JP7020448B2 - Method for estimating the amount of flying salt and method for determining the applicability of weathering steel - Google Patents

Description

The present invention relates to a method for estimating the amount of flying salt flying from the sea to a target point on land, and a method for determining the applicability of weathering steel used at the target point.

Weathering steel is a low alloy steel containing elements such as copper, nickel, and chromium that are effective in improving weather resistance, and under appropriate circumstances, there are a number of dark brown protective rust layers that can suppress the corrosion rate. Since it is formed in a year, it can be used without painting.

In recent years, especially in the construction of steel bridges, it is possible to use it without painting against the background that it is required to reduce not only the initial cost at the time of construction but also the life cycle cost including maintenance after construction. The use record of weathering steel is increasing.

However, it is known that weathering steel is difficult to form a protective rust layer in an environment with a high salt concentration and cannot exhibit sufficient weather resistance. Therefore, in Japan, research activities on the application conditions of weathering steel (Ministry of Construction Civil Engineering Research Institute, Steel Club, Japan Bridge Construction Association: Joint research report on the application of weathering steel to bridges ( Based on XX) -Design and construction guidelines for unpainted weathering steel bridges (revised proposal)-), criteria for determining whether or not to construct steel bridges using weathering steel have been established.

According to this standard, the amount of flying salt in the planned construction site of a weathering steel bridge is actually measured by a predetermined method, and the measured value of this amount of flying salt is a predetermined threshold (for example, 0.05 mdd (mg / dm ² / day)). It is determined that the weathering steel bridge can be used unpainted if it is confirmed that the following conditions are met, or if the planned construction site is located within a predetermined designated area.

Further, in Patent Documents 1 to 3, the amount of corrosion of weathering steel during a predetermined service period is predicted based on the numerical values of environmental factors such as the amount of flying salt, temperature, humidity, wetting time, and sulfur oxide amount, and the weathering resistance is predicted. The applicability of steel is judged.

Further, in Patent Document 4, in estimating the amount of flying salt flying from the sea to the target point on land, the offshore distance D from the point closest to the target point on the coastline to the target point and the above on the coastline are described. From the wave height intensity H at the point, the flying salt content C is estimated by the following formula (C _α : constant).

C = C _α × H × D ^-0.6
Further, in Patent Document 5, a wind speed / wind direction database is used for estimating the amount of flying salt.

However, in the techniques disclosed in Patent Documents 1 to 3, the amount of flying salt, which is one of the factors for determining whether or not a weathering steel bridge can be constructed, is determined by a predetermined method at the planned construction site of the weathering steel bridge. It is necessary to actually measure and confirm that the measured value of the amount of flying salt is equal to or less than a predetermined threshold. Therefore, it is necessary to conduct a field survey of the amount of flying salt for one year or more before determining whether or not a weathering steel bridge can be constructed, which increases the cost of determining whether or not a weathering steel bridge can be constructed and hinders process control. Is likely to occur.

Moreover, even if the field survey of the amount of flying salt is conducted over one year, the measured value of the amount of flying salt obtained is only the data for a limited period of a specific one year. Therefore, if the weather for one year when the field survey of the amount of flying salt was conducted was not as usual, the validity of the judgment result of whether or not to construct a weathering steel bridge remains questionable. Furthermore, when predicting the amount of corrosion of weathering steel, it is necessary to enter not only the amount of flying salt but also other environmental factors such as temperature, humidity, wetting time, and amount of sulfur oxides, so the formula for predicting the amount of corrosion is complicated. Is.

Therefore, in the techniques disclosed in Patent Documents 1 to 3, instead of conducting a field survey of the amount of flying salt at the planned construction site, an existing actual measurement database of the amount of flying salt may be used, or Patent Document 4 It is conceivable to estimate the amount of flying salt by the method disclosed in. However, the actual measurement database of the amount of flying salt and the amount of flying salt estimated by the method of Patent Document 4 are safe values on the premise that the terrain is flat. Therefore, even if the planned construction site of the weathering steel bridge is located behind a large mountain, for example, and the salt content flying to the weathering steel bridge is blocked, the weathering steel bridge can be constructed. There was a problem that the topographical impact could not be taken into consideration, such as the fact that construction was judged to be impossible.

Further, in Patent Document 5, when wind speed / direction data is used for estimating the amount of flying salt, it is necessary to also perform flow analysis and salt diffusion analysis using topographical data, and whether or not a weathering steel bridge can be constructed is determined. There was a problem that it took time to judge. Further, in Patent Document 5, "the first step of calculating the amount of salt generated on the coast" is performed, but the definition of "coast" is not clear. For example, if the planned construction site of a weather-resistant steel bridge is located on a small island, the entire circumference of the planned construction site is regarded as the above "coast", or only the coast closest to the planned construction site is regarded as the above "coast". There was a problem that the estimated value of the amount of flying salt changed depending on how the "coast" was defined.

Japanese Unexamined Patent Publication No. 2005-134320 Japanese Unexamined Patent Publication No. 2006-053122 Japanese Unexamined Patent Publication No. 2006-208346 Japanese Unexamined Patent Publication No. 2012-163374 Japanese Unexamined Patent Publication No. 2001-152413

The present invention is a method for estimating the amount of flying salt that can estimate the amount of flying salt flying from the sea to a target point on land with a relatively simple configuration, and a method for determining the applicability of weathering steel used at the target point. The purpose is to provide.

In order to solve the above problems, the present invention has the following features.

[1] A method for estimating the amount of flying salt that flies from the sea to a target point on land, using wind speed / direction data at five or more points including the target point and four points around the target point. A method for estimating the amount of flying salt, which comprises calculating the proportional number of sea breeze energy to a target point and calculating the estimated value of the amount of flying salt using the proportional number of sea breeze energy.

[2] The surrounding four points are the first point closest to the target point on the coastline, and a straight line extending in a direction forming +90 degrees from the direction from the target point to the first point intersects the coastline. The direction from the target point to the first point is +270 at the second point, the third point where the straight line extending in the direction forming +180 degrees from the target point intersects the coastline, and the direction from the target point to the first point. The method for estimating the amount of flying salt according to the above [1], wherein a straight line extending in a direction consisting of a fourth point intersecting the coastline.

[3] The method for estimating the amount of flying salt according to the above [1] or [2], wherein the wind speed / wind direction data obtained from the meteorological analysis by the meso-meteorological model is used as the wind speed / direction data.

Here, as the mesoscale meteorological model, for example, the regional meteorological model "WRF", which is software developed by the US Atmospheric Research Center and the like, can be used. "WRF" is software that analyzes changes in the state of the atmosphere, which can be expressed by temperature, wind, atmospheric pressure, water vapor, etc., according to the laws of physics such as fluid mechanics and thermodynamics.

[4] The method for determining the applicability of the weathering steel used at the target point, which is the method for estimating the amount of flying salt according to any one of the above [1] to [3]. A method for determining applicability of a weathering steel, which comprises determining that the steel grade is applicable when the estimated value is equal to or less than the allowable upper limit value of the amount of flying salt determined for each weathering steel grade.

[5] A method for determining the applicability of weathering steel used at the target point. Using the wind speed / direction data, the land wind energy proportional number at the target point is calculated, and the land wind energy proportional number is used. , The corrosion suppression amount of the weathering steel is calculated, and it is calculated by the corrosion resistance determined for each steel type of the weathering steel and the method for estimating the amount of flying salt according to any one of the above [1] to [3]. An estimated value of the amount of corrosion of the weathering steel is calculated using the estimated value of the amount of flying salt and the amount of suppression of corrosion, and when the estimated value of the amount of corrosion is equal to or less than the allowable upper limit value, the steel grade. A method for determining the applicability of weathering steel, which comprises determining that the applicability is applicable.

[6] The method for determining applicability of a weathering steel according to [4] or [5], wherein the weathering steel is used for a steel bridge constructed at the target point.

According to the method for estimating the amount of flying salt and the method for determining the applicability of weathering steel using the method of the present invention, wind speed / direction data at 5 or more points including the target point and 4 points around the target point can be obtained. By using it, it is possible to estimate the amount of flying salt flying from the sea to the target point on land in a short time and with high reliability without requiring a detailed field survey of the amount of flying salt over a long period of time.

Further, by setting the first to fourth points as the four surrounding points according to the method of [2] above, even if the target points are located in an island or a peninsula, the target points can be viewed from all sides around the target points. The amount of flying salt can be estimated with even higher reliability by appropriately taking into consideration the amount of flying salt. In particular, the relative relationship between the wind speed / wind direction data at the target point and the wind speed / wind direction data at the first point closest to the target point on the coastline is between the target point and the first point. It differs depending on whether there is a shield such as a mountain or not. Therefore, if the target point where weathering steel is used is located behind a mountain, for example, and the salt arrival due to sea breeze is blocked, this effect is taken into consideration when estimating the amount of incoming salt and weather resistance. Applicability of weathering steel can be determined more appropriately.

In addition, as described in [3] above, by using the wind speed / wind direction data obtained from the meteorological analysis by the meso-meteorological model as the wind speed / direction data, the wind speed / direction can be related even at a point where there is no observation record of the wind speed / direction. It is possible to estimate the amount of flying salt with high reliability without the need for a field survey.

Further, as in the above [5], by using the proportional number of land wind energy, it is possible to determine the applicability of the weathering steel in consideration of the corrosion suppressing effect due to the surface of the weathering steel being dried by the land wind.

Further, the method for estimating the amount of flying salt and the method for determining the applicability of weathering steel using the method of the present invention can be suitably used for determining the applicability of weathering steel used for steel bridges.

It is a flowchart which shows the flow of the method of estimating the amount of flying salt content and the method of determining the applicability of weathering steel according to the first embodiment of the present invention. It is a figure which shows the setting method of 4 points (1st to 4th points) around a target point in the method of estimating the amount of flying salt of this invention. It is a graph which shows the example which compared the estimated value of the flying salt content estimated by the method of estimating the flying salt content of the present invention with the measured value of the flying salt content. It is a flowchart which shows the flow of the applicability determination method of the weathering steel of the 2nd Embodiment of this invention.

An embodiment of the method for estimating the amount of flying salt and the method for determining the applicability of weathering steel of the present invention will be described below with reference to the drawings.
(First Embodiment)
FIG. 1 is a flowchart showing a flow of a method for estimating the amount of flying salt and a method for determining applicability of weathering steel according to the first embodiment of the present invention.

First, in step S1, a steel grade of weathering steel that is a candidate for use is selected.

In step S2, the target point _P0 , which is the planned construction site of the structure using the weathering steel (for example, a steel bridge), is set in the map data. The target point P ₀ shall be set on the land L in the map data. As the map data, a generally widely used geographic information system (GIS) or the like can be used.

In step S3, as shown in FIG. ₂ , in the map data, the _first point P1 which is the closest point to the target point P0 on the coastline SL is set. Furthermore, the directions from the target point P ₀ to the first point are +90 degrees, +180 degrees, and +270 degrees, and the three straight lines extending in the directions intersect the coastline SL, respectively, at the _second to _fourth points P2 to P4. Is set on the above map data.

In step S4, the wind speed data W ₀ (m / s) and the wind direction data θ ₀ (degrees) obtained at a predetermined time interval at the target point P ₀ , and the first to fourth points P ₁ to P ₄ , respectively. In, the wind speed / direction data (W ₁ (m / s), θ ₁ (degrees)) to (W ₄ (m / s), θ ₄ (degrees)) obtained at predetermined time intervals during a predetermined period are input values. Prepare as. Here, the wind direction θ ₁ (degrees) at the first point is an angle with respect to the direction from the first point P ₁ to the target point P ₀ . Similarly, the wind directions θ ₂ to θ ₄ (degrees) at the _2nd to _4th points P2 to _P4 are the angles from the _2nd point P2 to the target point P0 and the target from the _3rd point P3, respectively. The angle with respect to the direction toward the point _P0 and the angle with respect to the direction from the _fourth point P4 to the target point _P0 . For example, when the predetermined period is one year and the predetermined time interval is one month or two months, one month at each of the target points _P0 and the _first to _fourth points P1 to P4. Alternatively, the average wind speed and the maximum wind direction for two months can be prepared for one year, and these can be used as input values with the above-mentioned wind speed / wind direction data obtained at one-month or two-month intervals over one year.

The wind speed / direction data (W ₀ (m / s), θ ₀ (degrees)) to (W ₄ (m / s), θ ₄ (degrees)) are the target points P ₀ and the first to fourth points. _{In each} of P1 to P4, the measured values observed at the predetermined time intervals over the predetermined period may be used, or instead, the target points P obtained from the meteorological analysis by the meso meteorological model. The wind speed / direction values at ₀ and each of the _first to _fourth points P1 to P4 may be used.

In step S5, the proportional number of sea breeze energy from each of the _first to _fourth points P1 to _P4 to the target point P0 is calculated.

The proportional number of sea breeze energy at the target point P ₀ is the component of the square of the wind speed W ₀ at the target point P ₀ in the direction from the first point P ₁ to the target point P ₀ , that is, W ₀ ² cos θ ₀ (m ² / s). ² ) is calculated as the accumulated value Σ (W ₀ ² cos θ ₀ ) (m ² / s ² ) during the above predetermined period.

The proportional number of sea breeze energy from the first point P ₁ to the target point P ₀ is the square of the wind speed W ₁ (m / s) at the first point P ₁ in the direction from the first point P ₁ to the target point P ₀ . The component, that is, W ₁ ² cos θ ₁ (m ² / s ² ), is calculated as the accumulated value Σ (W ₁ ² cos θ ₁ ) (m ² / s ² ) during the predetermined period.

Similarly, each of the sea breeze energy proportional numbers from each of the _second to _fourth points P2 to P4 to the target point P0 is Σ (W ₂₂ cos θ ₂ ) _, Σ ⁽ W ₃₂ cos θ ³ ) _, Σ. It is calculated as (W ₄ ² cos θ ₄ ) (m ² / s ² ).

In step S6, the estimated value Cp ( _mdd ) of the amount of flying salt from the sea to the target point P0 is calculated. The estimated flying salt content Cp is obtained in step S5, where the linear distance from _each of the _first to _fourth points P1 to _P4 to the target point P0 is D1 to _D4 (km), respectively. It is calculated according to the following equation (1) using the sea breeze energy proportional number (α is a constant). However, when each of D ₁ to D ₄ is less than 1 (km), 1 is used as the value to be substituted in the equation (1), and when each of D ₁ to D ₄ exceeds 40 (km), the equation is used. Use ∞ (infinity) as the value to be assigned to (1).

Here, the constant α is the wind speed / direction data (W ₁ (m / s), θ ₁ (degrees) on the right side of the above equation (1) at the target point P ₀ where the measured value of the amount of flying salt is obtained. )-(W ₄ (m / s) (m / s), θ ₄ (degrees)), actual distances D ₁ to D ₄ (km) from each of the first to fourth points P ₁ to P ₄ . It is a value obtained by substituting the value and substituting the measured value of the amount of flying salt into Cp on the left side. A constant α is calculated for each of the plurality of target points P ₀ for which the measured value of the amount of flying salt is obtained, and the value of α obtained empirically based on these is 0.04 to 0.25 (mdd. It is about s / m ² ).

In FIG. 3, the land point of 34 degrees 51 minutes north latitude and 139 degrees 55 minutes east longitude is set as the target point P ₀ , and the first to fourth points P ₁ to P ₄ are set based on this target point P ₀ . Wind speed / direction data W observed at 1-hour intervals from the beginning of each month to the end of each month from _April 2005 to March 2006 at the target points _P0 and the _1st to 4th points P1 to P4. Monthly estimated flying salt content Cp (mdd) calculated by inputting ₀ to W ₄ (constant α = 0.18 (mdd · s / m ² )) and the above target points from the sea. The graph which compared the measured value of the amount of the incoming salt for each month which came to P ₀ (the land point of 34 degrees 51 minutes north latitude, 139 degrees 55 minutes east longitude) is shown.

As shown in FIG. 3, the amount of flying salt fluctuates from month to month, but the estimated value of flying salt Cp (mdd) fluctuates almost in proportion to the measured value of flying salt, according to equation (1). It can be seen that the calculated flying salt content estimated value Cp (mdd) is an effective value close to the measured value.

In step S7, it is determined whether or not the estimated flying salt content Cp (mdd) calculated in step S6 is equal to or less than the allowable upper limit of flying salt content determined for each steel type selected in step S1. For example, when the steel type selected in step S1 is an SMA material (welded structure weathering resistant hot-rolled steel material) (JIS G3114), 0.05 mdd or the like can be used as the allowable upper limit value of the amount of flying salt.

When it is determined in step S7 that the estimated flying salt content Cp is equal to or less than the allowable upper limit value (Yes), it is determined in step S8 that the steel grade selected in step S1 is applicable at the target point _P0 . To. If it is determined in step S7 that the estimated flying salt content Cp exceeds the allowable upper limit value (No), it is determined in step S9 that the steel grade selected in step S1 is not applicable at the target point _P0 . .. This completes the method for determining the applicability of the weathering steel of the first embodiment.
(Second Embodiment)
FIG. 4 is a flowchart showing a flow of a method for determining applicability of weathering steel according to the second embodiment of the present invention.

The second embodiment is based on the method of estimating the amount of flying salt and the method of selecting the steel type of the weathering steel of the first embodiment, and further takes into consideration the corrosion suppressing effect due to the surface of the weathering steel being dried by the land breeze. Therefore, the applicability of weathering steel is determined.

Steps S11 to S16 are performed in the same manner as in steps S1 to S6 of the first embodiment.

In step S17, when the weathering steel selected in step S11 is installed at the target point _P0 , the estimated corrosion amount before taking into consideration the corrosion suppressing effect due to the surface of the weathering steel being dried by the land wind. t ₁ (mm / year) is calculated using the estimated flying salt content Cp (mdd) calculated in step S16 and the corrosion resistance determined for each weathering steel grade selected in step S11.

In step S18, the proportional number of land breeze energy at the target point _P0 is calculated.

In step S19, the amount of corrosion suppression due to land breeze t ₂ (mm / year) is calculated using the land breeze energy proportional number at the target point 7 calculated in step S18.

In step S20, the estimated corrosion amount t ₁ (mm / year) calculated in step S17 before taking into account the corrosion suppression effect due to land wind, and the corrosion suppression amount t ₂ due to land wind calculated in step S19 ( From mm / year), the estimated corrosion amount t (mm / year) ₌ t, taking into consideration the corrosion suppression effect due to land wind when the weathering steel selected in step S11 is installed at the target point P0. Calculate _{1 -} t2.

In Table 1, three target points P ₀ (Point A: Land point at 34 ° 51'N, 139 ° 55'E, Point B: Land at 37 ° 46'N, 139 ° 04'E, Point C: Weather-resistant steel (steel grade: SMA material) is applied to each of the land points (35 degrees 22 minutes north latitude and 132 degrees 47 minutes east longitude), and at point A for 12 months from April 2005 to March 2006, points B and At point C, for the example installed for 12 months from February 2005 to January 2006, the offshore distance D ₁ (km) between the target point P ₀ and the first point P ₁ and the three target points P ₀ The measured value of the amount of flying salt (mdd), the proportional number of land wind energy at the three target points (average value for one year), and the measured value of corrosion amount of the weather-resistant steel (mm) (average value of the upper and lower flanges) are shown.

As in points B and C in Table 1, under the condition that the proportional number of land breeze energy is almost the same, that is, the effect of suppressing corrosion by the land breeze is almost the same, the larger the amount of flying salt, the larger the measured corrosion amount. On the other hand, when the proportional number of land breeze energy is large as in point A, it can be seen that the weathering steel is dried by the land breeze, so that corrosion is suppressed and the measured corrosion amount becomes small.

In step S21, it is determined whether or not the corrosion amount estimated value t (mm / year) calculated in step S20 is equal to or less than the corrosion amount allowable corrosion amount. The upper limit of the allowable corrosion amount of the weathering steel is preferably set to, for example, 0.03 (mm / year), 0.3 mm / 50 years, 0.5 mm / 100 years, or the like.

When it is determined in step S21 that the estimated corrosion amount t (mm / year) is equal to or less than the allowable upper limit value (Yes), the steel grade selected in step S11 can be applied at the target point _P0 in step S22. Is determined. If it is determined in step S21 that the estimated flying salt content Cp exceeds the allowable upper limit value (No), it is determined in step S23 that the steel grade selected in step S11 is not applicable at the target point _P0 . .. This completes the method for determining the applicability of the weathering steel of the second embodiment.

In the method for estimating the amount of flying salt and the method for determining the applicability of weathering steel of the present invention, for example, a program capable of executing the processing flow of the above-mentioned first embodiment and the second embodiment is installed in a general-purpose personal computer. It can be carried out by doing.

_P0 target point (planned construction site)
P ₁ 1st point P ₂ 2nd point P ₃ 3rd point P ₄ 4th point D ₁ Straight line distance from 1st point to target point D ₂ Straight line distance from 2nd point to target point D ₃ From 3rd point Straight line distance to the target point D ₄ Straight line distance from the 4th point to the target point W ₀ Wind speed at the target point W ₁ Wind speed at the 1st point W ₂ Wind speed at the 2nd point W ₃ Wind speed at the 3rd point W ₄ 4th point Wind direction θ ₀ Wind direction at the target point θ ₁ Wind direction at the first point θ ₂ Wind direction at the second point θ ₃ Wind direction at the third point θ ₄ Wind direction at the fourth point L Land SL coastline

Claims (7)

It is a method of estimating the amount of flying salt that comes from the sea to the target point on land.
The target point , the first point closest to the target point on the coastline, and the second point where a straight line extending in a direction extending at +90 degrees from the target point to the first point intersects the coastline. The direction from the target point to the first point is +180 degrees, and the direction from the target point to the first point is +270 degrees with the third point where the straight line extending in the direction intersects the coastline. Using the wind velocity / direction data at 5 or more points including the 4th point where the straight line extending to the coastline intersects the coastline , the sea breeze energy proportional number to the target point is calculated.
A method for estimating the amount of flying salt, which comprises calculating the estimated value of the amount of flying salt using the sea breeze energy proportional number. The method for estimating the amount of flying salt according to claim 1 , wherein the wind speed / wind direction data obtained from the meteorological analysis by the meso meteorological model is used as the wind speed / direction data. It is a method for determining the applicability of weathering steel used at the target point.
When the estimated value of the amount of flying salt calculated by the method for estimating the amount of flying salt according to claim 1 or 2 is equal to or less than the allowable upper limit value of the amount of flying salt determined for each weathering steel type. A method for determining applicability of weathering steel, which comprises determining that the steel type is applicable. Using the wind speed and wind direction data at 5 or more points including the target point where weathering steel is used and 4 points around the target point, the sea breeze energy proportional number to the target point is calculated.
Using the sea breeze energy proportional number, the estimated value of the amount of flying salt flying from the sea to the target point on land was calculated.
Using the wind speed / direction data, the land wind energy proportional number at the target point is calculated.
Using the land breeze energy proportional number, the amount of corrosion suppression of the weathering steel was calculated.
Using the corrosion resistance determined for each type of weathering steel, the estimated value of the amount of flying salt, and the amount of corrosion suppression, the estimated value of the amount of corrosion of the weathering steel is calculated.
A method for determining applicability of weathering steel, which comprises determining that the steel grade is applicable when the estimated value of the amount of corrosion is equal to or less than the allowable upper limit value. The four surrounding points are
The first point on the coastline that is closest to the target point,
A second point where a straight line extending in a direction forming +90 degrees from the target point toward the first point intersects the coastline.
A straight line extending in a direction of +180 degrees from the target point toward the first point intersects with the coastline at the third point, and
A fourth point where a straight line extending in a direction forming +270 degrees from the target point toward the first point intersects the coastline.
The method for determining applicability of a weathering steel according to claim 4, wherein the steel is made of. As the wind speed / direction data, the wind speed / wind direction data obtained from the meteorological analysis by the meso meteorological model is used.
The method for determining applicability of a weathering steel according to claim 4 or 5. The method for determining applicability of a weathering steel according to any one of claims 3 to 6 , wherein the weathering steel is used for a steel bridge constructed at the target point.

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