Elevators as a Repeatable Excitation Source for Structural Health Monitoring in Buildings

Abstract

In this paper, the feasibility of using elevator motion as a statistically repeatable excitation for use in structural health monitoring (SHM) of tall buildings is investigated. Robust SHM benefits from a repeatable excitation source, but in buildings this is problematic for many technical and practical reasons. Ambient vibrations are therefore often used for repeated system identification of such civil structures. In tall buildings, the movement of elevators contributes to the mix of ambient vibrations. The 17-story Factor Building on the UCLA campus is heavily instrumented for earthquakes, and has high-resolution real-time continuous recording of vibration data. There are 72 accelerometers distributed throughout the building in addition to nearby ground motion and borehole reference accelerometers. Using Factor as a test bed, experimental studies of elevator-induced building vibrations were conducted. Building monitoring was augmented with additional elevator sensors and a small shaker. Initial results indicate that elevator-induced vibrations are statistically separable from other ambient vibration components in both the time and frequency domains. However, it may be necessary to measure elevator position and/or elevator counterweight vibrations. Work continues on the development of a methodology to use the elevators as a repeatable source for SHM of the Factor Building and other tall buildings.