Seismic Behavior of Rail Counterweight Systems of Elevators in Buildings

Keywords: Seismic performances.  Rail counterweight systems.  Building elevators.  Guide rail designs.  Seismic code provisions.  Elevator systems.  Critical facilities.  Hospitals.  Nonstructural components.

Abstract: This report describes an investigation of the seismic performance of elevator systems.  The report begins with an overview of elevator systems used in buildings, including various components of the system and their functions.  Because counterweights are the most vulnerable components to earthquake induced ground motion, the focus of this study is on the development of comprehensive analytical models of the rail-counterweight systems, including details of their guidance systems.  The authors develop both linear and nonlinear models to evaluate the seismic performance of the rail-counterweight system.  Several sets of numerical results are presented for different buildings, earthquake motions, rail sizes, flexibilities, and gap sizes.  Current code provisions for the design of guide rails are also discussed.  The analytical models and approach described in the report can aid in the seismic evaluation of critical facilities, such as hospitals, that are equipped with elevators.  This study can also help designers and manufacturers of elevator systems understand why elevators behave as they do in earthquakes and how to evaluate modification and design changes that may be necessary to improve their seismic performance.