Abstract: An optical fiber-embedded PC steel strand includes a PC steel strand in which a plurality of PC steel wires are twisted together, and an optical fiber. The optical fiber is fixed with a resin in a twist groove that is a groove between two PC steel wires of the PC steel wires, the two PC steel wires being disposed at an outer surface of the PC steel strand and being next to each other. A coefficient of variation in distance between a common tangent of the two PC steel wires that form the twist groove and are next to each other, and a center of the optical fiber is 0.5 or less, as measured in 10 cross sections of the PC steel strand that are perpendicular to a longitudinal direction of the PC steel strand.

Abstract: Provided is a strand board with improved strength and water resistance. Reduction in productivity is prevented and characteristics of the strand board can be varied as desired while achieving certain strength and water resistance of the strand board. A strand board B is formed by stacking and laminating five strand layers 1 each formed by a large number of strands 5. The strand board B has substantially constant density distribution in the lamination direction of the strand layers 1. Three of the five strand layers 1 of the strand board B are high-density strand layers 1a having a higher density than the other strand layers 1, and the other strand layers 1 are low-density strand layers 1b.

Abstract: Provided is a strand board with improved strength and water resistance. Reduction in productivity is prevented and characteristics of the strand board can be varied as desired while achieving certain strength and water resistance of the strand board. A strand board B is formed by stacking and laminating five strand layers 1 each formed by a large number of strands 5. The strand board B has substantially constant density distribution in the lamination direction of the strand layers 1. Three of the five strand layers 1 of the strand board B are high-density strand layers 1a having a higher density than the other strand layers 1, and the other strand layers 1 are low-density strand layers 1b.

Abstract: A concrete structure includes a first concrete member, a second concrete member, a sheath that is disposed in a through hole extending from the first concrete member to the second concrete member, a tension part that is inserted over the entire length of the sheath and that is subjected to a tensile force, a fixing tool that fixes the tension part to the first concrete member or the second concrete member, and an anticorrosion part that covers the fixing tool. The tension part includes a stranded wire part and a first cover that covers an outer periphery of the stranded wire part. A space between the sheath and the tension part is not filled with a grout material.

Abstract: This method for manufacturing a high-density strand board enables high-density strand boards to be formed by using about the same press pressure as press pressures required to form strand boards with common densities, so that the high-density strand boards can be produced without using special facilities and equipment. A pretreatment process P2 is performed on strands 5 before pressing. The pretreatment process P2 is comprised of a first treatment process P2a and a subsequent second treatment process P2b. At least one of beating, high-frequency treatment, high-temperature high-pressure treatment, high-water pressure treatment, repeated deaeration and dehydration treatment, and chemical treatment is performed in the first treatment process P2a, and roll pressing or flat press pressing is performed in the second treatment process P2b. A strand board B with a density of 750 to 950 kg/m3 is formed by using a press pressure of 4 N/mm2 or less.

Abstract: This invention provides a high-strength PC steel wire having a chemical composition containing, in mass %, C: 0.90 to 1.10%, Si: 0.80 to 1.50%, Mn: 0.30 to 0.70%, P: 0.030% or less, S: 0.030% or less, Al: 0.010 to 0.070%, N: 0.0010 to 0.010%, Cr: 0 to 0.50%, V: 0 to 0.10%, B: 0 to 0.005%, Ni: 0 to 1.0%, Cu: 0 to 0.50%, and the balance: Fe and impurities. A ratio between the Vickers hardness (HvS) at a location (surface layer) that is 0.1D [D: diameter of steel wire] from the surface of the steel wire and the Vickers hardness (HvI) of a region on the inner side relative to the surface layer satisfies the formula [1.10<HvS/HvI?1.15]. An average carbon concentration in a region from the surface to a depth of 10 ?m (outermost layer region) of the steel wire is 0.8 times or less a carbon concentration of the steel wire. The steel micro-structure in the region on the inner side relative to the outermost layer region contains, in area %, a pearlite structure: 95% or more.

Abstract: This invention provides a high-strength PC steel wire having a chemical composition containing, in mass %, C: 0.90 to 1.10%, Si: 0.80 to 1.50%, Mn: 0.30 to 0.70%, P: 0.030% or less, S: 0.030% or less, Al: 0.010 to 0.070%, N: 0.0010 to 0.010%, Cr: 0 to 0.50%, V: 0 to 0.10%, B: 0 to 0.005%, Ni: 0 to 1.0%, Cu: 0 to 0.50%, and the balance: Fe and impurities. A ratio between the Vickers hardness (HvS) at a location (surface layer) that is 0.1D [D: diameter of steel wire] from the surface of the steel wire and the Vickers hardness (HvI) of a region on the inner side relative to the surface layer satisfies the formula [1.10<HvS/HvI?1.15]. The steel micro-structure in the region from the surface of the steel wire to 0.01D (outermost layer region) consists of, in area %, a pearlite structure: less than 80%, and the balance: a ferrite structure and/or a bainitic structure.

Abstract: A stranded wire having a plurality of steel wires twisted together includes, in its cross section perpendicular to its longitudinal direction, a central wire as the steel wire, a plurality of first circumferential wires as the steel wires arranged in contact with the central wire to surround an outer periphery side of the central wire, and a plurality of second circumferential wires as the steel wires arranged in contact with the first circumferential wires to surround an outer periphery side of a region where the first circumferential wires are arranged, the second circumferential wires being greater in yield stress than the central wire and the first circumferential wires. The central wire is in surface contact with the first circumferential wires. The first circumferential wires are in surface contact with the second circumferential wires.

Abstract: A concrete structure includes a first concrete member, a second concrete member, a sheath that is disposed in a through hole extending from the first concrete member to the second concrete member, a tension part that is inserted over the entire length of the sheath and that is subjected to a tensile force, a fixing tool that fixes the tension part to the first concrete member or the second concrete member, and an anticorrosion part that covers the fixing tool. The tension part includes a stranded wire part and a first cover that covers an outer periphery of the stranded wire part. A space between the sheath and the tension part is not filled with a grout material.

Abstract: This method for manufacturing a high-density strand board enables high-density strand boards to be formed by using about the same press pressure as press pressures required to form strand boards with common densities, so that the high-density strand boards can be produced without using special facilities and equipment. A pretreatment process P2 is performed on strands 5 before pressing. The pretreatment process P2 is comprised of a first treatment process P2a and a subsequent second treatment process P2b. At least one of beating, high-frequency treatment, high-temperature high-pressure treatment, high-water pressure treatment, repeated deaeration and dehydration treatment, and chemical treatment is performed in the first treatment process P2a, and roll pressing or flat press pressing is performed in the second treatment process P2b. A strand board B with a density of 750 to 950 kg/m3 is formed by using a press pressure of 4 N/mm2 or less.

Abstract: A pregrouted PC steel material (10) includes a 19-wire-twisted PC strand (1), a pregrouted layer (2) disposed on an outer periphery of the PC strand (1), and a sheath (3) configured to cover an outer periphery of the pregrouted layer (2). A filling resin (4) is filled between steel wires (side wires) (1b, 1c, 1d). Since the filling resin (4) does not exude to the pregrouted layer (2) before tensioning of the PC strand (10), an operation of tensioning the PC strand (1) is not hindered by curing of the pregrouted layer (2). In contrast, since the gap between the steel wires is reduced when the PC strand (1) is tensioned, the filling resin (4) flows out (exudes) from between the steel wires to the pregrouted layer (2) to cure the pregrouted layer (2) only after the reduction.

Abstract: Provided is a strand board with improved strength and water resistance. Reduction in productivity is prevented and characteristics of the strand board can be varied as desired while achieving certain strength and water resistance of the strand board. A strand board B is formed by stacking and laminating five strand layers 1 each formed by a large number of strands 5. The strand board B has substantially constant density distribution in the lamination direction of the strand layers 1. Three of the five strand layers 1 of the strand board B are high-density strand layers 1a having a higher density than the other strand layers 1, and the other strand layers 1 are low-density strand layers 1b.

Abstract: Provided is a pregrouted PC steel material comprising a PC steel stranded wire composed of a plurality of steel wires, a pregrout layer disposed on the outer periphery of the PC steel stranded wire so as to accommodate the PC steel stranded wire, a sheath covering the outer periphery of the pregrout layer, and a capsule including a pregrout-hardening agent and a film with which the agent is covered, the capsule being interposed among the steel wires constituting the PC steel stranded wire. The capsule has a strength such that the capsule is not broken before tensioning the PC steel stranded wire but is broken by a tensile force during the tensioning. Also provided is a method for hardening the pregrout layer.

Abstract: This invention provides a high-strength PC steel wire having a chemical composition containing, in mass %, C: 0.90 to 1.10%, Si: 0.80 to 1.50%, Mn: 0.30 to 0.70%, P: 0.030% or less, S: 0.030% or less, Al: 0.010 to 0.070%, N: 0.0010 to 0.010%, Cr: 0 to 0.50%, V: 0 to 0.10%, B: 0 to 0.005%, Ni: 0 to 1.0%, Cu: 0 to 0.50%, and the balance: Fe and impurities. A ratio between the Vickers hardness (HvS) at a location (surface layer) that is 0.1D [D: diameter of steel wire] from the surface of the steel wire and the Vickers hardness (HvI) of a region on the inner side relative to the surface layer satisfies the formula [1.10<HvS/HvI?1.15]. An average carbon concentration in a region from the surface to a depth of 10 ?m (outermost layer region) of the steel wire is 0.8 times or less a carbon concentration of the steel wire. The steel micro-structure in the region on the inner side relative to the outermost layer region contains, in area %, a pearlite structure: 95% or more.

Abstract: This invention provides a high-strength PC steel wire having a chemical composition containing, in mass %, C: 0.90 to 1.10%, Si: 0.80 to 1.50%, Mn: 0.30 to 0.70%, P: 0.030% or less, S: 0.030% or less, Al: 0.010 to 0.070%, N: 0.0010 to 0.010%, Cr: 0 to 0.50%, V: 0 to 0.10%, B: 0 to 0.005%, Ni: 0 to 1.0%, Cu: 0 to 0.50%, and the balance: Fe and impurities. A ratio between the Vickers hardness (HvS) at a location (surface layer) that is 0.1D [D: diameter of steel wire] from the surface of the steel wire and the Vickers hardness (HvI) of a region on the inner side relative to the surface layer satisfies the formula [1.10<HvS/HvI?1.15]. The steel micro-structure in the region from the surface of the steel wire to 0.01D (outermost layer region) consists of, in area %, a pearlite structure: less than 80%, and the balance: a ferrite structure and/or a bainitic structure.

Abstract: A pregrouted PC steel material (10) includes a 19-wire-twisted PC strand (1), a pregrouted layer (2) disposed on an outer periphery of the PC strand (1), and a sheath (3) configured to cover an outer periphery of the pregrouted layer (2). A filling resin (4) is filled between steel wires (side wires) (1b, 1c, 1d). Since the filling resin (4) does not exude to the pregrouted layer (2) before tensioning of the PC strand (10), an operation of tensioning the PC strand (1) is not hindered by curing of the pregrouted layer (2). In contrast, since the gap between the steel wires is reduced when the PC strand (1) is tensioned, the filling resin (4) flows out (exudes) from between the steel wires to the pregrouted layer (2) to cure the pregrouted layer (2) only after the reduction.

Abstract: Provided is a pregrouted PC steel material comprising a PC steel stranded wire composed of a plurality of steel wires, a pregrout layer disposed on the outer periphery of the PC steel stranded wire so as to accommodate the PC steel stranded wire, a sheath covering the outer periphery of the pregrout layer, and a capsule including a pregrout-hardening agent and a film with which the agent is covered, the capsule being interposed among the steel wires constituting the PC steel stranded wire. The capsule has a strength such that the capsule is not broken before tensioning the PC steel stranded wire but is broken by a tensile force during the tensioning. Also provided is a method for hardening the pregrout layer.

Abstract: There is provided a strand that can reduce the trouble in constructing an object to which compression force is applied by the strand and that can keep the construction cost down. A strand 1 is placed in a bore hole provided in a wall or roof surface, and is gripped by a wedge in a tensioned state so as to apply a tensile force to the wall or roof surface. The strand 1 of the present invention includes a pipe-shaped member (corrugated tube 11) made of metal, and a plurality of metal wires 12 arranged on the outer periphery of the corrugated tube 11. The metal wires 12 are arranged to surround the corrugated tube 11 on the cross section of the corrugated tube 11.

Abstract: There is provided a strand that can reduce the trouble in constructing an object to which compression force is applied by the strand and that can keep the construction cost down. A strand 1 is placed in a bore hole provided in a wall or roof surface, and is gripped by a wedge in a tensioned state so as to apply a tensile force to the wall or roof surface. The strand 1 of the present invention includes a pipe-shaped member (corrugated tube 11) made of metal, and a plurality of metal wires 12 arranged on the outer periphery of the corrugated tube 11. The metal wires 12 are arranged to surround the corrugated tube 11 on the cross section of the corrugated tube 11.