JP6984562B2 - Soundness evaluation method - Google Patents

Description

The present invention relates to a soundness evaluation method for evaluating the soundness of a structure.

It is important to evaluate the soundness of the structure in order to use it safely. A typical inspection method for evaluating the soundness of a structure is a visual inspection of the appearance. By visual inspection of the conventional appearance, it is possible to find a large deformation of the structure and a clear malfunction of various constituent members (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-214957

Tatsuya Oshio et al., Development of stress stethoscope using friction type strain gauge and application to structural soundness diagnosis, 60th Annual Scientific Lecture Meeting of Japan Society of Civil Engineers, September 2005 Jun Yamaguchi, "Development of Terahertz Imaging System", PIONEER R & D (2014)

However, in the conventional visual inspection of appearance, it is difficult to make a quantitative evaluation, so that the accuracy of the evaluation is limited. In addition, even if an abnormal stress exceeding the design stress is generated in the structure, there is a problem that it is overlooked if there is no large deformation that can be confirmed from the appearance. rice field.

The present invention has been made in view of the above, and an object of the present invention is to provide a soundness evaluation method capable of accurately measuring the soundness of a structure.

(1) In order to solve the above-mentioned problems and achieve the object, the soundness evaluation method according to one aspect of the present invention measures the stress distribution generated in a structure by a stress distribution measuring device configured to be measurable. It is a soundness evaluation method for evaluating the soundness of the structure by an analysis means based on the stress distribution of the structure, wherein the analysis means has a stress distribution based on a design in the structure and the said. It is characterized in that the soundness of the structure is evaluated by comparing the stress distribution of the structure measured by the stress distribution measuring device and the difference between the stress distribution based on the design and the measured stress distribution. And.

(2) In the soundness evaluation method according to one aspect of the present invention, in the above invention (1), the analysis means assumes the installation conditions of the constituent members that cause the stress distribution in the structure to change. In addition, the stress distribution generated in the structure under the assumed installation conditions can be derived, and the analysis means can be used when the derived stress distribution substantially matches the measured stress distribution. It is characterized in that it is determined that the installation condition of the constituent member in the measured structure is the assumed installation condition.

(3) In the soundness evaluation method according to one aspect of the present invention, in the above invention (1) or (2), the structure is configured by providing a non-metal layer on an upper layer of a metal substrate, and the stress distribution. The measuring device is configured to be able to irradiate a predetermined position on the surface of the structure with a terahertz wave, and is reflected at the predetermined position of the structure by a terahertz wave transmitting means capable of scanning the surface of the structure. It is characterized in that it is configured to be able to detect a terahertz wave and is provided with a terahertz wave detecting means capable of scanning the surface of the structure.

(4) In the soundness evaluation method according to one aspect of the present invention, in the above invention (3), the non-metal layer is irradiated with the terahertz wave emitted from the terahertz wave transmitting means, and the terahertz wave detecting means is used. By detecting the intensity of the terahertz wave transmitted through the non-metal layer, the stress state in the non-metal layer is measured, and the non-metal layer is used as a strain detecting means in the photoelastic method in the structure. It is characterized by measuring the stress distribution.

(5) In the soundness evaluation method according to one aspect of the present invention, in the invention of any one of the above (3) and (4) that cites the above (2) or the above (2), the structure is the constituent member. It is characterized by being a bridge having at least one bearing.

According to the soundness evaluation method according to the present invention, it is possible to accurately measure the soundness of a structure.

FIG. 1 is a diagram showing an example of a normal state of a bridge to be measured according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of an abnormal state in a bridge to be measured according to an embodiment of the present invention. FIG. 3 is a diagram showing a configuration of a stress measuring device according to an embodiment of the present invention. FIG. 4 is a diagram showing another configuration of the stress measuring device according to the embodiment of the present invention. FIG. 5 is a flowchart when the soundness evaluation method according to the embodiment of the present invention is applied to the diagnosis of the soundness of bearings in a bridge. FIG. 6 is a flowchart of a repair method according to an embodiment of the present invention. FIG. 7 is a diagram showing a schematic configuration of a photoelastic stress measuring device for explaining a stress measuring method by a conventional photoelastic method.

Hereinafter, a soundness evaluation method according to an embodiment of the present invention will be described with reference to the drawings. In all the drawings of the following embodiment, the same or corresponding parts are designated by the same reference numerals. Further, the present invention is not limited to the embodiments described below.

First, in explaining the soundness evaluation method according to the present invention, the principle of the present invention will be described in order to facilitate the understanding of the present invention. In one embodiment, a plate girder bridge of a bridge will be described as an example as a typical structure. Plate girders have a load called dead load generated by their own weight such as girders and decks. The plate girder has a dead load stress distribution assumed in the design according to the dead load and the installation condition or the support condition of the device for supporting the plate girder provided on the pier (hereinafter referred to as a bearing). On the other hand, if the bearings supported by the pins do not rotate properly due to deterioration over time, or if the bearings supported by the rollers do not move properly, or if there is an abnormality in the bearing installation conditions, death will occur. Changes occur in the load stress distribution.

Therefore, if the dead load stress distribution in the plate girder as the measurement target can be measured and compared with the dead load stress distribution assumed in the design, if there is a large discrepancy between the two, an abnormality will occur in the plate girder. It can be judged that it has occurred. Furthermore, the dead load stress distribution according to the support conditions is derived by changing the support conditions in the bearing of the plate girder to various conditions and performing an analysis in which the support conditions are adjusted. The dead load stress distribution in the measured plate girder is compared with the dead load stress distribution derived by the analysis, and if they match, the support condition in the derived dead load stress distribution is the support condition in the measured plate girder. It becomes possible to determine that. This makes it possible to identify what kind of abnormality has occurred in which part of the measured plate girder. If the anomaly that is occurring and the part where the abnormality is occurring can be identified, it will be possible to perform appropriate repairs on the appropriate part of the plate girder. The present invention described below has been devised by the above diligent studies.

Next, a soundness evaluation method according to an embodiment of the present invention based on the principle described above will be described. 1 and 2 are diagrams showing an example of a normal state and an abnormal state of the dead load stress distribution on the web surface of the plate girder in a steel bridge, respectively.

As shown in FIG. 1, the plate girder 30 of a steel bridge is configured to have a web 30a and a flange 30b. Both sides of the plate girder 30 are supported by a bearing 31 consisting of, for example, a pin-roller bearing that supports one end and a bearing 32, for example, a pin-fixed bearing that supports the other end. When both bearings 31 and 32 are in a normal state and function as designed, the stress distribution generated on the surface of the web 30a of the girder 30 is the stress distribution of the compressive stress 33a and the tensile stress 33b. Consistent with the stress distribution assumed in the design. On the other hand, as shown in FIG. 2, when at least one of the bearings 31 and 32 is in an abnormal state and is not functioning according to the design specifications, the compressive stress 33a and the tensile stress 33b The stress distribution of is different from the stress distribution assumed in the design (see FIG. 1).

Therefore, when the dead load stress distribution generated by the dead load is measured in the web 30a and compared with the dead load stress distribution assumed in the design, the measured dead load stress distribution is the dead load assumed in the design. If it deviates from the stress distribution, it can be judged to be in an abnormal state. Further, in an abnormal state, it is highly possible that at least one of the bearings 31 and 32 is dysfunctional.

(Measurement method of stress distribution)
In order to determine the above-mentioned normal state and abnormal state, it is necessary to measure the stress distribution generated in the plate girder 30. The method of measuring the stress distribution for measuring the stress distribution in the web 30a of the bridge will be described below.

Normally, the surface of a structure is coated with a paint or resin having excellent environmental resistance to protect the members. A typical example of these is a non-metal layer as an anticorrosion layer that protects a steel structure from corrosion, such as painting and coating. These non-metal layers are usually in close contact with the surface of the member. Therefore, since the non-metal layer is deformed according to the member, when the steel or the like as the metal substrate constituting the structure is distorted, the non-metal layer in close contact with the surface is also distorted. According to the findings of the present inventor based on Non-Patent Document 1, the strain of the metal substrate and the strain of the non-metal layer on the surface are substantially the same. Therefore, since the strain of the metal substrate can be evaluated by measuring the strain of the non-metal layer, the stress state of the metal substrate can also be evaluated.

Conventionally, a photoelastic method is known as a method for evaluating the stress of a transparent material such as resin or glass. FIG. 7 is a diagram showing a schematic configuration of a photoelastic stress measuring device for explaining a stress measuring method by a conventional photoelastic method.

As shown in FIG. 7, the conventional photoelastic stress measuring apparatus 100 includes a visible light source 101, a first polarizing plate 102, a λ / 4 wave plate 103, 104, and a second polarizing plate 105, which are arranged linearly with each other. And a camera 106. If necessary, a lens or the like is further provided. Of these, the first polarizing plate 102 and the second polarizing plate 105 are provided so that the polarization directions differ from each other by 90 ° (π / 2). On the other hand, the λ / 4 wave plates 103 and 104 are provided so that the main axis directions differ from each other by 90 °. On top of that, the polarization direction of the first polarizing plate 102 and the spindle direction of the λ / 4 wave plate 103 are provided so as to be different from each other by 45 ° (π / 4). Similarly, the main axis direction of the λ / 4 wave plate 104 and the polarization direction of the second polarizing plate 105 are provided so as to be different from each other by 45 °. The measurement object 110 made of a photoelastic body to which stress is measured is made of, for example, an epoxy resin that is transparent to visible light. The object to be measured 110 is arranged at a predetermined position between the λ / 4 wave plates 103 and 104.

When measuring the stress generated in the object to be measured 110 by the photoelastic stress measuring device 100, first, visible light is emitted from the visible light source 101. The visible light emitted from the visible light source 101 is linearly polarized by the first polarizing plate 102, and then circularly polarized by the λ / 4 wave plate 103. Visible light that has become circularly polarized light enters the measurement object 110 and causes a phase difference δ due to birefringence caused by the stress field of the measurement object 110, resulting in elliptically polarized light. The elliptically polarized light includes the case of circularly polarized light. Here, the phase difference δ generated by birefringence is proportional to _{the principal stress difference (σ 1} − σ ₂ ) of the object to be measured 110, as shown in the following equation (1).
δ = 2πCt (σ ₁ − σ ₂ ) / λ… (1)
In addition, λ is the wavelength of the light to be used, C is the photoelastic coefficient of the material of the object to be measured 110, and t is the thickness of the object to be measured 110.

The light transmitted through the object to be measured 110 is linearly polarized by the λ / 4 wave plate 104, and then the polarized light component that has passed through the second polarizing plate 105 is imaged by the camera 106. As a result, the image depending on the phase difference generated in the measurement object 110 can be captured by the camera 106, and the stress state of the measurement object 110 can be observed. The image captured by the camera 106 is obtained as an image of photoelastic fringes of a bright and dark pattern on the measurement object 110. The obtained light-dark pattern photoelastic stripes are called uniform color lines. _{By observing the imaged uniform color lines, the principal stress difference (σ 1} − σ ₂ ) as a photoelastic parameter can be derived from the thickness t of the object to be measured 110 and the photoelastic coefficient C.

On the other hand, in the photoelastic stress measuring device 100 shown in FIG. 7, the principal stress direction can be further measured by removing the λ / 4 wave plates 103 and 104. That is, in the photoelastic stress measuring device 100, the λ / 4 wave plates 103 and 104 are removed from the optical axis between the visible light source 101 and the camera 106. In this configuration, the visible light emitted from the visible light source 101 passes through the first polarizing plate 102, is polarized into linearly polarized light, and then is incident on the object to be measured 110. Here, when the polarization direction of the first polarizing plate 102, that is, the polarization direction of the linearly polarized light and the principal stress direction coincide with each other, the linearly polarized light passes through the object to be measured 110 without changing the polarization direction. Since the light transmitted through the object to be measured 110 is linearly polarized light parallel to the polarization direction of the first polarizing plate 102, it hardly transmits through the second polarizing plate 105. In this case, when the light transmitted through the second polarizing plate 105 is observed, a dark line called an isobaric line appears in the measurement object 110. On the other hand, when the polarization direction and the principal stress direction of the first polarizing plate 102 do not match, the light transmitted through the measurement object 110 has a phase difference δ due to birefringence, so that the light passes through the measurement object 110. The resulting light becomes elliptically polarized light, is polarized by the second polarizing plate 105, and is transmitted. The intensity of the transmitted light changes according to the difference in angle between the polarization direction and the principal stress direction of the first polarizing plate 102. As a result, the angle of the polarization direction of the visible light incident on the object to be measured 110 changes while maintaining the state in which the polarization directions of the first polarizing plate 102 and the second polarizing plate 105 are different from each other by 90 °. When rotated, light and darkness is generated in the light imaged by the camera 106, and photoelastic fringes are imaged corresponding to the rotation angle of the first polarizing plate 102. Based on the image of the photoelastic fringes captured by the camera 106, the principal stress direction in the object to be measured 110 can be derived.

As described above, the photoelastic stress measuring device 100 _{can detect the principal stress difference (σ 1} − σ ₂ ) and the principal stress direction as photoelastic parameters. When the principal stress difference (σ ₁ − σ ₂ ) and the principal stress direction are obtained, for example, the principal stress components σ ₁ and σ ₂ in the object to be measured 110 are derived in a separated state by the shear stress difference integration method. Will be possible. If the principal stress components σ ₁ and σ ₂ and the principal stress direction (maximum principal stress direction) are obtained, the state of the object to be measured 110, that is, the soundness of the object to be measured 110 can be evaluated in detail.

However, in the stress measurement by the photoelastic method using the conventional photoelastic stress measuring device 100 described above, since the visible light emitted from the visible light source 101 is used, the visible light is used as the measurement object 110. It was limited to those made of permeable transparent materials. On the other hand, since the resin material constituting the coating or coating used for anticorrosion against actual structures is opaque to visible light, the photoelastic method using visible light is used. Was difficult to apply.

Therefore, the present inventor came up with the idea of using a terahertz wave, which is a kind of electromagnetic wave, instead of visible light, and studied a soundness evaluation method by a photoelastic method using a terahertz wave. As described in Non-Patent Document 2, most of terahertz waves are transmitted when irradiated with a non-metal material such as a resin, while most of them are reflected when irradiated with a metal material. The present inventor pays attention to the property of the terahertz wave, and by using it in combination with the principle of the photoelastic method in which the birefringence phenomenon of electromagnetic waves is generated by strain, even in a resin which is a non-metal layer opaque to visible light. I came up with the idea that strain can be measured. Furthermore, the present inventor has found that by evaluating the strain of a non-metal layer, the strain of an object such as a steel material under the layer can be evaluated. Such a method is referred to as a "terahertz wave photoelastic method" in the present specification. That is, the present inventor has come up with the idea of using a non-metal layer made of a resin such as an anticorrosion layer in close contact with the surface of a structure as a strain sensor for measuring the strain of the structure by using a terahertz wave. .. That is, the idea was to make the non-metal layer function as a strain detecting means. By measuring the strain of the non-metal layer by using the terahertz wave photoelastic method described above by the inventor's diligent study, the strain at an arbitrary position of the structure can be measured non-contactly. Furthermore, the present inventor has conceived that a terahertz wave photoelastic method using reflection is also possible because most of the terahertz waves are reflected when the metal material is irradiated. The stress measuring device used for measuring the stress distribution according to this embodiment is configured by the above-mentioned diligent study by the present inventor.

(Stress distribution measuring device)
FIG. 3 is a diagram showing a configuration of a stress distribution measuring device according to an embodiment of the present invention. As shown in FIG. 3, the stress measuring device 1 as the stress distribution measuring device according to the embodiment includes an analysis control unit 10, a terahertz wave transmitter 11, and a terahertz wave detector 12. A structure such as a steel plate girder 30 (hereinafter referred to as a steel structure 15) to be measured in one embodiment is made of various resins such as coating and coating on the surface of a steel material 15a as a metal substrate. A non-metal layer anticorrosion layer 15b is provided and configured.

The stress measuring device 1 is configured so that the surface of the steel structure 15 can be irradiated by polarized the _{terahertz wave L 1} and can be detected after _{the terahertz wave L 2 reflected from the steel structure 15 is polarized.} It consists of a reflected terahertz wave measuring device. That is, the stress measuring device 1 has both a terahertz wave transmitting means and a terahertz wave detecting means. Here, the terahertz wave is an electromagnetic wave belonging to the so-called terahertz region, which is a frequency region of about ^{1 terahertz (1 THz = 10 12} Hz), specifically, a frequency region on the order of 100 GHz to 10 THz (10 ¹¹ to 10 ^{13 Hz).} The terahertz region is a frequency region that has both straightness of light and transmission of radio waves. In one embodiment, the frequency of the terahertz wave can be selected according to conditions such as the material and thickness of the anticorrosion layer 15b, and is selected according to the attenuation (transmittance) of the terahertz wave in the anticorrosion layer 15b. You may.

The terahertz wave transmitter 11 as a terahertz wave transmitting means has, for example, a terahertz wave generating element 11a equipped with a resonance tunneling diode (RTD) or the like, a hemispherical lens 11b, a collimating lens 11c, and an objective lens 11d. It is composed. A photo Conductive Antenna (PCA) may be used instead of the resonance tunnel diode. On the transmitting side of the terahertz wave transmitter 11, a first polarizing plate 13a as a transmitting side linearly polarizing means and a λ / 4 wave plate 14a as a transmitting side phase conversion means are provided. The linearly polarized light means functions as a phase conversion means for performing phase conversion on an electromagnetic wave. The polarization direction of the first polarizing plate 13a and the main axis direction of the λ / 4 wave plate 14a are provided so as to be different from each other by 45 °. The terahertz wave transmitter 11, the first polarizing plate 13a, and the λ / 4 wave plate 14a constitute an optical system arranged linearly, but are not necessarily limited to the case where they are arranged linearly. , An optical system that bends the terahertz wave may be further provided with a reflecting mirror or the like that reflects the terahertz wave L _1. Terahertz wave transmitter 11, outgoing optical system composed of the first polarizing plate 13a, and lambda / 4 wave plate 14a is a terahertz wave L _1p is linearly polarized light of the terahertz wave L _1, the plane of the steel structures 15 It is configured to be able to irradiate at a predetermined angle α.

The terahertz wave detector 12 as the terahertz wave detecting means includes, for example, a terahertz wave detecting element 12a made of an RTD, a hemispherical lens 12b, and a condenser lens 12c. The terahertz wave detector 12 is provided in the stress measuring device 1 in a state where the reflected waves of the terahertz wave (terahertz waves L ₂ , L _{2p) can be received by the terahertz wave detecting element 12a.} On the detection side of the terahertz wave detector 12, a second polarizing plate 13b as a detection-side polarizing means and a λ / 4 wave plate 14b as a detection-side phase conversion means are provided. The main axis direction of the λ / 4 wave plate 14b and the polarization direction of the second polarizing plate 13b are provided so as to be different from each other by 45 °.

The first polarizing plate 13a and the second polarizing plate 13b are provided so that the polarization directions differ from each other by 90 °. Here, the fact that the first polarizing plate 13a and the second polarizing plate 13b are provided so that the polarization directions differ by 90 ° means that the λ / 4 wavelength plates 14a and 14b are not provided and the compound refraction phenomenon occurs. The terahertz wave reflected on a predetermined surface does not pass through the second polarizing plate 13b after being linearly polarized by the first polarizing plate 13a in a state where no member is provided. Is to become. Further, due to the relationship between the first polarizing plate 13a and the second polarizing plate 13b described above, the λ / 4 wave plates 14a and 14b differ from each other by 90 ° in the main axis direction.

In the stress measuring device 1 configured as described above, the terahertz composed of at least a terahertz wave transmitter 11, a terahertz wave detector 12, a first polarizing plate 13a, a second polarizing plate 13b, and a λ / 4 wave plate 14a, 14b. The wave optical system is integrally tradable relative to the steel structure 15. As a result, the stress measuring device 1 is configured to be able to irradiate the _{terahertz wave L 1} and detect the reflected terahertz wave while scanning a predetermined range on the surface of the steel structure 15. As a scanning mechanism for scanning the terahertz wave optical system of the stress measuring device 1 relative to the surface of the steel structure 15, various conventionally known scanning mechanisms can be adopted, and further, scanning is performed manually. It is also possible to make it.

The analysis control unit 10 as an analysis means and a control means includes a signal amplification unit 10a, a bias generation unit 10b, a lock-in detection unit 10c, and an analysis processing unit 10d. The analysis control unit 10 performs various controls on the terahertz wave transmitter 11. Further, the analysis control unit 10 performs various processes on the terahertz wave signal detected by the terahertz wave detector 12. The signal amplification unit 10a amplifies the signal detected by the terahertz wave detector 12 and outputs it to the lock-in detection unit 10c as terahertz wave reception data. The bias generation unit 10b generates a bias voltage to bias the terahertz wave generating element 11a and the terahertz wave detecting element 12a, thereby changing the transmitted terahertz wave or the detected terahertz wave according to the bias voltage. The terahertz wave transmitted or detected by the terahertz wave generating element 11a and the terahertz wave detecting element 12a may be weak. In this embodiment, an example is shown in which the transmitted or detected terahertz wave is weak, and lock-in detection is used for the detection of the terahertz wave. At the time of lock-in detection, in the terahertz wave transmitter 11, the noise component of the terahertz wave detection signal is removed by using the reference signal modulated as the bias voltage of the terahertz wave generating element 11a. As a result, even if the transmitted or detected terahertz wave is weak, the detection can be performed with high accuracy. The analysis processing unit 10d as an analysis means includes a predetermined recording unit (not shown) for storing the detected terahertz wave reception data, and performs analysis processing on the terahertz wave reception data. Further, the storage unit (not shown) of the analysis processing unit 10d stores data of the dead load stress distribution when the above-mentioned plate girder 30 or the like is in a normal state.

(Measurement method of principal stress difference)
Next, the stress measurement by the stress measuring device 1 configured as described above will be described. As described above, the steel structure 15 is provided with the anticorrosion layer 15b on the steel surface 15as of the steel material 15a. The steel material 15a is a typical material generally used in structures such as bridges and pipes. The steel structure 15 includes, for example, a steel structure having a coating and covering, and a non-metal layer on the upper layer of the base, with a predetermined surface of a metal base such as aluminum (Al) or stainless steel (SUS) as a base. Can be various objects formed by.

The anticorrosion layer 15b functions as an anticorrosion layer on the steel surface 15as of the underlying steel material 15a, and also includes an adhesive and the like. The anticorrosion layer 15b is provided in close contact with the steel surface 15as of the steel material 15a. Therefore, when strain is generated in the steel material 15a to which the anticorrosion layer 15b is applied due to stress, most of the generated strain is propagated to the anticorrosion layer 15b, and strain similar to that of the steel material 15a is also generated in the anticorrosion layer 15b. Therefore, in the steel structure 15, it is inspected in advance by a conventionally known method, for example, a peeling test or the like, to check whether the anticorrosion layer 15b is in close contact with the steel surface 15as of the steel material 15a.

In steel structure 15 in a state where anticorrosion layer 15b is in close contact with the steel surface 15As, it emits the terahertz wave L ₁ toward the terahertz wave oscillator 11 of the stress measuring device 1 on the surface 15bs of the anticorrosion layer 15b. Specifically, the terahertz wave generated in the terahertz wave generating element 11a is emitted as a _{terahertz wave L 1} via the hemispherical lens 11b, the collimating lens 11c, and the objective lens 11d. Here, the transmitted terahertz wave L ₁ is typically a continuously transmitted terahertz continuous wave, but may be an intermittently transmitted terahertz pulse wave or tone burst wave.

_{The terahertz wave L 1} transmitted from the terahertz wave transmitter 11 is linearly polarized by the first polarizing plate 13a. The linearly polarized terahertz wave that has passed through the first polarizing plate 13a passes through the λ / 4 wave plate 14a and becomes circularly polarized light. The circularly polarized terahertz wave L _1p is incident on the anticorrosion layer 15b of the steel structure 15 at an incident angle of a predetermined angle α. As described above, the anticorrosion layer 15b has a strain similar to the strain of the lower steel material 15a. Therefore, the terahertz wave L _1p incident on the anticorrosion layer 15b is completely reflected by the steel surface 15as while birefringence corresponding to the strain occurs in the anticorrosion layer 15b. _{The terahertz wave L 2} completely reflected on the steel surface 15 as is emitted from the surface 15 bs while birefringence corresponding to the strain occurs in the anticorrosion layer 15 b.

_{The terahertz wave L 2} emitted from the surface 15 bs has a phase difference δ due to birefringence and is elliptically polarized light or circularly polarized light. It is polarized by the plate 13b. The polarized terahertz wave L _2p is detected by the terahertz wave detector 12. As a result, the terahertz wave detector 12 detects the ellipticity of the terahertz wave transmitted through the anticorrosion layer 15b and the intensity of the terahertz wave depending on the phase difference caused by the birefringence in the anticorrosion layer 15b.

_{As described above, the intensity of the terahertz wave L 2p} detected by the terahertz wave detector 12 is a physical quantity proportional to the principal stress difference (σ ₁ − σ _{2) of the anticorrosion layer 15b.} On the other hand, the photoelastic coefficient and the thickness of the anticorrosion layer 15b are measured in advance. Then, when the intensity of the terahertz wave L _{2p is detected, the principal stress difference (σ 1} − σ ₂ ) of the anticorrosion layer 15b can be derived from the intensity, photoelasticity coefficient, and thickness of the terahertz wave L _2p. As described above, the strain of the anticorrosion layer 15b conforms to the strain of the lower steel material 15a. _{Therefore, once} the principal stress difference (σ 1 − σ ₂ ) of the anticorrosion layer 15b is obtained, the principal strain difference (ε ₁ −ε ₂ ) of the anticorrosion layer 15b can be derived from this principal stress difference. Since the principal strain difference (ε _{1 −} ε ₂ ) of the anticorrosion layer 15b is equivalent to the principal strain difference of the steel surface 15as, the principal stress difference (σ ₁ ′ −) of the steel surface 15as is based on various parameters of the steel material 15a. σ ₂ ′) can be derived. That is, the principal stress difference (σ ₁ ′ − σ ₂ ′) of the steel material 15a can be derived from the derived principal stress difference (σ ₁ − σ _{2) of the anticorrosion layer 15b.} These derivations are executed by the analysis processing unit 10d of the analysis control unit 10 and the like.

Further, the above-mentioned scanning mechanism causes the above-mentioned terahertz wave optical system to scan a predetermined range along the surface of the steel structure 15. As a result, the terahertz wave intensity distribution according to the strain of the anticorrosion layer 15b is detected by the terahertz wave detector 12 in a predetermined range of the surface 15bs of the steel structure 15. The intensity distribution of the terahertz wave detected by the terahertz wave detector 12 is obtained as the distribution of the uniform color lines of the photoelastic stripes of the terahertz wave in the anticorrosion layer 15b. As described above, the distribution of the color matching lines of the photoelastic stripes in the obtained anticorrosion layer 15b is equivalent to the distribution of the color matching lines in the steel material 15a. That is, the anticorrosion layer 15b functions as a strain sensor for detecting _{the principal stress difference (σ 1} − σ _{2) of the strain of the steel material 15a.} By detecting the strain state in the anticorrosion layer 15b as the strain sensor using a terahertz wave, it is possible to measure the strain state of the steel material 15a.

(Measuring device in the direction of principal stress)
When the principal stress direction generated in the steel material 15a which is the above-mentioned structure is unknown, it is necessary to measure the principal stress direction in addition to the measurement of _{the principal stress difference (σ 1} − σ _2). FIG. 4 is a diagram showing another configuration of the stress measuring device according to one embodiment for measuring the principal stress direction.

As shown in FIG. 4, the stress measuring device 2 has a configuration in which the λ / 4 wave plates 14a and 14b are not provided in the stress measuring device 1. Further, the stress measuring device 2 is provided with a first polarizing plate 21a and a second polarizing plate 21b corresponding to the first polarizing plate 13a and the second polarizing plate 13b in the stress measuring device 1, respectively. The first polarizing plate 21a and the second polarizing plate 21b are each composed of disk-shaped polarizing plates having the same diameter, and have a disk gear shape in which external teeth having the same pitch are formed on the outer peripheral portion of the disk shape. Have.

In the stress measuring device 2, a polarizing plate synchronous rotation mechanism 22 is provided between the first polarizing plate 21a and the second polarizing plate 21b. The polarizing plate synchronous rotation mechanism 22 includes a turning head 22a, a gear box 22b, and a polarizing plate synchronous rotation gear 22c. The swivel head 22a is connected to the polarizing plate synchronous rotation gear 22c via a conventionally known gear box 22b. By rotating the swivel head 22a around the rotation shaft O, the polarizing plate synchronous rotation gear 22c is rotated via a plurality of gears in the gearbox 22b. External teeth that mesh with the external teeth of the outer peripheral portions of the first polarizing plate 21a and the second polarizing plate 21b are formed on the outer peripheral portion of the polarizing plate synchronous rotary gear 22c. By engaging the external teeth of the polarizing plate synchronous rotation gear 22c with the external teeth of the first polarizing plate 21a and the second polarizing plate 21b, the first polarizing plate 21a and the first polarizing plate 21a and the first polarizing plate 21a and the first polarizing plate 21a and the first 2 The polarizing plate 21b rotates in the same rotation direction. Here, the outer diameter of the first polarizing plate 21a and the outer diameter of the second polarizing plate 21b are the same as each other. Therefore, when the turning head 22a is rotated to rotate the polarizing plate synchronous rotation gear 22c, the first polarizing plate 21a and the second polarizing plate 21b differ in the polarization direction by a predetermined polarization direction, here, by an angle of 90 °. Rotate in the same direction of rotation while maintaining the state of rotation. Other configurations are the same as those of the stress measuring device 1.

(Measuring method in the direction of principal stress)
Next, a method of measuring the main stress direction using the above-mentioned stress measuring device 2 will be described. That is, as shown in FIG. 4, the terahertz wave L ₁ emitted from the terahertz wave oscillator 11, after being polarized into linearly polarized light passes through the first polarizer 21a, enters the anticorrosion layer 15b of steel structures 15 Will be done. _{The terahertz wave L 1p} incident on the anticorrosion layer 15b is completely reflected by the steel surface 15as of the steel material 15a and is emitted through the anticorrosion layer 15b. In this state, the polarizing plate synchronous rotation gear 22c is rotated to rotate the first polarizing plate 21a and the second polarizing plate 21b while maintaining a state in which the polarization directions differ from each other by 90 °.

As the first polarizing plate 21a and the second polarizing plate 21b rotate, the polarization direction of the first polarizing plate 21a, that is, the polarization direction of the linearly polarized terahertz wave L _1p and the principal stress direction of the anticorrosion layer 15b coincide with each other. A condition arises. In this state, the terahertz wave L _1p passes through the anticorrosion layer 15b without changing the linearly polarized light. The terahertz wave L _1p is further reflected by the steel surface 15as and passes through the anticorrosion layer 15b. _{The terahertz wave L 2} transmitted through the anticorrosion layer 15b is linearly polarized light along the polarization direction of the first polarizing plate 21a. Therefore, the terahertz wave L ₂ hardly transmits the second polarizing plate 21b in the polarization direction different from the polarization direction of the first polarizing plate 21a by 90 °, and the intensity of the _{terahertz wave L 2p transmitted through the second polarizing plate 21b.} Becomes minimal. In this case, when the terahertz wave L _2p transmitted through the second polarizing plate 21b is observed, a dark line called an isobaric line in which the intensity of the terahertz wave L _{2p is minimized appears in the anticorrosion layer 15b.}

When the polarization direction of the first polarizing plate 21a and the principal stress direction of the anticorrosion layer 15b coincide with each other, the terahertz wave L ₂ hardly passes through the second polarizing plate 21b. That is, in the X-axis and Y-axis shown in FIG. 4 and the second polarizing plate 21b, when the terahertz wave L _2p transmitted through the second polarizing plate 21b becomes extremely small, the polarization direction of the second polarizing plate 21b and the polarization direction of the second polarizing plate 21b. The direction orthogonal to the polarization direction of the second polarizing plate 21b is the principal stress direction. Thereby, the main stress direction of the anticorrosion layer 15b can be derived.

On the other hand, when the polarization direction and the principal stress direction of the first polarizing plate 21a do not match, the terahertz wave L _1p incident on the anticorrosion layer 15b causes a phase difference due to the birefringence generated in the anticorrosion layer 15b. Therefore, the terahertz wave L ₂ emitted from the anticorrosion layer 15b is elliptically polarized light or circularly polarized light. The elliptically polarized terahertz wave L ₂ passes through the second polarizing plate 21b and is polarized into linearly polarized light. The linearly polarized terahertz wave L _2p is detected by the terahertz wave detector 12. The intensity of the terahertz wave L _2p in this state is larger than the intensity of _{the terahertz wave L 2p} when the polarization direction of the first polarizing plate 21a described above and the principal stress direction of the anticorrosion layer 15b coincide with each other.

Based on the above changes in the state, _{the intensity of the terahertz wave L 2p} detected by the terahertz wave detector 12 alternates between maximum and minimum while the first polarizing plate 21a and the second polarizing plate 21b rotate by 90 °. Expressed in. _{As a result, when the principal stress direction is derived, the principal stress direction of the maximum principal stress component σ 1} can be derived based on the shape of the steel material 15a, the operating conditions of the external force, and the like by a conventionally known method.

Further, by the above-mentioned scanning mechanism (not shown), a second terahertz wave optical system in which at least a terahertz wave transmitter 11, a terahertz wave detector 12, a first polarizing plate 21a, and a second polarizing plate 21b are integrated is provided. A predetermined range is scanned along the surface of the steel structure 15. As a result, the terahertz wave detector 12 detects the intensity distribution of _{the terahertz wave L 2p} along the principal stress direction of the anticorrosion layer 15b in a predetermined range of the steel structure 15. _{The intensity distribution of the terahertz wave L 2p} detected by the terahertz wave detector 12 is obtained as an isobaric line of the terahertz wave in the anticorrosion layer 15b. Since the anticorrosion layer 15b is in close contact with the steel surface 15as of the steel material 15a, the isotonic lines of the obtained photoelastic stripes are the isotonic lines of the steel material 15a. That is, the anticorrosion layer 15b functions as a strain sensor for detecting the main stress direction of the strain of the steel material 15a.

Based on the above method, the principal stress difference (σ ₁ − σ ₂ ) and the principal stress direction are derived. If necessary, the principal stress components σ ₁ and σ ₂ are separated from each other _{based on the principal stress difference (σ 1} − σ ₂ ) derived by the conventionally known shear stress difference integration method and the principal stress direction. It can be derived. These derivations are executed by the analysis processing unit 10d of the analysis control unit 10 and the like. Once the photoelastic parameters such as the principal stress components σ ₁ and σ ₂ and the principal stress direction in the anticorrosion layer 15b are known, the strain of the anticorrosion layer 15b can be derived based on the elastic constant of the anticorrosion layer 15b. As described above, the anticorrosion layer 15b and the steel material 15a constituting the underlying structure are usually in close contact with each other, and the strain of the anticorrosion layer 15b conforms to the strain of the steel material 15a. Therefore, the stress generated in the steel material 15a can be derived based on the strain of the steel material 15a obtained as the strain of the anticorrosion layer 15b and the elastic modulus of the steel material 15a.

That is, the stress measuring devices 1 and 2 can measure the strain state of the steel material 15a by detecting the strain state of the anticorrosion layer 15b serving as the strain sensor using the terahertz wave. As a result, when the principal stress components σ ₁ and σ ₂ and the principal stress direction are derived, the stress state of the steel structure 15, that is, the stress state of the steel material 15a, which is the object to be measured, can be measured. In other words, by deriving the stress state of the anticorrosion layer 15b by the terahertz wave photoelastic method, the stress state of the lower steel material 15a can be finally derived, and the stress distribution generated in the steel structure 15 can be measured. It will be possible.

(Modification example)
Next, a modified example of the method for measuring the principal stress difference and the method for measuring the principal stress direction according to the above-described embodiment will be described. That is, in the stress measuring device 2 shown in FIG. 4, the first polarizing plate 21a and the second polarizing plate 21b rotate in the same rotation direction while maintaining a state in which the polarization directions differ by 90 °. In this case, the detection intensity at a position in an arbitrary polarization direction and the position where the first polarizing plate 21a and the second polarizing plate 21b are rotated by 45 ° while maintaining a state in which the polarization directions differ by 90 ° from that position. detects the intensity of the terahertz wave L _2p, by adding the intensities of the two detected terahertz waves L _2p, it is also possible to determine the principal stress difference (σ ₁ -σ _2).

More specifically, the intensity I ₁ of the light detected in an arbitrary polarization direction is the angle φ between the phase difference δ caused by birefringence and the principal stress direction and the polarization direction, as shown in the following equation (2). Depends on.
I ₁ = A ² sin ² 2φ ・ sin ² (δ / 2)… (2)
Note that A is the amplitude of the incident light.

Further, from the position where the light intensity I ₁ is detected, the first polarizing plate 21a and the second polarizing plate 21b are detected at a position rotated by 45 ° while maintaining a state in which the polarization directions differ from each other by 90 °. _{The intensity I 2} of the light to be formed is as shown in Eq. (3).
I ₂ = A ² sin ² 2 (φ + π / 4) ・ sin ² (δ / 2)… (3)

When the light intensities I ₁ and I ₂ detected as described above are combined, the combined light intensity I is the angle φ between the principal stress direction and the polarization direction as shown in the following equation (4). Does not depend on.
I = I ₁ + I ₂ = A ² sin ² (δ / 2)… (4)
This means that in the photoelastic method, the same result as when circularly polarized light is used can be obtained. As a result, the stress measuring device 2 can derive both the principal stress direction and the principal stress difference (σ ₁ − σ _{2) of the anticorrosion layer 15b.} Other configurations are the same as those of the above-described embodiment.

(Soundness evaluation method)
Next, the stress distribution of the steel structure 15 composed of the plate girder 30 measured as described above becomes the dead load stress distribution of the plate girder 30. Therefore, a method for evaluating the soundness of the bearings 31 and 32 that support the plate girder 30 based on the dead load stress distribution of the plate girder 30 measured as described above will be described. FIG. 5 is a flowchart for explaining an example of a soundness evaluation method according to an embodiment. The flowchart shown in FIG. 5 shows a process from evaluation of soundness in a steel bridge to narrowing down of repair targets, and is executed by, for example, an analysis processing unit 10d in the analysis control unit 10.

As shown in FIG. 5, first, in step ST1, the dead load stress distribution in the plate girder 30 of the bridge is measured by using the stress measuring devices 1 and 2 described above. Next, in step ST2, the analysis processing unit 10d has the data of the dead load stress distribution (hereinafter referred to as the design stress distribution) stored in the storage unit in the normal state and the dead load stress distribution measured in step ST1. (Hereinafter, the measured stress distribution) is compared with the data. After that, the process proceeds to step ST3.

In step ST3, the analysis processing unit 10d determines whether or not there is a discrepancy between the design stress distribution and the measured stress distribution. When the analysis processing unit 10d determines that there is no discrepancy between the design stress distribution and the measured stress distribution and they are substantially in agreement with each other (step ST3: No), the process proceeds to step ST10 and the current stress of the plate girder 30 is reached. It is determined that the distribution is in the normal state and the states of the bearings 31 and 32 are also in the normal state, and the soundness diagnosis process is terminated. On the other hand, when the analysis processing unit 10d determines in step ST3 that there is a discrepancy between the design stress distribution and the measured stress distribution (step ST3: Yes), the process proceeds to step ST4.

In step ST4, the analysis processing unit 10d derives by calculating the stress distribution, assuming the conditions of the bearings 31 and 32. This is because if there is a discrepancy between the design stress distribution and the measured stress distribution, it is considered that some abnormality has occurred in the plate girder 30 of the bridge. In this respect, it is extremely unlikely that the weight of the plate girder 30 or the floor slab will change significantly over time. Therefore, it is considered that the cause of the discrepancy between the design stress distribution and the measured stress distribution is due to the abnormality of the functions of the supporting bearings 31 and 32. Here, an example of a method of changing the installation conditions of the bearings 31 and 32 will be described.

In one embodiment, the bearing 31 that supports one end of the plate girder 30 comprises, for example, a pin-roller type bearing and is configured to be rotatable and horizontally movable. The bearing 32 that supports the other end of the plate girder 30 is, for example, a pin / fixed bearing, and is configured to be rotatable and fixed. Therefore, the analysis processing unit 10d changes the data of the degree of freedom of rotation of the bearing 31 to be reduced by X% with respect to the design specification, and the data of the degree of freedom of horizontal movement to be reduced by Y% with respect to the design specification. At the same time, the analysis processing unit 10d changes the data of the degree of freedom of rotation of the bearing 32 so as to be reduced by Z% with respect to the design specifications. The degree of freedom in the bearings 31 and 32 is reduced with respect to the design specifications in order to reproduce the state in which the functions of the bearings 31 and 32 are reduced. After that, the analysis processing unit 10d derives the dead load stress distribution generated in the plate girder 30 based on the data in which the degrees of freedom in the bearings 31 and 32 are changed. The data of the dead load stress distribution (hereinafter referred to as the calculated stress distribution) derived by the analysis processing unit 10d by calculation is stored in the storage unit of the analysis processing unit 10d.

After that, the process proceeds to step ST5, and the analysis processing unit 10d compares the calculated stress distribution data with the measured stress distribution data. After that, the process proceeds to step ST6. In step ST6, the analysis processing unit 10d determines whether or not there is a discrepancy between the calculated stress distribution and the measured stress distribution. When the analysis processing unit 10d determines that there is a discrepancy between the calculated stress distribution and the measured stress distribution (step ST6: Yes), the process proceeds to step ST7.

In step ST7, the analysis processing unit 10d changes the conditions in the bearings 31 and 32. That is, the analysis processing unit 10d changes the data of the degrees of freedom in the bearings 31 and 32 to the data different from the data of the degrees of freedom changed in step ST4. Specifically, in the bearing 31, at least one of X% regarding the degree of freedom of rotation, Y% regarding the degree of freedom of horizontal movement, and Z% regarding the degree of freedom of rotation in the bearing 32 is changed to be free. Change the degrees of freedom data. After that, the process returns to step ST4. The processes of steps ST4 to ST7 are repeatedly executed until the analysis processing unit 10d determines in step ST6 that there is no discrepancy between the calculated stress distribution and the measured stress distribution.

When the analysis processing unit 10d determines in step ST6 that there is no discrepancy between the calculated stress distribution and the measured stress distribution and they are substantially in agreement with each other (step ST6: No), the process proceeds to step ST8. In step ST8, the analysis processing unit 10d determines that the actual states of the bearings 31 and 32 match the states of the bearings 31 and 32 based on the data assumed in step ST4 or ST7. That is, the analysis processing unit 10d determines that the state of the degrees of freedom of the bearings 31 and 32 assumed in the calculated stress distribution is the state of the degrees of freedom in the abnormal state of the actual bearings 31 and 32.

After that, when the process proceeds to step ST9, the analysis processing unit 10d derives the bearings 31 and 32 in which the abnormality has occurred and the defective events in the bearings 31 and 32 based on the states of the bearings 31 and 32 determined in step ST8. .. As a result, the analysis processing unit 10d determines the bearings 31 and 32 to be repaired and the defective event. With the above, the soundness diagnosis process is completed.

(Structure repair processing method)
After that, based on the bearings 31, 32 to be repaired and the defective event derived by the above-mentioned soundness diagnosis process, the steel structure 15 made of the plate girder 30 is repaired while confirming the repair state. .. FIG. 6 is a flowchart showing an example of a structure repair processing method according to an embodiment.

As shown in FIG. 6, first, in step ST11, a repair worker or the like performs repair based on the above-mentioned defective event for the bearings 31 and 32 to be repaired. After that, in step ST12, a predetermined manager or the analysis processing unit 10d (hereinafter collectively referred to as a manager) determines whether or not it is necessary to confirm the effect of the repair. When the administrator determines that it is not necessary to confirm the effect of the repair (step ST12: No), the process proceeds to step ST16, it is determined that the repair is completed, and the repair process is terminated.

On the other hand, when the administrator determines in step ST12 that it is necessary to confirm the effect of the repair (step ST12: Yes), steps ST13, ST14, and ST15 are sequentially executed. In steps ST13 and ST14, the dead load stress distribution in the steel structure 15 is measured again using stress measuring devices 1, 2 and the like in the same manner as in steps ST1 and ST2 in the above-mentioned soundness diagnosis process, and then the design is performed. Compare the stress distribution with the measured stress distribution. In step ST15, in the same manner as in step ST3 described above, the analysis processing unit 10d determines whether or not there is a discrepancy between the design stress distribution and the measured stress distribution. When the analysis processing unit 10d determines in step ST15 that there is a discrepancy between the design stress distribution and the measured stress distribution (step ST15: Yes), the process proceeds to step ST17.

In step ST17, the administrator adjusts the content of the repair work based on the comparison between the design stress distribution and the measured stress distribution performed in step ST14, shifts to step ST18, and performs additional repair work. .. After that, the process returns to step ST12. The processes of steps ST12 to ST15, ST17, and ST18 are repeatedly executed until it is determined in step ST15 that there is no discrepancy between the design stress distribution and the measured stress distribution and they are substantially the same (step ST15: No). ..

When the analysis processing unit 10d determines in step ST15 that there is no discrepancy between the design stress distribution and the measured stress distribution and they are substantially in agreement with each other (step ST15: No), the process proceeds to step ST16. In step ST16, since the dead load stress distribution of the steel structure 15 after repair is in the normal state, the states of the bearings 31 and 32 are also in the normal state. Therefore, it is determined that the repair is completed, and the repair process is performed. To finish. As described above, the repair process according to the embodiment is completed.

According to the soundness evaluation method according to the embodiment described above, it is determined whether or not there is a discrepancy between the design stress distribution and the measured stress distribution, and when it is determined that there is a discrepancy, the support 31 and 32 By changing the installation conditions to derive the calculated stress distribution and repeatedly assuming the installation conditions of the supports 31 and 32 until there is no discrepancy between the calculated stress distribution and the measured stress distribution and they are in good agreement with each other. It is possible to quantitatively measure and evaluate the soundness of a steel structure 15 such as 30.

Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-mentioned one embodiment, and various modifications based on the technical idea of the present invention are possible. For example, the configurations of the stress measuring devices 1 and 2 given in the above embodiment are merely examples, and the principal stress difference and the principal stress direction of the non-metal layer in close contact with the surface of the structure are measured using a terahertz wave. If possible, a device having a different configuration may be used if necessary. Further, the present invention is not limited by the description and drawings which form a part of the disclosure of the present invention according to the above-described embodiment.

For example, in the above-described embodiment, the soundness of the bearings 31 and 32 such as the plate girder 30 of the bridge is diagnosed, but the structures to be diagnosed for the soundness are not necessarily the plate girder 30 and the bearings 31 and 32. Not limited to. Specifically, it is also possible to make a structure such as a pipeline a target for soundness diagnosis. In pipelines and the like, support portions designed to move horizontally in the pipe axis direction and expansion joints installed to absorb thermal stress and the like are provided. If these supports and expansion joints are not functioning properly, the stress distribution will change throughout the pipeline. In this case, by measuring the change in the stress distribution and comparing it with the stress distribution by design by the soundness diagnosis process according to the above-described embodiment, the repaired part and the function to be repaired can be specified, and the optimum repair is performed. Will be possible. Further, the structure may be a crane such as a gantry crane (bridge crane), a plant pipe, or the like, in addition to the bridge girder 30 and the pipeline, and can be various structures. be.

Further, in the above-described embodiment, the degree of freedom of bearing is changed as three parameters, but the parameter is not necessarily limited to the three parameters and is one or more changeable parameters. Any parameter can be set as long as it causes a change in the stress distribution in the steel structure 15.

For example, in the above-described embodiment, the terahertz wave photoelastic method is used as a method for measuring the dead load stress distribution in the plate girder 30, but the method is not necessarily limited to the terahertz wave photoelastic method. That is, in addition to the terahertz wave photoelastic method, various non-destructive stress measurement methods such as X-ray stress measurement method, magnetic strain method, Parchausen noise method, and sound elasticity method, stress release method by partial cutting, blind hole method, etc. It is also possible to adopt a semi-non-destructive measurement method using a strain gauge. Further, the cause of the stress is not limited to the dead load, and the stress generated when a heavy object is placed by a loading test or the like may be measured.

For example, in the above-described embodiment, the terahertz wave is spot-irradiated to the steel structure 15 and is spot-reflected by the steel surface 15as of the steel material 15a, but is not necessarily spot-irradiated and reflected. Not limited to. For example, instead of the terahertz wave transmitter 11, a terahertz wave light source capable of emitting a terahertz wave in a planar manner is used, and instead of the terahertz wave detector 12, a terahertz wave L _2p can be detected as a planar distribution. It is also possible to use a wave detection array or the like. According to this configuration, the stress distribution of the steel material 15a in the steel structure 15 as the measurement object, that is, the principal stress difference (σ ₁ − σ ₂ ) and the principal stress direction can be derived and evaluated. ..

For example, in the above-described embodiment, as a mechanism for rotating the first polarizing plate 21a and the second polarizing plate 21b in the stress measuring device 2 while maintaining a state in which the polarization directions differ from each other by 90 °. Although the polarizing plate synchronous rotation mechanism 22 is used, the mechanism is not necessarily limited to this mechanism. If it is possible to rotate the first polarizing plate 21a and the second polarizing plate 21b while maintaining a state in which the polarization directions differ from each other by 90 °, it is possible to adopt various conventionally known rotation mechanisms. be.

For example, in the above-described embodiment, in the stress measuring devices 1 and 2, the optical system for emitting the terahertz wave toward the steel structure 15 and the terahertz wave reflected by the steel surface 15as are detected. Although the optical system is configured to be non-coaxial with a different optical axis, it is not necessarily limited to non-coaxial. Specifically, by using a half mirror or the like, it is possible to configure the optical system that emits the terahertz wave and the optical system that detects the reflected terahertz wave to be coaxial in which the optical axes overlap.

Further, in the above-described embodiment, the main stress direction generated in the steel material 15a of the steel structure 15 may be clear depending on the shape, design, and the like. In this case, based on the principal stress difference (σ ₁ − σ ₂ ) obtained as described above and the principal stress direction that is clear depending on the shape, design, etc., the principal stress is applied by a conventionally known shear stress difference integration method. It is possible to obtain the components σ ₁ and σ _{2 separately from each other.} These derivations are executed by the analysis processing unit 10d of the analysis control unit 10 and the like. By deriving the principal stress components σ ₁ and σ ₂ and the principal stress direction, it becomes possible to measure the state of the steel structure 15, that is, the load stress distribution of the plate girder 30 of the bridge, which is the object to be measured, in detail. .. Further, when the stress generated in the steel material 15a is a uniaxial stress field or a stress field close to the uniaxial stress field, the principal stress difference (σ ₁ − σ ₂ ) should be regarded as almost the maximum principal stress component σ _1. Can be done. In this case, the derivation process for separating the principal stress components σ ₁ and σ _{2 from the principal stress difference (σ 1} − σ ₂ ) can be omitted by the shear stress difference integration method. That is, it is possible to measure the dead load stress distribution in the plate girder 30 in detail only by measuring the principal stress difference (σ ₁ − σ _2).

1,2 Stress measuring device 10 Analysis control unit 10a Signal amplification unit 10b Bias generation unit 10c Lock-in detection unit 10d Analysis processing unit 11 Terahertz wave transmitter 11a Terahertz wave generator 11b, 12b Hemispherical lens 11c Collimated lens 11d Objective lens 12 Terahertz Wave detector 12a Terahertz wave detection element 12c Condensing lens 13a, 21a First polarizing plate 13b, 21b Second polarizing plate 14a, 14b λ / 4 wave plate 15 Steel structure 15a Steel material 15as Steel surface 15b Anticorrosion layer 15bs Surface 22 Polarization Plate synchronous rotation mechanism 22a Swivel head 22b Gear box 22c Polarizer synchronous rotation gear 30 Plate girder 30a Web 30b Flange 31, 32 Support 33a Compressive stress 33b Tensile stress

Claims (8)

Based Accordingly resulting stress distribution in the dead load of the structure to dead load stress distribution measurably the structure measured by configured stress distribution measuring device to evaluate the soundness of the structure by analysis means It is a soundness evaluation method,
The analysis means is
The dead load stress distribution based on the design of the structure is compared with the dead load stress distribution of the structure measured by the stress distribution measuring device.
A soundness evaluation method characterized in that the soundness of the structure is evaluated by the discrepancy between the dead load stress distribution based on the design and the measured dead load stress distribution. The analysis means is configured to be able to derive the stress distribution generated in the structure under the assumed installation conditions when the installation conditions of the constituent members that cause the stress distribution in the structure to change are assumed. ,
When the derived stress distribution substantially matches the measured stress distribution, the analysis means determines that the installation condition of the constituent member in the measured structure is the assumed installation condition. The soundness evaluation method according to claim 1, wherein the soundness is evaluated. The structure is composed of a non-metal layer provided on an upper layer of a metal substrate.
The stress distribution measuring device
A terahertz wave transmitting means capable of irradiating a predetermined position on the surface of the structure with a terahertz wave and scanning the surface of the structure.
Claim 1 or 2 is characterized by comprising a terahertz wave detecting means capable of detecting a terahertz wave reflected at a predetermined position of the structure and scanning the surface of the structure. The soundness evaluation method described in. The stress in the non-metal layer is detected by irradiating the non-metal layer with the tera-hertz wave emitted from the tera-hertz wave transmitting means and detecting the intensity of the tera-hertz wave transmitted through the non-metal layer by the tera-hertz wave detecting means. The soundness evaluation method according to claim 3, wherein the stress distribution in the structure is measured by measuring the state and using the non-metal layer as a strain detecting means in the photoelastic method. The soundness of the structure is based on the stress distribution of the structure measured by a stress distribution measuring device configured to be able to measure the stress distribution generated in the structure provided with the non-metal layer on the upper layer of the metal substrate. Is a soundness evaluation method that evaluates by analysis means.
The stress distribution measuring device is configured to be capable of irradiating a predetermined position on the surface of the structure with a terahertz wave, and also has a terahertz wave transmitting means capable of scanning the surface of the structure and the predetermined position of the structure. A terahertz wave detecting means capable of scanning the surface of the structure and a transmitting side straight line provided on the emitting side of the terahertz wave in the terahertz wave transmitting means while being configured to be able to detect the terahertz wave reflected in the above. The detection side linear polarization means provided on the detection side of the polarization means and the terahertz wave detection means so that the polarization direction differs from the polarization direction of the transmission side linear polarization means by 90 °, and the emission side of the terahertz wave transmission means. The transmitting side phase conversion means for giving a phase difference so that the linearly polarized terahertz wave transmitted through the transmitting side linear polarizing means becomes circularly polarized, and the incident side of the terahertz wave to the detecting side linear polarizing means. A detection side phase conversion means provided on the side and giving a phase difference to the terahertz wave is provided.
It is configured so that the principal stress difference acting on the structure can be measured, and the stress of the structure is stressed by using the principal stress difference of the structure obtained from the detection intensity of the terahertz wave detected by the terahertz wave detecting means. It is configured so that the distribution can be derived,
The analysis means is
The stress distribution based on the design in the structure is compared with the stress distribution of the structure measured by the stress distribution measuring device.
The soundness of the structure is evaluated by the difference between the stress distribution based on the design and the measured stress distribution.
A soundness evaluation method characterized by this. The structure is measured by an analysis means based on the stress distribution of the structure measured by a stress distribution measuring device configured to be able to measure the stress distribution generated in the structure provided with the non-metal layer on the upper layer of the metal substrate. It is a soundness evaluation method for evaluating the soundness of
The stress distribution measuring device is configured to be able to irradiate a predetermined position on the surface of the structure with a terahertz wave, and also has a terahertz wave transmitting means capable of scanning the surface of the structure and the predetermined position of the structure. The terahertz wave detecting means capable of scanning the surface of the structure and the transmitting side straight line provided on the emitting side of the terahertz wave in the terahertz wave transmitting means while being configured to be able to detect the terahertz wave reflected in the above. A polarization means and a detection-side linear polarization means provided on the detection side of the terahertz wave detection means so that the polarization direction differs from the polarization direction of the transmission-side linear polarization means by 90 ° are provided.
The transmitting side linearly polarizing means and the detecting side linearly polarizing means are configured to be rotatable while maintaining a state in which the polarization direction of the transmitting side linearly polarizing means and the polarization direction of the detecting side linearly polarizing means are different by 90 °. ,
The detection intensity of the terahertz wave at an arbitrary position obtained by rotating the transmitting side linearly polarizing means and the detecting side linearly polarizing means while maintaining a state in which the polarization directions differ by 90 °, and the polarization direction of the transmitting side linearly polarizing means. And the detection intensity at the position further rotated by 45 ° while maintaining the state where the polarization direction of the detection side linearly polarizing means is different by 90 °, and the principal stress difference is measured by adding.
Along with the rotation of the transmitting side linear polarizing means and the detecting side linear polarizing means, the principal stress direction acting on the structure is measured based on the direction in which the detection intensity of the terahertz wave detected by the terahertz wave detecting means is minimized. , The stress distribution of the structure is derived based on the measured principal stress difference of the structure and the principal stress direction of the structure.
The analysis means is
The stress distribution based on the design in the structure is compared with the stress distribution of the structure measured by the stress distribution measuring device.
The soundness of the structure is evaluated by the difference between the stress distribution based on the design and the measured stress distribution.
A soundness evaluation method characterized by this . The analysis means is configured to be able to derive the stress distribution generated in the structure under the assumed installation conditions when the installation conditions of the constituent members that cause the stress distribution in the structure to change are assumed. ,
When the derived stress distribution substantially matches the measured stress distribution, the analysis means determines that the installation condition of the constituent member in the measured structure is the assumed installation condition.
The soundness evaluation method according to claim 5 or 6, characterized in that. The first aspect of claim 2, wherein the structure is a bridge having at least one bearing as the constituent member, claims 3 and 4 citing claim 2 , and claim 7 . Soundness assessment method.

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