Calculation of rain load based on single raindrop impinging experiment and applications

In this paper, a method for calculating the rain load based on the single raindrop impinging experiment is presented, and a wind tunnel test is carried out to validate its effectiveness. The raindrop impinging force is measured using a self-made piezoelectric transducer. Based on the experimental results, a fitting formula of the peak force is proposed, which is then used to normalize the time-history of the raindrop impinging force. According to the experimental results and the law of conservation of momentum, a method is proposed for calculating the rain load in each rainfall event. The final formula derived is then used in the numerical simulation of a transmission tower subjected to the wind and rain loads, and it is demonstrated that the maximum percentage of root-mean-square (RMS) acceleration induced by the rain load relative to the wind load can reach to 22.4% for the basic wind speed of 5 m/s and rain intensity of 200 mm/h, which indicates that the effect of rain load on the tower response is not negligible. Meanwhile a wind tunnel test has been conducted to verify the simulation results and good agreement has been achieved in this regard. Finally, response analysis of transmission tower for a specific location of a recorded typhoon is performed and results reveal that the rain load should be given more attention during a typhoon.