JP7026601B2 - Prestressed concrete girder and prestress introduction method - Google Patents

Description

The present invention relates to prestressed concrete girders and prestressed introduction methods. Prestressed concrete girders are used to hang or support bridges, roads, lines (railways) and other building structures.

The so-called prestress method, in which compressive stress (prestress) is introduced in advance into a concrete structure in order to suppress cracks that occur in the concrete structure and reduce the weight of the structure, is known. It is applied to construction. Prestressed concrete structures are called prestressed concrete structures. Conventionally, high-strength steel materials have been used as tension materials applied to prestressed concrete structures. The tension method and the fixing method to concrete are considered to be important technologies.

In conventional prestressed concrete structures, so-called PC steel materials such as PC steel strands and PC steel rods are used as tension materials (Patent Document 1).

In order to prevent the PC steel material from being rusted, the surface of the PC steel material is subjected to a rust preventive treatment such as an epoxy resin film treatment. However, it has recently become known that it is difficult to completely prevent the occurrence of rust and that maintenance costs are required more than expected. Especially when the prestressed concrete structure is a bridge on which a large amount of freeze-melting material is sprayed or a bridge constructed along the coast, it is difficult to prevent rust on the PC steel material for a long period of time.

In order to fix the tense PC steel material to the concrete structure, fixing jigs such as metal anchor heads, wedges, and fixing plates are installed at the ends of the PC steel materials. Rust prevention treatment such as oil seal is required for these fixing jigs. Therefore, long-term maintenance costs such as inspection of oil seals and regular replacement are incurred.

In recent years, continuous fiber reinforced stranded wires have tended to be used as tension materials for prestressed concrete structures instead of PC steel materials. The continuous fiber reinforced stranded wire does not rust under any corrosive environment, and its tensile strength is much higher than that of PC steel. Moreover, since the continuous fiber reinforced stranded wire is lightweight, it does not require heavy machinery during tension work, and work efficiency can be improved. It also contributes to reducing the weight of prestressed concrete structures.

However, the continuous fiber reinforced stranded wire is inferior in strength to the tightening load from the circumferential direction as compared with the PC steel material. Therefore, when the fastener is fixed to the end portion of the continuous fiber reinforced stranded wire by directly gripping it on the continuous fiber reinforced stranded wire by utilizing the taper effect of the wedge as in the case of the PC steel strand, the surface of the continuous fiber reinforced stranded wire is exposed. It is damaged and the fixing tool cannot be firmly fixed to the end of the continuous fiber reinforced stranded wire.

In Patent Document 2, the load end side is composed only of thermosetting resin in a metal socket formed in a conical shape in which the end portion of a fiber reinforced plastic cable (FRP cable) is inserted, and the free single side is thermosetting. The structure of the anchorage, which is composed of a mixture of resin and filler, is described. In this method, the metal wedge does not directly grip the surface of the FRP cable, so that the surface of the FRP cable is less likely to be damaged.

However, in order to achieve high fixing efficiency of the epoxy resin in the metal socket and the end of the FRP cable, it is necessary to increase the diameter and length of the socket. Furthermore, in order to ensure the rigidity of the socket, the material of the socket must be made of metal. Furthermore, in order to completely achieve rust prevention of metal sockets, it is necessary to use special and expensive stainless steel for the sockets, which is expensive. Since a large metal socket is heavy, there is a high possibility that the continuous fiber reinforced stranded wire near the socket will be bent when trying to lift the continuous fiber reinforced stranded wire including the socket. The continuous fiber reinforced stranded wire has the property of being easily bent compared to the PC steel strand, and if the bending curvature is small, the outer stranded wire may be damaged, in which case the continuous fiber. There is a risk of reducing the guaranteed breaking load carried by the reinforced stranded wire.

In addition, when installing multiple FRP cables in a prestressed concrete structure by inserting FRP cables into the sheath embedded in the prestressed concrete structure, a large diameter sheath is used to pass the large diameter socket. Must. As a result, problems such as difficulty in arranging the total number of FRP cables required for design and cross-sectional defects in the prestressed introduction area of the prestressed concrete structure occur.

Japanese Unexamined Patent Publication No. 2016-30933 Japanese Unexamined Patent Publication No. 9-209501

An object of the present invention is to introduce prestress into a concrete girder structure without using any metal member, thereby constructing a highly durable concrete girder structure that does not require maintenance cost.

It is also an object of the present invention to allow a tensioning material for introducing prestress into a concrete girder structure to be tensioned at the ends of the concrete girder structure without tension.

The prestressed concrete girder according to the present invention is provided with a gap (interval) between the first concrete girder structure in which the sheath is embedded and the first concrete girder structure, and the sheath is embedded in the prestressed concrete girder. No. 2 concrete girder structure, a sheath embedded in the first concrete girder structure and a sheath embedded in the second concrete girder structure, provided with a twist fixing tool at at least one of both ends. A continuous fiber reinforced stranded wire in a tense state, one end of which is fixed in the first concrete girder structure and the other end of which is fixed in the second concrete girder structure, and the first concrete girder. The first concrete girder structure and the second concrete girder structure provided in the gap between the structure and the second concrete girder structure and generated by the continuous fiber reinforced stranded wire in a tense state are provided. It is equipped with a supporting reaction force body that supports the tension force in the direction of approaching each other, and the tension force of the continuous fiber reinforcing stranded wire in the tension state is the prestress of the first concrete girder structure, the second concrete girder structure and the above. It is characterized by being introduced into a supporting reaction force body.

According to the present invention, continuous fiber reinforced stranded wires are provided inside the first and second concrete girder structures. Since the continuous fiber reinforced stranded wire does not corrode like metal under any corrosive environment, the yield strength of the first and second concrete girder structures does not decrease due to the corrosion. In addition, since the continuous fiber reinforced stranded wire has a high tensile breaking stress, the bending strength is significantly improved as compared with the concrete girder structure reinforced by PC steel strands and reinforcing bars. Furthermore, since the continuous fiber reinforced stranded wire is lightweight, it is possible to reduce the cost of tension work at the site.

The prestressed concrete girder of the present invention includes a first concrete girder structure, a second concrete girder structure, and a supporting reaction force body provided between them. The continuous fiber reinforced stranded wire in a tense state is provided from the first concrete girder structure to the second concrete girder structure, and both ends thereof are provided in each of the first concrete girder structure and the second concrete girder structure. Since it is fixed to the concrete skeleton, prestress as a reaction force of tension is introduced into the first concrete girder structure and the second concrete girder structure, and the supporting reaction force body between them. To. Since the continuous fiber reinforced stranded wire is provided with a untwisting fixing tool at at least one of both ends, the tension force of the tense continuous fiber reinforced stranded wire is applied to the first concrete girder structure and the second concrete girder structure. It can be efficiently transmitted to both structures of objects. The untwisted fixing tool may be provided at both ends of the continuous fiber reinforced stranded wire. Further, the untwisted fixing tool may be provided only at one end of the continuous fiber reinforced stranded wire. On the other side of the case, the fixing length is 50 to 60 times the diameter of the continuous fiber reinforced stranded wire, and this is called a straight fixing tool. In that case, the fixing length of the linear fixing tool is longer than that of the untwisted fixing tool, but even in that case, the tension force should be efficiently transmitted to both the first concrete girder structure and the second concrete girder structure. Can be done. The straight fixing tool is economically cheaper than the untwisting fixing tool, but since prestress cannot be introduced into the concrete girder structure of the straight fixing length part, the untwisting fixing tool is selected by design. You just have to decide whether to use the ingredients at one end or both ends.

In one embodiment, both ends of the continuous fiber reinforced stranded wire are outside the sheath embedded in the first concrete girder structure and outside the sheath embedded in the second concrete girder structure, respectively. Both ends of the sheath are embedded in the concrete constituting the first concrete girder structure and the concrete constituting the second concrete girder structure, respectively. This structure can be adopted when the first and second concrete girder structures are made by the on-site casting method (a method of installing a formwork and placing concrete at the site).

In another embodiment, both ends of the continuous fiber reinforced stranded wire are placed in a sheath embedded in the first concrete girder structure and in a sheath embedded in the second concrete girder structure, respectively. It is inserted and fixed to the sheath by a time-curing material such as cement grout filled in the sheath. This structure is adopted when the first and second concrete girder structures are precast members. A precast member is a member that is manufactured by performing a series of processes such as formwork installation, concrete placement, curing, and formwork demolding at a precast factory, not at the site.

Preferably, the continuous fiber reinforced stranded wire is made by twisting a plurality of continuous fiber bundles, and the untwisted fixing tool at at least one end of the continuous fiber reinforced stranded wire has the continuous fiber bundle over a predetermined length. The space formed by untwisting the fibers is filled, cured, and cured with a time-curing material such as cement grout.

By untwisting the twist of multiple continuous fiber bundles (untwisting) and filling it with a time-curing material such as cement grout, the diameter is gradually increased from both sides to the center. It can be used as a fixing tool. Higher fixing rigidity can be exhibited as compared with the case where another member such as a metal sleeve is fixed to the continuous fiber reinforced stranded wire as a fixing tool. In addition, the fixing structure can be manufactured compactly and economically. The untwisted fuser, which is made by twisting the stranded wire and filling it with a time-curing material, has a remarkable uneven shape on its surface, which improves the adhesion performance between concrete and grout material and effectively fixes it. Can be expected. The improvement of the fixing performance contributes to the efficient transmission of the tension force from the tensioned continuous fiber reinforced stranded wire to the first and second concrete girder structures and the supporting reaction force body between them.

Preferably, the supporting reaction force is cast-in-place concrete or non-shrink cement mortar that fills the gap between the first concrete girder structure and the second concrete girder structure. It is possible to form a supporting reaction force body having a shape along the first and second concrete girder structures.

The present invention also provides a method for introducing prestress. The method according to the present invention is provided with a first concrete girder structure in which one end of a continuous fiber reinforced stranded wire surrounded by a sheath is fixed, and the first concrete girder structure is provided with a untwisted fixing tool at at least one of both ends and surrounded by a sheath. The second concrete girder structure in which the other end of the continuous fiber reinforced stranded wire is fixed is installed with a gap, and the first concrete girder structure and the second concrete girder structure are installed. A jack is installed in the gap between the concrete, and the continuous fiber reinforced stranded wire is tensioned by expanding the gap with the jack, and the tension of the continuous fiber reinforced stranded wire is maintained, and the first concrete girder structure is maintained. A supporting reaction force that supports a force that brings the object and the second concrete girder structure closer to each other fills the gap between the first concrete girder structure and the second concrete girder structure. be.

Both ends of the continuous fiber reinforced stranded wire are previously fixed to the first and second concrete girder structures. By widening the gap between the first and second concrete girder structures, the continuous fiber reinforced stranded wire can be strained. When the continuous fiber reinforced stranded wire is tensioned, the continuous fiber reinforced stranded wire is not fixed by utilizing the taper effect of the wedge like the PC steel strand, so that the continuous fiber reinforced stranded wire is not tightened from the circumferential direction. Therefore, the continuous fiber reinforced stranded wire is not damaged.

It is a perspective view of the prestressed concrete girder by cast-in-place concrete of 1st Example. It is a perspective view of the prestressed concrete girder by the precast concrete of the 2nd Example. It is a perspective view of the prestressed concrete girder by the precast concrete of the 3rd Example. The untwisted fixing tool is shown. (A) to (E) are prestress introduction steps in cast-in-place concrete girders. (A) to (E) Prestress introduction steps in precast concrete girders. It is a plan view of a prestressed concrete girder.

FIG. 1 shows the prestressed concrete girder 1 of the first embodiment, and shows a state when prestress is introduced into the prestressed concrete girder 1 in the cast-in-place concrete girder in the direction of the bridge axis.

The prestressed concrete girder 1 includes a concrete girder 10A having a short length in the bridge axis direction and a concrete girder 10B having a long length in the bridge axis direction arranged in the bridge axis direction with a gap G. As will be described later, when prestress is introduced into the prestressed concrete girder 1, the gap G between the concrete girder 10A and the concrete girder 10B is widened, and at this time, the concrete girder 10A having a short length in the bridge axis direction is expanded. However, it moves away from the concrete girder 10B, which has a long length in the direction of the bridge axis. The concrete girder 10B, which has a long length in the direction of the bridge axis, does not move. The concrete girder 10A that moves when prestress is introduced is called "movable girder 10A", and the concrete girder 10B that does not move is called "fixed girder 10B".

The movable girder 10A and the fixed girder 10B both have a π-shaped cross section, for example, and are a flat plate-shaped upper flange (floor slab) 11 installed horizontally and downward from both sides of the bottom surface of the upper flange 11. It is provided with a pair of extending webs 12 and a lower flange 13 integrally formed at the lower end of the web 12. The prestressed concrete girder 1 (movable girder 10A and fixed girder 10B) is a so-called cast-in-place concrete girder, which is constructed on-site by placing concrete in a formwork to be assembled on-site. That is, the upper flange 11, the web 12, and the lower flange 13 of the movable girder 10A and the fixed girder 10B are integrally molded using concrete at the site.

The gap G between the movable girder 10A and the fixed girder 10B is provided to introduce prestress to the prestressed concrete girder 1 including the movable girder 10A and the fixed girder 10B, and is finally provided as described later. Filled with concrete or non-shrink mortar. Asphalt (not shown) may be paved on the upper flange 11 of the movable girder 10A and the fixed girder 10B, including the gap G filled with concrete or non-shrink mortar.

Inside the movable girder 10A and the fixed girder 10B, an elongated tubular sheath 45 made of, for example, polyethylene extending in the direction of the bridge axis is embedded, respectively. The sheath 45 embedded in the movable girder 10A and the sheath 45 embedded in the fixed girder 10B are equipped with a plurality of sheaths required for design with a gap G, and prestress is introduced in these sheaths 45. A continuous fiber reinforced stranded wire 40 used as a tensioning material is passed through. The plurality of continuous fiber reinforced stranded wires 40 required in the design have a length over almost the entire length of the movable girder 10A and the fixed girder 10B installed with a gap G in the bridge axial direction, and are fixed to the movable girder 10A. It is also continuously installed in the gap G between the girders 10B.

Although details will be described later, untwisted fixing tools 43 are formed on both ends of the continuous fiber reinforced stranded wire 40 located on the outside of the sheath 45, and the untwisted fixing tools 43 at one end are made of cast-in-place concrete. The untwisted fixing tool 43 at the other end is fixed to the movable girder 10A to be constructed, and to the fixed girder 10B, which is also constructed from cast-in-place concrete, in the concrete of each girder (10A, 10B). In FIG. 1, the untwisted fixing tool 43 is emphasized (larger than the actual size) for the sake of clarity. Further, in FIG. 1, for the sake of clarity, one sheath 45 is embedded in each of one lower flange 13 of the movable girder 10A and one lower flange 13 of the fixed girder 10B, and these sheaths 45. The continuous fiber reinforced stranded wire 40 passed through is shown. A plurality of sheaths 45 are embedded in the movable girder 10A and the fixed girder 10B, and a continuous fiber reinforced stranded wire 40 is passed through each of the plurality of sheaths 45. That is, not only one lower flange 13 but also the other lower flange 13, the pair of webs 12, and the upper flange 11 have sheaths 45 extending in the direction of the bridge axis embedded at intervals from each other. The continuous fiber reinforced stranded wire 40 is passed through the inside. Generally, dozens of continuous fiber reinforced stranded wires 40 are provided in the prestressed concrete girder 1.

Although the details will be described later, the jack 50 installed in the gap G between the movable girder 10A and the fixed girder 10B is used to widen the gap G between the movable girder 10A and the fixed girder 10B, whereby the continuous fiber reinforced stranded wire is expanded. Tension force (tensile force) is introduced in 40. After concrete or non-shrink mortar is placed and cured in the gap G between the movable girder 10A and the fixed girder 10B while maintaining the tension, the compressive strength is developed, and then the jack 50 is removed. By filling the gap G between the movable girder 10A and the fixed girder 10B and expressing the strength, a structure that bears the reaction force of the tension force is constructed. Hereinafter, this is referred to as a supporting reaction force body. As a result, prestress in the direction of the bridge axis is introduced into the movable girder 10A, the fixed girder 10B, and the supporting reaction force body between them. In FIG. 1, one jack 50 is shown for the sake of clarity, but as for the jack 50, a plurality of jacks 50 are actually installed.

FIG. 2 shows the prestressed concrete girder 2 of the second embodiment, and shows a state when prestress is introduced into the prestressed concrete girder 2 to which the precast block (segment) is applied in the direction perpendicular to the bridge axis. There is.

The prestressed concrete girder 2 consists of one precast block (segment) 20A and five precast blocks (segments) 20B having a longitudinal direction in the direction of the bridge axis, which are arranged in the direction perpendicular to the bridge axis with a gap between them. include. The number of precast blocks 20B is arbitrary and can be increased or decreased according to the required bridge width.

The precast blocks 20A and 20B both have a T-shaped cross section, for example, a flat plate-shaped upper flange 21 installed horizontally and a flat plate-shaped web extending downward from approximately the center of the bottom surface of the upper flange 21. It is equipped with 22 and a lower flange 23 formed at the lower end of the web 22. The precast block 20A is provided with a recess (described later) for installing the jack 50, which is different from the precast block 20B having no recess.

The precast blocks 20A and 20B are so-called precast members that are manufactured in advance at a precast factory, transported to the site, and joined. It is desirable that precast blocks 20A and 20B have prestress introduced in the direction of the bridge axis in advance, and it is economical to manufacture them by a pretension method using a continuous fiber reinforced stranded wire 40.

Before manufacturing the precast blocks 20A and 20B, a plurality of sheaths 45 are embedded in each upper flange 21 in the direction perpendicular to the bridge axis. Once the precast blocks 20A and 20B have been transported to the construction site, they will be installed at the joints at appropriate intervals in the direction perpendicular to the bridge axis.

Details will be described later, but non-shrink mortar is placed and cured in the gap between the five precast blocks 20B. As a result, the concrete of the upper flange 21 of the five precast blocks 20B is continuous. The precast block 20A becomes a movable girder, and five concrete precast blocks 20B become a fixed girder.

A continuous fiber reinforced stranded wire 40 having untwisted fixing tools 43 at both ends was inserted into the sheath 45 embedded in each of the precast blocks 20A and 20B in the direction perpendicular to the bridge axis, and embedded in the precast block 20A. Cement grout in the gap between the sheath 45 and the untwisted fixing tool 43, and in the gap between the sheath 45 and the untwisted fixing tool 43 embedded in the precast block 20B farthest from the precast block 20A. Is filled. The continuous fiber reinforced stranded wire 40 extending in the direction perpendicular to the bridge axis has the untwisted fixing tool 43 at both ends due to the strength development of the cement grout, one of which is the precast block 20A and the other is the precast block 20A in the sheath 45. It is fixed in the precast block 20B farthest from. The gap G between the precast block 20A and the precast block 20B closest to the precast block 20A is expanded using the jack 50, which creates tension in the continuous fiber reinforced stranded wire 40 extending perpendicular to the bridge axis. be introduced. Since the gap G between the precast block 20A and the precast block 20B is cast, cured, and strengthened on-site by concrete or non-shrink mortar while maintaining tension, the jack 50 is then removed. Prestress is introduced over the entire length in the direction perpendicular to the bridge axis by a series of operations.

FIG. 3 shows a prestressed concrete girder 3 made of precast concrete in the third embodiment, and shows a state when prestress is introduced in the bridge axis direction of the prestressed concrete girder 3.

The prestressed concrete girder 3 includes one precast block 30A and eight precast blocks 30B installed in the direction of the bridge axis with a gap from each other. The number of precast blocks 30B is arbitrary and can be increased or decreased according to the required bridge length.

For example, the cross-sectional shapes of the precast blocks 30A and 30B are so-called box-shaped, with a horizontal flat plate-shaped upper flange 31 and a pair of flat plate-shaped webs 32 extending downward from both sides of the bottom surface of the upper flange 31. A flat plate-shaped lower flange 33 is provided by connecting the lower ends of the flat plate-shaped web 32 to each other and provided in parallel with the upper flange 31. The precast blocks 30A and 30B are also made of concrete, and are so-called precast members that are manufactured in advance at the precast factory and transported to the site, or constructed at the construction site. Although detailed illustration is omitted, a plurality of sheaths 45 extending in the direction of the bridge axis are each embedded in advance in the upper flange 31, the web 32, and the lower flange 33 of the precast blocks 30A and 30B.

Similar to the second embodiment, a non-shrink mortar is placed in the gap between the eight precast blocks 30B, whereby the concrete of the eight precast blocks 30B is made continuous. The precast block 30A becomes a movable girder, and eight continuous precast blocks 30B become a fixed girder.

The continuous fiber reinforced stranded wire 40 having the untwisted fixing tool 43 formed at both ends is inserted into the sheath 45 arranged in a row. At both ends of the continuous fiber reinforced stranded wire 40, cement grout is filled in the gap between the sheath 45 and the untwisted fixing tool 43. At both ends of the continuous fiber reinforced stranded wire 40, one of them becomes a precast block 30A and the other becomes a precast block 30B farthest from the precast block 30A in the sheath 45 due to the strength development of the filled cement grout. ， Each is fixed. The gap G between the precast block 30A and the precast block 30B closest to the precast block 30A is expanded using the jack 50, thereby tensioning the continuous fiber reinforced stranded wire 40 inserted and placed in the bridge axis direction. Power is introduced. Concrete or non-shrink mortar is cast, cured, and strengthened in the gap G between the precast block 30A and the precast block 30B while maintaining tension, so the jack 50 can be removed afterwards. It will be possible. As a result, prestress is introduced over the entire length in the direction of the bridge axis.

The untwisted anchor 43 is preferably formed at both ends of the continuous fiber reinforced stranded wire, depending on the anchoring length (the length of the continuous fiber reinforced stranded wire covered with concrete, or the cement grout filled in the sheath 45. When the length that the continuous fiber reinforced stranded wire is covered) may be long by design, for example, when it is possible to secure a fixing length of about 50 to 60 times the diameter of the continuous fiber reinforced stranded wire, on the other hand. The untwisted fixing tool 43 can be changed to a straight fixing tool. That is, in the third embodiment, instead of the continuous fiber reinforced stranded wire 40 in which the untwisted fixing tool 43 is formed at both ends, the continuous fiber reinforced stranded wire 40 in which the untwisted fixing tool 43 is formed only at one end portion is used. Can be used (FIG. 3 shows a continuous fiber reinforced stranded wire 40 in which the untwisted fixing tool 43 is formed only at one end located at the precast block 30A and the linear fixing tool is formed at the other end. It has been.). This also applies to the first embodiment and the second embodiment.

FIG. 4 shows an enlarged portion of one end of the continuous fiber reinforced stranded wire 40.

The continuous fiber reinforced stranded wire 40 is composed of one core wire 41 and a plurality of lateral wires 42 twisted around the core wire 41. When viewed in cross section (not shown), the continuous fiber reinforced stranded wire 40, the core wire 41, and the lateral wire 42 all have an almost circular shape. Further, when viewed in cross section, the continuous fiber reinforced stranded wire 40 has a core wire 41 arranged at the center thereof, and a plurality of side wires 42 are located so as to surround the core wire 41. The continuous fiber reinforced stranded wire 40 has a diameter of, for example, about 5 mm to 30 mm.

The core wire 41 and the side wire 42 are both resin-containing fiber bundles in which a large number of continuous carbon fibers impregnated with a thermosetting resin or a thermoplastic resin, for example, tens of thousands of long continuous carbon fibers are bundled in a circular cross section. The entire continuous fiber reinforced stranded wire 40 contains hundreds of thousands of carbon fibers. Each of the carbon fibers is very fine, for example with a diameter of 5 μm to 7 μm. It can be said that the continuous fiber reinforced stranded wire 40 is made of carbon fiber reinforced plastics (Carbon Fiber Reinforced Plastics). Aramid fiber or glass fiber may be used instead of carbon fiber. As the thermosetting resin, for example, an epoxy resin or a vinyl ester resin is used. For example, polycarbonate or polyvinyl chloride is used as the thermoplastic resin.

The untwisting fixing tool 43 untwists the side wires 42 constituting the continuous fiber reinforced stranded wire 40 over a predetermined length (untwisting section L) (untwisting the side wires 42), and the gap formed by the untwisting (untwisting). The space) is filled with resin mortar or cement mortar 7. Prior to untwisting, both ends of the untwisting section L are bound using a binding band 6. The plurality of lateral lines 42 constituting the continuous fiber reinforced stranded wire 40 in the untwisted section L sandwiched by the binding band 6 are untwisted, and the plurality of untwisted lateral lines 42 are pulled outward, thereby unraveling. In the twisted section L, a gap is formed between the core wire 41 and the lateral line 42, and between the lateral wires 42. The resin mortar or cement mortar 7 is injected into the formed gap using an injection device. The resin mortar or cement mortar 7 is cured after a predetermined time. The compressive strength of the resin mortar or cement mortar 7 is about 30 to 60 N / mm ² , and even if the continuous fiber reinforced stranded wire 40 is strongly tensioned, the diameter of the untwisted fixing tool 43 does not decrease.

The length of the untwisted section L is preferably 5 times or more, for example, about 5 to 20 times, preferably about 7 to 20 times the diameter D1 of the continuous fiber reinforced stranded wire 40. Further, it is desirable that the diameter D2 of the untwisted fixing tool 43 (the diameter of the cross section of the thickest portion of the untwisted fixing tool 43) is about 1.2 to 2.6 times the diameter D1 of the continuous fiber reinforced stranded wire 40. By using the continuous fiber reinforced stranded wire 40 equipped with the untwisted fixing tool 43 having such a large diameter at the end, both ends of the continuous fiber reinforced stranded wire 40 can be made of concrete under a short fixing length. It can be firmly fixed to the digits 1 to 3.

5 (A) to 5 (E) show a step of fixing a continuous fiber reinforced stranded wire 40 to a cast-in-place concrete girder and using the continuous fiber reinforced stranded wire 40 to introduce prestress to the movable girder 10A and the fixed girder 10B (see FIG. 1). Shows.

With reference to FIG. 5A, a formwork 61 for the movable girder 10A and a formwork 62 for the fixed girder 10B are constructed at the site with a gap G corresponding to the dimensions of the jack 50 described later. A sheath 45 is installed in each of the formwork 61 and 62, and a continuous fiber reinforced stranded wire 40 is inserted into the sheath 45. The untwisted fuser 43 at both ends of the continuous fiber reinforced stranded wire 40 is located on the outside of the sheath 45.

With reference to FIG. 5B, after closing the end of the sheath 45 with the seal 47, concrete is poured into the formwork 61 and 62 and cured. Since the end of the sheath 45 is sealed by the seal 47, concrete does not flow into the sheath 45 and remains hollow, and the continuous fiber reinforced stranded wire 40 inserted in the sheath 45 is cast. It is separated from the concrete. After the concrete develops the specified strength, the formwork 61 and 62 are removed. The untwisted fixing tool 43 at both ends of the continuous fiber reinforced stranded wire 40 completes the movable girder 10A and the fixed girder 10B fixed in concrete, respectively.

A recess 51 is formed on the surface of the movable girder 10A facing the fixed girder 10B (the formwork 61 has a shape forming the recess 51 in the movable girder 10A). The jack 50 is installed in the recess 51 with reference to FIG. 5 (C). By jacking up, the movable girder 10A moves away from the fixed girder 10B. The width of the gap G between the movable girder 10A and the fixed girder 10B is widened from W1 to W2 (W2> W1). Tension force is introduced into the continuous fiber reinforced stranded wire 40 in which the untwisted fixing tool 43 is fixed to each of the movable girder 10A and the fixed girder 10B. The hydraulic pressure of the jack 50 is controlled and the amount of elongation of the continuous fiber reinforced stranded wire 40 is controlled in order to apply an appropriate tension force to the continuous fiber reinforced stranded wire 40.

With reference to FIG. 5D, after the end of the sheath 45 facing the gap G is sealed by the seal 47, the jack 50 is installed while maintaining the tension of the continuous fiber reinforced stranded wire 40 by the jack 50. Concrete or non-shrink mortar 71 is placed in the gap G between the movable girder 10A and the fixed girder 10B and cured, except for the range.

With reference to FIG. 5 (E), the jack 50 is removed after the concrete or non-shrink mortar 71 develops a predetermined strength, and the concrete or non-shrink mortar 72 is placed in the area where the jack 50 is installed and cured. do. The construction of the prestressed concrete girder 1 is completed when the concrete or the non-shrink mortar 72 develops a predetermined strength. The concrete or non-shrink mortar 71, 72 that fills the gap G between the movable girder 10A and the fixed girder 10B becomes a supporting reaction force body that bears the reaction force of the tension introduced into the movable girder 10A and the fixed girder 10B. ..

Since tension is introduced into the continuous fiber reinforced stranded wire 40 fixed to each of the movable girder 10A and the fixed girder 10B, prestress is applied to the movable girder 10A and the fixed girder 10B, and the supporting reaction forces 71 and 72. be introduced.

6 (A) to 6 (E) show that the continuous fiber reinforced stranded wire 40 is fixed to the precast block 20A and the plurality of precast blocks 20B (see FIG. 2), and the continuous fiber reinforced stranded wire 40 is used to precast the precast blocks 20A and 20B. It shows the process of introducing stress. The same process is performed for the prestressed concrete girder 3 (see FIG. 3) of the third embodiment including the precast block 30A and the plurality of precast blocks 30B.

With reference to FIG. 6A, a precast block 20A in which the sheath 45 is pre-embedded and a plurality of precast blocks 20B in which the sheath 45 is pre-embedded (here, four precast blocks 20B are shown) are ， Installed with a gap at the construction site. A urethane rubber or rubber ring seal 48 having an inner diameter along the outer diameter of the sheath 45 is arranged between the precast blocks 20B, and the sheath 45 in the precast blocks 20B adjacent to each other by the ring seal 48 is arranged. The seals are connected to each other. The gap between the precast blocks 20B is, for example, 2 to 5 cm, and it is preferable that the distance is such that the ring seal 48 is slightly crushed. A gap G corresponding to the size of the jack 50 is secured between the precast block 20A and the precast block 20B closest to the precast block 20A.

With reference to FIG. 6B, the gap between the precast blocks 20B on which the ring seal 48 is installed is filled and cured with the non-shrink mortar 5, whereby the concrete of the plurality of precast blocks 20B is continuously formed. (Multiple precast blocks 20B are fixed digits). Further, the continuous fiber reinforced stranded wire 40 is inserted into the sheath 45 from the precast block 20A to the plurality of continuous precast blocks 20B. The untwisted fixing tool 43 at both ends of the continuous fiber reinforced stranded wire 40 is also put in the sheath 45. The untwisted fixing tool 43 at one end is located in the sheath 45 embedded in the precast block 20A. The twisted fixing tool 43 at the other end is located in the sheath 45 embedded in the precast block 20B farthest from the precast block 20A.

The gap between the sheath 45 embedded in the precast block 20A and the untwisted fixing tool 43, and the gap between the sheath 45 embedded in the precast block 20B farthest from the precast block 20A and the untwisted fixing tool 43. Is filled with cement grout 8 and cured. Both ends of the sheath 45 to be filled with the cement grout 8 are sealed with seals 47 in advance so that the cement grout 8 is filled only around the untwisted fixing tool 43. Due to the strength development of the cement grout 8, the untwisted fixing tools 43 at both ends of the continuous fiber reinforced stranded wire 40 are fixed to the precast block 20A and the precast block 20B farthest from the precast block 20A, respectively.

With reference to FIG. 6C, the jack 50 is installed in the recess 51 formed in advance in the precast block 20A, and by jacking up, the precast block 20A moves away from the precast block 20B. The width of the gap G is expanded from W1 to W2, and tension is introduced into the continuous fiber reinforced stranded wire 40.

With reference to FIG. 6D, after the end of the sheath 45 facing the gap G is sealed by the seal 47, the jack 50 is installed while maintaining the tension of the continuous fiber reinforced stranded wire 40 by the jack 50. Concrete or non-shrink mortar 71 is placed in the gap G between the precast block 20A and the prestress block 20B and cured, except for the above range. With reference to FIG. 6E, after the concrete or non-shrink mortar 71 develops a predetermined strength, the jack 50 is removed, and the concrete or non-shrink mortar 72 is placed in the area where the jack 50 is installed. Cure. The construction of the prestressed concrete girder 2 is completed when the concrete or the non-shrink mortar 72 (supporting reaction force 71, 72) develops a predetermined strength.

The continuous fiber reinforced stranded wire 40 fixed to each of the precast block 20A and the prestress block 20B farthest from the precast block 20A is integrated with the precast block 20A because tension is introduced. Prestress is introduced into the plurality of precast blocks 20B and the supporting reaction forces 71 and 72 between them.

The width of the gap G between the two concrete girders for introducing prestress depends on the dimensions of the installed jack 50, as described above. A flat jack may be used to narrow the width of the gap G between the two concrete bridge girders. FIG. 7 shows a state in which the flat jack 55 is installed in the gap G between the two concrete girders 1A and 1B.

1,2,3 Prestressed concrete girder 5 Non-shrink mortar 7 Resin mortar or cement mortar 8 Cement grout
10A movable girder
10B fixed girder
11, 21, 31 Upper flange
12, 22, 32 web
13, 23, 33 Lower flange
20A, 20B, 30A, 30B precast block
40 Continuous fiber reinforced stranded wire
41 Core line
42 lateral line
43 Untwisted fixing tool
45 Sheath
50 jack
55 flat jack
71,72 Supporting reaction force

Claims (7)

First concrete girder structure with a buried sheath,
A second concrete girder structure provided with a gap between the first concrete girder structure and a sheath in which a sheath is embedded.
A twist fixing tool is provided on at least one of both ends, and the sheath is passed through a sheath embedded in the first concrete girder structure and a sheath embedded in the second concrete girder structure, and one end thereof is formed. A tensioned continuous fiber reinforced stranded wire with the other end fixed in the first concrete girder structure and the other end in the second concrete girder structure, as well as the first concrete girder structure and the second concrete girder structure. Tension force in the direction of bringing the first concrete girder structure and the second concrete girder structure closer to each other, which is provided in the gap between the concrete girder structures of the above and is generated by the continuous fiber reinforcing stranded wire in the tension state. Equipped with a supporting reaction force to support
The tension force of the continuous fiber reinforced stranded wire in the tension state is introduced into the first concrete girder structure, the second concrete girder structure and the supporting reaction force body as prestress.
Prestressed concrete girder. Both ends of the continuous fiber reinforced stranded wire protrude from the sheath embedded in the first concrete girder structure and the sheath embedded in the second concrete girder structure, respectively.
Both ends protruding outside the sheath are embedded in the concrete constituting the first concrete girder structure and the concrete constituting the second concrete girder structure, respectively.
The prestressed concrete girder according to claim 1. Both ends of the continuous fiber reinforced stranded wire are inserted into the sheath embedded in the first concrete girder structure and the sheath embedded in the second concrete girder structure, respectively. It is fixed to the sheath by the time-curing material filled in the sheath.
The prestressed concrete girder according to claim 1. The above-mentioned continuous fiber reinforced stranded wire is made by twisting a plurality of continuous fiber bundles.
The untwisted fixing tool at at least one end of the continuous fiber reinforced stranded wire fills the space formed by untwisting the continuous fiber bundle over a predetermined length with a time-curing material and cures it. Is a thing,
The prestressed concrete girder according to any one of claims 1 to 3. The supporting reaction force is cast-in-place concrete or non-shrink cement mortar that fills the gap between the first concrete girder structure and the second concrete girder structure.
The prestressed concrete girder according to any one of claims 1 to 4. A first concrete girder structure in which one end of a continuous fiber reinforced stranded wire surrounded by a sheath is fixed by providing a detwisting fixing tool on at least one of both ends, and the continuous fiber reinforcement surrounded by the sheath. A second concrete girder structure with the other end of the stranded wire fixed was installed with a gap.
A jack is installed in the gap between the first concrete girder structure and the second concrete girder structure.
By expanding the gap with the jack, the continuous fiber reinforced stranded wire is strained.
The first concrete girder structure and the second concrete girder structure are supported by a supporting reaction force body that supports the tension in the direction of bringing the first concrete girder structure and the second concrete girder structure closer to each other while maintaining the tension of the continuous fiber reinforcing stranded wire. Fill the gap between the concrete girder structure and the second concrete girder structure above.
Prestress introduction method. The above-mentioned continuous fiber reinforced stranded wire is made by twisting a plurality of continuous fiber bundles.
The untwisted fixing tool at at least one end of the continuous fiber reinforced stranded wire fills the space formed by untwisting the continuous fiber bundle over a predetermined length with a time-curing material and cures it. Is a thing,
The prestress introduction method according to claim 6.

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