When an elevator rope for a high-rise building is forcibly excited by long-period ground motion, rope displacement becomes large even if the ground acceleration is small. Therefore, detecting the rope sway in real time is important to avoid damage during and after earthquakes. In a previous method for calculating the rope vibration using the finite difference method (FDM), excitation waves are the machine room displacement and the ground displacement. However, these displacements cannot be directly obtained because acceleration is measured by seismic sensors. In this paper, a simplified calculation method, based on a single degree of freedom (SDOF) system, for estimating rope displacement during an earthquake by using the building's acceleration and ground acceleration is presented. Finite difference analyses of rope vibration are also performed to verify the validity of the simplified method. The results of this simplified calculation method agree with those of the conventional finite difference method, within the 20% error margin.
