Elongation measuring device

Abstract

To provide an elongation length measurement device allowing detection of displacement of a tip position of a PC steel bar without removing a tension device.SOLUTION: An elongation length measurement device 1 is provided to a PC tension device 3, wherein the PC tension device 3 comprises: a fixation nut 21 attached on a projecting part 7a of the PC steel bar 7; a tension rod 11 to which a tip part 7b of the PC steel bar 7 is inserted and attached; and a hydraulic jack 13 for applying force to the tension rod 11, and applies tension force to the PC steel bar 7, and wherein the elongation length measurement device 1 measures an elongation length of the PC steel bar 7. The elongation length measurement device 1 comprises: a measurement rod that is slidably inserted to the tension rod 11, is biased so that its one end is abutted to a right end surface 7c of the PC steel bar 7, and includes a part exposed out of the tension rod 11; and a displacement acquisition part for acquiring displacement of the exposed part of the measurement rod.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an elongation measuring device for measuring the elongation of a PC steel bar. [Background technology]

[0002] A known technology in this field is a jack for PC tendons described in Patent Document 1 below. In this type of tensioning of PC steel bars, the pressure applied to the PC steel bars and the amount of extension of the PC steel bars are managed. The jack in Patent Document 1 has a socket wrench that rotates the anchoring nuts that secure the PC steel bars, and the number of rotations of the socket wrench is detected to indirectly obtain the tightening allowance of the anchoring nuts as the amount of extension of the PC steel bars. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-318984 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to obtain the amount of extension of the PC steel bar with higher accuracy, it is preferable to eliminate as much as possible indirect elements that may include errors, such as the socket wrench, and obtain the amount of displacement of the tip position of the PC steel bar as directly as possible. For example, it is possible to remove the tensioning device after tensioning the PC steel bar and directly measure the amount of displacement of the tip position of the PC steel bar with a vernier caliper or the like. However, this method requires repeated tensioning of the PC steel bar and removal of the tensioning device until the amount of extension of the PC steel bar falls within the standard value, which increases the workload. In view of such problems, the present invention aims to provide an extension measuring device that can detect the amount of displacement of the tip position of the PC steel bar without removing the tensioning device. [Means for solving the problem]

[0005] The elongation measuring device of the present invention is an elongation measuring device that is installed on a PC tensioning device that applies tension to the PC steel rod and measures the elongation of the PC steel rod, and has a fixing nut that is attached to the protruding part of the PC steel rod that protrudes from a support plate on a structure on which the PC steel rod is installed, a tension rod having a PC mounting part at one end into which the tip of the PC steel rod that protrudes further from the fixing nut is inserted and attached, and a jack that takes up a reaction force against the support plate and applies a force to the tension rod in the protruding direction of the PC steel rod.The elongation measuring device is equipped with a measuring rod that is slidably inserted into the tension rod parallel to the protruding direction and receives a biasing force toward the tip surface of the PC steel rod, one end of which is abutted against the tip surface of the PC steel rod by the biasing force, and includes an exposed part exposed outside the tension rod.

[0006] The extension measuring device of the present invention may further include a displacement acquiring section that acquires the displacement of the exposed portion of the measuring rod.

[0007] The displacement acquisition unit may have a wire encoder including an encoder main body attached to the outer peripheral surface of the jack and a measuring wire extending from the encoder main body in a protruding direction, and a wire connection portion to which the measuring wire is connected, protruding from the exposed portion of the measuring rod in a direction intersecting the protruding direction.

[0008] The PC mounting portion has a PC insertion hole formed on one end face of the tension rod, into which the tip of the PC steel bar is inserted and held, and the measuring rod is inserted and slidable through a rod insertion hole that penetrates in the protruding direction from the PC insertion hole to the outside of the tension rod, with one end of the measuring rod abutting against the tip face of the PC steel bar within the PC insertion hole.

[0009] The elongation measuring device of the present invention is an elongation measuring device that is installed on a PC tensioning device that applies tension to the PC steel rod and measures the elongation of the PC steel rod, and has a fixing nut that is attached to the protruding part of the PC steel rod that protrudes from a support plate on a structure on which the PC steel rod is installed, a tension rod having a PC mounting part at one end into which the tip of the PC steel rod that protrudes further from the fixing nut is inserted and attached, and a jack that takes up a reaction force against the support plate and applies a force to the tension rod in the protruding direction of the PC steel rod, and is equipped with a displacement acquisition unit that acquires the displacement amount of the exposed part of the tension rod that is exposed outside the jack.

[0010] The displacement acquisition unit may have a wire encoder including an encoder main body attached to the outer peripheral surface of the jack and a measuring wire extending from the encoder main body in a protruding direction, and a wire connection portion to which the measuring wire is connected, protruding from the exposed portion of the tension rod in a direction intersecting the protruding direction. Effect of the Invention

[0011] According to the present invention, it is possible to provide an elongation measuring device that can detect the amount of displacement of the tip position of a PC steel bar without removing the tensioning device. [Brief description of the drawings]

[0012] [Figure 1] 1 is a side view showing the appearance of a PC tensioning device to which the extension amount measuring device of the first embodiment is applied. [Diagram 2] 3(a) to 3(c) are cross-sectional views showing different stages of a tensioning process for applying tension to a PC steel bar using the PC tensioning device of the first embodiment. [Diagram 3] 4 is an enlarged cross-sectional view showing the vicinity of the left end portion of the measuring rod. FIG. [Figure 4] 6(a) to 6(c) are cross-sectional views showing different stages of a tensioning process for applying tension to a PC steel bar using a PC tensioning device of a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (First embodiment) Hereinafter, an embodiment of an elongation measuring device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a side view showing the appearance of a PC tensioning device 3 to which an elongation measuring device 1 of this embodiment is applied. The PC tensioning device 3 is a device for applying tension to a PC steel bar 7 so as to apply prestress to a concrete structure 5. A sheath 9 is embedded in the concrete structure 5 so as to penetrate the interior, and the PC steel bar 7 is inserted into the sheath 9. One end of the PC steel bar 7 is disposed so as to protrude from one end side of the concrete structure 5 to the outside, and the PC tensioning device 3 is attached to this protruding portion. The other end of the PC steel bar 7 is not shown, but is assumed to have already been fixed to the other end side of the concrete structure 5 at the other end side of the concrete structure 5.

[0014] The PC tensioning device 3 includes a tension rod 11 attached to the PC steel bar 7, and a hydraulic jack 13 that applies pressure to the tension rod 11 to apply a tensile force to the PC steel bar 7. The hydraulic jack 13 has a ram portion 13b that expands and contracts in the left-right direction. A hydraulic port 13a for introducing and discharging hydraulic oil is provided on the outer circumferential surface of the hydraulic jack 13. An encoder body 15a of a wire encoder 15 is also attached to the outer circumferential surface of the hydraulic jack 13, and a nut rotating device 17 is also provided. The nut rotating device 17 engages with a fixing nut 21 (see FIG. 2) of the PC steel bar 7 via a predetermined mechanism, and rotates the fixing nut 21. The nut rotating device 17 is provided with a manual handle 17a for rotating the fixing nut 21.

[0015] 2(a)-(c) are cross-sectional views showing each stage of tensioning treatment for applying tension to the PC steel bar 7. FIG. 2(a)-(c) shows the internal structure and other features of the PC tensioning device 3 in an exaggerated manner, and does not accurately represent the shape and size of each part. In the following description, when words such as "right / left" and "rightward / leftward" are used, they correspond to right and left in FIG. 2. Note that the nut rotation device 17 is not shown in FIG. 2. FIG. 2(a) shows a stage before tensioning the PC steel bar 7, FIG. 2(b) shows a stage during tensioning in which the pressure of the hydraulic jack 13 is acting on the PC steel bar 7, and FIG. 2(c) shows a stage in which the fixing nut is moved and the pressure of the hydraulic jack 13 is released and the PC steel bar 7 is fixed. In the following, the stage in FIG. 2(a) is called the "pre-tensioning stage", the stage in FIG. 2(b) is called the "tensioning stage", and the stage in FIG. 2(a) is called the "fixing stage".

[0016] As shown in FIG. 2(a), a metal support plate 19 is installed on the surface of the concrete structure 5. The PC steel rod 7 inserted into the sheath 9 passes through a central hole in the support plate 19 and protrudes to the right from the concrete structure 5. The part of the PC steel rod 7 protruding to the right from the support plate 19 is called the "protruding part 7a." A male thread is formed in this protruding part 7a, and a fixing nut 21 is attached so as to be screwed into the male thread. The left end face of the fixing nut 21 is in contact with the support plate 19. The right part of the protruding part 7a protrudes further to the right from the right end of the fixing nut 21. The part of the PC steel rod 7 protruding further to the right from the right end of the fixing nut 21 is called the "tip part 7b."

[0017] The tension rod 11 is cylindrical and extends in the left-right direction. A bottomed PC insertion hole 23 (PC mounting portion) is formed in the left end surface of the tension rod 11, which is drilled toward the right and into which the tip 7b of the PC steel bar 7 is inserted and attached. A female thread is formed in the PC insertion hole 23, and the male thread of the tip 7b of the PC steel bar 7 is screwed into the female thread, so that the PC steel bar 7 and the tension rod 11 are firmly connected coaxially. The tension rod 11 is inserted through the center of the hydraulic jack 13. The right end of the tension rod 11 protrudes to the right from the hydraulic jack 13. A tension nut 27 is attached to the right end of the tension rod 11 protruding from the hydraulic jack 13. The left end surface of the tension nut 27 contacts the ram portion 13b of the hydraulic jack 13.

[0018] At the center of the tension rod 11, a rod insertion hole 11a is formed, which is coaxial with the PC insertion hole 23 and penetrates from the PC insertion hole 23 to the outside of the tension rod 11 in the left-right direction. A measuring rod 29 is inserted into the rod insertion hole 11a. The measuring rod 29 is guided by the rod insertion hole 11a and can slide in the rod insertion hole 11a in the axial direction (left-right direction). The left end of the measuring rod 29 enters the PC insertion hole 23 and contacts the right end surface 7c (tip surface) of the PC steel bar 7. The right end of the measuring rod 29 protrudes further to the right from the right end of the tension rod 11 and is exposed to the outside. The measuring rod 29 is biased leftward with respect to the tension rod 11, so that the left end of the measuring rod 29 is pressed against the right end surface 7c of the PC steel bar 7.

[0019] A specific biasing mechanism for biasing the measuring rod 29 as described above is shown in FIG. 3. FIG. 3 is a cross-sectional view showing an enlarged view of the left end portion of the measuring rod 29. A spherical portion 29a having a diameter larger than that of the rod insertion hole 11a is formed at the left end of the measuring rod 29. A coil spring 31 is installed in the vicinity of the spherical portion 29a so as to wind around the shaft portion of the measuring rod 29, and the coil spring 31 is sandwiched and compressed between the spherical portion 29a and the right end surface of the PC insertion hole 23. As described above, the measuring rod 29 is biased leftward relative to the tension rod 11 by the repulsive force of the coil spring 31, and the left end of the measuring rod 29 is pressed against the right end surface 7c of the PC steel bar 7. In FIG. 2, the detailed illustration of the biasing mechanism as described above is omitted to avoid complication of the figure.

[0020] The hydraulic jack 13 surrounds the left end of the tension rod 11 and the anchoring nut 21. Specifically, the tension rod 11 is held in a central hole extending in the left-right direction in the center of the hydraulic jack 13, and the anchoring nut 21 attached to the PC steel bar 7 at a position to the left of the tension rod 11 is also housed in this central hole. The left end of the hydraulic jack 13 abuts against the support plate 19. The hydraulic jack 13 may be composed of a jack main body that drives the ram portion 13b in the left-right direction and a ram chair that supports the jack main body and abuts against the support plate 19.

[0021] In the PC tensioning device 3 configured as above, when the hydraulic jack 13 is driven, the ram part 13b extends to the right as shown in FIG. 2(b), and the hydraulic jack 13 applies a reaction force to the support plate 19 and pushes the tension nut 27 to the right. Then, the tension nut 27 and the tension rod 11 move to the right inside the hydraulic jack 13, and the PC steel bar 7 is extended as if pulled by the tension rod 11 (tensioning stage). Then, the PC steel bar 7 extended inside the concrete structure 5 extends to the right from the support plate 19, and the fixing nut 21 floats from the support plate 19 and moves to the right. When the fixing nut 21 is rotated by the nut rotating device 17 from this state, the fixing nut 21 moves to the left and abuts against the support plate 19 as shown in FIG. 2(c). After that, the hydraulic pressure of the hydraulic jack 13 is released, and the right end of the PC steel bar 7 is fixed (fixing stage).

[0022] In the tensioning of the PC steel bar 7, it is necessary to control the pressure applied to the PC steel bar 7 by tensioning and the amount of elongation of the PC steel bar 7 by tensioning. The amount of elongation of the PC steel bar 7 to be controlled here is the amount of elongation of the part of the PC steel bar 7 that was inserted into the concrete structure 5 in the pre-tensioning stage (FIG. 2(a)), and does not include the amount of elongation of the protruding part 7a. The protruding part 7a is slightly elongated together with the fixing nut 21 and the PC insertion hole 23 by the pressure of the hydraulic jack 13 in the tensioning stage (FIG. 2(b)), but in the fixing stage (FIG. 2(c)), the pressure of the hydraulic jack 13 is released and the protruding part 7a returns to the length of the pre-tensioning stage (FIG. 2(a)). Therefore, the displacement of the right end surface 7c of the PC steel bar 7 in the fixing stage (FIG. 2(c)) based on the pre-tensioning stage (FIG. 2(a)) corresponds to the amount of elongation of the PC steel bar 7 to be controlled.

[0023] The PC tensioning device 3 is equipped with an extension measuring device 1 for measuring the displacement of the right end face 7c of the PC steel bar 7 as the extension of the PC steel bar 7. The extension measuring device 1 is equipped with the above-mentioned measuring rod 29 and a displacement acquiring unit 33 for acquiring the displacement of an exposed portion 29c of the measuring rod 29 that is exposed to the outside of the tension rod 11 at the right end side. The displacement acquiring unit 33 has a wire encoder 15 and a wire connecting fitting 35 (wire connecting portion) interposed between the wire encoder 15 and the measuring rod 29. The wire connecting fitting 35 is attached to the exposed portion 29c of the measuring rod 29 and protrudes from the exposed portion 29c toward the outside in the radial direction of the PC steel bar 7.

[0024] As described above, the wire encoder 15 includes the encoder body 15a attached to the outer circumferential surface of the hydraulic jack 13, and the measuring wire 15b extending rightward from the encoder body 15a. The wire encoder 15 detects the amount of displacement of the tip of the measuring wire 15b by detecting the amount of the measuring wire 15b pulled out from the encoder body 15a. Since such a wire encoder 15 is well known, further detailed description will be omitted. The right end of the measuring wire 15b is connected to the outer circumferential end of the wire connecting fitting 35, and the measuring wire 15b extends parallel to the extension direction of the PC steel bar 7.

[0025] According to the elongation measuring device 1 having the above-mentioned structure, when the PC tensioning device 3 applies tension to the PC steel rod 7 and the PC steel rod 7 elongates, the right end face 7c of the PC steel rod 7 moves rightward with respect to the concrete structure 5 and the support plate 19. Then, the measuring rod 29 and the wire connection fitting 35 pressed against the right end face 7c also follow and displace to the right by the same amount. Then, the measuring wire 15b is pulled out from the encoder main body 15a by the same amount as the rightward displacement of the wire connection fitting 35, and the measurement value of the wire encoder 15 is obtained.

[0026] Therefore, with the elongation measuring device 1, by taking the difference between the measurement values ​​by the wire encoder 15 in the pre-tensioning stage and the fixing stage of the PC steel bar 7, it is possible to obtain the displacement amount of the right end face 7c of the PC steel bar 7 and, ultimately, the elongation amount of the PC steel bar 7 to be managed. As a specific method, the measurement value of the wire encoder 15 in the pre-tensioning stage is set to zero in advance, and the measurement value of the wire encoder 15 in the fixing stage is taken as the elongation amount of the PC steel bar 7 to be managed and is recorded in a database for tension management of the PC steel bar 7, for example.

[0027] The effect of such an elongation measuring device 1 will be described. In tensioning the PC steel bar 7, the elongation of the PC steel bar 7 must be within a standard value, and the standard value is, for example, a design value of ±0.5 mm, so high accuracy is required for measuring the elongation. In order to measure the elongation of the PC steel bar 7 with high accuracy, it is preferable to eliminate indirect factors that may include errors as much as possible and directly obtain the displacement of the right end face 7c of the PC steel bar 7. For example, in the past, after tensioning the PC steel bar, the elongation measuring device would be removed and the displacement of the position of the right end face of the PC steel bar would be directly measured with a caliper or the like, and this task would be repeated until the elongation falls within the standard value.

[0028] In contrast, according to the elongation measuring device 1, a measuring rod 29 is inserted into the tension rod 11, and one end of the measuring rod 29 is abutted against the right end face 7c of the PC steel bar 7. The other end of the measuring rod 29 is exposed to the outside of the tension rod 11, and the displacement amount of this other end is acquired by the displacement amount acquiring unit 33. Therefore, during the fixing stage, the displacement amount of the right end face 7c of the PC steel bar 7 (i.e., the elongation amount of the PC steel bar 7 to be managed) can be directly measured without removing the PC tensioning device 3 from the PC steel bar 7.

[0029] Furthermore, according to the extension amount measuring device 1, even in the tensioning stage, the displacement amount of the right end face 7c of the PC steel bar 7 can be measured without removing the PC tensioning device 3 from the PC steel bar 7. Then, by applying a predetermined correction calculation to this measurement value, the displacement amount of the right end face 7c when moving to the fixing stage (i.e., the extension amount of the PC steel bar 7 to be managed) can be calculated. Therefore, when this calculated value reaches a standard value, it is sufficient to move from the tensioning stage to the fixing stage. In other words, in the tensioning stage, it is not necessary to release the pressure of the hydraulic jack 13 or remove the PC tensioning device 3 to check the extension amount, and it is sufficient to drive the hydraulic jack 13 until the above calculated value reaches the standard value and then move to the fixing stage.

[0030] The above correction calculation will be explained. In the tensioning stage, the protruding portion 7a of the PC steel bar 7 is also slightly elongated by the pressure of the hydraulic jack 13, so the measurement value obtained in the tensioning stage includes the elongation amount of the protruding portion 7a in addition to the elongation amount of the PC steel bar 7 to be managed. When the stage moves to the fixing stage, the pressure of the hydraulic jack 13 is released, and the elongation amount of the protruding portion 7a returns to zero. Therefore, the displacement amount of the right end face 7c when the stage moves to the fixing stage (i.e., the elongation amount of the PC steel bar 7 to be managed) is obtained by performing a correction calculation to remove the elongation amount of the protruding portion 7a from the measurement value obtained in the tensioning stage. In order to make such a correction calculation possible, it is necessary to obtain the elongation characteristics of the protruding portion 7a in advance by experiment or the like.

[0031] Therefore, the extension measuring device 1 can detect the extension amount of the PC steel bar 7 that must be managed even during the tensioning stage, making it possible to check whether the extension amount has reached a standard value without frequently releasing the pressure of the hydraulic jack 13. Also, because the measuring rod 29 is slidably inserted into the tension rod 11, even if the tension rod 11 expands or contracts due to the pressure of the hydraulic jack 13, this expansion or contraction does not affect the measuring rod 29. Therefore, the above correction calculation does not include any factors related to the expansion or contraction of the tension rod 11, making it possible to simplify the correction calculation.

[0032] Second embodiment Next, a PC tensioning device 53 according to a second embodiment of the present invention will be described with reference to Fig. 4. In the PC tensioning device 53, the measuring rod 29 (Fig. 2) in the PC tensioning device 3 of the first embodiment is omitted, and instead of the wire connection fitting 35 (Fig. 2), a wire connection fitting 65 is attached to the right end of the tension rod 11. Other than this, the configuration of the PC tensioning device 53 is the same as that of the PC tensioning device 3, so in the drawings, the same reference numerals are used for the same or equivalent components, and duplicate explanations will be omitted.

[0033] 4(a) shows the "pre-tensioning stage" before tension is applied to the PC steel rods 7, Fig. 2(b) shows the "tensioning stage" during tensioning when the pressure of the hydraulic jack 13 is acting on the PC steel rods 7, and Fig. 2(c) shows the "anchoring stage" when the anchoring nut has been moved and the pressure of the hydraulic jack 13 has been released. The operation of the PC tensioning device 53 in each stage is similar to that of the PC tensioning device 3 in the first embodiment, so detailed explanations will be omitted.

[0034] The extension measuring device 51 provided in the PC tensioning device 53 has a displacement acquisition unit 63 that acquires the displacement of the exposed portion 11c of the tension rod 11 that protrudes to the right from the hydraulic jack 13 and is exposed to the outside. The displacement acquisition unit 63 has a wire encoder 15 and a wire connecting fitting 65. The wire connecting fitting 65 is attached to the right end of the tension rod 11 and protrudes outward in the radial direction of the PC steel bar 7. The right end of the measuring wire 15b of the wire encoder 15 is connected to the outer circumferential end of the wire connecting fitting 65, and the measuring wire 15b extends parallel to the extension direction of the PC steel bar 7.

[0035] With the PC tensioning device 53 and the extension amount measuring device 51 having such a structure, the displacement amount of the right end surface 7c of the PC steel bar 7 (i.e., the extension amount of the PC steel bar 7 to be managed) can be measured in the fixing stage (FIG. 4(c)) without removing the PC tensioning device 3 from the PC steel bar 7. Furthermore, with the extension amount measuring device 51, the displacement amount of the right end surface 7c of the PC steel bar 7 can be measured in the tensioning stage without removing the PC tensioning device 53 from the PC steel bar 7. Then, by applying a predetermined correction calculation to this measurement value, the displacement amount of the right end surface 7c in the case of moving to the fixing stage (i.e., the extension amount of the PC steel bar 7 to be managed) can be calculated. Therefore, when this calculated value reaches a standard value, it is sufficient to move from the tensioning stage to the fixing stage. That is, in the tensioning stage, it is not necessary to release the pressure of the hydraulic jack 13 or remove the PC tensioning device 53 to check the extension amount, and it is sufficient to drive the hydraulic jack 13 until the above calculated value reaches the standard value and move to the fixing stage.

[0036] The above correction calculation will be explained. In the extension amount measuring device 51, the wire connection fitting 65 is attached to the right end of the tension rod 11, and in the tensioning stage, the protruding portion 7a of the PC steel bar 7 and the tension rod 11 are also slightly extended. Therefore, the measurement value obtained in the tensioning stage includes the extension amount of the protruding portion 7a and the extension amount of the tension rod 11 in addition to the extension amount of the PC steel bar 7 to be managed. After that, when the stage moves to the fixing stage, the pressure of the hydraulic jack 13 is released, and the extension amount of the protruding portion 7a and the extension amount of the tension rod 11 return to zero. Therefore, the displacement amount of the right end surface 7c when the stage moves to the fixing stage (i.e., the extension amount of the PC steel bar 7 to be managed) is obtained by performing a correction calculation to remove the extension amount of the protruding portion 7a and the extension amount of the tension rod 11 from the measurement value obtained in the tensioning stage. In order to make such a correction calculation possible, it is sufficient to obtain the extension characteristics of the protruding portion 7a and the tension rod 11 in advance by experiment or the like.

[0037] Therefore, like the extension amount measuring device 1 of the first embodiment, the extension amount measuring device 51 can detect the extension amount of the PC steel bar 7 to be managed even during the tensioning stage, making it possible to check whether the extension amount has reached the standard value without frequently releasing the pressure of the hydraulic jack 13. Compared to the extension amount measuring device 1 of the first embodiment, the extension amount measuring device 51 of this embodiment includes an element related to the expansion and contraction of the tension rod 11 in the above correction calculation, making the correction calculation somewhat more complicated. In other words, the extension amount measuring device 1 of the first embodiment is preferable to the extension amount measuring device 51 of this embodiment in that the correction calculation can be made simpler.

[0038] The present invention can be implemented in various forms including the above-described embodiment and various modifications and improvements based on the knowledge of those skilled in the art. In addition, it is possible to configure modified examples by utilizing the technical matters described in the above-described embodiment. The configurations of each embodiment may be used in appropriate combination.

[0039] For example, the displacement amount acquiring unit 33 in the first embodiment is not limited to a configuration using the wire encoder 15, and may be configured to acquire the displacement amount of the exposed portion 29c of the measuring rod 29 by combining various other devices. In addition, it is not essential that the extension amount measuring device 1 includes the displacement amount acquiring unit 33. For example, the displacement amount of the exposed portion 29c based on the outer circumferential surface of the support plate 19 or the hydraulic jack 13 may be measured manually by an operator using a caliper or the like. In addition, in the second embodiment, the displacement amount acquiring unit 63 is not limited to a configuration using the wire encoder 15, and may be configured to acquire the displacement amount of the exposed portion 11c of the tension rod 11 by combining various other devices. [Explanation of symbols]

[0040] 1,51...elongation measuring device, 3,53...PC tensioning device, 5...concrete structure, 7...PC steel rod, 7a...protruding portion, 7b...tip portion, 7c...right end face (tip face), 11...tension rod, 11a...rod insertion hole, 11c...exposed portion, 13...hydraulic jack, 15...wire encoder, 15a...encoder main body, 15b...measuring wire, 19...support plate, 21...fixing nut, 23...PC insertion hole (PC mounting portion), 29...measuring rod, 29c...exposed portion, 33,63...displacement acquisition portion, 35,65...wire connection fitting (wire connection portion).

Claims

1. an extension amount measuring device that is attached to a PC tensioning device that applies tension to the PC steel rod and measures the extension amount of the PC steel rod, the device comprising: an anchoring nut that is attached to a protruding portion of the PC steel rod that protrudes from a support plate on a structure on which the PC steel rod is installed; a tension rod having a PC attachment portion at one end into which a tip end of the PC steel rod that protrudes further from the anchoring nut is inserted and attached; and a jack that receives a reaction force from the support plate and applies a force to the tension rod in the protruding direction of the PC steel rod, the device being attached to a PC tensioning device that applies tension to the PC steel rod and measures the extension amount of the PC steel rod, An extension measuring device comprising a measuring rod that is slidably inserted into the tension rod in a direction parallel to the protruding direction and receives a biasing force toward the tip surface of the PC steel rod, one end of which is abutted against the tip surface of the PC steel rod by the biasing force, and includes an exposed portion exposed to the outside of the tension rod.

2. The extension measuring device according to claim 1 , further comprising a displacement acquisition unit that acquires the displacement of the exposed portion of the measuring rod.

3. The displacement amount acquisition unit a wire encoder including an encoder body attached to an outer peripheral surface of the jack and a measurement wire extending from the encoder body in the protruding direction; 3. The extension measuring device according to claim 2, further comprising: a wire connection portion extending from said exposed portion of said measuring rod in a direction intersecting said protruding direction and to which said measuring wire is connected.

4. The PC mounting portion has a PC insertion hole formed in an end surface of the one end of the tension rod and into which the tip end of the PC steel rod is inserted and held, The extension measuring device described in claim 2 or 3, wherein the measuring rod is inserted and slidable through a rod insertion hole that penetrates in the protruding direction from the PC insertion hole to the outside of the tension rod, and one end of the measuring rod is abutted against the tip surface of the PC steel rod within the PC insertion hole.

5. an extension amount measuring device that is attached to a PC tensioning device that applies tension to the PC steel rod and measures the extension amount of the PC steel rod, the device comprising: an anchoring nut that is attached to a protruding portion of the PC steel rod that protrudes from a support plate on a structure on which the PC steel rod is installed; a tension rod having a PC attachment portion at one end into which a tip end of the PC steel rod that protrudes further from the anchoring nut is inserted and attached; and a jack that receives a reaction force from the support plate and applies a force to the tension rod in the protruding direction of the PC steel rod, the device being attached to a PC tensioning device that applies tension to the PC steel rod and measures the extension amount of the PC steel rod, An extension amount measuring device including a displacement amount acquiring unit that acquires the displacement amount of an exposed portion of the tension rod that is exposed to the outside of the jack.

6. The displacement amount acquisition unit a wire encoder including an encoder body attached to an outer peripheral surface of the jack and a measurement wire extending from the encoder body in the protruding direction; 6. The extension measuring device according to claim 5, further comprising: a wire connection portion extending from the exposed portion of the tension rod in a direction intersecting the protruding direction and to which the measuring wire is connected.

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