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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.
1141

Assessment Of Seismic Hazard With Local Site Effects : Deterministic And Probabilistic Approaches

Vipin, K S 12 1900 (has links)
Many researchers have pointed out that the accumulation of strain energy in the Penninsular Indian Shield region may lead to earthquakes of significant magnitude(Srinivasan and Sreenivas, 1977; Valdiya, 1998; Purnachandra Rao, 1999; Seeber et al., 1999; Ramalingeswara Rao, 2000; Gangrade and Arora, 2000). However very few studies have been carried out to quantify the seismic hazard of the entire Pennisular Indian region. In the present study the seismic hazard evaluation of South Indian region (8.0° N - 20° N; 72° E - 88° E) was done using the deterministic and probabilistic seismic hazard approaches. Effects of two of the important geotechnical aspects of seismic hazard, site response and liquefaction, have also been evaluated and the results are presented in this work. The peak ground acceleration (PGA) at ground surface level was evaluated by considering the local site effects. The liquefaction potential index (LPI) and factor of safety against liquefaction wee evaluated based on performance based liquefaction potential evaluation method. The first step in the seismic hazard analysis is to compile the earthquake catalogue. Since a comprehensive catalogue was not available for the region, it was complied by collecting data from different national (Guaribidanur Array, Indian Meterorological Department (IMD), National Geophysical Research Institute (NGRI) Hyderabad and Indira Gandhi Centre for Atomic Research (IGCAR) Kalpakkam etc.) and international agencies (Incorporated Research Institutions for Seismology (IRIS), International Seismological Centre (ISC), United States Geological Survey (USGS) etc.). The collected data was in different magnitude scales and hence they were converted to a single magnitude scale. The magnitude scale which is chosen in this study is the moment magnitude scale, since it the most widely used and the most advanced scientific magnitude scale. The declustering of earthquake catalogue was due to remove the related events and the completeness of the catalogue was analysed using the method suggested by Stepp (1972). Based on the complete part of the catalogue the seismicity parameters were evaluated for the study area. Another important step in the seismic hazard analysis is the identification of vulnerable seismic sources. The different types of seismic sources considered are (i) linear sources (ii) point sources (ii) areal sources. The linear seismic sources were identified based on the seismotectonic atlas published by geological survey of India (SEISAT, 2000). The required pages of SEISAT (2000) were scanned and georeferenced. The declustered earthquake data was superimposed on this and the sources which were associated with earthquake magnitude of 4 and above were selected for further analysis. The point sources were selected using a method similar to the one adopted by Costa et.al. (1993) and Panza et al. (1999) and the areal sources were identified based on the method proposed by Frankel et al. (1995). In order to map the attenuation properties of the region more precisely, three attenuation relations, viz. Toto et al. (1997), Atkinson and Boore (2006) and Raghu Kanth and Iyengar (2007) were used in this study. The two types of uncertainties encountered in seismic hazard analysis are aleatory and epistemic. The uncertainty of the data is the cause of aleatory variability and it accounts for the randomness associated with the results given by a particular model. The incomplete knowledge in the predictive models causes the epistemic uncertainty (modeling uncertainty). The aleatory variability of the attenuation relations are taken into account in the probabilistic seismic hazard analysis by considering the standard deviation of the model error. The epistemic uncertainty is considered by multiple models for the evaluation of seismic hazard and combining them using a logic tree. Two different methodologies were used in the evaluation of seismic hazard, based on deterministic and probabilistic analysis. For the evaluation of peak horizontal acceleration (PHA) and spectral acceleration (Sa) values, a new set of programs were developed in MATLAB and the entire analysis was done using these programs. In the deterministic seismic hazard analysis (DSHA) two types of seismic sources, viz. linear and point sources, were considered and three attenuation relations were used. The study area was divided into small grids of size 0.1° x 0.1° (about 12000 grid points) and the PHA and Sa values were evaluated for the mean and 84th percentile values at the centre of each of the grid points. A logic tree approach, using two types of sources and three attenuation relations, was adopted for the evaluation of PHA and Sa values. Logic tree permits the use of alternative models in the hazard evaluation and appropriate weightages can be assigned to each model. By evaluating the 84th percentile values, the uncertainty in spectral acceleration values can also be considered (Krinitzky, 2002). The spatial variations of PHA and Sa values for entire South India are presented in this work. The DSHA method will not consider the uncertainties involved in the earthquake recurrence process, hypocentral distance and the attenuation properties. Hence the seismic hazard analysis was done based on the probabilistic seismic hazard analysis (PSHA), and the evaluation of PHA and Sa values were done by considering the uncertainties involved in the earthquake occurrence process. The uncertainties in earthquake recurrence rate, hypocentral location and attenuation characteristic were considered in this study. For evaluating the seismicity parameters and the maximum expected earthquake magnitude (mmax) the study area was divided into different source zones. The division of study area was done based on the spatial variation of the seismicity parameters ‘a’ and ‘b’ and the mmax values were evaluated for each of these zones and these values were used in the analysis. Logic tree approach was adopted in the analysis and this permits the use of multiple models. Twelve different models (2 sources x 2 zones x 3 attenuation) were used in the analysis and based on the weightage for each of them; the final PHA and Sa values at bed rock level were evaluated. These values were evaluated for a grid size of 0.1° x 0.1° and the spatial variation of these values for return periods of 475 and 2500 years (10% and 2% probability of exceedance in 50 years) are presented in this work. Both the deterministic and probabilistic analyses highlighted that the seismic hazard is high at Koyna region. The PHA values obtained for Koyna, Bangalore and Ongole regions are higher than the values given by BIS-1893(2002). The values obtained for south western part of the study area, especially for parts of kerala are showing the PHA values less than what is provided in BIS-1893(2002). The 84th percentile values given DSHA can be taken as the upper bound PHA and Sa values for South India. The main geotechnical aspects of earthquake hazard are site response and seismic soil liquefaction. When the seismic waves travel from the bed rock through the overlying soil to the ground surface the PHA and Sa values will get changed. This amplification or de-amplification of the seismic waves depends on the type of the overlying soil. The assessment of site class can be done based on different site classification schemes. In the present work, the surface level peak ground acceleration (PGA) values were evaluated based on four different site classes suggested by NEHRP (BSSC, 2003) and the PGA values were developed for all the four site classes based on non-linear site amplification technique. Based on the geotechnical site investigation data, the site class can be determined and then the appropriate PGA and Sa values can be taken from the respective PGA maps. Response spectra were developed for the entire study area and the results obtained for three major cities are discussed here. Different methods are suggested by various codes to Smooth the response spectra. The smoothed design response spectra were developed for these cities based on the smoothing techniques given by NEHRP (BSSC, 2003), IS code (BIS-1893,2002) and Eurocode-8 (2003). A Comparison of the results obtained from these studies is also presented in this work. If the site class at any location in the study area is known, then the peak ground acceleration (PGA) values can be obtained from the respective map. This provides a simplified methodology for evaluating the PGA values for a vast area like South India. Since the surface level PGA values were evaluated for different site classes, the effects of surface topography and basin effects were not taken into account. The analysis of response spectra clearly indicates the variation of peak spectral acceleration values for different site classes and the variation of period of oscillation corresponding to maximum Sa values. The comparison of the smoothed design response spectra obtained using different codal provisions suggest the use of NEHRP(BSSC, 2003) provisions. The conventional liquefaction analysis method takes into account only one earthquake magnitude and ground acceleration values. In order to overcome this shortfall, a performance based probabilistic approach (Kramer and Mayfield, 2007) was adopted for the liquefaction potential evaluation in the present work. Based on this method, the factor of safety against liquefaction and the SPT values required to prevent liquefaction for return periods of 475 and 2500 years were evaluated for Bangalore city. This analysis was done based on the SPT data obtained from 450 boreholes across Bangalore. A new method to evaluate the liquefaction return period based on CPT values is proposed in this work. To validate the new method, an analysis was done for Bangalore by converting the SPT values to CPT values and then the results obtained were compared with the results obtained using SPT values. The factor of safety against liquefaction at different depths were integrated using liquefaction potential index (LPI) method for Bangalore. This was done by calculating the factor of safety values at different depths based on a performance based method and then the LPI values were evaluated. The entire liquefaction potential analysis and the evaluation of LPI values were done using a set of newly developed programs in MATLAB. Based on the above approaches it is possible to evaluate the SPT and CPT values required to prevent liquefaction for any given return period. An analysis was done to evaluate the SPT and CPT values required to prevent liquefaction for entire South India for return periods of 475 and 2500 years. The spatial variations of these values are presented in this work. The liquefaction potential analysis of Bangalore clearly indicates that majority of the area is safe against liquefaction. The liquefaction potential map developed for South India, based on both SPT and CPT values, will help hazard mitigation authorities to identify the liquefaction vulnerable area. This in turn will help in reducing the liquefaction hazard.
1142

Field Investigations and Numerical Modeling of Earthquake and Tsunami Risk at Four Vulnerable Sites in Indonesia

Ashcraft, Claire E. 10 December 2021 (has links)
Maps and models of seismic and tsunami risk are constructed from a variety of measurements taken in Indonesia, which have the potential to reduce loss of life and infrastructure. The first study uses the multichannel analysis of surface waves (MASW) method to calculate the time-averaged shear wave velocity to 30 m depth (Vs30). These measurements were taken at 58 sites in the city of Pacitan, Java and on the islands of Lombok, Ambon, and the Banda Islands. Vs30 calculations are compared with local geologic maps to extrapolate site class for locations not measured directly. Site class maps are then compared with Modified Mercalli Intensity (MMI) observations for three earthquake events that impacted Lombok and Ambon to identify regions where the MMI and Vs30 do and do not corroborate one another. Consistent with other Vs30 studies, the lowest values are observed on coastal alluvial plains and the highest values on steeper hillsides underlain by volcanic deposits. The second study focuses on a potential sector collapse of the volcano Banda Api within the Banda Islands. A field survey of its summit identified a steeply dipping normal fault striking NNE-SSW. This, along with the fissure geometry of the volcano's most recent eruption, reveals a failure plane along which a future sector collapse could occur. The numerical model Tsunami Squares (TS) predicts that the tsunami produced by this landslide would inundate an estimated 63% of buildings on the Banda Islands with waves as high as 82 m. These findings highlight the importance of installing a GPS receiver array on Banda Api to monitor the motion of its slopes. The third study analyzes sediment from trenches on the Banda Islands and Ambon to test if historical tsunamis that have impacted the area are preserved in the geological record. Potential tsunami deposits were identified by the presence of marine sand and larger clasts of marine carbonate in an environment which otherwise lacks large storms to bring such material onshore. Several dating methods constrain the ages of at least seven candidate tsunami deposits found in trenches onshore. One of these historical tsunamis (the event of November 26, 1852) is described in significant detail from several locations across the Banda Sea, which enables modeling of the event using a Bayesian statistical approach. The posterior of this model predicts the most likely epicenter was SW of Seram with a mean magnitude of Mw 8.8. It also makes other predictions about fault parameters. The region exhibits a marked slip deficit based on instrumental records of earthquakes in the area.
1143

Análisis y diseño estructural de una torre de 40 pisos y 4 sótanos siguiendo normas peruanas incluyendo su desempeño sísmico en el distrito de Santiago de Surco, Lima / Analysis and structural design of a tower 40 stories and 4 basements following peruvian norms including its seismic performance in the district de Santiago de Surco, Lima

Fernández López, Rodrigo Miguel, Zapata Velásquez, Ricardo Timoteo 04 November 2019 (has links)
En la presente investigación se realiza el análisis y diseño estructural de una torre de 40 pisos y 4 sótanos de concreto armado siguiendo normas peruanas y el cálculo de su nivel de desempeño sísmico en el distrito de Santiago de Surco, Lima. Para esto, la hipótesis plantea que las normas peruanas cumplen con el desempeño sismorresistente deseado para esta torre alta. Para un entendimiento progresivo, primero se hará una descripción de la torre alta a estudiar, su arquitectura, suelo entre otros. En la segunda parte se dan los conceptos necesarios para comprender los tipos de análisis lineal estático, lineal dinámico y no lineal estático. Se definen los materiales, los diagramas momento – rotación para luego explicar la obtención de la curva de capacidad del edificio. Se tocan conceptos de desempeño y viento. En la tercera parte, se procede con en análisis sísmico usando las exigencias de sismorresistencia, también se hace el análisis por viento para finalmente comparar ambos efectos. En el capítulo cuarto se procede a hacer el diseño estructural usando las normas de concreto armado. En el capítulo cinco se hace el análisis por desempeño usando el método pushover para finalmente conseguir los resultados de este proyecto y a las conclusiones de este desarrollo. / In the present investigation, the analysis and structural design of a 40-story tower and 4 basements of reinforced concrete are carried out following Peruvian standards and the calculation of its level of seismic performance in the district of Santiago de Surco, Lima. For this, the hypothesis states that Peruvian standards comply with the seismic-resistant performance desired for this high tower. For a progressive understanding, first a description will be made of the tall tower to be studied, its architecture, ground among others. In the second part, the concepts necessary to understand the types of static linear, dynamic linear and static nonlinear analysis are given. The materials are defined, the moment - rotation diagrams and then explain the obtaining of the building capacity curve. Performance and wind concepts are touched. In the third part, we proceed with seismic analysis using the seismic resistance requirements, the wind analysis is also done to finally compare both effects. In the fourth chapter the structural design is done using the reinforced concrete standards. In chapter five the performance analysis is done using the pushover method to finally get the results of this project and the conclusions of this development. / Tesis
1144

Tsunamigenic potential of crustal faults in the southern Strait of Georgia and Boundary Bay

Caston, Megan 31 August 2021 (has links)
In this thesis, I constrain rupture scenarios of active crustal faults in the southern Strait of Georgia and Boundary Bay in order to assess their tsunamigenic potential. The NW-SE-trending Drayton Harbor, Birch Bay, and Sandy Point faults had been previously identified on the southern side of Boundary Bay from aeromagnetic, LiDAR, and paleoseismic data; all show evidence of abrupt vertical Holocene displacements. South of Boundary Bay, the E-W-trending Skipjack Island fault zone was recently mapped on the basis of multibeam sonar imagery and seismic reflection data, with evidence for Holocene offsets of the seafloor and subsurface sediments. In addition, the Fraser River Delta fault had been hypothesized on the basis of a line of pockmarks and fluid seeps. Since these faults have only been recently mapped and identified as active, there is little information available on their structure, rupture style, and past large earthquakes. This makes it difficult to constrain rupture models to predict how fault slip could displace the seafloor during a large earthquake, for input to tsunami models. I analyzed relocated earthquake hypocentres, earthquake mechanisms, bathymetry, topography, and aeromagnetic, seismic reflection, and magnetotelluric data, to constrain the location, strike, dip, and rupture width of each fault. Correlations between datasets enabled mapping of northwestward extensions of the Sandy Point and Birch Bay faults, as well as delineating the previously unmapped Fraser River Delta fault. These offshore faults appear to be associated with infilled basement valleys in the subsurface, perhaps due to differential glacial erosion of weakened fault zone material. The Drayton Harbor fault could not be definitively mapped across Boundary Bay, so was excluded from the rupture modelling. Rupture styles were constrained using a combination of earthquake mechanisms, stress orientations, other evidence of regional compression, and vertical paleoseismic offsets. Where possible, paleoseismic displacements in past earthquakes were used to constrain the amount of fault slip for scenario earthquakes; empirical relations between fault slip and fault length or area were used to estimate displacements for the Skipjack Island and Fraser River Delta faults. The Birch Bay, Sandy Point, Skipjack Island, and Fraser River Delta faults all pose a significant tsunami risk to communities surrounding the southern Strait of Georgia and Boundary Bay. Considering both the originally mapped and extended lengths, the Birch Bay and Sandy Point faults could rupture in reverse-faulting earthquakes up to Mw 6.7-7.4 and 6.8-7.5, respectively, with seafloor uplift up to 2-2.5 m triggering damaging tsunami waves (up to at least 2.5 m) that could arrive onshore with little to no warning after the shaking begins. Similarly, the Fraser River Delta fault could host reverse or dextral-reverse slip earthquakes up to Mw 7.0-7.6, with seafloor uplift of 0.6-3.5 m. Ruptures on the Skipjack Island fault would likely have a larger strike-slip component; earthquakes of Mw 6.9-7.3 produce modelled seafloor uplift of 0.5-1.9 m. These results suggest that large tsunamigenic earthquakes on crustal faults in the southern Strait of Georgia should be included in future seismic and tsunami hazard assessments on both sides of the international border. / Graduate
1145

Dynamická analýza konstrukce zatížená seismickým zatížením / Dynamic analysis of structure loaded seismic loads

Šulerová, Zdeňka January 2014 (has links)
This thesis deals with the calculation of response of reinforced concrete construction on the effect of seismic tension. Time and spectral analysis were made. They are mentioned as possible ways of calculation in EN 1998 - 1:2004 norm. Final figures of global deformations and stress on selected beam from the time and spectral analysis were firstly compared for the horizontal components of seismic stress affecting only in one direction. Subsequently comparison of time progress to combination of these effects mentioned in relevant norm was made. In the conclusion the results of used analysis are appraised.
1146

Dynamická analýza mostní konstrukce / Dynamic analysis of bridge construction

Kinclová, Radka January 2015 (has links)
The objective of this diploma thesis is a dynamic analysis of a cable-stayed walkway. The RFEM structural analysis software is used for the calculation. Design principles of the structure are explained and analysis of the construction phases is then performed. The eigenmodes of the structure are calculated for various material combinations. The thesis examines the effects of moving loads and earthquake effects using several different methods. A comparison of the various loading effects on the structure and also the calculation methods is presented at the conclusion.
1147

Nelineární dynamická analýza konstrukce zatížena seismickými účinky / Nonlinear dynamic analysis of structures with seismic loads

Navrátilová, Martina January 2015 (has links)
Diploma thesis compares the methods for the calculation of the response of structures with seismic loads. Linear and nonlinear analyses are used for the calculations. In the case of linear analysis response spectrum method is applied. For nonlinear analysis pushover method is used. These two methods are compared in programs AxisVM and RFEM on the examples of high-rise building and space frame.
1148

Dynamická analýza lehké mostní konstrukce / Dynamic analysis of lightweight bridge construction

Krzywoň, Filip January 2016 (has links)
The thesis compares the dynamic response of lightweight footbridge structure. Two finite element models were made. One in Ansys 15.0 software, and another in RFEM 5.05 structural software. The results of the models were compared to each other. The response to dynamic excitation from pedestrians was evaluated in accordance to ČSN EN 1990/A2.
1149

Analýza ocelových přípojů při seismickém zatížení / Seismic Design of Structural Steel Connections

Sotulář, Jiří January 2017 (has links)
The thesis deals with the analysis and standard check of structural steel connections subjected to seismic loads. Analysis is based on a software solution and standard check is performed according to standard requirements and formulas. The first part deals with the theory of seismic load. There are described the general knowledges about the earthquake and the method of determining the effects of seismic loading on buildings according to the EN 1998-1. In the second part of the thesis is made design and check seismically loaded multi-storey steel building. Design is based on recommendations of the EN 1998-1 and some recommendations of research. In the third part is the analysis, verification and check of steel joints, which are contained in the structure designed in the second part of the thesis. On the basis results of analyses of indivudual connections are defined recommendations and requirements for the use and design structural steel connections subjected to seismic loads.
1150

Caractérisation de la source des séismes par inversion des données sismologiques et géodésiques : mécanismes au foyer, optimisation des modèles de vitesse, distribution du glissement cosismique / Characterization of the seismic source by inversion of seismological and geodetic data : focal mechanisms, optimization of velocity models, coseismic slip distribution

Balestra, Julien 04 April 2017 (has links)
La caractérisation de la source d’un séisme se fait à partir de l’analyse des mesures des déplacements transitoires et statiques du sol, et dépend de la quantité et de la qualité de ces mesures. Nous avons travaillé sur la détermination des mécanismes au foyer des répliques du séisme de Saintes (MW 6.4, 2004), et sur la détermination de la distribution spatio-temporelle du glissement cosismique des séismes de L’Aquila (Mw 6.3, 2009), et de Miyagi-Oki (Mw 7.2, 2005) et de Sanriku-Oki (Mw 7.3, 2011). Ces travaux se sont basés sur des méthodes d’inversions, et différents jeux de données (accélérométriques, large-bandes, GPS et InSAR) accessibles ou non selon le séisme considéré. La seule diversité des mesures n’est pas suffisante pour décrire la rupture. La modélisation des données se confronte à des difficultés, comme par exemple la pertinence des modèles de vitesses sismiques pour la modélisation des données accélérométriques. Une autre problématique récurrente est la non-unicité de la meilleure solution déterminée par les méthodes d’inversions pour décrire les données. Pour répondre à ces deux problématiques, nous avons d‘une part développé une procédure d’exploration de modèles de vitesse pour déterminer les valeurs optimales capables de décrire au mieux les données accélérométriques du séisme de L’Aquila. D’autre part, nous avons développé une procédure de construction d’un modèle de source moyen que nous avons appliqué pour la détermination du glissement cosismique des séismes de L’Aquila, de Miyagi-Oki, et de Sanriku-Oki. L’ensemble de ces travaux et les réponses aux problèmes soulevés sont présentés dans ce travail de thèse. / Studies of the earthquake source are based on observations of seismic ground motions. They also depend on the quality and the density of measurements. In this present work we will present studies of the determination of focal mechanism of main aftershocks of the Les Saintes (MW 6.4, 2004) earthquake, and the determination of the coseismic slip of the L’Aquila (MW 6.3, 2009), the Miyagi-Oki (MW 7.2, 2005), ant the Sanriku-Oki (MW 7.3, 2011) earthquakes. These studies were based on two inversion methods. Different kinds of data were available (strong motion, broadband teleseismic, GPS and InSAR) depending on the earthquake studied. But the multiplicity of data is not sufficient to well describe rupture process. There are others difficulties as the data modeling of strong motion. Seismic velocity models are used to describe the characteristics of layers crossed by seismic waves. The quality of the modeling is depending on the pertinence of these seismic velocity models. The description of the rupture process is also depending on the non-uniqueness of the best solution given by global inversion methods. We propose two procedures in order to take into account these two classic issues. First, we developed a velocity model exploration procedure to obtain optimized 1D velocity models in order to improve the strong motion modeling of the L’Aquila earthquake. Then we developed a procedure to build an average rupture model from the combined results of several joint inversions, which was applied to the L’Aquila, the Miyagi-Oki, and the Sanriku-Oki earthquake. This thesis presents all these works and answers to the raised issues.

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