Effect of Raindrop Size Distribution on Rain Load and Its Mechanism in Analysis of Transmission Towers

Rain load acting on a transmission tower is large enough to receive attention according to previous studies and, therefore, a parametric analysis is necessary to understand its mechanism. In this paper, the effects of different raindrop size distributions on both rain pressure and tower response are studied. First, a theoretical method is proposed to estimate the shape parameters of the gamma raindrop size distribution based on the conservation of rain intensity. The influence of raindrop spectrum on rain pressure in free wind field is then investigated. The results reveal that raindrop spectrum has great effect on the rain pressure distribution and its time interval has a large impact on the total rain pressure. In addition, the time interval has greater influence than the spectrum when the rain intensity is constant. At last, six different raindrop spectra are employed to simulate the tower response induced by wind and rain loads, of which the results indicate that the raindrop spectrum has a significant effect on the tower response. The maximum increasing percentage of rain load relative to wind load can reach up to 13.7%, indicating that the influence of rain load is quite remarkable and should be considered in analyzing the response of transmission towers.