An Optical Technique for Measuring Transient and Residual Interstory Drift as Seismic Structural Health Monitoring (S2HM) Observables

Abstract

Building interstory drift (ID), which is a measure of the relative displacement between two successive floors in a vibrating building, is a key response parameter utilized in both seismic design and post-earthquake damage assessments. To this point in time, there has been no accepted methodology or sensor technology for reliable and accurate direct measurements of building drift. Indirect measurement of drift, through signal processing and double integration of accelerometer data, is fraught with challenges, particularly when inelasticity-induced permanent drifts occur. In this paper, recent developments toward a new optically-based technique for measurement of both transient interstory drift (TID(t)) and residual interstory drift (RID) are described. The ability of a newly designed laser-based optical sensor system to directly measure interstory drift is demonstrated through experimental and model-based evaluations. This sensor technology has progressed to the point where practical application is feasible as an enabling S2HM technology.