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

Abstract

SUMMARYElevators in buildings serve a very important function and are among the critical components of an essential facility. They have several mechanical and electrical components that are known to be susceptible to damage during earthquake occurrences. The counterweights, being the heaviest, are among their most vulnerable components. The ASME code has made several provisions to improve the performance of the counterweights in seismic events. To evaluate their performance under code-mandated provisions, it is necessary that a comprehensive and realistic analytical model is used. This paper uses a detailed model of a counterweight of a traction elevator to study its in-plane and out-of-plane dynamic behavior. The model incorporates the multiple support inputs and exibilities of the counterweight guidance system along with their non-linearities caused by the clearance limitations. The study examines the e ect of changing clearances, variability of input motions, and the use of tie brackets on the system response, and evaluates the impact of some of the code provisions on the dynamic behavior of the 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.…”

“…Obviously, this arrangement is only possible for reducing the motion in the in-plane direction. However, the in-plane motion also happens to be the more critical of the two motions [13], and controlling this should improve the system performance. In the following, we present some results of using a passive and active TMD to examine its e ectiveness.…”

“…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.…”

“…The counterweight is perhaps the most vulnerable component of elevator, primarily because it is also the heaviest part of an elevator system. Therefore, the studies on seismic response and performance evaluations of counterweight-rail systems have been of continued research interest for the last 25 years [5][6][7][8][9][10][11][12][13].…”