JP2003066154A - Stress meter and seismometer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stress meter capable of measuring a seismic wave at the stage of stress and to provide a seismometer using the same. SOLUTION: The stress meter 3 is provided with a plate-like piezoelement 11, upper and lower electrode plates 12 and 13 provided on upper and lower surfaces of the piezoelement 11, upper and lower pressure receiving plates 14 and 15 for sandwiching the plates 12 and 13 therebetween, and a cylindrical buffer case 17 for housing the plates 12 and 13 and the upper and lower plates 14 and 15.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a stress meter and a seismograph using the stress meter.

[0002]

2. Description of the Related Art A conventional seismometer measures velocity or acceleration, that is, shake, at its installation position. FIG. 8 (a) shows an example of measurement of acceleration response of an observed seismic wave by a conventional seismometer installed at the Kobe Meteorological Observatory, where the horizontal axis is time (full scale is 60 seconds) and the vertical axis is acceleration (full scale). Is ± 100
0gal), the left three acceleration responses of the gate post foundation,
The three on the right show the acceleration response of the stigma, respectively. And, FIG. 7B shows the strain response of the reinforcing bar due to this observed seismic wave, where the horizontal axis is time (full scale is 60).
Seconds), and the vertical axis represents strain (full scale ± 80 μ).

By the way, in the Hyogo-ken Nanbu Earthquake, phenomena such as jumping and scattering of gate columns and stone columns, destruction of bridge piers, etc., which cannot occur with conventional seismic acceleration, have occurred. That is, FIG.
It has become clear from (b) of (1) that it cannot be estimated that the destruction is caused. That is, in the case of an inland earthquake, it is thought that two types of waves, a shock wave with a very short cycle due to shear failure of a fault, and a ground vibration with a long cycle thereafter are transmitted. To be Among them, it is considered that in the breakage due to the shock wave, the shock wave propagates inside the structure and is superposed with the reflected wave at the end portion so that the shock stress wave exceeds the break stress, and thus the break occurs. Table 1 shows the types of data measured during an earthquake and the method of evaluating damage.

[0004]

[Table 1]

As shown in Table 1, when considering a disaster caused by an earthquake, it is the "force" that causes damage and destruction of the ground and the structure. Therefore, the mechanism of destruction of the ground and the structure by the earthquake In order to find out, it is necessary to directly measure the force introduced during the earthquake, that is, the waveform of the “shock stress wave”. Here, the shock stress wave has a very high frequency, which is different from shaking, and therefore requires a high level of technology for measurement and analysis, and requires a sensor and a measurement system different from the acceleration measurement system. However, although a stress gauge that measures static stress, such as a strain gauge, is well known, no stress gauge that measures dynamic stress is known at all.

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide a stress gauge capable of measuring seismic waves at the stress stage and a seismometer using the stress gauge.

[0007]

A stress meter according to the present invention comprises a plate-shaped piezo element, upper and lower electrode plates provided on the upper and lower surfaces of the piezo element, and upper and lower pressure receiving plates sandwiching the upper and lower electrode plates from above and below. It is equipped with and.

According to the stress meter of the present invention, it is possible to measure an impact stress wave and obtain data that directly leads to the destruction of a building.

It is preferable that the stress meter further comprises a tubular buffer case for accommodating the piezo element, the upper and lower electrode plates and the upper and lower pressure receiving plates. The buffer case can remove components of the force applied to the piezo element that are not desired to be measured. More specifically, the upper and lower pressure receiving plates have a larger diameter than the piezo elements and the upper and lower electrode plates, and are sandwiched between the upper and lower pressure receiving plates in the middle of the buffer case and between the piezo elements and the upper and lower electrode plates. An inward flange portion having a gap is provided. With this configuration, the gap between the inward flange portion of the buffer case and the piezoelectric element and the upper and lower electrode plates can prevent the radially inward force acting on the buffer case from being transmitted to the piezoelectric element.

The lower surface of the upper pressure receiving plate, the upper surface of the upper electrode plate,
More preferably, the lower surface of the lower electrode plate and the upper surface of the lower pressure receiving plate are mirror-finished. By doing so, it is possible to make it difficult to transmit the force acting on the upper and lower pressure receiving plates in the direction orthogonal to the axial direction to the piezo element. By combining this configuration with the above configuration that does not transmit the radially inward force acting on the buffer case to the piezo element, it is possible to obtain a one-way stress meter that measures the stress only in the axial direction.

Further, in the stress gauge, the upper and lower pressure receiving plates are connected by a screw member, and by rotating the upper and lower pressure receiving plates with respect to the screw member, the initial stress of the piezo element can be brought into a compressed state. Is preferably provided. This is because the shock wave propagating in the concrete propagates not only the compressive stress but also the tensile stress. Therefore, it is necessary to apply compressive strain to the piezo element in advance in order to measure the tensile stress.

Furthermore, it is preferable that an adhesive is applied to the upper surface of the upper pressure receiving plate and the lower surface of the lower pressure receiving plate. This is because when the stress gauge is embedded in the object to be measured, the adhesion with concrete or the like is improved. A stress meter constructed in this way can be installed by drilling a hole in an existing structure, inserting the stress meter into this hole, and then closing the hole with concrete. It can also be installed by supporting it in advance.

The above stress meter may be used alone, but by using it together with an accelerometer which has been often used as a seismometer, it can be used as a seismometer to obtain more useful data. it can. In this case,
The output of the stress meter is amplified by a DC amplifier (signal conditioner) having a high frequency response characteristic capable of following the dynamic stress. According to the stress meter of the present invention, this DC amplifier is not always necessary because its output (volt) is considerably high.

According to this seismograph, it is possible to study the cause of failure of a structure and preventive measures against the failure by using two seismic data (acceleration and strain stress) by an evaluation method different from the conventional one. Therefore, regarding the failure modes that are considered to be caused by the shock stress wave, new developments such as a new seismic design method for relaxing the shock stress wave, a method for reinforcing the structure, and a new design method for the new structural method can be expected. Such seismometers can be used not only as ordinary seismometers, but also as seismic measurement monitoring devices and tunnel entrance shock wave measurement devices. There is a possibility that the problem of peeling of the coated concrete can be clarified.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the seismograph (1) according to the present invention includes an accelerometer (2), a stress meter (3), and instruments for these.
(2) A processing device (4) for processing the data of (3) is provided, and the processing device (4) includes a DC amplifier (5) and an AD converter (6).
And a memory (7), a solar cell (8), a communication device (9), and an antenna (10).

The accelerometer (2) is, for example, a known strain gauge type, for example, a low pass filter: 30H.
z, −12 db, sampling frequency: 100 Hz is used.

The stress meter (3) is, for example, a piezoelectric element type with a low-pass filter of 33 kHz and a sampling frequency of 10 kHz, and is a sensor capable of detecting stress regardless of the Young's modulus of the material. Specifically, as described later, a piezo type is used as a sensor material, and it is an embedded type (a surface pasting type is also possible).

The DC amplifier (5) is referred to as a signal conditioner, a charge amplifier, etc., and a high-frequency response having a micro-frequency response of 20 kHz or more is used.

The number of channels of the DC amplifier (5) and the AD converter (6) is 2 to 6 ch.

The AD converter (6) is of a trigger built-in type and has a sampling rate of 50 μs or more.

The memory (7) has 128 MB (64 MB +
Compact Flash (registered trademark) memory of 64 MB or more is used, and it is always measured and overwritten.
Recording shall be performed by fixing the data on the trigger in the memory.

The communication device (9) and the antenna (10) are assumed to be capable of Internet compressed communication using a mobile phone system.

The external shape of the seismograph (1) is 20 × 20 × 7 cm.
The size of the stress meter (3) is 10 to 20 mm in diameter.
mm, and the thickness is about 4 to 6 mm.

As shown in FIGS. 2 and 3, the stress gauge (3) comprises a plate-shaped piezoelectric element (11), upper and lower electrode plates (12) and (13) provided on the upper and lower surfaces of the piezoelectric element, and The upper and lower pressure receiving plates (14) and (15) sandwiching the electrode plates (12) and (13) from above and below, the screw member (16) connecting the upper and lower pressure receiving plates (14) and (15), the piezo element (11), and the upper and lower sides. It is composed of a cylindrical buffer case (17) that houses the electrode plates (12) and (13) and the upper and lower pressure receiving plates (14) and (15).

The piezo element (11) senses a dynamic strain from any direction and outputs a voltage, and has a frequency characteristic capable of measuring a stress wave of an earthquake as described above.

Piezo element (11) and upper and lower electrode plates (12) (13)
Are disk-shaped with an insertion hole for screw insertion in the center, and both have the same outer diameter.

The upper and lower pressure receiving plates (14) and (15) are disc-shaped and have an outer diameter larger than the outer diameters of the piezo element (11) and the upper and lower electrode plates (12) and (13). The upper pressure receiving plate (14) is provided with a bottomed screw hole (14a) opening downward, and the lower pressure receiving plate (15) is
A bottomed screw hole (15a) that opens upward is provided.

A portion of the lower surface of the upper pressure receiving plate (14) in contact with the upper electrode plate (12), the entire upper surface of the upper electrode plate (12), the entire lower surface of the lower electrode plate (13) and the upper surface of the lower pressure receiving plate (15). A mirror surface finish (18) is applied to a portion in contact with the lower electrode plate (12).

The buffer case (17) has a cylindrical shape and is made of styrofoam resin, and an inwardly facing flange portion (19) is provided at the axial center thereof. The inner diameter of this flange portion (19) is slightly larger than the outer diameters of the piezo element (11) and the upper and lower electrode plates (12), and the inner diameter of the buffer case (15) other than the flange portion (19) does not Board (14) (15)
Is formed almost equal to. Therefore, the inward flange (19), the piezo element (11) and the upper and lower electrode plates (12) (1
There is a gap between it and 3).

As shown in FIG. 4 (a), the buffer case (17)
Since there is a gap (G) between the inward flange portion (19) of the piezo element (11) and the upper and lower electrode plates (12) and (13),
Even if a radially inward force (see arrow) acts on the entire buffer case (17), this is not transmitted to the piezo element (11). Further, since the inward flange portion (19) of the cushion case (17) is sandwiched between the upper and lower pressure receiving plates (14) and (15), the cushion case (1
7) does not come off easily. Buffer Case (17)
If the diameter is 20 mm, a minimum thickness of 0.2 mm is required to block 1% strain, which is a strain amount three times the compressive fracture strain of concrete. Styrofoam resin is used.

The lower surface of the upper pressure receiving plate (14), the upper electrode plate (12)
Since the upper surface of the lower electrode plate (13), the lower surface of the lower electrode plate (13) and the upper surface of the lower pressure receiving plate (15) are mirror-finished (18),
The horizontal dynamic strain indicated by the arrow in (b) is the pressure plate (14).
The lateral shock wave is absorbed in the sliding region (M) between the electrode (15) and the electrode plates (12) and (13), and is hard to be transmitted to the piezoelectric element (11). Thus, by using the piezo element (11) that senses the dynamic strain from any direction, the unidirectional stress meter (3) that measures only the axial force is obtained.

Since both a compressive stress and a tensile stress propagate in a shock wave propagating in concrete, it is necessary to measure both stresses. Therefore, in order to measure the tensile stress, it is necessary to apply compressive strain (prestress) to the piezo element (11) in advance. According to the above stress gauge (3), since the upper and lower pressure receiving plates (14) and (15) are connected by the screw member (16), as shown in FIG. 5, the upper and lower pressure receiving plates (14) and (15) are connected.
By rotating the with respect to the screw member (16), the initial stress of the piezo element (11) can be brought into a compressed state.
The magnitude of the prestress is adjusted in advance while observing the output of the piezo element (11).

The stress gauge (3) is attached to the structure as shown in FIG. 6, for example.

Prior to mounting, the upper pressure plate of the stress gauge (3)
On the upper surface of (14) and the lower surface of the lower pressure receiving plate (15), the adhesive layer (2
(0) is provided and wiring that leads to the electrode plates (12) (13)
(21) is connected. Then, first, a large hole (22) is drilled in the existing structure (C) to be measured, and this hole is
The stress meter (3) is inserted into (22) and temporarily fixed by the spacer (23). The axial direction of the stress gauge (3) is aligned with the direction of the stress to be measured (vertical direction in the figure). In FIG. 6, in order to measure the stress in the vertical direction, the axial direction of the hole (22) and the axial direction of the stress gauge (3) are orthogonal to each other. Then the hole
A mold (24) is attached to the opening edge of (22), and resin concrete (25), non-shrinkable concrete or heat-shrinkable mortar is filled into the hole (22) and cured. The adhesive layer (20) is preferably an epoxy adhesive whose curing time is set to about 24 to 48 hours. By doing so, the curing time of the concrete (25) and the curing time of the adhesive are the same. Alternatively, or after the concrete (25) hardens, the adhesive hardens, and the pressure receiving plates (14) and (15) and the concrete (25) are firmly bonded. When installing when a structure is built, as shown in Fig. 2 (b), the pressure gauge (3) provided with the adhesive layer (20) is used before the concrete is filled by using the wire (27). It should be attached to the rebar (26).

FIG. 7 is a diagram showing an example of measurement by the stress meter according to the present invention and the seismograph using the stress meter. This measurement was carried out by burying the accelerometer (2) and the stress meter (3) in standard sand and dropping the weight from above the standard sand, as shown in FIG. The accelerometer (2) has a low pass filter of 30 Hz, -12 db, and a sampling frequency of 10
It is a strain gauge type of 0 Hz (that is, the same specification as the accelerometer for the conventional seismograph), and the stress gauge (3) is
Low-pass filter: 33 kHz, sampling frequency:
It is of a piezoelectric element type of 10 kHz (that is, the one shown in FIGS. 2 to 5). And the velocity of P wave in standard sand is about 200 m / s. The same figure (b) is the data by the accelerometer (2), the horizontal axis is time (full scale is 12 seconds), and the vertical axis is acceleration (full scale is -0.1 to +).
0.15G). Further, FIG. 7C shows data obtained by the stress meter (3), where the horizontal axis represents time (full scale is 0.012 seconds) and the vertical axis is acceleration (full scale is −8 to
+10 G). As is clear from these data, in the conventional seismograph accelerometer (2), short stress waves with a shock wave cannot be measured, whereas according to the stress meter (3) of the present invention, Impact stress wave is 7-9
It can be seen that the data is obtained by measuring the size of G and directly leads to the destruction of the building.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a seismograph using a stress meter according to the present invention.

FIG. 2 is a sectional view of a stress meter according to the present invention.

FIG. 3 is an exploded perspective view of the same.

FIG. 4 is a cross-sectional view showing a behavior when a force other than a direction to be measured is applied to the stress gauge.

5A and 5B are diagrams showing a state in which the stress gauge is being assembled, wherein FIG. 5A is a sectional view thereof, and FIG. 5B is a perspective view thereof.

FIG. 6 is a diagram showing an example of attaching a stress meter to an object, FIG. 6A shows a case where the stress meter is attached to an existing object,
Each of (b) shows a case of being attached to a building in the middle of construction.

FIG. 7 is a diagram showing a measurement example by a stress meter according to the present invention and a seismograph using the same, in which (a) is a model for measurement, (b) is data from an accelerometer, and (c) is a model.
Indicates the data obtained by the stress meter.

FIG. 8 is a diagram showing an example of measurement by a conventional seismograph and a diagram based on it, in which (a) shows an acceleration response of an observed seismic wave,
(B) shows the strain response of the reinforcing bar due to this observed seismic wave.

[Explanation of symbols]

(1) Seismometer (2) Accelerometer (3) Stress meter (11) Piezo element (12) (13) Upper and lower electrode plates (14) (15) Upper and lower pressure plates (16) Screw member (17) Buffer case (18) Mirror finishing (19) Inward flange (20) Adhesive layer

Claims (7)

[Claims] 1. A plate-shaped piezoelectric element (11), upper and lower electrode plates (12) (13) provided on the upper and lower surfaces of the piezoelectric element, and upper and lower electrode plates (12) (1).
A stress gauge including upper and lower pressure receiving plates (14) and (15) sandwiching 3) from above and below. 2. A cylindrical buffer case (17) for accommodating a piezo element (11), upper and lower electrode plates (12) (13) and upper and lower pressure receiving plates (14) (15).
The stress meter according to claim 1, further comprising: 3. The lower surface of the upper pressure receiving plate (14), the upper surface of the upper electrode plate (12), the lower surface of the lower electrode plate (13) and the upper surface of the lower pressure receiving plate (15) are mirror-finished (18). The stress gauge according to claim 1 or 2, wherein 4. The upper and lower pressure receiving plates (14) (15) are piezo elements (11).
And has a larger diameter than the upper and lower electrode plates (12) and (13), and is sandwiched between the upper and lower pressure receiving plates (14) and (15) in the middle part of the buffer case (17), and the piezo element (11) and the upper and lower electrodes. The stress gauge according to claim 2 or 3, wherein an inward flange portion (19) having a gap between the plates (12) and (13) is provided. 5. The upper and lower pressure receiving plates (14) (15) are screw members (16).
The upper and lower pressure receiving plates (14) and (15) are connected with screw members (16).
The stress gauge according to any one of claims 1 to 4, wherein the initial stress of the piezo element (11) can be brought into a compressed state by rotating it with respect to. 6. The upper surface of the upper pressure receiving plate (14) and the lower pressure receiving plate (15)
The stress gauge according to any one of claims 1 to 5, wherein an adhesive is applied to a lower surface of the stress gauge. 7. A stress gauge (3) according to any one of claims 1 to 6,
A seismograph equipped with an accelerometer (2) for detecting acceleration.