BASIC STUDY ON CONSTRUCTION OF THE PREDICTION SYSTEM FOR TRANSPORTATION OF AIRBORNE CHLORIDE IONS

It is very important to predict the airborne chloride ions to be transported from the sea in order to perform endurance design and maintenance. Furthermore, if it is possible to spatially visualize the distribution of the predicted airborne chloride ions, it is beneficial in helping to assess the chloride attack environment. In the above situation, we have proposed the airborne chloride ions estimation formula that taken into account the distance and altitude from the coast. In addition, the proposed formula takes into account the influence of the attenuation of airborne chloride ions. In the previous study (references 25) and 26)), the proposed formula has been approximated using a square law the relationship between the average wind speed and the generated airborne chloride ions. However, airborne chloride ions of Hashima Island in Nagasaki with special coastal terrain, there was a problem that it is difficult to capture the trend of the measured values in the proposed equation using the square-law. In this study, we have proposed the generation airborne chloride ions estimation equation using the exponential law. Also we estimated airborne chloride ions to be transported inland by using proposed equation, compared the estimated results with measured results and it was compared to previous studies. Furthermore, we attempt to construct a simple system that can visualize the spatial distribution of airborne chloride ions. First of all, in the study of the relationship between average wind speed and the generated airborne chloride ions, the approximation both the square-law and the exponential law were almost the same in Okinawa. On the other hand, in Hashima Island, the approximation compared exponential law with square law, it is possible to better the exponential law capture the trend of more measured results. Secondly, we have examined the attenuation coefficient used in equation (1). As the result, it was confirmed that attenuation coefficient considered the effect of shielding of building, the influence of the wind generated by the special terrain, effect of sedimentation rate of splash particles. In the study of airborne chloride ions to be transported to the inland, in Okinawa, the estimated value by the proposed formula and the BMS formula of the present study was to obtain a result in good agreement with the measured values. On the one hand, some of the observation points in Hashima Island, it was confirmed that the measured value and the estimated value does not match. However, the proposed equation in the study (Equation (1)) was able to capture the overall trend of the measured values. Finally, we visualized the airborne salt transport situation by using the estimated results of the proposed formula. In the created map of transportation airborne chloride ions, it is possible to take into account the distance from the coast, altitude, the building height. Also, it can be spatially visualized