Study On The Collapse Mechanism Of Long-span Transmission Tower-line System Subjected To Wind And Rain Loads

Most part of China belongs to the monsoon climate,and the severe convective weather such as storm,torrential rain often appears.The long span transmission tower-line system is a wind sensitive structure and the collapse of transmission tower induced by the wind and rain loads usually occurs due to its large-span,high-rise and flexible.The influence of rain load is often neglected in the aspect of the study on the combined effect of the wind and rain loads.In order to ensure the operation safety,reliability and stability of the transmission tower-line system,the study of the dynamic response of transmission tower-line system under the wind and rain loads is of great significance.Transmission tower-line system finite element model is established using ABAQUS.The mechanism of the rain load is studied to establish the formula for calculating the rain load.The time histories of wind and rain loads are simulated and the collapse mechanism of the transmission tower-line system under the wind and rain loads is studied.The paper mainly focused on the following aspects:(1)Based on the 2D wind field established without considering the effect of fluctuating wind speed,the influence of the parameters such as the altitude of the falling raindrop H,the raindrop diameter d and the surface roughness length z0 on the velocity ratio y is analyzed.The fitting formula for the velocity ratio is derived and multiplied by the time history of wind speed to obtain the time history of rain speed.This method is named as equation approach.(2)Based on the 2D wind field established with the consideration of the effect of fluctuating wind speed,the time history of rain speed can be obtained directly by programming in the MATLAB and this method is named as program approach.The program flow chart of the program approach is given to provide a reference about the numerical simulation of the wind and rain field.(3)Based on the time histories of wind and rain loads simulated through the equation approach and program approach,the nonlinear dynamic analysis of transmission tower subjected to wind load together with or without rain load is carried out,respectively.When the rainfall intensity is assumed to be 709.2 mm/h which is the heaviest rainfall ever on record in china,the maximum displacement percentage induced by rain load relative to wind load at the top of tower is 15.4%.The effect of rain load acting on the structures such as the transmission tower should not be ignored.(4)The reasonable collapse simulation method and criterion are chosen.The collapse of long span transmission tower-line system under different wind direction is simulated.The collapse process,distribution of ISDR value and collapse mechanism of transmission tower-line system subjected to wind and rain loads are studied.