Thesis (Ph. D.)--North Carolina State University, 1999. / Spiral bound. Includes vita. Also available on the Internet. Includes bibliographical references (p. 206-214) and abstract.

published_or_final_version / abstract / toc / Earth Sciences / Master / Master of Philosophy

Performance-based earthquake engineering is an emerging field of study that complements the prescriptive methods that the design codes provide to ensure adequate seismic performance of structures. Accounting for uncertainties in the performance assessments forms an important component in this area. In this context, the present study focuses on two broad themes; first, treatment of uncertainties and the application of the first-order reliability method (FORM) in finite-element reliability analysis, and second, the seismic risk assessment of reinforced concrete structures for performance states such as, collapse and monetary loss. In the first area, the uncertainties arising from inherent randomness (“aleatory uncertainty”) and due to the lack of knowledge (“epistemic uncertainty”) are identified. A framework for the separation of these uncertainties is proposed. Following this, the applicability of FORM to the linear and nonlinear finite-element structural models under static and dynamic loading is investigated. The case studies indicate that FORM is applicable for linear and nonlinear static problems. Strategies are proposed to circumvent and remedy potential challenges to FORM. In the case of dynamic problems, the application of FORM is studied with an emphasis on cumulative response measures. The limit-state surface is shown to have a closed and nonlinear geometric shape. Solution methods are proposed to obtain probability bounds based on the FORM results. In the application-oriented second area of research, at first, the probability of collapse of a reinforced concrete frame is assessed with nonlinear static analysis. By modelling the post-failure behaviour of individual structural members, the global response of the structure is estimated beyond the component failures. The final application is the probabilistic assessment of monetary loss for a high-rise shear wall building due to the seismic hazard in the Cascadia subduction zone. A 3-dimensional finite-element model of the structure with nonlinear material models is subjected to stochastic ground motions in the reliability analysis. The parameters for the stochastic ground motion model are developed for Vancouver, Canada. Monetary losses due to the damage of structural and non-structural components are included.

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The term “blue-sky eruption” (BSE) can be used to describe eruptions which are unexpected or have no detected precursory activity. Case study analyses indicate that they have a diverse range of characteristics and magnitudes, providing both direct and indirect hazards and occur in both under-developed and developed countries. BSEs can be a result of physical triggers (e.g. the lack of physically detectable precursors or a lack of understanding of the eruption model of the volcano), social triggers (such as an inadequate monitoring network), or a combination of the two. As the science of eruption forecasting is still relatively young, and the variations between individual volcanoes and individual eruptions are so great, there is no effective general model and none should be applied in the absence of a site-specific model. Similarly, as methods vary between monitoring agencies, there are no monitoring benchmarks for effective BSE forecasting. However a combination of seismic and gas emission monitoring may be the most effective. The United States began a hazard and monitoring review of their volcanoes in 2005. While the general principles of their review would be beneficial in a monitoring review of New Zealand’s volcanoes, differences in styles of volcanism, geographic setting and activity levels mean changes would need to be review to fully appreciate the risk posed by New Zealand’s volcanoes. Similarly, the monitoring benchmarks provided in the U.S. review may not be fully applicable in New Zealand. While advances in technology may ultimately allow the effective forecasting of some BSEs, the immediate threat posed by unexpected eruptions means that effective management and mitigation measures may be the only tools currently at our disposal to reduce the risks from BSEs.

On the 13th of March, 2007 a failure of the tephra dam at Te-wai-a-moe, the Crater Lake of Mt Ruapehu in the North Island of Aotearoa/New Zealand, caused a lahar to travel down the Whangaehu River channel. The lahar event had been predicted after an eruptive event at Mt Ruapehu eleven years before. As a result of the early prediction, the lahar event and potential risk was well studied, and twenty four management options were proposed to mitigate risk. After a period of consultation with stakeholders, including local iwi, the Minister for Conservation ratified a non-intervention option which emphasised monitoring and prohibited engineering intervention on the mountain. The media event associated with 2007 lahar event drew considerable attention to the 1953 Tangiwai tragedy which occurred following a similar lahar event at Mt Ruapehu. The 2007 lahar media event constructed Tangiwai as a site of risk that belonged to science, technology and Pakeha tragedy, dominating understandings of Tangiwai as an important spiritual place for local iwi and their relationship with Mt Ruapehu. The lahar event also highlighted the dominant western science based hazard management paradigm and its interactions with matauranga Maori. Inherent in the dominant western science paradigm is the natural/social split born of the scientific Enlightenment and the removal of non-humans as actors. Bruno Latour (2004) calls for a move beyond the natural/social dualism and recognition for the importance of non-humans in contesting and recreating worlds; this thesis considers Charles Royal’s tangata whenua paradigm as an answer to Latour’s call.

In this dissertation we present a novel computational method, as well as its software implementation, to compare two samples by a nonparametric likelihood-ratio test. The basis of the comparison is a mean-type hypothesis. The software is written in the R-language [4]. The two samples are assumed to be independent. Their distributions, which are assumed to be unknown, may be discrete or continuous. The samples may be uncensored, right-censored, left-censored, or doubly-censored. Two software programs are offered. The first program covers the case of a single mean-type hypothesis. The second program covers the case of multiple mean-type hypotheses. For the first program, an approximate p-value for the single hypothesis is calculated, based on the premise that -2log-likelihood-ratio is asymptotically distributed as ­­χ2(1). For the second program, an approximate p-value for the p hypotheses is calculated, based on the premise that -2log-likelihood-ratio is asymptotically distributed as ­χ2(p). In addition we present a proof relating to use of a hazard-type hypothesis as the basis of comparison. We show that -2log-likelihood-ratio is asymptotically distributed as ­­χ2(1) for this hypothesis. The R programs we have developed can be downloaded free-of-charge on the internet at the Comprehensive R Archive Network (CRAN) at http://cran.r-project.org, package name emplik2. The R-language itself is also available free-of-charge at the same site.

Seven and a half kilometers of high-resolution SH-wave seismic reflection profiles were collected across the Mt. Vernon graben, a 35 km by 3 km graben (bounded by the Wabash Island (WIF) and Hovey Lake faults (HLF)) in the southern Wabash Valley fault system (WVFS) of southern Indiana. Forty-six discrete faults were imaged that displaced Quaternary horizons in the vicinity of the WIF and HLF. The structural styles associated with faults include: 1) normal displacement, 2) reverse displacement and other compressional features, 3) varying magnitudes of slip along fault planes, and 4) different senses of slip along individual fault planes. Carbon 14 dating of displaced horizons suggests movement between approximately 26,000 and 42,000 YBP. The style and timing of Quaternary deformation within the WVFS, the close association of soil faults to documented post-Pennsylvanian bedrock faults (HLF and WIF), and focal mechanism studies of current seismicity in the Wabash Valley seismic zone are all direct evidence that the extensionally-formed faults of the WVFS are being transpressionally reactivated: a manner consistent with the current east-northeast westsouthwest regional compressive stress field.

The primary goal of the empirical research outlined in this thesis was to examine a number of the factors contributing to the design of more ergonomic multisensory warning signals, that is, signals that elicit efficient and effective responses from interface operators under demanding conditions. To achieve this goal, a series of experiments was conducted in order to examine the nature and consequences of the crossmodal links inherent in spatial attention between various different sensory modalities, such as audition, vision, and touch, in an applied setting. In particular, a laboratory-based simulated driving task was used to investigate the effectiveness of various different auditory and vibrotactile cues in orienting a driver's attention to potential emergency driving events seen through the front windscreen or rearview mirror. The results of the first set of auditory spatial cuing experiments highlighted a significant performance advantage when the target driving events occurred in the cued, rather than the uncued, direction, with the biggest benefits being seen following spatially-predictive auditory or verbal cues. The second set of vibrotactile spatial cuing experiments demonstrated the potential utility of vibrotactile warning signals for presenting spatial information to car drivers, and the results were successfully replicated in a study using a high-fidelity driving simulator. The third set of experiments, incorporating an orthogonal task design, were conducted in order to examine the mechanisms responsible for the advantageous spatial cuing effects reported in the earlier experiments. Taken together, the results demonstrated that while directional congruency between a warning signal and target driving event may be sufficient to facilitate performance due to the priming of the appropriate response, attentional facilitation (i.e., perceptual enhancement) typically requires the co-location of the cue and target within the same functional region of space. In sum, this thesis demonstrates the potential value of approaching the design of effective multisensory warning signals for human operators by studying the information processing mechanisms in the human brain. The findings outlined here add to the literature concerning the brain's differential representation of stimuli presented in peripersonal as opposed to extrapersonal space. Further experimental chapters detail experiments that examined verbal directional cuing, olfactory cuing, and crossmodal interactions in virtual haptic environments.