US20200002947A1

US20200002947A1 - Stranded cable wedge

Info

Publication number: US20200002947A1
Application number: US16/569,733
Authority: US
Inventors: Shunji Hachisuka; Hiroshi Kimura; Daisuke Manabe; Hiroyuki Shimmura; Yukio KITADA; Ryo Yamashita
Original assignee: Tokyo Rope Manufacturing Co Ltd; Hinode Ltd
Current assignee: Tokyo Rope Manufacturing Co Ltd; Hinode Ltd
Priority date: 2017-03-14
Filing date: 2019-09-13
Publication date: 2020-01-02
Also published as: JP6705940B2; JPWO2018167849A1; WO2018167849A1

Abstract

A split wedge body, which has a curved inner surface, is formed gradually thicker from a tip portion to a terminal end portion thereof, and is made to cover the outer peripheral surface of a CFRP cable to thereby enclose the outer peripheral surface of the CFRP cable over a prescribed length thereof. A gap extending in the longitudinal direction is assured between end faces that oppose each other when a plurality of the split wedge bodies are arranged on the outer peripheral surface of the CFRP cable. The gap has an inclined portion that runs along a valley of the CFRP cable enclosed by the split wedge bodies.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of PCT International Application No. PCT/JP2017/010243 filed on Mar. 14, 2017, the entire disclosure of the application being considered part of the disclosure of this application and hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a stranded cable wedge.

BACKGROUND ART

Prestressed concrete, in which compressive stress is applied to concrete by a pre-tension or post-tension method, is known in the art. Prestressed concrete is strong not only against compression but also tension and is employed widely in the field of public works, construction and bridge-building.
To achieve the compressive stress applied to prestressed concrete, use is made of the reaction of tensile force applied to a tendon embedded in the concrete. In order to tension the tendon, it is necessary to grip the terminal end of the tendon stably and strongly, and it is required that a terminal member that implements such gripping be firmly anchored (secured) to the terminal end of the tendon.
International Publication No. WO2015/125220 discloses a rope mounting tool for holding a rope by an inner cylinder and tightening the inner cylinder by an outer cylinder.
The inner cylinder is composed of four split members each of which has a curved surface that contacts the rope. The rope is surrounded by the four split members. A gap is formed in the longitudinal direction between mutually adjacent split members.
The outer shape of the inner cylinder constructed by combining the four split members is that of a truncated cone. The outer cylinder has an inner surface lying along the outer shape of the inner cylinder. The inner cylinder is drawn into the outer cylinder by a tensile force that acts upon the rope, whereby the inner cylinder and outer cylinder (namely the rope mounting tool) are anchored to the rope.
When the tensile force continues to be applied to the rope, the inner cylinder gradually penetrates deeper into the outer cylinder and the gap between the mutually adjacent split members gradually becomes narrower. Owing to the narrowing of the gaps between the split members, the rope is tightly clamped by a strong force from the periphery thereof.
When the rope is thus tightened from its periphery by a strong force, the rope (especially the strands on the outer layer thereof) tends to be deformed or elongated so as to protrude (penetrate) into the gaps between the neighboring split members. If, in a case where the gaps between the mutually adjacent split members are narrowed further by continuing the application of the tensile force, portions of the rope protrude into the gaps, the protruding portions may be nipped and crushed by the split members and damage may occur. Nipping damage to the rope is a factor in a decline in rope strength and in a decline in the anchoring performance of the rope placement tool.

DISCLOSURE OF THE INVENTION

An object of the present invention is to prevent damage to a stranded cable (a twisted member) wherein a terminal part is wedged, and in particular to prevent the above-mentioned nipping damage.
A stranded cable wedge according to the present invention comprises a plurality of split wedge bodies, each of which has a curved inner surface and is formed gradually thicker from a tip portion to a terminal end portion thereof, made to cover the outer peripheral surface of a stranded cable (a twisted member) to thereby enclose (embrace) the outer peripheral surface of the stranded cable over a prescribed length thereof. The stranded cable wedge is characterized in that a gap, which is assured between end faces that oppose each other when the plurality of split wedge bodies are arranged on the outer peripheral surface of the stranded cable, has a portion that runs along a valley of the stranded cable enclosed by the split wedge bodies.
The stranded cable is constructed by twisting together multiple strands (multiple filament bundles, multiple linear bodies), and the outer peripheral surface thereof is formed to have valleys that extend helically along the longitudinal direction. The stranded cable wedge comprises a plurality of split wedge bodies made to cover the outer peripheral surface of the stranded cable having such a stranded structure. The split wedge bodies may be obtained by splitting a stranded cable wedge longitudinally into two pieces (two half-bodies), three pieces or four pieces. Each of the split wedge bodies has an inner surface which is curved, and a portion of the stranded cable in the circumferential direction thereof is enclosed by the curved surface. By arranging the plurality of split wedge bodies side by side in the circumferential direction of the stranded cable, a portion of the stranded cable in the longitudinal direction thereof is enclosed (embraced) by the plurality of split wedge bodies with the exception of the gaps assured between the split wedge bodies.
Since each split wedge body is formed to have gradually larger thickness from the tip portion toward the terminal end portion thereof, the stranded cable wedge constructed by combining a plurality of the split wedge bodies has an outer shape that is gradually thicker from its tip portion to its terminal end portion. Although the stranded cable wedge typically is constructed to have the approximate shape of a truncated cone, it may also have the shape of a square pyramid or some other shape. The stranded cable wedge is inserted into the interior of a sleeve having a hollow space the shape of which is similar to the outer shape of the stranded cable wedge. The plurality of split wedge bodies are pressed and tightened from the periphery by the inner wall of the hollow space of the sleeve, whereby the sleeve can be anchored firmly to the stranded cable via the stranded cable wedge.
The opposing end faces of the plurality of split wedge bodies, arranged so as to enclose the outer peripheral surface of the stranded cable, do not contact each other, it being assured that the stranded cable wedge has longitudinally extending gaps the number of which is the same as the number of split wedge bodies. This is for the purpose of allowing further tightening of the stranded cable. By assuring the gaps, the stranded cable wedge can be inserted into the sleeve deeply and the stranded cable can be tightened further from its periphery at this time by the plurality of split wedge bodies even if the stranded cable is reduced in diameter by continuous application of tensile force to the stranded cable. The stranded cable wedge and the above-mentioned sleeve can continue to be anchored firmly to the stranded cable. The above-mentioned gaps can be assured by forming the curved concave surface of each split wedge body to have a shallow depth.
When the stranded cable wedge enters deeply into the sleeve, as mentioned above, the gaps between neighboring split wedge bodies (between the opposing end faces) become gradually narrower.
In accordance with the present invention, the gap between split wedge bodies has a portion (a valley following (tracking) gap portion) that runs along a valley of the stranded cable enclosed by the split wedge bodies. Therefore, even if deformation or elongation of the stranded cable is caused as a result of the stranded cable being tightened from its periphery under a strong force exerted by the stranded cable wedge, the stranded cable that has undergone deformation or elongation will not readily penetrate into the gap portion lying along the valley of the stranded cable. When the gap between split wedge bodies narrows, the stranded cable (the outer-layer strands thereof) is prevented from being nipped and crushed in the gap and is prevented from being damaged. It is possible to prevent a decline in the strength of the stranded cable and a decline in the fixing force of the stranded cable wedge and sleeve.
The stranded cable may be a fiber cable, rope or rod produced by twisting together synthetic fibers, which are represented by carbon fibers, or a fiber bundle obtained by bundling multiple synthetic fibers. It may be a wire cable or rope produced by twisting steel wires together or strands obtained by twisting steel wires together.
Since the valleys of the stranded cable extend helically in the longitudinal direction of the stranded cable, the valley following gap portions running along the valleys of the stranded cable have an angle that is oblique with respect to the direction connecting the tip and terminal end portions of the stranded cable wedge (the axial direction of the stranded cable to which the stranded cable wedge is attached).
Preferably, the gap assured between the opposing end faces includes a valley following gap portion that runs along a valley of the stranded cable, and a valley non-following gap portion that does not run along a valley of the stranded cable, a plurality of the valley following gap portions being formed, in the longitudinal direction of the stranded cable wedge, bracketing the valley non-following gap portions between them. The split wedge bodies can be shaped to readily cover the periphery of the stranded cable.
In an embodiment, the length of the valley following gap portion is greater (longer) than the length of the valley non-following gap portion. The valley following gap portion that runs along the valley of the stranded cable can be assured over a comparatively long distance.
In another embodiment, the direction of the valley following gap portion and the direction of the valley non-following gap portion intersect within a range of 75° to 120°. Since the valley following gap portion runs along a valley of the stranded cable, it is orientated in a direction that coincides with or at least approximates that of the valley of the strand cable. The valley non-following gap portion that intersects the valley following gap portion within the range of 75° to 120° extends in a direction different from that of the valley of the stranded cable (the twisted strands that constitute the stranded cable). By designing the end faces of the split wedge bodies such that the valley following gap portion and valley non-following gap portion intersect within the range of 75° to 120°, concentration of stress in a specific portion of the end faces of the split wedge bodies (particularly a portion constituting a boundary portion of the valley following gap portion and valley non-following gap portion) is alleviated and the valley following gap portion can be assured over a comparatively long distance. Furthermore, since the valley non-following gap portion intersects the strands at a comparatively deep angle (an angle comparatively close to a right angle), nipping of the stranded cable (the outer-layer strands thereof) is difficult even in the valley non-following gap portion.
In a preferred embodiment, the curved inner surface is formed to have a plurality of grooves formed along the strands constituting the stranded cable and having a size conforming to the diameter of the strand constituting the stranded cable. Since the curved inner surface and the stranded cable (the strands constituting the stranded cable) come into broad contact, the anchoring performance of the stranded cable wedge can be improved. Further, since the stranded cable can be constrained to the curved surface by the plurality of grooves, the stranded cable can be prevented from rotating, for example, in the stranded cable wedge, and the above-mentioned gaps between the split wedge bodies (the valley following gap portions) can be made to follow along the valleys of the stranded cable accurately.
In an embodiment, engaging portion for alignment is formed on each of the plurality of split wedge bodies. By way of example, the engaging portion can be constructed by a projection formed on one split wedge body and a recess, which is formed on another split wedge body adjacent the one split wedge body, engaged by the projection. Since the relative positions of the plurality of split wedge bodies (the relative position in the longitudinal direction and the relative position in the circumferential direction) can be fixed (guided), the plurality of split wedge bodies can be arranged correctly around the stranded cable.
The valley following gap portions of the stranded cable wedge running along the valleys of the stranded cable are formed by the end faces that oppose each other when the plurality of split wedge bodies are combined, as described above. With respect to the end faces of the wedge in particular, the present invention can also be defined as follows:
A stranded cable wedge according to the present invention is formed gradually thicker from a tip portion to a terminal end portion thereof and has a curved inner surface that comes into contact with a stranded cable, the wedge enclosing the outer peripheral surface of the stranded cable over a prescribed length thereof by being arranged around the stranded cable leaving a gap in the longitudinal direction, characterized in that an end face of a side wall on both sides of the curved surface of one stranded cable wedge and an end face of a side wall on both sides of the curved surface of another stranded cable wedge adjacent to the one stranded cable wedge, which end faces form the gap, are formed with an inclination that runs along a valley of the enclosed stranded cable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a terminal anchoring structure fixed to terminal end portion of a cable made of carbon fiber reinforced plastic;

FIG. 2 is a longitudinal sectional view of the terminal anchoring structure;

FIG. 3 is a perspective view illustrating the manner in which the cable made of carbon fiber reinforced plastic is embraced by two split wedge bodies;

FIG. 4 is an exploded perspective view of two split wedge bodies and the cable made of carbon fiber reinforced plastic embraced by the two split wedge bodies;

FIG. 5 is a side view illustrating the manner in which the cable made of carbon fiber reinforced plastic is embraced by two split wedge bodies;

FIG. 6 is an enlarged end view taken along line VI-VI of FIG. 5;

FIG. 7 is an enlarged end view taken along line VII-VII of FIG. 5;

FIG. 8 is an enlarged end view taken along line VIII-VIII of FIG. 5; and

FIG. 9, which illustrates another embodiment, is an exploded perspective view of two split wedge bodies and the cable made of carbon fiber reinforced plastic embraced by the two split wedge bodies.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view illustrating an embodiment in which a terminal anchoring structure is applied to a terminal end portion of a cable 1 made of carbon fiber reinforced plastic (CFRP) (referred to also as a Carbon Fiber Composite Cable) (referred to as a CFRP cable below). FIG. 2 is a longitudinal sectional view of the terminal anchoring structure. FIG. 3 is a perspective view illustrating the manner in which two split wedge bodies have been attached to a terminal end portion of the CFRP cable 1, and FIG. 4 is an exploded perspective view thereof. FIG. 5 is a side view when two split wedge bodies have been attached to a terminal end portion of the CFRP cable 1. FIGS. 6 to 8 are enlarged sectional views taken along lines VI-VI, VII-VII, VIII-VIII of FIG. 5, respectively.
With reference to FIGS. 1 and 6, the CFRP cable 1 has a 1×7 structure obtained by twisting together seven carbon fiber bundles 1 a, which are made of carbon fiber reinforced plastic and have a circular cross-section and the material of which is a composite obtained by impregnating multiple continuous carbon fibers 22 with epoxy resin 21 (a structure obtained by twisting six of the carbon fiber bundles 1 a around one centrally located carbon fiber bundle 1 a). Instead of the carbon fibers 22, use may be made of glass fibers, boron fibers, aramid fibers, polyethylene fibers, PBO (polyphenylenebenzobisoxazole) fibers or other fibers. Polyamide or other resins can be used instead of the epoxy resin 21.
The cross-sectional diameter of the CFRP cable 1 is, for example, about 15.2 mm. Hereafter the carbon fiber bundles 1 a constituting the CFRP cable 1 will be referred to as strands 1 a. The six strands constituting the outer layer 1 a extend helically in the longitudinal direction of the CFRP cable 1, and helically extending valleys 1 b are formed between mutually adjacent strands 1 a. The six outer-layer strands 1 a constituting the CFRP cable 1 are indicated by respective letters of the alphabet A through F in FIGS. 6 to 8.
The terminal anchoring structure of this embodiment has a stranded cable wedge (a clamping wedge) 10 (two split wedge bodies 6), which is made of metal, provided on a terminal end portion of the CFRP cable 1, and a sleeve 5, which is made of metal, into which the stranded cable wedge 10 is tightly fitted.
With regard to FIGS. 1 and 2, the sleeve 5 is cylindrical in shape and threads 5 b are formed on the circumferential surface of the sleeve 5 in the vicinity of the terminal end portion. An interior hollow 5 a has a transverse cross-section of approximate oval shape and is formed into the approximate shape of a truncated cone so as to be gradually larger from the tip to the terminal end of the sleeve 5. The terminal end portion of the CFRP cable 1 is inserted into the hollow 5 a of the sleeve 5 from the small opening at the tip of the sleeve 5 and emerges to the exterior from the large opening at the terminal end.
The stranded cable wedge 10 is attached to terminal end portion of the CFRP cable 1 that has emerged to the exterior. The stranded cable wedge 10 is composed of the two slender, elongated split wedge bodies 6 each having an overall length of 175 mm, by way of example. The two split wedge bodies 6 are identical in shape and size, and are fabricated by, for example, casting. With reference to FIG. 4, a curved concave surface 6 a which comes into contact with the CFRP cable 1 is formed longitudinally in the inner surface of each of the split wedge bodies 6. The thickness of each of the split wedge bodies 6 is gradually larger from the tapered tip portion toward the terminal end portion on the opposite side. When the two split wedge bodies 6 are combined, the exterior shape of the transverse cross-section becomes approximately oval and gradually larger from the tip portion toward the terminal end portion. The exterior shape of the two split wedge bodies 6 when they are combined approximately coincides with the shape of the hollow 5 a of the sleeve 5. The material used for the split wedge bodies 6 is spheroidal graphite cast iron, which excels in strength, toughness and fatigue strength, or an austenitic or martensitic stainless steel alloy excelling in strength, toughness, fatigue strength and corrosion resistance.
A groove 7 for applying an O-ring (not shown) is formed circumferentially in the terminal end portion of each split wedge body 6. Combining the two split wedge bodies 6 gives the grooves 7 an annular shape. By applying the O-ring to the grooves 7 imparted with the annular shape, the state in which the terminal portion of the CFRP cable 1 is embraced by the two split wedge bodies 6 can be readily maintained.
The terminal end portion of each split wedge body 6 is formed to have an engaging projection 8A and an engaging recess 8B on both the left and right sides, respectively, that are provided at positions with the curved concave surface 6 a between. When the two split wedge bodies 6 are combined, the engaging projection 8A on one split wedge body 6 engages with the engaging recess 8B on the other split wedge body 6, and the engaging projection 8A on the other split wedge body 6 engages with the engaging recess 8B of the first-mentioned split wedge body. Since the relative positions of the two split wedge bodies 6 (the relative position in the longitudinal direction and the relative position in the circumferential direction) can be fixed (guided) by the engaging projections 8A and engaging recesses 8B, the CFRP cable 1 can be embraced accurately from both sides by the two split wedge bodies 6.
With reference to FIG. 4, a tapered face 6 d that enlarges the bore is formed at the tip portion of the curved concave surface 6 a of each split wedge body 6. By forming the tip portion of the curved concave surface 6 a of each split wedge body 6 with the tapered face 6 d that enlarges the bore, damage to the CFRP cable 1 at the tip portion of the split wedge bodies 6 can be prevented or reduced.
With reference to FIG. 2, the split wedge bodies 6 embracing the CFRP cable 1 are pushed into the hollow portion 5 a of the sleeve 5 from the large opening at the terminal end of the sleeve 5. The split wedge bodies 6 are pressed down from the periphery thereof and tightened by the inner wall of the hollow portion 5 a of the sleeve 5. The sleeve 5 is anchored (wedged) to the terminal end portion of the CFRP cable 1 via the two split wedge bodies 6 (stranded cable wedge 10). Though the sleeve 5 generally is anchored to both terminal ends of the CFRP cable 1, it may be anchored to only one terminal end. The CFRP cable 1 having the sleeve 5 anchored to its terminal end portion via the stranded cable wedge 10 can be used as a tendon in prestressed concrete, by way of example.
With reference to FIG. 4, each split wedge body 6 possesses a structure in which the inner surface thereof has the longitudinally extending curved concave surface 6 a, the side opposite side curved concave surface 6 a being open, as set forth above. Further, both the left and right sides of the curved concave surface 6 a are formed to have a wave-shaped side wall. In the description that follows, one side wall will be referred to as left side wall 6L, and the other side wall on the opposite side will be referred to as right side wall 6R. The inner surfaces of the left and right side walls 6L, 6R also constitute the curved concave surface 6 a.
With reference to FIGS. 4 and 6, the inner surface (curved concave surface 6 a) of each split wedge body 6 is formed to have multiple shallow grooves 6 b extending helically in the longitudinal direction. The multiple shallow helical grooves 6 b have a shape, obtained by transfer of the surface shape of the CFRP cable 1, intended for the purpose of attaching the split wedge bodies 6. Since the CFRP cable 1 is fabricated by placing one strand 1 a having the circular cross-section at the center and twisting together around this strand the six strands 1 a having the circular cross-section, as mentioned above, the six strands 1 a constituting the outer layer all extend helically in the longitudinal direction of the CFRP cable 1. The multiple helical grooves 6 b formed in each curved concave surface 6 a run along respective ones of the helically extending strands 1 a that constitute the CFRP cable 1, and each has a size (width) conforming to the diameter of the strands 1 a. The helical grooves 6 b are formed also in the inner surface of each of the left and right side walls 6L, 6R mentioned above.
When the two split wedge bodies 6 are attached to the CFRP cable 1, each of the twisted six strands 1 a that constitute the CFRP cable 1 fits into a respective helical groove 6 b of the multiple helical grooves 6 b formed in the curved concave surface 6 a. Further, a helically extending ridgeline (elongate projection) 6 c (see FIG. 6) formed between adjacent helical grooves 6 b fits into a helical valley between the strands 1 a. The outer surface of the CFRP cable 1 can be made to broadly contact the curved concave surface 6 a of each split wedge body 8 (the multiple helical grooves 6 b and multiple helical ridgelines 6 c), whereby application of local force to the CFRP cable 1 can be prevented and the gripping force of the CFRP cable 1 by the split wedge bodies 6 can be enhanced.
Further, movement of the CFRP cable 1 is restrained by the multiple helical grooves 6 b formed in the curved concave surfaces 6 a. As a result, movement in the longitudinal direction and rotation of the CFRP cable 1 inside the split wedge bodies 6 is prevented and the attitude or position of the CFRP cable 1 inside the split wedge bodies 6 can be kept fixed.
With reference to FIG. 4, the left and right side walls 6L, 6R of each split wedge body 6 both have respective end faces 30L, 30R defined by the thickness of the split wedge body 6. The end faces 30L, 30R transition smoothly between high and low levels in the longitudinal direction. When the split wedge bodies 6 are viewed from the side (see FIGS. 3 and 5), it can be seen that peaks and valleys are formed alternatingly in the longitudinal direction.
With reference to FIG. 4 for a more detailed description, the left side wall 6L is formed to have three peaks 51L, 52L, 53L, in the order mentioned, from the tip portion toward the terminal end portion of the split wedge body 6. The other right side wall 6R is formed to have three peaks 51R, 52R, 53R, in the order mentioned, from the tip portion toward the terminal end portion of the split wedge body 6. Furthermore, the three peaks 51L to 53L and 51R to 53R of both left and right side walls 6L and 6R, respectively, are gradually taller from the tip portion toward the terminal end portion of the split wedge body 6.
With reference to FIGS. 4 and 5 for a description focused on the end faces 30L, 30R of both side walls 6L, 6R, the peaks 51L, 52L, 53L, 51R, 52R, 53R are given their shape by gently sloping surfaces 31L, 31R, which have a small gradient (inclination), extending over a comparatively long distance, and steeply sloping surfaces 32L, 32R, which have a large gradient (inclination), extending over a comparatively short distance. The gently sloping surfaces 31L, 31R and respective ones of the steeply sloping surfaces 32L, 32R are approximately orthogonal. As a result, the peaks 51L, 52L, 53L, 51R, 52R, 53R each have the approximate shape of a right-angled triangle the apex of which is the boundary between the gently sloping surfaces 31L, 31R and respective ones of the steeply sloping surfaces 32L, 32R. Although the three peaks 51L, 52L, 53L of the left side wall 6L and the three peaks 51R, 52R, 53R of the right side wall 6R are formed at positions having left-right symmetry, there is a difference in that each gently sloping surface 31R of the right side wall 6R descends in the direction from the tip portion toward the terminal end portion of the split wedge body 6 (the height of the side wall gradually decreases), whereas each gently sloping surface 31L of the left side wall 6L rises in the direction from the tip portion toward the terminal end portion of the split wedge body 6 (the height of the side wall gradually increases).
With reference to FIG. 5, the angle of inclination of the gently sloping surfaces 31L, 31R is designed in conformity with twist angle of the CFRP cable 1 (the twist angle of the six outer-layer strands 1 a constituting the CFRP cable 1, the twist angle of the valleys 1 b formed between the strands 1 a). In FIG. 5, the twist angle of the strands 1 a (valleys 1 b) and the angle of inclination of the gently sloping surfaces 31L, 31R (more strictly, the angle of inclination of an inner edge 11, described later, of the gently sloping surfaces 31L, 31R) are indicated by Θ1 and Θ2, respectively. By making the inclination angle Θ2 of the gently sloping surfaces 31L, 31R conform to the twist angle Θ1 of the strands 1 a (valleys 1 b), the CFRP cable 1 (strands 1 a) can be made to run continuously along the inner surface of the left and right side walls 6L, 6R (the above-mentioned grooves 6 b formed in the inner surface of the peaks) over a comparatively long distance, and the split wedge bodies 6 can thus be fixed stably to the CFRP cable 1.
With reference to FIGS. 6 to 8, the gently sloping surfaces 31L, 31R are formed so as to twist in accordance with the height position of the side walls 6L, 6R. That is, the gently sloping surfaces 31L, 31R are such that when at a low position, the inner edge (inner ridgeline) 11 is at a position higher than that of the outer edge (outer ridgeline) (FIGS. 6, 8), and the gently sloping surfaces 31L, 31R are such that when at a high position, the outer edge is at a position higher than that of inner edge 11 (FIGS. 6, 8). At the intermediate position (FIG. 7), the outer edge and the inner edge 11 of the gently sloping surfaces 31L, 31R are at substantially the same height position. By forming the gently sloping surfaces 31L, 31R so as to twist, gaps G formed when the two split wedge bodies 6 are combined can be assured at substantially equal intervals across the full width of the gently sloping surfaces 31L, 31R.
With reference to FIG. 5, combining the two split wedge bodies 6 brings the end face 30L of the left side wall 6L of one split wedge body 6 into opposition with the end face 30R of the right side wall 6R of the other split wedge body 6, and brings the end face 30R of the right side wall 6R of one split wedge body 6 into opposition with the end face 30L of the left side wall 6L of the other split wedge body 6. The peaks of one split wedge body 6 oppose the valleys of the other split wedge body 6 across the gap G and, conversely, the valleys 6 of one split wedge body 6 oppose the peaks of the other split wedge body 6 across the gap G.
With reference to FIG. 5 and FIGS. 6 to 8, when the two split wedge bodies 6 are combined with the CFRP cable 1 embraced between them, the end faces 30L, 30R of both side walls 6L, 6R of the two split wedge bodies 6 do not contact each other, and the longitudinally extending gaps G are formed on both sides of the split wedge bodies 6. Since the end faces 30L, 30R of both side walls 6L, 6R transition smoothly between high and low levels in the longitudinal direction, as mentioned above, the gaps G appear to extend wave-like in the longitudinal direction when viewed from the side. The gaps G can be assured by making the depth of the curved concave surface 6 a of each split wedge body 6 smaller than the cross-sectional radius of the CFRP cable 1.
The gaps G on both sides of the two split wedge bodies 6 are assured even with the split wedge bodies 6 in a state in which they have been pushed into the sleeve 5 (see FIG. 2). For example, the depth of the above-mentioned curved concave surface 6 a is adjusted so as to assure a gap G on the order of 0.5 to 2 mm when the split wedge bodies 6 are pushed into the sleeve 5. By assuring the gaps G in advance, the CFRP cable 1 can be tightened firmly from the periphery thereof by the two split wedge bodies 6 and the two split wedge bodies 6 and sleeve 5 can continue to be stably anchored to the terminal portion of the CFRP cable 1 even if the split wedge bodies 6 gradually penetrate deeper into the sleeve 5 owing to continuous application of a tensile force to the CFRP cable 1, or even if the diameter of the CFRP cable 1 is reduced owing to use over a long period of time.
With reference to FIG. 5 and FIGS. 6 to 8, and as described above, the gently sloping surfaces 31L, 31R are formed so as to have an angle along the twist angle Θ1 of the strands 1 a (valleys 1 b) that constitute the CFRP cable 1, and the gaps G between the gently sloping surfaces 31L, 31R run along the helical valleys 1 b, which are on the surface of the CFRP cable 1, formed between the twisted strands 1 a. That is, the gaps G formed by the gently sloping surfaces 31L, 31R follow along the valleys 1 b of the CFRP cable 1 (see FIGS. 6 to 8). As a consequence, even if the gaps G between the two split wedge bodies 6 are narrowed owing to continuous application of tensile force to the CFRP cable 1, it will be difficult for the strands 1 a to enter into the gaps G between the two split wedge bodies 6, and it will be difficult for the stands 1 a to be nipped (clamped) between the two split wedge bodies 6 (the gently sloping surfaces 31L, 31R) (that is, the strands 1 a will not readily be crushed by the split wedge bodies 6). Nipping damage to the CFRP cable 1 by the split wedge bodies 6 can be prevented effectively. This means that a decline in the strength of the CFRP cable 1, as well as a decline in the fixing performance of the split wedge bodies 6 and sleeve 5, is prevented.
It goes without saying that the helical grooves 6 b (see FIG. 4 and FIGS. 6 to 8) formed in the curved concave surface 6 a of each of the split wedge bodies 6 are formed in advance such that the gaps G between the gently sloping surfaces 31L, 31R will run along the helical valleys 1 b on the surface of the CFRP cable 1. As mentioned above, owing to the helical grooves 6 b, the CFRP cable 1 is always disposed on the curved concave surface 6 a of each split wedge body in a fixed attitude. By placing the two split wedge bodies 6 such that the CFRP cable 1 (strands) fits into the helical grooves 6 b, the gaps G between the gently sloping surfaces 31L, 31R will run along the helical valleys 1 b on the surface of the CFRP cable 1. Since it is not necessary to carefully position the two split wedge bodies 6, it is easy to carry out the work for fabricating the terminal anchoring structure (the anchoring work of split wedge bodies 6 and the sleeve 5) at a construction site or the like.
A portion of the gap G formed by the gently sloping surfaces 31L, 31R runs along the helical valleys 1 b of the CFRP cable 1 (this is a valley following gap portion), while a portion of the gap G formed by the steeply sloping surfaces 32L, 32R does not run along helical valleys 1 b (this is a valley non-following gap portion). However, the valley non-following gap portion formed by the steeply sloping surfaces 32L, 32R has a direction substantially orthogonal to the valley following gap portion formed by the gently sloping surfaces 31L, 31R, i.e., is oriented in a direction substantially orthogonal to the helically extending strands 1 a (valleys 1 b) constituting the CFRP cable 1. In addition, since the steeply sloping surfaces 32L, 32R are short in length, the strands 1 a will not readily enter into the valley non-following gap portion formed by the steeply sloping surfaces 32L, 32R and nipping damage is not likely to occur.
Reference will be had to FIG. 5 to give a more detailed description of the structure of the end faces 30L, 30R (gently sloping surfaces 31L, 31R and steeply sloping surfaces 32L, 32R) of the split wedge bodies 6.
As mentioned above, the stranded cable wedge (gripping member) 10 for gripping the CFRP cable (stranded cable) 1 constructed by twisting together multiple (seven in this embodiment) strands 1 a includes multiple (two in this embodiment) split wedge bodies 6 which, by being combined so as to embrace the CFRP cable 1, enclose a portion of the CFRP cable 1 in the longitudinal direction. The split wedge bodies 6 include respective ones of the end faces 30L, 30R that oppose each other across the gap G when the split wedge bodies 6 are combined embracing the CFRP cable 1. A portion of a helically extending valley 1 b formed at the boundary between strands 1 a can be confirmed visually from the outside through the gap G between the opposing end faces 30L, 30R.
The end faces 30L, 30R have the gently sloping surfaces 31L, 31R and the steeply sloping surfaces 32L, 32R, and the inner edges 11 of the gently sloping surfaces 31L, 31R are formed substantially parallel to portions of the valleys 1 b of the CFRP cable 1. The end faces 30L, 30R have multiple (three in this embodiment) inner edges 11, and the multiple inner edges 11 are connected by inner edges 12 of the steeply sloping surfaces 32L, 32R formed non-parallel to portions of the valleys 1 b.
The split wedge bodies 6 are designed such that the direction of the inner edges 11 of the gently sloping surfaces 31L, 31R and the direction of the inner edges 12 of the steeply sloping surfaces 32L, 32R intersect within a range of 75° to 120° (this will be referred to as “condition 1” below). If the angle falls below the lower limit of condition 1, namely below 75°, this is undesirable because the boundaries between the inner edges 11 of the gently sloping surfaces 31L, 31R and the inner edges 12 of the steeply sloping surfaces 32L, 32R will develop a sharp angle where stress will tend to concentrate, and because it will tend to be difficult to assure the draft angle of the inner edges 12 of the steeply sloping surfaces 32L, 32R. If the angle exceeds the upper limit of condition 1, namely exceeds 120°, this is undesirable because the proportion (length) of the inner edges 11 of the gently sloping surfaces 31L, 31R that occupies the end faces 30L, 30R will tend to decrease.
In this embodiment, the strands 1 a constituting the CFRP cable 1 have a twist angle Θ1 of about 7 to 10° with respect to a direction D lying parallel to axial direction 1 c of the CFRP cable 1. The valleys 1 b between the strands 1 a also have a twist angle Θ1 of about 7 to 10°. Since the inner edges 11 of the gently sloping surfaces 31L, 31R are formed substantially parallel to the valleys 1 b of the CFRP cable 1, as mentioned above, the inclination angle Θ2 of the inner edges 11 also is about 7 to 10°. An angle Θ3 at which the direction of the inner edges 11 of the gently sloping surfaces 31L, 31R and the direction of the inner edges 12 of the steeply sloping surfaces 32L, 32R intersect is designed to be about 85°. This satisfies condition 1 cited above.
In accordance with the stranded cable wedge 10, the end faces 30L, 30R of the respective two split wedge bodies 6 have the gently sloping surfaces 31L, 31R that include the inner edges 11 formed parallel to portions of the valleys 1 b of the CFRP cable 1. Therefore, by attaching the two split wedge bodies 6 to the CFRP cable 1 such that the valleys 1 b of the CFRP cable 1 are situated between the inner edges 11 of each of the opposing gently sloping surfaces 31L, 31R of the two split wedge bodies 6, portions that follow along the valleys 1 b having the twist angle Θ1 can be provided in the gap G provided between the end faces 30L, 30R that oppose each other when the CFRP cable 1 is embraced by the split wedge bodies 6. Consequently, even in a case where the CFRP cable 1 is tightened via the stranded cable wedge 10 and the strands 1 a undergo deformation or elongation, it will be difficult for the deformed or elongated strands 1 a to bulge into the gap G and the clamping of the CFRP cable 1 between the end faces 30L, 30R can be suppressed. Accordingly, even in a case where the stranded cable wedge 10 is pushed deeply into the sleeve 5 and the gap G grows narrow, the clamping and crushing of the CFRP cable 1 by the end faces 30L, 30R can be suppressed or reduced and, hence, so can damage to the CFRP cable 1.
Furthermore, in accordance with the stranded cable wedge 10, since the end faces 30L, 30R of the respective multiple split wedge bodies 6 have the multiple inner edges 11 and the inner edges 12 formed non-parallel to portions of the valleys 1 b so as to connect the multiple inner edges 11, it is possible to provide a plurality of the gaps G inclined so as to follow along the valleys 1 b having the twist angle Θ1. This enables the distance of the valleys 1 b of CFRP cable 1 situated in the gaps G to be extended. Accordingly, the clamping of the CFRP cable 1 in the gaps G and damage to the cable can be suppressed or reduced to a greater degree.
Furthermore, in accordance with the stranded cable wedge 10, the design is such that the inner edges 11 of the gently sloping surfaces 31L, 31R are longer than the inner edges 12 of the steeply sloping surfaces 32L, 32R, and the direction of the inner edges 11 and direction of the inner edges 12 intersect within a range of 75° to 120°. As a consequence, concentration of stress at the boundaries between the inner edges 11 of the gently sloping surfaces 31L, 31R and the inner edges 12 of the steeply sloping surfaces 32L, 32R is mitigated and the length of the portion of the gaps G inclined so as to follow along the valleys 1 b having the twist angle Θ1 can be increased. Accordingly, the clamping of the CFRP cable 1 in the gaps G and damage to the cable can be suppressed to an even greater degree.
FIG. 9 illustrates split wedge bodies 6A of another embodiment. These differ from the split wedge bodies 6 described above in that the terminal end portion of each is not formed to have the engaging projection 8A and the engaging recess 8B (see FIG. 4). As mentioned above, the engaging projection 8A and the engaging recess 8B are provided in order to fix (guide) the relative positions of the two split wedge bodies 6. Even if the split wedge bodies are not equipped with these, a curved concave surface 6 a of each of the split wedge bodies 6A is formed to have helical grooves 6 b, as mentioned above, and therefore the two split wedge bodies 6A embracing the CFRP cable 1 will not undergo any large positional displacement. Naturally, when consideration is given to the time required to accurately attach the split wedge bodies to the CFRP cable 1, it is preferred that the engaging projection 8A and engaging recess 8B be formed.
In the embodiments set forth above, though modes are described in which the CFRP cable 1 is enclosed by the two split wedge bodies 6, 6A, the CFRP cable 1 may just as well be enclosed by three or four split wedge bodies. Further, in the above-described embodiments, while the opposing end faces 30L, 30R of the left and right side walls 6L, 6R have the difference in levels (a wave-like shape), they are also formed in a straight line from the tip portion to the terminal end portion of each of the split wedge bodies 6, 6A. However, they can be formed to curve in the circumferential direction.

Claims

What is claimed is:

1. A stranded cable wedge comprising a plurality of split wedge bodies, each of which has a curved inner surface and is formed gradually thicker from a tip portion to a terminal end portion thereof, made to cover the outer peripheral surface of a stranded cable to thereby enclose the outer peripheral surface of the stranded cable over a prescribed length thereof;

characterized in that a gap, which is assured between end faces that oppose each other when said plurality of split wedge bodies are arranged on the outer peripheral surface of the stranded cable, has a valley following gap portion that runs along a valley of the stranded cable enclosed by said split wedge bodies.

2. A stranded cable wedge according to claim 1, wherein the gap assured between the opposing end faces includes a valley following gap portion that runs along a valley of the stranded cable and a valley non-following gap portion that does not run along a valley of the stranded cable; a plurality of said valley following gap portions being formed in the longitudinal direction bracketing the valley non-following gap portions between them.

3. A stranded cable wedge according to claim 2, wherein length of said valley following gap portion is greater than length of said valley non-following gap portion.

4. A stranded cable wedge according to claim 2, wherein direction of said valley following gap portion and direction of said valley non-following gap portion intersect within a range of 75° to 120°.

5. A stranded cable wedge according to claim 1, wherein said curved inner surface is formed to have a plurality of grooves formed along the strands constituting the stranded cable and each having a size conforming to the diameter of the strand constituting the stranded cable.

6. A stranded cable wedge according to claim 1, wherein engaging portion for alignment is formed on each of the plurality of split wedge bodies.

7. A stranded cable wedge formed gradually thicker from a tip portion to a terminal end portion thereof and having a curved inner surface that comes into contact with a stranded cable, said wedge enclosing the outer peripheral surface of the stranded cable over a prescribed length thereof by being arranged around the stranded cable leaving a gap in the longitudinal direction;

wherein an end face of a side wall on both sides of the curved surface of one stranded cable wedge and an end face of a side wall on both sides of the curved surface of another stranded cable wedge adjacent to said one stranded cable wedge, which end faces form the gap, are formed with an inclination that runs along a valley of the enclosed stranded cable.

8. A stranded cable wedge according to claim 7, wherein the end face of both side walls includes a gently sloping surface that runs along a valley of the stranded cable, and a sharply sloping surface that does not run along a valley of the stranded cable; a plurality of said gently sloping surfaces being formed in the longitudinal direction bracketing the sharply sloping surfaces.

9. A stranded cable wedge according to claim 8, wherein length of said gently sloping surface is greater than length of said sharply sloping surface.

10. A stranded cable wedge according to claim 8, wherein direction of said gently sloping surface and direction of said sharply sloping surface intersect within a range of 75° to 120°.