JPS6232358A - Measuring method for ae of concrete structure - Google Patents

Abstract

PURPOSE:To measure the arrival time of a minute breakdown sound in concrete, and to locate exactly its generation source, by attaching a sensor to the end part of a measuring bar which has been stuck to the surface of a concrete structure. CONSTITUTION:A measuring bar 2 is stuck in the axial direction of the surface of a concrete structure 1, and a sensor 3 is attached to an exposed part of both ends of the measuring bar 2. In this state, when both end parts of the lower side of the structure 1 are supported by a supporting point R, and a load P is applied from the upper side of the center part, a primary crack C1 is generated, and a minute breakdown sound is transferred to the measuring bar 2, and received by the sensors 3, 3 of both the ends. The arrival time of a breakdown sound arriving to the sensors 3, 3 is different, respectively, in accordance with a position of the crack C1. Therefore, it becomes possible to calculate and locate a position of the crack C1 from a difference of the arrival time. Subsequently, when a secondary crack C2 is generated, its breakdown sound is transmitted directly to the measuring bar 2, and received by the sensor 3, therefore, it is not obstructed by the primary crack C1.

Description

[Detailed description of the invention] [Object of the invention 1 Lx] 11U old month 1 Invention month 1 Concrete, reinforced concrete tomorrow! +
When a concrete structure of Suzutanreguz1nku-L"!s causes micro-destruction due to cracks, etc., the strain energy accumulated inside the structure is released and a micro-destruction sound is generated. Regarding the measurement method using 1 called acoustic emission (acoustic emission), it is particularly useful for locating the source of cracks, etc., based on the difference in the time it takes for the AE (e.g., e.g. This is related.

Conventionally, as shown in Fig. 7, the method for locating cracks in concrete structures involves attaching AE sensors 22 to both ends of a concrete structure 20 such as a beam, and detecting cracks based on the difference in arrival time of the AE multiplied signal. Calculating the location of occurrence.

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 the fjS7 diagram above, if a secondary crack C2 occurs while the primary crack C already exists, The sensor 2 on the right side is blocked by the primary crack C of the AE double signal.
By the time it reaches 0, it will either become extremely small, or it will reach the sensor 21 by bypassing this -order crack C1.

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 of the present invention is to adhere a measurement bar to the surface of the concrete structure, and attach a sensor to the end of the measurement bar. The VF signal is used to measure the arrival time of minute fracture sounds in concrete and locate the source of the sound.

1fi Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In Fig. 151, reference numeral 1 denotes a concrete concrete structure such as a beam, to which a measurement bar 2 is adhered in the axial direction. The measurement bar 2 is thin and does not affect the strength of the concrete structure 1.

In addition to metals such as steel, the material of the measurement bar 3 may also be non-metallic materials such as plastic materials and ceramic materials, as long as the material has at least a longitudinal wave transmission velocity characteristic faster than that of concrete. .

Furthermore, the measurement bar 2 is not limited to a round bar, but may be a tube or a strip.

A sensor 3 consisting of an AE transducer such as a piezoelectric element is attached to both ends of the measuring bar 2, and an amplifier, a time difference measuring device, etc. (
(not shown) to a computer.

As shown in FIG. 2(A), the measuring bar 2 may be bonded to the surface of the concrete structure 1 by bonding the adhesive material 4 over the entire length of the concrete surface, or by bonding the measuring bar 2 to the surface of the concrete structure 1.
Glue only the area you want to measure as shown in Figure (B), or
Furthermore, as shown in FIG. 2(C), the Hunkreet structure 1
If the adhesive material 4 is to be prevented from peeling off due to large deformation, the adhesive material 4 may be bonded at intervals.

Therefore, when both lower ends of the concrete structure 1 are supported at the fulcrum R and a load P is applied to the central part from above, a primary crack C1 will first occur, and the minute cracking sound of the concrete caused by this will be measured. The signal is transmitted to the bar 2 and immediately received by the sensors 3 on both sides. These sensors 3,
Since the arrival time of the destructive sound reaching C.3 differs depending on the position of the crack CI, the position of the crack C8 can be calculated and located based on the difference in arrival time between the two sensors 2.2.

Since the breaking sound is directly transmitted to the measurement bar 2 and received by the sensor 3, it is not interfered with by the above-next crack C8.

Figure @3 shows a second embodiment in which a measuring bar 5 is glued parallel to the measuring bar 2, and in this case, for example, in the pongee direction of the concrete structure 1, it is placed at almost the same position as the crack CI. However, the elastic waves W caused by the distortion and destruction of the concrete due to the load P above can be accurately measured by the upper measurement bar 5.

The PjS4 diagram shows one measurement bar 2, 7 in the direction of the concrete structure 1 and in the transverse direction perpendicular to this direction.
At the same time, sensors 3 are placed at three locations in total: both ends of the measurement bar 2 in the axial direction and one end of the measurement bar 7 in the transverse direction.
, 8 is shown.

Therefore, in the present embodiment, when the crack C1 that has occurred has grown deeper, the position X of its origin can be accurately measured by the three sensors 3 and 3.8.
The depth of cracks can be determined with high precision.

9 is bonded to the opposite surface of the concrete structure 1 or is buried in the concrete structure 1. In this case, the embodiment shown in FIG. In comparison, if the measurement bars 2 and 9 that are orthogonal to each other cross each other, sensors 10 and 10 can be attached to the J! II section, respectively, and high-precision positioning can be performed in a two-dimensional manner.

Note that if the number of each of these measurement bars is increased as necessary, even more accurate orientation can be achieved.

Figure 6 shows the case where each measuring bar 2, 11, 13 is oriented and glued in the mutually orthogonal directions of X, Y, and Z, that is, in the three-dimensional direction. Ii
The source position within the IT object 1 can be located three-dimensionally.

[Effects of the invention 1 (1) AE measurement can be performed by easily bonding measurement bars to existing concrete structures that are already cracked and have already deteriorated.

(2) What is the situation from the initial stage of cracks to the collapse of concrete? ! ! ! But the accuracy <AE measurement can be done.

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

(4) The number of AE sensors can be reduced to enable economical measurement.

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

(6) Be able to determine the location and size of cracks in concrete in scientific experiments and research.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the first embodiment of the present invention, fpJ2 diagram (Δ
) to (C) are diagrams showing each embodiment of the bonding method, FIG. 3 is a diagram showing the second embodiment of the present invention, FIG. 4 is a diagram showing the third embodiment of the present invention, and FIG. FIG. 6 is a diagram showing a fourth embodiment of the present invention, FIG. 6 is a diagram showing a fifth embodiment of the present invention, and FIG. 7 is a diagram showing a conventional E measurement method. 1... Concrete structure, 2... Measuring bar, 3...
...Sensor, 4...Adhesive material, 5...Measurement bar, 6
...Sensor, 7...Measurement bar, 8...Sensor, 9...Measurement bar, 10...Sensor, 11...
Measuring bar, 12...sensor, 13...measuring bar,
14...Sensor%C1tC2...Crack, R・
...Fully point, P...load, W...elastic wave, X...source position. 4 and 3 @ Figure 4 Figure 5

Claims (3)

[Claims] (1) A measuring bar is glued to the surface of a concrete structure, a sensor is attached to the end of the measuring bar, the arrival time of minute breaking sounds in the concrete is measured, and the source of the sound is located. A in concrete structures
How to measure E. (2) The method for measuring AE in a concrete structure according to claim 1, characterized in that one or more measurement bars are arranged in one direction. (3) The method for measuring AE in a concrete structure according to claim 1, characterized in that one or more measurement bars are arranged in each orthogonal direction.