Characterization of coupled response of wind-excited base-isolated tall buildings

Date

2022-08

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Abstract

A comprehensive analysis of wind pressure measurement data is conducted to investigate the characteristics of spectra and coherence of alongwind, crosswind and torsional story forces on a high-rise building model. New models are then established for describing the power spectra density (PSD) functions and coherence functions of alongwind, crosswind and torsional story forces, base bending moments and torque. These advanced models permit wind-induced dynamic response analysis of tall buildings in both frequency and time domains. An analytical framework is presented for estimating stochastic three-dimensional (3D) coupled wind-induced response of base-isolated tall buildings with eccentricity. The building is featured with 3D coupled mode shapes in alongwind, crosswind and torsional directions due to existence of eccentricities in mass and resistance centers. The base isolation system has coupled biaxial hysteretic restoring force-displacement relation. The accuracy of reduced-order building model in terms of lower modal displacements is examined. The 3D building responses are then quantified by time history analysis approach. The characteristics of inelastic response, the influence of mean wind load and the eccentricities between mass center and resistance center on superstructure, and the influence of biaxial interaction of hysteretic restoring force character of base isolation system are examined through a comprehensive parametric study. The responses are also compared to those of fixed-base building. New insights are provided toward improved understanding of coupled responses of base-isolated buildings with eccentricity and biaxial hysteretic restoring force character under strong wind loads. The influence of biaxial interaction of hysteretic restoring forces in both alongwind and crosswind directions depends on the yielding levels of alongwind and crosswind base displacements, their correlations and power spectral characteristics. A detailed parameter study is conducted to better understand the biaxial interaction on inelastic response. The results demonstrate that the biaxial interaction leads to increase in low-frequency component and decrease in resonant component of base displacement and decrease in relative upper building responses in the direction with lower response. The influence of biaxial interaction increases when both response levels are quite different and are strongly correlated and the larger response has a greater level of yielding. The influence of biaxial interaction is greater when the base displacements have higher low-frequency components. The biaxial interaction also leads to fast growth of time-varying mean alongwind base displacement of the isolation system. The nonlinear inelastic response of base-isolated buildings with biaxial hysteretic restoring forces is also estimated using statistical linearization approach. The statistical linearization approach is established by approximating the hysteretic displacements in a linear model thus permits use of more efficient spectral analysis approach for response estimation. The performance of statistical linearization approach for uniaxial and biaxial hysteretic models with Gaussian distribution assumption is examined. The results show that linearization approach gives quite accurate estimation of standard deviations (STDs) of responses with relatively weak non-Gaussian characteristics, such as alongwind base displacement and upper building responses. It underestimates the STD of crosswind base displacement at higher wind speeds which has strong softening non-Gaussian character. The hysteretic displacement and crosswind base displacement show apparent non-Gaussian character at higher wind speed. The linearization approach can be further improved by considering non-Gaussian response character. A relatively simple but sufficiently accurate procedure is proposed for modeling directionality effect in computing extreme responses of wind-excited structures with various mean recurrence intervals and system reliability associated with multiple limit state responses. The reliability of structure associated with single and multiple limit state responses (demands) is analyzed with consideration of directionality effect. It is illustrated that the multiple limit state responses can be assumed to be mutually independent. The characteristics of failure probability influenced by wind directionality and structural orientation are investigated. The sensitivity of failure probability estimation to the assumed probability distribution model of extreme response is also examined.


Embargo status: Restricted until 09/2023. To request the author grant access, click on the PDF link to the left.

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Keywords

High-Rise Buildings, Inelastic Response, Base-Isolated Tall Building, Eccentricity, Biaxial Hysteretic Restoring Force, Alongwind Response, Crosswind Response, Torsional Response, Wind Directionality Effect, Uncertainty, Reliability Analysis.

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