JP3942463B2 - Reinforced concrete stress measurement system for reinforced concrete structures - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a system for measuring the existing stress of a reinforcing bar in a reinforced concrete structure.
[0002]
[Prior art]
As shown in FIG. 13, a reinforced concrete beam 4 installed on each floor is connected to the reinforced concrete column portion (reinforced concrete structure) 1. This reinforced concrete beam 4 is formed by arranging reinforcing bars 5 and 6 according to a conventional method so as to be able to face tensile stress, and then installing a formwork and placing concrete in the inside. In general, the reinforcing bars 5 and 6 arranged by the reinforced concrete beam 4 are arranged in a transverse direction so as to include a plurality of beam main bars 5 arranged in the longitudinal direction and these beam main bars 5. A plurality of shear reinforcement bars (stirrups) 6 are secretly assembled.
[0003]
By the way, it is performed to grasp the deterioration degree of an existing reinforced concrete structure by inspecting the stress of the reinforcing bar. As a conventional stress measurement method, for example, the concrete portion of the measurement location is hung, the exposed rebar is partially smoothed with a file or the like, a strain gauge is installed, and the generated strain is measured to determine the stress. .
[0004]
Further, there is a known reinforcing bar measuring instrument for measuring the stress of a reinforcing bar. As shown in FIG. 13, this conventional reinforcing bar is welded at both ends of a reinforcing bar 7 to a reinforcing bar 5 to construct a new reinforced concrete structure. At this time, it is embedded and the stress is detected appropriately.
[0005]
[Problems to be solved by the invention]
However, in the conventional stress measurement method, the method using a strain gauge has a problem that the reinforcing bar has to be partially smoothed with a file or the like, which damages the reinforcing bar and weakens the strength of the reinforcing bar.
[0006]
On the other hand, in the method using a reinforcing bar meter, it is necessary to cut the reinforcing bar and install the reinforcing bar meter, and even if it can be used for a newly-installed reinforced concrete structure, it cannot be used for an existing reinforced concrete structure. Moreover, when the reinforcing bar embedded beforehand breaks down, the reinforcing bar must be cut and consequently cannot be replaced.
[0007]
In addition, when measuring a reinforcing bar stress using a strain gauge in an existing concrete structure, there is a problem that the measured value is an increment after the gauge is installed and the existing stress cannot be measured.
[0008]
Furthermore, the conventional reinforcing bar meter is expensive, and the construction method of cutting the reinforcing bar and installing the reinforcing bar meter also takes time, which increases the cost.
[0009]
As described above, the present invention has been made to solve the above-described problems. Regardless of existing or new construction, the present invention provides a reinforcing bar for a reinforced concrete structure that can easily and easily measure the stress of the reinforcing bar without damaging the reinforcing bar. It is to provide a stress measurement system.
[0010]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
That is, the present reinforced concrete structure reinforced concrete stress measurement system of the present invention is formed into a cylindrical shape, a hollow member in which a reinforced concrete structure to be measured is inserted into a hollow portion thereof, and wound around the inside of the hollow member. A stress measurement sensor comprising a secondary coil, a primary coil wound around the outside of the hollow member, and a thermometer for detecting the temperature of the reinforcing bar, and measuring the existing stress of the reinforcing bar in the reinforced concrete structure Before installing the stress measurement sensor on the rebar to be measured, a calibration rebar of the same type as the rebar to be measured is inserted into the stress measurement sensor, and a pulse current is applied to the primary coil. In addition, a conversion equation calculation is performed by using the induced current value obtained through the secondary coil and the temperature detected by the thermometer to obtain a conversion equation. Means and the stress measuring sensor installed on the reinforcing bar to be measured, and an induced current value is detected via the secondary coil by a pulse current applied to the primary coil, and the temperature is measured by the thermometer. And a stress calculation means for calculating a current stress of the reinforcing bar by calculating the detected induced current value and temperature using the conversion formula.
[0011]
In this configuration, when installing the stress measurement sensor, it is not necessary to cut the reinforcing bar partly with a file or the like or to cut the reinforcing bar. Moreover, the installation also only winds a coil in the inner side and the outer side of the hollow member inserted in the reinforcing bar. Therefore, the present invention does not weaken the strength of the reinforcing bars when installing the sensor. In addition, since the sensor structure is simple and inexpensive, it can be easily installed and replaced regardless of whether the sensor is installed or newly installed.
[0012]
<Additional configuration in the present invention>
The reinforced concrete stress measurement system for a reinforced concrete structure according to the present invention is composed of the above-described essential components, but can be established even when the following components are further added to the components.
[0013]
That is, in the present invention, when the stress measurement sensor is installed on a reinforcing bar of an existing reinforced concrete structure, a procedure for lifting a concrete portion around the reinforcing bar to be measured and the stress measuring sensor are measured. What has a procedure which installs in a reinforcing bar, and the above-mentioned procedure which embeds concrete in a protruding position and restores the above-mentioned existing reinforced concrete structure is also included.
[0014]
According to this configuration, the stress measurement sensor can be installed without damaging the reinforcing bars in the existing reinforced concrete structure.
[0015]
Further, in the present invention, the hollow member includes a configuration in which the hollow member has a cylindrical shape divided into two. According to this configuration, construction for installing the stress measurement sensor is further facilitated.
[0016]
Furthermore, in the present invention, the conversion formula is a relational expression of the magnetic permeability obtained from the induced current, the temperature of the reinforcing bar to be measured, and the stress applied to the reinforcing bar.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a reinforced concrete stress measurement system for a reinforced concrete structure according to an embodiment of the present invention will be described with reference to the drawings.
[0018]
[Explanation of stress measurement sensor]
First, a stress measurement sensor according to an embodiment of the present invention will be described.
As shown in FIGS. 6 and 7, the stress measurement sensor 11 includes a hollow member 12 in which a reinforcing bar (for example, a beam main reinforcing bar of a reinforced concrete beam 4) 5 to be measured is inserted into a hollow portion thereof, and an inner periphery of the hollow member 12. Are provided with a secondary coil 13 wound around, a primary coil 14 wound around the outside of the hollow member 12, and a thermometer 15 for measuring the temperature of the reinforcing bar 5.
[0019]
Although the hollow member 12 is described as a cylindrical shape in FIG. 7, the hollow member 12 is not limited to a cylindrical shape, and may be a cylindrical shape. In addition, the hollow member 12 is initially formed by splitting the reinforcing bar 5 into an insertion shape using a split member. The hollow member 12 is preferably made of a material having long-term durability. For example, the hollow member 12 is formed by solidifying a polyurethane resin.
[0020]
The primary coil 14 is connected to an input unit 16 that applies a pulse current via a signal line. The input unit 16 is connected to a power supply unit 19 that supplies a pulse current.
[0021]
The secondary coil 13 is connected to an output unit 18 that outputs an induced current value obtained from the pulse current of the applied primary coil 14 via a signal line. The output unit 18 is connected to the calculation unit 20.
[0022]
Furthermore, the thermometer 15 is a thermistor thermometer, for example, and is connected to the output unit 17 that outputs the detected temperature. The output unit 17 is connected to the calculation unit 20.
[0023]
The arithmetic unit 20 is a computer-configured device, and uses the induced current value from the output units 17 and 18 and the detected value that is the detected temperature to obtain a conversion equation for calibration (conversion equation calculating means) and conversion An induced current value and a detected temperature from the output units 17 and 18 are calculated using an equation, and the current stress of the reinforcing bar 5 is obtained (stress calculating means).
[0024]
The arithmetic unit 20 has a recording unit 21. The recording unit 21 records the conversion formula storage area 21a for storing the conversion formula obtained for each calibration reinforcing bar by the conversion formula calculation means, and the stress obtained for each reinforcing bar by the stress calculation means. It has a stress memory area 21b.
[0025]
The stress measurement sensor 11 is an Elasto-Magnetic (EM) sensor that utilizes the fact that the permeability of a steel material such as a reinforcing bar is sensitive to changes in stress.
[0026]
[Explanation of stress measurement sensor installation procedure]
Next, the stress measurement sensor installation procedure of the present invention will be described with reference to FIG. In addition, it demonstrates by the case where a stress measurement sensor is installed in the reinforcing bar in the existing concrete structure.
[0027]
First, the measurement position of the existing concrete structure is selected (step 101). Next, the position of the reinforcing bar in the structure is confirmed using a reinforcing bar probe or the like at the measurement position (step 102). This confirmation work is performed from two directions (for example, a plane direction and a front direction) as shown in FIG. The suspension position is determined by checking the position of the reinforcing bar.
[0028]
As shown in FIG. 3, the projecting operation (step 103) is performed after making four small-diameter holes 8a to 8d avoiding the reinforcing bar 5 and opening the four cutter grooves 9a to 9d in a lattice shape. Lifting out is performed (see the hanging portion 10 in FIGS. 4 and 5) to expose the reinforcing bar 5 to be measured.
[0029]
Next, in parallel with the lifting operation (step 103), the stress measurement sensor 11 is designed in consideration of the shape and installation status of the reinforcing bar to be measured (step 201), the material is procured (step 202) and created. (Step 203). In parallel with this work, the same type of reinforcing bars for calibration are prepared (step 104). The creation of the stress measurement sensor 11 at this time is a provisional creation for calibration.
[0030]
[Description of calibration]
Next, the calibration operation (step 204) of this embodiment will be described.
[0031]
The calibration work of the stress measurement sensor 11 includes the verification of the sensor intrinsic coefficient (step 211), the creation of the working point (step 212), the verification of the relation coefficient between the stress and the permeability (step 213), and the relationship between the temperature and the permeability. The test is performed in the order of the coefficient test (step 214).
[0032]
The sensor intrinsic coefficient test (step 211) is to test the output characteristics of the created stress measurement sensor 11 with respect to the prevoltage. In this step, the stress measurement sensor 11 is set in a magnetic field-free environment, a voltage is applied to the primary coil 14, and output data (inductive current value) of the secondary coil 13 at that time is measured. The output coefficient of the stress measurement sensor 11 is determined based on the relationship between the voltage value (ΔV) and the induced current value at this time.
[0033]
In the creation of the working point (step 212), the measurement point (range) in which the output characteristics at the time of magnetic field generation of the measurement wire (that is, the same type of reinforcing bar to be measured and the load is constant) is optimized is investigated. . In this step, the magnetic permeability when the measurement point (range) is changed is measured. Next, the measurement point (range) is shifted and the measurement is repeated. FIG. 9 shows the measurement values obtained by the procedure of step 212 in a graph of vertical axis: permeability and horizontal axis: output voltage. In FIG. 9, it can be seen that the rate of change of magnetic permeability is large at a position where the voltage is low, and the rate of change of magnetic permeability is small at the position where the voltage is high. Therefore, the working point at which the output characteristics are optimal is determined as an intermediate position M where the voltage is neither high nor low.
[0034]
The test of the relation coefficient between stress and permeability (step 213) is to measure the stress (load) and output value (permeability) under constant temperature conditions (constant temperature) to measure the characteristics of the measurement strand (rebar). To detect. In this step, a load is applied at every fixed stage, and an output value (magnetic permeability) is measured. Further, the relationship between the load and the output value is measured for each temperature by changing the constant temperature state (for example, every -40 ° C, -20 ° C, 0 ° C, 20 ° C, 40 ° C). FIG. 10 shows the measurement values obtained by the procedure of step 213 in a graph of vertical axis: permeability and horizontal axis: stress. Then, the relationship coefficient between stress and magnetic permeability is determined from these output relationships (graph of FIG. 10).
[0035]
In the test of the relation coefficient between temperature and magnetic permeability (step 214), the characteristics of the measurement strand are detected by measuring the temperature and the output value (magnetic permeability) under a constant stress. In this step, the output value (permeability) is measured by changing the temperature at every fixed stage. Further, the stress state is changed, and the relationship of the output value with respect to the temperature change is measured. FIG. 11 shows the measurement values obtained by the procedure of step 214 in a graph of vertical axis: permeability and horizontal axis: temperature. And the relationship coefficient of temperature and magnetic permeability is determined from these output relationships (graph of FIG. 11).
[0036]
FIG. 12 is a three-dimensional representation of the measured value graph of FIG. 10 and the measured value graph of FIG. 11. FIG. 12 shows the permeability (H), temperature (T), tensile stress (σ), and The relationship becomes clear. And the relationship between this magnetic permeability (H), temperature (T) and tensile stress (σ) is:
μ (σ, T _c , H) = μ (0, 0) + g (σ, T _c )
For example, as an approximate expression, μ (σ, T _c , H) = μ (0, 0) + m ₁ σ + m ₂ σ ² + α ₁ T _c
Note that μ (0,0), m ₁ , m ₂ , and α ₁ are constants.
It can be expressed as Therefore, the calibration operation is to obtain a constant for each measuring wire (reinforcing bar), so that the conversion formula σ = f (μ, T _c )
(Conversion formula calculation means: see step 205 in FIG. 8).
[0037]
Next, in FIG. 1, the stress measurement sensor 11 temporarily created in step 203 is installed on the reinforcing bar 5 to be measured (step 105), and the signal line of the stress measurement sensor 11 is cured (step 106). Then, an operation check operation (step 107) of the stress measurement sensor 11 is performed. That is, it is checked whether or not the stress measurement sensor 11 operates normally and the calculation unit 20 can perform stress calculation based on the above-described conversion formula.
[0038]
In this operation confirmation work, as shown in FIG. 8, measurement is performed with the thermometer 15 of the reinforcing bar 5 (step 401), and the detected value (temperature) is recorded in the recording unit 21 (step 402). Further, a pulse current is applied to the primary coil 14 (step 501), and an induced current is obtained through the secondary coil 13 and stored in the recording unit 21 (step 502).
[0039]
Next, the calculation unit 20 calculates the magnetic flux and the magnetic flux density from the obtained induced current (step 503), and calculates the magnetic permeability (step 504).
[0040]
Then, the calculation unit 20 performs calculation processing by substituting the temperature recorded in Step 402 and the magnetic permeability obtained in Step 504 into the above-described conversion formula (Step 505), and calculates stress (Step 506).
[0041]
As described above, when the operation confirmation work is completed, the concrete is placed in the protruding position and the restoration work is performed (step 108), and the installation of the stress measurement sensor 11 is completed (step 109).
[0042]
In the above-described embodiment, the case where the stress measurement sensor is installed on the reinforcing bar in the existing concrete structure has been described. However, the same applies to the case where the stress measuring sensor is installed on the reinforcing bar in the new concrete structure. That is, in the case of a new installation, step 102 (measurement object search) and step 103 (lifting operation) in FIG. 1 are not necessary, and are performed based on the procedure from the next step 104 to step 109.
[0043]
【The invention's effect】
As described above, according to the present invention, when the stress measurement sensor is installed, it is not necessary to cut the reinforcing bar partly with a file or the like or to cut the reinforcing bar. Moreover, the installation also only winds a coil in the inner side and the outer side of the hollow member inserted in the reinforcing bar. Therefore, the present invention does not weaken the strength of the reinforcing bars when installing the sensor. In addition, since the sensor structure is simple and inexpensive, it can be easily installed and replaced regardless of whether the sensor is installed or newly installed.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a flowchart showing a measurement procedure of a rebar existing stress measurement system for a reinforced concrete structure according to the present invention.
FIG. 2 is a perspective view showing a suspended position of a reinforced concrete beam.
FIG. 3 is a plan view of a suspended position of a reinforced concrete beam.
FIG. 4 is a plan view of a reinforced concrete beam after hanging.
FIG. 5 is a front view of a reinforced concrete beam after hanging.
FIG. 6 is a block diagram of a steel bar existing stress measurement system according to the present invention.
7A and 7B are external views of a stress measurement sensor attached to a reinforcing bar, in which FIG. 7A shows a front sectional view and FIG. 7B shows a partial side sectional view.
FIG. 8 is a flowchart of a measurement procedure using a stress measurement sensor.
FIG. 9 is a magnetic characteristic diagram showing the relationship between magnetic permeability and output voltage.
FIG. 10 is a magnetic characteristic diagram showing the relationship between magnetic permeability and stress.
FIG. 11 is a magnetic characteristic diagram showing a relationship between magnetic permeability and temperature.
FIG. 12 is a magnetic characteristic diagram showing a relationship among magnetic permeability H, temperature T, and tensile stress σ.
FIG. 13 is an explanatory diagram of a conventional method for measuring the existing stress of a reinforced concrete structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Column part 4 ... Reinforced concrete beam 5 ... Beam main reinforcement 6 ... Stirrup 11 ... Stress measurement sensor 12 ... Hollow member 13 ... Secondary coil 14 ... Primary coil 15 ... Thermometer 20 ... Calculation part

Claims (4)

A hollow member that is molded into a cylindrical shape and in which a reinforcing bar of a reinforced concrete structure to be measured is inserted into the hollow portion, a secondary coil wound around the inner periphery of the hollow member, and wound around the outer periphery of the hollow member A system for measuring the existing stress of a reinforced concrete structure using a stress measuring sensor including a primary coil and a thermometer for detecting the temperature of the reinforcing bar,
Before installing the stress measurement sensor on the reinforcing bar to be measured, a calibration reinforcing bar of the same type as the reinforcing bar to be measured is inserted into the stress measuring sensor, and a pulse current is applied to the primary coil to add the secondary current. A conversion formula calculating means for calibrating using the induced current value obtained through the coil and the temperature detected by the thermometer to obtain a conversion formula;
Using the stress measurement sensor installed in the reinforcing bar to be measured, an induced current value is detected through the secondary coil by a pulse current applied to the primary coil, and a temperature is detected by the thermometer. Detection means;
Stress calculating means for calculating the current stress of the reinforcing bar by calculating the detected induced current value and temperature using the conversion formula;
Reinforced concrete stress measurement system for reinforced concrete structures characterized by comprising: When installing the stress measurement sensor on a reinforcing bar of an existing reinforced concrete structure, a procedure for lifting a concrete portion around the reinforcing bar to be measured; a procedure for installing the stress measurement sensor on the reinforcing bar to be measured; The reinforced concrete stress measurement system for a reinforced concrete structure according to claim 1, further comprising a step of burying concrete at a protruding position to restore the existing reinforced concrete structure. 3. The reinforced concrete stress measurement system for a reinforced concrete structure according to claim 1, wherein the hollow member has a cylindrical shape divided into two. The said conversion formula is a relational expression of the magnetic permeability obtained from the said induction current, the temperature of the said reinforcing bar to measure, and the stress concerning the said reinforcing bar, Reinforcement existing stress of the reinforced concrete structure in any one of Claims 1-3 Measuring system.

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