Design Earthquakes Based on Probabilistic Seismic Hazard Analysis
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Earthquake is one of the most destructive natural disasters leading to financial, environmental, and even human losses. The most effective approach to prevent losses induced by structural damage is seismic design for structures, in which the determination of design earthquakes, including seismic design spectra and seismic design ground motions, is of great importance. Probabilistic Seismic Hazard Analysis (PSHA) has been widely used for the determination and selection of design earthquakes. However, there are a number of issues on the engineering application of PSHA in obtaining the design earthquakes, which need to be addressed before it can be readily implemented into reliability- and performance-based seismic design. In this research, based on the PSHA, the generation of seismic design spectra and spectrum-compatible earthquake groundmotions is studied. The PSHA-based seismic design spectra mainly include Uniform Hazard Spectrum (UHS), predicted spectrum based on Ground-Motion Prediction Equations (GMPEs), and Conditional Mean Spectrum considering ε (CMS-ε). These existing design spectra, however, do not or only partially provide probabilistic knowledge about the simultaneous occurrence of spectral accelerations at multiple vibration periods. The lack of such probabilistic knowledge of the design spectra may prevent them from being incorporated into reliability- and performance-based seismic design. The purpose of this study is to bridge the gaps between seismological analyses and engineering applications, i.e., to find suitable representations of design earthquakes from the PSHA. A generalized approach is developed to generate seismic design spectra using both scalar and vector-valued PSHA,which overcomes the deficiencies and preserves certain advantages of the existing PSHA-based seismic design spectra. An approximate approach is also developed to simplify the approach to the generation of seismic design spectra so that they can be easily incorporated into structural design and further performance-based seismic design. On the other hand, spectrum-compatible earthquake ground motions, which are generated by manipulating recorded ground motions, have been widely used for seismic design verification and seismic qualification of structures. The existing spectral matching algorithms in frequency-domain, however, may distort the valuable information contained in recorded earthquake ground motions due to the deficiency of the transformation methodologies on which they are based. To properly preserve the frequency contents and nonstationary characteristics of recorded ground motions, a signal processing method called Hilbert-Huang Transform (HHT) is used to generate spectrum-compatible earthquake ground motions. In the proposed generation procedures, the strategy of the selection of recorded ground motions is based on the PSHA so that the generated ground motions reflect realistic seismic hazard for the site of interest.