Seismic response of rail‐counterweight systems in elevators

Abstract

SUMMARYThe rail-counterweight systems in building elevators are known to be susceptible to earthquake-induced ground motions. Besides avoiding costly repairs and economic disruptions, it is of special interest to maintain the functionality of the elevators in critical facilities such as hospitals during, and especially after, a strong earthquake event. This paper presents an approach to develop a realistic analytical model of these vulnerable systems to study their seismic response behaviour. The model includes the exibilities of the guidance and supporting components of the counterweights in a systematic manner. Currently only the linear response behaviour is considered; however, the sources of non-linearities in the exible components are clearly identiÿed. The model considers the e ect of the di erential support motions from the building. Both the out-of-plane and in-plane responses of the rail-counterweight are studied and included in the stress calculations. Several sets of numerical results considering simultaneous action of the two orthogonal components of historic earthquakes are obtained to study the seismic response characteristics of the rail-counterweight system.

Seismic protection of counterweight–rails in elevators in buildings

“…The motions in these two planes are uncoupled, and thus they can be described by two separate systems of equations. The equations of motion of such a system without any protective system have been developed earlier by the authors [12][13][14]. Here, this analytical model is modiÿed to include the presence of a tuned mass damper in the passive and active mode.…”

“…The mechanical properties of the building and the rail-counterweight system are provided by the writers in their previous studies [12,13]. This counterweight system is examined for two recorded motions-the 1994 Northridge earthquake recorded at the Sylmar County Hospital Parking Lot (0:843g) and the 1940 El Centro earthquake recorded at the Imperial Valley Irrigation District (0:348g)-as well as for an ensemble for 50 acceleration time histories with broad band frequency characteristics.…”

“…This counterweight system is examined for two recorded motions-the 1994 Northridge earthquake recorded at the Sylmar County Hospital Parking Lot (0:843g) and the 1940 El Centro earthquake recorded at the Imperial Valley Irrigation District (0:348g)-as well as for an ensemble for 50 acceleration time histories with broad band frequency characteristics. These earthquake motions were applied at the base of the 10-storey building, and the multiple support motion ÿltered through the building were then used to deÿne the input to the counterweight-rails system [12]. To evaluate the e ectiveness of the proposed scheme, the maximum stresses in the rails under the controlled and uncontrolled conditions are compared.…”

“…In earlier studies [12,13] the authors have examined the responses of a representative analytical model of the rail-counterweight system under earthquake ground motion. The numerical results have shown that rails can experience high stresses under medium to strong earthquake ground motions.…”

Non‐linear seismic response of the rail‐counterweight system in elevators in buildings

“…Analytical models with di erent degrees of reÿnement have been used in these studies. Our earlier study [9] presented a model that included some important features of the counterweightrail system. However, the study was focused on examining the system characteristics with a linear model of the system.…”