JP6251833B1 - Intermediate fixing method for PC steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate fixing method capable of easily forming (fixing) an intermediate fixing member for applying prestress to a concrete frame to a PC steel material. [MEANS FOR SOLVING PROBLEMS] The present invention is an intermediate fixing method in which a PC steel material is intermediately fixed at a remaining portion excluding a dismantling portion in an existing PC structure. First, a mold is attached to the PC steel material exposed by removing a part of the concrete casing of the PC structure. Then, by filling the melted metal in the mold, an intermediate fixing member for prestressing the remaining portion is formed integrally with the PC steel material. [Selection] Figure 2

Description

  The present invention relates to an intermediate fixing method for PC steel in an existing PC structure.

  In a PC (prestressed concrete) structure, prestressed (compressive force) is applied to the concrete frame by embedding PC steel in a tensioned state inside the concrete frame and fixing both ends to the concrete frame with a fixing device. Yes.

  When it is desired to partially disassemble such an existing PC structure, an intermediate fixing method is used because prestress must remain in the PC steel material in the remaining portion. As an intermediate fixing method, for example, there is a method described in Patent Document 1. In Patent Document 1, the PC steel material is suspended before cutting at the intermediate portion of the PC structure, and the exposed PC steel material is fixed to the remaining portion by the intermediate fixing device. As the intermediate fixing device, a mechanical fixing structure such as a wedge or an adhesion type fixing structure using an expanding material is used.

Japanese Patent No. 4712612

  In the intermediate fixing method disclosed in Patent Document 1, since the PC steel material is held with a uniform wedge, it is necessary to uniformly pack the PC steel wires. Hereinafter, the intermediate fixing method of Patent Document 1 will be described using FIG. 7 while paying attention to the dense state of the PC steel wires. FIG. 7 is a cross-sectional view showing a cut surface of a sheath in which a plurality of PC steel wires are accommodated. In FIG. 7, a plurality of PC steel wires 210 are accommodated inside the sheath 220, and the grout is filled around the PC steel wires 210.

  A cut surface A shown in FIG. 7A shows a state in which a plurality of PC steel wires 210 are uniformly dense with reference to the central portion of the sheath 220. That is, in the cut surface A, a plurality of PC steel wires 210 are densely packed in a circular region. For example, in the vicinity of the fixing device, the PC steel wires 210 are easily arranged in a central portion of the sheath 220, so that the plurality of PC steel wires 210 are in a uniformly dense state like the cut surface A.

  A cut surface B shown in FIG. 7B shows a state in which a plurality of PC steel wires 210 are non-uniformly concentrated inside the sheath 220. That is, on the cut surface B, a plurality of PC steel wires 210 are arranged in a biased manner inside the sheath 220 and are densely packed in the non-circular region. For example, at a position away from the fixing device, the PC steel wires 210 are unevenly packed like the cut surface B because they are likely to be biased inside the sheath 220.

  The intermediate fixing is performed at an intermediate portion serving as a boundary between the remaining portion and the dismantling portion, that is, a position away from the fixing device, before partially disassembling the existing PC structure. For this reason, the dense state of the PC steel wire in the intermediate part is often non-uniform like the cut surface B shown in FIG. 7B, and the dense state is accurate unless it is lifted from the concrete frame. Difficult to grasp. Therefore, when using an intermediate fixing device that grips the PC steel wire by a mechanical method such as a wedge, in addition to the variation in the gap between the PC steel wires, the gap between the intermediate fixing device and the PC steel wire Since variations occur, it is difficult to grip the PC steel wire using a uniform shaped wedge.

  In order to solve the above problems, Patent Document 1 describes an intermediate fixing method using a wedge. In the intermediate fixing method disclosed in Patent Document 1, a plurality of PC steel wires are assembled by a collecting machine, and a wedge is mounted so as to cover the aggregate of PC steel wires. A steel insert is bonded to the wedge in contact with the PC steel wire. When a clamping force is applied to the wedge in the fixing operation, the steel insert is crushed. This crushed piece fills the gap between the PC steel wires and the gap between the PC steel wire and the wedge, so that the frictional force increases and the wedge grips the PC steel wire. Patent Document 1 also discloses a method of arranging a dummy material so as to fill a gap in the PC steel wire before the wedge is attached, and adjusting the dense state of the PC steel wire.

  However, the intermediate fixing method disclosed in Patent Document 1 forcibly gathers PC steel wires with prestress introduced by applying external force using a collecting machine, so that the PC steel wires receive external force from the collecting machine and break. there's a possibility that.

  Furthermore, in the method of arranging the dummy material on the PC steel material, the position and the number of the dummy material to be arranged vary depending on the dense state of the PC steel wire, and the work becomes complicated. Even if the dense state of the PC steel wire is evenly arranged, the diameter of the PC steel material may change from the original diameter due to the arrangement of the dummy material. In this case, it becomes difficult to grip the PC steel wire using a uniform wedge.

  Accordingly, an object of the present invention is to provide an intermediate fixing method capable of easily forming (fixing) an intermediate fixing member for applying prestress to a concrete frame to a PC steel material.

  The first invention of the present application is an intermediate fixing method in which a PC steel material is intermediately fixed at a remaining portion excluding a dismantling portion in an existing PC structure, and is exposed by removing a part of a concrete casing of the PC structure. A mold is attached to the PC steel. Then, by filling the melted metal in the mold, an intermediate fixing member for prestressing the remaining portion is formed integrally with the PC steel material.

  The metal described above can be a metal having a melting point of 300 ° C to 400 ° C.

As the intermediate fixing member, a wedge-shaped male member fitted to the female member can be used. In this case, the male member is fitted to the female member by moving the female member in the direction from the remaining portion toward the dismantling portion using a jack. And the fitting state of a female member and a male member is maintained using the spacer apparatus arrange | positioned between the removal part of a concrete frame, and a female member.

Moreover, the tension | tensile_strength of PC steel materials is increased by moving a female member and a male member in the direction which goes to a dismantling part using a jack in the state which the female member and the male member fitted. Before refilling the removal part of a concrete frame with concrete, the circumference | surroundings of the part which protrudes from a female member can be covered with a cap.

On the other hand, by using the jack, by Before moving the intermediate fixing member in a direction towards the dismantling unit from leaving portions, increasing the tension of the PC steel. The intermediate fixing member is held at a position where the tension of the PC steel material is increased by using a spacer device arranged between the removal portion of the concrete frame and the intermediate fixing member.

  According to the intermediate fixing method of the present invention, an intermediate fixing device can be attached to a PC steel simply by installing a mold for a PC steel arranged with an existing PC structure and filling the mold with a molten metal. Can be formed integrally.

It is sectional drawing which shows the inside of PC structure. It is a figure which shows an example of the process of the intermediate fixing method of this embodiment. It is a top view showing a jack and an intermediate fixing device in the present embodiment. It is a figure which shows another example of the process of the intermediate fixing method of this embodiment. It is a top view in the modification of the intermediate fixing device mounted on the PC steel material of the present embodiment. It is sectional drawing which shows a formwork when pressure-molding a male member. It is AA sectional drawing of FIG. 6A. It is a side view which shows a formwork when pressure-molding a male member. It is an end view which shows a formwork when pressure-molding a male member. It is sectional drawing which shows the dense state of PC steel materials.

  The intermediate fixing method which is an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing the inside of a PC structure.

  The existing PC structure 100 is, for example, a T girder bridge or an I girder bridge. In FIG. 1, a T girder bridge is shown as an example.

  The PC steel material 1 is arranged in the width direction (left-right direction in FIG. 1) of the PC structure 100, and is embedded in the concrete casing 2 in a tensioned state. Both ends of the PC steel material 1 are fixed by fixing devices 1 </ b> A and 1 </ b> B at both ends in the width direction of the concrete frame 2. Known fixing devices are used as the fixing devices 1A and 1B. Thereby, the restoring force of the PC steel material 1, that is, prestress acts on the concrete casing 2, and the concrete casing 2 can obtain crack resistance. In FIG. 1, one PC steel material 1 is shown, but for example, a bundle of a plurality of PC steel materials 1 can be used.

  Moreover, in the PC structure 100 shown in FIG. 1, the PC steel material 1 is embed | buried in the concrete frame 2, bending the up-down direction. Since tension is acting on the PC steel 1, a force for displacing the PC steel 1 in a direction along a virtual straight line connecting the two fixing devices 1 </ b> A and 1 </ b> B is generated. At this time, as the curvature of the PC steel material 1 increases as in the region P of the PC steel material 1 (region surrounded by the dotted-line ellipse in FIG. 1), a plurality of pieces in the region P as in the cut surface B in FIG. The PC steel material tends to be densely packed in a state of being biased in one direction with respect to the center of the sheath.

  In the PC structure 100, when disassembling only the dismantling part R2 (region in the one-dot chain line frame), the PC steel material 1 needs to be cut. In order to disassemble only the dismantled portion R2 without adversely affecting the prestress applied to the concrete frame 2 by the PC steel material 1, before cutting the PC steel material 1, the remaining portion R1 (region in the dotted frame) It is necessary to perform intermediate fixing in a predetermined intermediate portion 10 (region within a solid line frame) including the boundary between and the dismantling portion R2. In the intermediate fixing, a part of the concrete housing 2 is hung at the intermediate portion 10, and the tension of the PC steel material 1 is transferred to the hung PC steel material 1 in place of the fixing device 1B on the dismantling portion R2 side. An intermediate fixing device is installed. The intermediate fixing device is fixed to the remaining portion R1 after the disassembling portion R2 is disassembled. Thereby, only the dismantling part R2 can be disassembled, leaving the prestress accompanying the tension | tensile_strength of the PC steel material 1 in the remaining part R1.

  In the intermediate fixing method of this embodiment, a male member and a female member that are fitted to each other are used as the intermediate fixing device. In particular, the male member is integrally formed with the outer surface of the PC steel material 1 by casting, and the female member has a space in which the male member is fitted while the PC steel material 1 is inserted. Then, intermediate fixing can be performed by cutting the PC steel material 1 at a position on the dismantling part R2 side with respect to the intermediate fixing device. Hereinafter, the intermediate fixing method of the present embodiment will be described in detail.

  2A to 2F show the steps of the intermediate fixing method of the present embodiment over time in the intermediate portion 10 of FIG. Inside the dotted line frame is a suspended portion from which the concrete frame 2 is suspended. In addition, in FIG. 2, about the male member 61 mentioned later, the outer surface is shown instead of a cross section. Hereinafter, each step will be described.

  In step A shown in FIG. 2 (A), first, a part of the PC steel material 1 is lifted by lifting a part of the concrete casing 2 of the PC structure 100. Here, in the PC structure 100, a sheath (not shown) is disposed around the PC steel material 1, and a grout is filled between the PC steel material 1 and the sheath, so that the PC steel material 1 is exposed. The sheath and grout are removed. Then, the formwork 70 is attached to the exposed portion of the PC steel material 1. The mold 70 includes a filling port 70a for filling the metal in a molten state, and a molding part 70b for molding the molten metal filled from the filling port 70a into a predetermined shape. A hole for penetrating the PC steel material 1 is formed in the molded part 70b. For example, the mold 70 is composed of two halved main body pieces, and the two main body pieces are mounted so as to sandwich the PC steel material 1.

  Step B shown in FIG. 2B is a step of forming the male member 61 by casting. By filling the melted metal into the forming portion 70b from the filling port 70a and solidifying the molten metal, the male member 61 having a shape (wedge shape) along the forming portion 70b is formed. Here, if the temperature of the metal in the shaping | molding part 70b becomes below the temperature which can maintain the shape of the male member 61, the formwork 70 will be removed. Thereby, the male member 61 is fixed to the outer surface of the PC steel material 1.

  Since the male member 61 is formed by casting, the shape of the male member 61 is determined by the molding portion 70b of the mold 70. In the present embodiment, the shape of the male member 61 is a wedge shape having a tapered surface inclined with respect to the axial direction of the PC steel material 1.

  As the raw material (metal) for forming the male member 61, a metal that can suppress the thermal influence (adverse effect) on the PC steel material 1 at the casting temperature is used. Specifically, low melting point alloys such as zinc alloy, zinc aluminum alloy, and white metal are used. The casting temperature of these low melting point alloys is 300 to 400 ° C. Here, as a thermal influence which PC steel materials 1 receive at the time of casting, the breaking elongation of PC steel materials 1 accompanying the heating at the time of casting is mentioned. The elongation at break of the PC steel material 1 depends on the length of the PC steel material 1 exposed at the suspended portion of the concrete housing 2 and the length of the region in the PC steel material 1 where the male member 61 is formed. Therefore, by appropriately determining these lengths, casting can be performed at a temperature at which the elongation of the PC steel material 1 due to heating during casting does not reach the breaking elongation of the PC steel material 1. Therefore, even if the molten low melting point alloy is brought into contact with the PC steel material 1, the thermal effect (adverse effect) exerted on the PC steel material 1 can be suppressed, and the male member 61 can be formed by a simple method only by filling the molded portion 70b with the molten metal. Can be molded.

  Process C shown in FIG. 2C is a process of installing the plate member 30, the spacer device 40, the jack 50, and the female member 62 after the process B. The female member 62 is fitted to the male member 61. Installed so that it can. The intermediate fixing device 60 is configured by the male member 61 and the female member 62. The plate member 30 is disposed along the surface of the suspended portion of the concrete housing 2, and the spacer device 40 and the jack 50 are disposed between the plate member 30 and the intermediate fixing device 60. The configuration of each member will be described later with reference to FIG.

  Step D shown in FIG. 2D is a step of fitting the male member 61 to the female member 62 after the step C. In step D, the jack 50 presses the female member 62 toward the male member 61 via the spacer device 40 in the longitudinal direction of the PC steel material 1, thereby fitting the male member 61 to the female member 62.

  Although the male member 61 may be merely fitted to the female member 62, the tension force of the PC steel material 1 can be increased by pressing the female member 62 with the jack 50 in a state where the male member 61 is fitted to the female member 62. Can be increased. That is, in the state in which the male member 61 is fitted to the female member 62, the male member 61 and the female member 62 move together, so that the PC steel material 1 to which the male member 61 is fixed can be tensioned. Further tension can be applied to the PC steel 1 between the fixing device 1A on the remaining portion R1 side and the intermediate fixing device 60.

  Here, the procedure of steps C and D will be described with reference to FIG. FIG. 3 is a top view showing the configuration of the spacer device 40, the jack 50, the intermediate fixing device 60, and the like in the processes C and D.

  The plate member 30 is a plate-like member that transmits prestress received from the intermediate fixing device 60 to the concrete frame 2 via the spacer device 40 after the PC steel material 1 is cut. The plate member 30 is installed so that it abuts along the end surface on the side of the remaining portion R <b> 2 among the suspended portions of the concrete housing 2 while inserting the PC steel material 1.

  The plate member 30 only needs to be arranged so as not to interfere with the PC steel material 1. For example, the plate member 30 may be composed of a pair of main body pieces having a recess, and by combining the pair of main body pieces, a hole through which the PC steel material 1 is inserted through the recess of the pair of main body pieces may be formed.

  The spacer device 40 includes a pair of plate members 41 and 42 arranged substantially in parallel, and a bolt 43 and a nut 44 for adjusting the distance between the pair of plate members 41 and 42. The pair of plate members 41, 42 are positions that do not interfere with the PC steel material 1, and are installed between the plate member 30 and the female member 62. At this time, the plate member 41 contacts the plate member 30, and the plate member 42 contacts the female member 62 of the intermediate fixing device 60.

  The plate member 41 is provided with bolts 43 that are substantially perpendicular to the plate members 41 and 42 and extend toward the plate member 42. The plate member 42 is provided with a hole portion through which the bolt 43 is inserted and the nut 44 is not allowed to pass therethrough.

  The bolt 43 is formed with a thread that engages with the nut 44. The nut 44 can move in the axial direction of the bolt 43 by rotating around the axis of the bolt 43. As will be described later, the nut 44 is moved between the plate member 41 and the plate member 42, and the nut 44 is brought into contact with the plate member 42 pressed by the jack 50, whereby the distance between the pair of plate members 41, 42 is increased. The jack 50 can be removed while maintaining.

  In addition, the plate members 41 and 42 should just be arrange | positioned so that it may not interfere with PC steel material 1. FIG. For example, the plate members 41 and 42 may be provided with a concave groove through which the PC steel material 1 is inserted. Further, the positions and number of holes (holes through which the bolts 43 are inserted), bolts 43 and nuts 44 provided in the plate part 42 are not limited to those shown in FIG. 3, and the pressing of the plate member 42 by the jack 50 is obstructed. It is sufficient that it does not interfere with the intermediate fixing device 60.

  The jack 50 is installed between the plate members 41 and 42 of the spacer device 40 and presses the female member 62 through the plate member 42. An example of the jack 50 is a hydraulic jack. The jack 50 presses the female member 62 together with the plate member 42 toward the male member 61 in the longitudinal direction of the PC steel material 1. Thereby, as above-mentioned, the male member 61 and the female member 62 can be fitted, and the tension | tensile_strength of PC steel material 1 can be made to increase.

  The female member 62 has a hole 62 a that is a space for fitting the male member 61 and the fastening member 62 b while allowing the PC steel material 1 to be inserted therethrough. The wall surface of the hole 62 a is a tapered surface along the tapered surface of the male member 61. The female member 62 is composed of a pair of main body pieces having a concave portion which is a part of the hole portion 62a. By fixing the pair of main body pieces with the fastening member 62b, the hole portion 62a is formed by the concave portion of the pair of main body pieces. Is formed.

  The procedure of steps C and D will be described. The procedure (1) shown in FIG. 3 (1) corresponds to the process C. At this time, the jack 50 is installed between the pair of plate members 41 and 42 so that the plate member 42 can be pressed.

  In the procedure (2) shown in FIG. 3 (2), the jack 50 presses the plate member 42 so as to increase the distance between the plate member 41 and the plate member 42, whereby the female member 62 is interposed via the plate member 42. Is pressed toward the male member 61. Thereby, the male member 61 can be fitted into the hole 62 a of the female member 62. At this time, the plate member 42 is separated from the nut 44 by the movement of the plate member 42.

  In step (2), after the male member 61 is fitted to the female member 62, the plate member 42 is further pressed to move the intermediate fixing device 60 as described above, thereby increasing the tension of the PC steel material 1. Can be increased.

  In the procedure (3) shown in FIG. 3 (3), the nut 44 meshing with the bolt 43 is moved between the plate member 41 and the plate member 42 so as to contact the plate member 42. Thereby, when the jack 50 is removed, the plate member 42 can be prevented from moving. That is, the distance between the plate member 41 and the plate member 42 can be kept constant by using the bolt 43 and the nut 44, and the state in which the male member 61 is fitted to the female member 62 can be maintained.

  In step (4) shown in FIG. 3 (4), the pressing of the plate member 42 by the jack 50 is released, and the jack 50 is removed. Here, when fitting the male member 61 to the female member 62, the spacer device 40 can be omitted and only the jack 50 can be used. However, in this case, in order to keep the male member 61 fitted to the female member 62, the jack 50 must be left in place. As described above, by using the spacer device 40, after the jack 50 is used, the jack 50 can be removed, and the jack 50 can be prevented from being disposed.

  A description will be given with reference to FIG. 2 again. Step E shown in FIG. 2E is a step of attaching the cap 80 to the intermediate fixing device 60. The cap 80 covers the portion of the male member 61 protruding from the female member 62 (referred to as a protruding portion) while allowing the female member 62 to pass through the PC steel material 1 on the side opposite to the plate member 42 side. Installed. By mounting the cap 80, a space is formed around the protruding portion of the male member 61. For example, in order to insert the PC steel material 1, the cap 80 is constituted by a pair of main body pieces having a recess, and by combining the pair of main body pieces, the hole portion through which the PC steel material 1 is inserted through the recess of the pair of main body pieces. Is formed.

  Step F shown in FIG. 2 (F) is a step of cutting the concrete housing 2 together with the PC steel material 1 on the side of the dismantling portion R2 with respect to the intermediate fixing device 60 after the suspended portion of the concrete housing 2 is backfilled with concrete. is there. In the dismantling work of the dismantling part R2, the PC steel material 1 is cut together with the concrete housing 2, and the intermediate fixing device 60 is used instead of the fixing device 1B (see FIG. 1) of the dismantling part R2, so Stress (force in the direction indicated by arrow D1) can be applied. Here, the PC steel material 1 is fixed to the concrete frame 2 of the remaining portion R1 by the fixing device 1A and the intermediate fixing device 60.

  Further, when the PC steel material 1 is cut at the dismantling part R <b> 2 side, the male member 61 may be displaced in the direction of entering the hole 62 a of the female member 62 due to the shrinkage of the PC steel material 1 in the remaining part R <b> 1. . As described above, the female member 62 is fitted to the male member 61 by using the jack 50, but the male member 61 may be displaced with respect to the female member 62 depending on the contraction rate of the PC steel material 1. is there.

  Here, as described above, by using the cap 80 to form a space around the protruding portion of the male member 61, the above-described displacement of the male member 61 can be allowed. If the cap 80 is not provided, when the suspended portion of the concrete housing 2 is backfilled with concrete, the concrete adheres to the protruding portion of the male member 61, and the displacement of the male member 61 described above is hindered. That is, since the outer surface of the male member 61 is configured by a tapered surface, the displacement of the male member 61 described above is hindered by the concrete filled between the protruding portion of the male member 61 and the female member 62. By providing the cap 80 as in the present embodiment, the male member 61 and the female member 62 can be firmly fitted by allowing the displacement of the male member 61, and the PC steel material 1 by the intermediate fixing device 60 can be fitted. Fixing can be stabilized.

  Through the above steps, the PC steel material 1 is fixed to the remaining portion R1, and the dismantling portion R2 can be dismantled.

  FIG. 4 shows a modification of the intermediate fixing method shown in FIG. Steps A to D ((A) to (D) in FIG. 4) are the same steps as those in FIG.

  Step G shown in FIG. 4 (G) is a step of cutting the PC steel material 1 at the suspended portion of the concrete housing 2. When the PC steel material 1 is cut at the cutting portion 90 on the dismantling part R2 side of the intermediate fixing device 60, the prestress acting in the direction D1 can be received by the intermediate fixing device 60, as in the process F. As a result, the PC steel material 1 is fixed to the concrete housing 2 of the remaining portion R1 by the fixing device 1A and the intermediate fixing device 60, and prestress associated with the tension of the PC steel material 1 can remain in the remaining portion R1. Further, the cutting of the PC steel material 1 may cause the male member 61 to be displaced with respect to the female member 62 as described above.

  In step H shown in FIG. 4 (H), the suspended portion of the concrete housing 2 is backfilled with concrete. When refilling the suspended portion, the PC steel material 1 has already been cut, so there is no need to consider the displacement of the male member 61 relative to the female member 62, and the female member 62 has a cap 80 as shown in FIG. There is no need to wear. Therefore, the work of attaching the cap 80 is eliminated, and the work of the intermediate fixing method can be simplified.

  Through the above steps, the PC steel material 1 is fixed to the remaining portion R1, and the dismantling portion R2 can be dismantled. In particular, in the intermediate fixing method shown in FIG. 4, the displacement of the male member 61 relative to the female member 62 can be allowed without using the cap 80 shown in FIG. 2, and the male member 61 and the female member 62 can be firmly fixed. .

  In step D, the pressing force of the female member 62 by the jack 50 can be determined as appropriate. For example, if the male member 61 is displaced with respect to the female member 62 after the PC steel material 1 is cut, the tension of the PC steel material 1 is reduced by the amount of displacement of the male member 61. Considering the decrease in the tension force, if the tension force of the PC steel material 1 is increased when the female member 62 is pressed by the jack 50, the tension force of the PC steel material 1 can be suppressed from decreasing. In addition, the tension force of the PC steel material 1 can be increased more than the tension force before the PC steel material 1 is cut. Moreover, you may perform the press of the female member 62 with the jack 50 in the process E of FIG. 2, and the process G of FIG.

  In the intermediate fixing device 60 of this embodiment, the wedge-shaped male member 61 and the female member 62 are used. However, the present invention can also be applied to an intermediate fixing method using an anchor as shown in FIG. it can. As shown in FIG. 5, an anchor 63 is fixed to the PC steel material 1, and the anchor 63 can be formed by the same forming method as the male member 61 described above. Specifically, the anchor for forming the anchor 63 is mounted on the PC steel material 1 exposed from the concrete housing 2, the molten metal is filled in the mold, and the anchor is integrated with the PC steel material 1. 63 is formed.

  Here, it is preferable to install a spacer device 40 between the suspended portion of the concrete housing 2 and the anchor 63. In particular, when the PC steel material 1 is cut before the suspended portion of the concrete frame 2 is backfilled with concrete, it is necessary to install the spacer device 40 in order to prevent the anchor 63 from moving due to the cutting of the PC steel material 1. is there. In order to prevent the anchor 63 from moving during the hardening of the concrete even when the PC steel material 1 is cut after the suspended portion of the concrete housing 2 is backfilled with concrete, the spacer device 40 is used. It is good to install.

  When the spacer device 40 is installed, the plate member 42 of the spacer device 40 is brought into contact with one end surface of the anchor 63. Here, the plate member 42 is fixed by a nut 44 so that the plate member 42 does not move in the longitudinal direction of the PC steel material 1. When the PC steel material 1 is cut, prestress acts on the concrete frame 2 from the anchor 63 via the spacer device 40. Although not shown in FIG. 5, if the jack 50 is disposed between the pair of plate members 41 and 42 and the anchor 63 is pressed by the jack 50, the tension of the PC steel material 1 can be increased.

  In the present embodiment, the jack 50 is disposed between the pair of plate members 41 and 42. Here, depending on the size of the jack 50, it may be difficult to arrange the jack 50 between the pair of plate members 41 and 42. In this case, by using the jack described in Japanese Patent No. 5779705, the plate member 42 can be pressed in the direction in which the distance between the pair of plate members 41 and 42 is increased.

  Moreover, in the casting molding in the process B of this embodiment, the male member 61 can be pressure-molded using the mold 70 before the shape of the male member 61 is completely solidified. By this pressure molding, the adhesion between the male member 61 and the PC steel material 1 can be increased as compared with the case where pressure molding is not performed.

  The formwork 70 used for the pressure molding of the male member 61 will be described with reference to FIGS. 6A to 6D. 6A to 6D will be described on the assumption that the male member 61 is formed by the molding portion 70b of the mold 70. FIG. FIG. 6A is a cross-sectional view showing the configuration of the mold 70.

  The mold 70 includes a first mold 71, a second mold 72, a bolt 73a for connecting the first mold 71 and the second mold 72, and a nut 73b. The first mold 71 is composed of a pair of main body pieces 71 a and 71 b divided in a direction (vertical direction) orthogonal to the axial direction of the PC steel material 1. The main body pieces 71a and 71b are connected by bolts 73a and nuts 73b with a second mold frame 72 sandwiched between them in a direction orthogonal to the axial direction of the PC steel material 1.

  The filling port 70a is formed in the main body piece 71a. The molding part 70 b is formed by the two main body pieces 71 a and 71 b of the first mold 71 and the second mold 72. Since the second mold frame 72 is sandwiched between the two main body pieces 71a and 71b without a gap, the second mold frame 72 has a molten metal between the main body pieces 71a and 71b during casting. Leakage from the gap can be prevented.

  With reference to FIG. 6B, the structure of the 2nd formwork 72 is demonstrated. 6B is a cross-sectional view taken along the line AA in FIG. 6A. The second mold 72 is composed of four main body pieces divided in the axial direction of the PC steel material 1 and the direction orthogonal to the axial direction of the PC steel material 1. Specifically, the second mold 72 is composed of four main body pieces 72a, 72b, 72c, 72d. The main body pieces 72a and 72c have a symmetrical shape with the axis of the PC steel material 1 as the axis of symmetry. Similarly, the main body pieces 72b and 72d have a symmetrical shape with the axis of the PC steel material 1 as the axis of symmetry.

  Concave portions are formed on the opposing surfaces of the pair of main body pieces 72a and 72b, and these concave portions form holes 72e through which the bolts 73a are inserted when the main body pieces 72a and 72b are combined. Moreover, the wall surface which comprises a part of shaping | molding part 70b is formed by combining a pair of main body pieces 72a and 72b.

  The second mold 72 is removed before pressure molding of the male member 61. Here, when removing the second formwork 72, the shape of the concave portions of the main body pieces 72a and 72b can be appropriately determined so that the concave portions of the main body pieces 72a and 72b do not interfere with the bolt 73a. The combination of the main body pieces 72c and 72d is the same as the combination of the main body pieces 72a and 72b as described above.

  FIG. 6C is a view when the mold 70 is viewed from the direction of the arrow B shown in FIGS. 6A and 6B. The main body piece 72a includes an end plate portion 72a1 extending in a direction orthogonal to the PC steel material 1, and a spacer portion 72a2 extending from the end plate portion 72a1 along the axial direction of the PC steel material 1. The end plate portion 72a1 constitutes a part of the forming portion 70b with a wall surface orthogonal to the PC steel material 1. Similarly, the main body piece 72b has an end plate portion 72b1 extending in a direction orthogonal to the PC steel material 1, and a spacer portion 72b2 extending from the end plate portion 72b1 along the axial direction of the PC steel material 1. The end plate portion 72b1 constitutes a part of the forming portion 70b with a wall surface orthogonal to the PC steel material 1.

  As described above, the main body piece 72c has a symmetrical shape with the main body piece 72a, and thus has the same end plate portion and spacer portion as the end plate portion 72a1 and the spacer portion 72a2. In addition, as described above, the main body piece 72d has a symmetrical shape with the main body piece 72b, and thus has the same end plate portion and spacer portion as the end plate portion 72b1 and the spacer portion 72b2.

  FIG. 6D is a view when the mold 70 is viewed from the direction of the arrow C shown in FIG. 6C. The main body piece 72b and the main body piece 72d are formed with recesses located around the PC steel material 1. These concave portions form a hole portion through which the PC steel material 1 is inserted when the main body pieces 72b and 72d are combined. Note that the hole through which the PC steel material 1 is inserted comes into contact with the PC steel material 1 to such an extent that molten metal does not leak during casting.

  In addition, when the formwork 70 is viewed from the direction opposite to the direction of the arrow C, the main body piece 72a and the main body piece 72c are combined, and the structure when combined is the same as the structure shown in FIG. 6D. Therefore, detailed description is omitted.

  Hereinafter, the pressure molding procedure will be described. First, in step B, casting molding is performed using the mold 70 described above, and only the second mold 72 is removed before the male member 61 is completely solidified. Thereby, a space is formed between the main body piece 71a and the main body piece 71b by the thickness of the spacer portions 72a2 and 72b2 in the direction orthogonal to the axial direction of the PC steel material 1. At this time, the main body piece 71a and the main body piece 71b can be moved toward each other by tightening the bolt 73a and the nut 73b. Thereby, the male member 61 can be pressure-molded.

  By performing the pressure molding by the above method, the male member 61 and the PC steel material 1 are strongly pressure-bonded as compared with the case where the pressure molding is not performed. Thereby, even if the tension | tensile_strength of the PC steel material 1 worked to the male member 61 at the subsequent process, the male member 61 becomes difficult to peel from the PC steel material 1.

  In FIG. 6A to FIG. 6D, the second mold 72 is used to form a space for moving the main body pieces 71a and 71b during pressure molding, but this may be omitted. For example, in the description using FIG. 2 (A) and FIG. 2 (B), the formwork 70 is comprised by two main body pieces, and these main body pieces are being fixed by the fastening member 62b. Here, the male member 61 can be pressure-molded by increasing the fastening force of the fastening member 62b to the main body piece.

  On the other hand, in the present embodiment, a sensor for detecting internal information of the concrete housing 2 can be installed in the suspension portion of the concrete housing 2 before the suspended portion of the concrete housing 2 is backfilled. Thereby, the internal information (for example, the prestressed which acts on the concrete frame 2) of the concrete frame 2 can be monitored. After installing the sensor, the hanger is backfilled with concrete. For example, a strain sensor can be used as the sensor. Moreover, in order to transmit the information detected by the sensor to the outside of the concrete frame 2, a signal line can be installed in the hanging part. For example, an optical fiber can be used as the signal line.

  In the present embodiment, a PC steel wire is used as the PC steel material 1. However, for example, a PC steel rod or a PC steel wire may be used. Moreover, what is necessary is just to be able to give the prestress necessary for the remaining part R1 after the dismantling of the dismantling part R2, and the number of PC steel materials 1 can be determined as appropriate.

  In the present embodiment, since the melted metal flows so as to fill the gaps between the plurality of PC steel materials 1 at the time of casting, the male member 61 is formed integrally with the plurality of PC steel materials 1 without a gap. The Therefore, regardless of the dense state of the plurality of PC steel materials 1, the male member 61 can be formed on the PC steel material 1, and the PC steel material 1 can be fixed by the intermediate fixing device 60. Further, it is not necessary to apply an external force to the PC steel material 1 to make it dense, and the PC steel material 1 can be prevented from being deteriorated due to breakage or wear.

  On the other hand, when the PC steel material 1 is a PC steel wire, on the surface of the PC steel material 1, a groove formed by twisting the PC steel wire extends spirally. Since the molten metal flows into the spiral groove at the time of casting, the male member 61 is formed integrally with the PC steel material 1 and meshed with the spiral groove. Thereby, the male member 61 can be firmly fixed to the PC steel material 1, and it is easy to suppress the relative movement of the PC steel material 1 and the male member 61 in the axial direction of the PC steel material 1.

  In the present embodiment, cast molding that does not require complicated work is performed on-site, and the male member 61 can be easily formed on the PC steel material 1, so intermediate fixing is simpler.

1: PC steel, 2: Concrete frame, 10: Intermediate part, 100: PC structure,
30: plate member, 50: jack, 60: intermediate fixing device, 61: male member,
62: female member, 62a: hole, 62c: through hole, 63: anchor,
70: Formwork, R1: Remaining part, R2: Dismantling part

Claims (8)

In an existing PC structure, an intermediate fixing method in which the PC steel material is intermediately fixed at the remaining part excluding the dismantling part,
A mold is attached to the PC steel material exposed by removing a part of the concrete frame of the PC structure,
An intermediate fixing member for prestressing the remaining portion is formed integrally with the PC steel material by filling the molten metal in the mold.
An intermediate fixing method characterized by this.   The intermediate fixing method according to claim 1, wherein the metal has a melting point of 300 ° C. to 400 ° C. The mold has a plurality of main body pieces divided in a direction orthogonal to the axial direction of the PC steel material,
The intermediate fixing method according to claim 1, wherein the metal filled in the mold is compression-molded by moving the plurality of main body pieces in a direction approaching the PC steel material. The intermediate fixing member is a wedge-shaped male member fitted with a female member,
Using a jack, by moving the female member in a direction from the remaining portion toward the dismantling portion, the male member is fitted to the female member,
Using the spacer device disposed between the removing portion of the concrete frame and the female member, the fitting state of the female member and the male member is maintained.
The intermediate fixing method according to any one of claims 1 to 3, wherein: In the state where the female member and the male member are fitted, by using the jack, the female member and the male member are moved in the direction from the remaining portion toward the dismantling portion, thereby the tension of the PC steel material. The intermediate fixing method according to claim 4, wherein the intermediate fixing method is increased.   6. The intermediate fixing method according to claim 4, wherein a portion of the male member protruding from the female member is covered with a cap before the removed portion of the concrete frame is backfilled with concrete. With jack, by from the leaving part Before moving the intermediate fixing member in a direction toward the dismantling unit, to increase the tension of the PC steel,
The intermediate fixing member is held at a position where the tension of the PC steel material is increased by using a spacer device disposed between the removal portion of the concrete frame and the intermediate fixing member.
The intermediate fixing method according to claim 1 or 2, wherein The intermediate according to any one of claims 1 to 7, wherein a sensor that detects internal information of the concrete frame is installed in the removal unit before the removal unit of the concrete frame is backfilled with concrete. Fixing method.