This thesis addresses a diverse range of topics in the area of probabilistic seismic risk analysis of engineering facilities. This intentional path of diversity has been followed primarily because of the relatively new and rapid development of this facet of earthquake engineering. As such this thesis focuses on the rigorous scrutinization of current, and in particular, simplified methods of seismic risk assessment; the development of novel aspects of a risk assessment methodology which provides easily communicated performance measures and explicit consideration for the many uncertainties in the entire earthquake problem; and the application of this methodology to case-study examples including structures supported on pile foundations embedded in liquefiable soils. The state-of-the-art in seismic risk and loss assessment is discussed via the case study of a 10 storey New Zealand office building. Particular attention is given to the quality and quantity of information that such assessment methodologies provide to engineers and stakeholders for rational decision-making. Two chapters are devoted to the investigation of the power-law model for representing the ground motion hazard. Based on the inaccuracy of the power-law model at representing the seismic hazard over a wide range of exceedance rates, an alternative, more accurate, parametric hazard model based on a hyperbola in log-log space is developed and applied to New Zealand peak ground acceleration and spectral acceleration hazard data. A semianalytical closed-form solution for the demand hazard is also developed using the hyperbolic hazard model and applied for a case-study performance assessment. The power-law hazard model is also commonly used to obtain a closed-form solution for the annual rate of structural collapse (collapse hazard). The magnitude of the error in this closed-form solution due to errors in the necessary functional forms of its constitutive relations is examined via a parametric study. A series of seven chapters are devoted to the further development of various aspects of a seismic risk assessment methodology. Intensity measures for use in the estimation of spatially distributed seismic demands and seismic risk assessment which are: easily predicted; can predict seismic response with little uncertainty; and are unbiased regarding additional properties of the input ground motions are examined. An efficient numerical integration algorithm which is specifically tailored for the solution of the governing risk assessment equations is developed and compared against other common methods of numerical integration. The efficacy of approximate uncertainty propagation in seismic risk assessment using the so-called First-Order Second-Moment method is investigated. Particular attention is given to the locations at which the approximate uncertainty propagation is used, the possible errors for various computed seismic risk measures, and the reductions in computational demands. Component correlations have to date been not rigorously considered in seismic loss assessments due to complications in their estimation and tractable methodologies to account for them. Rigorous and computationally efficient algorithms to account for component correlations are presented. Particular attention is also given to the determination of correlations in the case of limited empirical data, and the errors which may occur in seismic loss assessment computations neglecting proper treatment of correlations are examined. Trends in magnitude, distribution, and correlation of epistemic uncertainties in seismic hazard analyses for sites in the San Francisco bay area are examined. The characteristics of these epistemic uncertainties are then used to compare and contrast three methods which can be used to propagate such uncertainties to other seismic risk measures. Causes of epistemic uncertainties in component fragility functions, their evaluation, and combination are also examined. A series of three chapters address details regarding the seismic risk assessment of structures supported on pile foundations embedded in liquefiable soils. A ground motion prediction equation for spectrum intensity (found to be a desirable intensity measure for seismic response analysis in liquefiable soils) is developed based on ground motion prediction equations for spectral accelerations, which are available in abundance in literature. Determination of intensity measures for the seismic response of pile foundations, which are invariably located in soil deposits susceptible to liquefaction, is examined. Finally, a rigorous seismic performance and loss assessment of a case-study bridge structure is examined using rigorous ground motion selection, seismic effective stress analyses, and professional cost estimates. Both direct repair and loss of functionality consequences for the bridge structure are examined.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The Western Cape is one of the most seismically active regions in South Africa. It features geological properties which can develop earthquakes as large as 6.87 on the Richter scale. This poses a serious threat to all of the buildings that are currently located within this region. A recent study has found that typical three-storey Unreinforced Masonry (URM) buildings in the Cape Town area shows a high probability of failure or damage if subjected to such a large earthquake. Many of these buildings can be found in an area of Cape Town called the Cape Flats, housing approximately 11 000 individuals. The structural integrity of these buildings are of concern to engineers since it houses a number of individuals. The purpose of the study was to develop a risk assessment procedure that could be used to assess low-rise multi-storey (2, 3 and 4 storeys) URM buildings in order to determine where the risk of earthquake related damage would be the highest. The risk assessment procedure compared various characteristics regarding the buildings, residents, seismic attributes of the region and the recovery capability of the residents. The result, in the form of a risk rating, enabled the buildings to be prioritized according to their seismic risk. The aim was to develop a comparative model which could be applied to a range of buildings, indicating where the impact of an earthquake would be greatest. This result could then be used for further remedial action (such as retrofitting) where it is needed the most. The risk assessment procedure used an Earthquake Risk Assessment Model (ERAM) which was specifically developed to assess the earthquake risk of each building with the use of 26 factors. These factors would each be individually scored and through the ERAM model would produce a risk rating. The buildings' can then be ranked (prioritized) according to it's risk rating to determine where remedial actions or procedures are needed first. / AFRIKAANSE OPSOMMING: Die Wes-Kaap is een van die mees seismiese aktiewe streke in Suid-Afrika. Dit bevat geologiese eienskappe wat aardbewings met groottes van 6,87 op die Richterskaal kan laat ontwikkel (1 in 475 jaar herhaal periode). Dit hou 'n bedreiging vir baie die geboue wat tans in hierdie streek geleë is. 'n Onlangse studie het bevind dat tipiese drie-verdieping lasdraende steengeboue in die omgewing van Kaapstad 'n hoë waarskynlikheid van faling of skade toon as dit blootgestel word aan 'n groot aardbewing. Baie van hierdie geboue kan gevind word in 'n gebied van Kaapstad genaamd die Kaapse Vlakte, wat vir ongeveer 11 000 individue behuising bied. Die strukturele integriteit van hierdie geboue is van belang aangesien dit 'n groot aantal individue huisves. Die doel van die studie was om 'n risiko-evaluerings proses te ontwikkel wat gebruik kan word om multi-verdieping (2, 3 en 4 verdiepings) lasdraende steengeboue te evalueer ten opsigte van aardbewing verwante skade. Die risiko-evaluering proses vergelyk verskeie kenmerke van die geboue, die inwoners, seismiese eienskappe van die streek en die vermoë van die inwoners om terug te keer na hul alledaagse leefstyl. Die resultaat is in die vorm van 'n risiko-gradering, wat die gebruiker in staat stel om die geboue te prioritiseer volgens hul aardbewings risiko. Die doel was om 'n vergelykende model te ontwikkel wat toegepas kan word om 'n verskeidenheid van geboue te evalueer, en aan te dui waar die impak van 'n aardbewing die grootste sal wees. Hierdie resultaat kan dan gebruik word vir verdere remediërende optrede of prosedures soos versterkings. Die risiko-evaluerings proses gebruik 'n "Earthquake Risk Assessment Model" (ERAM) wat spesifiek ontwikkel is om die aardbewings-risiko van elke gebou te evalueer met die gebruik van 26 faktore. Hierdie faktore word elkeen individueel beoordeel en 'n risiko-gradering word verkry met behulp van die ERAM model. Die geboue kan dan geprioritiseer word volgens elkeen se risiko-gradering om te bepaal waar daar remediërende optrede nodig is.

The number of subsea production systems placed in deepwater locations in the Gulf of Mexico (GOM) has increased significantly in the last ten to fifteen years. Currently, API-RP2A (2000 a,b) designates the GOM as a low seismic zone, and thus does not require seismic effects to be considered during the design process. However, there have been a number of seismic events with Richter magnitudes between 3.0 and 4.9 that have occurred in this region. As a result, questions have been raised regarding the seismic performance of deepwater subsea systems. This thesis presents an analytical parametric study where a prototype subsea structure was selected based on a survey of subsea systems. The baseline analytical model consisted of a single casing embedded in soft clay soils, which supported a lumped mass at a cantilevered height above the soil. A number of the model characteristics were varied in the parametric study to simulate the structural response of a range of subsea structures. This thesis discusses the impact of API-RP2A Zone 1 and 2 design seismic demands for the performance of subsea structures. The results from the subsequent analyses show that the stresses and deflections produced by the Zone 1 and 2 peak ground accelerations fall within the allowable limits.

The number of subsea production systems placed in deepwater locations in the Gulf of Mexico (GOM) has increased significantly in the last ten to fifteen years. Currently, API-RP2A (2000 a,b) designates the GOM as a low seismic zone, and thus does not require seismic effects to be considered during the design process. However, there have been a number of seismic events with Richter magnitudes between 3.0 and 4.9 that have occurred in this region. As a result, questions have been raised regarding the seismic performance of deepwater subsea systems. This thesis presents an analytical parametric study where a prototype subsea structure was selected based on a survey of subsea systems. The baseline analytical model consisted of a single casing embedded in soft clay soils, which supported a lumped mass at a cantilevered height above the soil. A number of the model characteristics were varied in the parametric study to simulate the structural response of a range of subsea structures. This thesis discusses the impact of API-RP2A Zone 1 and 2 design seismic demands for the performance of subsea structures. The results from the subsequent analyses show that the stresses and deflections produced by the Zone 1 and 2 peak ground accelerations fall within the allowable limits.

No description available.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Peru is located in a high seismicity region, since is on the subduction zone between the tectonic plates of Nazca and South American, both belonging to the Pacific's Ring of Fire. Peru is a developing country, so it is of the utmost importance that the Peruvian Government is prepared to assist the thousands of casualties that may be in the face of an important seismic event. Hence seismic risk assessment of essential buildings such as schools and hospitals is necessary for structural reinforcement projects in this type of infrastructure. In this scientific article, it is shown how vulnerable the public schools of the district of San Juan de Miraflores in the city of Lima are to a seismic event. Hence FEMA P-154 Rapid Visual Screening methodology was used to assess actual condition of school infrastructure which can be used as refuge for casualties or local headquarters to emergency response. The results of the research conclude that most educational buildings present a high seismic risk and do not meet the requirements of post-earthquake use as required by the Peruvian Seismic Design Building Code.

Mississippi State University is one of the many public institutions in Mississippi located near a seismic hazard zone known as the New Madrid Seismic Zone (NMSZ). Previous studies reveal the possibility of damage to the campus during an earthquake is in the order of ten percent. Risk assessment for building structures on campus was carried out using HAZUS-MH MR3 software package, for several earthquake scenarios defined to replicate historic and hypothetical earthquake events.The study predicts peak ground accelerations of 0.09g to 0.2g relating to 0.67% to 4.28% building loss ratios respectively, which amounts to a loss of $8.2 million to $53 million. Wood and reinforced masonry buildings show significant resistance to earthquakes compared to concrete and unreinforced masonry buildings. The results of this study suggest that there is a considerable seismic risk to Mississippi State University buildings from a seismic event originating in NMSZ.

Seismic isolation systems are widely recognized as beneficial for protecting both acceleration- and displacement-sensitive nonstructural systems and components. Furthermore, adaptive isolation systems have been shown to enable engineers to achieve various performance goals under multiple hazard levels. These systems have been implemented for horizontal excitation, but there has been very limited research on isolation for vertical excitation. Thus, this paper seeks to evaluate the benefit of adaptive vertical isolation systems for component isolation, specifically for nuclear plants. To do this, three vertical isolation systems are designed to achieve multiple goals: a linear spring and a linear damper (LSLD), a linear spring and a nonlinear damper (LSND) and a nonlinear spring and a linear damper (NSLD). To investigate the effectiveness of the proposed systems, a stiff piece of equipment is considered at an elevated floor within a power plant. A set of 30 triaxial ground motions is used to investigate the seismic response of the equipment. The maximum isolation displacement and equipment acceleration are used to assess the effectiveness of the three isolation systems. While all systems significantly reduce the seismic accelerations on the equipment compared to the fixed-base case, a LSND system is shown to exhibit superior seismic performance across multiple hazard levels. / Thesis / Master of Applied Science (MASc)

This research employs a deterministic seismic risk assessment methodology to assess the potential damage and loss at meshblock level in the Christchurch CBD and Mount Pleasant primarily due to building damage caused by earthquake ground shaking. Expected losses in terms of dollar value and casualties are calculated for two earthquake scenarios. Findings are based on: (1) data describing the earthquake ground shaking and microzonation effects; (2) an inventory of buildings by value, floor area, replacement value, occupancy and age; (3) damage ratios defining the performance of buildings as a function of earthquake intensity; (4) daytime and night-time population distribution data and (5) casualty functions defining casualty risk as a function of building damage. A GIS serves as a platform for collecting, storing and analyzing the original and the derived data. It also allows for easy display of input and output data, providing a critical functionality for communication of outcomes. The results of this study suggest that economic losses due to building damage in the Christchurch CBD and Mount Pleasant will possibly be in the order of $5.6 and $35.3 million in a magnitude 8.0 Alpine fault earthquake and a magnitude 7.0 Ashley fault earthquake respectively. Damage to non-residential buildings constitutes the vast majority of the economic loss. Casualty numbers are expected to be between 0 and 10.

Dans le cadre de l'analyse et de la gestion intégrée des risques sismiques, deux approches sont proposées. La première, une méthode pseudo - adaptative de réponse modale (PSA), qui estime la réponse sismique des bâtiments à portiques, avec une précision acceptable et un temps de calcul et d'analyse réduit. En effet, dans le cadre de l'analyse de pushover multimodale (MPA), la courbe de capacité se construit sur la base d'une approche énergétique et le changement des propriétés modales après plastification est évalué à partir des vecteurs de déplacement pendant l'analyse de pushover. L'estimation des réponses en termes de déplacements absolus et relatifs, forces de cisaillement et rotations est satisfaisante comparativement aux résultats d'analyses non linéaires complètes. La seconde approche porte sur l'évaluation post-sismique des dommages structuraux à partir de dommages locaux observés. Elle est fondée sur une relation postulée entre le dommage et la probabilité résiduelle de ruine, à deux niveaux : l'étage et le bâtiment complet. Quatre portiques sont analysés et les résultats sont comparés à une approche mécanique qui estime l'endommagement du système à partir de la perte de raideur de la courbe de capacité. Les résultats obtenus montrent de bonnes estimations du niveau de dommage global. Ainsi, cette approche pourrait bien faire partie d'un outil d'aide à la décision dans le cadre des programmes d'évaluation urbaine des dommages qui requièrent des estimations simultanément rapides et précises / Within the overall framework of seismic risk analysis and management two approaches are presented. First, the Pseudo-Adaptive Uncoupled Modal Response Analysis (PSA) aims to provide improved estimates of seismic response for framed buildings, with an acceptable accuracy and a reduced calculation time duration. It relies on an energy-based equivalent displacement to develop the capacity curve and a pseudo-adaptive feature that considers changes in modal shapes after yielding, within the framework of the widely used Modal Pushover Analysis. According to the results, PSA is able to provide good estimates of structural responses such as displacements, storey drifts, shear forces and rotations, in comparison to a complete Nonlinear Time History Analysis. Second, a strategy for post-seismic evaluation of structural global damage is proposed on the basis of observed local damages and the postulation of adequate relationships between damage and residual probability of failure at two levels: a storey level prior to a building level. Three factors are proposed to reflect the influence of components damage at each of those levels. The obtained results appear as good predictions of the global damage. Accordingly, this strategy has the potential for being a first step within the implementation framework of a decision-making tool for rapid and accurate estimates of structural damages