Multi-strand type pre-grouted PC steel material, method for manufacturing PC structures

Abstract

To provide a multi-strand type pre-grouted PC steel material containing multiple PC steel strands. [Solution] Multiple PC steel strands, numbering from two to four, A sheath that covers the aforementioned multiple PC steel strands together, The system comprises the aforementioned plurality of PC steel strands and a pre-grout disposed between them and the sheath, The aforementioned multiple PC steel strands are twisted together, forming a multi-strand type pre-grouted PC steel material.

Description

Technical Field

[0001] The present disclosure relates to a multi-strand pre-grout PC steel material and a method for manufacturing a PC structure.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a pre-grout PC steel material, which includes a step of applying a cement-based grout composition to the outer periphery of a PC steel material and a step of covering the outer periphery of the applied cement-based grout composition with a plastic sheath.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Concrete structures have the characteristic of being weak in tensile strength. Therefore, in order to control the tensile stress when the concrete structure receives a load and prevent cracks and the like from occurring, a tension member such as a PC steel strand is used by applying a compressive force to the concrete structure in advance.

[0005] When installing a PC steel strand in a concrete structure, in order to protect the PC steel strand and enhance its corrosion resistance, a grout such as cement milk is arranged around the PC steel strand.

[0006] In addition, a pre-grout PC steel material in which pre-grout is arranged around a PC steel strand at a factory is also used.

[0007] In pre-grouted PC steel materials, the PC steel strands are protected by the pre-grout even during transportation before construction, thus enhancing corrosion resistance.

[0008] In recent years, there has been a demand for multi-strand pre-grout PC steel materials, which include multiple strands of PC steel, in order to reduce the number of pre-grout PC steel materials needed when installing them in concrete structures and to improve work efficiency.

[0009] Therefore, the purpose of this disclosure is to provide a multi-strand type pre-grouted PC steel material that includes multiple PC steel strands. [Means for solving the problem]

[0010] The multi-strand type pre-grouted PC steel material of this disclosure comprises a plurality of PC steel strands, which number between two and four; a sheath that covers the plurality of PC steel strands collectively; and pre-grout disposed between the plurality of PC steel strands and the sheath, wherein the plurality of PC steel strands are twisted together. [Effects of the Invention]

[0011] According to this disclosure, a multi-strand type pre-grouted PC steel material containing multiple PC steel strands can be provided. [Brief explanation of the drawing]

[0012] [Figure 1A] Figure 1A is an explanatory diagram of a cross-section perpendicular to the longitudinal side of a multi-strand type pre-grouted PC steel material according to one embodiment of the present disclosure. [Figure 1B] Figure 1B is an explanatory diagram of a cross-section perpendicular to the longitudinal side of a multi-strand type pre-grouted PC steel material according to one embodiment of the present disclosure. [Figure 1C] Figure 1C is an explanatory diagram of a cross-section perpendicular to the longitudinal side of a multi-strand type pre-grouted PC steel material according to one embodiment of the present disclosure. [Figure 2]FIG. 2 is a side view of a multi-strand pre-grout PC steel material according to an aspect of the present disclosure. [Figure 3A] FIG. 3A is an explanatory view of a manufacturing process of a multi-strand pre-grout PC steel material according to an aspect of the present disclosure. [Figure 3B] FIG. 3B is an explanatory view of a manufacturing process of a multi-strand pre-grout PC steel material according to an aspect of the present disclosure. [Figure 4A] FIG. 4A is an explanatory view of a PC structure according to an aspect of the present disclosure. [Figure 4B] FIG. 4B is an explanatory view of a PC structure according to an aspect of the present disclosure. [Figure 5] FIG. 5 is an explanatory view when the PC structure according to an aspect of the present disclosure is a bridge. [Figure 6] FIG. 6 is a flowchart of a manufacturing method of a PC structure according to an aspect of the present disclosure. [Figure 7] FIG. 7 is a flowchart of a manufacturing method of a PC structure according to an aspect of the present disclosure.

Mode for Carrying Out the Invention

[0013] The mode for carrying out the invention will be described below

[0014] [Description of Embodiment of the Present Disclosure] First, the embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description thereof will not be repeated.

[0015] (1) A multi-strand pre-grout PC steel material according to an aspect of the present disclosure includes a plurality of PC steel strands of 2 or more and 4 or less, a sheath that collectively covers the plurality of PC steel strands, and a pre-grout disposed between the plurality of PC steel strands and the sheath, and the plurality of PC steel strands are twisted together. [[ID=;40]]

[0016] In the following description, the multi-strand pre-grout PC steel material is also simply referred to as "pre-grout PC steel material".

[0017] By using two or more strands of PC steel in pre-grouted PC steel, the tension force that the pre-grouted PC steel exerts on the concrete structure can be sufficiently increased.

[0018] When installing pre-grouted PC steel bars into a concrete structure, after installation, it is necessary to remove the sheath from the longitudinal end of the pre-grouted PC steel bar, wipe off the pre-grout, and install anchoring devices at the longitudinal end of each PC steel strand. Pre-grouted PC steel bars can be applied to various concrete structures, but in the case of concrete structures such as bridges, the area around the longitudinal end of the pre-grouted PC steel bar is often a very narrow space due to being surrounded by other adjacent structures. For this reason, by limiting the number of PC steel strands in the pre-grouted PC steel bar to four or less, the amount of work required when installing the pre-grouted PC steel bar into a concrete structure can be reduced, making it easier to install the pre-grouted PC steel bar into the concrete structure.

[0019] By twisting together multiple strands of PC steel wire in pre-grouted PC steel, the multiple strands of PC steel wire can be handled as a single unit during the manufacturing of pre-grouted PC steel, thereby increasing the productivity of pre-grouted PC steel.

[0020] Because pre-grouted PC steel materials have pre-grout, the stranded PC steel is protected by the pre-grout even during transportation before construction, thereby improving corrosion resistance.

[0021] (2) In (1), the twist pitch of the plurality of PC steel strands may be 1.5 m or more and 4.0 m or less.

[0022] By setting the twisting pitch of multiple PC steel wires to 4.0m or less, the contour of the bundle in a cross-section perpendicular to the longitudinal side of the bundle can be made closer to a perfect circle, thereby improving the handling of pre-grouted PC steel materials.

[0023] By setting the twist pitch of multiple PC steel wires to 1.5m or more, productivity can be increased when twisting multiple PC steel wires together.

[0024] (3) In (1) or (2), the roundness of the sheath in a cross section perpendicular to the longitudinal side may be 0 mm or more and 7 mm or less.

[0025] By making the sheath's roundness 7 mm or less, it becomes possible to make the outer shape of the pre-grouted PC steel material closer to a perfect circle, improving handling when installing it in concrete structures.

[0026] (4) In any of (1) to (3), the pre-grout may contain epoxy resin.

[0027] Since epoxy resin can achieve high hardness after curing, the inclusion of epoxy resin in the pre-grout protects the bundle of multiple PC steel strands and enhances corrosion resistance.

[0028] (5) A method for manufacturing a PC structure according to one aspect of the present disclosure comprises a PC steel installation step of installing a multi-strand type pre-grouted PC steel material inside a concrete structure, an anchoring device installation step of installing anchoring devices at the ends of a plurality of PC steel strands included in the multi-strand type pre-grouted PC steel material, and a tensioning force introduction step of introducing tension to the plurality of PC steel strands, wherein the multi-strand type pre-grouted PC steel material comprises a plurality of PC steel strands, which are two to four, a sheath that covers the plurality of PC steel strands collectively, and pre-grout disposed between the plurality of PC steel strands and the sheath, and the plurality of PC steel strands are twisted together.

[0029] In a method for manufacturing PC steel according to one aspect of this disclosure, pre-grouted PC steel according to one aspect of this disclosure is used. Since the number of PC steel strands in the pre-grouted PC steel according to one aspect of this disclosure is small, between two and four, the number of anchoring devices to be installed in the anchoring device installation process can be reduced, thereby reducing the labor required to install the anchoring devices. As a result, the construction period when manufacturing PC structures can also be shortened.

[0030] (6) In (5), between the PC steel material installation step and the anchoring device installation step, there may be a sheath removal step of removing the sheath at the end along the longitudinal side of the multi-strand type pre-grouted PC steel material, an untwisting step of untwisting the plurality of PC steel strands of the multi-strand type pre-grouted PC steel material in the portion from which the sheath has been removed by the sheath removal step, and a wiping step of wiping off the pre-grout adhering to the plurality of PC steel strands in the portion from which the sheath has been removed by the sheath removal step.

[0031] In the sheath removal process and the untwisting process, the sheaths at the ends along the longitudinal direction of the pre-grouted PC steel material are removed, and the twists of the PC steel strands are undone, making it possible to install anchoring devices on each PC steel strand.

[0032] In the wiping process, pre-grout adhering to multiple PC steel strands is wiped away, preventing pre-grout from entering between the anchoring device and the PC steel strands, thereby improving the adhesion between the anchoring device and the PC steel strands.

[0033] (7) In (5) or (6), the PC steel installation step may involve installing the multi-strand type pre-grouted PC steel within an external sheath installed within the concrete structure.

[0034] By placing an external sheath within the concrete structure and pre-grouted PC steel materials within the external sheath, it becomes possible to avoid the impact on the construction schedule due to the hardening process of the pre-grout.

[0035] (8) In any of (5) to (7), the concrete structure is a bridge, In the PC steel installation process, the multi-strand type pre-grouted PC steel may be installed along the longitudinal direction of the bridge.

[0036] The number of PC steel strands contained in the pre-grouted PC steel material used in the method for manufacturing PC structures according to one aspect of this disclosure is small, between two and four strands, which reduces the number of anchoring devices to be installed in the anchoring device installation process. This reduces the labor required to install the anchoring devices and shortens the construction period when manufacturing PC structures.

[0037] Therefore, the method for manufacturing a PC structure according to one aspect of this disclosure can be particularly effective when applied to a bridge where the space for installing the anchoring device is particularly narrow.

[0038] [Details of the embodiments of this disclosure] A specific example of a method for manufacturing multi-strand pre-grouted PC steel and PC structures according to one embodiment of this disclosure (hereinafter referred to as "this embodiment") will be described below with reference to the drawings. However, the present invention is not limited to these examples and is intended to include all modifications within the meaning and scope of the claims as indicated by the claims. [Multi-strand type pre-grouted PC steel] An example of the configuration of the multi-strand type pre-grouted PC steel material of this embodiment will be explained using Figures 1A, 1B, 1C, and 2.

[0039] Figures 1A, 1B, and 1C are longitudinal and perpendicular cross-sectional views of a multi-strand pre-grouted PC steel bar. Figure 2 is a side view of the multi-strand pre-grouted PC steel bar. In Figure 2, a bundle 100, which consists of multiple PC steel strands 11, is shown as a single cylinder.

[0040] In Figures 1A, 1B, and 1C, the Z-axis, perpendicular to the plane of the paper, corresponds to the axis along the longitudinal direction of the multi-strand pre-grouted PC steel material, and the XY plane corresponds to the plane perpendicular to the longitudinal direction of the multi-strand pre-grouted PC steel material. Figure 2 also shows the X, Y, and Z axes in accordance with Figures 1A, 1B, and 1C.

[0041] Figures 1B and 1C are modified examples of the multi-strand type pre-grouted PC steel material of this embodiment. Therefore, the explanation will mainly use Figures 1A and 2, and use Figures 1B and 1C as needed.

[0042] In this specification, multi-strand pre-grouted PC steel means PC steel containing multiple strands of PC steel, with pre-grout and a sheath arranged outside of the multiple strands of PC steel.

[0043] In this specification, a PC structure refers to a structure in which multi-strand pre-grouted PC steel is placed within a concrete structure, thereby applying prestress, which is a tensile force, to the concrete structure. In the terms PC structure, PC steel, and PC steel strands, "PC" is an abbreviation for "prestressed concrete."

[0044] As shown in Figure 1A, the pre-grouted PC steel material 10 of this embodiment comprises a plurality of PC steel strands 11, a sheath 13, and pre-grout 12 arranged between the plurality of PC steel strands 11 and the sheath 13.

[0045] The pre-grouted PC steel material of this embodiment will be described below. (1) Regarding each component of the pre-grouted PC steel material (1-1) PC steel strands, bundle of PC steel strands (Number of PC steel strands) As shown in Figure 1A, the pre-grouted PC steel material 10 has multiple strands of PC steel 11.

[0046] The pre-grouted PC steel material 10 may have two PC steel strands 11, as shown in Figure 1A (pre-grouted PC steel material 10A). The pre-grouted PC steel material 10 may also have three PC steel strands 11, as shown in Figure 1B (pre-grouted PC steel material 10B). Furthermore, the pre-grouted PC steel material 10 may also have four PC steel strands 11, as shown in Figure 1C (pre-grouted PC steel material 10C).

[0047] In other words, the pre-grouted PC steel material 10 can have multiple strands of PC steel 11, ranging from two to four strands.

[0048] By increasing the number of PC steel strands 11 in the pre-grouted PC steel material 10 to two or more, the tension force that the pre-grouted PC steel material 10 exerts on the concrete structure can be sufficiently increased.

[0049] When installing pre-grouted PC steel bars 10 into a concrete structure, after installation, it is necessary to remove the sheath 13 from the longitudinal end of the pre-grouted PC steel bar 10 and wipe off the pre-grout 12. Furthermore, it is necessary to install anchoring devices at the longitudinal end of each PC steel strand 11.

[0050] Pre-grouted PC steel bars 10 can be applied to various concrete structures, but in the case of concrete structures such as bridges, the area near the ends along the length of the pre-grouted PC steel bars 10 is often a very narrow space, due to being surrounded by other adjacent structures. For this reason, by limiting the number of PC steel strands 11 in the pre-grouted PC steel bars 10 to four or less, the amount of work required when installing the pre-grouted PC steel bars 10 on a concrete structure is reduced, and the pre-grouted PC steel bars 10 can be easily installed on the concrete structure.

[0051] The configuration of the multiple PC steel strands 11 of the pre-grouted PC steel material 10 may be the same or different. However, from the viewpoint of improving workability when installing the pre-grouted PC steel material 10 in a concrete structure and manufacturing a PC structure, the configuration of the multiple PC steel strands 11 of the pre-grouted PC steel material 10 may be the same. (PC steel stranded wire) The PC steel stranded wire 11 may contain multiple PC steel wires 111, which are individual steel strands.

[0052] The twist pitch of the multiple PC steel wires 111 in the PC steel stranded wire 11 is not particularly limited, but it may be 12 to 18 times the outer diameter D11 of the PC steel stranded wire 11 so that the PC steel wires 111 do not unravel when the PC steel stranded wire 11 is cut without binding.

[0053] The number of PC steel wires 111 in the PC steel strand 11 is not particularly limited, and multiple PC steel strands 11 can be selected to obtain desired characteristics such as tensile load.

[0054] The multiple PC steel wires 111 included in the PC steel stranded wire 11 may all have the same wire diameter (outer diameter), or at least some of the PC steel wires 111 may have different wire diameters.

[0055] The material of the PC steel wire 111 is not particularly limited, but one or more materials selected from those specified in JIS G 3536 (2014) or those disclosed in Patent Documents 2 and 3 can be used.

[0056] The materials disclosed in Patent Documents 2 and 3 are high-strength. Therefore, compared to using the JIS standard materials mentioned above, the number of PC steel wires 111 required to achieve the same tensile load can be reduced for the PC steel stranded wire 11 and the pre-grouted PC steel material 10, and the outer diameter can be reduced. Therefore, by using the materials disclosed in Patent Documents 2 and 3 for the PC steel wire 111, the handling of the pre-grouted PC steel material 10 can be improved.

[0057] The outer diameter D11 of the PC steel stranded wire 11 is not particularly limited, but may be, for example, 10 mm or more and 40 mm or less, or 11 mm or more and 35 mm or less.

[0058] By making the outer diameter D11 of the PC steel strand 11 40 mm or less, the outer diameter of the bundle 100 and the pre-grouted PC steel material 10 can also be reduced, improving the handling of the pre-grouted PC steel material 10.

[0059] By making the outer diameter D11 of the PC steel strand 11 10 mm or more, the strength of the PC steel strand 11, the bundle 100, and the pre-grouted PC steel material 10 can be increased.

[0060] The outer diameter D11 of the PC steel stranded wire 11 can be measured and calculated, for example, by the following procedure.

[0061] For example, in Figure 2, at the first position 20A indicated by the dotted line, the outer diameter of the smallest inclusion circle C11 (see Figure 1A) of the PC steel strand 11 is measured in a cross section perpendicular to the longitudinal side of the pre-grouted PC steel material 10.

[0062] Next, the outer diameter of the minimum inclusion circle C11 of the PC steel strand 11 is measured in the cross-section at the second position 20B and the cross-section at the third position 20C.

[0063] The second position 20B is located along the longitudinal side of the pre-grouted PC steel material 10, with a distance L1 of 10 cm from the first position 20A. The third position 20C is located with a distance L2 of 10 cm from the second position 20B.

[0064] The average value of the outer diameter of the PC steel stranded wire 11 measured at the cross-section at the first position 20A, the second position 20B, and the third position 20C can be taken as the outer diameter D11 of the PC steel stranded wire 11.

[0065] If the pre-grouted PC steel material 10 includes PC steel strands 11 with different outer diameters, the outer diameter of each can be measured and calculated using the procedure described above. (A collection of PC steel strands) Multiple PC steel strands 11 are twisted together to form a bundle 100. In the case of pre-grouted PC steel material 10A shown in Figure 1A, two PC steel strands 11 are twisted together to form a bundle 100A. In the case of pre-grouted PC steel material 10B shown in Figure 1B, three PC steel strands 11 are twisted together to form a bundle 100B. In the case of pre-grouted PC steel material 10C shown in Figure 1C, four PC steel strands 11 are twisted together to form a bundle 100C.

[0066] By twisting together multiple strands of PC steel wire 11 of the pre-grouted PC steel material 10 to form a bundle 100, the multiple strands of PC steel wire 11 can be handled as a single unit during the manufacturing of the pre-grouted PC steel material 10, thereby increasing the productivity of the pre-grouted PC steel material 10.

[0067] The twist pitch of the multiple PC steel strands 11 is not particularly limited, but may be, for example, 1.5m to 4.0m, or 1.7m to 2.7m.

[0068] By setting the twisting pitch of the multiple PC steel strands 11 to 4.0 m or less, the contour of the bundle 100 in a cross section perpendicular to the longitudinal side of the bundle 100 can be made closer to a perfect circle, thereby improving the handling of the pre-grouted PC steel material 10.

[0069] By setting the twisting pitch of multiple PC steel strands 11 to 1.5m or more, the productivity of twisting multiple PC steel strands 11 together can be increased.

[0070] The outer diameter of the bundle 100, which is a strand of multiple PC steel strands 11, is not particularly limited, but may be, for example, 45 mm or more and 65 mm or less, or 50 mm or more and 60 mm or less.

[0071] By making the outer diameter of the manifold 100 65 mm or less, the outer diameter of the pre-grouted PC steel material 10 can also be reduced, improving the handling of the pre-grouted PC steel material 10.

[0072] By making the outer diameter of the manifold 100 45 mm or more, the strength of the manifold 100 and the pre-grouted PC steel material 10 can be increased.

[0073] The procedure for measuring the outer diameter of the bundle 100 is the same as for measuring the outer diameter of the PC steel stranded wire 11, except that the object of measurement is the outer diameter of the bundle 100, so the explanation will be omitted. The outer diameter of the bundle in each cross section is the diameter D100A of the smallest inclusion circle C100A of the bundle 100A, as shown in Figure 1A.

[0074] The bundle 100 of PC steel strands 11 may have a maximum test force of 2000kN or more and 2500kN or less, or 2200kN or more and 2400kN or less. By setting the maximum test force of the bundle 100 to 2000kN or more, the number of pre-grouted PC steel members 10 installed in the concrete structure can be reduced, thereby lowering costs.

[0075] By limiting the maximum test force of assembly 100 to 2500kN or less, the weight of the pre-grouted PC steel material 10 can be reduced, improving handling.

[0076] The maximum test force of the assembly can be set to a predetermined range, for example, by the material of the PC steel wire 111 or the number of PC steel wires 111 included in the PC steel stranded wire 11.

[0077] The maximum test force can be evaluated by the tensile test described in JIS G 3536 (2014). (1-2) Sheath The pre-grouted PC steel material 10 may have a sheath 13 that covers multiple strands of PC steel 11, specifically a bundle 100, all at once.

[0078] The pre-grouted PC steel material 10 has a sheath 13, which protects the aggregate 100 inside the sheath 13 and prevents the pre-grout 12 from flowing out.

[0079] The material of the sheath 13 is not particularly limited and may contain polyolefin resin or polyethylene resin. In addition to resin, the sheath 13 may also contain additives such as flame retardants.

[0080] The sheath 13 may be positioned to cover the outer circumference of the pre-grout 12. The sheath 13 may also have rib portions 131, as shown in Figure 1A, for example. The rib portions 131 are portions that protrude more than other parts and can be positioned along the longitudinal side of the pre-grout PC steel material 10.

[0081] Furthermore, as shown in Figure 2, the sheath 13 may also have alternating recesses 21 and protrusions 22 along its longitudinal direction on its outer surface in portions other than the rib portion 131. By having alternating recesses 21 and protrusions 22 on the surface of the sheath 13, the contact area with the concrete structure can be increased after the pre-grouted PC steel material 10 is installed in the concrete structure, thereby restricting the movement of the pre-grouted PC steel material 10 along its longitudinal direction.

[0082] The thickness T13 of the sheath 13 is not particularly limited and may be 1 mm or more and 10 mm or less, 2 mm or more and 10 mm or less, or 3 mm or more and 5 mm or less.

[0083] By making the thickness T13 of the sheath 13 1 mm or more, the assembly 100 inside the sheath 13 can be protected. By making the thickness of the sheath 13 10 mm or less, the outer diameter of the pre-grouted PC steel material 10 can be reduced, improving the handling of the pre-grouted PC steel material 10.

[0084] In a cross-section perpendicular to the longitudinal side, the roundness of the sheath 13 may be between 0 mm and 7 mm, or between 1 mm and 6 mm. By making the roundness of the sheath 13 7 mm or less, it becomes possible to make the outer shape of the pre-grouted PC steel material 10 closer to a perfect circle, thereby improving handling when installing it in a concrete structure.

[0085] The roundness can be measured in a cross-section perpendicular to the longitudinal side of the pre-grouted PC steel material 10. For example, in the case of Figure 1A, the diameter D10A of the pre-grouted PC steel material 10 can be measured at multiple locations other than the rib section 131, and the absolute value of the difference between the maximum and minimum values ​​can be divided by 2 to obtain the roundness.

[0086] The number of diameters D10A measured in a single cross-section when determining roundness is not particularly limited, but for example, it may be between 5 and 10 points. (1-3) Pregrout The pre-grouted PC steel material 10 may have a pre-grout 12 placed between a plurality of PC steel strands 11 and a sheath 13.

[0087] Because the pre-grouted PC steel material 10 has pre-grout, the stranded PC steel is protected by the pre-grout even during transportation before construction, thereby improving corrosion resistance.

[0088] The material of the pre-grout is not particularly limited and may include, for example, epoxy resin.

[0089] Since epoxy resin can have high hardness after curing, the inclusion of epoxy resin in the pre-grout protects the bundle 100, which consists of multiple PC steel strands 11, and enhances corrosion resistance.

[0090] The epoxy resin is not particularly limited, but for example, one or more types selected from volac-type epoxy resin, bisphenol A-type epoxy resin, biphenyl-type epoxy resin, triphenylmethane-type epoxy resin, phenol aralkyl-type epoxy resin, etc., can be used.

[0091] Pregrout may also contain one or more types selected from curing agents and inorganic fillers in addition to epoxy resin.

[0092] As a curing agent, for example, a material that can accelerate the curing of epoxy resins can be used, and one or more types selected from amine compounds, acid anhydride compounds, amide compounds, phenolic compounds, carboxylic acid compounds, etc. can be used.

[0093] As inorganic fillers, one or more selected from crystalline silica, fused silica, alumina, zircon, calcium silicate, calcium carbonate, calcium oxide, silicon carbide, silicon nitride, boron nitride, zirconia, fostelite, steatite, spinel, titania, talc, etc. can be used. The form of the inorganic filler is not particularly limited and may be in the form of powder or spherical beads, etc. By adding inorganic fillers, the viscosity of the pre-grout can be adjusted.

[0094] The pre-grout 12 may also be filled into gaps between the PC steel wires 111 contained in the PC steel strand 11. For example, at least some of the components of the pre-grout 12, such as the hardening agent, can be filled into the gaps between the PC steel wires 111 contained in the PC steel strand 11. [Manufacturing method for pre-grouted PC steel] The method for manufacturing pre-grouted PC steel according to this embodiment will now be described. According to the method for manufacturing pre-grouted PC steel according to this embodiment, pre-grouted PC steel according to one aspect of the present disclosure can be manufactured. Therefore, some explanations of matters already described will be omitted. Note that the method for manufacturing pre-grouted PC steel according to one aspect of the present disclosure is not limited to the method described below.

[0095] The manufacturing method for pre-grouted PC steel will be explained using Figures 3A and 3B. In Figures 3A and 3B, a collection 100 of multiple twisted PC steel strands 11 is simplified and shown as a single cylinder.

[0096] A method for manufacturing pre-grouted PC steel materials may include a pre-grout placement step and a sheath formation step. (Pre-grouting process) In the pre-grout placement process, the pre-grout 12 can be placed outside the assembly 100, as shown in Figure 3A.

[0097] In the pre-grout placement process, by arranging the pre-grout 12 so that the outer shape of the pre-grout 12 in a cross section perpendicular to the longitudinal side of the assembly 100 approaches a perfect circle, the outer shape of the sheath 13 can also be made to approach a perfect circle when the sheath 13 is formed in the sheath formation process. In other words, the degree of circularity of the resulting pre-grouted PC steel material 10 in a cross section perpendicular to the longitudinal side can be reduced.

[0098] However, when the number of strands of PC steel 11 included in the bundle 100 is small, between two and four, the outline (outer shape) of the bundle 100 in a cross section perpendicular to the longitudinal side of the bundle 100 contains many irregularities, making it difficult to make the outer shape of the pre-grout 12 close to a circle.

[0099] During the pre-grout placement process, the inventors of the present invention discovered that when placing the pre-grout 12 outside the assembly 100, the viscosity of the pre-grout 12 is increased by cooling it, and then pressurizing it between the assembly 100 and the mold, thereby making the outer shape of the pre-grout 12 closer to a circle.

[0100] Therefore, in the pre-grout placement process, the pre-grout 12, which is placed outside the assembly 100, may be cooled and the pre-grout 12 may be press-injected between the assembly 100 and the mold.

[0101] The temperature at which Pregrout 12 is cooled is not particularly limited and can be selected according to the composition of Pregrout 12. (Sheath formation process) In the sheath formation process, as shown in Figure 3B, a sheath 13 is formed outside the pre-grout 12 to create a pre-grouted PC steel material 10.

[0102] In the sheath formation process, resin that will become the sheath 13 is supplied from two opposing directions, flanking the assembly 100 where the pre-grout 12 is located, thereby forming the sheath 13 outside the pre-grout 12. For this reason, although not shown in Figure 3B, a rib portion 131 can also be formed around the point where the resin supplied from the two directions converges. Furthermore, if necessary, the outer surface of the sheath 13 can be pressed with a mold or the like to form the recessed portion 21 and the convex portion 22 described using Figure 2.

[0103] After the sheath formation process is completed, a cooling process can be carried out to cool the obtained pre-grouted PC steel material 10, if necessary. [Manufacturing method for precast concrete structures] The manufacturing method of the PC structure according to this embodiment will be explained with reference to Figures 4A, 4B, 5, 6, and 7.

[0104] Figure 4A is an explanatory diagram of a PC structure that can be manufactured by the PC structure manufacturing method of this embodiment. Figure 4B is an explanatory diagram of another example configuration of a PC structure that can be manufactured by the PC structure manufacturing method of this embodiment. Figures 6 and 7 are flowcharts of the PC structure manufacturing method of this embodiment. Figure 5 is an explanatory diagram of a bridge.

[0105] First, using Figures 4A and 4B, we will describe the PC structure that can be manufactured by the PC structure manufacturing method of this embodiment. (1) Regarding PC structures As shown in Figure 4A, the PC structure 40 of this embodiment comprises a concrete structure 41 and pre-grouted PC steel materials 10 placed within the concrete structure 41. Figure 4A shows an example using pre-grouted PC steel materials 10A, which include two PC steel strands 11, as shown in Figure 1A.

[0106] Since the pre-grouted PC steel material 10 has pre-grout 12, it may be placed inside the concrete structure 41 so as to be in direct contact with the concrete structure 41, resulting in the PC structure 40A shown in Figure 4A.

[0107] Alternatively, as shown in Figure 4B, an external sheath 44 may be placed inside the concrete structure 41, and pre-grouted PC steel bars 10 may be placed inside the external sheath 44 to form a PC structure 40B.

[0108] In the case of the PC structure 40B shown in Figure 4B, grout 45 may be placed between the outer sheath 44 and the pre-grouted PC steel material 10.

[0109] As for grout 45, a non-shrink grouting agent may be used, and one or more types selected from, for example, cement mortar, epoxy resin mortar, water glass grout, etc. may be used.

[0110] The hardening of pre-grout 12 progresses depending on the type of pre-grout 12, and is influenced by the surrounding humidity and temperature. However, the degree of hardening of pre-grout 12 may vary depending on the environment of the construction site. In addition, depending on the length of the pre-grout PC steel 10, it may take a long time to install it on the concrete structure 41, and the pre-grout may harden during that time.

[0111] Therefore, by placing an external sheath 44 inside the concrete structure 41 and pre-grouted PC steel 10 inside the external sheath 44, it becomes possible to avoid the impact on the construction schedule due to the hardening of the pre-grout 12.

[0112] The pre-grouted PC steel members 10 have both ends along their length located outside the concrete structure 41 and can be gripped by anchoring devices 43. A bearing plate 42 may be placed between the anchoring device 43 and the concrete structure 41.

[0113] The bearing plate 42 is sometimes called a casting plate or anchor plate. The bearing plate 42 is a thick steel billet and has through holes for inserting the PC steel strands 11 of the pre-grouted PC steel material 10. The bearing plate 42 can bear the load applied to the anchoring device 43.

[0114] The bearing plate 42 can be placed on the surface of the concrete structure 41 as shown in Figure 4A, or it can be partially embedded within the concrete structure 41.

[0115] The fixing device 43 is not particularly limited, and various fixing devices capable of gripping the ends of the PC steel strands 11 can be used. The fixing device 43 may have a male cone 43A and a female cone 43B, for example, as shown in Figure 4A. Figure 4A shows an example where the female cone 43B can grip multiple PC steel strands 11 at once, but it is not limited to this configuration, and a female cone 43B may be provided for each PC steel strand 11. (2) Method of manufacturing PC structures The manufacturing method for the PC structure of this embodiment may include a PC steel installation step (S1), a fixing device installation step (S2), and a tension force introduction step (S3), as shown in the flow chart 60 of Figure 6.

[0116] The following describes each step. (2-1) PC steel material installation process (S1) In the PC steel installation process (S1), pre-grouted PC steel 10 according to one aspect of this disclosure can be installed within the concrete structure 41.

[0117] As already explained, in the PC steel installation process (S1), the pre-grouted PC steel 10 may be placed inside the concrete structure 41 in direct contact with the concrete structure 41, as shown in Figure 4A.

[0118] Furthermore, in the PC steel installation process (S1), the pre-grouted PC steel 10 may be installed inside the external sheath 44 installed within the concrete structure 41, as shown in Figure 4B. By placing the external sheath 44 inside the concrete structure 41 and the pre-grouted PC steel 10 inside the external sheath 44, it becomes possible to avoid the impact on the construction schedule due to the hardening of the pre-grout 12.

[0119] Since the pre-grouted PC steel material 10 has already been explained, the explanation will be omitted here. (2-2) Fixing tool installation process (S2) In the anchoring device installation process (S2), anchoring devices can be installed at the ends of each of the multiple PC steel strands 11 contained in the pre-grouted PC steel material 10.

[0120] In the method for manufacturing PC steel materials of this embodiment, pre-grouted PC steel materials 10 according to one aspect of the present disclosure are used. Since the number of PC steel strands 11 that the pre-grouted PC steel materials 10 have is small, between 2 and 4, the number of anchoring devices to be installed in the anchoring device installation process (S2) can be reduced, and the labor required to install the anchoring devices 43 can be reduced. Therefore, the construction period when manufacturing the PC structure 40 can also be shortened. (2-3) Tension introduction process (S3) In the tensioning process (S3), tension can be introduced into multiple PC steel strands 11.

[0121] In the tensioning force introduction process (S3), jacks can be installed at either end along the longitudinal direction of the PC steel strand 11, or at one of the ends along the longitudinal direction of the PC steel strand 11, and tension can be introduced to the PC steel strand 11 by pulling it.

[0122] After the tensioning force introduction process (S3), the position of the fixing device 43 can be adjusted and the end along the longitudinal direction of the PC steel strand 11 can be gripped to maintain the tension force introduced into the PC steel strand 11.

[0123] Since the pre-grouted PC steel material 10 contains multiple PC steel strands 11, the tensioning force introduction process (S3) may be performed for each PC steel strand 11. Alternatively, the tensioning force introduction process (S3) may be performed for multiple PC steel strands 11 at once.

[0124] After the tensioning process (S3), if necessary, a post-processing step may be performed in which the excess length of the PC steel strands protruding from the anchoring device 43 is cut off and a protective cap is installed to cover the end of the pre-grouted PC steel material 10.

[0125] By performing a post-processing step, the ends of the pre-grouted PC steel material 10 and the anchoring device 43 can be protected by protective caps. Grout may be filled into the protective caps as needed.

[0126] As the material for the grout to be filled inside the protective cap, a non-shrink grouting agent may be used, and one or more types selected from, for example, cement mortar, epoxy resin mortar, water glass grout, etc. may be used.

[0127] The method for manufacturing a PC structure in this embodiment may also include a sheath removal step (S11), a de-twisting step (S12), and a wiping step (S13) between the PC steel material installation step (S1) and the anchoring device installation step (S2), according to the flow chart 70 shown in Figure 7.

[0128] The following describes each step. (2-4) Sheath removal process (S11) In the sheath removal process (S11), the sheath 13 can be removed at the end of the pre-grouted PC steel material 10 along its longitudinal direction.

[0129] The method for removing the sheath 13 is not particularly limited; for example, an incision may be made in the sheath 13 with a cutter or the like, and the sheath 13 located at the end along the longitudinal side of the pre-grouted PC steel material 10 may be removed along its longitudinal side.

[0130] The sheath removal process (S11) removes the sheath 13 at the longitudinal end of the pre-grouted PC steel material 10, exposing the internal pre-grout 12 and multiple stranded PC steel wires 11. (2-5) Untwisting process (S12) In the untwisting process (S12), the twists of the multiple PC steel strands 11 of the pre-grouted PC steel material 10 can be untwisted in the portion where the sheath 13 has been removed in the sheath removal process (S11).

[0131] In the sheath removal process (S11) and the untwisting process (S12), the sheath 13 at the ends along the longitudinal direction of the pre-grouted PC steel material 10 is removed, and the twist of the PC steel strands 11 is undone, making it possible to install fixing devices on each PC steel strand 11. (2-6) Wiping process (S13) In the wiping process (S13), the pre-grout 12 adhering to multiple PC steel strands 11 can be wiped off in the area where the sheath 13 was removed in the sheath removal process (S11).

[0132] In the wiping process (S13), the pre-grout 12 adhering to multiple PC steel strands 11 is wiped off, preventing the pre-grout 12 from entering between the anchoring device and the PC steel strands 11, thereby improving the adhesion between the anchoring device and the PC steel strands 11. In the wiping process (S13), if pre-grout 12 is adhering to components other than the PC steel strands 11, such as the surface of the bearing plate 42 that contacts the anchoring device 43, the pre-grout adhering to these components may also be wiped off.

[0133] The wiping step (S13) may be performed, for example, after the anchoring device installation step (S2), by wiping off the pre-grout 12 adhering to the area around the anchoring device. If the wiping step (S13) is performed after the anchoring device installation step (S2), and the pre-grout has hardened, the hardened pre-grout may also be removed. Furthermore, pre-grout adhering to the surface of the anchoring device 43 or other parts where the PC steel stranded wire 11 and the anchoring device 43 come into contact may be left on without wiping, as this can improve corrosion resistance. (3) Examples of applications of the manufacturing method for PC structures The concrete structure in the method for manufacturing a PC structure according to this embodiment may be a bridge.

[0134] In this case, during the PC steel installation process (S1), the pre-grouted PC steel 10 can be installed along the longitudinal side of the bridge.

[0135] Here, an example of a bridge structure will be explained using Figure 5.

[0136] In Figure 5, the Z-axis is the axis along the bridge axis and the longitudinal axis of bridge 50. The Y-axis is the axis perpendicular to the bridge axis and corresponds to the width of bridge 50. The X-axis corresponds to the height.

[0137] In the bridge 50 shown in Figure 5, the pre-grouted PC steel members 10 are arranged along the bridge axis. However, the pre-grouted PC steel members 10 can be arranged according to the direction of the compressive force applied to the concrete structure bridge 50, and are not limited to this configuration.

[0138] As shown in Figure 5, the pre-grouted PC steel members 10 pass through, for example, the deflection section 52 provided in the lower slab 54, and both ends are inserted into insertion holes provided in the crossbeam, which is a concrete structure 51, and can be fixed with anchoring devices.

[0139] In the bridge 50 shown in Figure 5, the pre-grouted PC steel members 10 can be placed in the space 55 located between the upper deck 53 and the lower deck 54, that is, inside the bridge 50.

[0140] In Figure 5, some details, such as the bridge pier 56, have been omitted.

[0141] As shown in Figure 5, when installing pre-grouted PC steel members 10 on a bridge 50, the pre-grouted PC steel members 10 are fixed at the ends of the bridge 50 by anchoring devices. Therefore, workers must remove the sheath 13 from the pre-grouted PC steel members 10, wipe off the pre-grout 12, and install anchoring devices on each PC steel strand 11 in a very narrow space enclosed by concrete structures, which is included in the dotted areas A and B. Consequently, if there are many PC steel strands 11, it will place a heavy burden on the workers and may prolong the construction period.

[0142] In contrast, the number of PC steel strands 11 included in the pre-grouted PC steel material 10 used in the PC structure manufacturing method of this embodiment is small, between 2 and 4 strands, so the number of anchoring devices to be installed in the anchoring device installation process can be reduced. Therefore, the labor required to install the anchoring devices can be reduced, and the construction period when manufacturing the PC structure can be shortened.

[0143] Therefore, the method for manufacturing PC structures according to this embodiment can be particularly effective when applied to bridges where the space for installing anchoring devices is particularly narrow. [Explanation of Symbols]

[0144] 10 Multi-strand type pre-grouted PC steel 10A Multi-strand type pre-grouted PC steel 10B Multi-strand type pre-grouted PC steel 10C Multi-strand type pre-grouted PC steel D10A diameter 11 PC steel stranded wire Minimum inclusion circle of C11 PC steel stranded wire D11 PC steel stranded wire outer diameter 111 PC steel wire 100 sets 100A Assembly C100A Minimum inclusion circle of the set D100A Outer diameter of manifold 100B set 100C set 12 Pre-grout 13 Sheath 131 Rib section T13 Sheath Thickness 21 Recess 22 Convex part 20A 1st position 20B 2nd position 20C 3rd position L1 distance L2 distance 40 PC structures 40A PC structure 40B PC structure 41 Concrete structures 42 Bearing Plate 43 Fixing device 43A Oscone 43B Messcorn 44 External sheath 45 Grout 50 Bridges 51 Concrete structures 52 Deflection section 53 Upper deck version 54 Lower floor version 55 Space 56 Bridge piers Area A B area 60 flow S1 PC steel material installation process S2 Fixing tool installation process S3 Tension introduction process 70 flow S11 Sheath removal process S12 Untwisting process S13 Wiping process

Claims

1. Multiple PC steel strands, numbering between two and four, A sheath that covers the aforementioned multiple PC steel strands together, The system comprises the aforementioned plurality of PC steel strands and a pre-grout placed between them and the sheath, The aforementioned multiple PC steel strands are twisted together, forming a multi-strand type pre-grouted PC steel material.

2. The multi-strand type pre-grouted PC steel material according to claim 1, wherein the twist pitch of the plurality of PC steel strands is 1.5 m or more and 4.0 m or less.

3. The multi-strand type pre-grouted PC steel material according to claim 1 or claim 2, wherein the roundness of the sheath in a cross section perpendicular to the longitudinal side is 0 mm or more and 7 mm or less.

4. The multi-strand type pre-grout PC steel material according to claim 1 or claim 2, wherein the pre-grout contains epoxy resin.

5. The PC steel installation process involves installing multi-strand type pre-grouted PC steel materials within a concrete structure, A fixing device installation step involves installing fixing devices at the ends of multiple PC steel strands included in the multi-strand type pre-grouted PC steel material, The system includes a tensioning force introduction step for introducing tension to the plurality of PC steel strands, The aforementioned multi-strand type pre-grouted PC steel material is The plurality of PC steel strands, which consist of two or more and four or fewer strands, A sheath that covers the aforementioned multiple PC steel strands together, The system comprises the aforementioned plurality of PC steel strands and a pre-grout placed between them and the sheath, A method for manufacturing a PC structure, wherein the aforementioned multiple PC steel strands are twisted together.

6. Between the PC steel installation step and the anchoring device installation step, The process involves removing the sheath at the end along the longitudinal side of the multi-strand type pre-grouted PC steel material, In the portion from which the sheath has been removed by the sheath removal process, a detwisting process is performed to untwist the multiple strands of PC steel wires in the multi-strand type pre-grouted PC steel material. A method for manufacturing a PC structure according to claim 5, comprising: a wiping step of wiping off the pre-grout adhering to the plurality of PC steel strands in the portion from which the sheath has been removed by the sheath removal step.

7. The method for manufacturing a PC structure according to claim 5 or 6, wherein in the PC steel installation step, the multi-strand type pre-grouted PC steel is installed in an external sheath installed within the concrete structure.

8. The aforementioned concrete structure is a bridge, The method for manufacturing a PC structure according to claim 5 or 6, wherein in the PC steel installation step, the multi-strand type pre-grouted PC steel is installed along the longitudinal direction of the bridge.

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