JP2010204055A - Concrete internal inspection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-destructive inspection apparatus for extensively inspecting an internal quality of concrete in a short time by simply disposing transmission and reception antennas on both sides of a concrete wall of a concrete structure. <P>SOLUTION: The apparatus includes the transmission antenna to be disposed on one wall surface of the concrete wall to be inspected on the internal quality; the reception antenna to be disposed on the other wall surface, the transmission antenna and the reception antenna being array antennas having a plurality of antenna elements arranged in a matrix and disposed generally facing each other on both the sides of the concrete wall; a transmission/reception control means between the transmission and reception antennas for transmitting/receiving an electromagnetic wave; and an internal quality analytical means for measuring transmission characteristics and/or reflection characteristics and analyzing the internal quality. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inspection device for analyzing and inspecting the internal quality of concrete by nondestructive using electromagnetic waves.

The mechanical strength of the concrete that constitutes the walls of buildings such as buildings and the piers of expressways is influenced not only by the composition ratio of the concrete but also by the construction method and conditions during concrete placement.
In addition, the concrete strength changes over time due to the influence of the installation environment.
Therefore, it is necessary to evaluate the quality of concrete in order to ensure the mechanical resistance of concrete buildings to earthquakes.

As a method for evaluating the quality of concrete, the direct method in which a part of a specimen is cut out and a destructive test is performed is an estimation method using a sample, so that it is not easy to inspect the whole specimen.
Therefore, as a non-destructive diagnostic method, Reference 1 discloses a remote internal inspection method for concrete buildings and the like by ultrasonic waves.
However, it takes a lot of labor to inspect the entire subject by the ultrasonic method.
Further, in the non-destructive diagnostic method using X-rays, there is a current situation that concrete having a thickness of several tens of centimeters or more does not permeate due to safety control restrictions.

Patent Document 2 discloses a nondestructive inspection apparatus and method for a reinforced concrete structure using electromagnetic waves.
However, in the technique disclosed in the publication, in order to remove the influence of the reflected wave from the crossing rebar, the inspection range must be divided into six sections, and the average waveform of the received signal in each section must be obtained. The scanning movement must be made, and the apparatus becomes a large scale.

As a device for examining reinforcing bars in concrete, a reinforcing bar survey radar (RC radar) that measures the reflection time of electromagnetic pulses is commercially available, but this does not test the quality of concrete.
That is, this RC radar is intended to detect reinforcing bars, and its depth is limited to about 30 cm.

JP 2001-289827 A JP 2008-39429 A

  An object of the present invention is to provide a non-destructive inspection apparatus capable of inspecting the internal quality of concrete in a wide range and in a short time only by arranging transmission and reception antennas on both sides of a concrete wall of a concrete structure.

  A concrete internal inspection apparatus according to the present invention includes a transmission antenna disposed on one wall surface of a concrete wall to be inspected for internal quality, and a reception antenna disposed on the other wall surface. A transmission / reception control means for transmitting and receiving electromagnetic waves between the transmission / reception antennas, wherein the transmission antenna and the reception antenna are arranged substantially opposite to each other on both sides of the concrete wall, and a transmission characteristic. Or / and internal quality analysis means for measuring reflection characteristics and analyzing internal quality.

Here, the transmission / reception antenna in which a plurality of antenna elements are arranged in a matrix is used because a plurality of antenna elements to be transmitted and received are arranged in, for example, the horizontal direction and the vertical direction in order to suppress the influence of directivity of the reception antenna. This is intended to be arranged in a matrix shape, and the transmitting antenna and the receiving antenna are generally arranged opposite to each other on both sides of the concrete wall surface.
This makes it possible to measure transmission characteristics and reflection characteristics in a direction perpendicular to the concrete wall surface between the antenna elements arranged opposite to each other.
In addition, since the transmission / reception antenna is a two-dimensional array antenna, a wide range of measurements can be performed in a short time.
The electromagnetic wave used for the analysis of the internal quality is preferably a 1.0 to 3.0 GHz band quasi-microwave having high transmission characteristics to concrete in consideration of regulations of the Radio Law.
When this quasi-microwave is used, it is possible to inspect the concrete to a measurement depth (cover) of about 100 cm.
It should be noted that the difference in the density of concrete, the part of the gravel called junker that was not sufficiently filled with ready-mixed concrete, and the transmissivity and reflectivity of electromagnetic waves by reinforcing bars, etc. depend on the frequency. In order to investigate the nature, it is better to perform measurement at a plurality of frequencies.

In the present invention, since the transmitting / receiving antenna is a two-dimensional array antenna, the transmitting array antenna transmits a marker signal from the antenna element, detects the antenna element of the receiving array antenna that has received the marker signal, and detects the opposing antenna. You may make it have a counter antenna element automatic detection means for detecting an element automatically.
If it does in this way, the antenna element which opposes will be automatically detected only by arrange | positioning a transmission antenna and a reception antenna substantially in opposition.
If three or more marker signals are provided, the positions in the X and Y directions are determined.
In addition, the transmission and reflection of electromagnetic waves are assumed to vary depending on the concrete directionality of concrete, the structure of the jumper and the direction of the reinforcing bars. Therefore, the antenna element of the transmission / reception array antenna has horizontal polarization and vertical polarization. It may be possible to transmit and receive polarized waves in at least two directions.
Furthermore, the transmission surface of the transmission array antenna can be substantially in close contact with the concrete wall so that the transmission power is not reflected by the concrete surface, and the impedance of the material forming the transmission surface substantially matches the impedance of the concrete. It is good to do so.
Here, the fact that the transmission surface can be substantially in close contact with the concrete wall surface means that even if there are some irregularities on the concrete surface, it is only necessary to be able to overlap the concrete surface.

In the present invention, by using a transmission / reception antenna composed of a two-dimensional array antenna, a wide range of measurements can be realized in a short time by measuring transmission and reflection characteristics in a direction perpendicular to the wall surface of the concrete. Investigate overall solidity and inspect internal quality.
As a result, it is possible to detect the remarkable deterioration of concrete, the presence of non-metal objects such as jumpers and PVC pipes for electrical wiring, and cavities.
It should be noted that the detection of reinforcing bars can cope with a fog more than twice that of the conventional RC radar.

  In addition, by arranging two-dimensional array antennas facing each other, it is possible to obtain transmission characteristics in an oblique direction by measuring a total of nine points including the top, bottom, left, and right of the facing antenna elements. Transmission characteristics can also be obtained.

The structural example of the inspection apparatus which concerns on this invention is shown. An example of element arrangement of a transmission / reception two-dimensional array antenna is shown. An example of inspection of the internal quality of concrete will be shown.

The structural example of the inspection apparatus 10 inside the concrete which concerns on this invention is shown.
The transmitting antenna 11 is disposed so as to overlap with one wall surface of the concrete wall 1, and the receiving antenna 12 is disposed so as to overlap with the other wall surface.
As shown in FIG. 2, the transmission / reception antennas 11 and 12 are two-dimensional array antennas in which a plurality of antenna elements 20 are vertically and horizontally arranged in a matrix.
The size and number of the antenna elements 20 affect the analysis performance and are set according to the required accuracy.
In this embodiment, the antenna elements 20 having a = 30 mm and b = 30 mm are arranged in the form of 8 × 8 = 64 elements in the vertical and horizontal directions at a pitch of the center distance c = 35 mm.
In addition, the material of the portion of the transmitting / receiving antennas 11 and 12 with the built-in antenna element 20 that overlaps the concrete wall surface is generally matched to the impedance of the concrete.
As a transmission / reception control means, a quasi-microwave is generated from an electromagnetic wave generator 13 controlled by a control unit 14 such as a personal computer, and sequentially applied to each antenna element constituting a two-dimensional array of transmission antennas 11.
In synchronization with this, the intensity and phase of the transmitted wave are measured by the measuring instrument 15 one by one by the antenna element 20 constituting the two-dimensional array of the receiving antennas facing each other.
At the same time, the reflectivity and phase of the reflected wave are also measured.
As the electromagnetic wave used for measurement, a plurality of quasi-microwaves (1.0 to 3.0 GHz) are preferably used, and in this embodiment, frequencies of 1.8, 2.1, and 2.4 GHz are used.
Based on the measured data, the internal quality is analyzed by the analysis unit 16 as internal quality analysis means.
Before starting the measurement, it is preferable to transmit a marker signal from the transmitting antenna and detect a pair of opposing antenna elements 20 in advance based on the position coordinates of the antenna elements of the opposing receiving antenna receiving the marker signal. .
In addition, in the configuration example of the apparatus shown in FIG. 1, the transmission / reception antenna signal is transmitted by a cable. Can be used.

FIG. 3 shows an embodiment in which the internal quality of concrete is inspected using the transmission / reception antennas 11 and 12.
FIG. 3A is a plan view of a target concrete wall, and FIG. 3B is a side perspective view.
The concrete wall 1 is manufactured on a trial basis, and has a φ35 mm PVC pipe 5 embedded as an example of φ19 mm rebars 2, 3, and 4 and a cavity.
FIG. 3 shows the measurement results of the cross section A and the surface B.
In the graph of the measurement result of the cross section A, the horizontal axis indicates the distance from the left end of the concrete wall 1 and the unit is cm.
The vertical axis represents the transmitted radio wave intensity received by the receiving antenna, and the unit is dB.
In the graph, antennas A and B are examples of the array antenna according to the present invention. However, this is an example in which the impedance with concrete is not matched.
Commercially available wireless LAN antennas are data measured at a frequency of 2.4 GHz using PA2409A manufactured by Natec Co., Ltd.
When a reinforcing bar or a PVC pipe is detected, it can be seen that the intensity of the transmitted radio wave is relatively lowered, and the detection ability of the antennas A and B is higher than that of a commercially available product.
The measurement result of the surface B shows a two-dimensional radio wave intensity distribution received by the opposite wall surface when the array antenna according to the present invention is applied to the wall surface B of the concrete.
A black part shows a part with weak transmitted radio wave intensity, and it can be seen that the reinforcing bars 3 and 4 are detected.
This proved that the internal quality of the concrete could be inspected.

DESCRIPTION OF SYMBOLS 1 Concrete wall 2 Reinforcing bar 5 PVC pipe 10 Inspection apparatus 11 Transmission antenna 12 Reception antenna 13 Electromagnetic wave generator 14 Control part 15 Measuring instrument 16 Analysis part

Claims (4)

A transmission antenna disposed on one wall surface of a concrete wall to be inspected for internal quality, and a reception antenna disposed on the other wall surface;
The transmitting antenna and the receiving antenna are array antennas in which a plurality of antenna elements are arranged in a matrix,
The transmitting antenna and the receiving antenna are generally arranged opposite to each side of the concrete wall,
An internal inspection apparatus for concrete, comprising: transmission / reception control means for transmitting / receiving electromagnetic waves between the transmission / reception antennas; and internal quality analysis means for measuring transmission characteristics and / or reflection characteristics and analyzing internal quality.   The transmitting array antenna has a counter antenna element automatic detecting means for transmitting a marker signal from the antenna element, detecting the antenna element of the receiving array antenna that has received the marker signal, and automatically detecting the opposing antenna element. The concrete internal inspection device according to claim 1, wherein:   3. The concrete internal inspection apparatus according to claim 1, wherein the antenna element of the transmission / reception array antenna is capable of transmitting / receiving polarized waves in at least two directions of horizontal polarization and vertical polarization.   4. The transmitting array antenna according to claim 1, wherein the transmitting surface of the transmitting array antenna is substantially in close contact with the concrete wall surface, and the impedance of the material forming the transmitting surface substantially matches the impedance of the concrete. Cranic internal inspection device.