Influence of solar radiation for temperature and duration of getting wet of girders in the steel bridge

Steel bridges often have plural girders. Though the form of girders is the same, the difference of the position of girder in a bridge potentially causes different feature of corrosion environment around each girder. The purpose of this study is to clear the influence of solar radiation on corrosion of steel girders of bridge. In this study, these authors surveyed the eastern and the middle girders of the weathering steel bridge, which run north to south and has three girders. The eastern girder is exposed to solar radiation in the morning, while the middle one is not directly exposed to solar radiation. In this study, these authors analyzed, solar radiation, precipitation rate of airborn salt, temperature and relative humidity of area between girders, and temperature of girders. Both girders get wet due to dew during night to before morning, and get dry during daytime. In the case of clear weather in morning, solar radiation remarkably increased temperature of the eastern girder relative to middle one. In such case, the speed of the desiccation of the eastern girder was faster than that of the middle one. As a result, the time that the middle girder gets wet was three times as long as that of the eastern one. Therefore there is a possibility that corrosion of the middle girder will progress relative to that of the eastern one.