JP2005264716A - Flying salt amount evaluating method and steel structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate the influences of the geography of a mountain located on the windward side of a bridge building point and a salt deposition amount for every bridge cross section by using an objective and simple method without performing simulation and one-year long observation of flying salt. <P>SOLUTION: This flying salt amount evaluating method uses a flying salt amount predicting function for an open geography for predicting the flying salt amount on a specified portion of a steel structure located within a predetermined offshore distance from a seacoast. A geography reducing coefficient for the flying salt based on geographic factors between the seacoast and the steel structure and a portion reducing coefficient for the flying salt on the specified portion of the steel structure are previously quantified from a simulated value or a measured value. The geography reducing coefficient is multiplied by a predicted value for the flying salt amount using the flying salt amount predicting function for the open geography to predict the flying salt amount on the steel structure. Then, the portion reducing coefficient is multiplied by the predicted value for the flying salt amount on the steel structure to predict the flying salt amount on the specified portion of the steel structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for evaluating the amount of salt salinity and a steel structure, and particularly suitable for use in determining whether or not to apply a weather-resistant steel material to a bridge in an area where the amount of salt salinity is high. The present invention relates to a flying salt content evaluation method that takes into account the influence of each cross-section of the object, and a steel structure using the flying salt content evaluation method.

  In recent years, bridges using weathering steel materials that do not require painting (hereinafter referred to as weathering steel bridges) have attracted attention.

  This weather-resistant steel bridge does not require painting because it uses a weather-resistant steel in which a protective rust layer is formed after a few decades, although red rust is initially seen, and is usually done every few years The repainting operation can also be omitted, and as a result, it is extremely effective in reducing the life cycle cost.

This weathering steel significantly slows the progress of corrosion in an environment exposed to the atmosphere by covering the surface with stable anticorrosive rust enriched with effective elements such as nickel, copper, phosphorus and chromium. However, it has been found that a weather-resistant steel is difficult to form a protective rust layer in an environment with a high salinity. Therefore, in Non-Patent Document 1, as shown in FIG. The use of weather-resistant steel is permitted on the inland side, which is divided into the regional divisions, and further on the inland side than the separation distance where the incoming salt content is 0.05 mg / dm ² / day (hereinafter abbreviated as mdd). On the other hand, on the sea side from the separation distance where the amount of incoming salt becomes 0.05 mdd, as a rule, the use of bare weather-resistant steel (also referred to as bare specifications) is not permitted. At the bridge construction point, it is necessary to observe the amount of salinity for one year or more and indicate that the amount of salt salinity is 0.05 mdd or less.

  In Non-Patent Document 1, the amount of incoming salt is approximated by the −0.6 power of the shore separation distance. In other words, the amount of incoming salt is shown for an arbitrary rip-off distance, but this is based on open terrain.

  On the other hand, in Patent Document 1, after calculating the amount of salinity, the wind flow analysis / salinity analysis including the construction point of the bridge is performed, and the amount of incoming salinity considering the influence of topography is evaluated in more detail. It is described that the construction suitability of the steel bridge is judged. According to this result, it is possible to make naked use possible even in an area where the coastal distance is short, in which non-patent literature 1 does not permit the use of weathering steel. Further, it is described that flow analysis / salinity analysis around the bridge section is performed, applicability of the weathering steel material is determined for each bridge section, and the optimum steel type is selected.

Ministry of Construction Public Works Research Institute, Steel Club Co., Ltd., Japan Bridge Construction Association: “Joint Research Report on the Application of Weatherproof Steel to Bridges (XX)-Design and Implementation Guidelines for Unpainted Weatherproof Bridges (Revised) Draft-March 1993 " JP 2001-152413 A

  However, in Non-Patent Document 1, for example, in the Sea of Japan coastal region I shown in FIG. 14 (A), there is a premise that weathering steel cannot be used barely up to a separation distance of 20 km. In addition, the amount of salinity at any rip-off distance obtained from open terrain is simply approximated by the -0.6 power of the rip-off distance. The decrease in the amount of incoming salt due to is not evaluated.

  In addition, according to Non-Patent Document 1, if a long-term observation of one year or more is performed in an area where the bare use of weathering steel is not permitted, it is proved that the amount of incoming salt is 0.05 mdd or less. However, such long-term observation is burdensome both in terms of time and economy.

  On the other hand, as described in Patent Document 1, a flow analysis / salinity analysis is performed, and a method of analytically obtaining the amount of incoming salinity at each point, or a flow analysis / salinity analysis around a bridge cross-section is performed. In order to predict the amount of salinity in detail, it is necessary to perform numerical analysis of the flow including advection and diffusion of salinity. Therefore, specialized knowledge such as data creation, calculation, and evaluation method of results is required. However, it has a problem that it is economically burdensome.

  The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to reduce the amount of salinity due to the influence of topography such as mountains located on the windward side of the steel structure construction site. The first problem is to evaluate by an objective and simple method without performing long-term observation.

  The present invention further evaluates the amount of adhered salt (micro amount of flying salt) for each cross section of the steel structure by an objective and simple method without carrying out flying salt simulation and long-term observation for one year. Is a second problem.

  The present invention is a salt salinity evaluation method for predicting the amount of salt salvage from a coast to a steel structure located within a certain separation distance by using a salt salinity prediction function in open terrain, The terrain reduction coefficient of the flying salinity based on the terrain factor between the steel structures is quantified in advance from a simulation value or a measured value, and the terrain reduction coefficient is calculated using the flying salinity prediction function in the opened terrain. The first problem is solved by multiplying the amount predicted value to predict the amount of salinity in the steel structure.

  Also, a method for evaluating the amount of salt salinity for predicting the amount of salt salient to a specific part of a steel structure located within a certain separation distance from the coast using a salt salinity prediction function in an open terrain, And the landform reduction coefficient of the flying salt based on the landform factor between the steel structure and the part reduction coefficient of the flying salt to the specific part of the steel structure are quantified in advance from simulation values or measured values, Multiplying the terrain reduction coefficient by the predicted salt concentration using the predicted salinity function in the open terrain to predict the amount of salt flow to the steel structure, and then calculating the part reduction factor to the steel structure The second problem is solved by predicting the amount of salt salvage to a specific part of the steel structure by multiplying the predicted amount of salt salinity to the object.

  The steel structure may be a bridge.

  The topographic factor may be at least a mountain.

  In addition, the topographic factor is the height of the mountain, and when there is no mountain, the landform reduction coefficient of the salinity corresponding to the height of the mountain is the lower limit of the topography reduction coefficient by the two-dimensional landform, and the three-dimensional landform The reduction factor can be set as the upper limit.

Also, the terrain reduction coefficient is
Mountain height (m) Topography reduction factor
0 1.0
200 0.2 -0.9
400 0.05-0.5
600 0.04-0.3
1,000 0.01-0.02
It can be within the range surrounded by.

  The present invention also provides a steel structure in which the amount of flying salt predicted by the above method for evaluating the amount of flying salt is less than a certain value, or the steel structure that is less than or equal to the certain value. The weathering steel of the part is made into a weathering steel having specifications according to the predicted value of the amount of incoming salt.

  In the present invention, for example, as shown in FIG. 2 (a), a short period (one week) by a recovery method using an anemometer 12 and a gauze 14 defined in JISZ2381, for example, in an actual complex terrain. When the salinity on the sea breeze passes through the mountain 10 by comparing (calibrating) these data based on the data obtained by the salinity observation of the degree) or the flow analysis / salinity analysis data by numerical simulation. The amount of salt taken by the mountain is evaluated as shown in FIG. Or, a general parameter study was conducted, and some standard topographical flow / salinity analyzes were performed in advance, and the sea breeze passed through the mountains. Assess the amount of salt that is sometimes taken away. Based on the above data, the amount of salinity deprived when the sea breeze crosses the mountain is shown in FIG. 3 as a topographical reduction factor for the predicted topographical salinity of the topography opened in Non-Patent Document 1 shown in FIG. Generalize and evaluate as shown. Note that this terrain reduction coefficient can be converted into a data bank.

  Also, flow analysis / salinity analysis by numerical simulation around the cross section of the bridge 20 as shown in FIG. 4 (a), or actual short-term salinity observation data by the recovery method as shown in FIG. 4 (b). From the comparison, the amount of incoming salt for each bridge cross-section part is analyzed and evaluated as a part reduction coefficient as illustrated in FIG. Note that this part reduction coefficient can also be made into a data bank.

  For the amount of salinity at the bridge construction site, the influence of topography is taken into consideration by multiplying the amount of salinity evaluated in Non-Patent Document 1 by the topography reduction factor. Also, the amount of salinity at each bridge cross-section is evaluated by considering the salinity reduction factor for the amount of salinity at the bridge construction site.

  In order to evaluate the topography reduction factor and the site reduction factor, and to make it a data bank, a certain amount of salt salinity analysis and short-term field observation are required.

  According to the present invention, it is possible to reduce the amount of salinity due to the influence of topography such as a mountain located on the windward side of the steel structure construction site, without objective salinity simulation or long-term observation for one year. It becomes possible to evaluate by the method. In addition, it is possible to evaluate the amount of salt adhesion (micro amount of flying salt) for each cross-section of the steel structure by an objective and simple method without performing flying salt simulation or long-term observation for one year. Become.

  Hereinafter, with respect to the relationship between the amount of salinity and the berthing distance in Non-Patent Document 1, the amount of salt salvage at the bridge construction site is reduced with reference to the topographical reduction factor that evaluates the effect of deprivation of salt by mountains, etc. In the embodiment of the present invention, the amount of salinity in each cross-sectional part of the bridge is evaluated as a part reduction coefficient, and the steel material corresponding to the amount of salinity in the cross-section part is further accurately selected at the bridge construction point. explain.

According to Non-Patent Document 1, in the region of Japan Sea I shown in FIG. 14 (a), the shoreline distance 20km is the prescribed coastal distance at which the incoming salt content is 0.05 mdd, and the shoreline distance X other than 20km. Log ₁₀ S of the incoming salt content S (mdd) at (km) is represented by X ^−0.6 . At this time, if the shore distance is within 20 km, the amount of incoming salt becomes 0.05 mdd or more. In order to use a weather-resistant steel material barely, as described in Non-Patent Document 1, it is necessary to perform long-term observation of flying salt content and prove that the flying salt content is 0.05 mdd or less.

  However, in reality, the amount of incoming salinity carried by the sea breeze over the mountain of various heights is deprived by the surface of the mountain as shown in FIG. In the present invention, since the salinity loss is converted into a data bank using the terrain reduction coefficient, the terrain reduction coefficient corresponding to the height of the mountain or the state of the mountain surface, for example, at the mountain position on the windward side of the bridge construction point. Reduction of the amount of incoming salt due to (see FIG. 3) can be expected. In addition, it is possible to expect a reduction in the amount of salinity that reaches the actual cross section with respect to the amount of salinity at the bridge construction point by using a site reduction coefficient (see FIG. 5).

In the example of FIG. 1, according to Non-Patent Document 1, Log ₁₀ S having an incoming salinity amount S (km) is represented by a ^rip- off distance X- ^0.6. When the amount S is 0.05 mdd, the relationship between the shore separation distance and the incoming salinity is represented by the curve 1 in FIG.

Log ₁₀ S = Log ₁₀ X ^−0.6 −0.5204 (1)

Assuming this equation (1), the amount of incoming salinity at the rip-off distance X = 5 km, which is the mountain position, is 0.115 mdd at point B. If the topography reduction coefficient in this case is 0.8 from the position of the mountain and the surface state of the mountain, the amount of incoming salt S is 0.115 × 0.8 = 0 at point C due to the presence of the mountain. .092 mdd
It becomes. Therefore, the amount of incoming salt after passing through the mountain is represented by equation (2) as curve 2 in FIG. 1 as a new curve.

Log ₁₀ S = Log ₁₀ X ^−0.6 −0.6168 (2)

  If the separation distance X = 10 km at the bridge construction point, the amount of incoming salt will be 0.061 mdd as shown by point E according to equation (2). When there is no mountain, the amount of salinity at the bridge construction point is calculated as 0.076 mdd as shown by point D from equation (1), so it is possible to evaluate that the amount of salinity is reduced by 20%. In this example, the amount of incoming salt is not less than 0.05 mdd at the bridge construction site with a shore separation distance of 10 km, but it is less than 0.05 mdd in a very high mountain or a mountain covered with abundant trees. There is a possibility.

Next, a method for evaluating the amount of incoming salt for each bridge site will be described. As shown in FIG. 7, it is assumed that the amount of incoming salt is 1.0 on the windward side. This is the amount of salinity in the macro sense at the bridge construction site. The wind does not distribute the salinity evenly to each part of the bridge cross section, and exhibits complex behavior depending on the flow pattern formed around the cross section. For example, at the upper and lower parts of the bridge cross section, the amount of salinity increases where the flow converges due to flow separation, but inside the beam, the amount of salt is reduced unless the flow separated from the beam under the beam enters the beam under the beam. Will not be high. Outside the girders, rain hits and salt washing can be expected, but in steel bridges, corrosion of closed under-girder spaces where dust and salt accumulate is the most problematic. FIG. 7 is an example in which the part reduction coefficient is set to 0.4 in the downstream side of the under-sparing space. In this example, the amount of incoming salt at the bridge construction point at the shore distance of 10 km has shifted to the curve 2 and is 0.061 mdd at the point E according to the equation (2). Therefore, the amount of incoming salt at the downstream girder position is 0.061 × 0.4 = 0.024mdd at the F point.
Thus, it falls below the specified value of 0.05 mdd.

  In this way, even in a place where non-patent use of the weather-resistant steel material is not permitted in Non-Patent Document 1, the amount of incoming salt is 0.05 mdd or less, and the weather-resistant steel material can be used naked.

  Even if the amount of incoming salt exceeds 0.05 mdd, it may be possible to use Ni-based high weathering steel having higher salt resistance than general weathering steel. Alternatively, by applying coating on the general weathering steel material in accordance with the amount of incoming salt, the weathering steel can be applied in a wider area with a higher amount of incoming salt.

  Based on the above results, it is possible to evaluate the amount of salt salinity at each bridge construction site or bridge cross-section by using a calculator on a desk without the need for a high-speed computer if the reduction factor is made into a data bank with a certain amount of data. In addition, it can be carried out in a short time.

  In the embodiment, the example of one mountain is shown, but the number of mountains is not limited to one, and as shown in FIG. 8, there are a plurality of mountains (two in the figure). Is equally applicable. In FIG. 8, the mountain on the sea side has a height of 300 m and a reduction rate of 50% (reduction factor of 0.5), and the mountain on the land side has a height of 150 m and a reduction rate of 20% (reduction factor of 0.8).

  When the present invention is applied to the evaluation of the amount of incoming salt when constructing a bridge, the following effects can be obtained.

  (1) According to the provisions of Non-Patent Document 1, even in areas where the stripping distance is short where bare use of weathering steel is not permitted, a decrease in the amount of salinity due to mountains etc. can be expected as a topographical reduction factor, The bare use of weathering steel can be made possible.

  (2) The amount of salt flow in each bridge section at the bridge construction point can be estimated as a part reduction coefficient, and the weathering steel can be used barely for each section.

  (3) Even when the amount of flying salt predicted in the present invention exceeds 0.05 mdd, it is impossible to use bare weather-resistant steel, but the amount of flying salt can be predicted. It is possible to use a weather-resistant steel material by painting on a highly resistant Ni-based high weather-resistant steel material or a general weather-resistant steel material.

  (4) If generalization of the terrain reduction coefficient and the site reduction coefficient by using data such as experimental values and analysis values is possible, it will be possible to perform a large-scale flow analysis / salinity analysis considering the terrain without using a high-speed computer. In particular, it is possible to evaluate the amount of salinity in each bridge construction point and bridge cross section in a very short time.

  (5) The method for obtaining the amount of salt salinity for each bridge construction point and bridge cross-section according to the present invention can be implemented in a short time by using a calculator. In addition, since the method is extremely simple, anyone can easily evaluate the amount of incoming salt at any time.

  (6) Although numerical analysis evaluation of the amount of incoming salinity by flow analysis / salinity analysis is not necessarily the same regardless of who implements it due to differences in parameters, analysis models, calculation software used, etc. Since the present invention uses an objective reduction factor, the result is the same regardless of the person evaluating.

(A) Topographical reduction factor based on observed values To obtain the observed values, focus on the 259.5m high mountain A and the 349.5m high mountain B in Chiba Prefecture. At the same time, flying salt was observed. Since the rip-off distance is different between the leeward observation point and the leeward observation point for both A and B, first, as shown in Fig. 9, the flying salinity J at the leeward observation point is separated from the leeward flying salinity. It was calculated as decreasing with the power of (km) to -0.6. That is, the amount of incoming salinity J was evaluated in consideration of the amount that decreases due to the separation distance even when no mountain exists, and the ratio I / J of the actual observed value I to that value was defined as the terrain reduction coefficient by the observed value. . The actual values used for the calculation are shown in Table 1.

  As a result, a topography reduction factor of 0.81 was obtained at A mountain with a height of 259.5 m and 0.57 at B mountain with a height of 349.5 m. The terrain reduction factor based on the observed values is shown by ▲ in Fig. 11.

(B) Topographical reduction coefficient based on analysis value On the other hand, in order to obtain the analysis value, as shown in FIG. 10, first, the amount of salinity on the ground surface without a mountain is calculated, and the amount of salt salinity at the leeward side of the mountain is calculated. C ₀ was obtained. Then calculate the over all amount of salt height H of the mountains, and also give the airborne salt amount C _H at the leeward side position of the mountain. In this case, the accuracy of the analysis value needs to be sufficiently reliable by comparing the observation values.

  A similar analysis was performed using the height H of the mountain as a parameter, and as a result, a result as indicated by ● in FIG. 11 was obtained. Since the analysis is a two-dimensional mountain as shown in FIG. 12 and there is no three-dimensional wind wraparound as shown in FIG. 13, there is a possibility that the reduction due to the influence of the mountain is evaluated at the maximum. is there. On the other hand, Mt. A and M. B, where the observations were made, are round and have a typical three-dimensional shape. As a result, wind wraps around the back of the mountain as shown in FIG. Therefore, it is possible to evaluate the reduction of salinity due to the influence of mountains in a place near the minimum. Therefore, the two-dimensional terrain reduction coefficient based on the analysis value and the three-dimensional terrain reduction coefficient based on the observation value can be used as the lower limit and the upper limit of the terrain reduction coefficient, respectively.

  In the above embodiment, the topographic factor is a mountain and the steel structure is a bridge. However, the type of topographic factor and the steel structure is not limited to these, for example, a vegetation zone having a filter effect to reduce incoming salt content. It is also possible to change the topography reduction factor of the mountain according to the difference in the surface condition of the mountain such as the presence or absence of vegetation zone. It is also possible to target steel structures other than bridges such as power transmission towers and monuments.

Diagram showing the amount of salinity, landform and salinity reduction method according to the present invention Diagram showing how to calculate the terrain reduction factor The figure which similarly shows the example of the terrain reduction coefficient Sectional view showing how to calculate the part reduction coefficient Cross-sectional view showing an example of the part reduction coefficient Explanatory diagram showing an example of the effect of mountains on the amount of incoming salt Cross-sectional view showing an example of the salt content ratio of flying salt to the bridge section The figure which shows the other example of application of this invention Explanatory diagram showing an example of how to calculate the terrain reduction coefficient based on observed values Explanatory drawing showing an example of how to obtain the terrain reduction coefficient by analysis value The figure which shows the terrain reduction coefficient by observation value and the terrain reduction coefficient by analysis value A diagram showing the flow of a two-dimensional mountain wind A diagram showing the flow of a three-dimensional mountain wind The figure which shows the area division described in nonpatent literature 1.

Explanation of symbols

10 ... Mountain 12 ... Wind direction anemometer 14 ... Gauze 20 ... Bridge

Claims (7)

A method for evaluating the amount of salinity salinity that predicts the amount of salt salinity to a steel structure located within a certain separation distance from the shore using a salinity salt amount prediction function in open terrain,
Preliminarily quantify the landform reduction coefficient of the incoming salinity based on the landform factor between the coast and the steel structure from the simulation value or measured value,
A flying salinity evaluation method characterized by predicting a flying salt amount to the steel structure by multiplying the landform reduction coefficient by a flying salt amount prediction value using a flying salt prediction function in the open terrain. A method for evaluating salt salinity, which predicts the amount of salt salvage to a specific part of a steel structure located within a certain separation distance from the coast, using a function for predicting salt salinity in open terrain,
The landform reduction coefficient of the incoming salinity based on the landform factor between the coast and the steel structure, and the part reduction coefficient of the incoming salinity to the specific part of the steel structure are quantified in advance from a simulation value or a measured value,
Multiplying the landform reduction coefficient by the salt salinity prediction value using the salt salinity prediction function in the open landform to predict the amount of salt salinity to the steel structure,
Next, the method for evaluating a salinity of salt in a portion of the steel structure is predicted by multiplying the part reduction coefficient by a predicted value of the amount of salt in the steel structure.   The method for evaluating salt content according to claim 1 or 2, wherein the steel structure is a bridge.   The method for evaluating salt content according to any one of claims 1 to 3, wherein the topographic factor is at least a mountain.   The topographic factor is the height of the mountain, and when there is no mountain, the topographical reduction factor of the salinity corresponding to the height of the mountain is the lower limit of the topographical reduction factor due to the two-dimensional topography, and the reduction factor due to the three-dimensional topography. The amount of incoming salt content evaluation method according to any one of claims 1 to 4, wherein the upper limit is the upper limit. The terrain reduction factor is
Mountain height (m) Topography reduction factor
0 1.0
200 0.2 -0.9
400 0.05-0.5
600 0.04-0.3
1,000 0.01-0.02
7. The method for evaluating the amount of incoming salt according to claim 6, wherein the amount of incoming salt is within a range surrounded by.   When the flying salt content predicted by the flying salt content evaluation method according to any one of claims 1 to 6 is less than a certain value, the steel structure or a specific part of the steel structure that has become the certain value or less. A steel structure characterized in that the weather-resistant steel is a weather-resistant steel having specifications according to the predicted value of the amount of incoming salt.

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