Elevators are essential for vertical movement in high-rise buildings. However, the rope may be snagged due to a resonance phenomenon that occurs when the natural periods of the rope and the building are close. In fact, numerous cases of rope snagging were reported during past major earthquakes. This study evaluates the risk of rope snagging at each floor, assuming that the elevator cage is stopped at various floors. Seismic response analysis of the rope was first conducted, and a regression model was developed based on the relationship between the maximum rope displacement and the maximum acceleration at the top of the building. Using this regression model, fragility curves were derived to quantify the risk. As a result, the risk of snagging was not greatest on the floors where the natural frequencies of the rope and the building closed, but rather on the upper floors, depending on the characteristics of the seismic waves used. This method enables the identification of high-risk floors in advance and provides useful insights for determining appropriate refuge floors for elevator cages during earthquakes.
Matsushima et al. (Wed,) studied this question.