Numerical analysis of dropper stress under a moving load based on the uplift displacement for a high-speed railway

The most essential cause of the fracture of the dropper is the effect of alternating stress for a long time. Therefore, in order to ensure the safe operation of high-speed railways, the influence of moving loads on the stress of a dropper was investigated in this study. Due to a high-voltage catenary system, it is very difficult to measure the moving load. Thus, the uplift displacement measured by some software and hardware devices has been applied to the contact wire instead of the moving load. The response equation for the contact wire has been derived so as to determine the initial and boundary conditions of each dropper. Then it was combined with the equation for vibration analysis of the dropper and the stress of each dropper was calculated by using the finite-difference method based on a written MATLAB program. The results show that the dropper stress, during a certain period goes through two stages of immediate rebound and bending compression when the uplift displacement is large. After the pantograph passes, the vibration of the dropper tends to be smooth; also, dropper stress variation with timecan be described by three stages: immediate rebound, vibration attenuation, and bending compression. In addition, the maximum tensile stress of dropper Ⅳ was the highest. It indicates that dropper Ⅳ was more prone to fracture than other droppers.