Structural Response and Risk Considering Regional Ground Motion Characteristics

Chase, Robert Edward

Graduate Thesis Or Dissertation

Structural Response and Risk Considering Regional Ground Motion Characteristics Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/8336h216h

Abstract

Regions of the U.S. have different tectonic environments and, correspondingly, seismic ground motion characteristics can vary significantly across the country. Structures’ seismic risk depends greatly on these characteristics, which can significantly influence structural seismic response. Current seismic design procedures and many typical assessments only consider ground motion intensity at a structure’s fundamental period, and not motion characteristics like frequency content and ground motion duration. This dissertation explores the relationships between regional ground motion characteristics and structural risk through three studies that aim to fill this gap in the literature. Chapter 2 investigates induced earthquakes in the central U.S. to investigate the characteristics of ground motions and resulting structural response. Ground motion suites of induced motions and tectonic motions with similar earthquake source characteristics are gathered for dynamic analysis on a numerical model of a residential chimney. Tectonic motions are found to produce slightly higher probabilities of chimney collapse, when compared to induced motions of the same intensity. These higher probabilities are due to differences in the frequency content, which stem from differences in depth, stress drop, and regional seismic environment between the two ground motion sets. Chapter 3 analyzes light-frame wood buildings in sequences of induced motions, through dynamic simulations, to investigate damage and seismic loss accumulation in multiple shaking events. The study finds that, although cracks widen and elongate in subsequent events, the vulnerability of new light-frame wood construction does not increase when initially damaged at levels observed in recent induced events. However, seismic losses or repair costs may increase dramatically if owners are repairing after every event. In Chapter 4, light-frame wood buildings are simulated using hazard-consistent incremental dynamic analysis to assess collapse capacities and expected seismic loss, for one to four-story commercial and multifamily buildings at sites in California and the Pacific Northwest. Modification factors for design base shear are developed for these buildings to account for site-specific spectral shape. Collapse risk, losses, and design base shear are found to be higher for sites with larger contributions from subduction hazards, due to broader motion frequency content and, to a lesser extent, longer shaking durations.

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