157 research outputs found

    Survivable and disaster- resilient submarine optical-fiber cable deployment

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    06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Internete olan mevcut sosyal ve ekonomik bağlılık ve servis kesintileri nedeni ile oluşan önemli miktardaki tamir masrafları ile ağ kalımlılığı günümüzde telekomünikasyon ağ dizaynının önemli bir parçası olmuştur. Ayrıca, denizaltı fiber optik kabloların depremler gibi doğal afetlere veya insan-yapımı afetlere karşı zayıf olduğu da herkesçe kabul edilmiş bir gerçektir. Afete dayanıklı bir denizaltı kablo yerleştirilmesi, bir yada daha fazla kablo afet nedeni ile koptuğunda ağ servislerini yeniden eski haline getirmek için ağ operatörünün maliyetlerini (yolculuk maliyeti, kapasite kayıp maliyeti ve hasar gören kablonun tamir maliyeti) azaltabilir. Bu çalışmada afet-farkındalı denizaltı fiber optik kabloları yerleştirme problemini araştırdık. Kablolar için bir yol/rota seçerken yaklaşımımız toplam beklenen kayıp maliyetini, denizaltı fiber kabloların afetler nedeni ile zarar görebileceğini de düşünerek, bütçe ve diğer kısıtlamalar altında minimize etmeyi hedefler. Yaklaşımımızda afetle ilişkisiz arızaların ana kablonun yanında bir de yedek kablo sağlanarak üstesinden gelindiğini varsaydık. Önce basitçe bir su kütlesi (deniz/okyanus) tarafından ayrılmış iki kara parçası üzerine yerleştirilmiş iki düğümün olduğu bir senaryoyu düşündük. Daha sonra problemi formüle edebilmek için afet bölgelerinden sakınacak şekilde eliptik kablo şeklini dikkate aldık. En nihayetinde problem için, bu durumda yaklaşımımızın potansiyel faydalarını gösteren sayısal örneklerle desteklediğimiz bir Tamsayı Lineer Programlama formülasyonu ürettik. Bununla birlikte problemi daha pratik hale getirmek için, farklı kara parçalarına yerleşmiş çoklu düğümlerin örgüsel bir ağ topolojisini, düzenli şekillere sahip olmayan kabloları, deniz altındaki ortamın topografisini de dikkate aldık. Bu problemi de ifade etmek için sayısal örneklere birlikte bir Tamsayı Lineer Programlama sunduk. Sonuç olarak, pratik durumu düşünerek bir örnek durum incelemesi üzerinde yaklaşımımızı mevcut kablolama sistemleri ile kıyaslayarak teyit ettik. İki durumda da, sonuçlar bize %2-%11 oranında bir yerleştirme maliyeti artışı karşılığında beklenen maliyeti %90-%100 arasında azaltabileceğimizi gösterdi.With the existing profoundly social and economic reliance on the Internet and the significant reparation cost associated with service interruption, network survivability is an important element in telecommunication network design nowadays. Moreover, the fact that submarine optical-fiber cables are susceptible to man-made or natural disasters such as earthquakes is well recognized. A disaster-resilient submarine cable deployment can save cost incurred by network operators such as the capacity-loss cost, the cruising cost and the repair cost of the damaged cables, in order to restore network service when cables break due to a disaster. In this study, we investigate disaster-aware submarine fiber-optic cable deployment problem. While selecting a route/path for cables, our approach aims to minimize the total expected cost, considering that submarine optical-fiber cables may break because of natural disasters, subject to deployment budget and other constraints. In our approach, we assume disaster-unrelated failures are handled by providing a backup cable along with primary cable. In the simple case we consider a scenario with two nodes located on two different lands separated by a water body (sea/ocean). We then consider an elliptic cable shape to formulate the problem, which can be extended to other cable shapes, subject to avoiding deploying cable in disaster zones. Eventuaaly, we provide an Integer Linear Programming formulation for the problem supported with illustrative numerical examples that show the potential benefit of our approach. Furthermore, in order to make the problem more practical, we consider a mesh topology network with multiple nodes located on different sea/ocean, submarine optical- fiber cables of irregular shape, and the topography of undersea environment. Eventually, we provide an Integer Linear Programming to address the problem, together with illustrative numerical examples. Finally, we validate our approach by conducting a case study wherein we consider a practical submarine optical-fiber cable system susceptible to natural disasters. In this case, we compare our approach against the existing cable system in terms of deployment cost and reduction in expected cost. In either case results show that our approach can reduce expected cost from 90% to 100% at a slight increase of 2% to 11% in deployment cost of disaster-unaware approach

    Development of an acoustic emission waveguide-based system for monitoring of rock slope deformation mechanisms

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    Hundreds of thousands of landslides occur every year around the world impacting on people's lives. Monitoring techniques able to foresee imminent collapse and provide a warning in time useful for action to be taken are essential for risk reduction and disaster prevention. Acoustic emission (AE) is generated in soil and rock materials by rearrangement of particles during displacement or increasing damage in the microstructure preceding a collapse; therefore AE is appropriate for estimation of slope deformation. To overcome the high attenuation that characterise geological materials and thus to be able to monitor AE activity, a system called Slope ALARMS that makes use of a waveguide to transmit AE waves from a deforming zone to a piezoelectric transducer was developed. The system quantifies acoustic activity as Ring Down Count (RDC) rates. In soil applications RDC rates have been correlated with the rate of deformation, however, the application to rock slopes poses new challenges over the significance of the measured AE trends, requiring new interpretation strategies. In order to develop new approaches to interpret acoustic emission rates measured within rock slopes, the system was installed at two trial sites in Italy and Austria. RDC rates from these sites, which have been measured over 6 and 2.5 years respectively, are analysed and clear and recurring trends were identified. The comparison of AE trends with response from a series of traditional instruments available at the sites allowed correlation with changes in external slope loading and internal stress changes. AE signatures from the limestone slope at the Italian site have been identified as generated in response to variations in the groundwater level and snow loading. At the conglomerate slope in Austria, AE signatures include the detachment of small boulders from the slope surface caused by the succession of freeze-thaw cycles during winter time. Consideration was also given to laboratory testing of specific system elements and field experiments. A framework towards strategies to interpret measured acoustic emission trends is provided for the use of the system within rock slopes

    6th International Probabilistic Workshop - 32. Darmstädter Massivbauseminar: 26-27 November 2008 ; Darmstadt, Germany 2008 ; Technische Universität Darmstadt

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    These are the proceedings of the 6th International Probabilistic Workshop, formerly known as Dresden Probabilistic Symposium or International Probabilistic Symposium. The workshop was held twice in Dresden, then it moved to Vienna, Berlin, Ghent and finally to Darmstadt in 2008. All of the conference cities feature some specialities. However, Darmstadt features a very special property: The element number 110 was named Darmstadtium after Darmstadt: There are only very few cities worldwide after which a chemical element is named. The high element number 110 of Darmstadtium indicates, that much research is still required and carried out. This is also true for the issue of probabilistic safety concepts in engineering. Although the history of probabilistic safety concepts can be traced back nearly 90 years, for the practical applications a long way to go still remains. This is not a disadvantage. Just as research chemists strive to discover new element properties, with the application of new probabilistic techniques we may advance the properties of structures substantially. (Auszug aus Vorwort

    Safety and Reliability - Safe Societies in a Changing World

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    The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen

    The 29th Aerospace Mechanisms Symposium

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    The proceedings of the 29th Aerospace Mechanisms Symposium, which was hosted by NASA Johnson Space Center and held at the South Shore Harbour Conference Facility on May 17-19, 1995, are reported. Technological areas covered include actuators, aerospace mechanism applications for ground support equipment, lubricants, pointing mechanisms joints, bearings, release devices, booms, robotic mechanisms, and other mechanisms for spacecraft

    Seismische Risikoanalyse unterirdischer Versorgungsleitungen

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    Seismically caused failure of buried lifelines can result in disastrous events. Due to the grave consequences of those failures in past earthquakes, the need for reliable models examining the dynamic response of lifelines under earthquake excitation grows. In the present work, a methodology is developed to analyse the damage risk of buried lifelines exposed to seismic wave propagation. In order to perform this analysis, a three-dimensional numerical model is developed to describe the dynamic response of pipelines embedded in soil. Thereby, the emphasis is placed on three topics: the incorporation of dynamic soil-structure interaction, the advanced modelling of seismic excitation, and the over-all consideration of uncertainties. A hybrid finite element (FE)-scaled boundary finite element method (SBFEM) is presented to examine soil- structure interaction. Whereas the FEM enables a detailed modelling of the near-field, the SBFEM fulfils the wave radiation condition at infinity. In the latter method, increase of efficiency is, amongst others, achieved by employing substructuring techniques without losses of accuracy. For modelling seismic wave propagation in the near-field, a two-step procedure based on the domain reduction method is introduced. In the first step, a large scale simulation of the earthquake is performed, whereon the near- field is examined by the hybrid model. Thus, realistic seismic wave propagation inside the near-field can be modelled. Thereupon, an integrated probabilistic analysis is performed, which includes parameters of the entire seismic wave propagation path. For this process, a point estimate method is employed which enables an efficient and reliable determination of the failure probability of the pipeline. Parameter studies demonstrate the applicability of the present methodology which is not only applicable to lifelines but to any other structure under seismic wave excitation.Das seismisch bedingte Versagen von unterirdischen Versorgungsleitungen (Lifelines) und dessen Folgen offenbaren die Notwendigkeit von verlässlichen Modellen, die das dynamische Antwortverhalten realistisch abbilden. In der vorliegenden Arbeit wird eine Methode entwickelt, durch welche das Schadensrisiko von Lifelines infolge von seismischen Wellenausbreitungseffekten bestimmt werden kann. Zur Durchführung der Analyse wird ein dreidimensionales numerisches Modell entwickelt, welches das dynamische Verhalten von erdverlegten Rohrleitungen beschreibt. Bei der Entwicklung werden drei Schwerpunkte gesetzt: die detaillierte Abbildung der dynamischen Boden-Bauwerk-Wechselwirkung, die realistische Modellierung der seismischen Anregung sowie die globale Berücksichtigung von Unsicherheiten. Zur Untersuchung der Boden-Bauwerk-Wechselwirkung wird eine hybride Finite Element (FE)-Scaled Boundary Finite Element Methode (SBFEM) verwendet, wobei letztere die Wellenabstrahlung ins Unendliche simuliert. Effizienzsteigerungen können unter anderem durch den Einsatz von Substrukturmethoden erreicht werden. Zur Modellierung der seismischen Wellenausbreitung im Nahfeld wird eine Zwei-Schritt-Prozedur basierend auf der Domain Reduction Method vorgestellt. Im ersten Schritt wird eine großmaßstäbliche Simulation des Erdbebens durchführt, woraufhin im zweiten Schritt das Nahfeld mit der hybriden Methode untersucht wird. Diese Prozedur ermöglicht die Modellierung von realistischer seismischer Wellenausbreitung innerhalb des Nahfeldes. Darauf aufbauend wird eine ganzheitliche probabilistische Analyse durchgeführt, die Parameter des kompletten Ausbreitungspfades der seismischen Wellen einbindet. Für dieses Verfahren zur Ermittlung der Versagenswahrscheinlichkeit wird ein Punktschätzverfahren effizient eingesetzt. Parameterstudien zeigen die Anwendbarkeit der vorgestellten Methode, die sich nicht nur auf Rohrleitungen sondern auch auf jede andere Struktur unter seismischer Wellenbelastung erstreckt

    Symmetry in Structural Health Monitoring

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    In this Special Issue on symmetry, we mainly discuss the application of symmetry in various structural health monitoring. For example, considering the health monitoring of a known structure, by obtaining the static or dynamic response of the structure, using different signal processing methods, including some advanced filtering methods, to remove the influence of environmental noise, and extract structural feature parameters to determine the safety of the structure. These damage diagnosis methods can also be effectively applied to various types of infrastructure and mechanical equipment. For this reason, the vibration control of various structures and the knowledge of random structure dynamics should be considered, which will promote the rapid development of the structural health monitoring. Among them, signal extraction and evaluation methods are also worthy of study. The improvement of signal acquisition instruments and acquisition methods improves the accuracy of data. A good evaluation method will help to correctly understand the performance with different types of infrastructure and mechanical equipment

    Oceanography

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    How inappropriate to call this planet Earth when it is quite clearly Ocean (Arthur C. Clarke). Life has been originated in the oceans, human health and activities depend from the oceans and the world life is modulated by marine and oceanic processes. From the micro-scale, like coastal processes, to macro-scale, the oceans, the seas and the marine life, play the main role to maintain the earth equilibrium, both from a physical and a chemical point of view. Since ancient times, the world's oceans discovery has brought to humanity development and wealth of knowledge, the metaphors of Ulysses and Jason, represent the cultural growth gained through the explorations and discoveries. The modern oceanographic research represents one of the last frontier of the knowledge of our planet, it depends on the oceans exploration and so it is strictly connected to the development of new technologies. Furthermore, other scientific and social disciplines can provide many fundamental inputs to complete the description of the entire ocean ecosystem. Such multidisciplinary approach will lead us to understand the better way to preserve our "Blue Planet": the Earth

    Retrofit Solutions for New Zealand Hollow-Core Floors and Investigation of Reliable Diaphragm Load-Paths in Earthquakes

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    Standard floor diaphragm design relies on compression struts and tension ties within the floor to transfer large forces between lateral load resisting structural elements and stiffen the building during earthquakes. Floors in reinforced concrete frame buildings have been observed with wide cracks around the floor perimeter following earthquakes, raising questions about how compression struts can form between the floor and frame elements. An experimental investigation into reliable floor diaphragm force transfer mechanisms, and by extension load-paths, was undertaken using a full-scale two-way super- assembly frame specimen. Two tests were conducted where the specimen was subjected to simultaneous bi-directional inter-storey drift demands to induce realistic earthquake cracking damage between the floor and the frame. At different floor damage states, in-plane shear deformations were applied to the frame specimen to capture the deterioration of diaphragm transfer load-paths. Wide perimeter cracking was anticipated to eliminate diaphragm compression strut load-paths until shear deformation of the support frame-initiated binding with the floor, as it changed to a rhomboidal shape. This behaviour was not observed due to two observed phenomena across the two tests. In the first test, loss of beam torsional stiffness governed as the diaphragm load-path failure mechanism. Beam-to-floor continuity reinforcement acting in tension exceeded the weak-axis shear and torsion capacity of the perimeter frame beam plastic hinges. Beam elongation deformation incompatibility demands were relieved by the tops of the beams rotating into the floor. Deformation concentrated in the beam plastic hinges rather than forming cracks at the beam-to-floor interface. In the second test, wide cracks developed at the support-beam-to-floor interfaces. However, despite this, the diaphragm in-plane shear stiffness deteriorated less than what was observed during the first test. It was found that diaphragm struts could form across wide beam-to-floor cracks due to aggregate rubble falling into the cracks and providing a residual contact stress load-path. Evidence of compression strut formation was recorded up to crack widths of 5.5 mm. An initial suggestion is that compression struts can cross wide cracks that are smaller than ¼ of the aggregate size used in the floor topping concrete mixture. This only applies where there is ductile continuity reinforcement crossing the critical crack interface. The rate of diaphragm shear stiffness degradation with increasing inter-storey drift demands was highly dependent on the ratio of simultaneous bi-directionality, due to the impact simultaneous bending actions had on beam torsional capacity. For low ratios of inter-storey drift simultaneous bi-directionality, beam torsional stiffness was maintained to a greater degree, providing higher diaphragm in-plane shear stiffness. An adjacent research stream was conducted related to hollow-core flooring systems. Hollow-core floors were widely installed in multi-storey buildings throughout New Zealand in the 1980s and 1990s. Hollow-core units were designed to act as simply supported members. Unfortunately, continuity reinforcement used to sustain floor diaphragm load-paths enforces deformation incompatibility demands on the floor during earthquakes, subjecting hollow-core units to substantial positive and negative bending moment demands they were not designed for. These demands can initiate a range of brittle failure mechanisms in the units. Concerns regarding the potential for commonly installed retrofits, used to increase seating widths for hollow-core units, to promote brittle failure of hollow-core units under negative moment demands prompted an experimental investigation. Six hollow-core unit sub-assembly experiments were used to identify unfavourable seating details which could cause negative moment failure of the floor during an earthquake and verify retrofit solutions to prevent this from occurring. Successful retrofits were installed in a full-scale two-way super-assembly frame specimen subjected to simultaneous bi-directional earthquake demands with full three-dimensional effects for further rigorous verification. Four viable retrofit strategies were identified and verified to prevent negative moment failure from occurring while providing adequate seating for the hollow-core units. Hollow-core units seated on beam plastic hinges extending out of interior frame columns, named beta units, were experimentally tested with seismic demands for the first time in the super-assembly experiment. Following inter-storey drift demands of 3%, the residual gravity carrying capacity of a beta unit with substantial web-splitting was tested. Shear failure of the unit near the support occurred at gravity load demands aligning to 91% of the NZS1170.5 (Standards New Zealand, 2016) design live load combination (1.2G + 1.5Q), demonstrating the vulnerability of beta units. Retrofit strategies to prevent brittle failure and collapse of vulnerable hollow-core units seated at the ends of support beams were also tested in the super-assembly specimen, providing verification and design improvements for catch-frame and hanger retrofits
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