JP6247605B2 - PC steel set amount correction method - Google Patents

Description

  In the present invention, a new PC structure in which prestress is introduced into a concrete frame is tensioned and fixed using PC steel, or an existing PC structure in which prestress is introduced into a concrete frame is re-tensioned and fixed using PC steel. In particular, the present invention relates to a method for correcting a set amount generated after fixing, and more particularly, to a set amount correcting method capable of correcting a set amount by an easy operation without decentering a bearing state even in a narrow position. In the present invention, the PC steel material includes a PC steel wire and a PC steel stranded wire.

  The most common PC fixing system for fixing PC steel (PC cable) composed of PC steel wire or PC steel wire is composed of a casting block and an anchor head embedded in concrete. After tension, the PC steel wire or the PC steel wire is fixed to the anchor head by a wedge, and the fixing is completed by filling the casting block and the sheath with the grout from the grout hole provided in the casting block.

  Wedge fixing in such a fixing operation (using a fixing tool (fixing grip) consisting of a wedge and a sleeve with a taper), the PC steel wire is bitten on the inner periphery of the wedge, and the wedge outer periphery and the sleeve taper When fixing, the wedge protrudes to the outside of the sleeve. However, when the tension load of the jack is released (unloaded) at the time of fixing, the wedge moves into the sleeve due to the return (loosening) of the PC steel wire. The amount of set is generated by sinking, and the prestress is reduced by that amount (set loss). This set loss has a greater effect as the length of the wire (member length) is shorter than that of the PC steel, and the ratio to the design prestress is large, and it may be difficult to introduce the design prestress. For this reason, the operation | work which correct | amends this set amount is needed. As a method of this correction work, a ring nut method and a shim plate method are conventionally known.

As disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-231683 (Patent Document 1), the ring nut method uses a fixing tool attached with a ring nut that is screwed to a sleeve, and after being tensioned once, A tension stand (ram chair) is installed and re-tensioned, and the gap between the bearing plate and the fixing tool generated by the set amount is corrected by rotating the ring nut.
For example, as disclosed in Japanese Patent Application Laid-Open No. 2011-043025 (Patent Document 2), the shim plate method is re-installed with a reaction force stand after performing tension / fixing work using a normal fixing tool. Tension is applied, and correction is made by inserting a shim plate into the gap between the bearing plate and the fixing tool generated by the set amount.

JP 2007-231683 A JP 2011-043025 A

  However, although the method of correcting the set amount using the ring nut disclosed in Patent Document 1 is widely used, there is a problem that the outer diameter becomes large because the ring nut is attached to the outer periphery of the fixing tool. In addition, it cannot be applied to a multiple bundled fixing tool that is closely arranged so that the ring nuts interfere with each other. Further, it is necessary to rotate the ring nut several times, which requires a lot of work. There is a problem that it takes.

  Further, in the method of correcting the set amount using the shim plate disclosed in Patent Document 2, there is a problem that a half-shape is formed due to post-insertion, and the bearing state is decentered. There is a problem that a skilled technique is required to set the shim plate in the middle, and further, there is a problem that it is difficult to set and cannot be applied to a plurality of bundling fixing devices due to post-insertion.

  The present invention has been developed in view of the above-described problems of the prior art, and the object of the present invention is to correct the set amount by an easy operation without decentering the bearing state even in a narrow position. It is to provide a set amount correction method capable of performing the above.

In order to achieve the above object, the PC steel set amount correction method according to the present invention employs the following technical means.
That is, the PC steel set amount correction method according to the present invention corrects the PC steel set amount in a PC structure that applies a compressive force to the housing portion. The set amount correction method uses a combination of a first thin plate and a second thin plate having a shape centered on the axis of the PC steel. The first thin plate and the second thin plate have a plurality of planar first pressure bearing portions and a plurality of planar second pressure bearing portions, respectively, at predetermined central angle portions around the axis. The first thin plate and the second thin plate are placed around the axis from a first state where the first and second support portions do not overlap. By rotating it, it is possible to make a transition to the second state in which the first and second pressure bearing portions overlap each other. The first and second support pressure portions have uniform thicknesses, and the first support pressure portion is thinner than the second support pressure portion. In the set amount correction method, the first thin plate and the second thin plate in the first state are set between the pressure bearing plate and the fixing tool, and are thicker than the first pressure bearing portion. A tension fixing step of tensioning and fixing the PC steel material by supporting a tensile load by the second bearing portion; and tensioning and fixing the PC steel material in the tension fixing step; An installation step of installing a reaction force stand so that at least one of the second thin plates can rotate around the axis and covering the fixing tool; and a tensile load is supported by the reaction force stand. The second state by rotating at least one of the first thin plate and the second thin plate around the axis, and a tension step for secondarily tensioning the PC steel material at least for the set amount. In The thin plate rotating step to be transferred and the tensile load in the tensioning step are released, the tension force is supported by the first thin plate and the second thin plate in the second state, and the reaction force frame is removed. Post-processing steps.

  Preferably, the second thin plate has a substantially disc shape, and extends radially from a second annular portion having a central hole through which the PC steel material passes and an outer arc of the second annular portion. In addition, a plurality of second fan-shaped portions as the second support pressure portions and a rod-shaped portion provided on an outer arc of one of the plurality of second fan-shaped portions may be configured. it can. The first thin plate has a substantially disc shape, the first fan-shaped portion serving as the first supporting pressure portion corresponding to a portion where the second fan-shaped portion does not exist, and the plurality of first thin plates. A first annular portion connecting the outer arcs of one fan-shaped portion, and a portion corresponding to the rod-shaped portion in the first annular portion is cut out as an annular cutout portion. Can be configured. In the tension fixing step, the PC steel material is passed through the second annular portion in the first state in which the rod-like portion is matched with the annular notch portion, and between the bearing plate and the fixing tool. The first thin plate and the second thin plate in the first state are set, the tension step floats the second thin plate by at least a set amount, and the thin plate rotation step includes the second thin plate. By rotating the second thin plate around the axis using the rod-shaped portion, the second fan-shaped portion is superimposed on the first fan-shaped portion so as to transition to the second state. Can be configured.

More preferably, the thin plate rotating step is configured to rotate the rod-shaped portion of the second thin plate so as to face vertically downward so that the second fan-shaped portion overlaps the first fan-shaped portion. be able to.
More preferably, the first fan-shaped portion and the second fan-shaped portion can be configured so as to include four each at approximately 90 ° intervals, and the thin plate rotating step includes the step of rotating the second thin plate. The rod-shaped portion can be configured to rotate approximately 45 ° around the axis to overlap the second fan-shaped portion with the first fan-shaped portion.

More preferably, the first thin plate can be configured to further include a protrusion provided on an outer arc of the first annular portion, and the reaction force frame is fitted to the protrusion. It can comprise so that the fitting part to perform may be further provided. And the installation step is such that the first thin plate does not rotate around the axis when the fitting part is fitted to the protrusion, and the second thin plate is around the axis. The reaction force mount can be installed so that it can rotate.

  According to the set amount correcting method for PC steel according to the present invention, in a PC structure where a set amount has occurred in tension / fixing work, the set amount can be corrected by an easy operation without decentering the bearing state even in a narrow position. can do.

It is a figure which shows two shims (thin plate) used in the set amount correction method according to the embodiment of the present invention, (A) is a two-sided view of shim A (first thin plate), B) is a two-sided view of shim B (second thin plate). It is a figure which shows two shims (thin board) different from FIG. 1 used in the set amount correction | amendment method which concerns on embodiment of this invention, Comprising: (A) is two surfaces of shim A (1st thin board). (B) is a two-sided view of shim B (second thin plate). FIG. 3 is a three-sided view of a reaction force mount (chair) corresponding to the shim shown in FIG. 1. FIG. 3 is a three-side view of a reaction force mount (chair) corresponding to the shim shown in FIG. 2. It is a schematic diagram (the 1) which shows the procedure of the process of the set amount correction method which concerns on embodiment of this invention. It is a schematic diagram (the 2) which shows the procedure of the process of the set amount correction method which concerns on embodiment of this invention. It is a schematic diagram of the confirmation test of the set amount correction method according to the embodiment of the present invention, corresponding to FIG. 1 and FIG. It is a schematic diagram of the confirmation test of the set amount correction method according to the embodiment of the present invention, and corresponds to FIG. 2 and FIG.

  Hereinafter, a PC steel set amount correction method (hereinafter sometimes simply referred to as a set amount correction method) according to an embodiment of the present invention will be described in detail with reference to the drawings. The method for correcting the amount of PC steel set according to the present invention is an existing method in which prestress is introduced into a concrete frame even when a new PC structure that introduces prestress into a concrete frame is tensioned and fixed using PC steel. The present invention can also be suitably applied to a case where a PC structure is re-tensioned and fixed using PC steel for repair. The PC steel material in the present invention may be a PC steel wire or a PC steel wire composed of a plurality of steel wires, and one of the plurality of steel wires is composed of a plurality of thinner steel wires. It may be a wire or a single steel wire.

  The PC steel set amount correction method according to the present embodiment corrects the PC steel set amount at the time of fixing of the PC steel in the PC structure that applies a compressive force to the housing portion. In addition, as described above, the PC steel material at the time of re-fixing of the PC steel material remaining after cutting a part of the PC steel material for repair in the existing PC structure (for example, PC bridge) in which the compressive force is applied to the housing portion. Correct the set amount.

[Jig used for set amount correction method (dedicated product)]
Before explaining the set amount correction method according to the present embodiment, a jig used in this set amount correction method and having a special structure that matches this set amount correction method (dedicated Product).
This set amount correction method uses a combination of a first thin plate (Shim A100A and Shim A150A, which will be described later) and a second thin plate (Shim B100B and Shim B150B, which will be described later) having a shape centered on the axis of the PC steel material. At the same time, a reaction force stand (chair, reaction force stand 200 and reaction force stand 250 described later) is used during secondary tension. The material of the shim A100A and shim A150A and the shim B100B and shim B150B is SS400, and the material of the reaction force stand 200 and the reaction force stand 250 is S55C. However, the material is not limited to these materials. .

First thin plate (Shim A) and second thin plate (Shim B)
The first thin plate (shim A) has a plurality of planar first bearing parts (first fan-shaped part 100A4 and first fan described later) at a predetermined central angle centered on the axis. A shape portion 150A4). The second thin plate (shim B) also has a plurality of planar second pressure-supporting portions (second fan-shaped portion 100B4 and second fan described later) at a predetermined central angle centered on the axis. A shape portion 150B4). And these 1st thin plate (shim A) and 2nd thin plate (shim B) are 1st from the 1st state where the 1st bearing part and the 2nd bearing part do not overlap. By rotating at least one of the thin plate and the second thin plate around the axis, it is possible to shift to the second state in which the first and second support portions overlap. Furthermore, each of the first and second support pressure portions has a uniform thickness, and the first support pressure portions (first fan-shaped portion 100A4 and first fan-shaped portion 150A4) are It is thinner than the second pressure bearing part (second fan-shaped part 100B4 and second fan-shaped part 150B4).

  More specifically, the first thin plate (Shim A), the second thin plate (Shim B), and the reaction force mount (chair) used in the set amount correction method according to the present embodiment will be described with reference to FIGS. This will be described in detail with reference to FIG. In this embodiment, as an example of a PC steel material that imparts tension to a PC structure, seven strands of PC steel are used as a strand of φ12.4 mm × 12 and a single portion of PC steel is used as a φ7 mm × 12 single wire. Two types were adopted. Each has a first thin plate (Shim A) and a second thin plate (Shim B) and a reaction force stand (chair).

  Fig. 1 shows shim A100A and shim B100B for PC steel wire, Fig. 2 shows shim A150A and shim B150B for PC steel wire, and Fig. 3 shows a three-sided view of reaction force stand 200 for PC steel wire. FIG. 4 shows a three-sided view of a reaction force mount 250 for PC steel wire. More specifically, FIG. 1A shows a two-sided view of a shim A100A (first thin plate), FIG. 1B shows a two-sided view of a shim B100B (second thin plate), and FIG. ) Shows a two-sided view of shim A150A (first thin plate), and FIG. 2B shows a two-sided view of shim B150B (second thin plate).

  As shown in FIG. 1 (B) and FIG. 2 (B), shims B100B and 150B, which are second thin plates, are substantially disk-shaped, and are provided with center holes 100B8 and 150B8 through which PC steel is passed. A plurality of second fan-shaped portions 100B4, 150B4 as second supporting portions radially extending from the outer arcs of the second annular portions 100B2, 150B2, The rod-shaped parts 100B6 and 150B6 provided on the outer arc of the second fan-shaped part.

  As shown in FIG. 1 (A) and FIG. 2 (A), shims A100A and 150A, which are first thin plates, are substantially disk-shaped, and are not formed in the portions where the second fan-shaped portions 100B4 and 150B4 do not exist. 1st fan-shaped part 100A4, 150A4 as a corresponding 1st bearing part, and 1st ring part 100A2, 150A2 which connects the outer circular arc of several 1st fan-shaped part 100A4, 150A4 is provided. In the first annular portions 100A2 and 150A2, portions corresponding to the rod-shaped portions 100B6 and 150B6 described above are notched as annular notches 100A8 and 150A8. Further, the shim A100A and the shim A150A include projecting portions 100A6 and 150A6 extending outward from the outer peripheral arcs of the first annular portions 100A2 and 150A2. For details of the projecting portions 100A6 and 150A6, reaction force This will be described later together with the fitting portions 206 and 256 of the gantry 200 and 250.

  Here, the correspondence between the first fan-shaped portions 100A4 and 150A4 and the second fan-shaped portions 100B4 and 150B4, and the corresponding relationship between the annular cutout portions 100A8 and 150A8 and the rod-shaped portions 100B6 and 150B6. 5A, the first bearing part (first fan-shaped part 100A4, 150A4) and the second bearing part (second fan-shaped part 100B4, 150B4) do not overlap. It is defined in the state of 1.

  As shown in FIGS. 1 and 2, the first bearing part (first fan-shaped parts 100A4, 150A4) and the second bearing part (second fan-shaped parts 100B4, 150B4) are uniform. Thickness (t (A) and t (B)), and the first supporting pressure part (first fan-shaped part 100A4, 150A4) is the second supporting pressure part (second fan-shaped part). 100B4 and 150B4) (t (A) <t (B)).

  As described above, the first fan-shaped portions 100A4 and 150A4 and the second fan-shaped portions 100B4 and 150B4 have been described as being provided with four at approximately 90 ° intervals, but the present invention is limited to this. is not. The first fan-shaped portions 100A4 and 150A4 and the second fan-shaped portions 100B4 and 150B4 have shapes with the axis of the PC steel material as the center of symmetry, and are respectively formed at predetermined central angle portions around the axis. From the first state (see FIG. 5 (A)) in which the first fan-shaped portions 100A4, 150A4 and the second fan-shaped portions 100B4, 150B4 do not overlap with each other, the shims A100A, 150A and A second state in which the first fan-shaped portions 100A4 and 150A4 and the second fan-shaped portions 100B4 and 150B4 overlap each other by rotating at least one of the shims B100B and 150B around the axis (see FIG. 5E). As long as it is possible to make a transition to (), it may be a number other than four at an angular interval other than 90 °.

・ Reaction force stand (chair)
Next, with reference to FIG. 3 and FIG. 4, reaction force bases (chairs) 200 and 250 for supporting a tensile load in a tension step in which PC steel material is secondarily tensioned will be described.
The reaction force bases 200 and 250 support a tensile load in a tension step described later, and at least one of the first thin plate (Shim A) and the second thin plate (Shim B) is made of PC steel in the thin plate rotation step. In the installation step after the PC steel material is tensioned and fixed by the tension fixing step so as to be able to rotate around the axis, it is installed so as to cover the fixing tool. Note that the fitting portions 206 and 256 that are fitted to the protrusions 100A6 and 150A6 of the first thin plate (shim A) so as not to rotate the shim A around the axis of the PC steel material are provided as reaction force mounts 200 and 250, respectively. Can also be prepared.

  As shown in FIGS. 3 and 4, the reaction force bases 200 and 250 are substantially hollow cylindrical shapes, and pass a large diameter portion 202 having an inner diameter for covering a fixing tool, and a PC steel material. And a small-diameter portion 204 having an inner diameter. At the end of the small diameter portion 204, a hole portion 210 is provided for allowing the PC steel material to pass therethrough. At the end of the large-diameter portion 202, notches 208 and 258 for rotating the shims B100B and 150B using the rod-like portions 100B6 and 150B6 in order to transition from the first state to the second state, and shims Fitting portions 206 and 256 are provided to hold the shims A100A and 150A so that the shims A are not rotated by fitting into the protrusions 100A6 and 150A6 of the A100A and 150A. The reaction force bases 200 and 250 are installed so that the end surfaces 212 and 262 abut against the bearing plate 400 (so that the fitting portions 206 and 256 are fitted to the protrusions 100A6 and 150A6), and the PC steel material is subjected to secondary tension. In the tensioning step, the PC steel material is tensioned from the jack 600 from the end surfaces 214 and 264 side.

  As described above, the reaction force mounts 200 and 250 have been described as rotating the shim B without rotating the shim A, but the present invention is not limited to this. As long as the set amount described later can be corrected, the shim A may be rotated without rotating the shim B, or the shim A and the shim B may be rotated. Since it can be assumed that the shim A is rotated in this way, the fitting portions 206 and 256 of the reaction force bases 200 and 250 and the protrusions 100A6 and 150A6 of the shim A100A and 150A are not essential configurations in the present invention.

[Set amount correction method]
Shim A100A or shim A150A, shim B100B or shim B150B, and reaction force mount 200 or reaction jigs having a special structure matched with the set amount correction method according to the present embodiment as described above. A method for correcting the PC steel set amount using the force stand 250 will be described. Here, shim A100A, shim B100B and reaction force stand 200 are used together with PC steel strands (7 strands φ12.4 mm × 12 pieces), and shim A150A, shim B150B and reaction force stand 250 are PC steel wires (single wire) φ7 mm × 12), and the set amount correction method according to the present embodiment is realized.

This set amount correction method includes (1) a tension fixing step as a primary tension step, and a reaction force stand is installed after the tension fixing step (after a set amount to be corrected is generated). (3) Tension step as the next tension step, and the state of shims A and B in the second tension state are changed from the first state to the second state. (4) Thin plate rotation step, and the set amount is corrected And (5) a post-processing step.

  Hereinafter, each step will be described in detail with reference to FIGS. 5 and 6. 5 and 6, the state before the tension fixing step is shown in FIG. 6A, (1) the state of the tension fixing step is shown in FIGS. 5A and 6B, and (2) is installed. FIG. 5B shows the state of the step, FIG. 5C and FIG. 6C show the state of the tension step, and FIG. 5D shows the state of the thin plate rotation step. FIGS. 5 (E) and 6 (F) show the state after executing the post-processing step in (D) and (E), respectively. Moreover, the code | symbol in the following description describes the exclusive goods for wires from PC steel, and the exclusive goods for PC steel wires are described in brackets.

(1) Tension Fixing Step First, before the tension fixing step, as shown in FIG. 6 (A), the first state in the first state between the pressure plate 400 and the fixing tool 300 (wedge 310 and sleeve 320). A shim A100A (150A) which is a thin plate of 1 and a shim B100B (150B) which is a second thin plate are set.

More specifically, at this time, in the first state in which the rod-like portion 100B6 (150B6) is matched with the annular notch 100A8 (150A8), the second steel portion 500B8 (150B8) is made of the PC steel material 500 (here, PC). The shim A100A (150A) and shim B100B (150B) are set through the steel strand.
In this tension fixing step, as shown in FIGS. 5 (A) and 6 (B), the thickness t of the first fan-shaped portion 100A4 (150A4), which is the first bearing portion in the shim A100A (150A). The PC steel 500 is tensioned by supporting the tensile load by the thickness t (B) of the second fan-shaped portion 100B4 (150B4) which is the second supporting pressure portion of the shim B100B (150B), which is thicker than (A). And settle.

(2) Installation Step After tensioning and fixing the PC steel material 500 in the tension fixing step described above, as shown in FIG. 5 (B), the shim A100A (150A) that is the first thin plate and the second thin plate The reaction force stand 200 (250) is installed so that at least one of the certain shims B100B (150B) (here, the shims B100B (150B)) can rotate around the axis and covers the fixing device 300. .

  More specifically, in this installation step, the shim A 100A (150A) is formed by fitting the fitting portion 206 (256) of the reaction force rack 200 (250) to the protrusion 100A6 (150A6) of the shim A 100A (150A). The reaction force platform 200 (250) is provided so that the shim B100B (150B) can be rotated around the axis by operating the rod-like part 100B6 (150B6) from the notch 208 (258) so as not to rotate around the axis. ) Is installed.

(3) Tension step As shown in FIGS. 5C and 6C, a tensile load is supported by the reaction force rack 200 (250), and the jack steel 600 is used to at least set the PC steel material 500. Second tension.
More specifically, in this tensioning step, the second thin plate shim B100B (150B) is shown in FIG. 5C by being secondarily tensioned at least by the set amount by the tensile load in the direction indicated by the arrow X. Will float on. As a result, the shim B100B (150B) can rotate around the axis.

(4) Thin plate rotation step As shown in FIGS. 5 (D), 6 (D), and 6 (E), the first thin plate shim A100A (150A) and the second thin plate shim B100B (150B) Is shifted to the second state by rotating around at least one of them.
More specifically, in this thin plate rotation step, the operator grips the rod-like portion 100B6 (150B6) of the shim B100B (150B) with the finger or tool through the notch 208 (258) and rotates it in the direction indicated by the arrow R. By rotating the shim B100B (150B) around the axis, the second fan-shaped portion 100B4 (150B4) is overlapped with the first fan-shaped portion 100A4 (150A4) to make a transition to the second state.

  More specifically, in this thin plate rotation step, four first fan-shaped portions 100A4 (150A4) and four second fan-shaped portions 100B4 (150B4) are provided at intervals of approximately 90 °. It is preferable in that the operator can transition from the first state to the second state only by gripping the rod-like portion 100B6 (150B6) of the shim B100B (150B) with a finger or a tool and rotating it 45 degrees in the direction of arrow R.

  More specifically, in this thin plate rotating step, the rod-shaped portion 100B6 (150B6) of the shim B100B (150B) is rotated so as to face vertically downward to cause the second fan-shaped portion 100B4 (150B4) to move to the first fan. Overlay on shape part 100A4 (150A4). This is preferable in that the shim B100B (150B) in a rotatable state around the axis can naturally transition from the first state to the second state by gravity.

(5) Post-processing step After the processing of the thin plate rotation step described above, as a post-processing step, the tensile load in the tension step as the secondary tension step is released, and the shim A100A (150A) and shim B100B in the second state The tension is supported by (150B). Further, the reaction force mount 200 (250) is removed.

After this post-processing step, the state shown in FIGS. 5E and 6F is obtained.
Thus, according to the set amount correction method according to the present embodiment, in the PC structure in which the set amount is generated in the tension / fixing work,
(A) Since the shim A and the shim B do not have a large volume and only the shim B needs to be rotated slightly, the set amount can be corrected when the work space is narrow,
(B) Since shim A and shim B have a shape with the axis of the PC steel material as the center of symmetry, the set amount can be corrected without decentering the bearing state,
(C) Since it is only necessary to rotate the shim B slightly, the set amount can be corrected by an easy operation.

[Confirmation test]
About the set amount correction | amendment method which concerns on this Embodiment which expresses such an effect, the confirmation test was done simulating a construction site. The items to be confirmed were the workability of the set amount correction method (can be constructed) and the effectiveness of the set amount correction (must be corrected).
Fig. 7 is a schematic diagram of a confirmation test for PC steel wires with a diameter of 12.4 mm x 12 from 7 wires, and Fig. 8 is a confirmation test for PC wires with a single wire of 7 mm x 12 wires. A schematic diagram is shown respectively.

  As shown in FIG. 7 and FIG. 8, the PC steel materials to be arranged are in a bundle of 12 pieces in the central portion, but the PC steel materials that are tensioned and fixed are effective in the workability of the set amount correction method and the effectiveness of the set correction. It is assumed that there is a high possibility that a difference will occur, and that the angles are three (circle numbers 1 to 3). In addition, the tension load (allowable tensile force) per PC steel material is 0.7 Pu (70% of the maximum test force (standard breaking load)) in use, and 0.9 Py (0.2%) during tension work. 90% of the load with respect to permanent elongation (yield load). Specifically, in the case of PC steel strand (7 strands φ12.4 mm), 0.7 Pu = 112 kN and 0.9 Py = 12.4 kN, and in the case of PC steel wire (single wire φ7 mm), 0.7 Pu = 40.81 kN and 0.9Py = 45.9 kN.

The confirmation items are the workability of the set amount correction and the effectiveness of the set amount correction based on the tension load measured by the load cell.
・ About the workability of set amount correction FIG. 6 shows both the PC steel strand shown in FIG. 7 (7 strands φ12.4 mm × 12 wires) and the PC steel wire shown in FIG. 8 (single wire φ7 mm × 12 strands). As shown in Fig. 5, the set amount of all the locations was corrected, and the workability was confirmed.

In addition to the cutout portions 208 and 258 of the reaction force racks 200 and 250, one more cutout portion is added to check the rotation (movement) status of the shims B100B and 150B using the rod-like portions 100B6 and 150B6. It is also preferable to guide the movement (rotation) of the shims B100B and 150B.
・ Effectiveness of set amount correction The transition of tension load is shown in Table 1 for PC steel strands (7 strands φ12.4mm × 12) and in Table 2 for PC steel wires (single wire φ7mm × 12), respectively. . The following results were obtained from the relationship between the tension (0.7 Pu) for each PC steel material, the load difference (round numeral 3 in the table), and the correction amount (round numeral 7 in the table). Note that fixing load = tensile force−average value of load difference, corrected load = fixing load + average value of correction amount.

PC steel strand (7 strands φ12.4mm x 12 strands)
Tension: 112kN
Fixing load: 81.5kN (= 112-30.5)
Load after correction: 104.2 kN (= 81.5 + 22.7)
From these, the ratio of the fixing load to the tension is reduced to 72.8% (= 81.5 kN / 112 kN × 100) due to the generation of the set amount at the time of fixing, but the set amount correcting method according to the present embodiment Thus, after correction, the ratio of the corrected load to the tension is recovered to 93.0% (= 104.2 kN / 112 kN × 100), and 20.2% (93.0-72.8) is recovered.

PC steel wire (single wire φ7mm × 12)
Tension: 40.81kN
Fixing load: 23.31 kN (= 40.81-17.5)
Load after correction: 32.31 kN (= 23.31 + 9.0)
From these, the ratio of the fixing load to the tension is reduced to 57.1% (= 23.31 kN / 40.81 kN × 100) due to the generation of the set amount at the time of fixing, but the set amount according to the present embodiment. After correction by the correction method, the ratio of the corrected load to the tension is recovered to 79.2% (= 32.31kN / 40.81kN × 100) and 22.1% (79.2-57.1) is recovered. is made of.

As described above, 20.2% in the case of PC steel strand (twisted wire φ12.4mm × 12), and 22.1% in the case of PC steel wire (single wire φ7mm × 12), Both have recovered about 20%.
As described above, judging from the transition of the tension load, the load reduced by the set amount was corrected, and its effectiveness could be confirmed.

As described above, according to the set amount correction method of the PC steel material according to the present embodiment,
(A) Since the shim A and the shim B do not have a large volume, and the shim B only needs to be rotated slightly, the set amount can be corrected in a narrow work space.
(B) Since shim A and shim B have a shape with the axis of the PC steel material as the center of symmetry, the set amount can be corrected without decentering the bearing state,
(C) Since it is only necessary to rotate the shim B slightly, the set amount can be corrected by an easy operation.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is preferable for a method of correcting a set amount generated when prestress is applied by a PC steel material, and the set amount can be corrected by an easy operation without decentering a bearing state even in a narrow position. Particularly preferred.

100A, 150A Shim A (first thin plate)
100B, 150B Shim B (second thin plate)
200, 250 Reaction force stand (chair)
300 Fixing tool (fixing grip)
310 Wedge 320 Sleeve 400 Bearing plate 500 PC steel wire 600 Jack

Claims (5)

A PC steel set amount correction method in a PC structure for applying a compressive force to a casing portion, wherein the set amount correction method includes a first thin plate and a second thin plate having a shape centered on the axis of the PC steel material. In combination, the first thin plate and the second thin plate each have a plurality of planar first bearing portions and a plurality of planes at a predetermined central angle centered on the axis. The first thin plate and at least one of the second thin plates from a first state in which the first support pressure portion and the second support pressure portion do not overlap each other. By rotating either one around the axis, the first and second support pressure portions can be shifted to a second state where the first support pressure portion and the second support pressure portion are overlapped. Each of the second bearing portions has a uniform thickness, and the first supporting portion Pressure part thinner than the second Bearing unit,
The set amount correction method is:
The first thin plate and the second thin plate in the first state are set between the pressure bearing plate and the fixing tool, and pulled by the second pressure bearing portion that is thicker than the first pressure bearing portion. A tension fixing step of tensioning and fixing the PC steel material by supporting a load;
After tensioning and fixing the PC steel material in the tension fixing step, at least one of the first thin plate and the second thin plate can rotate around the axis and covers the fixing tool. In the installation step to install the reaction force mount,
A tension step in which a tensile load is supported by the reaction force frame and the PC steel material is secondarily tensioned for at least a set amount;
A thin plate rotating step of changing to the second state by rotating at least one of the first thin plate and the second thin plate around the axis;
A post-processing step of releasing the tensile load in the tension step and supporting the tension force by the first thin plate and the second thin plate in the second state, and removing the reaction force frame. Set amount correction method. The second thin plate has a substantially disc shape, the second annular portion having a central hole through which the PC steel material passes, and the second annular portion radially extending from an outer arc of the second annular portion. A plurality of second fan-shaped portions as two support portions, and a rod-shaped portion provided on an outer arc of one of the plurality of second fan-shaped portions,
The first thin plate has a substantially disc shape, the first fan-shaped portion serving as the first supporting pressure portion corresponding to a portion where the second fan-shaped portion does not exist, and the plurality of first thin plates. A first annular portion connecting outer circular arcs of one fan-shaped portion, and a portion corresponding to the rod-shaped portion in the first annular portion is notched as an annular notch,
In the tension fixing step, the PC steel material is passed through the second annular portion in the first state in which the rod-like portion is matched with the annular notch portion, and the first steel plate is interposed between the bearing plate and the fixing tool. Set the first thin plate and the second thin plate in state 1;
The tension step floats the second thin plate by at least a set amount,
In the thin plate rotating step, the second fan-shaped portion is turned into the first fan-shaped portion by rotating the second thin plate around the axis using the rod-shaped portion of the second thin plate. The set amount correction method according to claim 1, wherein the transition to the second state is performed again.   The set according to claim 2, wherein the thin plate rotating step rotates the second thin plate so that the rod-shaped portion of the second thin plate faces vertically downward to overlap the second fan-shaped portion with the first fan-shaped portion. Amount correction method. The first fan-shaped portion and the second fan-shaped portion are each provided with four at approximately 90 ° intervals,
The said thin plate rotation step rotates the said rod-shaped part of a said 2nd thin plate about 45 degree | times around the said shaft center, and overlaps the said 2nd fan-shaped part on the said 1st fan-shaped part. Item 4. The set amount correction method according to Item 3. The first thin plate further includes a protrusion provided on an outer arc of the first annular portion,
The reaction force mount further includes a fitting portion that fits into the protruding portion,
In the installation step, the second thin plate can be rotated around the axis so that the first thin plate does not rotate around the axis when the fitting portion is fitted to the protrusion. The set amount correction method according to any one of claims 2 to 4, wherein the reaction force mount is installed as described above.