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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Simplified Performance-Based Analysis for Seismic Slope Displacements

Astorga Mejia, Marlem Lucia 01 July 2016 (has links)
Millions of lives have been lost over the years as a result of the effects of earthquakes. One of these devastating effects is slope failure, more commonly known as landslide. Over the years, seismologists and engineers have teamed up to better record data during an earthquake. As technology has advanced, the data obtained have become more refined, allowing engineers to use the data in their efforts to estimate earthquakes where they have not yet occurred. Several methods have been proposed over time to utilize the earthquake data and estimate slope displacements. A pioneer in the development of methods to estimate slope displacements, Nathan Newmark, proposed what is now called the Newmark sliding block method. This method explained in very simple ways how a mass, in this case a rigid block, would slide over an incline given that the acceleration of the block surpassed the frictional resistance created between the bottom of the block and the surface of the incline. Because many of the assumptions from this method were criticized by scientists over time, modified Newmark sliding block methods were proposed. As the original and modified Newmark sliding block methods were introduced, the need to account for the uncertainty in the way soil would behave under earthquake loading became a big challenge. Deterministic and probabilistic methods have been used to incorporate parameters that would account for some of the uncertainty in the analysis. In an attempt to use a probabilistic approach in understanding how slopes might fail, the Pacific Earthquake Engineering Research Center proposed a performance-based earthquake engineering framework that would allow decision-makers to use probabilistically generated information to make decisions based on acceptable risk. Previous researchers applied this framework to simplified Newmark sliding block models, but the approach is difficult for engineers to implement in practice because of the numerous probability calculations that are required. The work presented in this thesis provides a solution to the implementation of the performance-based approach by providing a simplified procedure for the performance-based determination of seismic slope displacements using the Rathje & Saygili (2009) and the Bray and Travasarou (2007) simplified Newmark sliding block models. This document also includes hazard parameter maps, which are an important part of the simplified procedure, for five states in the United States. A validation of the method is provided, as well as a comparison of the simplified method against other commonly used approaches such as deterministic and pseudo-probabilistic.
2

Probabilistic Seismic Hazard Assessment For Earthquake Induced Landslides

Balal, Onur 01 January 2013 (has links) (PDF)
Earthquake-induced slope instability is one of the major sources of earthquake hazards in near fault regions. Simplified tools, such as Newmark&rsquo / s Sliding Block (NSB) Analysis are widely used to represent the stability of a slope under earthquake shaking. The outcome of this analogy is the slope displacement where larger displacement values indicate higher seismic slope instability risk. Recent studies in the literature propose empirical models between the slope displacement and single or multiple ground motion intensity measures such as peak ground acceleration or Arias intensity. These correlations are based on the analysis of large datasets from global ground motion recording database (PEER NGA-W1 Database). Ground motions from earthquakes occurred in Turkey are poorly represented in NGA-W1 database since corrected and processed data from Turkey was not available until recently. The objective of this study is to evaluate the compatibility of available NSB displacement prediction models for the Probabilistic Seismic Hazard Assessment (PSHA) applications in Turkey using a comprehensive dataset of ground motions recorded during earthquakes occurred in Turkey. Then the application of selected NSB displacement prediction model in a vector-valued PSHA framework is demonstrated with the explanations of seismic source characterization, ground motion prediction models and ground motion intensity measure correlation coefficients. The results of the study is presented in terms of hazard curves and a comparison is made with a case history in Asarsuyu Region where seismically induced landslides (Bakacak Landslides) had taken place during 1999 D&uuml / zce Earthquake.

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