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Title: SHM-based seismic performance assessment for super high-rise buildings under long-period ground motion
Authors: Hu, Rongpan
Degree: Ph.D.
Issue Date: 2019
Abstract: With the rapid urbanization, more and more super high-rise buildings with complex structural systems have been built around the world. Though most of the super high-rise buildings are located in low seismic regions, they may be subjected to seismic hazards from long-period ground motions generated from large-magnitude distant earthquakes. The long-period ground motions generated from the 2011Tohoku earthquake induced the excessive vibrations of the high-rise buildings in Tokyo and caused considerable damage to the facilities, nonstructural components, and structural components, paralyzing the city for weeks. It is therefore essential to conduct a timely seismic performance assessment of super high-rise buildings subjected to long-period ground motions to facilitate the decision-making on their post-earthquake repair, maintenance, and reoccupation. However, this objective has been hindered by several obstacles: (1) there are few reliable long-period ground motion records especially due to large-magnitude distant earthquakes; (2) the complex structural configuration of a super high-rise building with a hybrid structural system and the limited number of sensors installed in the building make a complete performance assessment almost impossible; (3) the complexity of the coupled bending-torsion vibration of the super high-rise building under bi-directional long-period ground motions make seismic assessment very difficult; and (4) there are limited researches on both system-level and component-level seismic performance assessment methods for super high-rise buildings. This thesis aims to address these issues and to propose comprehensive solutions for the structural health monitoring (SHM)-based seismic performance assessment of super high-rise buildings under long-period ground motions. Firstly, this study proposes a novel three-segment curve model (in log-log space) to model the Q-f relationship to overcome the potential biased estimation in the long-period range by the commonly-used "coda wave" method. The optimal curve-fitting process is performed to determine the Q-f relationship for the Hong Kong region based on recently-available digital ground motion records. The calibrated whole path anelastic attenuation factor is then incorporated with the stochastic simulation procedure to generate representative synthetic long-period ground motions. The simulated results are validated through comparison with the measured seismic records in both frequency and time domains.
Secondly, this study proposes an integrated optimal multi-type sensor placement and response-excitation reconstruction scheme based on the Kalman filter algorithm and in terms of a 2D condensed finite element model of a super high-rise building. The multi-type sensors used in this study include GPS, inclinometers, and accelerometers. The proposed scheme enables determining the optimal multi-type sensor placement in terms of the minimum number and the best location of multi-type sensors for achieving the best response and excitation reconstruction simultaneously. An experimental study on a cantilever beam using multi-type sensors is performed to verify the proposed scheme. The experimental results show that the proposed schemes is feasible, effective and robust. Towards a complete and accurate seismic assessment of a super high-rise building under bi-directional long-period ground motions, this study extends the optimal multi-type sensor placement scheme for the best reconstruction of structural responses and ground motions to a full-scale 3D finite element model of a super high-rise building. The selected locations and types of sensors are capable of not only capturing the coupled bending-torsional vibration but also providing an unbiased estimation of the unmeasured responses of seismic-vulnerable components and bi-directional ground motions. Thirdly, to make full use of the accurate and complete estimation of all the key structural responses of an instrumented high-rise building, a real-time warning system and a probabilistic post-earthquake performance assessment are proposed. The warning system monitors the building structural behavior in real-time and issues various levels of warning whenever it detects structural responses exceeding the preset safety thresholds. The assessment method evaluates the structural component integrity after an earthquake in a probabilistic manner, incorporating the extreme value distribution of the reconstructed structural responses with the structural component fragility functions to determine the damage probabilities of the structural components. Finally, an innovative method for generating building-specific fragility curves for various structural components is developed. The fragility curves of the key structural components are obtained by performing the incremental dynamic analysis on the nonlinear finite element model of the super high-rise building. The generated fragility curves are then incorporated with the extreme response distributions to yield an estimation of the probabilistic damage states of the key structural components. This innovative method and the probabilistic post-earthquake performance assessment method are implemented to a 3D nonlinear finite element model of the super high-rise building to verify their feasibility and effectiveness. The numerical results manifest that the proposed framework provides a reliable way of estimating the safety and operability levels of the instrumented super high-rise building after the earthquake event.
Subjects: Hong Kong Polytechnic University -- Dissertations
Tall buildings -- Earthquake effects -- Evaluation
Earthquake hazard analysis
Structural health monitoring
Pages: xIi, 279 pages : color illustrations
Appears in Collections:Thesis

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