JP2024067942A - Prestress introduction unit - Google Patents

Abstract

[Problem] To provide a prestress introduction unit capable of smoothly releasing a reaction force in a reaction body. [Solution] A prestress introduction unit 1 according to the present invention comprises a PC steel bar 2, anchoring plates 3a, 3b, cylindrical reaction members 4a, 4b, and a reaction force release mechanism 5. The reaction force release mechanism 5 comprises wedge-shaped members 11a, 11b, clamping members 12, 13 that clamp the wedge-shaped members from the sides, and two sets of bolts 14 and nuts 15 that interconnect the clamping members. The bolts 14, nuts 15, and clamping members 12, 13 are configured such that, by turning each nut 15 in the loosening direction, the wedge-shaped members 11a, 11b are moved relatively to each other so that the overall dimensions of the wedge-shaped members 11a, 11b along the material axis 10 become shorter. [Selected Figure] Figure 5

Description

The present invention relates to a prestress introduction unit used in constructing prestressed concrete.

Prestressed concrete (PC) can be broadly divided into pretensioning and posttensioning, depending on when the prestress is introduced. The pretensioning method involves introducing tensile force into the tendons by taking a reaction force from a reaction table to which the tendons are attached, pouring concrete in this state, and then removing the tendons from the reaction table after waiting for the concrete to develop its strength. Therefore, it is basically used when manufacturing precast concrete (PCa) components in a factory.

On the other hand, the post-tensioning method allows the tendons to be freely positioned within the concrete, making it possible to easily introduce large prestress into cast-in-place concrete of various shapes, and is widely used in bridge construction and other construction sites. However, it can be disadvantageous in terms of construction time and cost because it takes time to position the sheath, which is complicated by rebar work, and it requires space and scaffolding to install hydraulic jacks.

In this situation, a method has been developed to introduce prestress into concrete by transporting and installing a unit in which tension has already been applied to the tensioning material while the tension is still maintained, and then releasing the tension after the concrete has been poured and has had time to develop its strength. This method makes it possible to use the pretensioning method at bridge construction sites and other construction sites.

The above prestress introduction units include a type in which a reaction member inserted inside a hollow tension member is used to introduce tension into the tension member, and after the poured concrete has hardened, prestress is introduced into the concrete through adhesion to the periphery of the tension member. In addition, there is also a type in which a reaction body made of a hollow material is used to introduce tension into the tension member inserted inside, and after the poured concrete has hardened, prestress is introduced into the concrete through support pressure from a fixing device attached to the end of the tension member. As an example of the latter, Patent Document 1 discloses a unit in which two reaction bodies made of hollow materials are arranged side by side so that their material axes are aligned along a common axis, and tension is introduced into the tension members by pushing them apart in the direction away from each other when they face each other, and the tension is released by loosening them in the opposite direction to introduce prestress into the concrete.

JP 2005-325518 A JP 2020-147913 A

In the prestress introduction unit 1 described in Patent Document 1, the PC steel rod 2 corresponds to the tension material, and the reaction sheath tubes 5 and 6 correspond to the two reaction bodies, but in the case of this unit, a tensile force is generated in the PC steel rod 2 while a reaction force is taken from the reaction tables 10 and 10, and at the same time, the special nut 7 screwed onto the reaction sheath tube 6 is turned to bring the pressing flange portion 7b formed at its tip into contact with the end face of the reaction sheath tube 5, so that the reaction force supported by the reaction tables 10 and 10 is transferred to the reaction sheath tubes 5 and 6 as a compressive force.

However, when turning the special nut 7 to release the tensile force introduced into the PC steel bar 2, a large frictional force is generated between the pressure flange portion 7b and the end face of the reaction sheath tube 5, which can make it difficult to perform the release operation on site.

Incidentally, Patent Document 2 discloses an invention that solves the problem of Patent Document 1, but the technical idea for releasing the tensile force is fundamentally different from that of the present invention.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a prestress introduction unit that can smoothly release the reaction force generated in the reaction body.

In order to achieve the above object, as described in claim 1, the prestress introduction unit of the present invention comprises a PC steel member, a pair of anchoring members attached in the vicinity of each end of the PC steel member, a pair of tubular reaction members arranged coaxially with the PC steel member and through which the PC steel member is inserted so that a reaction force for introducing a tensile force into the PC steel member is transmitted to each of the anchoring members or the vicinity of each end of the PC steel member, and a reaction force release mechanism capable of releasing the reaction force generated in the pair of tubular reaction members by bringing the opposing end portions of the pair of tubular reaction members closer to each other, and the reaction force release mechanism is composed of a pair of wedge-shaped members each having a through opening for passing the PC steel member through and each having an inclined surface inclined with respect to a plane perpendicular to the material axis of the PC steel member, and arranged so that the inclined surfaces are in contact with each other, and a relative movement adjustment means for freely adjusting the relative movement amount of the pair of wedge-shaped members along the direction perpendicular to the material axis,
The pair of wedge-shaped members have pressure-loading surfaces located on the opposite sides of each of the inclined surfaces, through which compressive forces are transmitted from each of the opposing ends, and each of the through openings is formed in a notch or long hole shape so that the relative movement of each of the inclined surfaces is not restricted when one of the inclined surfaces moves relative to the other by sliding against the other, and a convex portion is formed on one of the inclined surfaces and a concave portion or convex portion that can engage with the convex portion is formed on the other of the inclined surfaces so that relative rotation around the material axis is restricted.

The prestress introduction unit according to the present invention has stepped ends on the opposing sides of the pair of wedge-shaped members, with each inclined surface being formed by a protruding side inclined surface formed on the end face of the protruding portion and a non-protruding side inclined surface formed on the end face of the non-protruding portion, and each of the protruding portions is made into the convex portion.

In addition, the prestress introduction unit according to the present invention has the relative movement adjustment means configured with a pair of clamping members that clamp the pair of wedge-shaped members from the sides of the material shaft, and a connecting mechanism that connects the pair of clamping members to each other.

The prestress introduction unit according to the present invention, as described in claim 4, comprises a PC steel member, a pair of anchoring members attached in the vicinity of each end of the PC steel member, a pair of tubular reaction members arranged coaxially with the PC steel member and through which the PC steel member is inserted so that a reaction force for introducing a tensile force into the PC steel member is transmitted to each of the anchoring members or the vicinity of each end of the PC steel member, and a reaction force release mechanism capable of releasing the reaction force generated in the pair of tubular reaction members by bringing the opposing end portions of the pair of tubular reaction members closer to each other, and the reaction force release mechanism is composed of a pair of wedge-shaped members each having a through opening for passing the PC steel member through and each having an inclined surface inclined with respect to a plane perpendicular to the material axis of the PC steel member, and arranged so that the inclined surfaces abut against each other, and a relative movement adjustment means for freely adjusting the relative movement of the pair of wedge-shaped members in the direction perpendicular to the material axis,
The pair of wedge-shaped members have pressure-loading surfaces on the opposite sides of the inclined surfaces, through which compressive forces are transmitted from the opposing ends, and the through openings are formed in a notch or slot shape so that the relative movement of the inclined surfaces is not restricted when one of the inclined surfaces slides over the other.
the relative movement adjustment means is composed of a pair of clamping members that clamp the pair of wedge-shaped members from the sides of the material shaft, and a connecting mechanism that connects the pair of clamping members to each other,
The pair of wedge-shaped members and the pair of clamping members are configured so that the cross sections of the pair of wedge-shaped members are non-circular and mating recesses are formed facing the pair of clamping members so as to abut their peripheral surfaces, thereby restricting relative rotation of the pair of wedge-shaped members about the material axis.

The prestress introduction unit according to the present invention is configured by disposing intermediate pedestals, each having a pedestal-side through opening for passing the PC steel material, between each of the opposing ends and the pair of wedge-shaped members, and forming each of the pedestal-side through openings in the shape of a notch or a long hole so that the relative movement of the pair of wedge-shaped members is not restricted.

[Action of the present invention]
In the prestress introduction unit of the present invention, as in the prior art, the opposing ends of a pair of tubular reaction members are brought closer together to release the compressive force generated in the pair of tubular reaction members as a reaction force to the tensile force to be introduced into the PC steel material, but the reaction force release mechanism of the present invention is composed of a pair of wedge-shaped members, each of which has a through opening for passing the PC steel material through, and a relative movement adjustment means for freely adjusting the relative movement of the pair of wedge-shaped members in the direction perpendicular to the material axis of the PC steel material.

When prestressing concrete in this configuration, the above-mentioned prestress introduction unit in which tension is introduced into the PC steel is placed in the concrete pouring area, and then concrete is poured into the concrete pouring area while being careful not to fill the area around the reaction force release mechanism with concrete, and the concrete is allowed to develop strength. After that, the pair of wedge-shaped members are moved relative to each other using the relative movement adjustment means so that the overall dimension of the pair of wedge-shaped members along the material axis is shortened.

In this way, the overall dimensions of the wedge-shaped member are shortened, and the opposing ends of the pair of cylindrical reaction members come closer together, causing the compressive force generated in each cylindrical reaction member to disappear. As a result of the disappearance of the compressive force as a reaction force, the tensile force introduced into the PC steel is transmitted as a compressive force via the pair of anchoring members to the surrounding concrete, and the concrete functions as prestressed concrete.

Here, in the past, the compressive force acting on a pair of cylindrical reaction members was released at the contact surfaces of the mechanical parts, such as nuts, with which they act, and this could cause excessive frictional forces to be generated at the contact surfaces of the mechanical parts, making the release operation difficult. However, in the present invention, a significant portion of the compressive force is supported by the inclined surfaces of the wedge-shaped members, and a component force according to the inclination angle is supported by the relative movement adjustment means, which adjusts the relative movement of the pair of wedge-shaped members, thereby releasing the compressive force.

In other words, in the prestress introduction unit of the present invention, the operation of releasing the compressive force acting on the pair of cylindrical reaction members is performed not at the location where the compressive forces act directly on each other, but at the location where the component force acting on the inclined surfaces of the pair of wedge-shaped members acts. This configuration eliminates the concern that the frictional force acting on the contact surfaces of the machine parts becomes excessive, making the release operation difficult, as was the case in the conventional case.

[Actions of the present invention (claims 1 to 3)]
In particular, in each of the inventions according to claims 1 to 3, a convex portion is formed on one of the pair of wedge-shaped members and a concave or convex portion which engages with the convex portion is formed on the other so that the relative rotation of the pair of wedge-shaped members about the material axis is restricted. This eliminates concerns about the pair of wedge-shaped members rotating relatively about the material axis of the PC steel material, making it possible to carry out the above-mentioned release operation more reliably.

The following combinations are possible in which a convex portion is provided on one of the pair of wedge-shaped members and a concave portion or a convex portion is provided on the other of the pair of wedge-shaped members:
(a) Providing a protrusion on one wedge-shaped member and a recess on the other wedge-shaped member
(b) It is possible to provide a convex portion on one wedge-shaped member and a convex portion on the other wedge-shaped member, and a stepped end portion is provided on each of the opposing sides of a pair of wedge-shaped members, and each of the inclined surfaces is constituted by a protruding-side inclined surface formed on the end face of the protruding portion and a non-protruding-side inclined surface formed on the end face of the non-protruding portion, and each of the protruding portions is configured as the convex portion. This is one specific example.

The relative movement adjustment means in each of the inventions of claims 1 and 2 may have any specific configuration as long as it can move the opposing ends of the pair of cylindrical reaction members closer together by relatively moving the pair of wedge-shaped members so that the overall dimension of the pair of wedge-shaped members along the material axis is shortened, but a typical example is one that is configured with a pair of clamping members that clamp the pair of wedge-shaped members from the sides of the material axis and a connecting mechanism that connects the pair of clamping members to each other.

In such a configuration, if the connecting mechanism is configured with, for example, a bolt and a nut, the pair of wedge-shaped members can be moved relative to one another by loosening the nut so that the pair of clamping members move away from each other, thereby shortening the overall dimension of the pair of wedge-shaped members along the material axis.

[Action of the present invention (Claim 4)]
In addition, in the invention of claim 4, the pair of wedge-shaped members and the pair of clamping members are configured so that the cross sections of the pair of wedge-shaped members are non-circular and opposing fitting recesses are formed in the pair of clamping members so as to abut their peripheral surfaces, thereby restricting rotation of each wedge-shaped member about the material axis relative to the pair of clamping members.This prevents each of the pair of wedge-shaped members from rotating relative to the pair of clamping members, and as a result, as with the inventions of claims 1 to 3, there is no concern that the pair of wedge-shaped members will rotate relatively about the material axis of the PC steel material, further increasing the reliability of the above-mentioned release operation.

Examples of a wedge-shaped member with a non-circular cross section include a rectangular cross section and an elliptical cross section.

[Action of the present invention (Claim 5)]
The opposing ends of the cylindrical reaction member in each of the inventions according to claims 1 to 4 may be directly abutted against the respective pressure-bearing surfaces of the pair of wedge-shaped members, but if there is a concern that the abutment of the opposing ends may hinder the relative movement of the wedge-shaped members, a configuration can be adopted in which intermediate bases each having a base-side through opening for passing PC steel material therethrough are disposed between each opposing end and each wedge-shaped member, and each base-side through opening is formed in the shape of a notch or a long hole so that the relative movement of the pair of wedge-shaped members is not restricted.

FIG. 2 is a side view showing the prestress introduction unit 1 according to this embodiment with a tensile force introduced into the PC steel bar 2. FIG. 1A and 1B are diagrams showing the wedge-shaped members 11a and 11b that constitute the prestress introduction unit 1, where (a) is an exploded oblique view, (b) is a side view of the wedge-shaped member 11a, (c) is a front view of the wedge-shaped member 11a as viewed from the direction of line A-A, (d) is a side view of the wedge-shaped member 11b, and (e) is a front view of the wedge-shaped member 11b as viewed from the direction of line B-B. 1A and 1B are exploded perspective views showing the wedge-shaped members 11a and 11b together with their sliding regions and locking regions, where (a) is an exploded perspective view showing the sliding regions hatched, and (b) and (c) are exploded perspective views showing the locking regions hatched, where (b) is a view showing a state in which a compressive force acting as a reaction force to the tensile force of the PC steel bar 2 is generated in the cylindrical reaction members 4a and 4b, and (c) is a view showing the time when the compressive force is released. 1A and 1B are diagrams showing the operation of the prestress introduction unit 1, in which (a) is a detailed side view of the state in which a compressive force acting as a reaction force to the tensile force of the PC steel bar 2 is generated in the tubular reaction members 4a and 4b, (b) is a detailed oblique view of the same, (c) is a detailed side view of the state when the above-mentioned compressive force is released, and (d) is a detailed oblique view of the same. 1 is a side view showing the prestress introduction unit 1 in a state before tensile force is introduced into the PC steel bar 2. FIG. FIG. 2 is an overall perspective view showing how a tensile force is introduced into a PC steel bar 2. 1 is a side view showing how prestress is introduced into concrete using a prestress introduction unit 1. FIG. This figure shows the deck of a bridge to which the prestress-introducing unit 1 is applied when connecting precast concrete members to each other, where (a) is a plan view and (b) is a view seen from the direction of line C-C. A diagram showing the process of replacing a bridge deck using a prestress introduction unit 1. The following figures show the process of replacing the bridge deck, where (a) is a plan view showing the state before the pouring of post-pour concrete, and (b) is a plan view showing the state after pouring. This is a diagram showing the subsequent process of replacing the bridge deck, and is a plan view showing how the precast concrete members 103a, 103b are connected to each other as a result of the release of the compressive force of the tubular reaction members 4a, 4b (the reaction force due to the tensile force of the PC steel bar 2). FIG. 4 is an explanatory diagram showing the operation of the prestress introduction unit 1. 13A and 13B show a pair of wedge-shaped members 311a and 311b relating to a modified example, where (a) is a side view of the wedge-shaped member 311a, (b) is a front view of the wedge-shaped member 311a as viewed from the direction of line D-D, (c) is a side view of the wedge-shaped member 311b, and (b) is a front view of the wedge-shaped member 311b as viewed from the direction of line E-E. 13A and 13B show a pair of wedge-shaped members 511a and 511b relating to another modified example, where (a) is a side view of the wedge-shaped member 511a, (b) is a front view of the wedge-shaped member 511a as viewed from the line F-F direction, (c) is a side view of the wedge-shaped member 511b, and (b) is a front view of the wedge-shaped member 511b as viewed from the line G-G direction. 13A and 13B are diagrams showing wedge-shaped members 711a, 711b and sandwiching members 712, 713 according to a second embodiment, in which (a) is an exploded perspective view and (b) is an exploded front view. 10A and 10B are diagrams showing the operation of the prestress introduction unit in the second embodiment, in which (a) is a detailed side view of the state in which a compressive force acting as a reaction force to the tensile force of the PC steel bar 2 is generated in the tubular reaction members 4a and 4b, (b) is a detailed oblique view of the same, (c) is a detailed side view of the state when the above-mentioned compressive force is released, and (d) is a detailed oblique view of the same. 13A and 13B are diagrams showing wedge-shaped members 811a and 811b and sandwiching members 812 and 813 according to a modified example, in which FIG.

Below, an embodiment of the prestress introduction unit according to the present invention will be described with reference to the attached drawings.

[First embodiment]
1 to 5 are diagrams showing a prestress introduction unit according to this embodiment. As can be seen from these figures, the prestress introduction unit 1 according to this embodiment includes a PC steel bar 2 as a PC steel material, a pair of anchoring plates 3a, 3b as a pair of anchoring members attached near each end of the PC steel bar, a pair of cylindrical reaction members 4a, 4b, and a reaction release mechanism 5.

Here, when a tensile force is introduced into the PC steel rod 2 and a compressive force is generated in each of the cylindrical reaction members 4a, 4b as a reaction force, as shown in Figure 1, the PC steel rod 2 has a total length of _Lp , and each of the cylindrical reaction members 4a, 4b has a total length of _Lr .

The anchor plates 3a and 3b are each circular in shape, and the tensile force previously introduced into the PC steel bar 2 is transmitted to the concrete as a bearing pressure via the opposing surfaces of the anchor plates 3a and 3b, allowing prestress to be introduced into the concrete.

Here, the anchor plate 3b is fixed to one end of the PC steel bar 2 by welding, engagement, screwing, etc., but the anchor plate 3a is designed so that the PC steel bar 2 can be inserted into the insertion hole 31 provided in the anchor plate, and the attachment position to the PC steel bar 2 can be adjusted by screwing the anchor nut 33 into the male screw 32 provided at the other end of the PC steel bar 2.

As can be seen clearly in Figure 2, the cylindrical reaction members 4a, 4b are each constructed from a hollow cylindrical member, and are arranged coaxially with the PC steel rod 2 so that the compressive force, which is the reaction force for introducing a tensile force into the PC steel rod 2, is transmitted to the opposing surfaces of the anchoring plates 3a, 3b via the opposing ends 7a, 7b, respectively, and the PC steel rod 2 is inserted through it.

The reaction force release mechanism 5 is capable of releasing the compressive force acting on the cylindrical reaction members 4a, 4b by bringing the angular pedestals 8a, 8b constituting the opposing ends of the cylindrical reaction members 4a, 4b closer together, and is composed of a pair of wedge-shaped members 11a, 11b, a pair of clamping members 12, 13 that clamp the wedge-shaped members from the sides of the material shaft 10 of the PC steel bar 2, two sets of bolts 14 and nuts 15 as a connecting mechanism that connects the clamping members to each other, and intermediate pedestals 16a, 16b.

As shown in FIG. 3(a), the wedge-shaped members 11a and 11b are formed so that the peripheral surfaces 24a and 24b are roughly cylindrical, and notched through openings 17a and 17b are formed to allow the PC steel rod 2 to pass through. Stepped ends 201a and 201b are provided on the opposing sides, and the opposite sides serve as pressure-bearing surfaces 19a and 19b, to which compressive forces are transmitted from the pedestals 8a and 8b via the intermediate pedestals 16a and 16b.

As can be seen clearly in Figures 3(b) and (c), when viewed from the side opposite the wedge-shaped member 11b, the stepped end 201a has a protruding portion 211a in an inverted J shape that surrounds the through opening 17a, and the end face of the protruding portion 211a is formed with a protruding side inclined surface 212a that is inclined with respect to a plane perpendicular to the material axis 10 of the PC steel bar 2, and the end face of the non-protruding portion 214a adjacent to the protruding portion via the step 213a is provided with a non-protruding side inclined surface 215a that has the same inclination as the above inclination.

Similarly, as can be seen in Figures 3(d) and (e), when viewed from the side opposite the wedge-shaped member 11a, the stepped end 201b has a J-shaped protruding portion 211b surrounding the through opening 17b, and the end face of the protruding portion 211b has a protruding side inclined surface 212b that is inclined with respect to a plane perpendicular to the material axis 10 of the PC steel bar 2, and the end face of the non-protruding portion 214b adjacent to the protruding portion via the step 213b has a non-protruding side inclined surface 215b that has the same inclination as the above inclination.

Here, as shown in FIG. 4(a), the protruding side inclined surface 212a and the non-protruding side inclined surface 215b are configured to move relative to each other by sliding one over the other, and the protruding side inclined surface 212b and the non-protruding side inclined surface 215a are configured to move relative to each other by sliding one over the other, so that the protruding side inclined surface 212b and the non-protruding side inclined surface 215b and the protruding side inclined surface 212a and the non-protruding side inclined surface 215a each function as the inclined surface of the present invention, and the notched through openings 17a, 17b already mentioned are configured so that their relative movement is not restricted.

In FIG. 4(a), the sliding area between the protruding side inclined surface 212a and the non-protruding side inclined surface 215b, and the sliding area between the protruding side inclined surface 212b and the non-protruding side inclined surface 215a are shown by hatching.

On the other hand, as shown in Figures 4(b) and (c), the protruding portion 211a is engaged with the inner circumferential surface 221b of the protruding portion 211b (part of the inner circumferential surface of the through opening 17b) via the step 213a, and the protruding portion 211b is engaged with the inner circumferential surface 221a of the protruding portion 211a (part of the inner circumferential surface of the through opening 17a) via the step 213b, so that the relative rotation of the wedge-shaped members 11a and 11b around the material axis 10 is restricted, and the protruding portions 211a and 211b each function as the convex portion of the present invention.

In addition, in Figures 4(b) and (c), the engagement area between protruding portion 211a and inner circumferential surface 221b of protruding portion 211b, and the engagement area between protruding portion 211b and inner circumferential surface 221a of protruding portion 211a are shown by hatching according to the magnitude of the relative movement of wedge-shaped members 11a and 11b in the direction of the arrows in the figure.

It is desirable to take measures such as applying a lubricant with excellent load resistance or coating with PTFE (polytetrafluoroethylene) to the protruding side inclined surface 212a and the non-protruding side inclined surface 215a of the wedge-shaped member 11a and the protruding side inclined surface 212b and the non-protruding side inclined surface 215b of the wedge-shaped member 11b to minimize friction.

The intermediate pedestals 16a, 16b each have a pedestal-side through opening 25a, 25b for passing the PC steel bar 2 through, and each pedestal-side through opening 25a, 25b is cut out like the through openings 17a, 17b so that the relative movement of the wedge-shaped members 11a, 11b is not restricted.

The intermediate pedestals 16a, 16b serve to reliably transmit the compressive force from the cylindrical reaction members 4a, 4b via the pedestals 8a, 8b to the wedge-shaped members 11a, 11b with a wider acting area, and when the wedge-shaped members 11a and 11b move relative to each other in the direction perpendicular to the material axis 10, they are able to slide on two surfaces, the side of the wedge-shaped members 11a, 11b and the side of the pedestals 8a, 8b, so that the relative movement of the wedge-shaped members 11a, 11b is more reliably achieved.

As with the protruding side inclined surface 212a and the non-protruding side inclined surface 215a of the wedge-shaped member 11a and the protruding side inclined surface 212b and the non-protruding side inclined surface 215b of the wedge-shaped member 11b, it is desirable to reduce friction by applying a lubricant with excellent load resistance or coating with PTFE on both sides of the intermediate bases 16a and 16b.

The clamping members 12, 13 are rectangular parallelepipeds, with curved recesses 20, 22 formed on their opposing inner surfaces, and the peripheral surfaces 24b, 24a of the wedge-shaped members 11b, 11a abut against the curved recesses so that a portion of each wedge-shaped member is fitted into each of them. The clamping member 12 has bolt holes 21, 21 at a position that sandwiches the curved recess 20, and the clamping member 13 has bolt holes 23, 23 at a position that sandwiches the curved recess 22. Bolts 14 are inserted into the two sets of bolt holes 21, 23, and nuts 15 are screwed onto the tips of the bolts.

In addition, the clamping member 12 has a countersink 26 on the surface opposite the curved recess 20, into which the head of the bolt 14 is fitted.

As with the wedge-shaped members 11a, 11b and intermediate seats 16a, 16b, it is desirable to reduce friction by applying a lubricant with excellent load resistance to the curved recesses 20, 22 of the clamping members 12, 13 and the peripheral surfaces 24b, 24a of the wedge-shaped members 11b, 11a or coating them with PTFE.

As can be clearly seen in Figure 5, the connecting mechanism consisting of bolt 14, nut 15 and clamping members 12, 13 is designed to move the wedge-shaped members 11a, 11b relatively along the material axis 10 from a state in which the overall dimension of the members is _Lw (the state in Figures 5(a) and (b)) to a state in which the overall dimension is shortened to a state of _Lw ' (the state in Figures 5(c) and (d)) by turning each nut 15 in the loosening direction, and the bolt 14, nut 15 and clamping members 12, 13 function as a relative movement adjustment means for adjusting the amount of relative movement of the wedge-shaped members 11a, 11b along the perpendicular direction to the material axis 10 of the PC steel bar 2.

To introduce tension to the PC steel bar 2 in the prestress introduction unit 1 according to this embodiment, first, the wedge-shaped members 11a and 11b are abutted against each other so that their through openings 17a and 17b are coaxial with each other at the protruding side inclined surface 212a and the non-protruding side inclined surface 215b, and the protruding side inclined surface 212b and the non-protruding side inclined surface 215a are abutted against each other, and in this state, they are sandwiched by the sandwiching members 12 and 13 and connected by the bolt 14 and the nut 15, thereby assembling the reaction force release mechanism 5 in advance. The intermediate pedestals 16a and 16b may be appropriately inserted and positioned between the wedge-shaped member 11a and the pedestal 8a and between the wedge-shaped member 11b and the pedestal 8b prior to the tension introduction process described later.

After the tensile force is introduced, the total length of the PC steel rod 2 expands to _Lp as explained in FIG. 1, but before the tensile force is introduced, the total length is _Lp '(< _Lp ) as shown in FIG. 6. After the tensile force is introduced, the total length of the cylindrical reaction members 4a, 4b contracts to _Lr , but before the compressive force is generated, the total length is _Lr '(> _Lr ).

Next, as shown in FIG. 7, the PC steel rod 2 with the anchor plate 3b attached to one end is inserted through the cylindrical reaction member 4b, the reaction release mechanism 5, and the cylindrical reaction member 4a in that order, and the male screw 32 at the tip of the PC steel rod is inserted through the insertion hole 31 of the anchor plate 3a, and a nut 33 is provisionally placed on the male screw.

Next, by taking the reaction force from the anchor plate 3a as shown by the black arrow in the figure, a tensile force is applied to the PC steel bar 2 as shown by the white arrow in the figure.

When applying a tensile force, it is desirable to use a reaction stand called a chair and connect a tensile force introduction rod to the male screw 32 with a coupler (both not shown), and apply a tensile force to the tensile force introduction rod so that an even reaction force acts on the anchor plate 3a.

When a predetermined tensile force is applied to the PC steel rod 2, the nut 33 is tightened to press the anchor plate 3a against the end 7a of the cylindrical reaction member 4a, fixing it to the cylindrical reaction member, and then the reaction stand, the tensile force introduction rod, and the coupler are removed.

In this way, the tensile force of the PC steel rod 2 is balanced with the compressive force acting as a reaction force generated in the cylindrical reaction members 4a, 4b and the reaction release mechanism 5, and thus a tensile force is introduced into the PC steel rod 2.

On the other hand, when prestressing concrete, the above-mentioned prestress introduction unit 1 with tension introduced into the PC steel bar 2 is placed in the concrete pouring area, and then, as shown in FIG. 8, concrete 51 is poured into the concrete pouring area while being careful not to fill the area around the reaction force release mechanism 5 with concrete, and the concrete is allowed to develop strength. After that, the nuts 15 are loosened to widen the connection distance between the clamping members 12, 13, and the wedge-shaped members 11a, 11b are moved relative to each other so that the overall dimension of the wedge-shaped members along the material axis 10 is shortened.

By doing this, the overall dimensions of the wedge-shaped members 11a, 11b are shortened, and the opposing ends of the cylindrical reaction members 4a, 4b, the bases 8a, 8b, come closer together, and the compressive force generated in each cylindrical reaction member disappears. As a result of the disappearance of the compressive force as a reaction force, the tensile force introduced into the PC steel bar 2 is transmitted as a compressive force through the anchor plates 3a, 3b to the surrounding concrete, as shown in the figure, and the concrete functions as prestressed concrete.

Next, we will explain the method of connecting precast concrete members to each other using the prestress introduction unit 1 when applied to bridge deck replacement.

Figure 9 shows a plan view of the deck 101 of the bridge in question and a view seen from the direction of the arrow C-C.

As shown in the figure, the deck 101 is constructed by arranging rectangular precast concrete members 103a', 103b' side by side in a direction perpendicular to the bridge axis, across the main girder 102 of the bridge, and laying these in a row along the bridge axis.

As already explained, to replace the precast concrete members 103a' and 103b', first, tension is introduced into the PC steel rods 2 that constitute the prestress introduction unit 1 at a factory or the like.

Next, the new precast concrete member 103a to be replaced is fabricated so that the anchor plate 3a of the prestress introduction unit 1, in which tensile force is introduced to the PC steel rod 2, is embedded in the precast concrete member and the anchor plate 3b protrudes.

Meanwhile, the new precast concrete member 103b to be replaced is manufactured in a separate process from the introduction of tensile force into the prestress introduction unit 1 so that a notch, as described below, is formed.

Next, the precast concrete member 103a with the prestress introduction unit 1 pre-attached and the precast concrete member 103b with the notch formed therein are transported to the construction site, which is the bridge deck replacement site.

When replacing a bridge deck, for example in the case of a bridge with two lanes on each side, a full road closure and traffic congestion can be avoided by closing only one lane and allowing the other lane to pass. Taking this as an example, first, as shown in Figure 10(a), of the existing precast concrete members 103a', 103b' to be replaced, only precast concrete member 103b' is removed, and then, as shown in Figure 10(b), precast concrete member 103b with a notch 114 formed therein is installed in the removed location.

Next, the existing precast concrete member 103a' is removed as shown in FIG. 1(c), and then a precast concrete member 103a with a prestress introduction unit 1 pre-attached is installed in the removed location as shown in FIG. 1(d).

When installing the precast concrete members 103a and 103b, the precast concrete members 103a and 103b are placed side by side so that the anchor plate 3b is positioned within the notch 114 of the precast concrete member 103b, as shown in FIG. 11(a).

Next, as shown in FIG. 1(b), concrete is poured into the notch 114 and into the space extending between the opposing surfaces 115a, 115b of the precast concrete members 103a, 103b, excluding the working area 131 for operating the reaction force release mechanism 5.

In this way, a tensile force transmission section 113 is provided in the cutout 114 so as to be continuously and integrally formed with the precast concrete member 103b, and an anchor plate 3b is embedded in the tensile force transmission section.

In addition, a joint 116 is provided in the space extending between the opposing surfaces 115a, 115b of the precast concrete members 103a, 103b, so as to be continuously and integrally formed with the precast concrete members 103a, 103b.

It is preferable to enhance the continuous integration between the precast concrete member 103b and the tensile force transmission section 113 by appropriately protruding the reinforcing bars (not shown) arranged in the precast concrete member 103b from the precast concrete member into the cutout 114, and to enhance the continuous integration between the precast concrete members 103a, 103b and the joint section 116 by appropriately protruding the reinforcing bars (not shown) arranged in the precast concrete members 103a, 103b from the respective precast concrete members into the space extending to the opposing surfaces 115a, 115b.

Next, after the concrete strength of the tensile force transmission section 113 and the joint section 116 is realized, as already explained, the compressive force of the cylindrical reaction members 4a and 4b that constitute the prestress introduction unit 1 is released.

In this way, as the compressive force acting on the cylindrical reaction members 4a, 4b is released, the tensile force of the PC steel rod 2, which had been acting as a reaction force, is balanced with the compressive force in the surrounding concrete through the support pressure of the anchoring plates 3b, 3a, as shown in Figure 12, and the compressive force of the concrete is balanced by the compressive reaction forces received from the opposing surfaces 115a, 115b of the precast concrete members 103a, 103b, respectively. Thus, the two precast concrete members 103a, 103b are pulled together and connected by the tensile force of the PC steel rod 2, which acts as a reaction force against the compressive force acting on the opposing surfaces 115a, 115b of the precast concrete members 103a, 103b via the joint 116.

After releasing the tensile force, the boxed-out work area 131 can be filled with concrete or mortar as appropriate.

As described above, according to the prestress introduction unit 1 of this embodiment, the wedge-shaped members 11a, 11b are moved relative to each other so that the overall dimensions of the wedge-shaped members 11a, 11b are shortened while embedded in concrete, thereby bringing the bases 8a, 8b of the cylindrical reaction members 4a, 4b closer together. This makes it possible to introduce prestress into the concrete while avoiding a situation in which the operation of generating or releasing compressive force becomes difficult due to excessive friction at the contact surfaces of the machine parts, and in particular makes it possible to efficiently introduce prestress using the pretensioning method at construction sites such as bridge construction sites.

In other words, conventionally, compressive forces were generated or released on the contact surfaces of machine parts such as nuts, which acted on each other, and this compressive force could cause excessive friction on the contact surfaces of the machine parts, making each operation difficult.

In contrast, when the wedge-shaped members 11a and 11b are moved relative to each other so that the overall dimensions of the wedge-shaped members 11a and 11b are shortened in order to release the compressive force generated in the cylindrical reaction members 4a and 4b in the prestress introduction unit 1 according to this embodiment, as shown in FIG. 13, the component force P1 perpendicular to the protruding side inclined surface 212a and the non-protruding side inclined surface 215a of the wedge-shaped member 11a and the protruding side inclined surface 212b and the non-protruding side inclined surface 215b of the wedge-shaped member 11b is supported by the normal load N acting from the wedge-shaped member 11b to the protruding side inclined surface 212a and the non-protruding side inclined surface 215a of the wedge-shaped member 11a. Considering this, the relative movement adjustment means only needs to support the component force P2 parallel to the protruding side inclined surfaces 212a and 212b and the non-protruding side inclined surfaces 215a and 215b (hereinafter simply referred to as inclined surfaces).

Specifically, the reaction force R to be borne by the relative movement amount adjustment means is expressed as follows:
R = P sin θ - μN (1)
θ: inclination of the inclined surface with respect to the plane perpendicular to the material axis 10 of the PC steel bar 2 μ: friction coefficient at the interface of the inclined surface Since the component force _R1 is
R ₁ = (P·sinθ-μN ) cosθ (2)
It becomes.

Here, if the friction coefficient μ can be substantially ignored,
_R1 = P sin θ cos θ (2')
Therefore, when tan θ=3/10,
_R1 = 0.275P (3)
It can be seen that the load _R1 to be borne by the two sets of bolts 14 and nuts 15 via the clamping member 13 is sufficient at 27.5% of the compressive force P from the cylindrical reaction member 4a.

In this way, the prestress introduction unit 1 makes it possible to release the compressive force acting on the cylindrical reaction members 4a and 4b under a load that is significantly smaller than conventional methods, making it possible to efficiently and reliably release the force (introduce prestress into the concrete) at the construction site.

In addition, according to the prestress introduction unit 1 of this embodiment, the protruding portion 211a is engaged with the inner circumferential surface 221b of the protruding portion 211b via the step 213a, and the protruding portion 211b is engaged with the inner circumferential surface 221a of the protruding portion 211a via the step 213b, so that the protruding portions 211a and 211b each function as the convex portion of the present invention, thus restricting the relative rotation of the wedge-shaped members 11a and 11b around the material axis 10, and making it possible to perform the above-mentioned release operation more reliably.

In this embodiment, the reaction force release mechanism 5 is provided with intermediate pedestals 16a, 16b, but if there are no problems when the compressive force is transmitted from the cylindrical reaction members 4a, 4b to the wedge-shaped members 11a, 11b, or when the wedge-shaped members 11a, 11b move relative to each other, the intermediate pedestals 16a, 16b may be omitted.

In addition, in this embodiment, the through openings 17a, 17b and the base side through openings 25a, 25b are cut out, but as long as there is no problem with the relative movement of the wedge-shaped members 11a, 11b, they may be elongated holes.

In addition, in this embodiment, when introducing a tensile force into the PC steel rod 2, as explained in FIG. 7, a reaction force is taken from the anchor plate 3a while a tensile force is applied to the PC steel rod 2, and then the nut 33 is tightened to press the anchor plate 3a against the end 7a of the cylindrical reaction member 4a, thereby fixing it to the cylindrical reaction member. However, instead of this, a reaction force release mechanism 5 may be used to introduce a tensile force into the PC steel rod 2.

That is, using the bolts 14 and nuts 15 and clamping members 12, 13 that constitute the reaction force release mechanism 5, the wedge-shaped members 11a, 11b are moved relatively against the compressive force transmitted from the tubular reaction members 4a, 4b so that the overall dimension of the wedge-shaped members 11a, 11b along the material axis 10 of the PC steel rod 2 is lengthened from _Lw ' to _Lw .

By doing this, the overall dimensions of the wedge-shaped members 11a, 11b are lengthened, and the opposing ends of the cylindrical reaction members 4a, 4b, the bases 8a, 8b, are pushed apart, generating a compressive force, which in turn introduces a tensile force into the PC steel rod 2.

In addition, in this embodiment, the protruding side inclined surface 212a of the protruding portion 211a provided at the stepped end 201a of the wedge-shaped member 11a and the non-protruding side inclined surface 215b of the non-protruding portion 214b provided at the stepped end 201b of the wedge-shaped member 11b are moved relative to each other in a manner such that one of them slides over the other, and the protruding side inclined surface 212b of the protruding portion 211b provided at the stepped end 201b of the wedge-shaped member 11b and the non-protruding side inclined surface 215a of the non-protruding portion 214a provided at the stepped end 201a of the wedge-shaped member 11a are moved relative to each other in a manner such that one of them slides over the other. The exit inclined surface 215b functions as the inclined surface of the present invention, and the protruding portion 211a is engaged with the inner peripheral surface 221b of the protruding portion 211b via the step 213a, and the protruding portion 211b is engaged with the inner peripheral surface 221a of the protruding portion 211a via the step 213b, so that the protruding portion 211a and the protruding portion 211b function as the convex portion of the present invention. However, the present invention is not limited to the above embodiment, as long as a convex portion is formed on one of the pair of wedge-shaped members and a concave portion or convex portion that engages with the convex portion is formed on the other so that the relative rotation of the wedge-shaped members 11a, 11b around the material axis 10 is restricted.

For example, as shown in FIG. 14, the wedge-shaped member of the present invention can be configured with a wedge-shaped member 311a having protruding portions 411a, 411a that are convex portions, and a wedge-shaped member 311b having non-protruding portions 411b, 411b that are recessed portions in which the protruding portions are engaged.

In addition, in this configuration, the protruding portion of the wedge-shaped member 311b sandwiched between the non-protruding portions 411b, 411b can be considered as the convex portion of the present invention, and the non-protruding portion of the wedge-shaped member 311a sandwiched between the protruding portions 411a, 411a can be considered as the concave portion of the present invention, and the protruding portions 411a, 411a of the wedge-shaped member 311a and the protruding portion of the wedge-shaped member 311b sandwiched between the non-protruding portions 411b, 411b can each be considered as the convex portion of the present invention.

Also, as shown in FIG. 15, the wedge-shaped member of the present invention may be constituted by a wedge-shaped member 511a having grooves 611a, 611a formed as recesses, and a wedge-shaped member 511b having ridges 611b, 611b formed as protrusions that fit into and engage with the grooves.

[Second embodiment]
Next, a second embodiment will be described, in which the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted.

The prestress introduction unit according to this embodiment, like the first embodiment, comprises a PC steel bar 2, a pair of anchoring plates 3a, 3b attached near each end of the PC steel bar, a pair of cylindrical reaction members 4a, 4b, and a reaction release mechanism. However, as shown in FIG. 16, the reaction release mechanism according to this embodiment is composed of a pair of wedge-shaped members 711a, 711b, a pair of clamping members 712, 713 that clamp the wedge-shaped members from the sides of the material axis 10 of the PC steel bar 2, two sets of bolts 14 and nuts 15 as a connecting mechanism that connects the clamping members to each other, and intermediate pedestals 16a, 16b (not shown in FIG. 16).

The wedge-shaped members 711a, 711b have a shape similar to each cut piece obtained by cutting a rectangular parallelepiped diagonally, and each has a through opening 717a, 717b for passing the PC steel rod 2 through. In addition, each has an inclined surface 718a, 718b that is inclined with respect to a plane perpendicular to the material axis 10 of the PC steel rod 2, and the inclined surfaces are arranged so that they abut against each other.

The wedge-shaped members 711a, 711b have pressure-bearing surfaces 719a, 719b located opposite the inclined surfaces 718a, 718b, to which compressive forces are transmitted from the pedestals 8a, 8b via the intermediate pedestals 16a, 16b, respectively, and the through-openings 717a, 717b are cut out to prevent the relative movement of the inclined surfaces 718a, 718b from being restricted when one of them slides over the other.

It is advisable to take measures such as applying a lubricant with excellent load resistance or coating the inclined surfaces 718a, 718b of the wedge-shaped members 711a, 711b with PTFE (polytetrafluoroethylene) to minimize friction.

The clamping members 712 and 713 are rectangular parallelepipeds, and their opposing inner surfaces are formed with fitting grooves 720 and 722, which serve as fitting recesses with a rectangular cross section. The peripheral surfaces 724b and 724a of the wedge-shaped members 711b and 711a abut against the fitting grooves, respectively, so that a portion of each wedge-shaped member is fitted into each of the fitting grooves. The clamping member 712 has bolt holes 21 and 21 at positions that sandwich the fitting groove 720, and the clamping member 713 has bolt holes 23 and 23 at positions that sandwich the fitting groove 722. Bolts 14 are inserted into the two sets of bolt holes 21 and 23, respectively, and nuts 15 are screwed onto the ends of the bolts.

In addition, the clamping member 712 has a countersink 26 on the surface opposite the fitting groove 720, into which the head of the bolt 14 is fitted.

The fitting grooves 720, 722 of the clamping members 712, 713 and the peripheral surfaces 724b, 724a of the wedge-shaped members 711b, 711a are preferably coated with a lubricant with excellent load resistance or coated with PTFE to reduce friction, as are the inclined surfaces 718a, 718b of the wedge-shaped members 711a, 711b and both sides of the intermediate pedestals 16a, 16b.

As can be clearly seen in Figure 17, the connecting mechanism consisting of the bolt 14, nut 15 and clamping members 712, 713 is designed to relatively move the wedge-shaped members 711a, 711b along the material axis 10 from a state in which the overall dimension of the members is _Lw (the state in Figures 17(a) and (b)) to a state in which the overall dimension is shortened to a state of _Lw ' (the state in Figures 17(c) and (d)) by turning each nut 15 in the loosening direction, and the bolt 14, nut 15 and clamping members 712, 713 function as a relative movement adjustment means for adjusting the relative movement amount of the wedge-shaped members 711a, 711b along the perpendicular direction to the material axis 10 of the PC steel bar 2.

In addition, the wedge-shaped members 711a, 711b and the clamping members 712, 713 are restricted from rotating about the material axis 10 of the wedge-shaped members 711a, 711b relative to the clamping members 712, 713 by fitting a portion of the wedge-shaped members 711b, 711a into the fitting grooves 720, 722 formed in the clamping members 712, 713, respectively.

The procedure for introducing tensile force into the PC steel bar 2 in the prestress introduction unit of this embodiment, the procedure for introducing prestress into the concrete, and the method for connecting precast concrete members to each other using the prestress introduction unit are the same as those in the first embodiment, so their explanation will be omitted here.

As described above, according to the prestress introduction unit of this embodiment, as in the first embodiment, the wedge-shaped members 711a, 711b are moved relative to each other so that the overall dimensions of the wedge-shaped members 711a, 711b are shortened while embedded in concrete, thereby bringing the bases 8a, 8b of the cylindrical reaction members 4a, 4b closer together. This makes it possible to introduce prestress into the concrete while avoiding a situation in which the operation of generating or releasing a compressive force becomes difficult due to excessive friction at the contact surfaces of the machine parts, and in particular makes it possible to efficiently introduce prestress using the pretensioning method at construction sites such as bridge construction sites.

In addition, with the prestress introduction unit according to this embodiment, portions of the wedge-shaped members 711b, 711a are fitted into the fitting grooves 720, 722 formed in the clamping members 712, 713, respectively, thereby restricting the rotation of the wedge-shaped members 711a, 711b about the material axis 10 relative to the clamping members 712, 713, respectively, and as a result, the relative rotation of the wedge-shaped members 711a, 711b about the material axis 10 is restricted, so that the release operation described above can be performed more reliably.

In this embodiment, fitting grooves 720, 722 are formed in the clamping members 712, 713, and a portion of the wedge-shaped members 711b, 711a is fitted into each fitting groove, thereby preventing rotation of the wedge-shaped members 711a, 711b relative to the clamping members 712, 713 around the material axis 10. However, in the present invention, it is sufficient to make the cross sections of the pair of wedge-shaped members noncircular and form fitting recesses facing each other in the pair of clamping members so as to abut against their peripheral surfaces, thereby restricting the rotation of each wedge-shaped member relative to the pair of clamping members around the material axis.

Therefore, the pair of wedge-shaped members and pair of clamping members according to the present invention can be constructed, for example, using wedge-shaped members 811a, 811b and clamping members 812, 813 shown in FIG. 18.

Here, the wedge-shaped members 811a, 811b have an elliptical cross section perpendicular to the material axis 10, and are provided with notched through openings 817a, 817b for passing the PC steel bar 2 through. They are also provided with inclined surfaces 818a, 818b that are inclined relative to the plane perpendicular to the material axis 10 of the PC steel bar 2, and are arranged so that the inclined surfaces come into contact with each other. The clamping members 812, 813 each have fitting grooves 820, 822 formed on their opposing inner surfaces as fitting recesses with curved cross sections, and the peripheral surfaces 824b, 824a of the wedge-shaped members 811b, 811a come into contact with the fitting grooves, respectively, so that a portion of each wedge-shaped member is fitted into each of the fitting grooves.

This modified example also exhibits the above-mentioned relative rotation prevention effect, but except for the fact that the cross section of the wedge-shaped member is elliptical and the fitting recess of the clamping member has a corresponding shape, the configuration is almost the same as the above-mentioned embodiment, so detailed explanations of other configurations and effects will be omitted here.

Although not specifically mentioned in this embodiment or its modified examples, it is possible to form a convex portion on one side of the wedge-shaped members 711b, 711a or the wedge-shaped members 811b, 811a, and a concave portion or a convex portion that engages with the convex portion on the other side, and the convex portion or the concave portion can be configured in the same way as described in the first embodiment.

This configuration makes it possible to more reliably prevent the wedge-shaped members 711a, 711b and the wedge-shaped members 811b, 811a from rotating around the material axis 10.

1 Prestress introduction unit 2 PC steel bar (PC steel material)
3a, 3b Fixing plate (fixing member)
4a, 4b Cylindrical reaction member 5 Reaction release mechanism 8a, 8b Base (opposite end)
11a, 11b: a pair of wedge-shaped members; 12, 13: a pair of clamping members (relative movement amount adjustment means)
14 Bolt (connection mechanism, relative movement adjustment means)
15 Nut (connecting mechanism, relative movement adjustment means)
16a, 16b Intermediate base 18a, 18b Inclined surface 19a, 19b Pressure-bearing surface 17a, 17b Through opening 25a, 25b Base-side through opening 201a, 201b Step-shaped end 211a, 211b Protruding portion (convex portion)
212a, 215a: protruding side inclined surface, non-protruding side inclined surface (inclined surface)
212b, 215b: protruding side inclined surface, non-protruding side inclined surface (inclined surface)
311a, 311b Wedge-shaped members 411a, 411a Protruding portion (convex portion)
411b, 411b Non-protruding portion (recess)
511a, 511b Wedge-shaped members 611a, 611a Groove (recess)
611b, 611b protrusions (convex portions)
711a, 711b Wedge-shaped members 811a, 811b Wedge-shaped members

In addition, as described in claim 5 , the prestress introduction unit of the present invention comprises intermediate bases, each having a base-side through opening for passing the PC steel material, disposed between each of the opposing ends and the pair of wedge-shaped members, and each of the base-side through openings is formed in a notch or long hole shape so that the relative movement of the pair of wedge-shaped members is not restricted.
Furthermore, as described in claim 6 , the prestress introduction unit of the present invention comprises intermediate bases each having a base-side through opening for passing the PC steel material therethrough, which are disposed between each of the opposing ends and the pair of wedge-shaped members, and each of the base-side through openings is formed in a notch or long hole shape so that the relative movement of the pair of wedge-shaped members is not restricted.

Claims (5)

the PC steel member; a pair of anchoring members attached near each end of the PC steel member; a pair of tubular reaction members arranged coaxially with the PC steel member and through which the PC steel member is inserted so that a reaction force for introducing a tensile force into the PC steel member is transmitted to each of the anchoring members or the vicinity of each end of the PC steel member; and a reaction force release mechanism capable of releasing the reaction force generated in the pair of tubular reaction members by bringing the opposing ends of the reaction force members closer together, the reaction force release mechanism being composed of a pair of wedge-shaped members each having a through opening for passing the PC steel member through and each having an inclined surface inclined with respect to a plane perpendicular to the material axis of the PC steel member, the inclined surfaces being arranged so as to abut against each other, and a relative movement amount adjustment means for freely adjusting the relative movement amount of the pair of wedge-shaped members along the direction perpendicular to the material axis,
A prestress introduction unit characterized in that the pair of wedge-shaped members have pressure-loading surfaces on the opposite sides of each of the inclined surfaces, through which compressive forces are transmitted from each of the opposing ends, and each of the through openings is formed in a notch or long hole shape so that the relative movement of each of the inclined surfaces is not restricted when one of the inclined surfaces moves relative to the other by sliding against the other, and a convex portion is formed on one of the pair of wedge-shaped members and a concave portion or convex portion that engages with the convex portion is formed on the other so that relative rotation around the material axis is restricted. A prestress introduction unit according to claim 1, in which a stepped end portion is provided on each of the opposing sides of the pair of wedge-shaped members, and each of the inclined surfaces is constituted by a protruding side inclined surface formed on the end face of the protruding portion and a non-protruding side inclined surface formed on the end face of the non-protruding portion, and each of the protruding portions is the convex portion. A prestress introduction unit according to claim 1 or claim 2, in which the relative movement adjustment means is composed of a pair of clamping members that clamp the pair of wedge-shaped members from the sides of the material shaft, and a connecting mechanism that connects the pair of clamping members to each other. the PC steel member; a pair of anchoring members attached near each end of the PC steel member; a pair of tubular reaction members arranged coaxially with the PC steel member and through which the PC steel member is inserted so that a reaction force for introducing a tensile force into the PC steel member is transmitted to each of the anchoring members or the vicinity of each end of the PC steel member; and a reaction force release mechanism capable of releasing the reaction force generated in the pair of tubular reaction members by bringing the opposing ends of the reaction force members closer together, the reaction force release mechanism being composed of a pair of wedge-shaped members each having a through opening for passing the PC steel member through and each having an inclined surface inclined with respect to a plane perpendicular to the material axis of the PC steel member, the inclined surfaces being arranged so as to abut against each other, and a relative movement amount adjustment means for freely adjusting the relative movement amount of the pair of wedge-shaped members along the direction perpendicular to the material axis,
The pair of wedge-shaped members have pressure-loading surfaces on the opposite sides of the inclined surfaces, through which compressive forces are transmitted from the opposing ends, and the through openings are formed in a notch or slot shape so that the relative movement of the inclined surfaces is not restricted when one of the inclined surfaces slides over the other.
the relative movement adjustment means is composed of a pair of clamping members that clamp the pair of wedge-shaped members from the sides of the material shaft, and a connecting mechanism that connects the pair of clamping members to each other,
A prestress introduction unit characterized in that the pair of wedge-shaped members and the pair of clamping members have non-circular cross sections and opposing mating recesses are formed in the pair of clamping members so as to abut against their peripheral surfaces, thereby restricting rotation of each wedge-shaped member about its material axis relative to the pair of clamping members. A prestress introduction unit according to any one of claims 1 to 4, in which intermediate pedestals each having a pedestal-side through opening for passing the PC steel material therethrough are disposed between each of the opposing ends and the pair of wedge-shaped members, and each of the pedestal-side through openings is formed in a notch or long hole shape so that the relative movement of the pair of wedge-shaped members is not restricted.

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