 To that extent, the carbon fiber composite cable 1 for prestressing has a load capacity of 2550 N / mm². 2 It is a material of high strength and durability. This prestressing carbon fiber composite cable 1 is intended to be used as a tensioning member for pretensioning in the span direction of the aforementioned two-way PCaPC deck slab (MeL slab: registered trademark) or as a tensioning member for post-tensioning in the bridge axis direction.

[0028] As shown in Figures 2 and 3, both the core wire 2 and the side wire 2' are made of composite wire 20, which is a composite of carbon fiber and matrix resin. The composite wire 20 has resin thread 3 wound around its outer surface by a wrapping machine or the like, forming spiral irregularities at a predetermined angle. In the prestressed carbon fiber composite cable 1, composite wire 20 with resin thread 3 wound around the core wire 2, as well as the side wire 2' that comes into contact with the cement-based material, is used. Displacement evaluation tests, described later, showed that while the cement-based material and the side wire are fixed by adhesion, the side wire and core wire also exhibit a similar tendency to slide. At this time, if both have an irregular shape, they are mechanically fixed, shortening the fixing length and reducing the amount of displacement.

[0029] This composite wire 20 is a resin-impregnated fiber bundle made of carbon fiber reinforced plastic, in which numerous carbon fiber filaments, which are continuous fibers with a diameter of 5 to 7 μm, are impregnated with a matrix resin made of a thermosetting resin or thermoplastic resin and bundled together in a circular cross-section.

[0030] Furthermore, the resin yarn 3 according to this embodiment is a PET yarn (polyethylene terephthalate yarn) made by twisting together multiple (for example, about 20) PET fibers (polyethylene terephthalate fibers). Of course, the resin yarn according to the present invention is not limited to PET yarn made of PET fibers, but resin yarn made of other resin fibers can also be applied. In addition, the PET fibers in this resin yarn 3 are not tightly twisted together, but are twisted relatively loosely, and since the matrix resin of the composite wire 20 is wrapped around the outer surface of the composite wire 20 by a wrapping machine or the like while the composite wire 20 is still uncured, as shown in Figure 3, the cross-section of the wrapped resin yarn 3 deforms from a circular to a semicircular shape, and the core wire 2 and side wires 2' form semicircular protrusions around each composite wire 20 at a predetermined pitch. However, the protrusions applied to the core wire have a spacing of 2.52 mm between protrusions and a height of 0.16 mm between protrusions.

[0031] Furthermore, as shown in Figure 4(a), a side wire 2' made of composite wire 20 with resin thread 3 wound around it is further twisted around a core wire 2 made of composite wire 20 with resin thread 3 wound around it, thereby forming surface irregularities consisting of convex portions 1a and concave portions 1b on the surface that comes into contact with the cement-based material.

[0032] As shown in Figure 4(a), the surface irregularities have an irregularity spacing P1 of 2.0 mm or more and 5.0 mm or less, and from experiments described later, an irregularity spacing P1 of 2.5 mm or more and 3.0 mm or less is preferred. Furthermore, the irregularity spacing P1 of Type C described later, with a spacing P1 of 2.5 mm (2.52 mm), is the most preferred. Here, the irregularity spacing P1 is a representative value (average value) of the longitudinal distance between adjacent protrusions 1a or recesses 1b.

[0033] Furthermore, the difference in surface irregularities T1 is between 0.11 mm and 0.21 mm, and from experiments described later, a difference in surface irregularities T1 of 0.11 mm or more and 0.16 mm or less is preferred. Here, the difference in surface irregularities T1 is a representative value (average value) of the height difference between adjacent protrusions 1a and recesses 1b.

[0034] The height H1 of the surface irregularities is defined as the representative value of the difference between the outermost position of the protrusion 1a shown in Figure 4(a) of the prestressed carbon fiber composite cable 1 with surface irregularities shown in Figure 1 and the outermost position of the protrusion 1a shown in Figure 4(a) of the prestressed carbon fiber composite cable 1 with surface irregularities shown in Figure 4(b). That is, if the diameter of the prestressed carbon fiber composite cable 1 with surface irregularities is D1 and the diameter of the carbon fiber composite cable 1' without irregularities is D2, then the height of the protrusion H1 is defined as 1 / 2(D1-D2). In this case, the height of the protrusion H1 is 0.16 mm or more and 0.21 mm or less, and the most preferable is the irregularity height H1 = 0.16 mm for Type C, which will be described later.

[0035] As mentioned above, the carbon fiber composite cable 1 for prestressing is intended to be used as a tensioning member for pretensioning in the span direction of the two-way PCaPC deck slab or as a tensioning member for post-tensioning in the bridge axis direction. Therefore, the design standard strength when used as a tensioning member for pretensioning is 36 N / mm², which is different from the cement-based material mentioned above. 2 The design strength when used as concrete, short-fiber reinforced concrete, or tensioning material for post-tensioning is 30 N / mm². 2 The above concrete and short-fiber reinforced concrete have a load capacity of 30 N / mm². 2 We are assuming grout of the above strength.

[0036] [Methods for introducing prestress] Next, a prestress introduction method according to an embodiment of the present invention will be described. The prestress introduction method according to this embodiment is a post-tension type prestress introduction method that uses the aforementioned prestress carbon fiber composite cable 1, which is a tensioning material, to transmit the tension applied to the prestress carbon fiber composite cable 1 to the aforementioned two-way PCaPC slab or other concrete member via the adhesive force with the surrounding cement-based material, thereby introducing prestress.

[0037] Specifically, in the prestress introduction method according to this embodiment, as described in Japanese Patent No. 7201867 proposed by the applicants of the present application, a tendon insertion step is performed in which a prestressed carbon fiber composite material cable 1 is inserted into a sheath such as a PE sheath provided in a concrete member such as a two-way PCaPC floor slab.

[0038] Next, a tendon tensioning step is performed in which the prestressed carbon fiber composite material cable 1 inserted in the tendon insertion step is tensioned by a tensioning jack to apply a predetermined target tension.

[0039] Thereafter, a grout material filling step is performed in which a grout such as an ultra-low viscosity type grout, which is a cement-based material, is filled into the sheath tensioned in the tendon tensioning step.

[0040] Thereafter, after confirming that the compressive strength of the grout filled in the grout material filling step is 30 N / mm 2 or more, which is equivalent to concrete or short fiber reinforced concrete of 30 N / mm 2 or more, a tension release step is performed to release the tension of the prestressed carbon fiber composite material cable 1 tensioned in the tendon tensioning step.

[0041] In this tension release step, the tension applied to the prestressed carbon fiber composite material cable 1 is statically released using a torque wrench, and prestress is introduced into a concrete member such as a two-way PCaPC floor slab.

[0042] Specifically, in this tension release step, prestress is gradually introduced into the concrete member while controlling the tension release speed of the prestressed carbon fiber composite material cable using a hydraulic torque wrench.

[0043] In this tension release step, the prestressed carbon fiber composite material cable 1 may be cut and dynamically transmitted to the concrete member to introduce prestress. As described above, the prestressed carbon fiber composite material cable 1 has a convex portion height H1 of 0.16 mm or more and 0.21 mm or less, and thus has a high adhesive force.

[0044] According to the carbon fiber composite cable 1 for prestressing and the prestress introduction method according to the present embodiment described above, it is possible to provide a carbon fiber composite cable 1 for prestressing and a prestress introduction method having surface irregularities that can resist the target prestress with adhesive force.

[0045] Furthermore, the carbon fiber composite cable 1 for prestressing and the prestress introduction method according to this embodiment solve the problem that in a two-directional PCaPC slab where prestress is introduced using carbon fiber composite cables as tensioning members in two directions, the slab span direction and the bridge axis direction, a large number of small-diameter carbon fiber composite cables must be arranged, making it impossible to secure the target prestress due to arrangement limitations. This improves the adhesion force of the carbon fiber composite cables, making it possible to secure a stable anchorage length even with large-diameter carbon fiber composite cables.

[0046] [Experiment to verify the effect of uneven surfaces] Next, we will describe the effect verification experiment conducted to confirm the effect of the uneven shape of the core and side wires of the present invention. Figure 5 is a diagram showing the outline of the test specimen used in the effect verification experiment of the uneven shape, and Figure 6 is a diagram showing the position of the gauge installed on the side of the test specimen. Using the test specimen shown in Figure 5, we evaluated the grout adhesion and anchoring of a φ17.2 mm carbon fiber composite cable (CFCC). The level of the carbon fiber composite cable used is shown in Table 1. Uneven shapes were applied to the core wire and side wire to understand the effect of the presence or absence of the uneven shape on the anchoring length. The spacing of the unevenness applied to the core wire at this time was 2.52 mm, and the height of the protrusions was 0.16 mm (hereinafter referred to as Type A for the uneven specification).

[0047] The prestress was 0.7σ pu (269.5 kN), and the concrete strength at the time of prestressing was 54.2 N / mm². 2 The compressive strength of the grout is 57.2 N / mm². 2The anchorage length was evaluated by embedding surface gauges and mold gauges installed on the side of the concrete specimen, as shown in Figure 6. Prestress was introduced by cutting. The anchorage length was evaluated using surface strain gauges installed on the side of the specimen, and the ratio of strain before and after introduction was evaluated as the prestress effectiveness rate.

[0048] [Table 1]

[0049] Figure 7 is a photograph showing the state of specimen No. 2 after prestressing, with (a) showing the longitudinal end face and (b) showing the side view. Figure 8 is a photograph showing the state of the longitudinal end face of specimen No. 3 after prestressing. As shown in the photograph in Figure 7(a), splitting cracks occurred in a portion of specimen No. 2 when the exposed carbon fiber composite cable on the fixed end side was cut and inserted. Also, as shown in Figure 8, splitting cracks occurred in a portion of specimen No. 3 when the carbon fiber composite cable on the tensioned end side was cut and inserted.

[0050] Therefore, the uneven shape of the carbon fiber composite cable used in this study resulted in excessive circumferential tensile stress due to the adhesion and bearing effect caused by the uneven surface, leading to cracking in the concrete. Thus, it is clear that a stable anchorage length cannot be provided. The results of the anchorage lengths for specimens that did not develop cracks after the introduction of prestress are shown in Figure 9 for No. 1, Figure 10 for No. 2, and Figure 11 for No. 3. In addition, the results of the anchorage length when splitting cracks occurred in No. 3 are shown in Figure 12.

[0051] The results showed that in No. 1, which did not have any irregularities, the range where the effective prestress was 95% or more (anchorage length) was 114φ. In contrast, in No. 2 and No. 3, the anchorage lengths were 42φ and 43φ, respectively, clearly indicating a shorter anchorage length. This means that the adhesion to the grout improved due to the addition of the irregular shape. However, as mentioned above, if splitting cracks occur in the concrete specimen, the anchorage length increases, as shown in Figure 12. Therefore, it can be seen that a stable anchorage length cannot be ensured with high adhesion that causes cracking in the concrete.

[0052] [Displacement evaluation test] Next, we conducted tests to evaluate the displacement of the exposed carbon fiber composite cable before and after cutting. Table 2 shows the results at a level where no cracks occurred. As shown in Table 2, the largest displacement was observed in No. 1, where there were no irregularities, confirming that mechanical anchoring was achieved by the presence of the irregularities. Furthermore, comparing the effects of the core wire and side wire at the level with added irregularities, the displacement of the core wire was smaller in No. 3 than in No. 2, indicating that No. 3 had higher mechanical anchoring performance. This is because, although the grout and side wire are anchored by adhesion, the side wire and core wire also exhibit a similar tendency to slide, and at this time, if both have an irregular shape, they are mechanically fixed. Therefore, it was found that by adding an irregular shape to the side wire and core wire, the anchoring length can be shortened and the amount of displacement can be reduced.

[0053] [Table 2]

[0054] [Evaluation test of adhesion strength] Next, tests were conducted to evaluate the adhesion stress of carbon fiber composite cables with uneven surfaces added to the side wires and core wires, by varying the spacing of the uneven surfaces, the difference in unevenness, and the height of the protrusions in four different ways. Table 3 shows the test levels for each specimen, with the spacing of the uneven surfaces and the height of the protrusions being measured values. For comparison, a specimen without an uneven surface was also prepared. As for the uneven surface specifications, Type A is the level shown in the experiment to confirm the effect of the uneven surface; Type B is a level in which the spacing of the uneven surfaces is narrower and the difference in unevenness is smaller than that of Type A, but the height of the protrusions themselves is unchanged; Type C is a level in which the spacing of the uneven surfaces is the same as that of Type A and the difference in unevenness is smaller than that of Type B, but the height of the protrusions is lower than that of Type B; and Type D is a level in which the spacing of the uneven surfaces is smaller than that of Type A and the difference in unevenness is smaller than that of Type B, and the height of the protrusions is lower.

[0055] [Table 3]

[0056] Here, the spacing between protrusions and recesses is a representative value of the longitudinal spacing between adjacent protrusions or recesses in the carbon fiber composite cable, and the difference between protrusions and recesses is a representative value of the difference in height between adjacent protrusions and recesses. Furthermore, the protrusion height refers to a representative value of the difference between the outermost position of a protrusion and the outermost position of the base carbon fiber composite cable in the absence of protrusions and recesses.

[0057] Figure 13 shows an overview of the specimen used in the adhesion strength evaluation test, and Figure 14 shows an overview of the test used in the adhesion strength evaluation test. As shown in Figure 13, the specimen consisted of a concrete block with a φ17.2 mm carbon fiber composite cable placed on it, and a PE (polyethylene) sheath and grout were also incorporated to replicate the post-tension type. The anchoring length of the test was one strand pitch (approximately 14φ). Furthermore, as can be seen from the measurement diagram shown in Figure 14, the pull-out load was determined using a load cell, and the amount of pull-out at the anchoring point was determined by installing a displacement meter at the end of the carbon fiber composite cable.

[0058] The maximum adhesion stress is shown in Table 4 as a test result. From the results, the adhesion stress in the case of no irregularities is 9.7 N / mm².2 The results were as follows. In contrast, all levels with an uneven surface significantly exceeded the results. Among these, splitting cracks occurred in Type A and Type B, where the height of the protrusions was set high, while splitting cracks did not occur in Type C and Type D, where the height of the protrusions was set low. Therefore, while setting the height of the protrusions increases the adhesion force, it also increases the splitting tensile force, resulting in deformation of the base concrete. This is the same trend of splitting cracks shown in the experiment to confirm the effect of the uneven surface. As a result, among the levels with low protrusion heights, Type C showed superiority with a high degree of adhesion stress. Type D had a small difference in unevenness, which represents a result of a smaller mechanical anchoring mechanism.

[0059] [Table 4]

[0060] [Evaluation test for retention] Based on the results of the aforementioned adhesion strength evaluation test, Type C or Type D showed good performance as an uneven surface specification. Therefore, a test was conducted to evaluate the anchorage length using both levels. Figure 15 shows an overview of the specimen used in the anchorage length evaluation test. As shown in Figure 15, the specimen was made of short-fiber reinforced concrete with a height of 220 mm, a width of 210 mm, and a length of 2500 mm. A PE sheath of φ45 was placed in the center of the cross-section, and a φ19.3 mm carbon fiber composite cable was installed and integrated with ultra-low viscosity grout. The tension force applied to the carbon fiber composite cable was 0.7σu (332.8 kN), and the concrete strength at the time of introduction was 75.1 N / mm². 2 The grout strength is 72.6 N / mm². 2 The anchorage length was evaluated using surface strain gauges installed on the side of the specimen, and the ratio of strain before and after introduction was evaluated as the prestress effectiveness rate.

[0061] Table 5 shows the test levels. Two types of surface textures, Type C and Type D, were prepared, and a level without any surface texture was provided for comparison. The introduction methods were cutting and torque wrench.

[0062] [Table 5]

[0063] Figure 16 is a graph showing the results of the anchorage length evaluation test for Type C and Type D specimens with uneven surfaces, and Figure 17 is a graph showing the results of the anchorage length evaluation test for Case 5 specimens without uneven surfaces. As can be seen from Figures 16 and 17, at the level without uneven surfaces, the range where the effective prestress is 95% or more (anchor length) is greater than 65φ. Therefore, this means that the adhesion force is insufficient for the anchorage force due to prestress. Next, at the level with uneven surfaces, at Type D, the anchorage length was 65φ when cut and 85φ when using a torque wrench, while at Type C, the anchorage length was 45φ when cut and 33φ when using a torque wrench, indicating that the uneven Type C specimens have a more stable anchorage length. This is a result of the stable tension force at Type C, which has a high adhesion stress as shown in the adhesion force evaluation test, introducing prestress to the concrete member through grout adhesion. No splitting cracks occurred in any of the specimens.

[0064] From the above, it was found that the method of introducing prestress by grout adhesion using carbon fiber composite cables is advantageous when an uneven surface is applied, and furthermore, the degree of unevenness is advantageous when it is Type C.

[0065] Although the carbon fiber composite cable 1 for prestressing and the prestress introduction method using the same according to this embodiment of the present invention have been described in detail above, the embodiments described above or illustrated are merely examples of embodiments that have been materialized in carrying out the present invention. Therefore, the technical scope of the present invention should not be interpreted as being limited by these embodiments. [Explanation of symbols]

[0066] 1: Prestressed carbon fiber composite cable 1': Smooth carbon fiber composite cable 1a: Convex part 1b: recess 2: Core wire 2': Siding 20: Composite wire rod 3: Resin thread P1: Irregularity interval T1: Difference in unevenness H1: Height of unevenness D1: Diameter of carbon fiber composite cable for prestressing D2: Diameter of a carbon fiber composite cable with no irregularities.

Claims

1. A carbon fiber composite cable for prestressing is formed by twisting side wires made of the composite material around a core wire made of a composite material wire made of carbon fiber and matrix resin, and transmitting the tension force that applies prestress to a concrete member through the adhesive force with the surrounding cement-based material, Each of the composite wires has a resin yarn made of twisted resin fibers wound around it, and the side wires made of the composite wires with the resin yarn wound around them are further twisted around the core wire made of the composite wires with the resin yarn wound around them, thereby forming surface irregularities that come into contact with the cement-based material. A carbon fiber composite cable for prestressing, featuring the following characteristics.

2. The surface irregularities have an irregularity height of 0.16 mm or more and 0.21 mm or less. A carbon fiber composite cable for prestressing according to claim 1, characterized by the above.

3. The aforementioned surface irregularities have a spacing of 2.5 mm or more and 5.0 mm or less between the irregularities. A carbon fiber composite cable for prestressing according to claim 2, characterized by the above.

4. The surface irregularities have a difference of 0.11 mm or more and 0.16 mm or less. A carbon fiber composite cable for prestressing according to claim 2, characterized by the above.

5. The aforementioned resin yarn is a PET yarn in which PET fibers are twisted together. A carbon fiber composite cable for prestressing according to claim 2, characterized by the above.

6. A prestress introduction method that introduces prestress by transmitting the tension force applied to a tensioning material to a concrete member via the adhesive force with the surrounding cement-based material, The tensioning material is a carbon fiber composite cable for prestressing as described in any one of claims 1 to 5. A prestress induction method characterized by the following.

7. The tension applied to the tensioning material is statically transmitted to the concrete member using a torque wrench. The prestress introduction method according to claim 6, characterized by the above.

8. The tension applied to the tensioning member is transmitted to the concrete member by cutting the tensioning member. The prestress introduction method according to claim 6, characterized by the above.

9. This is a post-tensioning method for introducing prestress, in which a sheath is provided within the concrete member, a tensioning material is inserted into the sheath, grout (a cement-based material) is injected into the sheath, and after the grout hardens, tension is introduced into the concrete member via the grout. The compressive strength of the aforementioned grout is 30 N / mm². 2 Prestressing is introduced after the above conditions are met. A method for introducing prestress according to claim 7, characterized by the above.

10. This is a pretensioning method for introducing prestress to a concrete member, in which tension is introduced to the concrete member via the adhesive force with the surrounding cement-based material, wherein the compressive strength of the cement-based material is 36 N / mm². 2 Prestressing is introduced after the above conditions are met. A method for introducing prestress according to claim 7, characterized by the above.

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