JP3404302B2 - Vibration measurement method for civil engineering building structures - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring a vibration state of a civil engineering building such as a bridge and a method of measuring (calculating) a natural frequency of the civil engineering building based on the measured value. .

[0002]

2. Description of the Related Art Periodic maintenance and inspection of civil engineering structures such as bridges is important for proper maintenance, ensuring safety, and effective use of social capital such as economy. As the inspection means, there is one that measures the vibration state of the structure.

For example, when the rigidity of a bridge structure (bridge girder, pier, tower, etc.) is lowered, or a suspension bridge (cable stayed bridge)
When a change (slack) occurs in the cable tension of, it can be detected as a change in natural frequency. That is, the natural frequency of the structure in the normal state in the completed installation is known in advance, and the natural frequency measured periodically is
By comparing with the natural frequency in the normal state, the deterioration of the structure is judged and maintenance / inspection is performed.

As means for measuring the vibration of the structure, as shown in Japanese Utility Model Publication No. 1-36976 and Japanese Patent Laid-Open No. 5-339909, a vibration sensor or an accelerometer is directly attached to the structure for vibration measurement. It is carried out.

[0005]

In all of the above-mentioned conventional structure vibration measuring means, since the vibration sensor and the like are directly attached to the structure, the attachment work is troublesome and the measurement signal is measured by the lead wire. Therefore, it is necessary to lead it to the arithmetic decision unit on the ground, and the work is troublesome. That is, it is very troublesome to install a vibration sensor or the like and to perform lead wiring for each vibration measurement, and if the vibration sensor or the like is permanently installed, damage is likely to occur and accurate measurement cannot be performed. In particular, there is a problem of salt damage in the upper sea and freezing in cold regions such as Hokkaido, so permanent installation is not preferable. Further, the installation location of the vibration sensor and the like is often a high place, which is a dangerous work at a high place and the sea.

An object of the present invention is to make it possible to measure the vibration of a structure on the ground without attaching a measuring device to the structure.

[0007]

In order to achieve the above object, the present invention optically collimates one point of interest of a civil engineering building structure which is an object to be measured, and obtains vibration time history data of the point of interest. Is electrically taken out, and the vibration state of the structure is measured based on the time history data.

If it is optical, the point of interest can be observed from the ground. Also, as for the point of interest, a place where the movement is well understood may be arbitrarily selected. Therefore, it is possible to go to the measurement site and measure at the measurement date and time. It is preferable to attach a display such as a display plate to the point of interest to facilitate observation (measurement). For example, at night, fluorescent tape may be used.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As an embodiment of the present invention,
Luminance meter or CC for one point of interest in civil engineering structures such as bridges
A configuration can be adopted in which the vibration time history data of the point of interest is electrically taken out by the D camera, and the vibration state of the civil engineering / building structure is measured based on the time history data. The natural frequency of the civil engineering building structure can be measured by Fourier transforming the data. According to the vibration time history data, not only the natural frequency but also the actual amplitude or the like can be calculated, and the tension or the like can be calculated (see the embodiment). It should be noted that the amplitude and the like differ from the actual value and the measured value depending on the photographing distance, the degree of zooming, etc., and are calibrated each time the measurement is performed.

The luminance meter preferably has a visual angle of 0.2 °. This is a "circle that measures brightness"
This is because (See FIG. 5) is small, so that when the point of interest is a long distance from the ground, for example, in the case of a bridge cable, the change in brightness within the circle due to the cable vibration becomes remarkable, and highly accurate measurement can be performed.

The point of interest in the CCD camera is, for example, that the brightness changes on the structure or that the brightness difference becomes clear due to the difference in brightness between the structure itself and the background. The photographed image is composed of a large number of pixels arranged in a lattice, and each pixel represents light and shade. Therefore, the point of interest can be recognized as a grayscale change point on the image, and the vibration time history of the point of interest can be recorded by recording the displacement of the grayscale change point. Instead of luminance, it may be a change point of saturation, brightness, or the like. Further, the CCD camera can easily improve the accuracy by increasing the number of pixels, and if the zoom is possible, the stable accuracy can be obtained regardless of the distance.

[0012]

EXAMPLE In this example, the change in tension of the cable P of the cable-stayed bridge shown in FIG. 1 was measured. As shown in FIG. 2, a CCD camera 10, an image sensor 11, a personal computer 12, etc. were installed on the ground. CC installed in each and vibrating cable P
Take an image with the D camera 10. At this time, as shown in FIG. 3, the photographed image is composed of pixels arranged in a grid pattern of 480 vertical rows and 512 horizontal rows, and each pixel is 0.
Gradation of ˜255 represents light and shade. In the figure, the shaded portion indicates the cable P.

Now, a point S shown in FIG. 3A is set as a point of interest by utilizing the difference in brightness between the color of the cable P and the color of the background.
If the AA 'line passing through the point of interest S is defined on the image,
The gray scale of 512 pixels arranged in a line on the line AA 'is as shown in FIG. In this embodiment, the lightness change point is the lightness change point at the point where the lightness change amount is the maximum.

When the position of the gradation change point (X point coordinate in FIG. 3B) which changes every moment due to the vibration is recorded, FIG.
A time history waveform as shown in (a) is obtained. This waveform is only the vibration of the light and shade change point on the image, and the amplitude is different from the actual vibration of the cable P, but this is shown in FIG.
The characteristic (spectral intensity) in the spectral region obtained by the Fourier transform as described above is similar to the actual vibration of the cable P.

FIGS. 5 to 9 show an embodiment in which the vibration of the cable P is similarly recorded by the luminance meter 15 having the collimation angle of 0.2 °. First, as shown in FIGS. The luminance meter 15 of FIG. 7 shows a state in which the luminance in the circle changes due to the difference in brightness between the black cable P and the background.
The vibration time history shown in (a) was recorded and subjected to Fourier transform with an FFT analyzer to obtain spectrum intensity as shown in (b).

Based on the above spectrum intensity, the cable P
It is possible to specify the primary natural frequency of. Also,
The actual cable amplitude can also be calculated. At this time, in order to specify the primary natural frequency, calculate the amplitude, etc., the cable P having a known length is photographed in advance by calibration, and the ratio with the length on the image is calculated. It may be corrected by the calculated value. However, since the ratio changes depending on the shooting distance and the degree of zoom,
Calibrate.

Although the vibration shape of the cable P is complicated at first glance, it is generally constructed by superposition of natural vibration modes shown in FIGS. 8A to 8D, and the Fourier-transformed natural frequency is , In order from the smallest frequency, the first-order mode (Fig. (A)), the second-order mode (Fig. (B)), 3
Next mode ((c) in the figure), Fourth mode ((d) in the figure) ...
... The nth mode is set. Therefore, in the calculation of the cable tension by the vibration method, the method shown in FIG. 9 (1980.2) is used by the natural frequency of the first-order mode or the second-order mode.
(Publication report of JSCE) However, in the case of Nielsen bridge, in almost all cases, the tension is calculated only in the primary mode due to the specifications of the cable cross section and the design tension (see the formulas 2 and 3 in the same figure).

In each embodiment, one point of the structure itself is set as the focus point S. However, as shown in FIG. 10, the display plate 20 where the contrast is clear in bridge construction work, etc. is the focus point S.
Can be stuck to. By doing so, it becomes easy to recognize a change in brightness and the like. In the figure, the shaded area is black,
Others are white.

[0019]

As described above, according to the present invention, there is an advantage that the vibrating structure itself can measure its vibration without attaching a measuring device or the like, and the labor of measurement can be reduced. I can.

[Brief description of drawings]

[Figure 1] Schematic diagram of the bridge as the DUT

FIG. 2 is a schematic diagram of an embodiment.

FIG. 3 is an explanatory view of the operation of the same embodiment.

FIG. 4 is an operation explanatory view of the same embodiment.

FIG. 5 is an operation diagram of another embodiment.

FIG. 6 is a schematic view of the same embodiment.

FIG. 7 is an explanatory view of the operation of the same embodiment.

FIG. 8 is an operation diagram of the same embodiment.

[Figure 9] Cable tension calculation formula

FIG. 10 shows an example of a display board.

[Explanation of symbols]

P bridge cable S point of interest 10 CCD camera 11 Image sensor 12 PC 15 Luminance meter 20 display board

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Moriyoshi Kushida 1-12-19 Kitahori, Nishi-ku, Osaka City Kurimoto Iron Works Co., Ltd. (72) Naoichi Hirata 1-12-19 Kitahorie, Nishi-ku, Osaka Kurimoto Iron Works Co., Ltd. (56) References JP-A-5-52714 (JP, A) JP-A-3-315957 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01M 19/00 E01D 1/00 G01H 9/00

Claims (2)

(57) [Claims] 1. A point of interest S of a civil engineering building structure such as a bridge.
Optically collimated by the luminance meter, vibration time history data of the target point in electrical extraction, der method of measuring the vibration state of the civil engineering structures based on the time data
Then, the vibration time history data of the point of interest is converted into the vibration of the point of interest.
Obtained from the change state of the luminance in the circle of the above luminance meter
A method for measuring vibration of civil engineering and building structures characterized by the above . 2. A point of interest S of a civil engineering building structure such as a bridge.
Optically collimated by a CCD camera, the vibration time history data of the target point in electrical extraction, a method for measuring the vibration state of the civil engineering structures based on the time data, the interest The vibration of the point is the case that forms the image of the CCD camera.
Recognize as a change in the density of each pixel in the child array, and
The changed pixel displacement is used as the vibration time history data of the point of interest.
A method for measuring vibration of civil engineering and building structures , characterized by :