JP2000213998A - Bridge internal stress measurement method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a method for measuring the internal stress of a bridge, which is capable of knowing the stress state only by its own weight and knowing the internal stress state such as aging. SOLUTION: A stress in a state where a load only by its own weight of a bridge is applied is obtained from an X-ray stress measurement of crystal strain, and a stress in a service state where a vehicle load is applied is obtained from a comparison with a state where a vehicle load is not applied, The internal stress of the bridge is obtained as the sum of the stresses obtained in these two steps. This makes it possible to know the stress applied only by its own weight in the X-ray stress measurement using X-ray diffraction on crystal grains, and to easily know the internal stress of the bridge from the stress in the state where the vehicle load is applied by the strain gauge. Become like

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the internal stress of a bridge, and more particularly to a method of measuring the internal stress of a bridge, which can only be measured by its own weight, which could not be measured by a strain gauge. It is.

[0002]

2. Description of the Related Art With the recent increase in traffic volume, it is sometimes necessary to know the internal stress state of a bridge in operation for the purpose of safely managing the bridge.

Conventionally, in steel structures such as bridges, stress has been widely measured using a strain gauge.

[0004] Usually, the stress generated in the bridge is, as shown in FIG. 4, the stress in the initial state of the bridge 1 before the erection (the stress in the state of FIG. 1A) and the vehicle load of the bridge 1 after the erection. Due to its own weight without stress (stress in the state shown in FIG. 3 (b)) and the bridge 1
The stress of the bridge 1 to which the vehicle load is applied can be divided into the stress applied to the vehicle 1 (the stress in the state of FIG. 3C). Can be easily measured from a change in distortion between a state where the vehicle load is not applied and a state where the vehicle load is applied.

[0005]

However, the stress due to the weight of the bridge 1 after the erection without the vehicle load (the stress in the state shown in FIG. 3B) is obtained by attaching a strain gauge in advance in a factory or the like. If this is done, it is possible to measure the stress after the erection, but the strain gages are subject to maintenance due to the maintenance of the strain gages exposed to wind, rain, snow, etc. over a long period of time from the initial state, and the life of the strain gages themselves. However, there is a problem that it is practically difficult to measure a change in strain from the initial state of the bridge 1.

Further, even if a strain gauge is applied in advance in the initial state, the internal stress already generated by processing or the like cannot be taken into consideration, and the strain gauge cannot completely measure the stress in the initial state. There is also.

Therefore, conventionally, it has been practiced to estimate a stress state due to its own weight from a deflection under a state where a vehicle load is applied. For example, as a method of estimating the stress state, a stress frequency measurement (stress degree frequency distribution measurement) is performed. ), The soundness is estimated from the difference between the calculated value and the measured value, and the stress state due to its own weight is also estimated. As a method of estimating from the bending, the calculated value of the bending (the case of the own weight and the vehicle) The internal stress state is estimated by calculating backward from the load (in the case of load) and the measured value (in the case of vehicle load), but in any case, the internal stress state of the bridge can be indirectly known. Not too much, one more
There is a problem that it is impossible to accurately know the secular change of the stress state of the bridge for a long period of 0 to 30 years.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and it is intended to know the stress state only by its own weight, which could not be measured with a strain gauge, and to know the internal stress state such as aging. It is an object of the present invention to provide a method for measuring the internal stress of a bridge that can be used.

[0009]

In order to solve the problems of the prior art, a method for measuring internal stress of a bridge according to claim 1 of the present invention uses a method of measuring a stress in a state where a load of only the bridge's own weight is applied to a material. A process in which the X-ray stress of crystal strain is determined by comparing with the initial state of the process, and a process in which the stress in the service state where the vehicle load is applied is determined by comparing with the condition where the vehicle load is not applied. Calculating the internal stress of the bridge as the sum of the stresses.

According to this method for measuring the internal stress of a bridge, the stress in a state where a load of only the bridge's own weight is applied is determined from the X-ray stress measurement of crystal strain, and the stress in a service state where a vehicle load is applied is determined. From the comparison with the state that does not add,
The internal stress of the bridge is calculated as the sum of the stresses obtained in these two steps. The X-ray stress measurement using X-ray diffraction on the crystal grains is used to know the stress applied only by its own weight,
The internal stress of the bridge can be easily known from the stress in the state where the vehicle load is applied by the strain gauge.

According to a second aspect of the present invention, there is provided a method for measuring the internal stress of a bridge, wherein in addition to the configuration of the first aspect, a sample in an unstressed state is used as an initial state of the material, and a comparison with the value is performed. The stress is obtained.

According to this method for measuring the internal stress of a bridge, a sample in an unstressed state is used as an initial state of a material. By comparing with this, the stress to which only the current weight is applied can be easily obtained. You can easily know the internal stress of the bridge.

According to a third aspect of the present invention, there is provided a method for measuring internal stress of a bridge according to the first aspect of the present invention, further comprising: a crystal distortion of a portion of the bridge to which no stress is applied as an initial state of the material. The X-ray stress measurement is performed, and the stress is determined by comparison with the measured value.

According to this method for measuring the internal stress of a bridge, the measured value of the X-ray stress of the crystal strain of the material in the portion of the bridge where no stress is applied is used as the initial state of the material. It is possible to easily know the stress applied by the current weight only, and easily know the internal stress of the bridge.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, the method for measuring the internal stress of a bridge according to the present invention is as follows: 1: stress σ1 due to a load of its own weight, 2: stress σ2 during operation due to a vehicle load, and 3: these stresses σ1, σ2. It consists of three steps to find the bridge stress σ from
In particular, in the conventional method using a strain gauge, it was not possible to measure the stress .sigma.1 due to a load of only one's own weight.

The respective steps will be described below.

1: Measurement of Stress σ1 Due to Load of Its Own Weight The stress σ1 of load due to its own weight is measured by an X-ray stress measurement method, that is, an X-ray diffraction method.

In the stress measurement by the X-ray diffraction method, as shown in FIG. 2, a characteristic X-ray having a wavelength λ is applied to a polycrystalline sample which is an aggregate of crystal grains having a random orientation. When irradiated at an angle of ψ0 with respect to the normal, X-rays are diffracted by selecting crystal grains having a diffraction surface satisfying the black diffraction condition (1).

N · λ = 2d · sin θ (1) where d is a diffraction plane interval, θ is a diffraction angle, and n is a diffraction order, and may be usually n = 1.

Further, the distance between the diffraction planes in the unstrained state is d0,
Assuming that the distance between the diffracting surfaces in the strained state is d, the distortion Δd / d0 in the normal direction of the diffracting surface is given by the expression (2) from the expression (1).
Can be written.

Δd / d0 = −cot θ · Δθ (2) Therefore, it can be seen that the change Δd of the diffraction plane interval d, that is, the strain, can be obtained from the change Δθ of the diffraction angle θ.

Further, since the change Δθ of the diffraction angle θ with respect to the constant strain is larger for a diffraction surface having a larger diffraction angle θ, it can be understood that the accuracy is higher when a diffraction surface having a larger diffraction angle θ is used in X-ray stress measurement.

In such an X-ray diffraction method, a sin ² ψ method is used as a technique for measuring the X-ray stress of a polycrystal by angular dispersion.

Considering that the crystal is a random crystal and X-rays penetrate only into the surface layer of the sample, the stress state is plane stress.
From the slope M of the regression line of the relationship between the diffraction angle 2θ and sin ²測定 measured at different tilt angles ψ, the stress σx
Is found.

Σx = S · M (3) where S is called a stress constant and is given by equation (4). E is Young's modulus and ν is Poisson's ratio.

S = −cot θ0 {E / 2 (1 + ν)} · (π / 180) (4) If this value is known, the diffraction angle 2θ is obtained as shown in FIG.
Than the slope M of the regression line relationship between sin ² [psi, stress σx
Is found.

Although a mechanical value may be used as the elastic coefficient in the above equation, the stress can be obtained with higher accuracy by using the X-ray elastic coefficient.

In a specific measurement, a measurement position such as a girder portion of a bridge to be measured is polished to a diameter of about 3 mm, and X
This is performed by measuring the diffraction angle with a linear stress measuring device.

Measurement of X-Ray Stress in Unstrained State In order to know the stress caused by the load of the current bridge's own weight only, the self-weight in the initial state, for example, when the material is shipped from a factory or when the bridge is erected on site is completed. It is necessary to know the internal stress due to

Here, an X-ray diffraction angle of a crystal grain of this sample is obtained by using a sample in a non-strain state such as a sintered material having the same composition as the bridge as the initial state.

In the initial state, there is a part which is theoretically in a stress-free state as a structure, such as near the open end of a bridge girder in an erected state. Ask for.

X-Ray Stress Measurement in Strained Current State A measurement position such as a girder part of a bridge to be measured is determined, each measurement point is polished by about 3 mm in diameter, and an X-ray diffraction angle is measured by an X-ray stress measurement device. Is measured.

Calculation of Stress Due to Load Due to Its Own Weight When the X-ray diffraction angle in the initial state and the X-ray diffraction angle in the current state are obtained, the amount of change in the X-ray diffraction angle from the initial state to the present is calculated. The stress σ1 due to the load of its own weight is obtained.

2: Measurement of stress σ2 during service due to vehicle load Strain measurement using strain gauge, etc. The stress during service due to vehicle load is determined in the same manner as in the conventional stress measurement by determining the measurement position such as a bridge girder. A strain gauge is attached to the measurement point, and the strain in a state where the vehicle load is applied is measured based on a state where the vehicle load is not applied.

Calculation of Stress During Operation When the strain in the state where the vehicle load is applied is measured based on the state where the vehicle load is not applied, the stress σ 2 in the state where the vehicle load is applied can be obtained.

3: Calculation of the internal stress of the bridge In this way, when the stress σ1 due to the load of its own weight is calculated in 1 and the stress σ2 in service due to the vehicle load is calculated in 2, the internal stress of the bridge is calculated as the sum of these stresses. The stress σ can be determined.

As described above, according to this method for measuring the internal stress of a bridge, it is possible to obtain the stress by the load of its own weight by the X-ray stress measurement method, which could not be obtained by the conventional measurement using a strain gauge. In addition, the internal stress of the bridge can be known in combination with measuring the stress in service when a vehicle load is applied using a strain gauge or the like.

Based on the internal stress of the bridge, the useful life and the like of the bridge can be grasped, and the information can be used as information useful for management.

According to the method for measuring the internal stress of a bridge, the aging of the bridge can be easily known by measuring the same measurement position over time.

[0040]

As described above in detail together with one embodiment, according to the method for measuring the internal stress of a bridge according to the first aspect of the present invention, the stress in a state where only the bridge's own weight is applied is applied. Is determined from the X-ray stress measurement of crystal strain, the stress in the service state where the vehicle load is applied is determined from the comparison with the state where the vehicle load is not applied, and the internal stress of the bridge is calculated as the sum of the stresses obtained in these two processes. Since it was determined, the internal stress of the bridge can be easily known from the stress applied by the load of its own weight by the X-ray stress measurement using X-ray diffraction on the crystal grains, and the stress under the state where the vehicle load is applied by the strain gauge be able to.

According to the method for measuring internal stress of a bridge according to the second aspect of the present invention, a sample in a non-stressed state is used as an initial state of a material. You can know the internal stress of the bridge easily by knowing the stress applied only by the load.

Further, according to the method for measuring the internal stress of a bridge according to the third aspect of the present invention, the measured value of the X-ray stress of the crystal strain of the material in the portion of the bridge where no stress is applied is used as the initial state of the material. Therefore, by comparing with this, it is possible to easily know the stress applied by the load of the current own weight, and easily know the internal stress of the bridge.

Therefore, according to each of these inventions, it is possible to know the stress state of the bridge over time, and it becomes easy to manage the service life of the bridge and the like.

[Brief description of the drawings]

FIG. 1 is a flow chart of a measurement principle according to an embodiment of a bridge internal stress measuring method of the present invention.

FIG. 2 is a diagram illustrating the principle of X-ray stress measurement according to an embodiment of the method for measuring internal stress of a bridge according to the present invention.

FIG. 3 is an explanatory diagram of a sin ² ψ method as an X-ray stress measurement method according to an embodiment of the bridge internal stress measurement method of the present invention.

FIG. 4 is an explanatory diagram of different stress states generated in a bridge.

[Explanation of symbols]

 d Diffraction plane spacing θ Diffraction angle

Claims (3)

[Claims] 1. A step of obtaining stress in a state where a load only by its own weight of a bridge is applied by X-ray stress measurement of crystal strain from comparison with an initial state of a material, and determining a stress in a service state where a vehicle load is applied to a vehicle. A method for measuring the internal stress of a bridge, comprising: a step of determining from a comparison with a state where no load is applied; and a step of determining an internal stress of the bridge as a sum of the stresses determined in these two steps. 2. The method for measuring internal stress of a bridge according to claim 1, wherein a stress-free sample is used as an initial state of the material, and the stress is determined by comparison with the value. 3. An X-ray stress measurement of a crystal strain of a material to which a stress is not applied in the bridge as an initial state of the material, and the stress is obtained by comparing the measured value with the measured value. 2. The method for measuring internal stress of a bridge according to 1.