Nonparametric estimation of wave dispersion in high‐rise buildings by seismic interferometry

Earthq Engng Struct Dyn

Todorovska

2014

Self Cite

SUMMARYNonparametric techniques for estimation of wave dispersion in buildings by seismic interferometry are applied to a simple model of a soil-structure interaction (SSI) system with coupled horizontal and rocking response. The system consists of a viscously damped shear beam, representing a building, on a rigid foundation embedded in a half-space. The analysis shows that (i) wave propagation through the system is dispersive. The dispersion is characterized by lower phase velocity (softening) in the band containing the fundamental system mode of vibration, and little change in the higher frequency bands, relative to the building shear wave velocity. This mirrors its well-known effect on the frequencies of vibration, i.e. reduction for the fundamental mode and no significant change for the higher modes of vibration, in agreement with the duality of the wave and vibrational nature of structural response. Nevertheless, the phase velocity identified from broader band impulse response functions is very close to the superstructure shear wave velocity, as found by an earlier study of the same model. The analysis reveals that (ii) the reason for this apparent paradox is that the latter estimates are biased towards the higher values, representative of the higher frequencies in the band, where the response is less affected by SSI. It is also discussed that (iii) bending flexibility and soil flexibility produce similar effects on the phase velocities and frequencies of vibration of a building.

“…6 in the companion paper [2]). The width of the time windows was chosen to be equal to the width of the central pulse of the virtual source, i.e.…”

Section: Methodsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 94%

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Wave dispersion in high‐rise buildings due to soil–structure interaction

Rahmani

Earthq Engng Struct Dyn

Todorovska

2014

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“…For structures with shear walls, fitting a layered Timoshenko beam, which accounts for bending deformation, is more appropriate. Our recent numerical experiments with simulated building response by a Timoshenko beam model, in which dispersion is cause by the presence of bending, and by a shear beam model with inserted floor slabs, in which dispersion is caused by scattering from the slabs, suggest that the velocity of the fitted shear beam is a representative value of the phase velocity on the band [64,65]. [62,63].…”

Section: Discussionmentioning

confidence: 99%

Time‐wave velocity analysis for early earthquake damage detection in buildings: application to a damaged full‐scale RC building

Rahmani

Earthq Engng Struct Dyn

Todorovska

2015

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Summary An algorithm for time velocity analysis of building response is presented, which identifies the wave velocity of vertically propagating waves through the building and detects their changes. The algorithm is intended for use in SHM systems for rapid assessment of the structural health and integrity following an earthquake. The velocities are identified by an interferometric algorithm, which involves least squares fit of pulses in impulse response functions. An important feature of this method is that it is not sensitive to the effects of soil–structure interaction. The algorithm is applied to a 12‐story RC building in Los Angeles, lightly damaged by the San Fernando 1971 earthquake. The results of the time velocity analysis are critically compared with results of analysis of input power, interstory drift, and instantaneous frequency. The identified average vertical wave velocity was initially ~140 m/s for the NS and ~110 m/s for the EW response and reduced by ~26% and 32%, respectively. The detected reduction of the fundamental frequency of vibration was larger (~44% for the NS and 48% for the EW response). The difference is interpreted to be due to softening of the soil–foundation system, to which the identified frequency of vibration is sensitive. The change was larger in the lower half of the building (~31% for the NS and ~37% for the EW response) as compared with the upper half (~24% for the NS and ~27% for the EW response), consistent with the observed damage. Copyright © 2015 John Wiley & Sons, Ltd.

“…The flexural and flexural-shear modes of deformation are most likely the main reason for dispersion of shear waves in a building structure [11][12]. In order to account for the dispersion, an empirical function is proposed in this study to characterize the shear wave phase velocity as a function of frequency at each layer as…”

Section: Dispersive Model Parametrizationmentioning

confidence: 99%

Parametric Estimation of Wave Dispersion for System Identification of Building Structures

Lecture Notes in Civil Engineering

Kohler

Massari

et al. 2017

The linear-elastic response of a building structure subjected to an earthquake base excitation can be approximated as the response of a continuous, spatially inhomogenous, dispersive, viscoelastic solid subjected to vertically incident plane shear waves. The frequency-dependent phase velocity and attenuation of seismic energy at different wavelengths, together with the inertial properties of the multilayer solid characterize the response of the building structure. The objective of this study is to identify the structural system by estimating the parameters that characterize the propagation of seismic waves in an equivalent multilayer viscoelastic solid. To pursue this objective, first, the measured dynamic responses of a building structure are used to derive the frequency response functions (FRFs) of the floor absolute acceleration with respect to the base excitation using a seismic interferometry approach. The FRFs obtained from the measured structural responses are then compared with the FRFs estimated using analytical models for one-dimensional shear wave propagation in a multilayer Kelvin-Voigt dispersive medium. Through a recursive Bayesian estimation approach, the parameters characterizing the phase velocity and damping ratio of the multilayer medium are estimated. This study provides a step forward in seismic interferometric identification of building structures by proposing a new method for parametric estimation of shear wave velocity and damping dispersion at the story level of a building structure. The estimated shear wave velocities before and after a damage-inducing event can be used to identify permanent loss of effective lateral stiffness of the building structure at the story level, thus can provide an alternative method for structural health monitoring and damage identification.