Iceshedding on transmission lines results in longitudinal unbalanced forces on adjacent transmission towers,which significantly threaten the safety of transmission lines.The methodology of iceshedding simulation on transmission lines is developed by using the finite element method and validated by comparing the simulation results with those obtained from the modelscale experiments done by previous researchers.The responses of the towerline system induced by simultaneous iceshedding on the conductor and ground wire are analyzed.The developed methodology is then applied to study iceshedding considering unzipping effect,in which the influence of the velocity of iceshedding on the responses is investigated.Results from this study show that the longitudinal unbalanced forces induced by simultaneous iceshedding from the ground wire are greater than those from the conductor under similar condition.During the analysis of iceshedding considering unzipping effect,the slower the velocity of iceshedding is,the closer the responses are to those resulting from static unloading;and the faster the velocity of iceshedding is,the closer the responses are to those resulting from simultaneous iceshedding.