Dissertations / Theses on the topic 'SEISMIC CONDITION'

The demands of railway transport have been changing over the 150 years of existence of this type of transport in South Africa, specifically the performance requirements of the formation to cater for new traffic requirements. As such, it is important to assess the condition of this vital part of a railway track. This dissertation covers a research project conducted on two railway lines in which measurements of ground vibration were conducted in order to perform geophysical analysis and characterise the formation based on the results obtained. Measurements were taken on a 26 ton axle load track (Coal line, at Bloubank) and on a 20 ton axle load track (at Amandelbult) in South Africa. Planning and implementation of several test procedures to characterise track formation require considerable effort to minimize the impact on railway operations. Coupled with track occupation and the destructive nature of some of the test procedures, it is relevant to investigate alternative testing techniques to address the issues stated above. The use of surface waves for geotechnical characterization of sites is increasing worldwide. Applications to railway engineering have so far been limited to light load, high speed lines to minimize the use of poor geomaterials with reduced Rayleigh wave velocity. Four sites were identified where trains are operated at heavy loads, with the formation condition varying from poor to good. Seismic testing (geophysical) and conventional testing (deflection measurements) were performed at the identified sites. Seismic measurements were recorded using geophones as receivers, coupled to an amplifier and a computer. The source of the seismic events was the trains operating on the track and a hammer for impact testing. For the deflection measurements, the Remote Video Monitoring (RVM) technique was adopted. Dispersion analysis of the ground vibration experimental data was conducted using the multiple receiver method. The main conclusions reached with the analysis indicated that: __ Dispersion analysis had a good correlation with the formation deflection analysis; __ Phase velocity can be used as an indicator of the quality of a certain site; __ There are limitations when using trains as the energy source in terms of the generation of excitation frequency, which greatly reduces the phase velocity information in individual layers in the formation (i.e. wavelengths are not short enough).
Dissertation (MSc)--University of Pretoria, 2016.
Civil Engineering
MSc
Unrestricted

Marine seismic exploration is a method employed by the hydrocarbon industry to find geological structures in the sub-surface with the potential to contain trapped hydrocarbons. A source of seismic energy is towed behind a ship. The energy produced by the source propagates as a sound wave through the sea into the sub-surface. Within the sub-surface the energy is reflected, refracted and diffracted. The ship also tows an array of hydrophones behind the seismic source, and these are used to measure the wavefield. If the source signal is known, then the received signal at each hydrophone can be deconvolved for the source signal to obtain the impulse response of the earth between the source and the hydrophone. These impulse responses can highlight some of the structures in the subsurface. Maps of the subsurface built up from these impulse responses are then interpreted to estimate the locations of trapped hydrocarbons. The most commonly used seismic source is the seismic air gun, which is a canister containing highly compressed air. The air is released into the sea, forming an oscillating bubble. There are two methods used by industry to determine the signal produced by an air gun or air gun array: (1) modelling, and (2) extrapolation from near-field measurements. Traditionally, industry uses the first method. With broader bandwidth data that are being recovered in data processing by removing the sea-surface reflection at the source and receiver (source and receiver ghosts), it has been found that modelling is inferior to extrapolation from near field measurements, although industry has been slow to adopt the second method. Despite this change, modelling remains a valuable tool in the design of air gun arrays, where designs can be optimised by adjusting parameters of the array and using modelling to determine the wavefield of each variation of the array. The aim of this work is to develop methods which can improve on current air gun bubble modelling. In this thesis I develop a novel artificial boundary condition for use in finite volume simulations of oscillating bubbles. The purpose of the work is an improvement to the modelling of seismic air gun bubbles. However, the techniques presented in this thesis are not limited to air gun bubbles, but are applicable to any oscillating bubbles, or indeed any fluid dynamics problem which is spherical in nature, close to spherically symmetric, and produces flow speeds of low (< 0:1) Mach number some distance from the region of interest. The boundary condition is based on an existing approximation to the motion around a spherical bubble, which is derived from the asymptotic solution to the motion in the far field. It is applied as follows: (1) use the solution on the domain boundary to calculate the approximate solution external to the domain; (2) use the approximate external solution to calculate spatial derivatives of properties on the domain boundary, due to the external solution, and (3) use the spatial derivatives to describe characteristic waves incoming to the domain. I develop a finite volume scheme in which I apply this boundary condition. I present the results of one- and two-dimensional of simulations using this scheme, and demonstrate the efficacy of this boundary condition. The boundary condition performs well, allowing finite volume simulations of bubbles to be carried out for long run-times (5 105 time steps with a CFL number of 0:8) on highly truncated domains, in which the boundary condition may be applied within 0:1% of the maximum bubble radius. Conservation errors due to the boundary condition are found to be of the order of 0:1% after 105 time steps. One- and two-dimensional results show a third-order convergence rate of errors due to the boundary condition as the domain is enlarged. The one- and two-dimensional simulations of air gun bubbles I present are, to my knowledge, the first finite volume simulations of air gun bubbles carried out, and the first air gun bubble simulations in which the contents of the bubble are not considered to be homogeneous. Two-dimensional results show non-spherical aspects of air gun bubbles, which may be incorporated into models used by industry. The model captures surface instabilities, bubble translation and deformation due to gravity, and the formation of jets due to asymmetries on collapse. The results indicate that bubble surfaces are unstable throughout collapse. These phenomena are shown to increase the damping of bubble oscillations. The results of the two-dimensional air gun modelling highlight the potential value of my artificial boundary condition, and also the aspects of my computational scheme which require improvement. I extend the numerical scheme to include viscous effects, which I show to have limited impact on the signals emitted by air gun bubbles, although the influence of a boundary layer around the bubble is significant, causing an 18% reduction in rise rates. I extend the scheme to include the effects of the sea surface, and present results which show the impact of the reflection from the sea surface (the ghost wave) on the bubble. This extension shows the reflection of the ghost wave off the bubble, which provides a novel explanation of some of the higher frequencies present in measurements. This extension further increases the practical value of my contribution, and further demonstrates the ability of the boundary condition to handle asymmetrical flow features.

The best type of information about the Earth's interior is seismic. Seismic wave velocity depends on the value of the bulk modulus of the rock. The geophysicist Sir Harold Jeffreys derived a relation between temperature and bulk modulus for solids. From this, and the well known variation of velocity with bulk modulus for solids, we derived the variation of velocity for solids with temperature. We compared this relation to general data on rocks in order to test Jeffreys' predictions in our applications. Next, using the above relation as well as the well known relation between temperature and radius for an adiabatic Earth, we found the variation of bulk modulus with radius. This relation was then compared to actual values of the bulk modulus of the Earth in each major region.The variation of bulk modulus with radius should have been a close fit to the derived equation. This closeness of the fit would then be a measure of how close a region was too adiabatic conditions.The results of this study seem to indicate that the inner core and the outer core of the Earth seem to be near adiabatic conditions.
Department of Physics and Astronomy

Analytical and experimental studies of the behaviour of equipment vibration isolators under seismic conditions are presented. A preliminary parametric study of the effect of equipment-structure interaction on the ultimate equipment response of general equipment-structure systems is considered first. The results of this study indicate the conditions under which a non-interactive approach can yield adequate ultimate equipment response estimates. A model of a prototype air handling unit mounted on vibration isolators was constructed for use in the experimental studies. Two types of vibration isolators -elastomeric isolators and open spring isolators with uni-directional restraint - were tested under static and dynamic conditions. The frequency and seismic response characteristics of these vibration isolated systems were obtained. The experimental results indicate that the vibration isolators have nonlinear stiffness characteristics and high damping values. The results also show that the elastomeric isolators can survive a substantially higher level of base excitation than the open spring isolators with uni-directional restraint Analytical models of the vibration isolated systems, based on the model identification test results, have been formulated. A numerical procedure, utilizing time series analysis, was used to solve the equations of motion of the systems. Good agreement between the experimental results and the analytical results was observed. This study indicates that the analytical procedure can be used to accurately predict the response characteristics of vibration isolated equipment systems subjected to known base excitation inputs.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

Les Installations de Stockage de Déchets actuelles sont munies de barrieres de confinement composites géosynthétiques et minerales. En couverture, les interfaces entre composants de ces systèmes installés sur forte pente peuvent constituer des surfaces de glissement préférentiel. L'étude de ces interfaces est donc cruciale pour l'évaluation de la stabilité des barrières de ces installations. Le comportement de ces interfaces, en particuliers des interfaces géosynthétique - géosynthétique se révèle complexe: il va dépendre de la nature des polymères, de l'endommagement , de la vitesse de glissement relatif, de la température. Les conditions de chargement sont aussi primordiales, statiques ou dynamiques (cas de seisme). L'originalité du travail effectué dans le cadre de la présente étude tient d'abord aux dispositifs expérimentaux utilisés en parallèle, un Plan incliné et une Table Vibrante, les deux permettant de simuler les conditions réelles sur site, sous faible contrainte normale, en conditions d'une part statiques, d'autre part dynamiques. Des procédures d'essai nouvelles ont permis une interprétation fine des résultats d'essais. En particulier la variation du frottement en fonction de la cinétique d'essai est clairement démontrée, et le couplage des résultats obtenus dans les deux configurations d'essai permet de montrer que leur interprétation est complexe et ne peut se limiter à celle proposée par la norme européenne. En particulier, le niveau du déplacement relatif et la vitesse de déplacement influent significativement sur les résultats. Une étude spécifique de l'endommagement est aussi présentée
Modern landfills are equipped with multi-layered liners, including geosynthetic-geosynthetic and soil-geosynthetic interfaces. The interfaces represent weakness surfaces where the shear strength is a crucial aspect for the landfill stability. The behaviour of each interface can be different depending on the interactions of the materials in contact under the different load conditions (i.e. static and seismic loading). Nevertheless, the assessment of the geosynthetic interface shear strength can be difficult depending on different factors such as mechanical damage, time-dependent processes (ageing), stress dependent processes (such as repeated loading), coupled effects of both time and stress-strain dependent processes (creep or relaxation). In the present work, the static and the dynamic behaviour of typical geosynthetic - geosynthetic interfaces is investigated by means of the Inclined Plane and the Shaking Table tests since both devices permit to simulate experimental conditions close to them expected in landfill cover systems (low normal stress, small and large deformations). Two new test procedures are proposed and applied in order to assess the interface friction at both devices during all the phases of the tests. Taking advantage of the complementarity of both facilities, an innovative interpretation of test results considering the evolution of the shear strength parameters, passing from the static to the dynamic loading conditions, from small to large displacements is carried out. Furthermore, the dependence of the interface friction on different parameters such as the kinematic conditions, the normal stress and the mechanical damage is also investigated. In light of test results, it has been demonstrated that the variation of the interface friction could be significant, depending on the loading conditions (static or dynamic), on the actual kinematic conditions and on the level of deformation at which the interface is subjected

Although industrial piping systems and their components have been found highly vulnerable under earthquake events, there exists an inadequacy of proper seismic analysis and design rules for these structures. Current seismic design Standards and Codes are found to be over-conservative and some components, e.g., elbows, bolted flange joints and Tee joints, do not have detailed design guidelines that take into account earthquake loading. Thus, a clear need for the development of improved seismic design rules for such systems is evident. In this respect, numerical and experimental studies on piping systems and their components subjected to earthquake loading could be useful. As a result, valuable information, such as seismic capacities and demands under different limit states, could be utilized for the amendment of relevant design Codes and Standards. This thesis undertook a numerical and experimental investigation on a typical industrial piping system and some of its components in order to assess their seismic performance. In particular, the following issues have been pursued: (i) design of two non-standard Bolted Flange Joints (BFJs) suitable for seismic applications; (ii) experimental testing of the designed BFJs under monotonic and cyclic loading in order to check their leakage, bending and axial capacities; (iii) finite element analysis of a piping system containing several critical components under seismic loading; (iv) implementation of a pseudo-dynamic and real time testing schemes to test the piping system under seismic loading; and (v) pseudo-dynamic and real time tests on the piping system under several levels of earthquake loading corresponding to both serviceability and ultimate limit states. The above-mentioned activities were attained in this thesis. In particular, two different non-standard BFJs, comparatively thinner than the Standard ones, were designed, and their performance was examined through a number of monotonic and cyclic tests. Experimental results exhibited a favourable performance of the BFJs under bending and axial loading and moderate internal pressure; a good capacity in terms of strength, ductility, energy dissipation and leakage was observed. Performance of a typical full-scale industrial piping system containing several critical components, such as elbows, a bolted flange joint and a Tee joint, under realistic seismic loading was investigated through extensive numerical and experimental activities. The techniques of pseudo-dynamic and real time testing with dynamic substructuring –hybrid testing- were adopted to carry out experimental activities on the piping system under several limit state earthquake loading suggested by performance-based earthquake Standards. Implementations of hybrid tests were challenging mainly because the piping system was endowed with distributed masses and subjected to distributed earthquake forces, for which these experimental techniques have been considered inadequate so far. A number of mode synthesis techniques, namely the Craig-Bampton and SEREP methods, were discussed and their effectiveness was analysed for the realization of these tests. A characterization of the actuators to be used in the experimental tests was performed based on a transfer function. Relevant hybrid tests were successfully executed and they displayed a favourable performance of the piping system and its components; they remained below yield limits without any leakage even for the collapse limit state.

Although industrial piping systems and their components have been found highly vulnerable under earthquake events, there exists an inadequacy of proper seismic analysis and design rules for these structures. Current seismic design Standards and Codes are found to be over-conservative and some components, e.g., elbows, bolted flange joints and Tee joints, do not have detailed design guidelines that take into account earthquake loading. Thus, a clear need for the development of improved seismic design rules for such systems is evident. In this respect, numerical and experimental studies on piping systems and their components subjected to earthquake loading could be useful. As a result, valuable information, such as seismic capacities and demands under different limit states, could be utilized for the amendment of relevant design Codes and Standards. This thesis undertook a numerical and experimental investigation on a typical industrial piping system and some of its components in order to assess their seismic performance. In particular, the following issues have been pursued: (i) design of two non-standard Bolted Flange Joints (BFJs) suitable for seismic applications; (ii) experimental testing of the designed BFJs under monotonic and cyclic loading in order to check their leakage, bending and axial capacities; (iii) finite element analysis of a piping system containing several critical components under seismic loading; (iv) implementation of a pseudo-dynamic and real time testing schemes to test the piping system under seismic loading; and (v) pseudo-dynamic and real time tests on the piping system under several levels of earthquake loading corresponding to both serviceability and ultimate limit states. The above-mentioned activities were attained in this thesis. In particular, two different non-standard BFJs, comparatively thinner than the Standard ones, were designed, and their performance was examined through a number of monotonic and cyclic tests. Experimental results exhibited a favourable performance of the BFJs under bending and axial loading and moderate internal pressure; a good capacity in terms of strength, ductility, energy dissipation and leakage was observed. Performance of a typical full-scale industrial piping system containing several critical components, such as elbows, a bolted flange joint and a Tee joint, under realistic seismic loading was investigated through extensive numerical and experimental activities. The techniques of pseudo-dynamic and real time testing with dynamic substructuring –hybrid testing- were adopted to carry out experimental activities on the piping system under several limit state earthquake loading suggested by performance-based earthquake Standards. Implementations of hybrid tests were challenging mainly because the piping system was endowed with distributed masses and subjected to distributed earthquake forces, for which these experimental techniques have been considered inadequate so far. A number of mode synthesis techniques, namely the Craig-Bampton and SEREP methods, were discussed and their effectiveness was analysed for the realization of these tests. A characterization of the actuators to be used in the experimental tests was performed based on a transfer function. Relevant hybrid tests were successfully executed and they displayed a favourable performance of the piping system and its components; they remained below yield limits without any leakage even for the collapse limit state.

Over 7.8 km of seismic reflection data and 2 km of electrical resistivity data were acquired, processed, and interpreted during this multi-method geophysical study. Objectives included the definition of geologic conditions underlying a contaminant plume in McCracken County, western Kentucky, and the determination of the potential for structural control on the rate and direction of plume migration. Both geophysical methods indicate the presence of multiple high-angle normal faults outlining a series of asymmetric grabens ranging in width from 160 m to almost 300 m and striking between N40°E and N45°E. There was agreement between the two methods on fault location and degree of near-surface offset, with offsets of 1 to 2 m observed at 10 to 20 m below ground surface and 3 to 8 m observed at 20 to 30 m depth. Bedrock displacement was generally 2 to 3 times larger, with offsets of 10 to 26 m observed. The faults appear to have originated in the Paleozoic with predominantly normal reactivation occurring as recently as the Pleistocene. The fault strikes generally approximate the orientation of the northwestern contaminant plume. Observed offset of the Regional Gravel Aquifer may form a preferential flow path for contaminant migration.

Several studies were undertaken by various investigators during the last five decades to better understand the engineering behaviour of unsaturated soils. These studies are justified as more than 33% of soils worldwide are found in either arid or semi-arid regions with evaporation losses exceeding water infiltration. Due to this reason, the natural ground water table in these regions is typically at a greater depth and the soil above it is in a state of unsaturated conditions. Foundations of structures such as the housing subdivisions, multi-storey buildings, bridges, retaining walls, silos, and other infrastructure constructed in these regions in sandy soils are usually built within the unsaturated zone (i.e., vadose zone). Limited studies are reported in the literature to understand the influence of capillary stresses (i.e., matric suction) on the bearing capacity, settlement and liquefaction potential of unsaturated sands. The influence of matric suction in the unsaturated zone of the sandy soils is ignored while estimating or evaluating bearing capacity, settlement and liquefaction resistance in conventional engineering practice. The focus of the research presented in the thesis has been directed towards better understanding of these aspects and providing rational and yet simple tools for the design of shallow foundations (i.e., footings) in sands under both static and dynamic loading conditions. Terzaghi (1943) or Meyerhof (1951) equations for bearing capacity and Schmertmann et al. (1978) equation for settlement are routinely used by practicing engineers for sandy soils based on saturated soil properties. The assumption of saturated conditions leads to conservative estimates for bearing capacity; however, neglecting the influence of capillary stresses contributes to unreliable estimates of settlement or differential settlement of footings in unsaturated sands. There are no studies reported in the literature on how capillary stresses influence liquefaction, bearing capacity and settlement behavior in earthquake prone regions under dynamic loading conditions. An extensive experimental program has been undertaken to study these parameters using several specially designed and constructed equipment at the University of Ottawa. The influence of matric suction, confinement and dilation on the bearing capacity of model footings in unsaturated sand was determined using the University of Ottawa Bearing Capacity Equipment (UOBCE-2011). Several series of plate load tests (PLTs) were carried out on a sandy soil both under saturated and unsaturated conditions. Based on these studies, a semi-empirical equation has been proposed for estimating the variation of bearing capacity with respect to matric suction. The saturated shear strength parameters and the soil water characteristic curve (SWCC) are required for using the proposed equation. This equation is consistent with the bearing capacity equation originally proposed by Terzaghi (1943) and later extended by Meyerhof (1951) for saturated soils. Chapter 2 provides the details of these studies. The cone penetration test (CPT) is conventionally used for estimating the bearing capacity of foundations because it is simple and quick, while providing continuous records with depth. In this research program, a cone penetrometer was specially designed to investigate the influence of matric suction on the cone resistance in a controlled laboratory environment. Several series of CPTs were conducted in sand under both saturated and unsaturated conditions. Simple correlations were proposed from CPTs data to relate the bearing capacity of shallow foundations to cone resistance in saturated and unsaturated sands. The details of these studies are presented and summarized in Chapter 3. Standard penetration tests (SPTs) and PLTs were conducted in-situ sand deposit at Carp region in Ottawa under both saturated and unsaturated conditions. The test results from the SPTs and PLTs at Carp were used along with other data from the literature for developing correlations for estimating the bearing capacity of both saturated and unsaturated sands. The proposed SPT-CPT-based technique is simple and reliable for estimation of the bearing capacity of footings in sands. Chapter 4 summarizes the details of these investigations. Empirical relationships were proposed using the CPTs data to estimate the modulus of elasticity of sands for settlement estimation of footings in both saturated and unsaturated sands. This was achieved by modifying the Schmertmann et al. (1978) equation, which is conventionally used for settlement estimations in practice. Comparisons are provided between the three CPT-based methods that are commonly used for settlement estimations in practice and the proposed method for seven large scale footings in sandy soils. The results of the comparisons show that the proposed method provides better estimations for both saturated and unsaturated sands. Chapter 5 summarizes the details of these studies. A Flexible Laminar Shear Box (FLSB of 800-mm3 in size) was specially designed and constructed to simulate and better understand the behaviour of model surface footing under seismic loads taking account of the influence of matric suction in an unsaturated sandy soil. The main purpose of using the FLSB is to simulate realistic in-situ soils behaviour during earthquake ground shaking. The FLSB test setup with model footing was placed on unidirectional 1-g shake table (aluminum platform of 1000-mm2 in size) during testing. The resistance of unsaturated sand to deformations and liquefaction under seismic loads was investigated. The results of the study show that matric suction offers significant resistance to liquefaction and settlement of footings in sand. Details of the equipment setup, test procedure and results of this study are presented in Chapter 6. Simple techniques are provided in this thesis for estimating the bearing capacity and settlement behaviour of sandy soils taking account of the influence of capillary stresses (i.e., matric suction). These techniques are consistent with the methods used in conventional geotechnical engineering practice. The studies show that even low values of capillary stresses (i.e., 0 to 5 kPa) increases the bearing capacity by two to four folds, and the settlement of footings not only decreases significantly but also offers resistance to liquefaction in sands. These studies are promising and encouraging to use ground improvement techniques; such as capillary barrier techniques to maintain capillary stresses within the zone of influence below shallow foundations. Such techniques, not only contribute to the increase of bearing capacity, they reduce settlement and alleviate problems associated with earthquake effects in sandy soils.

Etude de petrologie experimentale sur les transformations a hautes pressions et hautes temperatures, de silicates et de germanates a structure olicine et pyroxene. Il a ete determine en fonction de la pression et de la temperature, la distribution du magnesium, du fer et du calcium entre mineraux mantelliques. Un modele thermodynamique coherent est construit et a permis de determiner le champ de stabilite de la perovskite silicatee et de proposer une interpretation de la discontinuite sismique des 670 km. Des mecanismes microscopiques de transformations de phase de l'olivine sont proposes. De quelques composes etudies par spectroscopie raman, a ete tire des parametres thermodynamiques harmoniques et anharmoniques de ces phases

Situated in an active tectonic region, Santiago de Chile, the country´s capital with more than six million inhabitants, faces tremendous earthquake hazard. Macroseismic data for the 1985 Valparaiso and the 2010 Maule events show large variations in the distribution of damage to buildings within short distances indicating strong influence of local sediments and the shape of the sediment-bedrock interface on ground motion. Therefore, a temporary seismic network was installed in the urban area for recording earthquake activity, and a study was carried out aiming to estimate site amplification derived from earthquake data and ambient noise. The analysis of earthquake data shows significant dependence on the local geological structure with regards to amplitude and duration. Moreover, the analysis of noise spectral ratios shows that they can provide a lower bound in amplitude for site amplification and, since no variability in terms of time and amplitude is observed, that it is possible to map the fundamental resonance frequency of the soil for a 26 km x 12 km area in the northern part of the Santiago de Chile basin. By inverting the noise spectral rations, local shear wave velocity profiles could be derived under the constraint of the thickness of the sedimentary cover which had previously been determined by gravimetric measurements. The resulting 3D model was derived by interpolation between the single shear wave velocity profiles and shows locally good agreement with the few existing velocity profile data, but allows the entire area, as well as deeper parts of the basin, to be represented in greater detail. The wealth of available data allowed further to check if any correlation between the shear wave velocity in the uppermost 30 m (vs30) and the slope of topography, a new technique recently proposed by Wald and Allen (2007), exists on a local scale. While one lithology might provide a greater scatter in the velocity values for the investigated area, almost no correlation between topographic gradient and calculated vs30 exists, whereas a better link is found between vs30 and the local geology. When comparing the vs30 distribution with the MSK intensities for the 1985 Valparaiso event it becomes clear that high intensities are found where the expected vs30 values are low and over a thick sedimentary cover. Although this evidence cannot be generalized for all possible earthquakes, it indicates the influence of site effects modifying the ground motion when earthquakes occur well outside of the Santiago basin. Using the attained knowledge on the basin characteristics, simulations of strong ground motion within the Santiago Metropolitan area were carried out by means of the spectral element technique. The simulation of a regional event, which has also been recorded by a dense network installed in the city of Santiago for recording aftershock activity following the 27 February 2010 Maule earthquake, shows that the model is capable to realistically calculate ground motion in terms of amplitude, duration, and frequency and, moreover, that the surface topography and the shape of the sediment bedrock interface strongly modify ground motion in the Santiago basin. An examination on the dependency of ground motion on the hypocenter location for a hypothetical event occurring along the active San Ramón fault, which is crossing the eastern outskirts of the city, shows that the unfavorable interaction between fault rupture, radiation mechanism, and complex geological conditions in the near-field may give rise to large values of peak ground velocity and therefore considerably increase the level of seismic risk for Santiago de Chile.
Aufgrund ihrer Lage in einem tektonisch aktiven Gebiet ist Santiago de Chile, die Hauptstadt des Landes mit mehr als sechs Millionen Einwohnern, einer großen Erdbebengefährdung ausgesetzt. Darüberhinaus zeigen makroseismische Daten für das 1985 Valparaiso- und das 2010 Maule-Erdbeben eine räumlich unterschiedliche Verteilung der an den Gebäuden festgestellten Schäden; dies weist auf einen starken Einfluss der unterliegenden Sedimentschichten und der Gestalt der Grenzfläche zwischen den Sedimenten und dem Festgestein auf die Bodenbewegung hin. Zu diesem Zweck wurde in der Stadt ein seismisches Netzwerk für die Aufzeichnung der Bodenbewegung installiert, um die auftretende Untergrundverstärkung mittels Erdbebendaten und seismischem Rauschen abzuschätzen. Dabei zeigt sich für die Erdbebendaten eine deutliche Abhängigkeit von der Struktur des Untergrunds hinsichtlich der Amplitude der Erschütterung und ihrer Dauer. Die Untersuchung der aus seismischem Rauschen gewonnenen horizontal-zu-vertikal-(H/V) Spektral-verhältnisse zeigt, dass diese Ergebnisse nur einen unteren Grenzwert für die Bodenverstärkung liefern können. Weil jedoch andererseits keine zeitliche Veränderung bei der Gestalt dieser Spektralverhältnisse festgestellt werden konnte, erlauben die Ergebnisse ferner, die Resonanzfrequenz des Untergrundes für ein 26 km x 12 km großes Gebiet im Nordteil der Stadt zu bestimmen. Unter Zuhilfenahme von Informationen über die Dicke der Sedimentschichten, welche im vorhinein schon durch gravimetrische Messungen bestimmt worden war, konnten nach Inversion der H/V-Spektralverhältnisse lokale Scherwellengeschwindigkeitsprofile und nach Interpolation zwischen den einzelnen Profilen ein dreidimensionales Modell berechnet werden. Darüberhinaus wurde mit den verfügbaren Daten untersucht, ob auf lokaler Ebene ein Zusammenhang zwischen der mittleren Scherwellengeschwindigkeit in den obersten 30 m (vs30) und dem Gefälle existiert, ein Verfahren, welches kürzlich von Wald und Allen (2007) vorgestellt wurde. Da für jede lithologische Einheit eine starke Streuung für die seismischen Geschwindigkeiten gefunden wurde, konnte kein Zusammenhang zwischen dem Gefälle und vs30 hergestellt werden; demgegenüber besteht zumindest ein tendenzieller Zusammenhang zwischen vs30 und der unterliegenden Geologie. Ein Vergleich der Verteilung von vs30 mit den MKS-Intensitäten für das 1985 Valparaiso-Erdbeben in Santiago zeigt, dass hohe Intensitätswerte vor allem in Bereichen geringer vs30-Werte und dicker Sedimentschichten auftraten. Weiterhin ermöglichte die Kenntnis über das Sedimentbeckens Simulationen der Bodenbewegung mittels eines spektralen-Elemente-Verfahrens. Die Simulation eines regionalen Erdbebens, welches auch von einem dichten seismischen Netzwerk aufgezeichnet wurde, das im Stadtgebiet von Santiago infolge des Maule-Erdbebens am 27. Februar 2010 installiert wurde, zeigt, dass das Modell des Sedimentbeckens realistische Berechnungen hinsichtlich Amplitude, Dauer und Frequenz erlaubt und die ausgeprägte Topographie in Verbindung mit der Form der Grenzfläche zwischen den Sedimenten und dem Festgestein starken Einfluss auf die Bodenbewegung haben. Weitere Untersuchungen zur Abhängigkeit der Bodenerschütterung von der Position des Hypozentrums für ein hypothetisches Erdbeben an der San Ramón-Verwerfung, welche die östlichen Vororte der Stadt kreuzt, zeigen, dass die ungünstige Wechselwirkung zwischen dem Verlauf des Bruchs, der Abstrahlung der Energie und der komplexen geologischen Gegebenheiten hohe Werte bei der maximalen Bodengeschwindigkeit erzeugen kann. Dies führt zu einer signifikanten Zunahme des seismischen Risikos für Santiago de Chile.

The purpose of this study is to assess the engineering geological and geotechnical characteristics and to perform seismic hazard studies of the Upper Pliocene to Quaternary (Plio-Quaternary) deposits located towards the north of Ankara through surface wave testing methods. Based on a general engineering geological and seismic site characterization studies, site classification systems are assigned in seismic hazard assessments. The objective of the research is to determine the regional and local seismic soil conditions (i.e., shear wave velocities, soil predominant periods and soil amplification factors) and to characterize the soil profile of the sites in this region by the help of surface geophysical methods. These studies have been supported by engineering geological and geotechnical field studies carried out prior to and during this study. By integrating these studies, local soil conditions and dynamic soil characteristics for the study area have been assessed by detailed soil characterization in the region. As a result, seismic hazard assessments have been performed for Ç
ubuk and its close vicinity with the aid of Geographical Information Systems (GIS) through establishing seismic characterization and local soil conditions of the area.

碩士
國立臺灣科技大學
營建工程系
106
As development continues, more and more tall apartment and office buildings are being built with basements that require slurry supported trenches for diaphragm wall construction. In the past, investigators have done studies into the stability of trenches. It was indicated that the trench stability analysis is a three dimensional problem due to arching effect from the finite length of the trenches. However, few studies have considered the seismic stability analysis of trenches. This thesis therefore aims to conduct research on the stability of slurry supported trenches under seismic conditions. However, it is not clear regarding its simulation conditions. In this study, finite element upper and lower bound limit analysis methods (LA) are used to study the stability of trenches under bentonite pressure in purely cohesive clay by considering seismic conditions and to produce stability charts to be used for preliminary by engineers.

With the occurrence of a number of earthquakes in the past and chances of many more in the future, seismic risk assessment has become a key factor in the seismic risk mitigation and management. Seismic design for structures has evolved with the passage of time and so has the complexities in design and construction. But Seismic design has its own limitations. Every type of structure deteriorates with time and becomes seismically vulnerable. Seismic vulnerability also depends a lot on the quality of construction and use of the structure. Also with the rapid rate of construction fulfilling the need of exploding population in developing countries like India, the number of buildings is increasing exponentially with small regard to seismic safety. Therefore a very rapid, reliable and economic method is required to roughly judge the seismic safety of buildings and Rapid Visual Screening of building structures appropriately serves the purpose. In the present work, various aspects of Rapid Visual Screening (R.V.S.) are considered. Rapid visual screening practices in US as per FEMA 154 and those in India are studied and an overview of the topic is developed. Later on efforts are made to devise a new more accurate and quicker RVS system for Indian conditions. This new modified system of RVS is proposed and explained in sufficient detail. Separate MS excel programs are developed for this new developed system and for RVS system specified by Bureau of Indian Standards (BIS) and using them screening of a certain number of buildings is carried out in the city of Lucknow (U.P.). Then finally the outcomes and results are stated, comparisons are made and utility and suitability of new developed RVS system is explained.

Sloshing is defined as the movement of liquid surface inside a tank. For sloshing, it is necessary to have a free surface of liquid. It encompasses a wide spectrum of problems in engineering interests. Study of sloshing phenomenon in water tanks is very vital during the event of earthquake because water tanks play a key role in relief operations after disasters. Thus, securing water for domestic purposes and fire control operations until the restoration of uninterrupted water supply is very important for disaster victims. During earthquakes, additional fluid pressure is exerted on the walls of the water tank. Therefore, a detailed analysis of the water storage tanks during seismic excitations is crucial for safe design of the water tanks. It is observed that water tanks that were inadequately designed suffered considerable damage in past earthquakes. In this study, a rectangular model of water tank is excited at its natural frequency for various conditions. The experimental programme included the study of the effect of various parameters on the sloshing behaviour of water inside the tank. Different levels of water inside the tank, location of baffle walls (used to moderate sloshing) inside the tank, type of baffle walls in terms of induced perforations inside them and the extent and placement of perforations of baffle walls where some parameters involved in the study. Results of the above mentioned parameters on the sloshing of water have been reported in this dissertation report. It is appreciated that study of these parameters may be useful in providing optimum designs of water tanks.

碩士
淡江大學
土木工程研究所
82
In this study, a preliminary investigation on hydraulic drawdown and seismic stability condition os an earth dam was presented. Theoretic srudies was conducted using finite element code FEADAM84 and hypervolic model in cooperation with laboratory triaxial data fram both drained and undrained tests. The stress destribution and stability variation along the dam were analyzed in the cases of 1. end of construction, 2. full reservoir condition, 3. rapid hydraulic drawdown and 4. seismic impaction. Effects on the seepage though the earth dam were neglected while the dynamic interactions were simulated by using pseudo-static analysis. The results of the study show that the general stability conditons at the end of construction and full reservoir condition as well as the individual case in rapid hydraulic drawdown and seismic impaction, are on the safe side. However, surface portion of the embankment may encount damage when seismic condition and hydraulic drawdown occur simultaneously.

碩士
國立中央大學
地球科學學系
107
Rock deformation experiments are utilized to investigate the frictional behaviors and the associated mechanism of a fault during earthquake nucleation and ruptures. In particular, rotary shear apparatuses, characterizing with the deformation of large displacement and high velocities, are allowed to determine the fault behavior and its mechanism operated during earthquake propagation. In general, incohesive materials (fault gouges) are the dominant component within a fault core. Therefore, the studying materials, including both natural and synthetic gouges, are widely utilized with rotary shear apparatuses. So far, experiments on gouges deformed at seismic rates are confined with Teflon rings and at low normal stresses (0.5 to 3 MPa), sometimes with the issues of gouge extrusion and chemical contamination. Here we develop a metal pressure vessel which allows to deform gouges at high normal stresses (up to 18 MPa) and at seismic rates and, importantly, without gouge and/or fluid extrusion. The results show (1) the resistance of the pressure vessel (metal-to-metal contact) is extremely low (friction coefficient≈0.02) and (2) similarity to the previously published data, suggesting the data of the pressure vessel is convincing. In particular, deformed at seismic rates, significantly different frictional behaviors of kaolinite between room humidity and water-saturated conditions are observed (small fracture and short dynamic weakening distance is observed under room humidity condition, and the opposite is observed under water-saturated condition). It suggests that under room humidity flash heating can rapidly increase temperature and facilitate frictional melting (thermal decomposition) on gouges to promptly reach steady state of friction. Instead, under water-saturated condition, because water can absorb frictional heat and be incompressible, flash heating is inhibited, displaying a large fracture energy and large dynamic weakening distance. The dynamic weakening is still unclear (fluid pressurization, thermal pressurization, or elastohydrodynamic lubrication) and further experiments are required for the determination. In summary, the designed pressure vessel could expand the experimental conditions and allows to enrich the understanding of fault (landslide) deformation.

Local soil conditions influence the characteristics of earthquake ground shaking and these effects must be taken into account when specifying ground shaking levels for seismic design. These effects are quantified via site response analysis, which involves the propagation of earthquake motions from the base rock through the overlying soil layers to the ground surface. Site response analysis provides surface acceleration-time series, surface acceleration response spectra, and/or spectral amplification factors based on the dynamic response of the local soil conditions. This dissertation investigates and compares the results from different site response methods. Specifically, equivalent-linear time series analysis, equivalent-linear random vibration theory analysis, and nonlinear time series analysis are considered. In the first portion of this study, hypothetical sites and events are used to compare the various site response methods. The use of hypothetical events at hypothetical sites allowed for the seismic evaluation process used in engineering practice to be mimicked. The hypothetical sites were modeled after sites with characteristics that are representative of sites in the Eastern and Western United States. The input motions selected to represent the hypothetical events were developed using the following methods: stochastically-simulated time series, linearly-scaled recorded time series, and spectrally-matched time series. The random vibration theory input motions were defined using: seismological source theory, averaging of the Fourier amplitude spectra computed from scaled time series, and a response spectrum compatible motion. All of the different input motions were then scaled to varying intensity levels and propagated through the sites to evaluate the relative differences between the methods and explain the differences. Data recorded from borehole arrays, which consist of instrumentation at surface and at depth within the soil deposit, are used to evaluate the absolute bias of the site response methods in the second portion of this study. Borehole array data is extremely useful as it captures both the input motion and the surface motion, and can be used to study solely the wave propagation process within the soil deposit. However, comparisons using the borehole data are complicated by the assumed wavefield at the base of the array. In this study, sites are selected based on site conditions and the availability of high intensity input motions. The site characteristics are then developed based on site specific information and data from laboratory soil testing. Comparisons between the observed and computed response are used to first assess the wavefield at the base of the array, and then to evaluate the accuracy of the site response methods.
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碩士
淡江大學
土木工程學系
90
To accomplish a sophisticated seismic analysis for Cable-Stayed bridges, it is essential to include not only the geometric nonlinearity resulting from the evident change in geometric appearance of structure bus also the material nonlinearity due to the significant deformation occurring in some regions of structural elements. Accordingly, in addition to taking the interaction of axial force and bending moment, in association with the geometric nonlinearity, into account, a degrading tri-linear model is chosen in this research to describe the relationship between moment and curvature, under each of three stress stages beginning separately from the initial application of the force to the cracking occurrence at the section, from the cracking occurrence to the yielding onset caused by flexural deformation and from the yielding onset to the trigger of ultimate strain at the outer fiber of the section. Since the seismic behaviors of the structure would be affected, significantly, by the interaction force between the tower foundation of the bridge and soil in the vicinity of it, an effective soil-structure interaction model would be adopted in the analyses. It is expected that seismic responses of Cable-Stayed bridge, due to the variation of soil property, tower proportion, input angle for seismic loading, ratio of vertical to horizontal component for the earthquake considered, obtained precisely in this way would be useful for the evaluation of structure safety.

The research activity carried out in PhD period focused on numerical modelling of the seismic response of soil embankments in near-source conditions. The interest on such a topic comes from the fact that in Italy and worldwide there are many large earth dams placed very close to active faults. In such conditions the seismic response of the structure could be affected by near-source phenomena. Worth mentioning are the case-histories of Conza Dam during the Irpinia 1980 earthquake and Campotosto reservoir during the 2009 Abruzzo earthquake. In the first case, the embankment was partially jeopardized by the seismic event, being the dam site very close to the source ( ≈ 10 km). In the latter case, the epicenters of several aftershocks following the April 6, 2009 main event migrated in the NW direction, just below the 315-million-m3 Campotosto reservoir. In those days, the authorities in charge of the dam safety acted completely unprepared to face the emergency, due to the lack of pre-arranged predictive/interpretative tools. The investigated research theme is quite new in the geotechnical field. It requires a detailed knowledge of basic seismological aspects to properly simulate the seismic source and wave propagation pattern to get the input motion exciting the site and the embankment. As regards the implications in the field of civil engineering, an important feature of near-source phenomena is ground-motion asynchronism. This means that two points placed not very far each other, i.e. at a distance comparable to the dimensions of strategic infrastructures - as dams, road embankments, or bridges - may undergo quite different motion at their base (even not accounting for site effects). In such a context, the proper characterization of the motion at the bedrock level may provide a better prediction of the structure response to seismic loadings. This issue is crucial for large earth-dams or embankments. If the points placed at the base of these structures experience very different seismic motions (as expected in near-source conditions) significant differential settlements and fractures of the embankment may occur, with the consequent reduction of structure safety. In the first chapter the peculiarities of the near source seismic propagation will be illustrated referring to a detailed literature review on such an issue. At the end of the chapter some preliminary numerical results will be provided on typical embankments and simplified source models. In the second chapter, the mathematical formulation of the DRM approach, will be provided. According to DRM it is possible to divide the problem at the site scale from the problem of seismic motion generation which consists in the simulation of the source and the seismic propagation until the site of interest. Once known the nodal displacements, it is possible to determine the effective nodal forces (Bielak et al., 2003) which represent in the second model (model 2) the actions due to the seismic source. In this research project it was developed a novel algorithm to export the stiffness matrix to be used for calculating the effective nodal forces at the interface of the detail model at the site scale. This procedure has been implemented in a commercial software based on finite difference method. In the third chapter the methodology to simulate the reference source mechanism (1980 Irpinia earthquake) and the propagating media on a "regional scale" will be illustrated. A quasi-deteministic approach will be used, in which the determination of the seismic motion generated by the fault will be reproduced by the use of the empirical Green's functions in the frequency domain (Discrete Wave Number Method, by Cotton & Coutant, 1997). The source model was reconstructed from numerous publications on 1980 Irpinia source mechanism (Westaway & Jackson, 1984; Westaway & Jackson, 1987; Bernard & Zollo, 1988; Bernard & Zollo, 1989; Cocco & Pacor, 1993). In the fourth chapter, the mathematical formulation necessary to solve the boundary value problem in the geotechnical field will be presented. Some constitutive models suitable to represent soil behaviour under cyclic loads will be briefly described. In the fifth chapter, the model at the "site scale" of DRM approach will be described. It includes an interesting case history of an earth dam that in the 1980 Irpinia earthquake suffered huge damage, probably just due to the near-source seismic propagation. With the input motion provided by the large DRM model (step I), the seismic response of Conza dam will be evaluated. Comparisons will be provided between the predicted response of the dam by the DRM procedure and the measured one, as interpreted by Brigante (2010). Finally, the main differences between the DRM approach developed during the PhD activity, and a more traditional one (where a unique input motion is adopted) will be highlighted and the engineering implications discussed.

碩士
國立臺灣大學
土木工程學研究所
104
From observation of previous earthquakes, site effect has a great influence on ground motions. In many earthquake-resistant design codes for buildings, the design ground motion would be specified according to the local site condition. To characterize the site condition, the average shear wave velocity of the upper 30 meter of the ground (Vs30) is often used. The stiff the site (e.g. rock) is, the higher the Vs30. To obtain the shear wave velocity, geophysical measurement (e.g suspension logging) can be performed. Although direct measurement of shear wave velocity is much more accurate, it may be costly and may not be possible for area with difficult access, proxies to estimate shear wave velocity can be used instead. In this research, different proxies (e.g. geology, slope, geomorphic features) are considered to develop inference models for estimation of Vs30 in Taiwan.

Understanding how populations are structured and how they use natural and anthropogenic spaces is essential for effective wildlife management. A total of 510 barren-ground (Rangifer tarandus groenlandicus), 176 boreal (R. t. caribou), 11 mountain woodland (R. t. caribou), and 39 island (R. t. groenlandicus x pearyi) caribou were tracked with satellite collars in 1993-2009 in the Northwest Territories, Nunavut, and northern Alberta. Using satellite location data and hierarchical and fuzzy cluster analyses, I verified that Cape Bathurst, Bluenose-West, Bluenose-East, Bathurst, Beverly, Qamanirjuaq, and Lorillard barren-ground subpopulations were robust; the Queen Maude Gulf and Wager Bay barren-ground subpopulations were distinct. Dolphin and Union island caribou formed one population; boreal caribou formed two distinct subpopulations. Females in robust subpopulations were structured by strong annual spatial affiliation; those in distinct subpopulations were spatially independent and structured by migratory connectivity, movement barriers, and/or habitat discontinuity. An east-west cline in annual-range sizes and path lengths supported the subpopulation structure identified for migratory barren-ground caribou. I analyzed satellite location data to determine parturition dates and activity periods for all caribou ecotypes. For parturition dates I found a north-south cline for boreal caribou, west-east cline for migratory barren-ground caribou, and ecotype and subspecies clines for boreal and barren-ground caribou. Based on annual changes in movement rates I identified eight activity periods for boreal and tundra-wintering, 10 for mountain woodland, and 12 for migratory barren-ground caribou. Based distribution and movements, boreal caribou avoided seismic lines during periods when females and calves were most vulnerable to predators or hunters. They crossed fewer seismic lines and travelled faster when they crossed them than expected. Caribou avoided areas ≤400 m from seismic lines where they could space away from them suggesting that they perceive these as risky areas. I defined secure habitats as areas that were >400 m from anthropogenic linear features. Population growth rates were higher in areas where they had access to secure unburned habitat and where most of that was in patches >500 km2. Critical habitat for boreal caribou is a habitat state that provides “security” from predation risk and facilitates the effectiveness of their anti-predator strategies.
Ecology

Seismic site response analysis allows an engineer to assess the effect of local soil conditions on the ground motions expected during an earthquake. In seismic site response analysis, an input ground motion on rock is propagated through a site specific soil column. The computed response at the surface is dependent on both the input ground motion and the soil properties that characterize the site. However, there is uncertainty in both the input ground motion and the soil properties, as well as natural variability in the soil properties across a site. To account for the uncertainty in the input ground motions, engineers use a suite of motions that are selected and scaled to fit a scenario input motion. This study introduces a semi-automated method to select and scale the input motions to fit a target input motion and its variability. The proposed method is intended to replace tedious trials of combinations by hand with combinations performed by a computer. However, as in the traditional selection methods, the final selection of the combination is done by the engineer.The effect of the selected ground motion combination on the computed surface response spectrum from the site response analysis, and its variability, was investigated in this study. The results show by using a combination with as few as five motions, the median surface response spectrum can be predicted with an error of 10%. Additionally, the manner used to scale the input motions does not impact the accuracy of the median surface response spectrum, as long as the median response spectrum of the input combination agrees with the target input response spectrum. However, if the standard deviation of the surface response spectrum is to be considered (e.g., to develop median plus one standard deviation spectra), a input combination of at least 20 motions is recommended and the combination must be scaled such that the standard deviation of the input combination matches the standard deviation of the input target spectrum. Monte Carlo simulations were used to assess the impact of soil property variability on surface spectra computed by seismic site response. The results from this study indicate that by accounting for the variability of the shear-wave velocity profile of a site can cause a significant decrease in the median surface response spectrum, as well as a slight increase in the standard deviation of the surface response spectrum at periods less than the site period. By considering the variability of the nonlinear properties (shear modulus reduction and damping ratio) the median response spectrum decreased only slightly, but the standard deviation increased in a manner similar to the increase observed when considering the variability of the shear-wave velocity profile. Simultaneously considering the variability of the shear-wave velocity profile and nonlinear properties resulted in a median surface response spectrumsimilar to the median surface response spectrumcomputed with considering the variability of the shear-wave velocity alone. However, the standard deviation of the surface response spectrum was larger than the standard deviation computed by independent consideration of the variability of the shear-wave velocity or nonlinear properties.

博士
國立臺灣大學
土木工程學研究所
88
The objective of this research is to investigate the dynamic interactions between high-speed trains and railway bridges. In the investigation, the train is simplified as a series of identical vehicles, the track structure as a pair of continuous rails lying on a Winkler medium and the bridge as a simply supported beam. Three types of rail element, i.e., the CFR, LSR and RSR elements, that can account for the finite/infinite nature of the element ends are derived for modelling the continuous and infinite rail-Winkler foundation system. By using the Newmark difference scheme to discretize the vehicle equations, the contact forces can be solved in terms of the unknown responses of the contact points. Based on the concept of consistent nodal loads, the contact forces are substituted into the equations of motion of the rail element to yield a vehicle-rail interaction (VRI) element, which enables us to compute the vehicle response, contact forces and bridge response with no iterations required. The dynamic characteristics of the train-railway bridge system in the two- and three-dimensional spaces are then studied comprehensively by the use of the developed vehicle-rail-bridge interaction (VRBI) models. Track irregularity with random nature is considered in the analysis to reflect the actual situations. The effects studied include impact responses for bridges due to different train speeds, support reaction caused by trains in braking, stability of trains travelling over bridges, responses induced by two trains in crossing, and so on. In addition, the response and stability of trains resting on and moving over railway bridges shaken by earthquakes are investigated by using the generalized VRBI model with the inclusion of the effects of ground motions. It is indicated that the seismic analysis of the railway bridge carrying a train in motion requires not only information on ground acceleration, but also on ground velocity and displacement induced by earthquakes. Two representative ground motions collected during the 1999 Chi-Chi Earthquake are adopted as the input excitations. Based on the indices and criteria for derailment, the relations between the maximum allowable train speed and the peak ground acceleration (PGA) of the two ground motions are established, which can serve as a useful preliminary guide to safety operation of trains under earthquakes.

碩士
國立宜蘭大學
土木工程學系碩士班
105
Earthquakes bring damages to slopes and affect their safety. Therefore, geosynthetic reinforced soil retaining structures (GRSRS) are used commonly in geotechnical engineering to strengthen slopes. The features of GRSRS contain easy construction, short project duration, and high resistance to stress and earthquake. Consequently, conventional gravity retaining structures are thus being gradually replaced by GRSRS. In order to understand the seismic response of GRSRS influenced by earthquake, this study uses actual recorded seismic data from an earthquake monitoring system for the GRSRS built in FoGuang University. The seismic response simulation is then followed by employing the finite element program PLAXIS dynamic analysis. The predicted results of the seismic analysis show that the maximum acceleration increases with the elevation of the slope during the earthquake. The predicted results provide the ratios of the maximum accelerations for the top layer and middle layer to the bottom layer as 2.0 and 1.4, which is only about 4% difference between the monitored data and simulation predictions. This study attempts to explore the effects of earthquakes on GRSRS with the aid of dynamic numerical simulation. The boundary conditions and material damping are discussed comprehensively. This study implements the finite element program PLAXIS to simulate the seismic responses of the geosynthetic reinforced slope. Since the reflection of seismic input wave may affect the dynamic simulation, boundary conditions provided in PLAXIS must be able to simplify and ensure the calculation accuracy. Applicable boundary conditions for the geosynthetic reinforced slope may be retrieved using the free-field and viscous boundaries for the dynamic simulation analysis to enhance the accuracy. Furthermore, it is necessary to apply appropriate material damping for dynamic response analysis if one wants to analyze the loss of energy correctly in the soil mass. Otherwise, the whole geosynthetic reinforced slope system will continue to produce vibration. In the PLAXIS finite element program, the soil damping method is considered by Rayleigh Damping. Rayleigh damping makes the soil more realistic and the simulation results more accurate under seismic conditions. The seismic monitored data of this study are the actual information and make the dynamic predicted results of the numerical simulation for geosynthetic reinforced slope practical. It is suggested to conduct the dynamic simulation process with free field boundary and 5.5% damping ratio in PLAXIS. Based on the predicted results obtained from the seismic simulation, it is found that the maximum acceleration on surface area of the geosynthetic reinforced slope is obviously enlarged with the elevation increasing during earthquake. However, inside the reinforced area as well as the inner part of soil layer, the seismic amplification behavior with height is significantly reduced.

碩士
逢甲大學
土木工程學系
104
Currently, the Ministry of Education has spent NT $40 billion on conducting seismic retrofitting of school buildings. The purpose is to prevent school buildings from tilting or collapsing in major earthquakes in the future. In doing so, there will be a significant reduction in casualties of students and teachers due to earthquakes. Through the study of this paper, it is found that the current seismic retrofitting of school buildings is based on static pushover analysis or in-situ pushover test result. Therefore, the applicable conditions are limited to the similar situations of failure mode and pushover mode. However, in some of the images of destructions caused by tilting and collapsing from the 921 earthquake in Jiji and 1022 earthquake in Chiayi, it was found that destructions caused by tilting and collapsing occurred only locally. Moreover, the actual failure mode and the pushover mode of most school buildings are not the same. The results of this study showed that the failure mode of school buildings’ tilting and collapsing was due to the occurrence of shear bandings in some part of the underlying soil. Therefore, the bearing capacity safety factor of the foundation is greatly reduced to less than 1.0 in earthquakes. It is recommended that future seismic retrofitting of school buildings should be focused on ensuring the earthquake-bearing capacity’s safety factors of the foundation to meet regulatory requirements. Further retrofitting on structural elements such as columns, beams, boards, and walls should be conducted afterwards. This can ensure that the retrofitted school buildings will not be damaged from tilting or collapsing in major earthquakes in the future.

Tese de doutoramento em Construção Metálica e Mista, apresentada ao Departamento de Engenharia Civil da Faculdade de Ciências e Tecnologia da Universidade de Coimbra
This thesis deals with the numerical and analytical modelling of beam-to-column steel joints, when subjected to monotonic, cyclic or dynamic loading, addressing both the global response of the joint and the behaviour of the critical components. End-plate bolted connections are widely used in Europe, due to its attractive manufacturing and erecting costs and its easy integration into the building structure and architecture. Although their design for use in non-seismic regions is fully supported by the design rules in Eurocode 3, current seismic design codes, like the Eurocode 8, do not provide enough information or any design tools to allow their practical use also in seismic regions. The available procedure in the Eurocode 3 based on the Component Method, to characterize the joints behaviour, is only applicable for monotonically loaded joints. One main goal of this research is to contribute for the developing of an analytical design method, based on the component method, which considers the cyclic behaviour of the joints given by the proper contribution of each dissipative component, assuming that the adequate overstrength is assured for the non-dissipative components (capacity design). A further important goal of this research is to contribute to the development and improvement of displacement-based design procedures, proposing improved ductility-equivalent viscous damping relationships for steel moment-resisting framed (MRF) structures with dissipative beam-to-column partial-strength joints. In order to achieve the main goals proposed above, a calibrated parametric finite element (FE) model of a double extended beam-to-column end-plate steel joint is developed and calibrated with the available results of experimental work, also examined in here. The set of numerical models generated with the parametric script is developed in Python and use the software package ABAQUS. The main outputs of the research are: i) the detailed FE model that is capable of simulating, with accuracy, the behaviour of end-plate beam-to-column joints and its components; ii) the several detailed procedures proposed to isolate some of the most relevant and dissipative components that contribute to the joint behaviour, namely: column web panel in shear, column web in transverse tension and/or compression, column flange in bending and end-plate in bending; iii) the identification of the components’ mechanical behaviour in terms of force-displacement relationships by analysing the stress and deformation fields in the FE models, which can be used directly in a component based mechanical model of the joint; iv) improved ductility-equivalent viscous damping relationships (ductility-EVD), considering the influence of the several dissipative components involved in the double-extended end-plate joints, which can be used directly in procedures like the Direct Displacement-Based Seismic Design (Priestley et al., 2007). The proposed procedures to isolate the components behaviour are very flexible in terms of the definition of the integration boundaries; according to the mechanical model chosen. The procedure is able to capture the behaviour of the identified components, including the additional shear resistance provided by the transverse web stiffeners. The use of this stiffeners considerably affects the behaviour of the joints and its components. In the component end-plate in bending the inner bolt rows closer to the beam flanges present stable cycles without pinching, unlike the external rows, which clearly are affected by that phenomenon. The extraction of the components revealed also that the basic component column web panel in shear presented a stable behaviour for all stiffened joints. For the connection components, and in the presence of transverse web stiffeners, only the end-plate in bending significantly contributes to the joint non-linear rotation, with the other connection components response remaining in elastic domain. Concerning the evaluation of the ductility-equivalent viscous damping (ductility -EVD) relationships, conclusions are drawn about the limitation of using the existing expression proposed by Priestley et al. (2007), which generally overestimates the levels of equivalent viscous damping, for MRF structures with partial-strength joints. Furthermore, the numerical results obtained in the study revealed no clear dependency of the ductility-EVD relationships on the plastic mechanism of the joint type, on the elastic period of vibration of the system or on the soil type. An improved ductility-equivalent viscous damping relationship was derived and proposed.
Nesta tese aborda-se a caracterização do comportamento de juntas viga-coluna submetidas a carregamentos monotónicos, cíclicos ou dinâmicos, quer em termos de resposta global da ligação quer ao nível das componentes mais condicionantes. As ligações aparafusadas com chapa de extremidade são utilizadas com frequência na Europa, devido ao seu reduzido custo de fabrico e montagem, mas também devido à sua excelente integração arquitetónica. Apesar do seu dimensionamento estar perfeitamente definido no Eurocódigo 3 para zonas de baixa sismicidade, os mais recentes regulamentos sísmicos, como o Eurocódigo 8, não possuem informação detalhada nem providenciam as ferramentas para o dimensionamento deste tipo de ligações em zonas sísmicas. O procedimento de dimensionamento, baseado no Método das Componentes, presente no Eurocódigo 3 é apenas aplicável a ligações submetidas a carregamentos monotónicos. Um dos principais objetivos desta investigação é contribuir para o desenvolvimento de uma metodologia analítica, baseada no método das componentes, que tenha em conta o comportamento cíclico das juntas determinado pelo comportamento de cada uma das componentes dissipativas, e garantindo a adequada sobrerresistência das componentes não dissipativas. Outro importante objetivo desta investigação é o contributo para o desenvolvimento e evolução de procedimentos baseados em deslocamentos, propondo relações ductilidade-amortecimento viscoso equivalente melhoradas para pórticos simples que possuam ligações viga-coluna com resistência parcial onde a energia é dissipada. Para alcançar os objetivos desenvolveu-se um modelo paramétrico de elementos finitos (EF) de uma junta viga-coluna com chapa de extremidade duplamente estendida, calibrado e validado por resultados de ensaios experimentais, disponíveis na literatura. O conjunto de modelos numéricos é gerados através de um script desenvolvido em Python e compilado pelo software ABAQUS. Os principais resultados da investigação são: i) o modelo detalhada de EF capaz de simular eficazmente o comportamento de ligações viga-coluna de chapa de extremidade e os seus componentes; ii) os procedimentos desenvolvidos para a caracterização isolada dos componentes dissipativos que contribuem para o comportamento da junta, nomeadamente: painel da alma de coluna solicitada ao corte, alma de coluna em compressão transversal, alma de coluna em tração transversal, banzo de coluna em flexão e chapa de extremidade em flexão; iii) determinação do comportamento mecânico dos componentes através de curvas força-deslocamento, obtidas por integração de tensões e deformações no modelo de EF, que podem ser usadas diretamente em modelos mecânicos de componentes da ligação; iv) relações ductilidade-amortecimento viscoso equivalente (ductilidade-AVE) melhoradas tendo em conta a influência dos vários componentes dissipativos presentes nas ligações de chapa de extremidade duplamente estendida, e que podem ser usadas diretamente em procedimentos baseados em deslocamentos como o Direct Displacement-Based Seismic Design (Priestley et al., 2007). Os procedimentos propostos para aferir o comportamento isolado das componentes é bastante flexível na definição dos limites de integração, dependendo do modelo mecânico escolhido. O procedimento é capaz de caracterizar o comportamento das componentes identificadas na ligação, incluindo a resistência ao corte adicional devido à existência de reforços transversais na alma. A utilização deste tipo de reforços transversais afeta significativamente o comportamento da ligação e das suas componentes. No caso da componente chapa de topo em flexão as curvas força-deslocamento, associadas às fiadas de parafusos interiores junto aos banzos da viga, apresentam ciclos estáveis, ao contrário das curvas associadas às fiadas exteriores que são mais suscetíveis ao fenómeno de pinching. O comportamento do componente básico da alma de coluna solicitada ao corte apresenta um comportamento estável para todas as ligações reforçadas. Na presença de reforços transversais, à alma a componente chapa de extremidade em flexão apresenta um contributo significativo para a rotação da ligação. Ao contrário da componente banzo da coluna em flexão que se mantem em regime elástico. A determinação das relações ductilidade-AVE permitiu concluir sobre as limitações de usar a expressão proposta por Priestley et al. (2007), que geralmente sobrestima o nível de amortecimento viscoso equivalente para pórticos simples com ligações de resistência parcial. Os resultados numéricos permitiram ainda concluir que não existe uma clara dependência das relações ductilidade -AVE com os mecanismos plásticos da ligação, nem do período elástico de vibração do sistema, nem do tipo de solo. No final é proposta uma alteração à expressão existente para a relação ductilidade - amortecimento viscoso equivalente.

In this thesis the problem of identification of design earthquakes and seismic demand for performance based earthquake engineering (PBEE) is studied referring to far-field and near-source conditions. Ordinary probability seismic hazard analyses (PSHA), usually referred to far-field conditions, are the base of hazard evaluation of the most advanced seismic codes (e.g. Eurocode 8, 2006, CS.LL.PP. 2008, etc.). PSHA allows to identify for each considered site the probability of exceedance of different ground motion intensity measure (IM) levels in a time interval of interest: choosing a return period, and assuming as IM the elastic spectral acceleration at different structural periods, it is possible to build the uniform hazard spectrum (UHS); i.e., the response spectrum with a constant exceedance probability for all ordinates (Reiter, 1990); e.g., 10% in 50 years in the case of design for life-safety structural performance. UHS is not the only possible PSHA-based design spectrum (e.g., Baker 2011), but it is, to date, the most used basis for the definition of design seismic actions on structures. Recent studies are focused on the possibility of reducing uncertainties of PSHA analyses because it will produce a significant reduction of hazard values. Despite that, ordinary PSHA and UHS can be considered as a consolidated procedure which is not discussed here. If the seismic assessment of structures is carried out via non-linear dynamic analysis, knowledge of design response spectra is not enough and selecting the seismic input is seen to be one of the most critical issue which is sometimes considered more important even than structural modeling. In general, the signals that can be used for the seismic structural analysis are of three types: (1) artificial waveforms; (2) simulated accelerograms; and (3) natural records (Bommer and Acevedo, 2004). Spectrum-compatible signals of type (1) are obtained, for example, generating a power spectral density function from a code-specified response spectrum, and deriving signals compatible to that. However, this approach may lead to accelerograms not reflecting the real phasing of seismic waves and cycles of motion, and therefore energy. Simulation records (2) are obtained via modeling of the seismological source and may account for path and site effects but, they often require setting of some rupture parameters, such as the rise-time, which are hard to determine. Finally, of type (3) are ground-motion records from real events. The availability of on-line, user-friendly, databases of strong-motion recordings, and the rapid development of digital seismic networks worldwide, have increased the accessibility to recorded accelerograms, which, therefore, have become the most promising candidates for the seismic assessment of structures (Iervolino and Manfredi, 2008). In the code approach, selection of natural records has to identify a set compatible with the code-specified spectrum which should include implicitly information about the features of the seismogenic sources determining the seismic hazard at the construction site. Moreover, prudently, the practitioner is often required to also account explicitly for them: for example, Eurocode 8 states that accelerograms should be adequately qualified with regard to the seismogenetic features of the sources […]. In practical engineering application, accounting for seismological features of the sources is usually not compatible with information and/or ability of practitioners but, in accordance with probabilistic approach, for a given UHS, disaggregation of seismic hazard (Bazzurro and Cornell, 1999), for the exceedance return period and for the spectral ordinate of interest, allows to identify the contribution to the hazard of each seismological features considered in PSHA. Thus earthquakes dominating the hazard at the site (or design earthquakes) may be considered as the events characterized by the seismological features with the maximum contributions to the hazard (McGuire, 1995). In the first part of this work issues and findings related to identification of design earthquakes are taken to the Italian national level extending preliminary investigations of Convertito et al., 2009 which were referred to a case study region in the Southern Italy. In a recent work of Barani et al. (2009). disaggregation analyses of Italy were presented but different criteria for identification of design earthquakes were chosen. A large part of results obtained here can be considered independent from the specific sites considered and correlated to the typology of analyses: for example it is discussed how and why design earthquakes change with the spectral period (i.e., the dynamic characteristics of the considered structure), or why return period of seismic action may increase the hazard contribution of moderate events respect to the strong distant earthquakes. Moreover general trends of results for Italian sites are identified and a methodology for extracting one or more design earthquakes given disaggregation results is proposed and discussed. Finally, it is illustrated how these concepts may be easily included in engineering practice complementing design hazard maps and effectively enriching definition of seismic action with relatively small effort. The attention to the practical applicability of presented analyses is summarized in their implementation in an already existing and freely distributed software addressed to the code-based record selection (Iervolino et al., 2010 and Galasso et al. 2010). In the second part of the work, near-source conditions are considered analyzing the problem of rupture directivity effects. Generally speaking sites that are in a particular geometrical configuration with respect to the rupture may be reached contemporarily by seismic waves generated in different instant of time and velocity fault-normal signals may show a large pulse which occurs at the beginning of the record and contains the most of energy (Somerville et al., 1997). The results are waveforms different from ordinary ground motions recorded in the far field or in geometrical conditions not favorable with respect to directivity (Singh, 1985 and Reiter, 1990). Current attenuations laws are not able to capture such effect well but, unfortunately, it is believed that structures with dynamic behavior in a range of periods related to the pulse period may be subjected to underestimated seismic demand (Tothong and Cornell, 2006). So although directivity effects are known since many years to both seismologists and earthquake engineers, many aspects are still to be deepening. A systematic procedure for (i) analyzing resultant signals, (ii) studying structural effects and (iii) including these issues in hazard assessment is still far to be consolidated and as consequence, main European seismic codes do not account for the problem. In this work an attempt of improving each one of the previous points is presented. Regarding quantification of structural effects, a strong-motions’ American database, already classified in pulse-like and non pulse-like signals, is analyzed and three main characteristics of pulse-like records are outlined: (1) the elastic demand is generally larger than that of ordinary recordings, particularly concerning the fault-normal direction; (2) the spectral shape is non-standard with an increment of spectral ordinates in the range around the pulse period; (3) because the pulse period is generally a low frequency one (i.e., in the same order of magnitude of that of the most of common structures) the inelastic demand can be particularly high (Tothong and Luco, 2007) and developed in a comparatively short time which may facilitate fragile collapse mechanisms in structures not properly designed. Using previous results as benchmark, signals of the recent L’Aquila earthquake mainshock are analyzed investigating if directivity effects occurred. In particular, near-source records from the mainshock, rotated in fault-normal (FN) and fault-parallel (FP) directions, are analyzed extracting pulses with the same procedure used for the NGA dataset. Those found as likely containing velocity pulses were compared to: (1) those not identified as pulse-like; (2) the un-rotated components, and (3) to predictive models for the occurrence of directivity pulses and for the pulse period. The features of L’Aquila records were also compared to those of the NGA database to check whether they are in agreement to what expected for impulsive and non impulsive near-source records. The analyses include also rupture-rotated and vertical components of motion. Finally all the recent models regarding pulse-like effects (applied also in the analyses mentioned above) are used for a PSHA which is modified in order to account for near-source conditions (Iervolino and Cornell, 2008). Also disaggregation analysis is adapted to near source conditions as suggested by literatures (Thotong et al., 2007). Illustrative cases are analyzed: they can be considered as some of the first numerical applications of the most recent procedures and they are a way for identifying advantages and limits and for contributing to future improvements.

碩士
國立中興大學
土木工程學系所
102
Bridge from damaged serious foundation exposure caused by riverbed scour, lead to reduced seismic capacity of the bridge. If design of the bridge structure follow the Capacity Design Principle, so that the capacity of foundation higher than the column, and consider site species or replace the site type, will reduce damage to the bridge occurred when a natural disaster. 　　This study the soil-pile system with foundation exposure is idealized as a two-degree-of freedom system with an equivalent stiffness and damping ratio. Assume the lateral strength of the foundation is twice the lateral strength of the superstructure, and consider the impact strength reduction caused by the pile group effect, using the response spectrum analysis method to discuss the foundation - bridge system period due to changes resulting from bare foundation, and then evaluate the bridge model in the seismic exposed the different depth of the reaction. And quite soft, medium, hard three site type reactions, different sites to explore whether there is a critical scour depth of bridge foundation and their variations.

碩士
國立高雄第一科技大學
營建工程研究所
101
Nuclear electrical power has been a part of the power supply of Taipower Company in Taiwan. As the high-level radioactive waste has been produced during the generation of nuclear electrical power and endangering the human environment for a long period with its long half-life property, all the advanced countries using nuclear energy has widely accepted the Deep Geological Disposal method as the optimum one to permanently dispose the high-level radioactive waste after long-term research and discussion. In this research, the basic concept of the underground disposal site of Swedish KBS-3V was employed. The seismic measurements during the Japanese 311 earthquake, measured by HAGA which is one of 800 stations installed by National Ressarch Institute for Earth Science and Disaster Prevention, has been utilized as the geological conditions in Taiwan is quite similar to the ones in Japan. The numerical software, SAP90, was employed in the seismic analysis conducted in this research. The contents are composed of (1) the comparison of stress analyses using Eigen and Ritz methods, (2) the influence of stress distribution with various damping ratios and damping coefficients, and (3) the discussion of sensitivity analysis over the data obtained from the previous two studies. The analytical results found the following conclusions. The energy dissipation and damping effect became obvious if the damping coefficients increased when the disposal site was under earthquake. Only small change of the stresses in the whole disposal site was found for various damping ratio as the nonlinear damper were originally assumed for the selection of damping coefficients.

碩士
國立臺灣科技大學
營建工程系
107
For the past few decades, the slope disasters are often the issues for infrastructure protection. They can be caused by the earthquake, rainfall, and other human activities. Recently, the phenomenon is getting worse after Chi-Chi earthquake. The slope mass disturbance induced by earthquakes would be one of the factors. In addition to the earthquake effects, climate change as a result of global warming would be more an important problem (challenge) that civil engineers should face it from now on. Therefore, the attention of this study was paid to slope stability issue. According to the previous studies, Hoek-Brown failure criterion can provide better rock slope stability estimations than the conventional Mohr-Coulomb failure criterion. In addition, artificial intelligence (AI) technique brings the convenience for repetitive works and still maintain accuracy. The purpose of this study is to predict the rock slope stability and reliability by using three different concepts, namely as, Limit theorem, AI technique and Monte Carlo method for seismic rock slope stability problems.

碩士
朝陽科技大學
營建工程系碩士班
97
Since 1975 Freeman introduced a prototype model of the capacity spectrum method, Capacity Spectrum method has been widely used in the seismic assessment of reinforced concrete. This is especially true after Mahaney and others proposed ADRS format in capacity spectrum method in 1993. Over the years, there are many related researches by domestic researchers and yet seldom addressed the effect of the boundary modeling on the evaluation results. Therefore, through the case study of old engineering building at CYUT, the aim of this work is to investigate the degree of influence due to boundary modeling on the Seismic Capacity Evaluation. In this study, the lateral boundary conditions are modeled by walls, springs, and fixed supports , while the lower part of the boundary conditions, namely the foundations, are simulated as piles (members on elastic foundation), equivalent springs with soil stiffness, and rigid connections. Push-Over analyses are first carried out for various structural models with different boundary conditions at both lateral and foundation interfaces. Capacity curves can thus be obtained and converted to capacity spectra. Finally, corresponding acceleration of Seismic capacity can be determined by finding the maximum spectral acceleration or displacement of the spectra. The major findings based on the simulation results are as follows. For structures rested on normal to hard soil, the responses are so close to those associated with fixed supports that they can be modeled as fixed structures for simplicity. On the other hand, lateral boundary conditions significantly alter the result of seismic capacity on the target structure, and thus they are required to provide appropriate results. However, the results indicate that simulations based on shear wall elements and equivalent springs are more suitable selections since models with laterally rigid supports seem leading to over-estimated capacities

High-frequency wave phenomena is observed in many physical settings, most notably in acoustics, electromagnetics, and elasticity. In all of these fields, numerical simulation and modeling of the forward propagation problem is important to the design and analysis of many systems; a few examples which rely on these computations are the development of metamaterial technologies and geophysical prospecting for natural resources. There are two modes of modeling the forward problem: the frequency domain and the time domain. As the title states, this work is concerned with the former regime. The difficulties of solving the high-frequency wave propagation problem accurately lies in the large number of degrees of freedom required. Conventional wisdom in the computational electromagnetics commmunity suggests that about 10 degrees of freedom per wavelength be used in each coordinate direction to resolve each oscillation. If K is the width of the domain in wavelengths, the number of unknowns N grows at least by O(K^2) for surface discretizations and O(K^3) for volume discretizations in 3D. The memory requirements and asymptotic complexity estimates of direct algorithms such as the multifrontal method are too costly for such problems. Thus, iterative solvers must be used. In this dissertation, I will present fast algorithms which, in conjunction with GMRES, allow the solution of the forward problem in O(N) or O(N log N) time.
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