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Object-Oriented Damage Information Modeling Concepts and Implementation for Bridge Inspection
(2022)
Bridges are designed to last for more than 50 years and consume up to 50% of their life-cycle costs during their operation phase. Several inspections and assessment actions are executed during this period. Bridge and damage information must be gathered, digitized, and exchanged between different stakeholders. Currently, the inspection and assessment practices rely on paper-based data collection and exchange, which is time-consuming and error-prone, and leads to loss of information. Storing and exchanging damage and building information in a digital format may lower costs and errors during inspection and assessment and support future needs, for example, immediate simulations regarding performance assessment, automated maintenance planning, and mixed reality inspections. This study focused on the concept for modeling damage information to support bridge reviews and structural analysis. Starting from the definition of multiple use cases and related requirements, the data model for damage information is defined independently from the subsequent implementation. In the next step, the implementation via an established standard is explained. Functional tests aim to identify problems in the concept and implementation. To show the capability of the final model, two example use cases are illustrated: the inspection review of the entire bridge and a finite-element analysis of a single component. Main results are the definition of necessary damage data, an object-oriented damage model, which supports multiple use cases, and the implementation of the model in a standard. Furthermore, the tests have shown that the standard is suitable to deliver damage information; however, several software programs lack proper implementation of the standard.
In Germany, bridges have an average age of 40 years. A bridge consumes between 0.4% and 2% of its construction cost per year over its entire life cycle. This means that up to 80% of the construction cost are additionally needed for operation, inspection, maintenance, and destruction. Current practices rely either on paperbased inspections or on abstract specialist software. Every application in the inspection and maintenance sector uses its own data model for structures, inspections, defects, and maintenance. Due to this, data and properties have to be transferred manually, otherwise a converter is necessary for every data exchange between two applications. To overcome this issue, an adequate model standard for inspections, damage, and maintenance is necessary. Modern 3D models may serve as a single source of truth, which has been suggested in the Building Information Modeling (BIM) concept. Further, these models offer a clear visualization of the built infrastructure, and improve not only the planning and construction phases, but also the operation phase of construction projects. BIM is established mostly in the Architecture, Engineering, and Construction (AEC) sector to plan and construct new buildings. Currently, BIM does not cover the whole life cycle of a building, especially not inspection and maintenance. Creating damage models needs the building model first, because a defect is dependent on the building component, its properties and material. Hence, a building information model is necessary to obtain meaningful conclusions from damage information. This paper analyzes the requirements, which arise from practice, and the research that has been done in modeling damage and related information for bridges. With a look at damage categories and use cases related to inspection and maintenance, scientific literature is discussed and synthesized. Finally, research gaps and needs are identified and discussed.
Paper-based data acquisition and manual transfer between incompatible software or data formats during inspections of bridges, as done currently, are time-consuming, error-prone, cumbersome, and lead to information loss. A fully digitized workflow using open data formats would reduce data loss, efforts, and the costs of future inspections. On the one hand, existing studies proposed methods to automatize data acquisition and visualization for inspections. These studies lack an open standard to make the gathered data available for other processes. On the other hand, several studies discuss data structures for exchanging damage information among different stakeholders. However, those studies do not cover the process of automatic data acquisition and transfer. This study focuses on a framework that incorporates automatic damage data acquisition, transfer, and a damage information model for data exchange. This enables inspectors to use damage data for subsequent analyses and simulations. The proposed framework shows the potentials for a comprehensive damage information model and related (semi-)automatic data acquisition and processing.
A safe and economic structural design based on the semi-probabilistic concept requires statistically representative safety elements, such as characteristic values, design values, and partial safety factors. Regarding climate loads, the safety levels of current design codes strongly reflect experiences based on former measurements and investigations assuming stationary conditions, i.e. involving constant frequencies and intensities. However, due to climate change, occurrence of corresponding extreme weather events is expected to alter in the future influencing the reliability and safety of structures and their components. Based on established approaches, a systematically refined data-driven methodology for the determination of design parameters considering nonstationarity as well as standardized targets of structural reliability or safety, respectively, is therefore proposed. The presented procedure picks up fundamentals of European standardization and extends them with respect to nonstationarity by applying a shifting time window method. Taking projected snow loads into account, the application of the method is exemplarily demonstrated and various influencing parameters are discussed.
In dieser Arbeit wird eine umfassende Untersuchung der raumakustischen Qualität der Schlosskapelle des Weimarer Residenzschlosses für den Zustand, wie sie zwischen 1658 und 1774 existierte, durchgeführt. Die Schlosskapelle als sakraler Raum innerhalb der Schlossanlage diente der Ausübung religiöser Handlungen und war fester Bestandteil des kulturellen Lebens am Weimarer Hof. Eine wesentliche Bedeutung erlangte sie in diesem Zusammenhang als musikalische Wirkungsstätte Johann Sebastian Bachs. Mit ihrer akustischen Qualität hatte sie einen erheblichen Einfluss auf sein musikalisches Schaffen. Die Untersuchung der raumakustischen Situation stellt damit eine notwendige Grundlage für eine musikwissenschaftliche Einordnung der Schlosskapelle als Aufführungsstätte geistlicher Kompositionen dar. Der raumakustische Zustand der Weimarer Schlosskapelle ist eng mit der baulichen Entwicklung der gesamten Schlossanlage verbunden, die infolge äußerer Einflüsse einem steten Wandel unterlag. Die Umgestaltung der Schlosskapelle zu Beginn des 17. Jahrhunderts erfolgte nach barocken Raumvorstellungen. Einen wesentlichen Einfluss auf die Gestaltung des Innenraumes übte zudem die reformierte Kirche mit ihren liturgischen Anforderungen aus. Die historische Entwicklung der architektonischen Stilepoche sowie der protestantischen Kirche wird in Bezug zu dem akustischen Erscheinungsbild der Schlosskapelle näher untersucht. Ausgehend von der architektonischen Rekonstruktion wird die Raumstruktur der historischen Schlosskapelle in ein Computermodell übertragen, mit dem die Berechnung akustischer Bewertungskriterien möglich ist. Eine ausgiebige Recherche nach verwendeten Materialien und der Ausbildung baulicher Konstruktionen ist dabei die Grundvoraussetzung für aussagekräftige Simulationsergebnisse. Die Wahl der Materialparameter sowie der Einfluss der geometrischen Besonderheiten der Weimarer Schlosskapelle auf die simulierten Schallfeldparameter werden durch die Untersuchung eines Referenzobjektes verifiziert. Dafür werden die akustischen Bewertungskriterien mit einer raumakustischen Messung ermittelt und mit Simulationsergebnissen verglichen. Ein besonderes Interesse bei der Simulation der Schlosskapelle gilt der Nachhallzeit als Charakteristikum der Halligkeit, die in sakralen Gebäuden die auffälligste akustische Raumeigenschaft darstellt. Mit der rekonstruierten Nachhallzeit wird die Schlosskapelle mit barocken Kirchen verglichen und bezüglich ihrer Lage im baustiltypischen Bereich beurteilt. Der Direktschall und die im zeitig folgenden Reflexionen sind bei der raumakustischen Simulation maßgeblicher Gegenstand der Betrachtung. Während der Nachhall das Verschmelzen einzelner Töne zu einem Gesamtklang fördert, ist der Direktschall für die Deutlichkeit von Sprache und der klanglichen Durchsichtigkeit von musikalischen Strukturen verantwortlich. Der Einfluss des Direktschalls wird mit speziellen Energiekriterien beurteilt, mit denen gezielte Aussagen über die akustische Qualität einzelner Platzbereiche möglich sind. Die unterschiedlichen akustischen Anforderungen an die Schlosskapelle bei der jeweiligen Nutzung des Raumes werden mit den Energiekriterien differenziert untersucht und bewertet.
Die Finite-Elemente-Methode entwickelte sich in den letzten beiden Jahrzehnten zu einem wichtigen und mächtigen Werkzeug für Berechnungen im Ingenieurwesen. Waren zu Beginn dieser Entwicklung nur kleine Probleme lösbar, sind mit der heutigen Rechentechnik Systeme mit vielen Tausend Freiheitsgraden berechenbar. Durch diese Entwicklung werden Berechnungen von sehr komplizierten Strukturen möglich. Besonders in der Automobilindustrie kann mit einem solchen Verfahren die Konstruktion von Strukturen verbessert und optimiert werden. Um gute Ergebnisse bei den Berechnungen erzielen zu können müssen Programme entwickelt werden, die entsprechende mathematische Methoden enthalten. Besonders im Maschinenbau, aber auch in anderen Ingenieurbereichen wie dem Bauwesen, werden häufig gekrümmte dünne Schalenstrukturen untersucht. Eine effiziente und logische Konsequenz daraus ist die Nutzung von Schalenelementen innerhalb der FE-Berechnungen. Wird nun noch Wert auf eine realitätsnahe Modellierung gelegt, dann lässt es sich oft nicht vermeiden von der im Bauwesen üblichen Theorie erster Ordnung in eine nichtlineare Berechnungstheorie zu wechseln. Hierfür sind Methoden notwendig, die es vermögen diese Theorie abzubilden. Sollen Schalenstrukturen mit großen Verschiebungen betrachtet werden, ist es notwendig, die linearen Elementformulierungen um die nichtlinearen Ansätze der Strukturmechanik zu erweitern. Die Grundlage dieser Formulierung stellt oft die Lagrange'sche Betrachtungsweise dar, die Berechnungen an Strukturen mit großen Verformungen zulässt. Die Inhalte dieser Formulierung werden in Abschnitt 1.5 dieser Arbeit betrachtet. Räumlich veränderlichen Strukturen, also solche mit großen Verformungen, sind im Allgemeinen mit großen Rotationen verknüpft. Diese Rotationen werden bei Volumenelementen durch die unterschiedliche Verschiebung zweier benachbarter Elementknoten realisiert. Bei der Formulierung von dünnen Schalenelementen wird hingegen die Struktur als gekrümmte Raumfläche betrachtet. Da in Dickenrichtung nur ein Elementknoten zur Verfügung steht, muss die Rotation über eine andere Formulierung in die Berechnung einfließen. Ansätze zu allgemeinen großen Rotationen werden im Kapitel 2 betrachtet und für den Einsatz in einer Elementformulierung vorbereitet. Für die beschriebenen Schalenstrukturen werden häufig vierknotige Elemente genutzt, da mit ihnen Strukturen in einfacher Weise abgebildet werden können. Ein weiterer Vorteil besteht in der sich ergebenden geringen Bandbreite der Elementmatrizen. Diese Elementgruppe besitzt jedoch bei der klassischen isoparametrischen Formulierung einen großen Nachteil, der in der Erzeugung von parasitären Steifigkeitsanteilen besteht. Um dieses Sperrverhalten, was auch als 'Locking' bekannt ist, zu minimieren wurden in der Vergangenheit verschiedene Ansätze entwickelt. Ein sehr effizienter Ansatz zur Minimierung des Transversalschublockings bei bilinearen Schalenelementen stellt das Verfahren der veränderten Verzerrungsverläufe auf Elementebene dar. Dieses Verfahren wird vielfach in der Literatur aufgegriffen und als 'Assumed-Natural-Strain'-Ansatz oder als 'Mixed Interpolation of Tensorial Components' bezeichnet. Dieses Verfahren wird im Abschnitt 1.6 vorgestellt. Das Programmsystem SLang ermöglicht eine Berechnung von Strukturen mittels der Finite-Elemente-Methode. Um mit diesem Programm auch nichtlineare Probleme an Schalentragwerken berechnen zu können, wird im Rahmen dieser Diplomarbeit ein vierknotiges nichtlineares Schalenelement implementiert, das die genannten Ansätze für große Verformungen und finite Rotationen enthält. Für die Vermeidung von Transversalschublocking wird ein ANS-Ansatz in die Formulierung integriert. Das Kapitel 3 beschreibt die Formulierung dieses SHELL4N-Elementes. Dort werden die Elementmatrizen und deren Aufbau ausführlich dargestellt. Einige numerische Berechnungsbeispiele mit diesem neuen Element werden zur Evaluierung im Kapitel 4 dieser Arbeit dargestellt.
The conservation of living heritage sites is a highly complex process. Two factors need careful consideration in order to achieve a balance in the management of such sites: the conservation demands of conservation experts for built heritage and the needs of local people for development of their heritage living space. The complexity of factors involved make for an interesting study of living heritage, taken up by this research in its main case study of the town of Nan in Thailand.
Research into the historical background of Nan and its cultural heritage reveals a living heritage site, which is both unique and diverse. Present day Nan was examined using a variety of analysis tools, which were applied to data from interviews, empirical data, field surveys, and documents, in order to better understand the nature of the living heritage site and changing trends over time. Luang Prabang in Lao PDR, a World Heritage site since 1995, was also selected as a further case study with which to compare Nan’s potential World Heritage status from a point of view of changes to living heritage attributes.
The outcomes of the research indicate the importance of the management of the sites, which can be at risk of losing balance by focusing on one aspect of heritage to the detriment of the other. The conservation perspective, if allowed to dominate, as in Luang Prabang, can cause irreparable damage to the social fabric, where the development needs of the town are not met. This research concludes that a balance of power amongst stakeholders in the collaborative networks managing such sites is vital to sustaining a balance of living heritage attributes.
Heat, gas, and leachate are primary by-products of landfill processes in municipal solid waste landfills. In nuclear waste repository, temperature of the waste also raises due to radioactivity processes. Temperature increase in the repository induces hydro-mechanical processes of its sealing material. Moderate to high temperature is expected to be encountered in the field situation. In this thesis, a study on the thermo-hydro-mechanical behavior of compacted bentonite-sand mixtures which are among the materials proposed to be used as sealing material for landfills and hazardous waste repository is presented. Mixtures of a calcium-type bentonite, Calcigel, and quartz sand were used in this study. Series of tests including suction and swelling pressure measurement, drying-wetting under unconfined and confined conditions were conducted at a moderately high temperature. Tests at room temperature including basic and physico-chemical characterization, microstructure and fabric studies, and osmotic suction were conducted in order to provide insight into understanding the hydro-mechanical processes taking place in the bentonite. The experimental data obtained are presented and compared to the result of the previous tests for the same material performed by other researchers at room temperature. The changes in hydro-mechanical behavior due to elevated temperature were analyzed and discussed based on the suction components of soil which are influenced by temperature. At the end, conclusions concerning the temperature effects on the hydro-mechanical behavior of the materials are drawn and suggestions for future studies are made.
The thesis addresses journalistic, administrative and judicial historical documentation to analyze the links between aridity and geographical imaginaries in the province of Catamarca (Argentina), from a historical point of view. The research aims to contribute to the understanding of the "non-hegemonic" versions of Modernity, its territoriality and the productions of geographic imaginaries that they involve. To provide a broad purpose, it raises as an object of study the ways in which "modern" practices, actors, links, discourses and expectations about the territory are mobilized when they are located in a space in "other" water conditions. those that are intended to "civilize" it.
The general objective of the research is to analyze time-space controversies around water in the city and valley of Catamarca towards 19th and 20th centuries. The specific objectives derived are a) analyzing how various actors are related to waters behavior - in other words, the local water regime – in Catamarca and the meanings built around it. b) to analyze the controversies about the place of Catamarca and its water regime in the local and national geographic imaginary. c) analyze controversies in which the relationships between actors and materialities involved in modernization projects are put into discussion.
These concerns by the experience of the actors and by the historical-spatial imagination of the territory, combined, led to the construction of an interdisciplinary methodology based on tools from anthropology, sociology, geography and history.
This work describes an algorithm and corresponding software for incorporating general nonlinear multiple-point equality constraints in a implicit sparse direct solver. It is shown that direct addressing of sparse matrices is possible in general circumstances, circumventing the traditional linear or binary search for introducing (generalized) constituents to a sparse matrix. Nested and arbitrarily interconnected multiple-point constraints are introduced by processing of multiplicative constituents with a built-in topological ordering of the resulting directed graph. A classification of discretization methods is performed and some re-classified problems are described and solved under this proposed perspective. The dependence relations between solution methods, algorithms and constituents becomes apparent. Fracture algorithms can be naturally casted in this framework. Solutions based on control equations are also directly incorporated as equality constraints. We show that arbitrary constituents can be used as long as the resulting directed graph is acyclic. It is also shown that graph partitions and orderings should be performed in the innermost part of the algorithm, a fact with some peculiar consequences. The core of our implicit code is described, specifically new algorithms for direct access of sparse matrices (by means of the clique structure) and general constituent processing. It is demonstrated that the graph structure of the second derivatives of the equality constraints are cliques (or pseudo-elements) and are naturally included as such. A complete algorithm is presented which allows a complete automation of equality constraints, avoiding the need of pre-sorting. Verification applications in four distinct areas are shown: single and multiple rigid body dynamics, solution control and computational fracture.
Since the end of the 1950s, Italy has focused part of its modernization on the erection of public works. Due to corruption, mafia, and further malpractice, this form of development has occasionally failed, producing a high number of constructions that have remained unfinished for decades. In 2007, the group of artists Alterazioni Video constructed an informal survey in the form of an on-line tool open to public contributions, which revealed that there are 395 unfinished public works in Italy from which 156, approximately 39.5%, are located in Sicily alone. In view of such a statistic, Alterazioni Video opted to coin the term ‘Incompiuto Siciliano’ – literally ‘Sicilian Incompletion’ – to refer to unfinished public works as a formal architectural style. This re-interpretation, which aims to convey the recovered dignity of these ‘modern ruins’, considers unfinished public works a type of heritage with the potential to represent the entirety of Italian society. Furthermore, it goes as far as to say an unfinished public work is ‘Incompiuto Siciliano’ despite being located in another of the Italian regions.
This doctoral dissertation embraces the artists’ argument to develop a complete study of Incompiuto Siciliano by embedding this architectural style/artistic project within the main debates on modern ruins at present. This is important because it is expected to contribute to the revalorization and eventual recommissioning of unfinished sites by validating Incompiuto Siciliano in the realm of academia. Furthermore, this work aspires to be a worthwhile source of information for future investigations dealing with cultural interpretations of incompletion in any other context – a not unreasonable goal considering how unfinished works are one of the key urban topics after the 2008 financial crisis. Hence, this doctoral dissertation uses Incompiuto Siciliano to discuss a different perspective in each of the five chapters and, though these can be read as independent contributions, the objective is that all chapters read together, form a clear, concise, continuous unit. And so it must be said this is not a dissertation about unfinished public works in Italy; this is a dissertation about Incompiuto Siciliano as an artistic response to unfinished public works in Italy – which clearly requires an interdisciplinary analysis involving Urban Studies, Cultural Geography, Contemporary Archaeology, Critical Heritage and Visual Arts.
Resonance vibration of structures is an unpleasant incident that can be conventionally avoided by using a Tuned Mass Damper (TMD). The scope of this paper contains the utilization of engineered inclusions in concrete as damping aggregates to suppress resonance vibration similar to a TMD. The inclusions are composed of a stainless-steel core with a spherical shape coated with silicone. This configuration has been the subject of several studies and it is best known as Metaconcrete. This paper presents the procedure of a free vibration test conducted with two small-scaled concrete beams. The beams exhibited a higher damping ratio after the core-coating element was secured to them. Subsequently, two meso-models of small-scaled beams were created: one representing conventional concrete and the other representing concrete with the core-coating inclusions. The frequency response curves of the models were obtained. The change in the response peak verified the ability of the inclusions to suppress the resonance vibration. This study concludes that the core-coating inclusions can be utilized in concrete as damping aggregates.
Experimental Validation of Dynamic Response of Small-Scale Metaconcrete Beams at Resonance Vibration
(2023)
Structures and their components experience substantially large vibration amplitudes at resonance, which can cause their failure. The scope of this study is the utilization of silicone-coated steel balls in concrete as damping aggregates to suppress the resonance vibration. The heavy steel cores oscillate with a frequency close to the resonance frequency of the structure. Due to the phase difference between the vibrations of the cores and the structure, the cores counteract the vibration of the structure. The core-coating inclusions are randomly distributed in concrete similar to standard aggregates. This mixture is referred to as metaconcrete. The main goal of this work is to validate the ability of the inclusions to suppress mechanical vibration through laboratory experiments. For this purpose, two small-scale metaconcrete beams were cast and tested. In a free vibration test, the metaconcrete beams exhibited a larger damping ratio compared to a similar beam cast from conventional concrete. The vibration amplitudes of the metaconcrete beams at resonance were measured with a frequency sweep test. In comparison with the conventional concrete beam, both metaconcrete beams demonstrated smaller vibration amplitudes. Both experiments verified an improvement in the dynamic response of the metaconcrete beams at resonance vibration.
In this thesis, a generic model for the post-failure behavior of concrete in tension is proposed. A mesoscale model of concrete representing the heterogeneous nature of concrete is formulated. The mesoscale model is composed of three phases: aggregate, mortar matrix, and the Interfacial Transition Zone between them. Both local and non-local formulations of the damage are implemented and the results are compared. Three homogenization schemes from the literature are employed to obtain the homogenized constitutive relationship for the macroscale model. Three groups of numerical examples are provided.
Within the scope of literature, the influence of openings within the infill walls that are bounded by a reinforced concrete frame and excited by seismic drift forces in both in- and out-of-plane direction is still uncharted. Therefore, a 3D micromodel was developed and calibrated thereafter, to gain more insight in the topic. The micromodels were calibrated against their equivalent physical test specimens of in-plane, out-of-plane drift driven tests on frames with and without infill walls and openings, as well as out-of-plane bend test of masonry walls. Micromodels were rectified based on their behavior and damage states. As a result of the calibration process, it was found that micromodels were sensitive and insensitive to various parameters, regarding the model’s behavior and computational stability. It was found that, even within the same material model, some parameters had more effects when attributed to concrete rather than on masonry. Generally, the in-plane behavior of infilled frames was found to be largely governed by the interface material model. The out-of-plane masonry wall simulations were governed by the tensile strength of both the interface and masonry material model. Yet, the out-of-plane drift driven test was governed by the concrete material properties.
Stanford Anderson is Professor of History and Architecture and was Head of the Department of Architecture from 1991 through 2004. He was director of MIT’s PhD program in History, Theory and Criticism of Architecture, Art and Urban Form from its founding in 1974 to 1991 and in 1995-96. Anderson’s research and writing concern architectural theory, early modern architecture in northern Europe, American architecture and urbanism, and epistemology and historiography. He has organized numerous professional conferences and served on the editorial boards of Assemblage, Journal of Architectural Education, Places, and The MIT Press. In addition to numerous articles, his books are Planning for Diversity and Choice, On Streets, and Hermann Muthesius: Style-Architecture and Building Art. He is co-author of Kay Fisker. Peter Behrens and a New Architecture for the Twentieth Century appeared in 2000 and Eladio Dieste: Innovation in Structural Art in 2004. In 1997, The MIT Press published a collection of essays in his honor, edited by Martha Pollak: The Education of the Architect: Historiography, Urbanism, and the Growth of Knowledge. He was a Fulbright fellow at the Technische Hochschule in Munich and subsequently a fellow of the John Simon Guggenheim Foundation and the American Council of Learned Societies. Anderson received his bachelor’s degree from the University of Minnesota, his master’s in architecture from the University of California at Berkeley, and his doctoral degree in the history of art from Columbia University in New York City.
Im Rahmen dieser Arbeit wurde der Energieeintrag beim Laserstrahl-schweißen untersucht. Das verwendete Material ist ein Stahl der Sorte S355 J2G3. Für das FE-Programm SYSWELD sind verschiedene Wärmequellen entwickelt, erprobt und über Temperaturfelder mit einander verglichen wurden. Dabei kamen unterschiedliche Netz-varianten zum Einsatz. Der Energieeintrag wurde abzüglich der Verluste die beim Laserstrahlschweißen entstehen betrachtet, dabei sind die Verluste aus Transmission, Reflexion und Metalldampf separat betrachtet wurden. Es wurden auch Materialparameter wie: Verdampfungsenthalpie, spezifische Wärmekapazität sowie Wärmeleit-fähigkeit analysiert. Die Ergebnisse zur Anpassung des Energieeintrages waren im Gegensatz zu den Materialparametern noch ausbaufähig.
Der vorliegende Beitrag ist in zwei thematische Teilebereiche gegliedert. Der erste Teil beschäftigt sich mit der Analyse von Graphen, insbesondere von Graphen, die Straßennetzwerke repräsentieren. Hierzu werden Methoden aus der Graphentheorie angewendet und Kenngrößen aus der Space Syntax Methode ausgewertet. Ein Framework, welches basierend auf der Graphentheorie in Architektur und Stadtplanung Einzug gehalten hat, ist die Space Syntax Methode. Sie umfasst die Ableitung unterschiedlicher Kenngrößen eines Graphen bzw. Netzwerkes, wodurch eine Analyse für architektonische und stadtplanerische Zwecke ermöglicht wird.
Der zweite Teil dieses Berichts beschäftigt sich mit der Generierung von Graphen, insbe-sondere der von Straßennetzwerkgraphen. Die generativen Methoden basieren zum Teil auf den gewonnenen Erkenntnissen der Analyse von Straßennetzwerken. Es werden unterschiedliche Ansätze untersucht, um verschiedene Parameterwerte zur Generierung von Straßengraphen festzulegen. Als Ergebnis der Arbeiten ist ein Softwaretool entstanden, welches es erlaubt, auf Grundlage einer Voronoi-Tesselierung realistische Straßennetzwerkgraphen zu erzeugen.
Web applications that are based on user-generated content are often criticized for containing low-quality information; a popular example is the online encyclopedia Wikipedia. The major points of criticism pertain to the accuracy, neutrality, and reliability of information. The identification of low-quality information is an important task since for a huge number of people around the world it has become a habit to first visit Wikipedia in case of an information need. Existing research on quality assessment in Wikipedia either investigates only small samples of articles, or else deals with the classification of content into high-quality or low-quality. This thesis goes further, it targets the investigation of quality flaws, thus providing specific indications of the respects in which low-quality content needs improvement. The original contributions of this thesis, which relate to the fields of user-generated content analysis, data mining, and machine learning, can be summarized as follows:
(1) We propose the investigation of quality flaws in Wikipedia based on user-defined cleanup tags. Cleanup tags are commonly used in the Wikipedia community to tag content that has some shortcomings. Our approach is based on the hypothesis that each cleanup tag defines a particular quality flaw.
(2) We provide the first comprehensive breakdown of Wikipedia's quality flaw structure. We present a flaw organization schema, and we conduct an extensive exploratory data analysis which reveals (a) the flaws that actually exist, (b) the distribution of flaws in Wikipedia, and, (c) the extent of flawed content.
(3) We present the first breakdown of Wikipedia's quality flaw evolution. We consider the entire history of the English Wikipedia from 2001 to 2012, which comprises more than 508 million page revisions, summing up to 7.9 TB. Our analysis reveals (a) how the incidence and the extent of flaws have evolved, and, (b) how the handling and the perception of flaws have changed over time.
(4) We are the first who operationalize an algorithmic prediction of quality flaws in Wikipedia. We cast quality flaw prediction as a one-class classification problem, develop a tailored quality flaw model, and employ a dedicated one-class machine learning approach. A comprehensive evaluation based on human-labeled Wikipedia articles underlines the practical applicability of our approach.
TRANSFORMING TACIT KNOWLEDGE
(2011)
Sabine Ammon studied architecture and philosophy at the Technische Universität Berlin. Study and research visits led her to the University of London, Harvard University and ETH Zürich. Furthermore, she practised building design as a freelance architect. Her dissertation “Wissen verstehen. Perspektiven einer prozessualen Theorie der Erkenntnis”, Weilerswist 2009, develops a theory of knowledge, based on the philosophy of symbols. In her current research project she explores the epistemic dimension of architectural design processes.
Energy‐Efficient Method for Wireless Sensor Networks Low‐Power Radio Operation in Internet of Things
(2020)
The radio operation in wireless sensor networks (WSN) in Internet of Things (IoT)applications is the most common source for power consumption. Consequently, recognizing and controlling the factors affecting radio operation can be valuable for managing the node power consumption. Among essential factors affecting radio operation, the time spent for checking the radio is of utmost importance for monitoring power consumption. It can lead to false WakeUp or idle listening in radio duty cycles and ContikiMAC. ContikiMAC is a low‐power radio duty‐cycle protocol in Contiki OS used in WakeUp mode, as a clear channel assessment (CCA) for checking radio status periodically. This paper presents a detailed analysis of radio WakeUp time factors of ContikiMAC. Furthermore, we propose a lightweight CCA (LW‐CCA) as an extension to ContikiMAC to reduce the Radio Duty‐Cycles in false WakeUps and idle listening though using dynamic received signal strength indicator (RSSI) status check time. The simulation results in the Cooja simulator show that LW‐CCA reduces about 8% energy consumption in nodes while maintaining up to 99% of the packet delivery rate (PDR).
The key objective of this research is to study fracture with a meshfree method, local maximum entropy approximations, and model fracture in thin shell structures with complex geometry and topology. This topic is of high relevance for real-world applications, for example in the automotive industry and in aerospace engineering. The shell structure can be described efficiently by meshless methods which are capable of describing complex shapes as a collection of points instead of a structured mesh. In order to find the appropriate numerical method to achieve this goal, the first part of the work was development of a method based on local maximum entropy (LME)
shape functions together with enrichment functions used in partition of unity methods to discretize problems in linear elastic fracture mechanics. We obtain improved accuracy relative to the standard extended finite element method (XFEM) at a comparable computational cost. In addition, we keep the advantages of the LME shape functions,such as smoothness and non-negativity. We show numerically that optimal convergence (same as in FEM) for energy norm and stress intensity factors can be obtained through the use of geometric (fixed area) enrichment with no special treatment of the nodes
near the crack such as blending or shifting.
As extension of this method to three dimensional problems and complex thin shell structures with arbitrary crack growth is cumbersome, we developed a phase field model for fracture using LME. Phase field models provide a powerful tool to tackle moving interface problems, and have been extensively used in physics and materials science. Phase methods are gaining popularity in a wide set of applications in applied science and engineering, recently a second order phase field approximation for brittle fracture has gathered significant interest in computational fracture such that sharp cracks discontinuities are modeled by a diffusive crack. By minimizing the system energy with respect to the mechanical displacements and the phase-field, subject to an irreversibility condition to avoid crack healing, this model can describe crack nucleation, propagation, branching and merging. One of the main advantages of the phase field modeling of fractures is the unified treatment of the interfacial tracking and mechanics, which potentially leads to simple, robust, scalable computer codes applicable to complex systems. In other words, this approximation reduces considerably the implementation complexity because the numerical tracking of the fracture is not needed, at the expense of a high computational cost. We present a fourth-order phase field model for fracture based on local maximum entropy (LME) approximations. The higher order continuity of the meshfree LME approximation allows to directly solve the fourth-order phase field equations without splitting the fourth-order differential equation into two second order differential equations. Notably, in contrast to previous discretizations that use at least a quadratic basis, only linear completeness is needed in the LME approximation. We show that the crack surface can be captured more accurately in the fourth-order model than the second-order model. Furthermore, less nodes are needed for the fourth-order model to resolve the crack path. Finally, we demonstrate the performance of the proposed meshfree fourth order phase-field formulation for 5 representative numerical examples. Computational results will be compared to analytical solutions within linear elastic fracture mechanics and experimental data for three-dimensional crack propagation.
In the last part of this research, we present a phase-field model for fracture in Kirchoff-Love thin shells using the local maximum-entropy (LME) meshfree method. Since the crack is a natural outcome of the analysis it does not require an explicit representation and tracking, which is advantageous over techniques as the extended finite element method that requires tracking of the crack paths. The geometric description of the shell is based on statistical learning techniques that allow dealing with general point set surfaces avoiding a global parametrization, which can be applied to tackle surfaces of complex geometry and topology. We show the flexibility and robustness of the present methodology for two examples: plate in tension and a set of open connected
pipes.
SYSBAT - An Application to the Building ProductionBased on Computer Supported Cooperative Work
(2003)
Our proposed solution is to enable partners of a construction project to share all the technical data produced and handled during the building production process by building a system through the use of internet technology. The system links distributed databases and allows building partners to access remotely and manipulate specific information. It provides an updated building representation that is being enriched and refined all along the building production process. A recent collaboration with Nemetschek France (subsidiary company of Nemetschek AG, AEC CAD software leader) focus on a building product repository available in a web context. The aim is to help building project actors to choose a technical solution that fits its professional needs, and maintain our information system with up to date information. It starts with the possibility to build on line building product catalogs, in order to link Allplan CAD entities with building technical features. This paper presents the conceptual approaches on which our information system is built. Starting from a general organization diagram organization, we focus on the product and the description branches of construction works (including last IFC model specifications). Our aim is to add decisional support to the construction works selection process. To do so, we consider the actor's role upon the system and the pieces of information each one needs to achieve a given task.
Visually impaired is a common problem for human life in the world wide. The projector-based AR technique has ability to change appearance of real object, and it can help to improve visibility for visually impaired. We propose a new framework for the appearance enhancement with the projector camera system that employed model predictive controller. This framework enables arbitrary image processing such as photo-retouch software in the real world and it helps to improve visibility for visually impaired. In this article, we show the appearance enhancement result of Peli's method and Wolffshon's method for the low vision, Jefferson's method for color vision deficiencies. Through experiment results, the potential of our method to enhance the appearance for visually impaired was confirmed as same as appearance enhancement for the digital image and television viewing.
The node moving and multistage node enrichment adaptive refinement procedures are extended in mixed discrete least squares meshless (MDLSM) method for efficient analysis of elasticity problems. In the formulation of MDLSM method, mixed formulation is accepted to avoid second-order differentiation of shape functions and to obtain displacements and stresses simultaneously. In the refinement procedures, a robust error estimator based on the value of the least square residuals functional of the governing differential equations and its boundaries at nodal points is used which is inherently available from the MDLSM formulation and can efficiently identify the zones with higher numerical errors. The results are compared with the refinement procedures in the irreducible formulation of discrete least squares meshless (DLSM) method and show the accuracy and efficiency of the proposed procedures. Also, the comparison of the error norms and convergence rate show the fidelity of the proposed adaptive refinement procedures in the MDLSM method.
Humans are able to think, to feel, and to sense. We are also able to compute but not very well. In contrast, computers are giants in computing. Yet, they can not do anything else besides computing. Appropriate combinations of the different gifts and strengths of human and computer may result in impressive performances. In the 3-Hirn approach one human and two computers are involved. On the computers different programs are running. The human starts the machines and inspects the solutions they propose. He compares these candidate solutions and finally decides for one of the alternatives. So, the human makes the final choice from a small number of computer proposals. In performance-oriented chess, 3-Hirn combinations consisting of an amateur player and commer-cial software have reached world class level. 3-Hirn is a Decision Support System with Multiple Choice Structure. Such Multiple Choice Systems will be exhibited and discussed.
Koulu - Schule auf Finnisch : Funktions-, Raum- und Gestaltungskonzepte für neue Schulen in Finnland
(2008)
Beginnend mit einem historischen Rückblick auf die Entwicklung des Schulbaus in Finnland sowie einen Überblick zu den rechtlichen und organisatorischen Rahmenbedingungen für den Schulbau, wird in der Untersuchung dargestellt, dass in Finnland ein traditioneller Grundkonsens darüber besteht, dass Bildung eine besonders wichtige gesellschaftliche Aufgabe darstellt und Art sowie Umfang ihrer Erfüllung von herausragender Bedeutung für die Zukunft des Landes ist. Daher wird dem Thema „Schule“ nicht nur in der Theorie, sondern auch im praktischen Alltag ein ausgesprochen hoher Stellenwert beigemessen. Auch die Lernumgebung wird mit besonderer Sorgfalt gestaltet. Die Gestaltung zahlreicher finnischer Bildungsanstalten ist transparent und flexibel. Das Schulgebäude ist somit für zukünftige Anforderungen leicht adaptierbar. Zu diesem Zweck wird architektonische Vielfalt mit einem hohen Grad an Funktionalität verbunden, die gleichzeitig lokale Gegebenheiten und Bedürfnisse berücksichtigt. Prägend für die Funktions-, Raum- und Gestaltungskonzepte sind insbesondere der Baukörper und seine Form, die Erschließung der Schule und die Raumfolge innerhalb des Gebäudes, die Raumfunktion und Nutzung einzelner Bereiche sowie ein hohes Maß an räumlich-visueller Kommunikation und Transparenz, sowohl innerhalb der Klassencluster als auch zwischen unterschiedlichen Funktionsbereichen der Schulen. Diese Parameter wurden in der vorliegenden Studie anhand von zahlreichen Fallbeispielen eingehend untersucht und dokumentiert. Durch einen frühzeitig geführten, intensiven Dialog zwischen Behörden, Pädagogen und Architekten sind räumliche Konzepte entstanden, die das Erlernen von sozialen Kompetenzen, Teamfähigkeit und Gruppenarbeit unterstützen und fördern.
Schwerpunkt dieser Arbeit ist die Untersuchung des Ausbruchverhaltens von unbewehrten Porenbetonplatten bei konzentrierter Lasteintragung in Randnähe. In der Praxis tritt diese Problematik bei Befestigungen oder Verankerungen auf, die eine punktuelle Beanspruchung bewirken. Hauptziel der durchgeführten experimentellen und numerischen Untersuchungen war das Erkennen von Gesetzmäßigkeiten für Versagenserscheinungen und für Bruchlasten in Abhängigkeit von variierenden Geometrie- und Materialparametern. Dabei waren Größe und Lage der Lasteinleitungsstelle sowie die Materialfestigkeit die wichtigsten Einflussfaktoren. Von besonderem Interesse war auch das spröde Verhalten des Porenbetonmaterials auf das Ausbruchverhalten. Die Arbeit gliedert sich in drei Hauptteile: die Experimente mit anschließend weiterführenden numerischen Untersuchungen, sowie Bemessungskonzepten mit Ausbruchgleichungen. Ein weiteres Kapitel behandelt die Zugfestigkeit von Porenbeton. Die Experimente wurde an für Wand- oder Deckenplatten originaldicken Versuchskörpern durchgeführt. Dabei waren die Lagerbedingungen so festgelegt, dass sich möglichst ein ungestörter Ausbruchkörper ausbilden konnte. Numerische Spannungsuntersuchungen über eine räumliche Idealisierung der Versuchskörper mit dem Finite- Element- Programmsystem ANSYS gaben Aufschlüsse über Ort und Größe von bruchverursachenden Spannungen. Des weiteren wurden über die Versuchsergebnisse hinaus Berechnungen über den Einfluss von Variationen bei der Plattengeometrie durchgeführt. Es wurden Betrachtungen über die Zugfestigkeit als einen maßgebenden Faktor für das Ausbruchverhalten geführt. Numerische Risssimulationen gaben Aufschluss über den Spannungszustand und den Ablauf der Rissentwicklung.
Performance assessment of a ductless personalized ventilation system using a validated CFD model
(2018)
The aim of this study is twofold: to validate a computational fluid dynamics (CFD) model, and then to use the validated model to evaluate the performance of a ductless personalized ventilation (DPV) system. To validate the numerical model, a series of measurements was conducted in a climate chamber equipped with a thermal manikin. Various turbulence models, settings, and options were tested; simulation results were compared to the measured data to determine the turbulence model and solver settings that achieve the best agreement between the measured and simulated values. Subsequently, the validated CFD model was then used to evaluate the thermal environment and indoor air quality in a room equipped with a DPV system combined with displacement ventilation. Results from the numerical model were then used to quantify thermal sensation and comfort using the UC Berkeley thermal comfort model.
Personalized ventilation (PV) is a mean of delivering conditioned outdoor air into the breathing zone of the occupants. This study aims to qualitatively investigate the personalized flows using two methods of visualization: (1) schlieren imaging using a large schlieren mirror and (2) thermography using an infrared camera. While the schlieren imaging was used to render the velocity and mass transport of the supplied flow, thermography was implemented to visualize the air temperature distribution induced by the PV. Both studies were conducted using a thermal manikin to simulate an occupant facing a PV outlet. As a reference, the flow supplied by an axial fan and a cased axial fan was visualized with the schlieren system as well and compared to the flow supplied by PV. Schlieren visualization results indicate that the steady, low-turbulence flow supplied by PV was able to penetrate the thermal convective boundary layer encasing the manikin's body, providing clean air for inhalation. Contrarily, the axial fan diffused the supplied air over a large target area with high turbulence intensity; it only disturbed the convective boundary layer rather than destroying it. The cased fan supplied a flow with a reduced target area which allowed supplying more air into the breathing zone compared to the fan. The results of thermography visualization showed that the supplied cool air from PV penetrated the corona-shaped thermal boundary layer. Furthermore, the supplied air cooled the surface temperature of the face, which indicates the large impact of PV on local thermal sensation and comfort.
This study investigates the flow supplied by personalized ventilation (PV) by means of anemometer measurements and schlieren visualization. The study was conducted using a thermal manikin to simulate a seated occupant facing a PV outlet. Air velocity was measured at multiple points in the flow field; the collected velocity values were used to calculate the turbulence intensity. Results indicated that PV was supplying air with low turbulence intensity that was able to penetrate the convective boundary layer of the manikin to supply clean air for inhalation. The convective boundary layer, however, obstructed the supplied flow and reduced its velocity by a total of 0.26 m/s. The PV flow preserved its value until about 10 cm from the face where velocity started to drop. Further investigations were conducted to test a PV diffuser with a relatively large outlet diameter (18 cm). This diffuser was developed using 3d-modelling and 3d-printing. The diffuser successfully distributed the flow over the larger outlet area. However, the supplied velocity and turbulence fields were not uniform across the section.
Personalisierte Lüftung (PL) kann die thermische Behaglichkeit sowie die Qualität der eingeatmeten Atemluft verbessern, in dem jedem Arbeitsplatz Frischluft separat zugeführt wird. In diesem Beitrag wird die Wirkung der PL auf die thermische Behaglichkeit der Nutzer unter sommerlichen Randbedingungen untersucht. Hierfür wurden zwei Ansätze zur Bewertung des Kühlungseffekts der PL untersucht: basierend auf (1) der äquivalenten Temperatur und (2) dem thermischen Empfinden. Grundlage der Auswertung sind in einer Klimakammer gemessene sowie numerisch simulierte Daten. Vor der Durchführung der Simulationen wurde das numerische Modell zunächst anhand der gemessenen Daten validiert. Die Ergebnisse zeigen, dass der Ansatz basierend auf dem thermischen Empfinden zur Evaluierung des Kühlungseffekts der PL sinnvoller sein kann, da bei diesem die komplexen physiologischen Faktoren besser berücksichtigt werden.
The performance of ductless personalized ventilation (DPV) was compared to the performance of a typical desk fan since they are both stand-alone systems that allow the users to personalize their indoor environment. The two systems were evaluated using a validated computational fluid dynamics (CFD) model of an office room occupied by two users. To investigate the impact of DPV and the fan on the inhaled air quality, two types of contamination sources were modelled in the domain: an active source and a passive source. Additionally, the influence of the compared systems on thermal comfort was assessed using the coupling of CFD with the comfort model developed by the University of California, Berkeley (UCB model). Results indicated that DPV performed generally better than the desk fan. It provided better thermal comfort and showed a superior performance in removing the exhaled contaminants. However, the desk fan performed better in removing the contaminants emitted from a passive source near the floor level. This indicates that the performance of DPV and desk fans depends highly on the location of the contamination source. Moreover, the simulations showed that both systems increased the spread of exhaled contamination when used by the source occupant.
This study investigates the performance of two systems: personalized ventilation (PV) and ductless personalized ventilation (DPV). Even though the literature indicates a compelling performance of PV, it is not often used in practice due to its impracticality. Therefore, the present study assesses the possibility of replacing the inflexible PV with DPV in office rooms equipped with displacement ventilation (DV) in the summer season. Numerical simulations were utilized to evaluate the inhaled concentration of pollutants when PV and DPV are used. The systems were compared in a simulated office with two occupants: a susceptible occupant and a source occupant. Three types of pollution were simulated: exhaled infectious air, dermally emitted contamination, and room contamination from a passive source. Results indicated that PV improved the inhaled air quality regardless of the location of the pollution source; a higher PV supply flow rate positively impacted the inhaled air quality. Contrarily, the performance of DPV was highly sensitive to the source location and the personalized flow rate. A higher DPV flow rate tends to decrease the inhaled air quality due to increased mixing of pollutants in the room. Moreover, both systems achieved better results when the personalized system of the source occupant was switched off.
Physical exercise demonstrates a special case of aerosol emission due to its associated elevated breathing rate. This can lead to a faster spread of airborne viruses and respiratory diseases. Therefore, this study investigates cross-infection risk during training. Twelve human subjects exercised on a cycle ergometer under three mask scenarios: no mask, surgical mask, and FFP2 mask. The emitted aerosols were measured in a grey room with a measurement setup equipped with an optical particle sensor. The spread of expired air was qualitatively and quantitatively assessed using schlieren imaging. Moreover, user satisfaction surveys were conducted to evaluate the comfort of wearing face masks during training. The results indicated that both surgical and FFP2 masks significantly reduced particles emission with a reduction efficiency of 87.1% and 91.3% of all particle sizes, respectively. However, compared to surgical masks, FFP2 masks provided a nearly tenfold greater reduction of the particle size range with long residence time in the air (0.3–0.5 μm). Furthermore, the investigated masks reduced exhalation spreading distances to less than 0.15 m and 0.1 m in the case of the surgical mask and FFP2 mask, respectively. User satisfaction solely differed with respect to perceived dyspnea between no mask and FFP2 mask conditions.
This dataset presents the numerical analysis of the heat and moisture transport through a facade equipped with a living wall system designated for greywater treatment. While such greening systems provide many environmental benefits, they involve pumping large quantities of water onto the wall assembly, which can increase the risk of moisture in the wall as well as impaired energetic performance due to increased thermal conductivity with increased moisture content in the building materials. This dataset was acquired through numerical simulation using the coupling of two simulation tools, namely Envi-Met and Delphin. This coupling was used to include the complex role the plants play in shaping the near-wall environmental parameters in the hygrothermal simulations. Four different wall assemblies were investigated, each assembly was assessed twice: with and without the living wall. The presented data include the input and output parameters of the simulations, which were presented in the co-submitted article [1].
Besides their multiple known benefits regarding urban microclimate, living walls can be used as decentralized stand-alone systems to treat greywater locally at the buildings. While this offers numerous environmental advantages, it can have a considerable impact on the hygrothermal performance of the facade as such systems involve bringing large quantities of water onto the facade. As it is difficult to represent complex entities such as plants in the typical simulation tools used for heat and moisture transport, this study suggests a new approach to tackle this challenge by coupling two tools: ENVI-Met and Delphin. ENVI-Met was used to simulate the impact of the plants to determine the local environmental parameters at the living wall. Delphin, on the other hand, was used to conduct the hygrothermal simulations using the local parameters calculated by ENVI-Met. Four wall constructions were investigated in this study: an uninsulated brick wall, a precast concrete plate, a sandy limestone wall, and a double-shell wall. The results showed that the living wall improved the U-value, the exterior surface temperature, and the heat flux through the wall. Moreover, the living wall did not increase the risk of moisture in the wall during winter and eliminated the risk of condensation.