1181 |
Extracting and Aggregating Temporal Events from TextsDöhling, Lars 11 October 2017 (has links)
Das Finden von zuverlässigen Informationen über gegebene Ereignisse aus großen und dynamischen Textsammlungen, wie dem Web, ist ein wichtiges Thema. Zum Beispiel sind Rettungsteams und Versicherungsunternehmen an prägnanten Fakten über Schäden nach Katastrophen interessiert, die heutzutage online in Web-Blogs, Zeitungsartikeln, Social Media etc. zu finden sind. Solche Fakten helfen, die erforderlichen Hilfsmaßnahmen zu bestimmen und unterstützen deren Koordination. Allerdings ist das Finden, Extrahieren und Aggregieren nützlicher Informationen ein hochkomplexes Unterfangen: Es erfordert die Ermittlung geeigneter Textquellen und deren zeitliche Einordung, die Extraktion relevanter Fakten in diesen Texten und deren Aggregation zu einer verdichteten Sicht auf die Ereignisse, trotz Inkonsistenzen, vagen Angaben und Veränderungen über die Zeit. In dieser Arbeit präsentieren und evaluieren wir Techniken und Lösungen für jedes dieser Probleme, eingebettet in ein vierstufiges Framework. Die angewandten Methoden beruhen auf Verfahren des Musterabgleichs, der Verarbeitung natürlicher Sprache und des maschinellen Lernens. Zusätzlich berichten wir über die Ergebnisse zweier Fallstudien, basierend auf dem Einsatz des gesamten Frameworks: Die Ermittlung von Daten über Erdbeben und Überschwemmungen aus Webdokumenten. Unsere Ergebnisse zeigen, dass es unter bestimmten Umständen möglich ist, automatisch zuverlässige und zeitgerechte Daten aus dem Internet zu erhalten. / Finding reliable information about given events from large and dynamic text collections, such as the web, is a topic of great interest. For instance, rescue teams and insurance companies are interested in concise facts about damages after disasters, which can be found today in web blogs, online newspaper articles, social media, etc. Knowing these facts helps to determine the required scale of relief operations and supports their coordination. However, finding, extracting, and condensing specific facts is a highly complex undertaking: It requires identifying appropriate textual sources and their temporal alignment, recognizing relevant facts within these texts, and aggregating extracted facts into a condensed answer despite inconsistencies, uncertainty, and changes over time. In this thesis, we present and evaluate techniques and solutions for each of these problems, embedded in a four-step framework. Applied methods are pattern matching, natural language processing, and machine learning. We also report the results for two case studies applying our entire framework: gathering data on earthquakes and floods from web documents. Our results show that it is, under certain circumstances, possible to automatically obtain reliable and timely data from the web.
|
1182 |
Caracterização da subsuperfície rasa através da curva da razão espectral H/V e da inversão conjunta das curvas de dispersão e elipticidade / Near-surface characterization from the H/V spectral curves along with the joint inversion of the ellipticity and dispersion curvesUllah, Irfan 30 August 2017 (has links)
A destruição causada por um terremoto depende de muitos fatores, como características e profundidade da fonte, magnitude, distância epicentral e da configuração geológica da área. A destruição causada devido à configuração geológica da área é denominada como efeito local. A modelagem do efeito local implica na determinação do tempo e nível de vibração e do efeito de amplificação do deslocamento. As propriedades elásticas dos materiais geológicos (velocidade das ondas de compressão e de cisalhamento, densidade, espessura da camada de solo, etc.) podem ser obtidas por diversos métodos geofísicos. O conhecimento dessas propriedades elásticas ajuda a melhor projetar as infraestruturas e reduzir as chances de danos. Este procedimento é denominado de microzoneamento. Os parâmetros mais importantes para realizar o microzoneamento são as espessuras dos sedimentos que recobrem o embasamento e o perfil das velocidades das ondas S (cisalhamento). Esses dois parâmetros são adequadamente caracterizados pelo uso de várias técnicas geofísicas como perfilagens em furos de sondagem, reflexão e refração sísmica. Esses métodos geofísicos trazem algumas restrições como a necessidade da execução de um furo, emprego de fontes sísmicas artificiais que muitas vezes são dispendiosas e por vezes de uso restrito em áreas urbanas, além de muitas vezes estarem limitadas a investigações de apenas algumas dezenas de metros. Os métodos que substituíram esses métodos geofísicos convencionais nas últimas décadas são a análise do ruído sísmico produzido por fontes naturais e culturais. Este ruído sísmico ambiental pode ser registrado com menor custo e esforço e com boa cobertura lateral. Várias técnicas que se utilizam do ruído sísmico podem ser empregadas, no entanto, aquela que obteve maior atenção nos últimos anos é a técnica da razão do espectro horizontal sobre o espectro vertical da onda de superfície (H/V). A curva da razão espectral H/V é uma ferramenta rápida, fácil e de baixo custo para a caracterização da subsuperfície rasa. Existem vários estudos realizados sobre o tema que tentaram cobrir todos os aspectos e problemas associados ao método. Aqui neste estudo são aprofundados alguns aspectos ainda não avaliados em detalhe. Diferentes procedimentos para a modelagem e as associações entre os fenômenos físicos envolvidos e as características da curva H/V são discutidos e os resultados numéricos desses estudos são comparados com informações extraídas de perfis de sondagens de um dos locais estudados. O pico e a forma da curva H / V são modelados para encontrar o desvio na frequência de pico a partir da frequência de ressonância da onda de cisalhamento considerando diferentes campos de onda em torno do pico, assim como sua relação com a forma dominante da curva. A frequência de pico das curvas H/V é utilizada para estimar a relação entre a frequência a espessura através de análise de regressão. O estudo mostra que a curva de dispersão obtida a partir de um ensaio MASW pode ser usada para estimar a velocidade da onda S a um metro de profundidade e sua tendência de aumento com a profundidade. Esses valores podem ser usados para estimar a relação frequência-espessura para uma área. Esses resultados são comparados com a relação frequência-espessura derivada experimentalmente para a mesma área. A sensibilidade da forma da curva H/V à estrutura de velocidade do meio é analisada através de duas técnicas de modelagem (elipticidade da onda Rayleigh e campo difuso baseado na curva H/V). Diferentes partes da curva H/V são invertidas visando avaliar qual a parte da curva H/V contém as informações mais importantes sobre a estrutura subterrânea. As lições aprendidas dessas análises são aplicadas a três dados experimentais de locais distintos. As ondas Love podem contaminar o resultado da curva H/V. Duas técnicas diferentes para remover o efeito das ondas amorosas são discutidas. Em seguida, são discutidos os resultados da inversão conjunta das curvas de dispersão e da curva H/V após remoção do efeito da onda Love, ou seja, a curva de elipticidade. Alguns aspectos novos da técnica H/V são discutidos no final. / The destruction caused by an earthquake at a site depends on many factors like source characteristics such as magnitude, epicentral distance from the site, depth of the source, and on the geological setting of the area. The destruction caused due to the geological setting of an area is termed as site effect. To model the site effect of an area is to determine the shaking level longevity and its displacement amplification. The elastic properties (shear and compressional wave velocities, density, thickness of soil layer, etc.) of the site are required to find out by employing various geophysical procedures. The knowledge of these elastic properties help in better designing the infrastructure, which reduces the chances of destruction caused by a local geological setting due to an earthquake occurrence. This procedure is widely termed as microzonation. The most important parameters for the microzonation are the thickness of soft sediments over the seismic bedrock and its shear wave velocity profile. These two parameters are properly characterized by employing various geophysical techniques like borehole measurement, seismic reflection and seismic refraction. The conventional geophysical methods bring some hindrance to the picture such as, the drilling of a borehole and artificial seismic sources deployment for the reflection and refraction survey, which are both expensive and time consuming, difficult or even in some case impossible to implement in urbanized environment, the investigation is depth limited to few tens of meter. The methods which replaced this conventional geophysical method from the last decades or so is the analysis of Earth vibration caused by the seismic noise which is produced by both natural and cultural sources. This ambient seismic noise can be recorded with less cost and effort with good lateral coverage. Various seismic noise techniques are employed for this job; however, the one which got the most attention in recent years is the horizontal over vertical spectral ratio (H/V) technique. The H/V spectral ratio curve is a fast easy and cheap tool for the near-subsurface characterization. There are various study performed on the topic which has tried to cover almost all the aspects and problems associated with the method. Here in this study, we try to detail the aspects of this technique, which are not been evaluated fully. The different modelling procedures presented to model and physically link the H/V curve with some physical phenomenon will be discussed and its numerical result with the experimental H/V curve will be compared for a borehole test site. The peak and the shape of the H/V curve will be modelled to find its peak frequency deviation from the shear wave resonance frequency by considering different wave-field around the peak. Similarly, the shape dominancy of the H/V curve linkage will be find out. The peak frequency of the H/V curve is used to estimate the thickness-frequency relation by regression analysis. Here we will show that the dispersion curve obtained from multi-channel analysis of surface waves (MASW) can be used to estimate the velocity at one meter and the shear wave velocity increase trend with depth. These values can be used to estimate the thickness frequency relation for an area and its result will be compared with the experimentally derived thickness-frequency relationship for the same area. The sensitivity of the H/V curve shape to the subsurface velocity structure will find out for two main modelling techniques (Rayleigh wave ellipticity and diffused field based H/V curve). The different parts of the H/V curve are inverted (back modelled) to find out the part of H/V curve which is carrying the most important information about the subsurface structure. The lesson learned from all this analysis will be applied to experimental data of three different sites. The Love waves might contaminate the result of the H/V curve. Two different techniques to remove their effects will be discussed. Then, the joint inversion result of the dispersion and this Love effect removed H/V for more precisely ellipticity curve is discussed. Some new aspects of the H/V curve technique are also discussed at the end.
|
1183 |
Caracterização da subsuperfície rasa através da curva da razão espectral H/V e da inversão conjunta das curvas de dispersão e elipticidade / Near-surface characterization from the H/V spectral curves along with the joint inversion of the ellipticity and dispersion curvesIrfan Ullah 30 August 2017 (has links)
A destruição causada por um terremoto depende de muitos fatores, como características e profundidade da fonte, magnitude, distância epicentral e da configuração geológica da área. A destruição causada devido à configuração geológica da área é denominada como efeito local. A modelagem do efeito local implica na determinação do tempo e nível de vibração e do efeito de amplificação do deslocamento. As propriedades elásticas dos materiais geológicos (velocidade das ondas de compressão e de cisalhamento, densidade, espessura da camada de solo, etc.) podem ser obtidas por diversos métodos geofísicos. O conhecimento dessas propriedades elásticas ajuda a melhor projetar as infraestruturas e reduzir as chances de danos. Este procedimento é denominado de microzoneamento. Os parâmetros mais importantes para realizar o microzoneamento são as espessuras dos sedimentos que recobrem o embasamento e o perfil das velocidades das ondas S (cisalhamento). Esses dois parâmetros são adequadamente caracterizados pelo uso de várias técnicas geofísicas como perfilagens em furos de sondagem, reflexão e refração sísmica. Esses métodos geofísicos trazem algumas restrições como a necessidade da execução de um furo, emprego de fontes sísmicas artificiais que muitas vezes são dispendiosas e por vezes de uso restrito em áreas urbanas, além de muitas vezes estarem limitadas a investigações de apenas algumas dezenas de metros. Os métodos que substituíram esses métodos geofísicos convencionais nas últimas décadas são a análise do ruído sísmico produzido por fontes naturais e culturais. Este ruído sísmico ambiental pode ser registrado com menor custo e esforço e com boa cobertura lateral. Várias técnicas que se utilizam do ruído sísmico podem ser empregadas, no entanto, aquela que obteve maior atenção nos últimos anos é a técnica da razão do espectro horizontal sobre o espectro vertical da onda de superfície (H/V). A curva da razão espectral H/V é uma ferramenta rápida, fácil e de baixo custo para a caracterização da subsuperfície rasa. Existem vários estudos realizados sobre o tema que tentaram cobrir todos os aspectos e problemas associados ao método. Aqui neste estudo são aprofundados alguns aspectos ainda não avaliados em detalhe. Diferentes procedimentos para a modelagem e as associações entre os fenômenos físicos envolvidos e as características da curva H/V são discutidos e os resultados numéricos desses estudos são comparados com informações extraídas de perfis de sondagens de um dos locais estudados. O pico e a forma da curva H / V são modelados para encontrar o desvio na frequência de pico a partir da frequência de ressonância da onda de cisalhamento considerando diferentes campos de onda em torno do pico, assim como sua relação com a forma dominante da curva. A frequência de pico das curvas H/V é utilizada para estimar a relação entre a frequência a espessura através de análise de regressão. O estudo mostra que a curva de dispersão obtida a partir de um ensaio MASW pode ser usada para estimar a velocidade da onda S a um metro de profundidade e sua tendência de aumento com a profundidade. Esses valores podem ser usados para estimar a relação frequência-espessura para uma área. Esses resultados são comparados com a relação frequência-espessura derivada experimentalmente para a mesma área. A sensibilidade da forma da curva H/V à estrutura de velocidade do meio é analisada através de duas técnicas de modelagem (elipticidade da onda Rayleigh e campo difuso baseado na curva H/V). Diferentes partes da curva H/V são invertidas visando avaliar qual a parte da curva H/V contém as informações mais importantes sobre a estrutura subterrânea. As lições aprendidas dessas análises são aplicadas a três dados experimentais de locais distintos. As ondas Love podem contaminar o resultado da curva H/V. Duas técnicas diferentes para remover o efeito das ondas amorosas são discutidas. Em seguida, são discutidos os resultados da inversão conjunta das curvas de dispersão e da curva H/V após remoção do efeito da onda Love, ou seja, a curva de elipticidade. Alguns aspectos novos da técnica H/V são discutidos no final. / The destruction caused by an earthquake at a site depends on many factors like source characteristics such as magnitude, epicentral distance from the site, depth of the source, and on the geological setting of the area. The destruction caused due to the geological setting of an area is termed as site effect. To model the site effect of an area is to determine the shaking level longevity and its displacement amplification. The elastic properties (shear and compressional wave velocities, density, thickness of soil layer, etc.) of the site are required to find out by employing various geophysical procedures. The knowledge of these elastic properties help in better designing the infrastructure, which reduces the chances of destruction caused by a local geological setting due to an earthquake occurrence. This procedure is widely termed as microzonation. The most important parameters for the microzonation are the thickness of soft sediments over the seismic bedrock and its shear wave velocity profile. These two parameters are properly characterized by employing various geophysical techniques like borehole measurement, seismic reflection and seismic refraction. The conventional geophysical methods bring some hindrance to the picture such as, the drilling of a borehole and artificial seismic sources deployment for the reflection and refraction survey, which are both expensive and time consuming, difficult or even in some case impossible to implement in urbanized environment, the investigation is depth limited to few tens of meter. The methods which replaced this conventional geophysical method from the last decades or so is the analysis of Earth vibration caused by the seismic noise which is produced by both natural and cultural sources. This ambient seismic noise can be recorded with less cost and effort with good lateral coverage. Various seismic noise techniques are employed for this job; however, the one which got the most attention in recent years is the horizontal over vertical spectral ratio (H/V) technique. The H/V spectral ratio curve is a fast easy and cheap tool for the near-subsurface characterization. There are various study performed on the topic which has tried to cover almost all the aspects and problems associated with the method. Here in this study, we try to detail the aspects of this technique, which are not been evaluated fully. The different modelling procedures presented to model and physically link the H/V curve with some physical phenomenon will be discussed and its numerical result with the experimental H/V curve will be compared for a borehole test site. The peak and the shape of the H/V curve will be modelled to find its peak frequency deviation from the shear wave resonance frequency by considering different wave-field around the peak. Similarly, the shape dominancy of the H/V curve linkage will be find out. The peak frequency of the H/V curve is used to estimate the thickness-frequency relation by regression analysis. Here we will show that the dispersion curve obtained from multi-channel analysis of surface waves (MASW) can be used to estimate the velocity at one meter and the shear wave velocity increase trend with depth. These values can be used to estimate the thickness frequency relation for an area and its result will be compared with the experimentally derived thickness-frequency relationship for the same area. The sensitivity of the H/V curve shape to the subsurface velocity structure will find out for two main modelling techniques (Rayleigh wave ellipticity and diffused field based H/V curve). The different parts of the H/V curve are inverted (back modelled) to find out the part of H/V curve which is carrying the most important information about the subsurface structure. The lesson learned from all this analysis will be applied to experimental data of three different sites. The Love waves might contaminate the result of the H/V curve. Two different techniques to remove their effects will be discussed. Then, the joint inversion result of the dispersion and this Love effect removed H/V for more precisely ellipticity curve is discussed. Some new aspects of the H/V curve technique are also discussed at the end.
|
1184 |
Neotectonic and palaeoseismological studies in the southwest of Western AustraliaEstrada Roldan, Beatriz Elena January 2009 (has links)
[Truncated abstract] The southwest of Western Australia is an intraplate area classified as a stable continental region. It comprises predominantly Archaean and Proterozoic geology and has generally subdued topography. The region currently experiences significant seismicity in the Southwest Seismic Zone (SWSZ), which is one of the most seismically active areas in Australia and is thought to represent the highest seismic hazard of the region. In recent years, numerous scarps, potentially related to large palaeoearthquakes have been recognised not only within the SWSZ, but also in a broader region of the southwest of Australia. Palaeoseismological investigations of two of these scarps, the Dumbleyung and the Lort River scarps, confirm their association with surface-rupturing palaeoearthquakes and indicate events with likely maximum magnitudes of ~Mw 7.0 on faults of low to medium slip rates. Two trenches across the Dumbleyung Fault scarp revealed a thrust fault in alluvial sediments with two associated earthquakes in the last ca 24-60 ka. A possible Holocene age was recognised for the last recorded earthquake event exposed in these trenches. Two trenches across the Lort River Scarp show that this feature results from thrust faulting in the weathered gneissic country rock. These trenches exposed evidence of two events in the last ca 35 ka, with a likely late Pleistocene age for the last earthquake. On both sites, the earthquakes are interpreted as associated with the last phase of fault activity, which was likely been preceded by a long period of quiescence. Assessment of the earthquake hazard associated with large earthquakes at the Dumbleyung and Lort River Faults resulted in calculated peak ground accelerations of up to 2 g in the near-fault fields. Such earthquakes would significantly affect nearby towns such as Dumbleyung, Wagin, Katanning, and Esperance, but they are unlikely to cause any significant damage in Perth. The palaeoseismological investigations show that the earthquake activity in the southwest of Western Australia is not only confined to the SWSZ, as it has been considered in previous assessments of the seismic hazard, but that there is also potential for strong earthquakes across much of the region. The seismicity in the southwest of Western Australia appears to be transient and migratory. This is suggested by the lack of local relief associated with places of current seismicity and fault scarps, the widespread distribution of the fault scarps across the region, the increase in seismicity in the SWSZ following strong recent events, and the apparent long periods of earthquake recurrence at fault sites. Accordingly, the current seismicity in the SWSZ is inferred to be transient and probably associated with stress changes produced by the recent earthquakes. '...' This uplift could be associated with dynamic topography effects resulting from processes along the plate margins. The uplift is probably enhanced by a flexural response of the lithosphere to local differential loads and density contrast along the southern margin, a mechanism that may also help explain the occurrence of some earthquake activity. The results from this study, complemented by additional palaeoseismological studies must be included in future probabilistic assessments of the seismic hazard of the southwest of Western Australia.
|
1185 |
Αντισεισμικός σχεδιασμός γεφυρών σκυροδέματος με βάση τις μετακινήσεις / Dispacement-based seismic design of concrete bridgesΜπαρδάκης, Βασίλειος 25 June 2008 (has links)
Η πλειονότητα των ερευνητών/ειδικών του αντισεισμικού σχεδιασμού συμφωνεί πως μια υπολογιστική διαδικασία που θα έχει ως βασική παράμετρο της απόκρισης τις σεισμικές μετακινήσεις θα είναι πιο ορθολογική και πιθανότατα πιο οικονομική απ’ τη συμβατική μεθοδολογία σχεδιασμού βάσει δυνάμεων. Η έλλειψη μιας μεθοδολογίας αντισεισμικού σχεδιασμού γεφυρών βάσει μετακινήσεων που να είναι απλή, εφικτή και συμβατή με την εφαρμοζόμενη πρακτική και η απουσία πρότασης σχεδιασμού των περιοχών του φορέα βάσει μετακινήσεων, αποδεικνύει το γνωστικό κενό που υπάρχει σ’ αυτή την περιοχή του αντισεισμικού σχεδιασμού. Η παρούσα εργασία επιχειρεί να συμβάλλει στην πλήρωση αυτού του κενού και προς τούτο προτείνει μια νέα μεθοδολογία. Αναφέρεται σε (μή-μονωμένες) γέφυρες σκυροδέματος και περιλαμβάνει μια απλή διαδικασία για την εκτίμηση των απαιτούμενων ανελαστικών παραμορφώσεων, τόσο των βάθρων, όσο και των περιοχών του φορέα - κάνοντας χρήση ελαστικής φασματικής ανάλυσης και επεκτείνοντας τον κανόνα των "Ίσων Μετακινήσεων" στο τοπικό επίπεδο.
Η διαδικασία αναπτύσσεται και βαθμονομείται βάσει (σχεδόν δύο χιλιάδων) μή-γραμμικών δυναμικών αναλύσεων (με εν χρόνω ολοκλήρωση) αντιπροσωπευτικών γεφυρών, τριών έως πέντε ανοιγμάτων. Όμως για την εφαρμογή της απαιτούνται μόνο ελαστικά εργαλεία. Σε αντίθεση με τις έως τώρα ερευνητικές προσπάθειες, όπου γίνεται η απλουστευτική παραδοχή γραμμικής συμπεριφοράς του φορέα, στην παρούσα έρευνα δίνεται έμφαση στην προσομοίωση των περιοχών του φορέα και λαμβάνονται υπ’ όψιν οι μή-γραμμικότητές του.
Από την εφαρμογή του διαπιστώνεται ότι ο προτεινόμενος σχεδιασμός βάσει μετακινήσεων προσφέρει πολύ οικονομικότερα ποσοστά όπλισης (από 1/2 έως 1/7 στο διαμήκη οπλισμό και από 1/1 έως 1/3 στον εγκάρσιο οπλισμό), χωρίς να επιβαρύνει ουσιαστικά την επιτελεστικότητα της γέφυρας - η υπεραντοχή των γεφυρών που σχεδιάζονται με την προτεινόμενη μεθοδολογία είναι πρακτικά ισοδύναμη με την υπεραντοχή των συμβατικά σχεδιασμένων γεφυρών.
Η παρουσίαση της μεθοδολογίας περιλαμβάνει την περιγραφή της διαδικασίας σχεδιασμού υπό μορφή αλγόριθμου (Κεφ. 2), του τρόπου εφαρμογής της στην πράξη (διαδικασία προσομοίωσης, παραδείγματα σχεδιασμού: Κεφ. 3), του θεωρητικού υποβάθρου βάσει του οποίου αναπτύχθηκε (Κεφ. 4), των προβλημάτων της συμβατικής μεθοδολογίας (παραδείγματα σχεδιασμού βάσει δυνάμεων: Κεφ. 3) και των κενών που διαπιστώνονται στην τεκμηρίωση της συμβατικής μεθοδολογίας (Κεφ. 4). Η αποτίμηση του σχεδιασμού (Κεφ. 3) δεκαέξι αντιπροσωπευτικών γεφυρών (οκτώ σχεδιασμένων βάσει μετακινήσεων και οκτώ συμβατικά σχεδιασμένων), παρουσιάζεται υπό μορφή παράλληλης σύγκρισης της επιτελεστικότητας και συνηγορεί υπέρ των πλεονεκτημάτων της νέας μεθοδολογίας. Στα Παραρτήματα δίνονται πληροφορίες για τα υπολογιστικά εργαλεία που αναπτύχθηκαν για την προσομοίωση και την ανάλυση των γεφυρών (επέκταση προγράμματος ANSRuop). / The majority of seismic design researchers/specialists concludes that displacement-based design methodologies reduce the uncertainty of the design process and probably lead to less expensive structures. The absence of a simple displacement-based seismic design procedure for bridges that will be feasible and compatible with the current design practice and the nonexistence of a proposal for the displacement-based design of the deck indicate the gap of knowledge in this field of earthquake engineering. This thesis attempts to contribute to the reduction of this gap and for this scope proposes a new methodology. The procedure focuses on bridges with concrete piers monolithically connected to a prestressed concrete continuous deck and comprises simple steps for the estimation of the inelastic/nonlinear deformations of both the piers and the deck - through elastic modal response spectrum analysis, extending the applicability of the "equal displacement" rule to the level of member deformations.
About two thousands nonlinear dynamic (time-history) analyses of several representative bridges (with deck of three or five spans) are used for the development and the calibration of the procedure. However, for the application of the methodology only elastic modal response spectrum analysis is needed. Contrary to other current researches, which adopt the hypothesis of deck elastic response, the nonlinearities of the deck are modeled.
The proposed displacement-based procedure offers lower reinforcement ratios (from 1/2 to 1/7 for the longitudinal reinforcement and from 1/1 to 1/3 for the transverse reinforcement) at no detriment to the expected seismic performance - the global overstrength of the bridges which are designed with the proposed procedure is practically equivalent to the global overstrength of the conventionally designed bridges (current force-based design).
The step by step description of the design algorithm (Chap. 2) is followed by the practical application of the methodology (modeling aspects, design examples: Chap. 3), the conceptual justification (Chap. 4), the deficiencies of the conventional design procedure (force-based design examples: Chap. 3) and the fallacies in the justification of the conventional design methodology (Chap. 4). Comparative performance-based design evaluation (Chap. 3) of sixteen representative bridges (eight bridges subjected to alternative seismic design) indicates the benefits of the proposed procedure. The computational capabilities which were developed for the modeling and the analysis of the bridges are described in the appendices (upgrade of program ANSRuop).
|
1186 |
Fine grained sediment clean-up in a modern urban environmentVillemure, Marlene January 2013 (has links)
Fine grained sediment deposition in urban environments during natural hazard events can impact critical infrastructure and properties (urban terrain) leading to reduced social and economic function and potentially adverse public health effects. Therefore, clean-up of the sediments is required to minimise impacts and restore social and economic functionality as soon as possible. The strategies employed to manage and coordinate the clean-up significantly influence the speed, cost and quality of the clean-up operation. Additionally, the physical properties of the fine grained sediment affects the clean-up, transport, storage and future usage of the sediment. The goals of the research are to assess the resources, time and cost required for fine grained sediment clean-up in an urban environment following a disaster and to determine how the geotechnical properties of sediment will affect urban clean-up strategies. The thesis focuses on the impact of fine grained sediment (<1 mm) deposition from three liquefaction events during the Canterbury earthquake sequence (2010-2011) on residential suburbs and transport networks in Christchurch. It also presents how geotechnical properties of the material may affect clean-up strategies and methods by presenting geotechnical analysis of tephra material from the North Island of New Zealand. Finally, lessons for disaster response planning and decision making for clean-up of sediment in urban environments are presented.
A series of semi-structured interviews of key stakeholders supported by relevant academic literature and media reports were used to record the clean-up operation coordination and management and to make a preliminary qualification of the Christchurch liquefaction ejecta clean-up (costs breakdown, time, volume, resources, coordination, planning and priorities). Further analysis of the costs and resources involved for better accuracy was required and so the analysis of Christchurch City Council road management database (RAMM) was done. In order to make a transition from general fine sediment clean-up to specific types of fine disaster sediment clean-up, adequate information about the material properties is required as they will define how the material will be handled, transported and stored. Laboratory analysis of young volcanic tephra from the New Zealand’s North Island was performed to identify their geotechnical properties (density, granulometry, plasticity, composition and angle of repose).
The major findings of this research were that emergency planning and the use of the coordinated incident management system (CIMS) system during the emergency were important to facilitate rapid clean-up tasking, management of resources and ultimately recovery from widespread and voluminous liquefaction ejecta deposition in eastern Christchurch. A total estimated cost of approximately $NZ 40 million was calculated for the Christchurch City clean-up following the 2010-2011 Canterbury earthquake sequence with a partial cost of $NZ 12 million for the Southern part of the city, where up to 33% (418 km) of the road network was impacted by liquefaction ejecta and required clearing of the material following the 22 February 2011 earthquake. Over 500,000 tonnes of ejecta has been stockpiled at Burwood landfill for all three liquefaction inducing earthquake events. The average cost per kilometre for the event clean-up was $NZ 5,500/km (4 September 2010), $NZ 11,650/km (22 February 2011) and $NZ 11,185/km (13 June 2011). The duration of clean-up time of residential properties and the road network was approximately two to three months for each of the three liquefaction ejecta events; despite events volumes and spatial distribution of ejecta. Interviews and quantitative analysis of RAMM data revealed that the experience and knowledge gained from the Darfield earthquake (4 September 2010) clean-up increased the efficiency of the following Christchurch earthquake induced liquefaction ejecta clean-up events.
Density, particle size, particle shape, clay content and moisture content, are the important geotechnical properties that need to be considered when planning for a clean-up method that incorporates collection, transport and disposal or storage. The geotechnical properties for the tephra samples were analysed to increase preparedness and reaction response of potentially affected North Island cities from possible product from the active volcanoes in their region. The geotechnical results from this study show that volcanic tephra could be used in road or construction material but the properties would have to be further investigated for a New Zealand context. Using fresh volcanic material in road, building or flood control construction requires good understanding of the material properties and precaution during design and construction to extra care, but if well planned, it can be economically beneficial.
|
1187 |
Étude de la réponse dynamique des ponts roulants soumis à des chocs multiples pendant un séisme : Co-simulation implicite / explicite multi-échelle en temps pour la dynamique du contact / Numerical response of bridge cranes subjected to repeated shocks during an earthquake : Implicit / explicite multi-time scale co-simulation for contact dynamicsFekak, Fatima-Ezzahra 02 May 2017 (has links)
Les ponts roulants sont des engins de levage situés en haut des bâtiments qu'ils équipent. Ils servent à manutentionner des charges très lourdes et parfois critiques. Pendant un séisme, un pont roulant est exposé à des chocs multiples. Ces impacts peuvent causer des dommages importants dans la structure pouvant conduire à une chute de la charge manutentionnée ou du pont roulant lui-même. Donc, la vérification de la tenue des ponts roulants au séisme est une question primordiale. Actuellement, cette vérification est basée sur des méthodes de calcul statiques. Ces méthodes font l'hypothèse d'un comportement purement linéaire des ponts roulants ce qui les rend très conservatives. Depuis quelques années les niveaux sismiques imposés par les autorités nationales augmentent chaque année, et les constructeurs de ponts roulants se trouvent dans l'incapacité de construire à partir des efforts sur-estimés fournis par les méthodes statiques. L'objectif de la thèse est l'étude de la réponse dynamique d'un pont roulant pendant un séisme en prenant en compte les non-linéarités géométriques et matériau. Afin de modéliser ces phénomènes, une analyse dynamique temporelle avec une approche multi-échelle en temps est adoptée. Pour prendre en compte l'aspect haute fréquence des chocs, un intégrateur temporel variationnel explicite, basé sur la méthode des multiplicateurs de Lagrange et dédié au contact/impact, est développé. Ensuite, un intégrateur hétérogène (différents schémas d'intégration) asynchrone (différents pas de temps), basé sur la méthode de couplage GC, est appliqué au problème du pont roulant. Cette stratégie multi-échelle en temps permet d'adapter le schéma d'intégration et le pas de temps au sous domaine considéré. Par conséquent, l'intégrateur explicite est adopté dans les zones de contact et un schéma implicite de type accélération moyenne, est adopté dans le reste de la structure. Finalement, un démonstrateur de co-simulation entre les logiciels Cast3M et Europlexus est mis en place pour montrer le gain très significatif en temps de calcul dans le cas d'un modèle élément finis tridimensionnel d'un pont roulant industriel. / Bridge cranes are hoisting appliances located overhead in buildings. They are used to handle very heavy and sometimes critical loads. During an earthquake, a bridge crane may be subjected to multiple impacts between wheels and rails. These impacts can cause significant damage to the structure leading to a fall of the handled load or the bridge crane itself. Therefore, the qualification of such equipment, subjected to an earthquake, is very important. Currently, this qualification is based on static methods. These methods assume a purely linear behavior of the bridge cranes, which leads to a very conservative forces. Consequently, the bridge cranes manufacturers are sometimes unable to design the equipement from the over-estimated efforts provided by the static methods. The aim of this work is to study the dynamic response of a bridge crane during an earthquake by taking into account the geometric and material non-linearities. In order to model such phenomena, a time-history dynamic analysis with a multi-scale approach is performed. To take into account the high frequency aspect of the impacts between wheels and rails, a Lagrange explicit contact/impact time integrator is proposed. This work has also led to the development of an explicit–implicit HATI (Heterogeneous Asynchronous Time Integrator) for contact/impact dynamics. This method allows us to adopt an explicit contact/impact time integrator in the contact area and an implicit time integrator with a coarse mesh in the rest of the domain. Finally, a co-simulation demonstrator between Cast3M and Europlexus softwares is set up to show the very significant gain in computation time for a three-dimensional finite element model of an industrial bridge crane.
|
1188 |
Efeito da rigidez de pilar parede no comportamento sísmico de edifício de concreto armadoThölken, Denise 13 December 2013 (has links)
Este trabalho tem como objeto o estudo do efeito da rigidez de pilar parede no comportamento estrutural de edifícios de concreto armado submetidos a sismos. Foram consideradas as premissas da norma brasileira ABNT NBR15421:2006, que apresenta os critérios para projeto de estruturas resistentes a sismo. A análise linear com emprego dos métodos da norma - método das forças horizontais equivalentes, método espectral e histórico de aceleração no tempo - foi aplicada em edifícios com dois tipos de sistemas estruturais, sendo eles pórtico de concreto e sistema dual pórtico de concreto e pilar parede. Os resultados foram analisados nos pórticos de extremidade das estruturas nos sentidos longitudinal (x) e transversal (y), comparando-se os deslocamentos de cada pavimento e esforços cortantes, momento fletor e normal nas bases dos pilares. A comparação foi realizada entre os três métodos aplicados e os sistemas estruturais analisados. / The aim of this work is to study the stiffness effect of wall columns on structural behavior of reinforced concrete buildings subjected to seismic action. The premises of the Brazilian standard ABNT NBR14521:2006 were considered, which presents criteria for earthquake resistant design of structures. The linear analysis employed the methods of the Brazilian standard - equivalent static load method, response spectrum analysis and time history method - were applied to buildings with two types of structural systems, namely concrete frame and dual system concrete frame and wall columns. The results were analyzed in edge frames structures in the longitudinal and transverse directions, comparing the displacement of each floor and shear, bending moment and axial forces on the bases of the columns. A comparison was made between the three methods applied and the structural systems analyzed.
|
1189 |
Charaterization of Sand-Rubber Mixture and Numerical Analysis for Vibration IsolationManohar, D R January 2016 (has links) (PDF)
Scrap tyres provide numerous advantages from the viewpoint of civil engineering practices. Scrap tyres are light weight, have high vibration absorption, high elastic compressibility, high hydraulic conductivity, and temperature isolation potential. Scrap tyres have a thermal resistivity that is about seven times higher than soil; they produce low earth pressure and absorb vibrations. Many new techniques have emerged with time to utilize these advantageous characteristics for practical purposes in civil engineering. Though current reuse and recovery of scrap tyres has reduced the amount of landfills, but still there is a need for developing additional practices for the reuse of scrap tyres. Moreover, most of present practices do not use its vibration absorption capacity efficiently. To use the scrap tyres as individual material or mixed with soil in civil engineering applications, the systematic understanding of static and dynamic properties of sand-rubber mixtures (SRM) are of prime importance. In the present study an attempt has been made to characterize the SRM to use them as low-cost isolation material for low-to-medium rise buildings.
Proposal of this isolation system using SRM is addressed in this study in four parts; in the first part, the estimation of shear strength and volumetric characteristics of the SRM were carried out. A total of seven different rubber sizes (six sizes of granulated rubber; 2 - 1 mm; 4.75 - 2 mm; 5.6 - 4.75 mm; 8 - 5.6 mm; 8 - 9.5 mm; 12.5 - 9.5 mm and one size of tyre chips; 20 - 12.5 mm) were considered for characterizing the SRM, and the rubber size which has higher shear strength characteristics is identified as optimum size for further studies. Second part deals with the effect of reinforcement on SRM with higher rubber content (50% and 75% rubber by volume). In the third part, dynamic properties of selected SRM combination with and without reinforcement were generated from experimental studies. In the last part, the numerical analysis was carried out using finite element program Strand7 to find out optimum dimension of proposed isolation scheme and reduction of spectral accelerations. In addition, the laboratory model tests were also carried out on square footing supported on unreinforced and reinforced SRM. The relative performances of reinforcement on settlement characteristics of SRM for 50% and 75% SRM have been compared with unreinforced SRM.
Engineering behaviour of SRM has been studied by considering different rubber sizes and compositions by carrying out large scale direct shear test and Unconsolidated Undrained (UU) triaxial test. The shear strength characteristics such as peak shear stress, cohesion, friction angle, secant/elastic modulus, volumetric strain, failure and ultimate strength, ductility/brittleness index, and energy absorption capacity of sand and SRM were determined. The optimum percentage rubber content based on maximum shear strength and energy absorption capacity has been arrived. The granulated rubber size (12.5 - 9.5 mm) and percentage ratio, 30% by volume is found to be optimum size and content, which gives the maximum energy absorption capacity and lower brittleness index values compared to other rubber sizes. This chapter also describes the applicability of concept of Response Surface Methodology (RSM) to identify an approximate response surface model from experimental investigations on the engineering properties of sand and SRM. The experimental data were quantitatively analyzed by multiple regression models by correlating response variables with input variables in this study.
To consume more tyres in SRM, rubber mix of 50 % and 75 % mixes are studied and these SRM results in lower shear strength and higher volume change when compared to 30 % SRM. To improve shear strength and reduce compressibility, geosynthetic reinforcement study has been carried out for 50% and 75% rubber by volume. Here geotextile, geogrid and geonets were used as reinforcement and number of layers and spacing between layers were varied. Finally type of reinforcement, number of layers and optimum spacing are arrived for the optimum rubber size of 12.5 - 9.5 mm for reinforced SRM. This study found that 4 layers with equal spacing of geotextile for 50 % SRM and geonet for 75 % SRM shows better strength when compared to other combinations.
Further dynamic properties such as shear modulus and damping values at different strain level are estimated for red soil, sand, 30 % SRM and unreinforced and reinforced 50 % and 75 % SRM by carrying out resonant column tests and cyclic triaxial tests. The normalized shear modulus and damping ratio curves have been developed for these materials. The experimental results indicate that, shear modulus increases for 30% rubber by volume when compared to sand, thereafter the shear modulus values decreased with a further increase in rubber content in SRM. Whereas the damping ratio increases with increasing rubber content in SRM. For sand and SRM, with an increase in confining pressure shear modulus increases and damping ratio decreases. Based on the comprehensive set of experimental results, a modified hyperbolic model has been proposed. These properties are further used in the numerical analysis to find out the effectiveness of SRM as isolation material.
Numerical dynamic analysis has been carried out on a 2-D finite element model of the soil-foundation-structure system. The building model has been generated considering the typical G+2 building resting on 20 m thick soil followed by rock depth and foundation is placed at 2.0 m below ground level. The beams and columns in the superstructure are modeled using 2-D frame elements. The soil column has been modeled using 4-noded 2-D plane strain plate elements. Considering the transmitting boundary condition, viscous dampers are implemented at the base of the computational soil domain in order to mitigate the reflective effects of waves. The Newmark family method (average acceleration method) has been used to calculate the displacement, velocity and acceleration vectors. Comprehensive numerical simulations have been carried out on the soil-foundation-structure system by varying rubber content in SRM (30%, 50% and 75% granulated rubber by volume), depth and thickness of SRM around footing and considering two input earthquake acceleration time history. It was found that earthquake vibrations are considerably reduced for SRM with higher rubber content. The optimum dimension of SRM giving maximum reduction in shaking level is found to be 3B below the footing and 0.75B (where B is the width of footing) on the side of the footing. Generally, the shaking levels at different floor can be reduced by 30-50%, with the use of 75% SRM. The results also indicated that the effectiveness of proposed system would depend on the characteristics of ground motion. To study the bearing capacity of square footing on SRM, laboratory model tests were carried out on square footing supported on unreinforced and reinforced SRM. The SRM combination which have been used for numerical studies are used in this model studies to know the bearing capacity and settlement characteristics. The optimum dimension of SRM around footing has been constructed. Model tests results show that, the bearing capacity decreases and settlement increases steadily with the increase in rubber content in SRM. Addition of reinforcement to SRM significantly improved the bearing capacity and reduced settlement characteristics. Reinforced SRM may be used as an effective low cost isolation scheme to reduce earthquake vibrations.
|
1190 |
Méthodes simplifiées basées sur une approche quasi-statique pour l’évaluation de la vulnérabilité des ouvrages soumis à des excitations sismiques / Simplified methods based on a quasi-static approach for the vulnerability assessment of structures subjected to seismic excitationsTataie, Laila 05 December 2011 (has links)
Dans le cadre de la protection du bâti face au risque sismique, les techniques d’analyse simplifiées, basées sur des calculs quasi-statiques en poussée progressive, se sont fortement développées au cours des deux dernières décennies. Le travail de thèse a pour objectif d’optimiser une stratégie d’analyse simplifiée proposée par Chopra et al. (2001) et adoptée par les normes américaines FEMA 273. Il s’agit d’une analyse modale non linéaire découplée, dénommée par les auteurs UMRHA qui se caractérisent principalement par : des calculs de type pushover selon les modes de vibration dominants de la structure, la création de modèles à un degré de liberté non linéaire à partir des courbes de pushover, puis le calcul de la réponse temporelle de la structure en recombinant les réponses temporelles associées à chaque mode de vibration. Dans ce travail, la méthode UMRHA a été améliorée en investiguant les points suivants. Tout d’abord, plusieurs modèles à un degré de liberté non linéaire déduits des courbes de pushover modal sont proposés afin d’enrichir la méthode UMRHA originelle qui emploie un simple modèle élasto-plastique : autres modèles élasto-plastiques avec des courbes enveloppes différentes, le modèle de Takeda prenant en compte un comportement hystérétique propre aux structures sous séismes, et enfin, un modèle simplifié basé sur la dégradation de fréquence en fonction d’un indicateur de dommage. Ce dernier modèle à un degré de liberté privilégie la vision de la chute de fréquence au cours du processus d’endommagement de la structure par rapport à une description réaliste des boucles d’hystérésis. La réponse totale de la structure est obtenue en sommant les contributions non linéaires des modes dominants aux contributions linéaires des modes non dominants. Enfin, la dégradation des déformées modales, due à l’endommagement subi par la structure au cours de la sollicitation sismique, est prise en compte dans la méthode M-UMRHA proposée dans ce travail, en généralisant le concept précédent de dégradation des fréquences modales en fonction d’un indicateur de dommage : la déformée modale devient elle-aussi dépendante d’un indicateur de dommage, le déplacement maximum en tête de l’ouvrage ; l’évolution de la déformée modale en fonction de cet indicateur est directement identifiée à partir des calculs de pushover modal. La pertinence de la nouvelle méthode M-UMRHA est investiguée pour plusieurs types de structures, en adoptant des modélisations éprouvées dans le cadre de la simulation des structures sous séismes : portique en béton armé modélisé par des éléments multifibres pour le béton et les armatures, remplissage en maçonnerie avec des éléments barres diagonales résistant uniquement en compression, bâti existant contreventé (Hôtel de Ville de Grenoble) avec des approches coques multicouches. Les résultats obtenus par la méthode simplifiée proposée sont comparés aux résultats de référence issus de l'analyse temporelle non linéaire dynamique. / In the context of building’s protection against seismic risk, simplified analysis techniques, based on quasi-static analysis of pushover, have strongly developed over the past two decades. The thesis aims to optimize a simplified method proposed by Chopra and Goel in 2001 and adopted by American standards FEMA 273. This method is a nonlinear decoupled modal analysis, called by the authors UMRHA (Uncoupled Modal for Response History Analysis) which is mainly characterized by: pushover modal analysis according to the dominant modes of vibration of the structure, setting up nonlinear single degree of freedom systems drawn from modal pushover curves, then determining the history response of the structure by combining of the temporal responses associated with each mode of vibration. The decoupling of nonlinear history responses associated with each mode is the strong assumption of the method UMRHA. In this study, the UMRHA method has been improved by investigating the following points. First of all, several nonlinear single degree of freedom systems drawn from modal pushover curves are proposed to enrich the original UMRHA method, in which a simple elastic-plastic model is used, other elastic-plastic models with different envelope curves, Takeda model taking into account an hysteretic behavior characteristic of structures under earthquakes, and finally, a simplified model based on the frequency degradation as a function of a damage index. The latter nonlinear single degree of freedom model privileges the view of the frequency degradation during the structure damage process relative to a realistic description of hysteresis loops. The total response of the structure is obtained by summing the contributions of the non linear dominant modes to those of linear non dominant modes. Finally, the degradation of the modal shapes due to the structure damage during the seismic loading is taken into account in the new simplified method M-UMRHA (Modified UMRHA) proposed in this study. By generalizing the previous model of frequency degradation as a function of a damage index: the modal shape becomes itself also dependent on a damage index, the maximum displacement at the top of the structure; the evolution of the modal shape as a function of this index is directly obtained from the modal pushover analysis. The pertinence of the new method M-UMRHA is investigated for several types of structures, by adopting tested models of structures simulation under earthquakes: reinforced concrete frame modeled by multifibre elements with uniaxial laws under cyclic loading for concrete and steel, infill masonry wall with diagonal bars elements resistant only in compression, existing building (Grenoble City Hall) with multilayer shell elements and nonlinear biaxial laws based on the concept of smeared and fixed cracks. The obtained results by the proposed simplified method are compared to the reference results derived from the nonlinear response history analysis.
|
Page generated in 0.0237 seconds