Determination method and determination device

Abstract

To provide a determination method and a determination device capable of determining whether a candidate date for photographing an infrared thermal image is suitable for photographing in a water retention inspection to detect water retention inside a steel deck. [Solution] A determination method including the steps of: prior to a water retention inspection to detect water retention W inside a steel deck plate (91) based on an infrared thermal image taken of the steel deck plate (91), setting optimal day conditions suitable for taking the infrared thermal image; calculating an expected value, which is the probability that the optimal day conditions will be satisfied on one candidate day for taking the image, based on an equation including at least three or more shooting conditions as variables; and determining that the candidate day for taking the image is suitable for taking the infrared thermal image if the expected value is equal to or greater than a predetermined determination threshold.

Description

[Technical Field]

[0001] The present invention relates to a method and device for determining whether a proposed date for taking infrared thermal images is suitable for taking the images prior to a water retention inspection to detect water retention inside a steel deck plate based on infrared thermal images taken of the steel deck plate. [Background technology]

[0002] As shown in Figure 1(a), a steel deck 91 used in bridges is a deck in which a flat deck plate 92 made of steel is stiffened from the backside with vertical ribs 94 and horizontal ribs 95. The vertical ribs 94 in the illustrated example are trough ribs 941 (closed cross-section ribs) with a cross-sectional shape such as a substantially U-shape, V-shape, or arc shape, and are welded to the underside of the deck plate 92.

[0003] In the steel deck 91 of bridges that have a high volume of large vehicle traffic and have been in service for a long time, deck-penetrating cracks 97 can occur due to the effects of fatigue. A deck-penetrating crack 97 is a crack that starts at the weld root 96 between the deck plate 92 and the trough rib 941 and penetrates the deck plate 92. Because deck-penetrating cracks 97 can also cause damage such as potholes in the pavement 93 laid on top of the deck plate 92, early detection is required.

[0004] However, because the deck-penetrating crack 97 is located below the pavement 93, it cannot be detected by visual inspection alone. Therefore, a method has been proposed in the past to detect damage to the deck plate 92 from the outside of the steel deck using infrared thermal images.

[0005] One inspection method using infrared thermal images focuses on the correlation between specific components and water retention, and detects damage to components by detecting water retention inside the deck slab. The upper end of the trough rib 941 of the steel deck slab 91 is welded to the underside of the deck plate 92, and the opening at the end in the bridge axis direction is sealed by a sealing diaphragm (not shown). Therefore, the internal space of the trough rib 941 is normally kept airtight. However, if a deck-penetrating crack 97 progresses as shown in Figure 1(b), rainwater from the road surface will infiltrate the internal space of the trough rib 941 along the deck-penetrating crack 97, causing water retention W (Figure 1(a)).

[0006] Patent Document 1 discloses that while driving on the pavement 3, infrared thermal images of the surface of the pavement 3 are taken to detect temperature differences on the road surface, thereby detecting water accumulation inside the deck slab, and the location of the detected water accumulation is investigated to detect through-cracks in the deck plate. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5249852 Summary of the Invention [Problem to be solved by the invention]

[0008] In a water retention inspection using infrared thermal images, whether or not an infrared thermal image that easily determines the presence or absence of water retention W can be captured is affected by various conditions, such as the weather on the day of capture, the time of day of capture, the position of the trough rib 941, and the amount of water retention W. For this reason, it is difficult to accurately predict the day on which an appropriate infrared thermal image can be reliably captured. Patent Document 1 does not describe determining whether a day is suitable for capturing an infrared thermal image when deciding the day to capture the infrared thermal image.

[0009] The object of the present invention is to solve the above-mentioned conventional problems and to provide a determination method and a determination device that can determine whether a candidate date for taking infrared thermal images is suitable for taking them in a water retention inspection to detect water retention inside a steel deck. [Means for solving the problem]

[0010] In order to solve the above problem, the method includes the steps of: prior to a water retention inspection to detect water retention inside a steel deck plate based on an infrared thermal image of the steel deck plate; setting optimal day conditions suitable for taking the infrared thermal image; calculating an expected value, which is the probability that the optimal day conditions will be satisfied on a candidate day for taking the infrared thermal image, based on an equation including at least three or more shooting conditions as variables; and determining whether the calculated expected value is equal to or greater than a predetermined threshold value, thereby determining whether the candidate day for taking the infrared thermal image is suitable.

[0011] Furthermore, the step of calculating the expected value includes the steps of extracting three shooting conditions a, b, and c that affect whether the optimum day conditions are met, categorizing the shooting conditions, calculating the occurrence rate p of days on which the optimum day conditions are met for each type of shooting condition, and weighting the occurrence rate p by multiplying it by a weight w calculated using the following formula 1, and it is preferable that the expected value S is calculated based on the following formula 2.

number

number

[0012] It is also preferable to set the determination threshold value based on the expected value S calculated from the photographing conditions on a non-satisfied day in the past when the optimum day conditions were not satisfied.

[0013] It is also preferable that the photographing conditions include at least the diurnal temperature range and general weather conditions.

[0014] In addition, the judgment device is equipped with a setting unit that sets optimal day conditions suitable for taking infrared thermal images prior to a water retention inspection to detect water retention inside the steel deck based on infrared thermal images taken of the steel deck, a calculation unit that calculates an expected value, which is the probability that the optimal day conditions will be satisfied on one candidate day for taking the infrared thermal images, based on an equation that includes at least three or more shooting conditions as variables, and a judgment unit that determines whether the calculated expected value is greater than or equal to a predetermined threshold value, thereby determining whether the candidate day for taking the infrared thermal images is suitable. [Effects of the Invention]

[0015] The present invention makes it possible to provide a determination method and device that can determine whether a candidate date for taking infrared thermal images is suitable for taking them in a water retention inspection to detect water retention inside a steel deck. [Brief explanation of the drawings]

[0016] [Figure 1] (a) is a schematic diagram showing the state in which water has stagnated inside the trough rib of a steel deck where a deck-penetrating crack has occurred, and (b) is a schematic diagram showing rainwater seeping into the inside of the trough rib along the deck-penetrating crack. [Figure 2] FIG. 1 illustrates an example of the configuration of a determination system according to an embodiment. [Figure 3] FIG. 10 is a flowchart showing the process flow of a determination method according to an embodiment. [Figure 4] This is a schematic diagram of a steel deck box girder bridge from which temperature data is collected. [Figure 5] This is a schematic diagram of a steel deck box girder bridge from which temperature data is collected. [Figure 6] 10A is a diagram showing the temperature changes in a day in a U-rib with and without water retention, and FIG. 10B is a diagram showing the number of times a negative temperature difference occurred. [Figure 7] (a) is a diagram showing the measurement results of the temperature of a U-rib without stagnant water, and (b) is a diagram showing the difference between the upper and lower limit values ​​of the temperature of the U-rib shown in (a). [Figure 8] FIG. 10 is a diagram showing the relationship between the temperature of the U-rib and the amount of retained water. [Figure 9] FIG. 10 is a diagram showing the trade-off relationship regarding setting of optimal day conditions. [Figure 10] FIG. 10 is a Venn diagram showing the relationship between a plurality of shooting conditions and days suitable for shooting. [Figure 11] FIG. 2 is a diagram illustrating an example of a photographing condition database. [Figure 12] FIG. 10 is a diagram showing an example of an input screen for imaging conditions. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] [Judgment system] Fig. 2 is a diagram showing an example of the configuration of a determination system 1 including a determination device 10 of an embodiment. The determination system 1 of the embodiment shown in Fig. 2 includes the determination device 10, an external sensor unit 20, a weather information database 30 (hereinafter also referred to as "weather information DB 30"), and a weather forecast server 40. The determination device 10 of the embodiment is communicably connected to the external sensor unit 20, the weather information DB 30, and the weather forecast server 40 via a network NW.

[0019] (judgment device) The determination device 10 of the embodiment is a computer that determines whether a day meeting the imaging conditions input by the user is suitable for taking an infrared thermal image, based on an infrared thermal image of the steel deck 91, prior to a water retention inspection to detect water retention W inside the steel deck 91. The determination device 10 may be a stationary computer or a mobile terminal device such as a smartphone or tablet. The determination device 10 may also be composed of multiple computers.

[0020] The determination device 10 of the embodiment includes a control unit 11 and a storage unit 12. The control unit 11 of the embodiment includes, as functional components, a setting unit 111, a calculation unit 112, and a determination unit 113. The storage unit 12 of the embodiment stores various information, programs, etc., including an actual measurement database 121 (hereinafter also referred to as "actual measurement DB121") and an imaging condition database 122 (hereinafter also referred to as "imaging condition DB122").

[0021] (External sensor part) The external sensor unit 20 of the embodiment is a temperature sensor. The external sensor unit 20 of the embodiment is attached to a trough rib 941 or the like provided on a bridge, and measures the temperature of the trough rib 941 or the like.

[0022] (Weather information database) The weather information DB 30 of the embodiment is a database of past weather information managed by the Japan Meteorological Agency or the like.

[0023] (Weather forecast server) The weather forecast server 40 of the embodiment is a server device managed by, for example, the Japan Meteorological Agency or a weather forecasting company, and provides weather forecast information based on past weather information.

[0024] [Judgment method] Here, the determination method of the embodiment will be described. The determination method of the embodiment determines whether a day meeting the imaging conditions input by the user is suitable for taking an infrared thermal image prior to a water retention inspection to detect water retention W inside the steel deck 91 based on an infrared thermal image of the steel deck 91. This determination is made by the determination device 10.

[0025] As shown in FIG. 3, the determination method of the embodiment includes a temperature data collection step S10, an optimum day condition setting step S20 for infrared thermal image capture, and a determination step S30 of whether the optimum day condition is met.

[0026] <Temperature Data Collection Step (S10)> The temperature data collection step S10 in the embodiment shown in FIG. 3 includes a step of collecting temperature data of the steel deck 91 and a step of storing the collected temperature data to create a database.

[0027] (Step S11) In this embodiment, an external sensor unit 20 (temperature sensor) is installed to conduct a long-term continuous investigation of the thermal environment in a steel deck box girder bridge in which a U-rib, a type of trough rib 94, is provided on the underside of the deck plate 92. Figure 4 shows a schematic diagram of the steel deck box girder bridge being investigated. The steel deck box girder bridge in the example shown in Figure 4 is equipped with a U-rib Ua with water retention, which is known to have water retention inside, and a U-rib Ub without water retention, which is known to have no water retention inside. In the example shown, the U-rib Ua with water retention and the U-rib Ub without water retention that are being investigated are adjacent to each other.

[0028] As shown in Figure 4, a box girder temperature sensor Sc for measuring the air temperature inside the box girder is installed inside the box girder BG1. In addition, a water-retained U-rib temperature sensor Sa is installed on the outer surface of the water-retained U-rib Ua, and a water-free U-rib temperature sensor Sb is installed on the outer surface of the water-free U-rib Ub. In this embodiment, measurements by each temperature sensor are taken once every three hours, continuously for one year (366 days). The temperature data collection interval is set to three hours because it is desirable to ensure at least three hours for the infrared thermal image capture work.

[0029] As shown in Figure 5, a temperature sensor Sc is also installed inside the box girder BG2, which has a total of 20 U-shaped ribs U1 to U20 and is known to have no water inside. Temperature sensors S1 to S20 are also installed on the outer surface of each of these U-shaped ribs U1 to U20. The measurement dates are distributed over different seasons, and all measurements are taken at the same time. In this embodiment, measurements were taken a total of 22 times using each temperature sensor.

[0030] In the embodiment, temperature data was collected from box girders and U-ribs installed on an actual bridge, but this is not limited to this, and temperature data may be collected by creating a simulated test environment, for example.

[0031] (Step S12) The temperature data collected in step S11 is stored to construct the actual measurement DB 121.

[0032] <Step of Setting Optimal Day Conditions for Infrared Thermal Image Capture (S20)> Next, the optimum day conditions for infrared thermal image capture are set based on the constructed actual measurement DB 121. In the optimum day conditions setting step S20 of the embodiment shown in Fig. 3, a judgment criterion for determining whether a day is suitable for capturing an infrared thermal image is derived based on the collected actual measurement data, and the setting unit 111 of the judgment device 10 sets this as the optimum day conditions. In this embodiment, the optimum day conditions are set based on the results of each analysis in steps S21 to S24.

[0033] (Step S21) In this embodiment, the difference in surface temperature (negative temperature difference / positive temperature difference) between the U-rib Ua with water retention and the U-rib Ub without water retention is analyzed. Figure 6(a) shows an example of daily temperature changes in the U-rib Ua with water retention and the U-rib Ub without water retention. As shown in Figure 6(a), the surface temperature of the U-rib Ub without water retention rises significantly as the air temperature rises during the day, while the surface temperature of the U-rib Ua with water retention rises more slowly. As a result, during the day, a negative temperature difference occurs in which the temperature of the abnormal part (U-rib Ua with water retention) is lower than the normal part (U-rib Ub without water retention).

[0034] Furthermore, after sunset, the surface temperature of all U-ribs drops, but the temperature drop of the U-rib Ua with water retention is gradual. As a result, at night, a positive temperature difference occurs in which the temperature of the abnormal part (U-rib Ua with water retention) is higher than the normal part (U-rib Ub without water retention). Therefore, the temperature difference between the U-ribs can be used to estimate the presence or absence of water retention within the U-rib.

[0035] As shown in Figure 6(a), negative temperature differences that occur during the day tend to be large and last for a long time, while positive temperature differences that occur at night tend to be small and last for only a short time. Therefore, in this embodiment, the optimal day conditions are set assuming that negative temperature differences will occur.

[0036] (Step S22) Next, the number of times that negative temperature differences occurred is analyzed for each temperature difference. Figure 6(b) shows the number of times that negative temperature differences occurred in the measurements of the U-rib temperature sensor Sa with water retention and the U-rib temperature sensor Sb without water retention, collected every three hours over the course of a year.

[0037] As shown in Figure 6(b), there was a clear correlation between the number of occurrences of large temperature differences and the number of occurrences of small temperature differences. Therefore, if the temperature difference (criterion value) set as the optimal day condition is increased (for example, -4°C), the number of times that images can be taken decreases, and if the judgment value is decreased (for example, -2°C), the number of times that images can be taken increases.

[0038] Generally, to obtain an infrared thermal image that makes it easy to determine whether or not there is water in the U-rib, it is preferable to take the infrared thermal image when the temperature difference between the two is as large as possible, but prioritizing only the magnitude of the temperature difference has the disadvantage of reducing the number of days on which investigation is possible. For these reasons, in this embodiment, the absolute value of the temperature difference between the U-rib with and without water retention, which is set as the optimal day condition, is set to be 4°C or less.

[0039] (Step S23) The surface temperature of the U-rib varies due to factors other than internal water retention. For example, the surface temperature of the U-rib will show different values ​​depending on where the U-rib is located on the bridge. Therefore, we analyze the temperature variation depending on the position of the U-rib, focusing on U-ribs without water retention.

[0040] Figure 7(a) shows the temperature measurement results for the box girder BG2 and the 20 U-shaped ribs U1 to U20 (all of which have no water retention) installed on this box girder BG2. As shown in Figure 7(a), as the temperature inside the box girder BG2 rises, there is a tendency for the average temperature of the U-shaped ribs U1 to U20 without water retention to also rise. However, it was found that there was no increase or decrease in the temperature range (the difference between the upper and lower limits) of the U-shaped ribs U1 to U20 without water retention in a single measurement.

[0041] Figure 7(b) shows the distribution of the difference between the upper and lower limits of the surface temperatures of the U-ribs U1 to U20 without water retention. The average temperature variation between the U-ribs without water retention was 1.14°C, and the largest variation was 2.0°C, which is 2.0°C within the 2σ range. This means that an error of about 2.0°C can occur in the surface temperature of the U-rib due to causes other than water retention. Therefore, if the absolute value of the temperature difference used to determine whether water retention is present or absent is set to 2.0°C or less, there is a risk that a U-rib without water retention will be mistakenly determined to have water retention. Therefore, in this embodiment, the absolute value of the temperature difference between U-ribs with and without water retention, set as the optimal day condition, is set to a value greater than 2.0°C.

[0042] (Step S24) Next, to examine the extent to which the amount of retained water can be evaluated, the relationship between the amount of retained water and the accuracy of the assessment is examined. In this embodiment, to verify the relationship between the amount of retained water in the U-rib with retained water and the temperature difference between U-ribs with and without retained water, U-ribs (with and without retained water) installed within the same box girder with a longitudinal gradient are used. Temperature sensors were installed in the U-rib without retained water, and temperature sensors were also installed at positions corresponding to the amount of retained water of "full (240 mm)," "3 / 4 (180 mm)," "1 / 2 (120 mm)," and "1 / 4 (60 mm)" using the longitudinal gradient of the U-rib with retained water. The results of simultaneous temperature measurements of the outer surface of the U-rib using these five temperature sensors are shown in Figure 8.

[0043] As shown in Figure 8, the greater the amount of water trapped in the U-rib, the greater the temperature difference between U-ribs with and without trapped water. For this reason, if the absolute value of the temperature difference used to determine whether or not there is trapped water is 4°C, then as a guideline, trapped water of approximately 3 / 4 or more can be detected; if the absolute value is 3°C, then trapped water of approximately 1 / 2 or more can be detected; and if the absolute value is 2°C, then trapped water of approximately 3 / 8 or more (90 mm) can be detected.

[0044] It should be noted that, for example, contact-type water retention screening surveys using ultrasound from the underside of a steel deck can screen for water retention of 5mm or more, so it is undeniable that the detection accuracy is inferior to such surveys. However, considering the effort required to conduct contact-type water retention screening surveys for all of the vast number of U-ribs, it can be said that the detection accuracy of water retention screening using infrared thermal images is sufficient.

[0045] (Step S25) Based on the analysis results obtained in steps S22 to S24, optimal day conditions are set. In this embodiment, two optimal day conditions are set: "conditions for the temperature difference between the U-ribs with and without water retention" and "conditions for the duration of this temperature difference."

[0046] In this embodiment, the analysis results obtained in steps S22 to S24 reveal the trade-off relationship shown in Figure 9. For example, if the temperature difference value is set to -2°C, the number of occurrences increases and even small amounts of water retention can be detected, but there is a risk that errors due to factors other than water retention will be detected and a healthy U-rib will be mistaken for "water retention." Furthermore, if the temperature difference value is set to -4°C, the number of occurrences decreases. In consideration of these balances, in this embodiment, the temperature difference value is determined to be -3°C.

[0047] (Step S26) Next, the time condition for the temperature difference determined in step S25 to continue is determined and set as the optimum day condition for infrared thermal image capture. In this embodiment, since it is desired to ensure a minimum of three hours of imaging time as described above, a negative temperature difference of -3°C continuing for three hours or more is set as the optimum day condition for infrared thermal image capture. The setting unit 111 sets the optimum day condition according to the specification of the operator operating the determination device 10. The setting unit 111 may cause the determination device 10 to display an input screen (not shown) for the optimum day condition.

[0048] <Step of determining whether the optimal day conditions are met (S30)> In the step of determining whether the optimum day conditions are satisfied (S30), the determination device 10 determines whether or not one candidate photographing date satisfies the set optimum day conditions.

[0049] (Step S31) In step S31, multiple shooting conditions that affect whether the optimal day conditions are met are extracted. First, the actual measurement DB 121 is referenced to identify the fulfillment date, which is the day on which the optimal day conditions set in step S26 are met. Next, weather data for the identified fulfillment date is obtained from the weather information DB 30, an external database that stores weather information. Examples of weather data obtained from the weather information DB 30 include the temperature, sunshine hours, diurnal range (the difference between the minimum and maximum temperatures in a day), rainfall, and general weather conditions on the fulfillment date. Attributes of the fulfillment date, such as the date and season, and the weather data for the fulfillment date are analyzed, and multiple conditions that are closely related to the fulfillment of the optimal day conditions are extracted as shooting conditions. From the perspective of improving the accuracy of the determination, it is preferable to extract at least three shooting conditions.

[0050] In this embodiment, three shooting conditions a, b, and c are extracted as shooting conditions that affect whether the optimum day conditions are met (see FIG. 10). The shooting conditions a to c extracted in this embodiment include, but are not limited to, shooting condition a being the "month," shooting condition b being the "daily temperature range," and shooting condition c being the "weather overview."

[0051] (Step S32) The extracted photographing conditions a to c are each categorized into a plurality of patterns. For example, the "month" of photographing condition a is categorized into 12 patterns from January to December. Furthermore, the "daily temperature range" of photographing condition b may be categorized into about 10 types at 1°C intervals, for example, between 5°C or less and 15°C or more. The "general weather conditions" of condition c can be categorized into a plurality of patterns, for example, "sunny" and "rainy, then cloudy." It is preferable to categorize the general weather conditions into about 15 to 20 types, for example.

[0052] In the embodiment, the categorized shooting conditions are stored in the shooting condition DB 122. Fig. 11 shows an example of the shooting condition DB 122 of the embodiment. In the embodiment, each categorized pattern is labeled with a1 (January), a2 (February) ..., b1 (daily temperature difference of 5°C or less), b2 (daily temperature difference of 6°C or less) ..., c1 (sunny), c5 (rain followed by cloudy) ..., etc.

[0053] (Step S33) Next, the calculation unit 112 calculates the occurrence rate of fulfilled days p, which is the occurrence rate of days fulfilling the optimal day conditions, for each type of shooting condition, by referring to the actual measurement database 13. For example, as shown in Fig. 11, if the total number of days fulfilling the optimal day conditions in pattern a1 (January) is 15, the occurrence rate of fulfilled days pa1 for pattern a1 (January) is 0.48.

[0054] (Step S34) The calculation unit 112 weights each of the fulfillment day occurrence rates p. In this embodiment, the fulfillment day occurrence rate p for each type is weighted with a weight according to the reliability of the fulfillment day occurrence rate p. For example, if the fulfillment day occurrence rate p for one type of one shooting condition is close to 100% or 0%, the reliability is considered higher than when the fulfillment day occurrence rate p is 50%, and the weight is increased. In this embodiment, the weight w is calculated using the following formula (1). The weight w takes a value between 0 and 1.

[0055]

number

[0056] In Equation 1, w is the weight and p is the occurrence rate of fulfillment days.

[0057] In the embodiment, the calculated fulfillment day occurrence rate p and weight w are stored in the imaging condition DB 122 shown in FIG. 11, but the present invention is not limited to this.

[0058] (Step S35) In step S35, the calculation unit 112 calculates an expected value, which is the probability that the optimum day conditions will be satisfied on one candidate shooting date, based on a formula that includes at least three or more shooting conditions as variables. In this embodiment, the expected value S is calculated according to the input shooting conditions a to c based on the following formula (2).

[0059]

number

[0060] In Formula 2, pa is the fulfillment day occurrence rate for one type of shooting condition a, pb is the fulfillment day occurrence rate for one type of shooting condition b, pc is the fulfillment day occurrence rate for one type of shooting condition c, wa is the weight obtained by substituting the fulfillment day occurrence rate pa into Formula 1, wb is the weight obtained by substituting the fulfillment day occurrence rate pb into Formula 1, and wc is the weight obtained by substituting the fulfillment day occurrence rate pc into Formula 1. The expected value S is calculated by dividing the sum of the fulfillment day occurrence rates p(pa, pb, pc) multiplied by the weights w(wa, wb, wc) by the sum of the weights w. Values ​​corresponding to the specified type of shooting conditions a to c are substituted for the weights w and the fulfillment day occurrence rate p.

[0061] The determination device 10 of the embodiment may provide an input screen SC1 (see FIG. 12) for inputting shooting conditions for calculating the expected value S based on Equation 2. The determination device 10 of the example shown in FIG. 12 is a mobile terminal device such as a smartphone. The input screen SC1 displayed on the display of the determination device 10 includes input fields IA1, IA2, and IA3 for specifying the type of each shooting condition. In the input fields IA1 to IA3 of this example, a label attached to each type can be selected and input using, for example, a pull-down menu.

[0062] In the embodiment, shooting condition b is the diurnal temperature range, and shooting condition c is the general weather conditions, but these diurnal temperature ranges and general weather conditions can be acquired and input from the weather forecast server 40. Note that the configuration of input screen SC1 is not limited to this, and it may be configured such that, for example, by inputting the year, month, and date of the candidate shooting date, forecast data for the candidate shooting date is automatically acquired and input from the weather forecast server 40.

[0063] (Step S36) Next, the setting unit 111 sets a judgment threshold θ for the expected value S of the candidate shooting day. In this embodiment, the setting unit 111 refers to the actual measurement data stored in the actual measurement DB 121, extracts non-satisfied days that do not satisfy the optimal day conditions, and calculates the expected value S by substituting the shooting conditions a to c on the extracted non-satisfied days into Equation 2. This makes it possible to quantify past non-satisfied days, i.e., days that are unsuitable for shooting infrared thermal images.

[0064] It is preferable that the setting unit 111 sets the judgment threshold θ to a value that exceeds, for example, the maximum value of the expected value S of a non-satisfied day. However, if the judgment threshold set based on this criterion results in a significant reduction in the number of candidate days that are determined to be suitable for photography, the judgment threshold θ may be set to a value that is equal to or less than the maximum value of the expected value S of a non-satisfied day. However, even in this case, the judgment threshold θ is set to a value that is equal to or greater than the top 5% of the expected values ​​S of the non-satisfied days. This improves the accuracy of determining whether photography is suitable or unsuitable, and makes it less likely that a candidate day determined to be suitable for photography actually does not satisfy the optimal day conditions.

[0065] After inputting the shooting conditions for the candidate shooting date to be judged in the input areas IA1 to IA3, the judgement button BT is tapped. In response to the input of the judgement button BT, the judgement unit 113 executes the judgement process of step S37.

[0066] (Step S37) The determination unit 113 determines whether the expected value S calculated in step S35 is equal to or greater than a predetermined threshold value. In this embodiment, using the threshold value θ set in step S36, if the expected value S is equal to or greater than the threshold value θ (S≧θ), the determination unit 113 determines that the candidate shooting date having the shooting conditions input in step S35 is suitable for capturing infrared thermal images, and outputs the determination result. If the expected value S is smaller than the threshold value θ (S<θ), the determination unit 113 determines that the candidate shooting date is not suitable for capturing infrared thermal images, and outputs the determination result.

[0067] The determination result by the determination unit 113 may be displayed on the input screen SC1 shown in the example of Fig. 12. In the embodiment, the determination unit 113 substitutes the values ​​of the fulfillment day occurrence rate p and weight w corresponding to each type input in the input areas IA1 to IA3 of the input screen SC1 into Equation 2, and determines whether the candidate shooting date having the specified shooting conditions is suitable for shooting an infrared thermal image. The determination result is displayed in the determination result display area DA of the input screen SC1. In the illustrated example, the determination result display area DA displays text such as "optimal" or "unsuitable" depending on the determination result.

[0068] As shown in Figure 10, Equation 2 in this embodiment weights and narrows down each of the shooting conditions a to c by the reliability of whether the optimal day condition is satisfied or not, and calculates the probability that the optimal day condition will be satisfied for one candidate shooting date using these shooting conditions as variables. As shown in Figure 10, the determination method in this embodiment is intended to allow a candidate date determined to be "unsuitable for shooting" to actually satisfy the optimal day condition, but conversely, not allow a candidate date determined to be "suitable for shooting" to actually not satisfy the optimal day condition. This allows the reliability of the determination accuracy to be improved according to this embodiment.

[0069] [Taking infrared thermal images] In this embodiment, infrared thermal images of the U-rib are taken on a day determined to be suitable for photography. In this embodiment, the U-rib is photographed directly from the underside of the bridge, taking into consideration the ease of determining whether or not there is water. By taking the photograph on a day that meets the optimal day conditions, an infrared thermal image can be obtained that makes it easy to determine whether or not there is water.

[0070] According to the above-described embodiment, a determination method and a determination device can be provided that can determine whether a candidate date for taking infrared thermal images is suitable for taking them in a water retention inspection to detect water retention inside a steel deck.

[0071] Although the present invention has been described above by taking the embodiments as examples, the present invention is not limited to the above-described embodiments and can be embodied in various forms. [Explanation of symbols]

[0072] 1 Judgment System 10 Judgment device 11 Control section 111 Setting section 112 Calculation Unit 113 Judgment section 12 Storage section 121 Measurement Database 122 Shooting Condition Database 20 External sensor unit 30 Weather Information Database 40 Weather forecast server NW Network Ua U-rib with water retention Ub U-rib without water retention BG1 Box girder Sc Box girder temperature sensor Sa: Water retention, U-rib temperature sensor Sb U-rib temperature sensor without standing water U1~U20 U-rib S1~S20 temperature sensors SC1 input screen IA1~3 input area BT judgment button DA judgment result display area 91 Steel deck slab 92 Deck Plate 93 Pavement 94 Vertical ribs 941 Trunk Rib 95 horizontal ribs 96 Weld root 97 Deck-penetrating crack

Claims

1. Prior to a water retention inspection to detect water retention inside the steel deck based on an infrared thermal image of the steel deck, setting optimal day conditions suitable for capturing the infrared thermal image; calculating an expected value, which is the probability that the optimum day conditions will be satisfied on one candidate shooting date, based on an equation including at least three or more shooting conditions as variables; determining that the candidate photographing date is suitable for photographing the infrared thermal image if the expected value is equal to or greater than a predetermined judgment threshold.

2. The step of calculating the expected value includes: extracting three photographing conditions a, b, and c that affect whether the optimum day conditions are satisfied; A step of categorizing the photographing conditions; calculating an occurrence rate p of days satisfying the optimum day conditions for each type of photography condition; and weighting the incidence rate p by multiplying the incidence rate p by a weight w calculated by the following Equation 1, The method according to claim 1 , wherein the expected value S is calculated based on the following formula 2: [Equation 1] [Equation 2]

3. The judgment threshold is The determination method according to claim 2, wherein the setting is based on the expected value S calculated from the photography conditions on a non-satisfied day in the past when the optimum day conditions were not met.

4. 4. The method according to claim 1, wherein the photographing conditions include at least a diurnal temperature range and general weather conditions.

5. Prior to a water retention inspection to detect water retention inside the steel deck based on an infrared thermal image of the steel deck, a setting unit for setting optimal day conditions suitable for capturing the infrared thermal image; a calculation unit that calculates an expected value, which is the probability that the optimum day conditions will be satisfied on one candidate shooting date, based on an equation that includes at least three or more shooting conditions as variables; and a determination unit that determines that the candidate photographing date is suitable for photographing the infrared thermal image if the expected value is equal to or greater than a predetermined determination threshold.

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