抄録
The many different factors involved in the deterioration of external building materials make it a complex phenomenon. The effect of rain is one of the most important factors. This paper deales with the development of the rainfall apparatus for evaluating the deterioration caused by rain. The first step was to develop an apparatus which produced vertically falling waterdrops. It was designed to produce four different types of waterdrops similar to actual vertically falling raindrops. Method A simulated weak and medium rainfall. A water tank with 14 nozzles producing waterdrops was set up at a height of 3 meters above ground. The waterdrops were then finely dispersed by a wire netting. Method B simulated hard and severe rainfall. The waterdrops, pressured by a pump, were sprayed intermittently by the switching system of a solenoid valve. Then they were finely dispersed through wire nettings. These two methods produced waterdrops similar to actual rainfall in regards to the falling properties ; falling velocity, drop diameter, size distribution and rainfall intensity. The second step was to develop an apparatus which produced driving rain. This was achieved by adding an air fan to the apparatus producing vertically falling waterdrops. Falling waterdrops on the vertical face were measured. And the similarity of the condition between actual driving rain and waterdrops produced by the apparatus was discussed. The two above mentioned studies led to the development of an apparatus for evaluating deterioration caused by rain. This apparatus was successful in producing waterdrops resembling to actual raindrops.
