JP3917359B2 - Nondestructive compression test method and nondestructive compression test equipment for concrete - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nondestructive compression test method and a nondestructive compression test apparatus for concrete, which are suitable for testing the compressive strength of concrete formations (for example, existing concrete structures, concrete products such as piles and fume pipes). .
[0002]
[Prior art]
Methods for testing the compressive strength of concrete structures include the following.
(1) A test piece is prepared at the time of placing concrete, and a compression test is performed on the test piece at a predetermined time using a compression tester.
(2) A part of a place to be examined such as a pillar, a beam, and a wall is sampled by core boring or the like, and the sampled sample is tested by a compression tester.
(3) Perform a nondestructive compression test by the surface hardness method (Schmidt Hammer).
[0003]
[Problems to be solved by the invention]
However, the methods {circle around (1)}, {circle around (2)} and {circle around (3)} have the following disadvantages.
In the case of {circle around (1)}, there are inconveniences such as troublesome management in preparation, curing, storage, etc. of the test piece, and a compatibility problem that the strength of the actual structure is indirectly estimated from the strength of the test piece.
In the case of (2): a defect occurs because a part of the structural frame is collected, and further, a large-scale work is required for this collection.
In the case of (3): Since concrete is hit and tested locally, it is easily affected by variations in surface hardness, resulting in relatively large variations in test results and lack of reliability.
[0004]
Therefore, in view of the above circumstances, the present invention has no problem of management complexity and compatibility, and does not damage the structure due to member loss, and can obtain a highly reliable test result. An object is to provide a nondestructive compression test method and a nondestructive compression test apparatus.
[0005]
[Means for Solving the Problems]
Claim 1 of the present invention for solving the above-mentioned problems is that the compressive strength (fc) of the concrete (40) is reduced without destroying the concrete (40) based on vibration propagated to the concrete surface (20). In the nondestructive compression test apparatus (1) that can be obtained,
A plurality of vibration detection means (3) for detecting vibrations propagated through the concrete (40);
The plurality of vibration detection means (3) are supported so that the plurality of vibration detection means (3) are brought into contact with positions (Q1, Q2) spaced apart from each other on the surface (20) of the concrete, and the concrete (40 ) A frame (2) composed of a material having a lower elastic wave velocity;
A detection result output unit (7) for outputting detection results of the plurality of vibration detection means (3);
A time difference detection unit (14) for detecting a time difference (T) between detection of vibration by one vibration detection means (3) and detection of the vibration by another vibration detection means (3);
Propagation for calculating the propagation velocity (V) of the vibration based on the detected time difference (T) and the distance (L) between the one vibration detection means (3) and the other vibration detection means (3). A speed calculator (12);
And a compressive strength calculating section (13) for calculating the compressive strength (fc) of the concrete based on the propagation velocity (V) .
[0006]
According to a second aspect of the present invention, in the nondestructive compression test apparatus , the vibration detecting means (3) includes a horizontal sensor (3b) for measuring elastic waves and / or a vertical sensor for measuring shear elastic waves ( 3a)
The compressive strength calculating unit (13) calculates the compressive strength (fc) of concrete based on the propagation velocity (Ve, Vs) of the elastic wave and / or the shear elastic wave.
[0007]
According to a third aspect of the present invention, in the nondestructive compression test apparatus (1), the vibration detecting means (3) has a rotatable sensor, and an elastic wave or a shear elastic wave according to the rotational position. Is measured.
[0010]
Note that the numbers in parentheses are for the sake of convenience indicating the corresponding elements in the drawings, and therefore the present description is not limited to the descriptions on the drawings.
[0011]
【The invention's effect】
As described above, according to the first and second aspects of the present invention, since the test piece is not used, there is no management complexity and compatibility problem. Further, since a part of the concrete casing to be tested is not collected, the structural casing is not damaged and a large-scale work is unnecessary. In addition, since the propagation speed of vibration across the two detection points is obtained, it is not easily affected by variations in the surface hardness of the concrete, the test results do not vary, and the reliability is high. Further, it is convenient to perform a test easily because it is sufficient to hit the ball at an arbitrary point in the vicinity of the extension line connecting the two detection points.
[0013]
According to the third aspect of the present invention, the same effect as that obtained when both the horizontal sensor and the vertical sensor are provided can be obtained, and the vibration detecting means can be easily and compactly formed by using the sensor.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic diagram showing a state in which a nondestructive compression test of concrete is performed by a nondestructive compression test apparatus. As shown in FIG. 1, the nondestructive compression test apparatus 1 includes an instrument 4 and a control device 10. The instrument 4 has a rod-like frame 2, and the frame 2 is made of a material having a lower elastic wave velocity than concrete so as not to affect the test result.
[0017]
Vibrometers 3 are respectively provided in the vicinity of both ends of the frame 2, and a gap is formed between the vibrometers 3, 3, and has a U-shape as a whole. In the vicinity of the center of the frame 2, a handle portion 2a that can be held and carried by a tester is formed. The frame 2 is provided with an interface portion 7 such as a connector electrically connected to the vibration meters 3 and 3, and a cable 5 is detachably connected to the interface portion 7. The side of the cable 5 opposite to the appliance 4 is connected to the control device 10.
[0018]
FIG. 2 is a block diagram showing a control configuration of the nondestructive compression test apparatus. As shown in FIG. 2, each vibrometer 3 has a horizontal sensor 3b, and a cable 5 is connected to the horizontal sensor 3b via an interface unit 7 omitted in FIG. As shown in FIG. 1, each vibration meter 3 is provided with a detection unit 3t (probe or the like) for the horizontal sensor 3b to capture vibration, and between the two detection units 3t and 3t of the three vibration meters 3 and 3. The interval is a predetermined interval L.
[0019]
As shown in FIG. 2, a main control unit 11 is provided on the control device 10 side. The main control unit 11 is connected to the cable described above via a filter / amplifier 6 and an A / D converter (not shown). 5 is connected. The horizontal sensor 3b described above captures the vibration, and the detection signal S1 or S2 is transmitted through the cable 5, and the vibration of the target frequency band is extracted and amplified by the filter / amplifier 6. The main control unit 11 is provided with a time difference detection unit 14, a speed calculation unit 12, a compression strength calculation unit 13, a display output unit 15, a recording unit 16 and the like via an internal bus. In FIG. 1, the instrument 4 and the control device 10 are separated from each other. However, the function of the control device 10 can be built in the frame 2 of the instrument 4 to provide portability and portability.
[0020]
FIG. 3 is a schematic cross-sectional view showing an example of a coarse / fine wave generator. For example, as shown in FIG. 3, a coarse / fine wave generator 30 used when performing a nondestructive compression test described later using the above-described nondestructive compression test apparatus 1 is installed on a concrete surface 20 constituting a flat slab or the like. A flexible frame 31 is provided, and a cylinder 32 arranged horizontally (parallel to the concrete surface 20) is fixed to the frame 31. A piston-like weight 33 that can reciprocate within the cylinder 32 is installed in the cylinder 32, and a spring 35 is provided on one of the weights 33.
[0021]
In order to use the coarse / fine wave generator 30, first, as shown by the solid line display in FIG. 3, the weight 33 is arranged at the first position PS <b> 1 by compressing the spring 35. The weight 33 is fixed to the cylinder 32 via the pin 36 at the first position PS1. Then, when generating a dense wave in concrete, the pin 36 is pulled out. As a result, the compression of the spring 35 is released, and the weight 33 moves violently in the cylinder 32 to the second position PS2 (indicated by a two-dot chain line) and hits the wall 32a of the cylinder 32. The impact hitting the wall portion 32a is transmitted to the concrete 40 through the frame 31, and a close-packed wave (elastic wave) is generated in the vicinity of the concrete surface 20.
[0022]
Since the nondestructive compression test apparatus 1 and the like are configured as described above, the nondestructive compression test of concrete is performed as follows using the nondestructive compression test apparatus 1. First, as shown in FIG. 1, the instrument 4 (frame 2) of the nondestructive compression test apparatus 1 is installed on the concrete 40 to be tested (in the figure, an example of a horizontal concrete slab is shown). At the time of installation, the detectors 3t and 3t of the two vibrometers 3 and 3 are arranged so as to contact the concrete surface 20. The points where each detection unit 3t contacts the concrete surface 20 are set as detection points Q1 and Q2, respectively.
[0023]
Subsequently, the above-mentioned rough / undense wave generator 30 is installed at a point P (FIG. 1) in the vicinity of the extension line connecting the two detection units 3t and 3t. Thus, the detection points Q1, Q2 and the point P are arranged in series. After the installation, the coarse / fine wave generator 30 generates a coarse / fine wave (elastic wave) in the concrete 40 according to the procedure already described. If the concrete to be tested is a member with exposed side surfaces such as beams and columns, the same density wave can be generated by hitting the side surface with a hammer or the like without using the density wave generator 30. be able to. Further, the above-described coarse / fine wave generator 30 shown in the present embodiment is merely an example, and the coarse / fine wave may be generated by other devices or methods.
[0024]
Each vibrometer 3 of the nondestructive compression test apparatus 1 detects the elastic wave with a time difference corresponding to the interval L via the detector 3t. Detection signals S 1 and S 2 from the vibrometers 3 and 3 are sequentially transmitted to the control device 10 side by the cable 5 through the interface unit 7. In the control device 10, the detection signals S1, S2 are A / D converted by an A / D converter (not shown), and the time difference detection unit 14 calculates the rise time difference T of the A / D converted detection signals S1, S2. This is transmitted to the speed calculation unit 12. Various methods other than this can be used for detecting the time difference T. For example, the timer may be started when the first detection signal is received, the next detection signal is received, the timer is stopped, and the time measured by the timer may be detected as a time difference.
[0025]
The speed calculation unit 12 calculates the velocity V of the elastic wave generated in the concrete based on the transmitted time difference T. That is, the time difference T is equal to the time during which the elastic wave travels through the interval L between the detectors 3t and 3t, and therefore the velocity V of the elastic wave is obtained by dividing the interval L by the time difference T. The speed calculation unit 12 transmits the calculated speed V to the compression strength calculation unit 13.
[0026]
FIG. 5 is a diagram showing waveform data detected in each vibration meter. For example, when the interval L is 30 cm, the waveform data at the two vibrometers 3 and 3 is DAT1. Vibrometers 3 and 3 detect rising points A and A ′ of the waveform of FIG. DAT2 and DAT3 are examples when the distance L is 50 cm and 100 cm, respectively. In DAT2, vibrometers 3 and 3 detect waveform rising points B and B ', respectively. In DAT3, vibrometers 3 and 3 The rising points C and C ′ are detected respectively.
[0027]
FIG. 4 is a diagram showing the relationship between the elastic wave velocity and the compressive strength of concrete. The compressive strength calculating unit 13 calculates the compressive strength by substituting the transmitted velocity V of the elastic wave into the relational expression between the elastic wave velocity and the compressive strength statistically obtained from the experiment. Generally, for each type of concrete, the relationship between the strength of the concrete (N / mm ² ) and the elastic wave velocity (m / s) propagating through the concrete is determined. For example, for the concrete to be tested in this embodiment, as shown in FIG. 4, the experimental statistical formula of concrete strength fc and elastic wave velocity; fc = Φ (V) is obtained in advance based on experiments, and the compressive strength calculating unit 13 Holds the experimental statistical formula; fc = Φ (V). Therefore, the compressive strength calculation unit 13 obtains the compressive strength fc of the concrete by substituting the speed V into the experimental statistical formula; fc = Φ (V).
[0028]
The compression strength fc calculated by the compression strength calculation unit 13 is transmitted to the display output unit 15, and the display output unit 15 displays the compression strength fc via a display (not shown). Further, the compression strength fc is transmitted to the recording unit 16, and recording is performed by a magnetic disk, a printer, or the like controlled by the recording unit 16.
[0029]
As described above, in the present embodiment, since no test piece is used, there are no management complexity and compatibility problems. Further, since a part of the structural casing to be tested is not collected, the structural casing is not damaged, and a large-scale work is unnecessary. Further, since the velocity of the elastic wave in the concrete between the two vibrometers 3 and 3 is obtained, it is not easily affected by the variation in the surface hardness of the concrete, the test result does not vary, and the reliability is high.
[0030]
In addition, it is convenient that the test can be easily performed because it is sufficient to strike at an arbitrary point P in the vicinity of the extension line connecting the two vibrometers 3 and 3.
[0031]
In the embodiment described above, the vibration generated in the concrete is tested as a vibration due to a dense wave (elastic wave). However, the vibration can be tested as a shear elastic wave. In this case, as shown in FIG. 2, the vibration meter 3 is provided with a vertical sensor 3a. The compressive strength calculation unit 13 holds experimental statistical formulas related to shear elastic waves.
[0032]
That is, as shown in FIG. 1, the instrument 4 is installed, and a point P near the extension line connecting the two detection units 3t and 3t is hit almost perpendicularly on the concrete surface 20 with a hammer or the like. As a result, the concrete is vibrated by shear elastic waves. Thereafter, similarly to the above-described procedure, the detection signals S1 and S2 from the vibrometers 3 and 3 are sequentially transmitted to the control device 10, and the time difference detection unit 14 detects the time difference T based on the detection signals S1 and S2. The velocity calculation unit 12 calculates the shear elastic wave velocity V based on the time difference T, and the compression strength calculation unit 13 calculates the shear elastic wave velocity V statistically from the shear elastic wave velocity and the compression strength obtained from experiments. The compression strength is calculated by substituting into the relational expression, and the calculated compression strength is displayed on the display via the display output unit 15 or the compression strength is recorded on the magnetic disk or printer via the recording unit 16.
[0033]
Note that G = E / {2 (1 + ν)} holds in the relationship between the elastic modulus and the shear elastic modulus. On the other hand, the elastic wave velocity and the shear elastic wave velocity have a relationship of elastic wave velocity Ve = (E / ρ) ^1/2 and shear elastic wave velocity Vs = (G / ρ) ^1/2 depending on the elastic modulus and unit volume mass. There is. Therefore, G = (Vs / Ve) ² · E. By these equations, mutual conversion between elastic wave velocity and shear elastic wave velocity can be made by calculation. Accordingly, the compressive strength calculating unit 13 holds the experimental statistical formulas of the concrete strength and the elastic wave velocity, and the compressive strength calculating unit 13 uses the experimental statistical formula, the conversion formula, and the shear elastic wave velocity, You may make it calculate the compressive strength of concrete. Conversely, the compressive strength calculating unit 13 holds experimental statistical formulas of concrete strength and shear elastic wave velocity, and the compressive strength calculating unit 13 determines the experimental statistical formula, the conversion formula, the elastic wave velocity, Thus, the compressive strength of the concrete may be calculated.
[0034]
Further, each vibrometer 3 may have both of these sensors 3a and 3b in addition to the configuration having only one of the horizontal sensor 3b and the vertical sensor 3a. Having both the horizontal sensor 3b and the vertical sensor 3a is convenient because an elastic wave or a shear elastic wave can be selectively employed according to the test situation.
[0035]
Each vibrometer 3 may have only one sensor, and the direction of the sensor may be freely rotatable. For example, when an elastic wave is employed, the sensor is rotated and set in the same detection direction as the horizontal sensor 3b described above. When a shear elastic wave is employed, the sensor is rotated and set in the same detection direction as the vertical sensor 3a described above. By making the direction of the sensor rotatable in this way, the same effect as when both the horizontal sensor 3b and the vertical sensor 3a are provided can be obtained, and the vibrometer can be easily and compactly formed by sharing the sensor.
[0036]
Further, when the rotary sensor is employed, the vibration direction can be checked and the relational expression can be automatically applied if the rotation of the sensor is taken into the control device 10 using an electrical contact.
[0037]
In addition, since it is only necessary to measure the propagation speed of vibration (elastic wave or shear elastic wave) propagating through the interval L in concrete, for example, by directly striking one vibration meter against the concrete surface 20, the same result as the above-described embodiment can be obtained. Obtainable.
[0038]
FIG. 6 is a diagram showing a state in which a nondestructive compression test apparatus is installed on the concrete on which the finishing material is installed. As shown in FIG. 6, a test method in the case where the finishing surface 25 such as mortar is provided on the concrete surface 20 includes a hole 3 having a diameter of about 1 cm penetrating the finishing material 25 portion, and the sensor 3a with the probe 27 is provided. By making contact with the concrete surface 20 through the holes 26, damage to the finish 25 can be minimized.
[0039]
In the nondestructive compression test, two vibrometers are provided. However, the number of vibrometers may be three or four as long as it is two or more. Even in the case of three or more, the vibration meters may be arranged in series at a known interval.
[0040]
In the non-destructive compression test described above, the non-destructive compression device 1 having the above-described configuration was used. However, two (or three or more) sensors are arranged at a predetermined interval without using the non-destructive compression device 1. It is possible to perform the same test.
[0041]
In addition, if you measure and record the compressive strength at the time of construction of each part such as pillars, beams, walls, and floors of the structure or at a certain time, the degree of deterioration due to subsequent secular changes, fires, earthquakes, malfunctions, etc. It is convenient because it can be judged.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a state in which a nondestructive compression test of concrete is performed by a nondestructive compression test apparatus.
FIG. 2 is a block diagram showing a control configuration of a nondestructive compression test apparatus.
FIG. 3 is a schematic cross-sectional view showing an example of a coarse / fine wave generator.
FIG. 4 is a diagram showing the relationship between elastic wave velocity and compressive strength of concrete.
FIG. 5 is a view showing waveform data detected by each vibration meter.
FIG. 6 is a view showing a state in which a nondestructive compression test apparatus is installed on concrete on which a finishing material is installed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Nondestructive compression test apparatus 2 Frame 2a Handle part 3 Vibration detection means (vibrometer)
3t detector 7 Detection result output unit (interface unit)
12 Propagation speed calculator (speed calculator)
13 Compression strength calculation output section (compression strength calculation section)
14 Time difference detection unit 15 Compression strength calculation output unit (display output unit)
16 Compression strength calculation output section (recording section)
20 Surface (concrete surface)
40 Concrete fc Compressive strength L Interval, arrangement interval (interval)
P point Q1, Q2 detection point T time difference V propagation speed (speed)

Claims (3)

In a nondestructive compression test apparatus that can determine the compressive strength of the concrete without destroying the concrete based on vibration propagated to the concrete surface,
    A plurality of vibration detecting means for detecting vibrations propagated through the concrete;
    Supporting the plurality of vibration detection means so that the plurality of vibration detection means are brought into contact with each other at positions spaced apart from each other on the surface of the concrete, and a frame made of a material having a lower elastic wave velocity than concrete;
    A detection result output unit that outputs detection results of the plurality of vibration detection means;
    A time difference detection unit for detecting a time difference between detection of vibration by one vibration detection unit and detection of the vibration by another vibration detection unit;
    A propagation speed calculation unit that calculates the propagation speed of the vibration based on the detected time difference and a separation distance between the one vibration detection unit and the other vibration detection unit;
    A compressive strength calculating unit that calculates the compressive strength of the concrete based on the propagation speed;
    A nondestructive compression testing apparatus comprising: The vibration detection means includes a horizontal sensor that measures elastic waves and / or a vertical sensor that measures shear elastic waves,
    The compressive strength calculation unit calculates the compressive strength of concrete based on the propagation speed of the elastic wave and / or the shear elastic wave,
    The nondestructive compression test apparatus according to claim 1. The vibration detection means has a rotatable sensor, and measures an elastic wave or a shear elastic wave according to the rotation position.
    The nondestructive compression test apparatus according to claim 1.

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