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- 2006 (173) (remove)
VARIATION OF ROTATIONAL RESTRAINT IN GRID DECK CONNECTION DUE TO CORROSION DAMAGE AND STRENGTHENING
(2006)
The approach to assessment of rotational restraint of stringer-to-crossbeam connection in a deck of 100-year old steel truss bridge is presented. Sensitivity of rotational restraint coefficient of the connection to corrosion damage and strengthening is analyzed. Two criteria of the assessment of the rotational restraint coefficient are applied: static and kinematic one. The former is based on bending moment distribution in the considered member, the latter one – on the member rotation at the given joint. 2D-element model of finite element method is described: webs and flanges are modeled with shell elements, while rivets in the connection – with system of beam and spring elements. The method of rivet modeling is verified by T-stub connection test results published in literature. FEM analyses proved that recorded extent of corrosion damage does not alter the initial rotational restraint of stringer-to-crossbeam connection. Strengthening of stringer midspan influences midspan bending moment and stringer end rotation in a different way. Usually restoring member load bearing capacity means strengthening its critical regions (where the highest stress levels occur). This alters flexural stiffness distribution over member length and influences rotational restraint at its connection to other members. The impact depends on criterion chosen for rotational restraint coefficient assessment.
Adopting the European laws concerning environmental protection will require sustained efforts of the authorities and communities from Romania; implementing modern solutions will become a fast and effective option for the improvement of the functioning systems, in order to prevent disasters. As a part of the urban infrastructure, the drainage networks of pluvial and residual waters are included in the plan of promoting the systems which protect the environmental quality, with the purpose of integrated and adaptive management. The paper presents a distributed control system for sewer network of Iasi town. Unsatisfactory technical state of the actual sewer system is exposed, focusing on objectives related to implementation of the control system. The proposed distributed control system of Iasi drainage network is based on the implementation of the hierarchic control theory for diagnose, sewer planning and management. There are proposed two control levels: coordinating and local execution. Configuration of the distributed control system, including data acquisition and conversion equipment, interface characteristics, local data bus, data communication network, station configuration are widely described. The project wish to be an useful instrument for the local authorities in the preventing and reducing the impact of future natural disasters over the urban areas by means of modern technologies.
Interval analysis extends the concept of computing with real numbers to computing with real intervals. As a consequence, some interesting properties appear, such as the delivery of guaranteed results or confirmed global values. The former property is given in the sense that unknown numerical values are in known to lie in a computed interval. The latter property states that the global minimum value, for example, of a given function is also known to be contained in a interval (or a finite set of intervals). Depending upon the amount computation effort invested in the calculation, we can often find tight bounds on these enclosing intervals. The downside of interval analysis, however, is the mathematically correct, but often very pessimistic size of the interval result. This is in particularly due to the so-called dependency effect, where a single variable is used multiple times in one calculation. Applying interval analysis to structural analysis problems, the dependency has a great influence on the quality of numerical results. In this paper, a brief background of interval analysis is presented and shown how it can be applied to the solution of structural analysis problems. A discussion of possible improvements as well as an outlook to parallel computing is also given.
Der Begriff der Zuverlässigkeit spielt eine zentrale Rolle bei der Bewertung von Verkehrsnetzen. Aus der Sicht der Nutzer des öffentlichen Personennahverkehrs (ÖPNV) ist eines der wichtigsten Kriterien zur Beurteilung der Qualität des Liniennetzes, ob es möglich ist, mit einer großen Sicherheit das Reiseziel in einer vorgegebenen Zeit zu erreichen. Im Vortrag soll dieser Zuverlässigkeitsbegriff mathematisch gefasst werden. Dabei wird zunächst auf den üblichen Begriff der Zuverlässigkeit eines Netzes im Sinne paarweiser Zusammenhangswahrscheinlichkeiten eingegangen. Dieser Begriff wird erweitert durch die Betrachtung der Zuverlässigkeit unter Einbeziehung einer maximal zulässigen Reisezeit. In vergangenen Arbeiten hat sich die Ring-Radius-Struktur als bewährtes Modell für die theoretische Beschreibung von Verkehrsnetzen erwiesen. Diese Überlegungen sollen nun durch Einbeziehung realer Verkehrsnetzstrukturen erweitert werden. Als konkretes Beispiel dient das Straßenbahnnetz von Krakau. Hier soll insbesondere untersucht werden, welche Auswirkungen ein geplanter Ausbau des Netzes auf die Zuverlässigkeit haben wird. This paper is involved with CIVITAS-CARAVEL project: "Clean and better transport in cites". The project has received research funding from the Community's Sixth Framework Programme. The paper reflects only the author's views and the Community is not liable for any use that may be made of the information contained therein.
Immer häufiger setzen Bund, Länder und Kommunen auf die Zusammenarbeit zwi-schen öffentlicher Hand und Privatwirtschaft. Insbesondere in den Bereichen Sport, Freizeit und Kultur sagen die kommunalen Entscheidungsträger dem Instrument PPP eine große Zukunft voraus. In der vorliegenden Diplomarbeit soll die Realisierbarkeit von PPP in einem regiona-len Bädernetzwerk untersucht werden. Da zu diesem Thema bisher keine Untersu-chung durchgeführt wurde, erfolgte einleitend in die Arbeit eine Marktübersicht, in der die geschichtliche Entwicklung des Badewesens, die heutigen Strukturen und Anforderungen an Bäder sowie eine Kategorisierung der Schwimmstätten nach An-zahl und Typus dargestellt werden. Im zweiten Kapitel wird ein Extrakt der derzeitigen und künftigen Marktgegebenhei-ten vorgenommen. Diesem liegt eine Marktabfrage nebst -auswertung zugrunde, welche bei privatrechtlich firmierten Bäderbetreibern recherchiert wurde. Im darauf folgenden dritten Kapitel werden Varianten für eine regionale Zusammen-arbeit dargelegt. Neben allgemeinen Ausführungen und individuellen Bestimmungen sind Voraussetzungen sowie Vor- und Nachteile der einzelnen Alternativen be-schrieben. Um den Leser mit dem Instrument PPP vertraut zu machen, gibt der vierte Teil eine Einführung in dieses Thema. Hierbei wird der Begriff PPP definiert, eine Abgrenzung des PPP-Inhabermodells, PPP-Konzessionsmodells und des PPP-Gesellschaftsmodells vorgenommen sowie Erläuterungen hinsichtlich rechtlicher und finanzieller Rahmenbedingungen gegeben. Abgeschlossen wird dieses Kapitel mit einer Auflistung der Vor- und Nachteile von PPP. Das fünfte Kapitel befasst sich mit der Gegenüberstellung der o.g. drei PPP-Vertragsmodelle. Vorrangig werden die Unterschiede im Risiko sowie finanzielle und rechtliche Differenzen herausgearbeitet. Betrachtet wird bspw. der Defizitausgleich, die Förderfähigkeit, das Vergabe- und Haushaltsrecht u. v. m. Die Umsetzbarkeit von PPP in einem regionalen Bädernetzwerk wird als vorletztes und damit sechstes Kapitel in dieser Diplomarbeit analysiert. Innerhalb dieses Kapi-tels werden positive Aussichten sowie Problemfelder aus der Sichtweise der Privat-wirtschaft und der öffentlichen Hand näher beleuchtet. Im siebten und abschließenden Kapitel wird ein Gesamtresümee die Arbeit abrun-den. Es kann bereits jetzt gesagt werden, dass ein Ergebnis, welches zu einer fina-len Aussage gelangt und bestimmten Projekten eine uneingeschränkte PPP-Eignung attestiert, nicht gegeben werden kann. Dafür ist jedes Projekt zu verschieden und bedarf einer individuellen Untersuchung.
The execution of project activities generally requires the use of (renewable) resources like machines, equipment or manpower. The resource allocation problem consists in assigning time intervals to the execution of the project activities while taking into account temporal constraints between activities emanating from technological or organizational requirements and costs incurred by the resource allocation. If the total procurement cost of the different renewable resources has to be minimized we speak of a resource investment problem. If the cost depends on the smoothness of the resource utilization over time the underlying problem is called a resource levelling problem. In this paper we consider a new tree-based enumeration method for solving resource investment and resource levelling problems exploiting some fundamental properties of spanning trees. The enumeration scheme is embedded in a branch-and-bound procedure using a workload-based lower bound and a depth first search. Preliminary computational results show that the proposed procedure is promising for instances with up to 30 activities.
Digital models of buildings are widely used in civil engineering. In these models, geometric information is used as leading information. Engineers are used to have geometric information, and, for instance, it is state of the art to specify a point by its three coordinates. However, the traditional approaches have disadvantages. Geometric information is over-determined. Thus, more geometric information is specified and stored than needed. In addition, engineers already deal with topological information. A denotation of objects in buildings is of topological nature. It has to be answered whether approaches where topological information becomes a leading role would be more efficient in civil engineering. This paper presents such an approach. Topological information is modelled independently of geometric information. It is used for denoting the objects of a building. Geometric information is associated to topological information so that geometric information “weights” a topology.
The concept presented in this paper has already been used in surveying existing buildings. Experiences in the use of this concept showed that the number of geometric information that is required for a complete specification of a building could be reduced by a factor up to 100. Further research will show how this concept can be used in planning processes.
TOOL TO CHECK TOPOLOGY AND GEOMETRY FOR SPATIAL STRUCTURES ON BASIS OF THE EXTENDED MAXWELL'S RULE
(2006)
One of the simplest principle in the design of light-weight structures is to avoid bending. This can be achieved by dissolving girders into members acting purely in axial tension or compression. The employment of cables for the tensioned members leads to even lighter structures which are called cable-strut structures. They constitute a subclass of spatial structures. To give fast information about the general feasibility of an architectural concept employing cable-strut structures is a challenging task due to their sophisticated mechanical behavior. In this regard it is essential to control if the structure is stable and if pre-stress can be applied. This paper presents a tool using the spreadsheet software Microsoft (MS) Excel which can give such information. Therefore it is not necessary to purchase special software and the according time consuming training is much lower. The tool was developed on basis of the extended Maxwell's rule, which besides topology also considers the geometry of the structure. For this the rank of the node equilibrium matrix is crucial. Significance and determination of the rank and the implementation of the corresponding algorithms in MS Excel are described in the following. The presented tool is able to support the structural designer in an early stage of the project in finding a feasible architectural concept for cable-strut structures. As examples for the application of the software tool two special cable-strut structures, so called tensegrity structures, were examined for their mechanical behavior.
Design activity could be treated as state transition computationally. In stepwise processing, in-between form-states are not easily observed. However, in this research time-based concept is introduced and applied in order to bridge the gap. In architecture, folding is one method of form manipulation and architects also want to search for alternatives by this operation. Besides, folding operation has to be defined and parameterized before time factor is involved as a variable of folding. As a result, time-based transformation provides sequential form states and redirects design activity.
The concrete is modeled as a material with damage and plasticity, whereat the viscoplastic and the viscoelastic behaviour depends on the rate of the total strains. Due to the damage behaviour the compliance tensor develops different properties in tension and compression. There have been tested various yield surfaces and flow rules, damage rules respectively to their usability in a concrete model. One three-dimensional yield surface was developed from a failure surface based on the Willam--Warnke five-parameter model by the author. Only one general uni-axial stress-strain-relation is used for the numeric control of the yield surface. From that curve all necessary parameters for different strengths of concrete and different strain rates can be derived by affine transformations. For the flow rule in the compression zone a non associated inelastic potential is used, in the tension zone a Rankine potential. Conditional on the time-dependent formulation, the symmetry of the system equations is maintained in spite of the usage of non-associated potentials for the derivation of the inelastic strains. In case of quasi statical computations a simple viscoplastic law is used that is rested on an approach to Perzyna. The principle of equality of dissipation power in the uni-axial and the three-axial state of stress is used. It is modified by a factor that depends on the actual stress ratio and in comparison with the Kupfer experiments it implicates strains that are more realistic. The implementation of the concrete model is conducted in a mixed hybrid finite element. Examples in the structural level are introduced for verification of the concrete model.
For assessment of old buildings, thermal graphic analysis aided with infra-red camera have been employed in a wide range nowadays. Image processing and evaluation can be economically practicable only if the image evaluation can also be automated to the largest extend. For that reason methods of computer vision are presented in this paper to evaluate thermal images. To detect typical thermal image elements, such as thermal bridges and lintels in thermal images respectively gray value images, methods of digital image processing have been applied, of which numerical procedures are available to transform, modify and encode images. At the same time, image processing can be regarded as a multi-stage process. In order to be able to accomplish the process of image analysis from image formation through perfecting and segmentation to categorization, appropriate functions must be implemented. For this purpose, different measuring procedures and methods for automated detection and evaluation have been tested.
The Lucas-Kanade tracker has proven to be an efficient and accurate method for calculation of the optical flow. However, this algorithm can reliably track only suitable image features like corners and edges. Therefore, the optical flow can only be calculated for a few points in each image, resulting in sparse optical flow fields. Accumulation of these vectors over time is a suitable method to retrieve a dense motion vector field. However, the accumulation process limits application of the proposed method to fixed camera setups. Here, a histogram based approach is favored to allow more than a single typical flow vector per pixel. The resulting vector field can be used to detect roads and prescribed driving directions which constrain object movements. The motion structure can be modeled as a graph. The nodes represent entry and exit points for road users as well as crossings, while the edges represent typical paths.
The main hypothesis of this research is that civil society’s participation is able to improve the planning results in the Chinese city of Qingdao in the contemporary age. Qingdao is a young city developed from a German colony in eastern China. Apart from the powers of the government and the market, the 'third power', including mainly the power of volunteer citizens and the citizens’ organisations, also positively promoted the spatial development in Qingdao’s history. Since 1978’s reform, Qingdao’s great progress in urban housing, historic preservation, public space and urban traffic results mainly from the increasing strength of both the government and the market, while the government has always been the dominant promoter for urban construction. The actual planning mechanism – the government formulates 'what to do' itself and decides 'how to do it' with the market – has much limit in reacting to the rapidly changing situation, serving diversified social interests, and raising sufficient funds for the city’s urgent demands in Qingdao. Searching for new development strategies based on the understanding of civil society in the Chinese context can provide a promising perspective on the urban studies of Qingdao. Chinese civil society can be understood as the intermediate sphere of individuals, families, citizen’s organisations, social movements, public communication, and of the non-governmental body’s non-for-profit involvement for the provision of public services between the state and the market. China has its own cultural tradition of civil society, and the modern civil society in China is showing its great potential in improving social integration and urban life. The Chinese government has started to advocate for civil society’s participation in urban construction, and encouraging the 'bottom-up' mechanism in the planning-related issues through political statements and legislative approaches since the last two decades. The existing planning practice in China is able to demonstrate that civil society’s participation helps improve the quality of Chinese urban planning realistically under present conditions, and that moderation of planning experts and the push of the authority are the key factors for successfully integrating the strength of civil society in planning. However, the power of civil society is not yet sufficiently discovered in Qingdao’s planning. For better planning results, the city of Qingdao needs more initiatives to mobilize civil society in the planning practice, as well as more support to enrich the related studies. This thesis recommends that Qingdao establishes the 'Foundation for Collaborative Urban Solutions' through the joint efforts of the authority and civil initiatives, which aims at moderating and facilitating the strength of civil society. The suggested pilot projects include: a. The Community-based Housing Workshop for regenerating the living environment of the run-down communities, where the residents are willing to collaborate with the foundation with own efforts. b. The Heritage Preservation Workshop for suggesting an efficient supervision mechanism involving civil society which protects the historic heritage from being destroyed in the urban construction. c. The Public Space Forum for improving accessibility, quantity and ecologic function in the development of Qingdao’s urban public space with the knowledge and creativity of both the government and the citizens. d. The Mass Transport Forum for a realistic strategy for funding the rail-based traffic system in Qingdao through enabling the civil society - especially the individual citizens and their households to invest. The 'Foundation of Collaborative Urban Solutions' is able to improve Qingdao’s planning to cope with the urban problems the city are facing in its contemporary development, as well as to provide valuable reference for the further research of civil society’s participation in Chinese urban planning.
Due to the amount of flow simulation and measurement data, automatic detection, classification and visualization of features is necessary for an inspection. Therefore, many automated feature detection methods have been developed in recent years. However, only one feature class is visualized afterwards in most cases, and many algorithms have problems in the presence of noise or superposition effects. In contrast, image processing and computer vision have robust methods for feature extraction and computation of derivatives of scalar fields. Furthermore, interpolation and other filter can be analyzed in detail. An application of these methods to vector fields would provide a solid theoretical basis for feature extraction. The authors suggest Clifford algebra as a mathematical framework for this task. Clifford algebra provides a unified notation for scalars and vectors as well as a multiplication of all basis elements. The Clifford product of two vectors provides the complete geometric information of the relative positions of these vectors. Integration of this product results in Clifford correlation and convolution which can be used for template matching of vector fields. For frequency analysis of vector fields and the behavior of vector-valued filters, a Clifford Fourier transform has been derived for 2D and 3D. Convolution and other theorems have been proved, and fast algorithms for the computation of the Clifford Fourier transform exist. Therefore the computation of Clifford convolution can be accelerated by computing it in Clifford Fourier domain. Clifford convolution and Fourier transform can be used for a thorough analysis and subsequent visualization of flow fields.
Die Instandhaltung der städtischen Trinkwassernetze ist Aufgabenschwerpunkt der Wasserversorgungsunternehmen bzw. Netzbetreiber. Dazu notwendige Rehabilitationsplanungen stützen sich zurzeit weitgehend auf die Trendprognose von Schadensraten und die Erfahrungen der Mitarbeiter. Der Einfluss wesentlicher Kenngrößen wie Werkstoffeigenschaften oder die Resttragfähigkeit des Rohres bleiben hierbei größtenteils unberücksichtigt. Über materialtechnische Untersuchungen werden die notwendigen Kenngrößen ermittelt, die eine zuverlässige Bewertung des technischen Zustands des Rohrstrangs ermöglichen. So lassen sich die Prognose der technischen Nutzungsdauer und Rehabilitationsplanungen auf eine solide Basis stellen. In dieser Dissertationsschrift wird hierzu ein Untersuchungs- und Bewertungsalgorithmus mit integrierten Prognoseverfahren erarbeitet.
Die Fachtagung richtete sich an Geschäftsführer, Projektleiter, Bauleiter und Projektsteuerer in Planung und Ausführung mit Beiträgen zum Nachtrags- und Änderungsmanagement am Bau, Workflow-Management in der Baupraxis, Integration von Informationsprozessen auf der Basis von Nemetschek Technologien sowie Kompetenzaufbau durch gezielte Weiterbildung.
This contribution will be freewheeling in the domain of signal, image and surface processing and touch briefly upon some topics that have been close to the heart of people in our research group. A lot of the research of the last 20 years in this domain that has been carried out world wide is dealing with multiresolution. Multiresolution allows to represent a function (in the broadest sense) at different levels of detail. This was not only applied in signals and images but also when solving all kinds of complex numerical problems. Since wavelets came into play in the 1980's, this idea was applied and generalized by many researchers. Therefore we use this as the central idea throughout this text. Wavelets, subdivision and hierarchical bases are the appropriate tools to obtain these multiresolution effects. We shall introduce some of the concepts in a rather informal way and show that the same concepts will work in one, two and three dimensions. The applications in the three cases are however quite different, and thus one wants to achieve very different goals when dealing with signals, images or surfaces. Because completeness in our treatment is impossible, we have chosen to describe two case studies after introducing some concepts in signal processing. These case studies are still the subject of current research. The first one attempts to solve a problem in image processing: how to approximate an edge in an image efficiently by subdivision. The method is based on normal offsets. The second case is the use of Powell-Sabin splines to give a smooth multiresolution representation of a surface. In this context we also illustrate the general method of construction of a spline wavelet basis using a lifting scheme.
Strategic Developments
(2006)