JPS6234054A - Method for measuring ae in concrete structure - Google Patents

Abstract

PURPOSE:To make it possible to easily measure AE (acoustic emission) with good accuracy, by adhering a measuring plate to the surface of a concrete structure and mounting a sensor to the end part of the measuring plate and measuring the arrival time of the minute destruction sound in concrete. CONSTITUTION:A measuring plate 2 is adhered to the surface of a concrete structure 1 and sensors 3 each comprising an AE (acoustic emission) converter such as a piezoelectric element are mounted to four corner parts of the measuring plate 2 and connected to a computer through an amplifier. When primary cracking C1 is at first generated and the minute destruction sound of concrete is transmitted to the measuring plate 2, the position of the cracking C1 is calculated and located on the basis of the difference between arrival times of the sensors 3. Succeedingly, when secondary cracking C2 is generated, the destruction sound thereof is directly received by the sensors 3 through the measuring plate 2 and the position of the cracking C2 is located without being disturbed by the cracking C1. By this method, the cracking position of the concrete structure can be easily located with good accuracy.

Description

[Detailed Description of the Invention] [Objective of the Invention I IL Five-Double Folded Depth 1] The present invention provides a method for preventing damage to the inside of a concrete structure such as concrete, reinforced concrete, or steel-framed reinforced concrete when micro-fractures occur due to cracks or the like. Regarding the measurement method that utilizes the phenomenon in which the strain energy accumulated in the This relates to a method of locating the source of cracks, etc., based on the difference in arrival time.

En- Conventionally, as shown in Fig. 4, the method of locating the crack position in a concrete structure is to attach AE sensors 22 to both i parts of a concrete structure 20 such as a beam, and calculate the position from the AE multiplied signal arrival time difference. The location of crack occurrence was calculated.

Furthermore, in order to attach the sensor 22 directly to the surface of the concrete structure 20, an adhesive is used or grease is applied to bond it.

However, as is clear from Figure 4 above, for example, if a secondary crack C2 occurs while the next crack CI already exists, the resulting AE signal will be similar to that of the primary crack. Either it is blocked by C1 and becomes very small by the time it reaches the sensor 20 on the right, or it bypasses this second crack CI and reaches the sensor 21.

In this way, since cracks that develop later are greatly affected by existing cracks, it has been almost impossible to calculate their location.

In addition, the conventional sensor mounting method described above has problems such as it takes time to remove the sensor and the reception characteristics of the sensor change because the grease is absorbed into the concrete.

The present invention has been made to solve the above problems,
The purpose is to be able to accurately measure cracks that occur one after another in a concrete structure from a crack-free state to collapse at any time, and to be able to install and remove the sensor. A in concrete structures where it is easy and the reception characteristics do not change
The purpose of this invention is to provide a new method for measuring E.

[Structure of the Invention] The method for measuring AE in a concrete structure according to the present invention is to measure AE in a concrete structure through a measuring plate that is glued to the surface of the concrete structure or embedded inside the concrete structure. This method is characterized by measuring the arrival time of minute breaking sounds in concrete using a sensor attached to the end of the measuring plate, and locating the source of the sound.

K1 properties Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, 1 is a concrete structure, and a measurement [2] is adhered to the surface thereof.

The measurement plate 2 is not limited to a metal plate, and may be made of a non-metallic material such as a plastic plate or a ceramic plate, as long as it has a characteristic faster than the longitudinal wave transmission velocity characteristic of concrete.

Further, the method of adhering the measurement plate 2 may be full surface adhesion, linear adhesion, or point adhesion, depending on the purpose of measurement.

Sensors 3.3, 3.3 consisting of AE transducers such as piezoelectric elements are attached to the four corners of the measurement plate 2, and are connected to the Hunbuter via an amplifier, time difference measuring device, etc. (not shown) as appropriate. put.

Therefore, when both lower ends of the concrete structure 1 are supported at the fulcrum R and a load P is applied to the medium-heated part from above, a primary crack C1 will first occur, and the resulting micro-destruction noise of the concrete will be generated. It is transmitted to the measurement plate 2 and immediately received by the sensors 3, 3, 3.3. These sensors 3,
3.3.3 The arrival time of the breaking sound to reach 3 is the crack C
1, the position of the crack C1 can be calculated and located based on the arrival time difference at each sensor 3.

Subsequently, when the second crack C2 occurs, the breaking sound is directly transmitted to the measurement plate 2 and received by the sensor 3, so that it is not interfered with by the second crack C1.

In addition, if the crack C1 where dust is generated develops deeper, the source position X is detected by four sensors 3, 3,
．． 3, it is possible to measure accurately, and the depth of the crack can also be located with high precision.

FIG. 2 shows examples of various shapes of the measuring plate 2 to be adhered to the surface of the concrete structure 1, including large and small square measuring plates 4, rectangular measuring plates 5, circular measuring plates 6, and oval measuring plates. It is possible to use a shaped measurement plate 7, a triangular measurement plate 8, etc. as appropriate or in combination depending on the measurement location and measurement purpose.

FIG. 3 shows an example in which the measuring plate 9 is buried in the concrete structure 1. If the measuring plate 9 is large as in this example, holes 10 are made as appropriate and the concrete structure is It is best to maintain the strength of object 1.

Furthermore, it is also possible to combine the measurement plate glued to the surface of the concrete structure with the measurement plate buried inside.1゜[Effects of the invention] (1) Existing structures with cracks and deterioration already progressing. AE measurement can be easily performed even on concrete 1-structures.

(2) Accurate AE measurement is possible under any condition, from the initial stage of cracks to the collapse of concrete.

(3) No matter what kind of cracks occur after the first crack occurs, which has been impossible until now, or where they occur, A
E-measurement is possible.

(4) Economical measurement is possible by reducing the number of AE sensors.

(5) Sensors can be accurately attached to the measurement board even in places where it is not possible to attach them.

(6) It can also be applied to determine the location and size of cracks in concrete in experiments and research.

[Brief explanation of the drawing]

Fig. 1 shows the first embodiment of the present invention, Fig. 2 shows various shapes of the measurement plate, Fig. 3 shows the second embodiment of the invention, and Fig. 4 shows the conventional AE It is a figure showing a measurement method. 1... Concrete structure, 2... Measuring plate, 3...
・Sensor, L5+LL8...Measuring plate, 9...Measuring plate, 10...Hole, 11...Sensor, C1, C2・
...Crack, R...Fully point, P...Load, X...
Source location.

Claims (2)

[Claims] (1) Glue the measurement plate to the surface of the concrete structure,
A method for measuring AE, comprising: attaching a sensor to the end of the measuring plate, measuring the arrival time of minute breaking sounds in concrete, and locating the source thereof. (2) A measuring plate is buried in a concrete structure, a sensor is attached to the end of the measuring plate, the arrival time of minute breaking sounds in the concrete is measured, and the source is located. How to measure AE.