Nonparametric Estimation of Wave Dispersion in High-Rise Buildings by Seismic Interferometry

Mahdi Ebrahimian, Mohammadtaghi Rahmani and Maria I. Todorovska ABSTRACT Interferometric identification and health monitoring of high-rise buildings has been gaining increasing interest in recent years. The wave dispersion in the structure has been largely ignored in these efforts, but needs to be considered to further develop these methods. In this paper, (1) the goodness of estimation of vertical wave velocity in buildings, as function of frequency, by two nonparametric interferometric techniques is examined, using realistic fixed-base Timoshenko beam benchmark models. Such models are convenient because the variation of phase and group velocities with frequency can be derived theoretically. The models are those of the NS and EW responses of Millikan library. One of the techniques, deconvolution interferometry, estimates the phase velocity on a frequency band from phase difference between motions at two locations in the structure, while the other one estimates it approximately at the resonant frequencies based on standing wave patterns. The paper also (2) examines the modeling error in wave velocity profiles identified by fitting layered shear beam in broader band impulse response functions of buildings with significant bending flexibility. This error may affect inferences on the spatial distribution of damage from detected changes in such velocity profiles.