Measuring device for evaluating the PC grout filling condition of concrete structures and evaluation method for the PC grout filling condition using the same

Abstract

To provide a measuring device which is simple in configuration, can easily perform short-time measurement, and can accurately grasp a PC grout filling state even when the sheath diameter is small, and an evaluation method using the same.SOLUTION: The measuring device includes an exciting coil having two magnetic pole end surfaces facing a measurement surface of a to-be-measured object, a pulse generating part applying a pulse current to the exciting coil, a detection coil composed of a circumferential conductor placed on a plane containing the two magnetic pole end surfaces of the excitation coil and spaced apart from the axis connecting the two magnetic pole end surfaces, a measurement part that measures an induced current generated in the detection coil, a calculation part that calculates an estimated electromagnetic force signal as measurement data by a product with a time integral of the induced current on the basis of the induced current measured by the measurement part, a storage part that registers the measurement data and pre-registers reference data, an evaluation part that compares the measurement data and the reference data to evaluate the state of the to-be-measured object, and a display part that displays the evaluation result obtained by the evaluation part and the measurement data.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a measuring device for evaluating the PC grout filling state in, for example, a post-tensioned concrete structure in which a sheath and PC steel are embedded, and a method for evaluating the PC grout filling state using the same. [Background technology]

[0002] As shown in Fig. 12(A), in a post-tensioned concrete structure 20 in which a sheath 21 and PC steel 22 are embedded, the inside of the sheath is generally filled with PC grout 21a to stably hold the PC steel 22 in the sheath 21, thereby suppressing corrosion of the PC steel 22 and integrating the PC steel 22, the sheath 21, and the concrete member. Therefore, as shown in Fig. 12(B) and (C), if the sheath 21 is not sufficiently filled with PC grout 21a, the durability and safety of the concrete structure 20 will be impaired.

[0003] For example, Non-Patent Document 1 reports an evaluation of PC grout filling using the electromagnetic field response of the sheath and steel rod excited by an electromagnetic input method. According to this paper, a pulsed excitation current is passed through an excitation coil by a pulse current generator, and a steep magnetic field is excited in the excitation coil. This magnetic field acts on the sheath and steel rod, causing them to vibrate. When the PC grout is filled, the steel rod is restrained and the vibration is small, but when the PC grout is not filled, the vibration becomes large, and the PC grout filling status is evaluated by detecting this using the electromagnetic field response. Here, the magnetic flux density near the sheath and steel rod is detected by search coils installed on the sheath and steel rod, respectively. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Shinichi Hattori, Daiki Kibe, Hiroki Terasawa, and Toshiro Kamata, "Evaluation of PC grout filling using electromagnetic field response of sheath and steel rod excited by electromagnetic input method," Proceedings of the Japan Concrete Institute, Vol. 41, No. 1, 2019, P1793-1798 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in some cases, such as when the sheath diameter is small compared to the buried depth of the sheath, it is difficult to fully grasp the state of grout filling inside the sheath. In addition, in the conventional impact elastic wave method, it is necessary to position and fix the excitation coil for applying an impact to the sheath and the detection coil for detecting the induced current based on the vibration caused by the shock wave, respectively, relative to the concrete structure, which makes the work required for measurement complicated and takes a long time to grasp the state of PC grout filling.

[0006] Furthermore, in the case of Non-Patent Document 1, in order to detect the vibration of the sheath along with the vibration of the steel rod, it is necessary to process the detection signals from the search coils installed at each measurement point on the concrete surface. Since the detection signals from the two search coils must be processed separately, the structure becomes complicated and the work time becomes long to evaluate the PC grout filling condition at each of the measurement points along the longitudinal direction of the sheath.

[0007] In view of the above, the present invention aims to provide a measuring device with a simple configuration that can perform measurements easily and quickly, and can accurately grasp the PC grout filling state even when the sheath diameter is small, and a method for evaluating the PC grout filling state using this measuring device. [Means for solving the problem]

[0008] In order to achieve the above object, a first configuration of the present invention includes an excitation coil having two magnetic pole tip faces with different polarities in an excited state, which are arranged to face a measurement surface of an object to be measured, a pulse generating unit which applies a pulse current to the excitation coil, a detection coil which is arranged on a plane including the two magnetic pole tip faces of the excitation coil and spaced apart from an axis connecting the two magnetic pole tip faces, a measurement unit which measures an induced current generated in the detection coil, a calculation unit which calculates an estimated electromagnetic force signal as measurement data by multiplying the induced current measured by the measurement unit by a time integral of the induced current, a memory unit which registers the measurement data and also registers reference data in advance, an evaluation unit which compares the measurement data with the reference data read out from the memory unit to evaluate the state of the object to be measured, and a display unit which displays the evaluation results by the evaluation unit and the measurement data, the pulse generating unit is composed of a charging circuit and a discharge circuit including a capacitor which is charged by the charging circuit and is connected in parallel to the exciting coil via a discharge switch circuit, the capacitor is composed of a plurality of capacitors connected in series and parallel, each having a predetermined withstand voltage, the total withstand voltage of the plurality of capacitors is set to be equal to or greater than the predetermined withstand voltage, the wiring resistance r of the discharge circuit and the capacitance C of the capacitor are selected so that the discharge circuit satisfies a critical damping condition, and the exciting coil and the detection coil are integrated so that their positional relationship does not change, The detection coil is made of a surrounding conductor, and the detection surface defined by the surrounding conductor is arranged parallel to the measurement surface. The magnetic pole end surface of the excitation coil is disposed with a predetermined gap from the measurement surface or is spaced apart via a non-magnetic, non-conductive solid spacer of a predetermined thickness, and the gap or the thickness of the solid spacer is configured to be adjustable with respect to the measurement surface. It is characterized by:

[0009] In the above configuration, preferably, an excitation coil, Detection coil, The pulse generating unit, the measuring unit, the computing unit, the memory unit and the evaluation unit are housed inside one housing, and the display unit is provided on the surface of the housing. However, preferably, it is inelastic. The detection coil preferably has a coil shape expanding in a direction perpendicular to the longitudinal direction of the PC steel of a post-tensioned concrete structure in which the PC steel is embedded in a sheath as the measurement object and filled with grout material. The detection coil preferably comprises a plurality of coils in a direction perpendicular to the longitudinal direction of the PC steel of a post-tensioned concrete structure in which the PC steel is embedded in a sheath as the measurement object and filled with grout material.

[0010] In order to achieve the above-mentioned object, a second configuration of the present invention is characterized by comprising a first step in which the above-mentioned measuring device is used to apply a pulse current to the excitation coil by a pulse generating unit to impact the measurement surface of the concrete structure, with both magnetic pole end faces of the excitation coil facing the longitudinal direction of the sheath of a post-tensioned concrete structure in which PC steel is embedded in a sheath as a measurement object and grout material is filled in the sheath; a second step in which the measurement unit measures the induced current generated in the detection coil in response to the electromagnetic field due to the impact and the calculation unit calculates the measurement data; a third step in which the evaluation unit compares the measurement data with reference data to evaluate the PC grout filling state in the sheath of the concrete structure; and a fourth step in which the evaluation result is displayed on a display unit.

[0011] In the above method, preferably, the reference data is measurement data at a measurement point where it is known in advance that PC grout is filled, and the evaluation unit compares the measurement data with the reference data to evaluate the PC grout filling state within the sheath of the concrete structure that is the object of measurement. The evaluation unit preferably evaluates the PC grout filling status as filled, poorly filled or unfilled by comparing the difference between the measurement data and the reference data as a first evaluation index value and a predetermined threshold value. Preferably, a pulse current is applied to the excitation coil at each of a plurality of measurement points along the longitudinal direction of the sheath of the concrete structure, an induced current generated in the detection coil is measured, and the measurement data is calculated, and an evaluation unit creates two-dimensional coordinate information consisting of the measurement data at each measurement point and position information of the measurement point, and the evaluation unit generates a second evaluation index value from the two-dimensional coordinates and the distribution of the first evaluation index value, and evaluates the extent of filling or unfilling with PC grout based on the second evaluation index value. The evaluation unit preferably causes the display unit to display the first evaluation index value and the evaluation result of the PC grout filling state for each measurement point. Preferably, a pulse current is applied to the excitation coil at each of a plurality of measurement points along the longitudinal direction of the sheath of the concrete structure, an induced current generated in the detection coil is measured, and the measurement data is calculated. An evaluation unit sequentially generates a first evaluation index value for each measurement point, and if the first evaluation index value continuously exceeds a threshold value, the PC grout filling state is evaluated as unfilled or improperly filled. Preferably, for a plurality of measurement points, in the region of the bent-up portion of the sheath, a pulse current is applied to the excitation coil in sequence from bottom to top, an induced current generated in the detection coil is measured, the measurement data is calculated, and a first evaluation index value is generated, and the first evaluation index value at each measurement point is compared in sequence with a threshold value by an evaluation unit, and when the first evaluation index value exceeds the threshold value consecutively, the PC grout filling state is evaluated as unfilled or improperly filled. For a plurality of measurement points, it is preferable to select a short interval between a measurement point where the PC grout filling state is evaluated as unfilled or improperly filled and the measurement points before and after that where the PC grout filling state is evaluated as filled. Effect of the Invention

[0012] According to the present invention, it is possible to provide a measuring device with a simple configuration that can perform measurements easily and in a short time, and that can accurately grasp the PC grout filling state even when the sheath diameter is small, and a method for evaluating the PC grout filling state using this measuring device. [Brief description of the drawings]

[0013] [Figure 1] 1 is a block diagram showing an overall configuration of an embodiment of a measurement device according to the present invention; [Diagram 2] 2A is a schematic side view of an excitation coil in the measurement device of FIG. 1, (B) is a schematic bottom view of the excitation coil, and (C) is a schematic plan view of a detection coil. [Diagram 3] 2 is a wiring diagram showing a configuration example of a pulse generating unit in the measurement device of FIG. 1. [Figure 4] 3 is a graph showing a waveform of a pulse generated by the pulse generating unit of FIG. 2. [Diagram 5] 2 is an explanatory diagram showing the processes of a measurement unit, a calculation unit, and an evaluation unit in the measurement device of FIG. 1. [Figure 6] FIG. 2A is a schematic plan view of the measuring device in FIG. 1, FIG. 2B is a schematic front view of the device in use, and FIG. 2C is a schematic perspective view showing the positional relationship of a measurement object to a concrete structure. [Figure 7] 2 shows the positional relationship of the excitation coil and detection coil with respect to the measurement surface of the concrete structure during measurement operation of the measurement device of FIG. 1, where (A) is an enlarged side view, (B) is a front view, and (C) is an enlarged plan view of the main part. [Figure 8] 2A and 2B are explanatory diagrams illustrating generation of a magnetic field by an excitation coil, generation of an electromagnetic force, and generation of an induced current during measurement by the measurement device of FIG. 1. [Figure 9] 2A is a schematic diagram showing multiple measurement points and unfilled and insufficiently filled areas B of the PC grout using the measurement device of FIG. 1, and (B) a graph showing the two-dimensional coordinate positions of the evaluation values ​​obtained by measurements at each measurement point. [Figure 10] 2A is a schematic diagram showing a distance d between a detection surface of a detection coil and a sheath of a concrete structure in the measurement device of FIG. 1, and FIG. 2B is a graph showing the relationship between the distance d and measurement data. [Figure 11] 2 is a schematic diagram showing measurement points of a bent-up sheath portion of a concrete structure measured by the measuring device of FIG. 1. [Figure 12] FIG. 1A is a cross-sectional view of a concrete structure, (B) is an example of poor PC grout filling, and (C) is an enlarged cross-sectional view showing another example of poor PC grout filling. [Figure 13] 13A and 13B show modified examples of the detection coil, in which (A) is a rectangular detection coil, and (B) and (C) are detection coils with a reduced diameter for multi-point measurement. [Figure 14] The figures show the positional relationship between the detection coil and the prestressing steel, with (A) showing the structure of a concrete structure, (B) showing the case where the detection coil is located directly above the prestressing steel, and (C) showing the case where the detection coil is 10 mm off-center from the prestressing steel. [Figure 15]The figure shows the induced electromotive force detected by the detection coil, where (A) is when the detection coil is directly above the PC steel and 10 mm off-center, and (B) is when the detection coil is moved 80 mm in the perpendicular direction A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the present invention will be described in detail based on the embodiments shown in FIG. 1 to FIG. FIG. 1 shows the configuration of one embodiment of a measuring device 10 according to the present invention. Here, a case will be described in which the measuring device 10 is used to evaluate the PC grout filling state in a post-tensioned concrete structure in which a sheath 21 and PC steel members 22 are embedded as a measurement object. Here, PC steel members 22 collectively refer to materials used in post-tensioned concrete structures such as PC steel bars and PC steel strands. As shown in FIG. 1, the measuring device 10 is composed of a housing 11, an excitation coil 12, a pulse generating unit 13, a detection coil 14, a measuring unit 15, a calculation unit 16, an evaluation unit 17, a storage unit 18, and a display unit 19.

[0015] 6(A) to (C), the housing 11 has a substantially rectangular parallelepiped outer shape and houses therein the excitation coil 12, the pulse generating unit 13, the detection coil 14, the measurement unit 15, the calculation unit 16, and the evaluation unit 17, with a display unit 19 exposed on the top surface. The housing 11 has an opening (not shown) on the bottom surface, and the excitation coil 12 and the detection coil 14 are exposed downward through this opening.

[0016] As a result, since each component is contained and integrated within a single housing 11, when performing measurements on the measurement surface 23 (see Figure 7) of the object to be measured, the simple task of positioning the housing 11 with respect to the measurement surface 23 allows each component, particularly the excitation coil 12 and detection coil 14, to be accurately positioned with respect to the measurement surface 23, improving workability and reducing work time when measurements are performed sequentially on multiple measurement points.

[0017] In order to evaluate the PC grout filling state of a concrete structure 20 having a sheath 21 and PC steel members 22 embedded therein, the bottom surface of the housing 11 is abutted against a surface (hereinafter referred to as a measurement surface) 23 adjacent to the sheath 21 of the concrete structure 20 as shown in Fig. 6(B). As a result, as shown in Fig. 6(C), the excitation coil 12 and detection coil 14 of the measurement device 10 face the measurement surface 23 adjacent to the sheath 21 of the concrete structure 20. The housing 11 may be provided with a handle 11a on its upper side as shown in Fig. 6(B) and configured as a portable type.

[0018] Here, the storage unit 18 is used as a so-called SD card 18a inserted into a slot 18c provided on the top surface of the housing 11. The storage unit 18 may be provided inside the housing 11 as a storage medium such as an HDD or SSD in addition to or instead of the SD card 18a. The storage unit 18 has measurement data 16a calculated by the calculation unit 16 described below registered therein in a readable and writable manner, and also has reference data 16b registered therein in a readable and writable manner in advance. The storage unit 18 may also have a first storage area 18a for storing reference data and a second storage area 18b for storing evaluation index values, as described below.

[0019] As shown in Figures 2(A) and (B), the excitation coil 12 includes a main body 12a extending horizontally, and magnetic pole ends 12b, 12c extending from both ends of the main body 12a to one side (the lower side in the illustrated case), and windings 12d, 12e are wound around the magnetic pole ends 12b, 12c, respectively. In the illustrated case, for example, the main body 12a has a total length of 250 mm, a height of 50 mm, and a width of 50 mm, and the height of each of the magnetic pole ends 12b, 12c is set to 50 mm. As a result, the coil dimensions are 200 x 100 x 50 mm, the coil cross section is 50 x 50 mm, and the coil magnetic path length is 300 mm. The number of turns of each of the windings 12d, 12e is, for example, 8 turns each.

[0020] Furthermore, during measurement, the end faces (called pole tip faces) 12f, 12g of the magnetic pole ends 12b, 12c of the excitation coil 12 are positioned with a predetermined distance D between them and the measurement surface 23 of the object to be measured, as shown in Figure 7(A). Preferably, a solid spacer S is placed within this gap, so that the coil is spaced apart from the measurement surface 23 of the object to be measured without contacting it.

[0021] The solid spacer S is made of, for example, a non-magnetic, non-conductive and non-elastic material, particularly a material that does not transmit the impact of the exciting coil 12, such as polyurethane foam, and when the exciting coil 12 is placed at a distance D from the measurement surface 23, the solid spacer S is compressed to press the measurement surface 23 with a constant pressure and maintain the compressed shape, absorbing the impact of the pulse current of the exciting coil 12. With this configuration, the magnetic pole end faces 12f, 12g of the exciting coil 12 are reliably spaced from the measurement surface 23, and the measurement operation is performed without contact. In particular, when the solid spacer S is present, the solid spacer S suppresses vibrations generated by the impact of the pulse current, and the measurement is performed more accurately.

[0022] The distance D by the gap or solid spacer described above is configured to be appropriately adjustable according to the distance (so-called cover) to the sheath 21 and PC steel 22 embedded in the concrete structure 20, which is the measurement target. As a result, the thickness of the gap or solid spacer S is appropriately adjusted according to various elements such as the embedded depth of the steel rod in the concrete structure 20 and the diameters of the sheath 21 and PC steel 22, allowing optimal measurement to be performed.

[0023] The pulse generating unit 13 is composed of a charging circuit 13a and a discharging circuit 13b as shown in Fig. 3. The charging circuit 13a has a known circuit configuration, and supplies power from a power source 13c, such as a commercial power source (AC 100V) or a power supply unit, via a charging control circuit 13d, a step-up transformer 13e, and a bridge-type rectifier circuit 13f, and controls the charging control circuit 13d by a voltage setting unit 13g to obtain a predetermined output voltage V.

[0024] The discharge circuit 13b is composed of a charging capacitor C connected in parallel to the exciting coil 12, the exciting coil 12, and a discharge switch circuit 13i connected in series to the exciting coil 12 and the negative side of the charging capacitor C. The charging capacitor C is made up of a plurality of capacitors, each having a predetermined withstand voltage, connected in series and parallel. The charge stored in the charging capacitor C is discharged in one go to the exciting coil 12 by turning on the discharge switch circuit 13i, and a pulse current is applied to the exciting coil 12.

[0025] Here, regarding the discharge circuit 13b of the pulse generating unit 13, in order to obtain a larger pulse current with the lowest possible charging voltage, the wiring resistance r c and the resistance r of the exciting coil 12 coil is set as small as possible, and the capacitance C of the charging capacitor is set as large as possible. In this case, the equivalent series resistance r ESR Select a capacitor with a small capacitance and connect it in parallel if necessary to ensure sufficient capacitance.

[0026] By minimizing the wiring resistance r of the discharge circuit 13b, a low charging voltage is sufficient, and by making the capacitance C of the capacitor as large as possible, a larger pulse current can be obtained, making it possible to generate a large magnetic field. In addition, since the withstand voltage of the charging capacitor C must be set higher than the supply voltage V, if this withstand voltage is insufficient, a predetermined number of capacitors may be connected in series. In other words, the withstand voltage of the charging capacitor C is the withstand voltage (V) of the capacitor having the predetermined withstand voltage multiplied by the number of stages connected in series.

[0027] Furthermore, the critical damping condition in the discharge circuit 13b is as follows: (r / 2) 2 = L / C or (r / 2) 2 <L / C It is necessary to satisfy the critical damping condition, and multiple capacitors are connected in parallel in each stage until this critical damping condition is satisfied. By satisfying the critical damping condition, an optimal pulse current can be obtained.

[0028] In Fig. 3, the charging capacitor C is made up of four capacitors C1, C2, C3, and C4 connected in parallel and in series to each other. Generally, aluminum electrolytic capacitors are used as large-capacity capacitors, but aluminum electrolytic capacitors have an electrolyte inside and mobility of ions accompanied by electric charge, which causes the problem that the equivalent series resistance is large. Therefore, the charging capacitor C uses a film capacitor, which has a smaller equivalent series resistance than the aluminum electrolytic capacitor, to reduce the equivalent series resistance and to ensure the withstand voltage by connecting in series in a specified number of stages. In the pulse generating unit 13 configured as described above, the charging capacitor C is charged by the charging circuit 13a, and then the discharge switch circuit 13i is turned on to discharge the charge all at once to the exciting coil 12, so that a pulse current such as that shown in the graph of FIG. 4 flows in the exciting coil 12.

[0029] As shown in Fig. 2(C), the detection coil 14 is composed of a surrounding conductor 14a with a predetermined number of turns and connection wires 14b, 14c drawn out from both ends of the surrounding conductor 14a, and as shown in Fig. 7, the detection coil 14 is disposed on a plane including the two magnetic pole end faces 12f, 12g of the excitation coil 12, spaced apart to one side (upper side in the illustrated case) from the axis X connecting these two magnetic pole end faces 12f, 12g. In the illustrated case, the detection coil 14 is selected to have, for example, 5 turns and a coil diameter of 20 mm.

[0030] As shown in Fig. 1, the measurement unit 15 detects the induced current i generated in the detection coil 14 and outputs it to the calculation unit 16. As shown in Fig. 5, the calculation unit 16 time-integrates the induced current i measured by the measurement unit 15 to calculate the magnetic flux density B, and also calculates an estimated electromagnetic force signal as measurement data 16a by multiplying the induced current I and the magnetic flux density B. This estimated electromagnetic force signal changes depending on whether the PC grout filling state, which will be described later, is unfilled or insufficiently filled (see Non-Patent Document 1).

[0031] The evaluation unit 17 compares the measurement data 16a calculated by the calculation unit 16 with the reference data 16b read from the first memory area 18a of the memory unit 18, and evaluates the PC grout filling state of the measurement target, that is, the concrete structure 20. Specifically, the evaluation unit 17 compares the measurement data 16a with the reference data 16b, and generates a first evaluation index value 17a from the difference between them.

[0032] The evaluation unit 17 registers this first evaluation index value 17a in a second memory area 18b of the memory unit 18, and compares it with a preset threshold value 17b to evaluate the PC grout filling state. That is, the evaluation unit 17 evaluates that the PC grout filling state is filled when the first evaluation index value 17a is equal to or smaller than the threshold value 17b, and evaluates that the PC grout filling state is unfilled or insufficiently filled when the first evaluation index value 17a exceeds the threshold value 17b, and outputs this evaluation result 17c to the display unit 19.

[0033] Furthermore, when the evaluation unit 17 performs the above-mentioned measurement and evaluation process at a plurality of measurement points along the longitudinal direction of the sheath 21 of the concrete structure 20, it generates a first evaluation index value 17a by comparing the measurement data 16a generated by the calculation unit 16 with reference data 16b for each measurement point in sequence, registers the first evaluation index value 17a in a second memory area 18b of the memory unit, and compares the first evaluation index value 17a with a preset threshold value 17b to evaluate the PC grout filling state, and outputs an evaluation result 17c together with the measurement data 16a to the display unit 19. In this case, the evaluation unit 17 evaluates the PC grout filling state as unfilled or improperly filled when the first evaluation index value 17a exceeds the threshold value 17b at two consecutive measurement points.

[0034] As a result, measurements are taken at multiple measurement points along the longitudinal direction of the sheath 21 to generate a first evaluation index value 17a, and if the first evaluation index value 17a exceeds the threshold value 17b at both adjacent measurement points, the PC grout filling state is determined to be unfilled or poorly filled, so that even if an error occurs in the measurement of the induced current by the measuring unit 15, the PC grout filling state can be more reliably evaluated as being unfilled or poorly filled.

[0035] Furthermore, the evaluation unit 17 acquires position information 17d at each measurement point and associates it with the first evaluation index value 17a, thereby outputting it to the display unit 19 as two-dimensional coordinate information 17e. As a result, the display unit 19 displays a two-dimensional graph 19a based on this two-dimensional coordinate information 17e. Then, the evaluation unit 17 generates a second evaluation index value 17f from a change in the slope of the curve of the first evaluation index value 17a in the two-dimensional coordinate information 17e when the slope of the curve becomes equal to or greater than a predetermined angle, and outputs the second evaluation index value 17f to the display unit 19.

[0036] Furthermore, when the evaluation unit 17 performs the above-mentioned measurement and evaluation processing at multiple measurement points in the region 24 (see Figure 11) of the bent-up portion of the sheath 21 of the concrete structure 20, it generates a first evaluation index value 17a by comparing the measurement data 16a created by the calculation unit 16 with reference data 16b for each measurement point sequentially from the bottom to the top of the bent-up portion and registers it in a second memory area 18b of the memory unit 18. It also evaluates the PC grout filling state based on the change in the first evaluation index value 17a and outputs the evaluation result 17c to the display unit 19 together with the measurement data 16a.

[0037] The display unit 19 is provided on the upper surface of the housing 11, and displays the measurement data 17a and evaluation results 17c output from the evaluation unit 17, as well as a two-dimensional graph 19a based on the two-dimensional coordinate information 17e, and also displays a warning that the PC grout filling status is unfilled or improperly filled based on the second evaluation index value 17f.

[0038] Next, a method of evaluating the PC grout filling state of a concrete structure 20 in which a sheath 21 and PC steel members 22 are embedded as a measurement object using the measurement device 10 according to an embodiment of the present invention will be described. As shown in Fig. 6(B), the measuring device 10 is brought into contact with the measurement surface 23 adjacent to the sheath 21 of the concrete structure 20. Since the exciting coil 12 and the detecting coil 14 are integrated within the housing 11, there is no need to position them with respect to the measurement surface 23, and further, all the necessary components are built into the measuring device 10, making it easy to perform the evaluation.

[0039] In this state, when a pulse current from the pulse generating unit 13 is applied to the exciting coil 12, a pulsed magnetic field A1 is generated in the exciting coil 12, as shown in Fig. 8(A). Therefore, due to the magnetic field from the exciting coil 12, an induced current A2 is generated in the sheath 21 and the PC steel 22, as shown in Figs. 8(A) and (B). This induced current A2 and the magnetic field A1 of the exciting coil 12 generate an electromagnetic force F in the sheath 21 and the PC steel 22.

[0040] Therefore, a difference ΔF occurs in the electromagnetic force due to the difference between the magnetic field on the exciting coil 12 side and the magnetic field on the opposite side of the sheath 21 and the PC steel 22, so that a force acts on the sheath 21 and the PC steel 22 on the opposite side of the exciting coil 12, causing the sheath 21 and the PC steel 22 to vibrate. This vibration generates an induced current flowing through the sheath 21 and the PC steel 22 as shown in FIG. 8(C), generating a new magnetic field A3. At that time, when the PC grout filling state in the sheath 21 is not filled or is imperfectly filled, the restraining force of the PC grout 22a on the sheath 21 and the PC steel 22 is weaker than when the PC grout is filled, so the vibration of the sheath 21 and the PC steel 22 becomes larger, and the generated magnetic field A3 also becomes larger. Therefore, an induced current i is generated in the detection coil 14 by this magnetic field A3.

[0041] This induced current i is measured by the measurement unit 15, and the calculation unit 16 calculates an estimated electromagnetic force signal acting on the detection coil 14 as measurement data 16a by multiplying this induced current i by the time integral of the induced current. The calculation unit 16 registers this measurement data 16a in a first storage area 18a of the storage unit 18. Thereafter, the evaluation unit 17 compares this measurement data 16a with reference data 16b registered in advance in the first storage area 18a of the storage unit 18, and generates a first evaluation index value 17a from the difference therebetween.

[0042] The evaluation unit 17 evaluates the PC grout filling state by comparing the first evaluation index value 17a with a threshold value 17b read out from a second memory area 18b of the memory unit 18. That is, the evaluation unit 17 evaluates that the PC grout filling state is filled when the first evaluation index value 17a is equal to or smaller than the threshold value 17b, and evaluates that the PC grout filling state is unfilled or insufficiently filled when the first evaluation index value 17a exceeds the threshold value 17b. The evaluation unit 17 outputs this evaluation result 17c to the display unit 19.

[0043] In this way, when the evaluation of the PC grout filling state at one measurement point is completed, the measurement device 10 is moved sequentially to a plurality of measurement points, and the above-mentioned evaluation of the PC grout filling state is repeated at each measurement point. Then, the measurement data 16a and the first evaluation index value 17a are created for each measurement point, the first evaluation index value 17a is compared with the threshold value 17b to create an evaluation result 17c, and the measurement data 16a and the evaluation result 17c are output to the display unit 19. As a result, the display unit 19 sequentially displays the measurement data 16a and the evaluation result 17c for each measurement point. Therefore, by moving the measurement device 10 for each measurement point, the operator can visually confirm the measurement data 16a and the evaluation result 17c at the measurement point as a primary evaluation each time. Note that the evaluation unit 17 may evaluate the PC grout filling state as unfilled or improperly filled when the first evaluation index value 17a exceeds the threshold value 17b at two consecutive measurement points.

[0044] According to the measuring device 10, for a measurement target, for example, a post-tensioned concrete structure 20 with a sheath 21 and PC steel 22 embedded therein, a surface close to the PC steel 22 inserted into the sheath 21 and filled with PC grout 22a is set as a measurement surface 23, and a pulse current is generated by the pulse generating unit 13 and applied to the excitation coil 12 with the two pole end faces 12f, 12g of the excitation coil 12 facing the measurement surface 23. As a result, the excitation coil 12 is excited by the pulse current, and an impact is applied to the sheath 21 and PC steel 22 of the concrete structure 20. This impact generates an induced current in the detection coil 14 in response to an electromagnetic field, and this induced current is measured by the measuring unit 15, and the calculation unit 16 calculates measurement data 16a based on this induced current. The evaluation unit 17 compares the measurement data 16a with reference data 16b registered in the memory unit 18 to evaluate the PC grout filling condition within the sheath 21 of the concrete structure 20, and the display unit 19 displays the evaluation result 17c and the measurement data 16a.

[0045] This allows the PC grout filling state in the sheath 21 to be easily evaluated in a post-tensioned concrete structure 20 in which the sheath 21 and PC steel 22 are embedded. Also, even in cases such as when the sheath diameter is small compared to the sheath embedment depth, the PC grout filling state in the sheath 21 can be reliably evaluated. Furthermore, since only the vibration of the PC steel 22 needs to be detected by the induced current generated in the detection coil 14, the number of parts is reduced, and the processing content and processing time are shortened, making it possible to more efficiently evaluate the PC grout filling state.

[0046] FIG. 9(A) shows the relationship between the position of each measurement point (the distance from the end of the PC steel 22 in the concrete structure 20) and the measurement data 16a. When there is a portion B where the PC grout is not filled or is insufficiently filled on the end side of the PC steel 22 (left side in FIG. 9(A)), it can be seen that the measurement data 16a is suddenly larger than when the PC grout is filled (see FIG. 9(B)). Therefore, by creating the measurement data 16a when the PC grout is filled as a standard value in advance and registering it in the storage unit 18 as the reference data 16b, it is possible to compare the measurement data 16a at each measurement point with the reference data 16b to evaluate the PC grout filling state at that measurement point.

[0047] Here, the difference between the measurement data 16a and the reference data 16b is taken as a first evaluation index value 17a, and when the first evaluation index value 17a exceeds a threshold value 17b, the difference between the measurement data 16a and the reference data 16b is taken to be outside the allowable range of standard values, and the PC grout filling state is evaluated as unfilled or poorly filled. In this way, evaluation at each measurement point is performed immediately at the time of measurement, and is displayed on the display unit 19. According to this configuration, by comparing the difference between the measurement data 16a and the reference data 16b at one measurement point with the threshold value 17b, the PC grout filling state at that measurement point can be evaluated as filled, poorly filled, or unfilled. Furthermore, the first evaluation index value 17a as the measurement data 16a and the evaluation result 17c are displayed on the display unit 19 each time a measurement is performed at each measurement point.

[0048] For example, as shown in FIG. 10(A), when the measurement is performed by the measuring device 10, the bottom surface of the housing 11 changes in distance d from the sheath 21 of the concrete structure 20, and as shown in FIG. 10(B), the induced current and magnetic flux density detected by the detection coil 14 change. In response to this change, the change in the measurement data 16a at each measurement point is compared with the threshold value 17b as the difference from the reference data 16b, that is, the first evaluation index value 17a, to reliably evaluate the PC grout filling state. According to this method, by adopting the measurement data 16a at the measurement point where the PC grout filling state is known in advance as the reference data 16b, it is possible to perform a more accurate evaluation of the PC grout filling state. As a result, even if the sheath diameter is small compared to the sheath burial depth, for example, the first evaluation index value 17a is compared with the threshold value 17b to perform the evaluation, and the PC grout filling state can be reliably evaluated.

[0049] Furthermore, when the evaluation unit 17 measures the above-mentioned measurement data 16a at each of a plurality of measurement points along the longitudinal direction of the sheath 21 of the concrete structure 20 to be evaluated, it acquires position information 17d of the measurement points, creates two-dimensional coordinate information 17e consisting of the measurement data 16a or the first evaluation index value 17a and the position information 17d, and after measurements at all measurement points are completed, sends the two-dimensional coordinate information 17e for all measurement points to the display unit 19. In this case, it is possible to perform an evaluation of the PC grout filling state at all measurement points, that is, a secondary evaluation that overlooks the entire PC steel member 22.

[0050] According to the above method, measurements are taken at a plurality of measurement points, and position information 17d is added to the measurement data 16a to generate two-dimensional coordinate information 17e. With respect to the measurement data 16a at a plurality of measurement points, the change in the measurement data 16a is grasped as a distribution of the first evaluation index value along the longitudinal direction of the sheath in an integrated manner, and a second evaluation index value 17f is generated from the distribution of the first evaluation index value to evaluate the PC grout filling state, i.e., to be filled, insufficiently filled, or not filled. In other words, the extent of filling or not filled of the PC grout can be evaluated based on the second evaluation index value. Furthermore, if the distribution of the first evaluation index value is a curve, the second evaluation index value 17f may be generated from the change in the slope of this curve. As a result, the display unit 19 displays a two-dimensional graph 19a, for example, showing the measurement position on the horizontal axis and the measurement data 16a or the first evaluation index value 17a on the vertical axis, based on the two-dimensional coordinate information 17e. Therefore, by visually checking the two-dimensional graph 19a displayed on the display unit 19 of the measurement device 10, the operator can instantly visually grasp the PC grout filling state.

[0051] In this case, the evaluation unit 17 generates a second evaluation index value 17f from the distribution of the first evaluation index values ​​or the change in the slope of the curve of the first evaluation index values ​​17a in the two-dimensional coordinate information 17e when the slope of this curve becomes a predetermined angle or more, and outputs it to the display unit 19. In response to this, the display unit 19 displays a warning that the PC grout filling state has become unfilled or insufficient based on the second evaluation index value 17f. This allows the worker to visually recognize the warning display on the display unit 19 and understand that the PC grout filling state has become unfilled or insufficient.

[0052] Fig. 11 shows measurement work in a region 24 of a bent-up portion of a sheath 21 and a PC steel member 22 in a concrete structure 20. It is known that in the bent-up portion region 24, non-filling or insufficient filling of PC grout is more likely to occur in an upper portion 24b (right side in Fig. 11) than in a lower portion 24a (left side in Fig. 11) due to a phenomenon such as forward flow when filling the PC grout, so measurement and evaluation are performed at measurement points in sequence starting from the lower portion 24a side, as shown by arrow Y in Fig. 11.

[0053] That is, the evaluation unit 17 measures and evaluates each of multiple measurement points in the bent-up region 24 of the concrete structure 20, sequentially from the bottom 24a to the top 24b, and generates a first evaluation index value 17a at each measurement point. When the first evaluation index value 17a is equal to or less than the threshold value 17b, the PC grout filling state is evaluated as being filled, and when the first evaluation index value 17a exceeds the threshold value 17b, the PC grout filling state is evaluated as being unfilled or improperly filled, and the evaluation result 17c is output to the display unit 19. In response to this, the display unit 19 displays the measurement data 16a and the evaluation result 17c at each measurement point.

[0054] Here, the evaluation unit 17 may evaluate the PC grout filling state as unfilled or poorly filled when the first evaluation index value 17a exceeds the threshold value 17b at two consecutive measurement points. This avoids the PC grout filling state from being erroneously evaluated as unfilled or poorly filled due to measurement errors caused by noise or the like. By focusing on the fact that the PC grout filling state is more likely to become unfilled or poorly filled at the upper side in the region 24 of the bent-up portion of the PC steel 22, it is possible to more reliably evaluate the portion where the PC grout filling state changes from filled to poorly filled or unfilled by performing measurements sequentially from the bottom to the top.

[0055] (Modification of detection coil) Next, modified examples of the detector coil will be described. Fig. 13 shows modified examples of the detector coil 14, in which (A) is a rectangular detector coil 14A, and (B) and (C) are detector coils 14B and 14C whose diameters are reduced for multipoint measurement. 2(C), the detection coil 14A shown in FIG. 13(A) has a rectangular coil shape, for example, 2 cm in short side and 4 cm in long side, expanded in a direction perpendicular to the longitudinal direction of the PC steel 22 in the concrete structure 20 shown by the dotted line (position of the PC steel). The detection coil 14A may be a coil wound a predetermined number of times in a rectangular coil shape. The detection coil 14A can measure the magnetic field averaged in the direction perpendicular to the longitudinal direction of the PC steel 22 even if an error occurs between the position of the PC steel 22 and the position of the detection coil 14A. The detection coil 14A may be integrated with the excitation coil 12 so that the positional relationship with the excitation coil 12 does not change.

[0056] 2(C), the detector coil 14B shown in Fig. 13(B) has a small diameter (10 mm) in the direction perpendicular to the longitudinal direction of the PC steel 22 in the concrete structure 20, and has a configuration in which multiple detector coils, four in the illustrated case, 14B1-14B4, are arranged in two rows at different positions in the longitudinal direction of the PC steel 22. The detector coil 14B may be fixed with resin. The induced electromotive forces detected by each of these detector coils 14B1-14B4 are compared to detect the detector coil 14B with the largest induced electromotive force, and an estimated electromagnetic force signal acting on the detector coil 14B, that is, measurement data 16a, can be obtained. With the detector coil 14B, even if an error occurs between the position of the PC steel 22 and the position of the detector coil 14B, by arranging multiple detector coils 14B1-14B4 perpendicular to the longitudinal direction of the PC steel 22, it is possible to easily select the detector coil 14B with the largest induced electromotive force, that is, the largest magnetic flux, by measuring the magnetic flux at multiple points in a narrow range. The detector coil 14B may be integrated with the excitation coil 12 so that the positional relationship with the excitation coil 12 does not change.

[0057] The detector coil 14C shown in FIG. 13(C) is different from the detector coil 14B shown in FIG. 13(B) in that four detector coils 14C1-14C with small diameters are arranged in a row in a direction perpendicular to the longitudinal direction of the PC steel member 22 in the concrete structure 20. The detector coil 14C may be fixed with resin. As with the detector coil 14B, the detector coil 14C compares the induced electromotive forces detected by the detector coils 14C1-14C and detects the detector coil 14B with the largest induced electromotive force, thereby measuring the magnetic flux at multiple points in a narrow range, and thus the detector coil 14C with the largest induced electromotive force, that is, the largest magnetic flux, can be selected. The detector coil 14C may be integrated with the excitation coil 12 so that the positional relationship with the excitation coil 12 does not change. Specific examples will be described below.

[0058] (Example) A test specimen was prepared simulating a post-tensioned concrete structure 20 in which a sheath 21 and PC steel members 22 were embedded. The core cover depth of the PC steel members 22 was set to 163 mm. The excitation coil 12 shown in Figures 2(A) and (B) was connected to the discharge circuit explained in Figure 3, and the excitation coil 12 and detection coil 14 (see Figure 2(C)) were placed on the test piece, after which a voltage of 900 V was supplied to the excitation coil 12 via a bridge-type rectifier circuit 13f, and a pulse wave shown in Figure 4 was applied. After the application of the pulse wave, the induced electromotive force due to the induced current generated in the detection coil 14 was measured.

[0059] Figure 14 shows the positional relationship between the detection coil 14 and the prestressing steel 22, with (A) showing the structure of the concrete structure 20, (B) showing the case where the detection coil 14 is located directly above the prestressing steel 22, and (C) showing the case where the detection coil 14 is 10 mm off-center from the prestressing steel 22. The distance between the excitation coil 12 and the detection coil 14 was 40 mm. As shown in Figure 14, the detection coil 14 was moved in 10 mm increments from directly above the prestressing steel 22 in direction A perpendicular to the longitudinal direction over a distance of 80 mm from -10 mm directly above to 70 mm, measuring at nine points.

[0060] Figure 15 is a graph showing the induced electromotive force detected by the detection coil 14, where (A) shows the case where the detection coil 14 is directly above the PC steel 22 and 10 mm off-center, and (B) shows the case where the detection coil 14 is moved 80 mm in the perpendicular direction A. In Fig. 15(A), the horizontal axis is time (sec) and the vertical axis is the induced electromotive force (V) of detection coil 14. In Fig. 15(B), the horizontal axis is the distance (mm) between prestressing steel 22 and detection coil 14, and the vertical axis is the induced electromotive force (V) of detection coil 14. Note that the induced electromotive forces at each distance shown in Fig. 15(B) are plots of the maximum values ​​generated on the positive and negative sides of the induced electromotive force as shown in the waveform in Fig. 15(A). From Figs. 15(A) and (B), it was found that when detection coil 14 is located directly above prestressing steel 22, an induced electromotive force that is approximately twice as large as when detection coil 14 is off-centered by 10 mm in the perpendicular direction A can be obtained.

[0061] The present invention can be embodied in various forms without departing from the spirit of the invention. For example, in the above-described embodiment, the measurement points are set at regular intervals along the longitudinal direction of the sheath 21, but the present invention is not limited thereto. For example, additional measurement points may be set at shorter intervals between a measurement point where the PC grout filling state is evaluated as unfilled or imperfectly filled and the measurement points before and after the measurement point, and the PC grout filling state may be evaluated for each additional measurement point, thereby making it possible to more accurately identify the position where the PC grout filling state changes from filled to unfilled or imperfectly filled. This makes it possible to more accurately detect the boundary position where the PC grout filling state changes from filled to imperfectly filled or unfilled in the longitudinal direction of the PC steel 22 by shortening the measurement point interval between a measurement point where the PC grout filling state is evaluated as unfilled or imperfectly filled and the measurement points before and after the measurement point which are evaluated as filled. [Explanation of symbols]

[0062] 10. Measurement Equipment 11. Cabinet 11a Handle 12 Excitation coil 12f,12g pole end face 13 Pulse generator 13a charging circuit 13b Discharge circuit 13c power supply 13d Charging control circuit 13e Step-up transformer 13f Bridge type rectifier circuit 13g Voltage setting section 14, 14A, 14B, 14C Detection coil 14a Circuit Wire 14b, 14c Connection wiring 15. Measurement section 16 Arithmetic section 16a Measurement data 16b Reference Data 17 Evaluation Section 17a First evaluation index value 17b Threshold 17c Evaluation Results 17d Location information 17e Two-dimensional coordinate information 17f Second evaluation index value 18 Storage section 19 Display section 19a Two-dimensional graphs 20 Concrete Structures 21 Sheath 22 PC steel material 22a PC Grout 23 Measurement Surface 24 Bend-up area S Solid Spacer

Claims

1. an excitation coil arranged such that two magnetic pole end faces having mutually different polarities in an excited state face a measurement surface of an object to be measured; a pulse generating unit which applies a pulse current to the excitation coil; a detection coil arranged on a plane including the two magnetic pole end faces of the excitation coil and spaced apart from an axis connecting the two magnetic pole end faces; a measurement unit which measures an induced current generated in the detection coil; a calculation unit which calculates an estimated electromagnetic force signal as measurement data by the product of the induced current measured by the measurement unit and a time integral of the induced current; a memory unit which registers the measurement data and in which reference data is registered in advance; an evaluation unit which compares the measurement data with reference data read out from the memory unit to evaluate a state of the object to be measured; and a display unit which displays the evaluation result by the evaluation unit and the measurement data; A measuring device characterized in that: the wiring resistance r of the discharge circuit and the capacitance C of the capacitor are selected so that the discharge circuit satisfies a critical damping condition; the excitation coil and the detection coil are integrated so that their positional relationship does not change; the detection coil is composed of a surrounding conductor and a detection surface defined by the surrounding conductor is arranged parallel to the measurement surface; the magnetic pole tip surface of the excitation coil is arranged with a predetermined gap from the measurement surface or is separated from the measurement surface via a non-magnetic, non-conductive solid spacer of a predetermined thickness; and the gap or the thickness of the solid spacer is configured to be adjustable with respect to the measurement surface.

2. 2. The measuring device according to claim 1, wherein the excitation coil, the detection coil, the pulse generating unit, the measurement unit, the calculation unit, the memory unit and the evaluation unit are housed within a single housing, and the display unit is provided on a surface of the housing.

3. The measuring device of claim 1 or 2, wherein the solid spacer is inelastic.

4. 4. A measuring device as described in any one of claims 1 to 3, characterized in that the detection coil has a coil shape that expands in a direction perpendicular to the longitudinal direction of the PC steel of a post-tensioned concrete structure in which PC steel is embedded in a sheath as the measurement object and filled with grout material.

5. 5. The measuring device according to claim 1, wherein the detection coil is composed of a plurality of coils arranged perpendicular to the longitudinal direction of the PC steel of a post-tensioned concrete structure in which the PC steel is embedded in a sheath as the measurement object and filled with grout material.

6. 6. A method for evaluating a PC grout filling state in a concrete structure, comprising: a first step of applying a pulse current to the excitation coil by the pulse generating unit with both magnetic pole end faces of the excitation coil facing each other in the longitudinal direction of the sheath with respect to a measurement surface adjacent to a sheath of a post-tensioned concrete structure in which PC steel is embedded in a sheath as the measurement object and grout material is filled in the sheath, thereby impacting the concrete structure; a second step of measuring an induced current generated in the detection coil in response to the electromagnetic field due to the impact by the measurement unit and calculating measurement data by the calculation unit; a third step of comparing the measurement data with the reference data by the evaluation unit to evaluate the PC grout filling state in the sheath of the concrete structure; and a fourth step of displaying the evaluation result on the display unit.

7. The evaluation method according to claim 6, characterized in that the reference data is measurement data at a measurement point where it is known in advance that PC grout is filled, and the evaluation unit compares the measurement data with the reference data to evaluate the PC grout filling state within the sheath of the concrete structure that is the measurement object.

8. The evaluation method according to claim 7, characterized in that the evaluation unit evaluates the PC grout filling state as filled, poorly filled, or unfilled by comparing the difference between the measurement data and the reference data as a first evaluation index value and a preset threshold value.

9. The evaluation method according to claim 8, characterized in that for the concrete structure, a pulse current is applied to the excitation coil, an induced current generated in the detection coil is measured and the measurement data is calculated at a plurality of measurement points along the longitudinal direction of the sheath, the evaluation unit creates two-dimensional coordinate information consisting of the measurement data at each measurement point and position information of the measurement point, the evaluation unit generates a second evaluation index value from the two-dimensional coordinates and a distribution of the first evaluation index value, and evaluates the area filled or unfilled with PC grout based on the second evaluation index value.

10. The evaluation method according to claim 9, characterized in that the evaluation unit causes a display unit to display the first evaluation index value and the evaluation result of the PC grout filling state for each measurement point.

11. The evaluation method according to claim 8, characterized in that for the concrete structure, a pulse current is applied to the excitation coil, an induced current generated in the detection coil is measured, and the measurement data is calculated at a plurality of measurement points along the longitudinal direction of the sheath, and the evaluation unit sequentially generates a first evaluation index value for each measurement point, and if the first evaluation index value continuously exceeds a threshold value, the PC grout filling state is evaluated as unfilled or improperly filled.

12. The evaluation method according to claim 9 or 10, characterized in that for the multiple measurement points, in the region of the bent-up portion of the sheath, a pulse current is applied to the excitation coil, an induced current generated in the detection coil is measured and the measurement data is calculated, and a first evaluation index value is generated, in sequence from bottom to top; and the evaluation unit compares the first evaluation index value at each measurement point with the threshold value in sequence, and if the first evaluation index value continuously exceeds the threshold value, evaluates the PC grout filling state as unfilled or poorly filled.

13. The evaluation method according to claim 11 or 12, characterized in that, for the plurality of measurement points, a short interval is selected between a measurement point whose PC grout filling state is evaluated as unfilled or poorly filled and a measurement point before and after that whose PC grout filling state is evaluated as filled.

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