JP2002181677A - Nondestructive compressive strength testing method, stress estimating method and test device for concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a highly accurate nondestructive compressive strength testing method or a stress estimating method using a propagation velocity of vibration. SOLUTION: An elastic wave velocity Vc in a compressive stress direction of concrete and an elastic wave velocity Vt in a tensile stress direction perpendicular to the elastic wave velocity Vc are respectively determined. An elastic wave velocity Vo in a stress-free state is calculated on the basis of the elastic wave velocities Vc and Vt, and a compressive strength fc of the concrete is calculated. Or, a compressive stress intensity σ is calculated on the basis of the elastic wave velocities Vc and Vt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for testing non-destructive compressive strength of concrete, a method for estimating stress, and a test apparatus therefor, using a propagation speed of vibration in a structural member such as an existing structure.

[0002]

2. Description of the Related Art Conventionally, non-destructive compressive strength tests on concrete products and the like have been performed by various methods. In addition, estimation of the stress acting on the concrete formed article and the like is performed by various methods.

[0003]

It is known that the compressive strength of concrete and the stress acting on concrete are related to the propagation speed of vibration propagating in the concrete. A method for accurately and easily estimating the nondestructive compressive strength of concrete and estimating stress using the propagation velocity has not yet been established.

In view of the above circumstances, the present invention provides a non-destructive compressive strength test method and stress estimation method for concrete, and a test apparatus therefor, capable of performing high-accuracy and simple measurement using the propagation speed of vibration. The purpose is to:

[0005]

According to a first aspect of the present invention, there is provided a method for testing non-destructive compressive strength of concrete (40) subjected to compressive stress, comprising the following steps. .

(A) The concrete surface is hit by striking the surface of the concrete on an extension line connecting a plurality of compression direction detection points (Q1, Q2) arranged along the direction of compressive stress on the surface (20) of the concrete. Vibration is generated in the concrete, the vibration generated in the concrete is detected at the plurality of compression direction detection points, and the time difference at which the vibration is detected at the compression direction detection points is detected, and the detected time difference and the plurality of compressions are detected. Calculating the propagation velocity (Vc) of the vibration in the compression direction based on the interval (L) between the direction detection points.

(B) The concrete surface is vibrated on the concrete surface by hitting the surface of the concrete on an extension line connecting a plurality of detection points in the tensile direction arranged along a tensile stress direction orthogonal to the compression direction. And detecting vibration generated in the concrete at the plurality of tensile direction detection points, detecting a time difference at which the vibration is detected at the tensile direction detection points, and detecting the detected time difference and the plurality of tensile direction detection points. Calculating the propagation velocity (Vt) of the vibration in the tensile direction based on the interval between the vibrations.

(C) calculating the propagation velocity (Vo) of the vibration in the concrete under no stress based on the propagation velocity in the compression direction and the tensile direction, and calculating the compressive strength of the concrete based on the propagation velocity; Procedure for calculating and outputting (fc).

A non-destructive compressive strength test method for concrete, characterized in that the steps (a) and (b) are performed in an arbitrary order, and then the step (c) is performed.

In the present invention, it is preferable that the propagation speed of the vibration in the compression direction is Vc, the propagation speed of the vibration in the tension direction is Vt, the propagation speed of the vibration under no stress is Vo, and When the gradient at which the propagation speed of vibration changes is Kc and the gradient at which the propagation speed of vibration changes due to tensile stress is -Kt, Vo = (KcVt + KtV)
c) Using the relationship of (Kc + Kt), calculate the propagation speed of vibration at the time of no stress in the procedure of (c).
It is characterized by the following.

According to a third aspect of the present invention, a method for estimating a stress of a member subjected to a compressive stress has the following procedure.

(A) hitting the surface of the member on an extension line connecting a plurality of compression direction detection points arranged along the direction of compressive stress on the surface of the member to generate vibration in the member, Along with detecting vibration generated in the member at a plurality of compression direction detection points, detecting a time difference at which vibration is detected at the compression direction detection points, and detecting the detected time difference and an interval between the plurality of compression direction detection points. Calculating a propagation speed of the vibration in the compression direction based on the vibration.

(B) hitting the surface of the member on an extension line connecting a plurality of detecting points in the tensile direction arranged on the surface of the member along the direction of tensile stress orthogonal to the compression direction to vibrate the member; And detecting the vibration generated in the member at the plurality of tensile direction detection points, detecting the time difference of detecting the vibration at the tensile direction detection points, and detecting the detected time difference and the plurality of tensile direction detection points. Calculating the propagation speed of the vibration in the tensile direction based on the interval between the vibrations.

(C) A procedure for calculating and outputting the degree of compressive stress (σ) acting on the member based on the propagation speed in the compression direction and the tensile direction.

A stress estimating method is characterized in that the procedures (a) and (b) are performed in an arbitrary order, and then the procedure (c) is performed.

Further, in the present invention, the propagation speed of the vibration in the compression direction is Vc, the propagation speed of the vibration in the tension direction is Vt, the degree of compressive stress acting on the member is σ, and the compressive stress is σ. Σ = (Vc−Vt) /, where Kc is the gradient at which the propagation speed of the vibration changes due to and −Kt is the gradient at which the propagation speed of the vibration changes due to the tensile stress.
Using the relationship (Kc + Kt), calculate the degree of compressive stress acting on the member in the procedure of (c).
It is characterized by the following.

According to a fifth aspect of the present invention, there is provided a test apparatus (1) used for the non-destructive compressive strength test method according to the first aspect or the stress estimation method according to the third aspect. ), The vibration detection means has a detection unit (3t) that can be arranged at the compression direction detection point or the tension direction detection point, and detects a vibration via the detection unit and outputs a detection result. An output unit (7) is provided, wherein the detection units of the vibration detection units are arranged at a predetermined arrangement interval (L) between the plurality of vibration detection units.

Note that the numbers in parentheses are for convenience showing corresponding elements in the drawings, and therefore, the present description is not limited to the description on the drawings.

[0019]

As described above, according to the first aspect of the present invention, since the compressive strength of the concrete structure is not determined through the compressive strength of the test piece, there are problems in management complexity and responsiveness. There is no such thing. In addition, since a part of the structural frame to be tested is not collected, the structural frame is not damaged, and a large-scale operation is not required, so that the measurement can be performed easily. Further, since the propagation speed of vibration in the concrete is determined between the detection points, it is hardly affected by the variation in the surface hardness of the concrete, and the test results do not vary and the reliability is high. Further, based on the propagation speed in the compressive stress direction and the propagation speed in the tensile stress direction, a true propagation speed at the time of no stress is calculated, and the compressive strength of the concrete is measured based on the true propagation speed. That is, since the compressive strength is measured by correcting the effect of the stress acting on the concrete, the measured value is accurate.

According to the second aspect of the present invention, accurate measurement can be performed by a simple calculation using the relational expression.

According to the third aspect of the present invention, the degree of compressive stress acting on the structural member can be estimated by simple vibration measurement without performing a large-scale operation.

According to the fourth aspect of the present invention, accurate measurement can be performed by a simple calculation using the relational expression.

According to a fifth aspect of the present invention, there is provided a test apparatus capable of easily performing the non-destructive compressive strength test of the concrete or estimating the stress of the member.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [1. Embodiment Regarding Non-Destructive Compressive Strength Test of Concrete] FIG. 1 is a schematic view showing a state where a non-destructive compressive strength test of concrete is performed by a test apparatus. The test apparatus 1 includes an instrument 4 and a control device 10 as shown in FIG. The device 4 has a rod-shaped frame 2, which is made of a material having a lower elastic wave velocity than concrete so as not to affect the test results.

Vibrometers 3 are provided in the vicinity of both ends of the frame 2, respectively, and a gap is formed between the vibrometers 3 to form a U-shape as a whole. In the vicinity of the center of the frame 2, a handle 2a that can be gripped and carried by a tester by hand is formed. The vibration meter 3,
An interface unit 7 such as a connector electrically connected to 3 is provided, and a cable 5 is detachably connected to the interface unit 7. The side of the cable 5 opposite to the device 4 is connected to the control device 10.

FIG. 2 is a block diagram showing a control configuration of the non-destructive compressive strength test apparatus. Each vibrometer 3 has a horizontal sensor 3b, as shown in FIG. 2, and a cable 5 is connected to the horizontal sensor 3b via an interface unit 7, which is omitted in FIG. As shown in FIG. 1, each vibrometer 3 is provided with a detecting unit 3t (probe or the like) for the horizontal sensor 3b to capture vibration, and between the detecting units 3t, 3t of the two vibrometers 3, 3. The interval is a predetermined interval L.

As shown in FIG. 2, a main controller 11 is provided on the controller 10 side. The main controller 11 is connected to the main controller 11 via a filter / amplifier 6 and an A / D converter (not shown). The cable 5 described above is connected. The vibration is captured by the above-described horizontal sensor 3b, and the detection signal S1 or S2 is detected.
Is transmitted via the cable 5, and the vibration in the target frequency band is extracted and amplified by the filter / amplifier 6.

The main control unit 11 also has an internal bus
A time difference detection unit 14, a first speed calculation unit 19, a second speed calculation unit 12, a compression strength calculation unit 13, a display output unit 15, a recording unit 16, an input unit 18, a speed storage unit 17, and the like are provided. Although the device 4 and the control device 10 are separate types in FIG. 1, the function of the control device 10 may be built in the frame 2 or the like of the device 4 to provide portability and portability.

Since the test apparatus 1 and the like are configured as described above, the non-destructive compressive strength test of concrete using the test apparatus 1 is performed as follows.

(A) Measurement of Elastic Wave Velocity in Compressive Stress Direction First, as shown in FIG. 1, concrete 40 (in the figure, an example of a vertical reinforced concrete column) is to be tested with an instrument 4 (frame 2) of a test apparatus 1. Shown). At the time of installation, the detectors 3t, 3t of the two vibrometers 3, 3 are arranged so as to contact the concrete surface 20. The points at which the detecting portions 3t abut on the concrete surface 20 are detection points Q1 and Q2 (compression direction detection points), respectively. The detection points Q1 and Q2 are points arranged in the vertical direction. Since the concrete 40 is a column, compressive stress acts in the vertical direction. That is, the device 4 was installed along the compressive stress acting direction of the concrete 40.

Next, a vibration composed of a compressional wave (elastic wave) is generated in the concrete 40 by hitting a point P (FIG. 1) near the extension line connecting the two detecting portions 3t, 3t. This impact may be applied in a vertical direction along the concrete surface 20 by an appropriate method. Each vibrometer 3 of the test apparatus 1 detects the above-mentioned elastic wave with a time difference corresponding to the interval L via the detection unit 3t. Detection signals S1 and S2 from the vibrometers 3 and 3 are sequentially transmitted to the controller 10 via the cable 5 via the interface unit 7. In the control device 10, the detection signals S1 and S2 are A / D converted by an A / D converter (not shown), and the time difference detection unit 14 calculates a rise time difference T between the A / D converted detection signals S1 and S2. The data is transmitted to the first speed calculator 19. Various methods other than the above can be used for detecting the time difference T.
For example, the timer may be started when the first detection signal is received, the timer may be stopped when the next detection signal is received, and the time measured by the timer may be detected as the time difference.

The first speed calculator 19 calculates the speed Vc (propagation speed) 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 in the interval L between the detection units 3t, 3t. Therefore, the interval L is divided by the time difference T to obtain the velocity Vc of the elastic wave. The first speed calculator 19 transmits the calculated speed Vc to the speed storage 17 and stores it. When the measurement of the elastic wave velocity Vc at the detection points Q1 and Q2 is started, an input indicating that the elastic wave measurement in the compressive stress direction is performed through the input unit 18 including a keyboard, a mouse, and a switch in advance. Is going. The input is stored in the speed storage unit 17 as a flag indicating “compression stress direction”,
The elastic wave velocity Vc is stored as "elastic wave velocity in the direction of compressive stress" in association with the flag.

FIG. 5 is a diagram showing waveform data detected by each vibrometer. For example, when the interval L is 30 cm,
The waveform data of the two vibrometers 3 and 3 is as shown in DAT1. The vibrometers 3 detect the rising points A and A 'of the waveform of FIG. 5, respectively. DAT2 and DAT3 are
In this example, the intervals L are 50 cm and 100 cm, respectively. In DAT2, the vibrometers 3 and 3 detect the rising points B and B 'of the waveform, respectively.
No. 3 detects the rising points C and C 'of the waveform, respectively.

(B) Measurement of Elastic Wave Velocity in the Tensile Stress Direction Next, the fixture 4 (frame 2) of the test apparatus 1 is re-installed on the concrete 40 (not shown). In this installation, 2
It is assumed that the tensile direction detecting points (not shown) where the detecting units 3t and 3t of the two vibrometers 3 and 3 abut on the concrete surface 20 are horizontally aligned. Since the concrete 40 is a pillar, a tensile stress acts in the horizontal direction. That is, the device 4 was installed along the tensile stress acting direction of the concrete 40.

Next, by violating a point near an extension line connecting the two detection units 3t, 3t, vibration of the compression wave (elastic wave) is generated in the concrete 40. The hit may be made by hitting the side of the pillar or the like with a hammer or the like. Each vibrometer 3 of the test apparatus 1 detects the above-mentioned elastic wave with a time difference corresponding to the interval L via the detection unit 3t.
The detection signals S1 and S2 from the vibrometers 3 and 3 are
Side, and the detection signals S1 and S2 are A / D-converted by an A / D converter (not shown).
In step 4, the rise time difference T between the A / D-converted detection signals S1 and S2 is calculated and transmitted to the first speed calculation unit 19.

The first speed calculating section 19 calculates the speed Vt (propagation speed) of the elastic wave generated in the concrete by dividing the interval L by the time difference T based on the transmitted time difference T. The first speed calculator 19 transmits and stores the calculated speed Vt to the speed storage 17. When the measurement of the elastic wave velocity Vt is started, an input indicating that the measurement is an elastic wave measurement in the tensile stress direction is performed in advance through the input unit 18 including a keyboard, a mouse, a switch, and the like. The input is stored in the speed storage unit 17 as a flag indicating “tensile stress direction”, and the elastic wave velocity Vt is stored as “elastic wave velocity in tensile stress direction” in association with the flag.

(C) Calculation of the true elastic wave velocity Next, based on the elastic wave velocities Vc and Vt obtained by the procedures (A) and (B), the true elastic wave velocity Vo (the elasticity under no stress) is calculated. (Wave velocity). Before describing the procedure, the relationship between the elastic wave velocity and the stress will be described.

FIG. 7 is a graph showing the relationship between the applied load and the elastic wave velocity, and FIG. 8 is a diagram for explaining the loading experiment.
As a characteristic of the elastic wave propagating in a solid, it is affected by the stress existing in the solid, and compared to the elastic wave velocity at the time of no stress,
In the case of compressive stress, the speed tends to increase, and in the case of tensile stress, the speed tends to decrease. For example, as shown in FIG. 8, a load H is applied to a test body 62 such as concrete by a jack 61 in a reaction force frame 60. Then, the specimen 62 contains
Compressive stress acts in the axial direction (the direction of arrow C in FIG. 8), which is the same direction as the load H, and tensile stress acts in the orthogonal direction (the direction of arrow T in FIG. 8), which is a direction orthogonal to the load H.

The relationship between the load H in the loading experiment shown in FIG. 8 and the elastic wave velocity in the test piece 62 was examined.
The result was as shown in the figure. In FIG. 7, black circles indicate changes in elastic wave velocity in the axial direction (the direction of arrow C where compressive stress acts), and white circles indicate changes in elastic wave velocity in the orthogonal direction (the direction of arrow T generated by tensile stress). The elastic wave velocity linearly increases with increasing load H under compressive stress, and decreases linearly with increasing load H under tensile stress. That is, it can be seen that the apparent elastic wave velocity changes according to the stress acting on the test body 62.

FIG. 3 is a graph showing the relationship between the degree of stress and the elastic wave velocity in concrete. In the present embodiment, a loading test similar to that described above was previously performed using a test piece made of the same material as the concrete 40 whose compressive strength is to be measured, and the load (stress) and the elastic wave in the test piece were measured. The relationship with the speed is obtained as shown in FIG.

As shown in FIG. 3, the elastic wave velocity of concrete subjected to compressive stress is Vc, the elastic wave velocity in the orthogonal direction is Vt, and the elastic wave velocity at no stress (true elastic wave velocity) is Vo, The slope at which the elastic wave velocity increases due to the compressive stress is Kc, the slope at which the elastic wave velocity decreases due to the tensile stress is −Kt, and the degree of compressive stress acting on the concrete at that time is σ.
Then, the following two equations hold.

Vc = Vo + Kcσ (1) Vt = Vo−Ktσ (2) From the above experimental results, the values of Kc and Kt in the equations (1) and (2) are clarified. Before performing the non-destructive compressive strength test of the second speed calculating unit 12,
Is stored in

Therefore, after the above procedures (A) and (B), the second velocity calculating section 12 calls up the elastic wave velocities Vc and Vt from the velocity storage section 17, and retrieves the elastic wave velocities Vc and Vt.
By solving the simultaneous equations of the above equations (1) and (2) using the values Kc and Kt stored in advance,
The true elastic wave velocity Vo (elastic wave velocity at no stress) is calculated and obtained. That is, Vo = (KcVt + KtVc) / (K
c + Kt).

(D) Calculation of Compressive Strength FIG. 4 is a diagram showing the relationship between elastic wave velocity and compressive strength of concrete. The compression strength calculation unit 13 calculates the compression strength by substituting the true elastic wave velocity Vo calculated by the second speed calculation unit 12 into a relational expression between the elastic wave velocity and the compression strength statistically obtained from an experiment. In general, for each type of concrete, the relationship between the strength (N / mm ² ) of the concrete and the true elastic wave velocity (m / s) propagating through the concrete is determined. For example, for the concrete to be tested in the present embodiment, as shown in FIG. 4, an experimental statistical formula of the concrete compressive strength fc and the true elastic wave velocity Vo; fc = Φ (V
o) is obtained in advance based on an experiment, and the compressive strength calculator 13 holds the experimental statistical formula; fc = Φ (Vo). Therefore, the compressive strength calculator 13 calculates the experimental statistical formula;
= Compression strength fc of concrete is obtained by substituting the elastic wave velocity Vo for Φ (Vo).

The compression strength f calculated by the compression strength calculator 13
c 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.

As described above, in the present embodiment, since the compressive strength of the concrete structure is not determined via the compressive strength of the test piece, there is no need for complicated management and compatibility. In addition, since a part of the structural frame to be tested is not collected, the structural frame is not damaged, and a large-scale operation is not required, so that the measurement can be performed easily. In addition, since the velocity of the elastic wave in the concrete is obtained between the two vibrometers 3 and 3, it is hardly affected by the variation in the surface hardness of the concrete, and the test results do not vary.
High reliability. Further, the true elastic wave velocity at the time of no stress is calculated from the elastic wave velocity in the compressive stress direction and the elastic wave velocity in the tensile stress direction, and the compressive strength of the concrete is measured based on the true elastic wave velocity. That is, since the compressive strength is measured by correcting the effect of the stress acting on the concrete, the measured value is accurate.

In the above-described embodiment, the test is performed with the vibration generated in the concrete as the vibration caused by the compression wave (elastic wave). However, the test can be performed with the vibration as the shear elastic wave. In this case, as shown in FIG. 2, the vibrometer 3 is provided with a vertical sensor 3a. For example, as shown in FIG. 1, a point P near an extension line connecting the two detection units 3t, 3t may be hit almost vertically to the concrete surface 20 by a hammer or the like.

The relationship between the elastic modulus and the shear elastic modulus is expressed by G
= E / {2 (1 + ν)} holds. On the other hand, the elastic wave velocity and shear wave velocity is the elastic modulus and the unit volume weight, elastic wave velocity ^{Ve = (E / ρ) 1/2} , shear acoustic wave velocity ^{Vs = (G / ρ) 1} /2 in relation There is. Therefore, G
= (Vs / Ve) ² · E. With these equations, mutual conversion between elastic wave velocity and shear elastic wave velocity is possible by calculation. In this case, since the first velocity calculating section 19 calculates the shear elastic wave, the shear elastic wave may be converted into an elastic wave velocity using the above equation and stored in the velocity storage section 17.

As another method, instead of the relationship between the stress intensity and the elastic wave speed shown in FIG. 3, the relationship between the stress intensity and the shear elastic wave speed is obtained, and the compressive strength and the elastic wave speed shown in FIG. By calculating the relationship between the compressive strength and the shear elastic wave velocity instead of the relation described above, the concrete compressive strength may be calculated through a procedure for calculating the true shear elastic wave velocity.

Each vibrometer 3 may have both of the sensors 3a and 3b in addition to the configuration having only one of the horizontal sensor 3b and the vertical sensor 3a. Providing both the horizontal sensor 3b and the vertical sensor 3a is convenient because an elastic wave or a shear elastic wave can be selectively adopted according to a test situation.

Each vibrometer 3 has only one sensor,
The direction of the sensor may be freely rotatable. For example, when elastic waves are used, the sensor is rotated and set in the same detection direction as the above-described horizontal sensor 3b for use. When a shear elastic wave is employed, the sensor is rotated and set in the same detection direction as the above-described vertical sensor 3a. By making the orientation of the sensor freely rotatable in this way, the same effect as in the case where both the horizontal sensor 3b and the vertical sensor 3a are provided is obtained, and the vibrometer can be formed simply and compactly by also using the sensor.

When the above-mentioned rotary sensor is employed,
If the rotation of the sensor is taken into the control device 10 by using an electric contact, it is possible to automatically check the vibration direction and apply the relational expression.

Since it is only necessary to be able to measure the propagation speed of the vibration (elastic wave or shear elastic wave) propagating in the interval L in the concrete, for example, one vibrometer is directly hit on the concrete surface 20 in the same manner as in the above-described embodiment. Can be obtained.

FIG. 6 is a view showing a state where a test apparatus is installed on concrete on which a finishing material is installed. As shown in FIG. 6, as a test method when the finishing material 25 such as mortar is provided on the concrete surface 20, a hole 26 having a diameter of, for example, about 1 cm penetrating the finishing material 25 portion is formed, By contacting the concrete surface 20 through the holes 26, damage to the finishing material 25 can be minimized.

In the nondestructive compressive strength test, two vibrometers are provided. If the number of vibrometers is two or more, three vibrometers are used.
Any number, such as four or four, may be used. Even in the case of three or more, the vibrometers may be linearly arranged at known intervals.

In the above-described non-destructive compressive strength test, the test apparatus 1 having the above configuration was used. However, without using the test apparatus 1, two (or three or more) sensors were arranged at predetermined intervals. Thus, a similar test can be performed.

[2. Embodiment Regarding Estimation of Stress Acting on Member] The stress acting on the concrete 40 shown in FIG. 1 is estimated. In this case, the control device 10 of the test apparatus 1 shown in FIG. The procedure of stress estimation is first described in [1. Embodiments Regarding Nondestructive Compressive Strength Test of Concrete], (A) measurement of elastic wave velocity in the direction of compressive stress, and (B) measurement of elastic wave velocity in the direction of tensile stress. Do.

Next, the procedure proceeds to a procedure for calculating and estimating the stress degree σ based on the elastic wave velocities Vc and Vt obtained in the procedures (A) and (B). Also in this procedure, the above equations (1) and (2) are used as in the procedure (C) described above (the values of Kc and Kt are obtained in advance as in the above-described embodiment). That is, the stress degree calculation unit 30 retrieves the elastic wave velocities Vc and Vt from the speed storage unit 17, and loads the elastic wave velocities Vc and Vt.
The stress degree σ is calculated by solving the simultaneous equations of the equations (1) and (2) using Vt and the values Kc and Kt stored in advance by the stress degree calculation unit 30. That is,
σ = (Vc−Vt) / (Kc + Kt).

The stress level σ calculated by the stress level calculating section 30 is transmitted to the display output section 15, and the display output section 15 displays the stress level σ via a display (not shown). The stress degree σ 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.

The members for which the stress can be estimated are not limited to concrete products, but may be other members such as steel. In addition, in the case of a material that is relatively uniform and has little variation in the true elastic wave velocity, such as steel, it is not necessary to measure the elastic wave velocity in two directions, and to measure the elastic wave velocity in only one direction. The stress can be easily obtained by applying the above equation (1) or (2) and using the elastic wave velocity at the time of no stress as Vo.

Also in the present embodiment, [1. Embodiment Regarding Nondestructive Compressive Strength Test of Concrete], a shear elastic wave may be used instead of an elastic wave.

[3. Other Application Examples] (a) Method for Managing Secular Change of Tension of Prestressed Concrete Structure It is said that the tension of prestressed concrete decreases over a long period of time due to creep or the like. In order to track such a secular change of the tension, the above-described relationship between the stress and the elastic wave velocity (see the above equations (1) and (2)) can be used.

FIG. 9 is a graph showing the relationship between the tension and the elastic wave velocity. First, when a tension is introduced into concrete during construction, the relationship between the tension and the elastic wave velocity is measured and recorded as shown by the solid line in FIG. At this time, the elastic wave velocity may be only in the tension direction. Thereafter, the elastic wave velocity (Va) is periodically measured, and plotted in a relationship diagram (see FIG. 9) between the tension and the elastic wave velocity recorded during construction. Thereby, the tension (Pa) at that time can be accurately estimated.

If an increase in concrete strength can be expected after construction, the increase is estimated and converted into a true increase in elastic wave velocity, or by using the above equations (1) and (2). The true elastic wave velocity may be obtained, and the values in the graph may be translated as indicated by the dotted lines in FIG. If the relationship between the tension and the elastic wave velocity has not been created at the time of construction, the elastic wave velocity in the direction of the tension and the direction perpendicular thereto is measured, and the above (1)
It is possible to estimate the tension by using the equation and the equation (2).

(B) Estimation of the stress generated in the structure When the existing structure is repaired or reinforced, the stress existing in the column, the beam, the wall or the like is calculated using the above equations (1) and (2). Estimation can make the design easier. In addition, in the case of failure of the structure due to uneven settlement or earthquake disaster,
The stress due to the failure is estimated using the above equations (1) and (2), and the change can be grasped by comparing with a previously measured record when the structure is in a healthy state such as at the time of completion. .

(C) Management of Stress During Construction Structural members such as pillars and beams may be temporarily dismantled or cut during renovation of a structure. In such construction,
It is necessary to replace the load supported by the structural member with a temporary member, but if sufficient measures are not taken, the burden will be applied to the surrounding members and it will cause damage, so a careful construction system is required . In such a case, if the stress of the peripheral member is measured using the above-described formulas (1) and (2) before and during the construction, the change can be easily grasped by comparing them.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a state where a non-destructive compressive strength test of concrete is performed by a test apparatus.

FIG. 2 is a block diagram illustrating a control configuration of the test apparatus.

FIG. 3 is a graph showing the relationship between the degree of stress and elastic wave velocity in concrete.

FIG. 4 is a diagram showing a relationship between elastic wave velocity and compressive strength of concrete.

FIG. 5 is a diagram showing waveform data detected by each vibrometer.

FIG. 6 is a view showing a state where a test device is installed on concrete on which a finishing material is installed.

FIG. 7 is a graph showing a relationship between a load and an elastic wave velocity.

FIG. 8 is a diagram illustrating a loading experiment.

FIG. 9 is a graph showing the relationship between tension and elastic wave velocity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test apparatus 3 Vibration detection means (vibration meter) 3t detection part 7 Detection result output part (interface part) L interval, arrangement interval (interval) Q1, Q2 Detection point T Time difference Vo Propagation speed (speed) Vc Propagation speed (speed) Vt Propagation speed (speed)

Claims (5)

[Claims] 1. A method for testing non-destructive compressive strength of concrete subjected to compressive stress, comprising: (a) an extension line connecting a plurality of compression direction detection points arranged along the direction of compressive stress on the surface of the concrete; Hitting the surface of the concrete to generate vibration in the concrete, detecting the vibration generated in the concrete at the plurality of compression direction detection points, and detecting the time difference of detecting the vibration at the compression direction detection points, Calculating a propagation speed of the vibration in the compression direction based on the detected time difference and an interval between the plurality of compression direction detection points; and (b) a tensile stress direction orthogonal to the compression direction on the concrete surface. The concrete surface is vibrated by striking the surface of the concrete on an extension line connecting a plurality of tensile direction detection points arranged along Detecting the vibration generated in the concrete at the plurality of tension direction detection points, detecting a time difference (T) at which the vibration is detected at the tension direction detection points, and detecting the detected time difference and the plurality of tension direction detections. Calculating the propagation speed of the vibration in the tensile direction based on the distance between the points; and (c) calculating the vibration of the concrete in the absence of stress based on the propagation speed in the compression direction and the tensile direction. Calculating the propagation speed and calculating and outputting the compressive strength of the concrete based on the propagation speed, performing the steps (a) and (b) in an arbitrary order, and then performing the above (c) A non-destructive compressive strength test method for concrete. 2. The propagation velocity of the vibration in the compression direction is V
c, Vt is the propagation speed of the vibration in the tensile direction, Vo is the propagation speed of the vibration under no stress, Kc is the gradient of the propagation speed of the vibration due to the compressive stress, and Gp is the gradient of the propagation speed of the vibration due to the tensile stress. Is −Kt, Vo
2. The non-destructive compression of concrete according to claim 1, wherein the propagation speed of vibration at the time of no stress in the step (c) is calculated using the relationship of = (KcVt + KtVc) / (Kc + Kt). Strength test method. 3. A method for estimating a stress of a member subjected to a compressive stress, comprising: (a) extending the surface of the member along an extension line connecting a plurality of compression direction detection points arranged along the direction of the compressive stress on the surface of the member; To generate vibration in the member, detect the vibration generated in the member at the plurality of compression direction detection points, detect the time difference of detecting the vibration at the compression direction detection points, and detect the detected time difference. Calculating the propagation velocity of the vibration in the compression direction based on the distance between the plurality of compression direction detection points, and (b) along the tensile stress direction orthogonal to the compression direction on the surface of the member. On an extension line connecting the plurality of arranged tensile direction detection points, the member strikes the surface of the member to generate vibration, and detects the vibration generated in the member at the plurality of tensile direction detection points. A step of detecting a time difference at which vibration is detected at the tensile direction detection points, and calculating a propagation speed of the vibration in the tensile direction based on the detected time difference and an interval between the plurality of tensile direction detection points; (C) calculating and outputting the degree of compressive stress acting on the member based on the propagation velocities in the compression direction and the tensile direction, wherein the steps (a) and (b) are optional. A stress estimating method, wherein the method is performed in order, and then the procedure (c) is performed. 4. The propagation velocity of the vibration in the compression direction is V
c, Vt is the propagation speed of the vibration in the tension direction, σ is the degree of compressive stress acting on the member, Kc is the gradient at which the propagation speed of the vibration changes due to the compressive stress, and the propagation speed of the vibration changes according to the tensile stress. When the gradient is -Kt,
4. The stress according to claim 3, wherein the degree of compressive stress acting on the member in the step (c) is calculated using a relationship of σ = (Vc−Vt) / (Kc + Kt). Estimation method. 5. A test apparatus used for the non-destructive compressive strength test method according to claim 1 or the stress estimation method according to claim 3, further comprising a plurality of vibration detecting means, wherein the vibration detecting means detects the compression direction. A detection unit that can be disposed at a point or a tension direction detection point, and a detection result output unit that detects a vibration through the detection unit and outputs a detection result is provided. The vibration detection is performed between the plurality of vibration detection units. A test apparatus, wherein the detection units of the means are arranged at a predetermined arrangement interval.