Seismic protection of counterweight–rails in elevators in buildings

Abstract

SUMMARYThe counterweight in an elevator, being the heaviest component, can often overstress the guide rails during a strong earthquake. To reduce the in-plane counterweight response, the use of a part of the counterweight mass as a tuned mass damper in the passive and active modes is examined. The passive TMDs can reduce the stresses in the rails, but their performance can be signiÿcantly improved when they are used in the active mode. An actuator with saturation capacity less than 10% of the weight of the counterweight could reduce the critical stress response to as low a level as, or even lower than, the maximum response induced by the out-of-plane motion of the counterweight.

Acceleration Feedback‐Based Active and Semi‐Active Seismic Response Control of Rail‐Counterweight Systems of Elevators

“…The dimensions of the counterweight's frame is 3.505 m high, 0.711 m wide and 0.152 m deep in which the weights fill up to two-third of the height. Other mechanical details about the equivalent stiffness properties of the system are given in Reference [4]. This counterweight system received the seismic input filtered through a ten-story building in which it was located.…”

“…The detailed development of the complete equations of motion is given in Reference [4]. Here we only provide the final set of equations primarily for the in-plane direction as the proposed active or semi-active devices are placed only in this direction.…”

“…(4) are the equivalent stiffness coefficients for the in-plane motion at the upper and lower corners of the counterweight, respectively, and k br is the bracket stiffness coefficient. The equivalent stiffness coefficients include the flexibilities of the rails, bracket and helical springs in the roller guides, and are defined in References [4,6]. The equivalent springs have a bilinear force-deformation relationship, as shown in Fig.…”

“…in the code). A more complete discussion of these nonlinearities and their effects on the seismic response of the rail-counterweight system is discussed in References [4,7]. The coefficient k T in Eq.…”

“…These dynamic effects have often damaged the counterweight rails and other hardware attached to the system. Several studies [5,9,10,12] were conducted to examine the dynamic behavior of these systems with different models, including a few recent ones by the writers [4,6,7]. In the most recent study [7], the writers have used an analytical model of the counterweight with roller guides, including the flexibilities of all supporting and guiding components (e.g., roller guide assemblies, guide rails and support brackets).…”