@phdthesis{Chan, author = {Chan, Chiu Ling}, title = {Smooth representation of thin shells and volume structures for isogeometric analysis}, doi = {10.25643/bauhaus-universitaet.4208}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200812-42083}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {162}, abstract = {The purpose of this study is to develop self-contained methods for obtaining smooth meshes which are compatible with isogeometric analysis (IGA). The study contains three main parts. We start by developing a better understanding of shapes and splines through the study of an image-related problem. Then we proceed towards obtaining smooth volumetric meshes of the given voxel-based images. Finally, we treat the smoothness issue on the multi-patch domains with C1 coupling. Following are the highlights of each part. First, we present a B-spline convolution method for boundary representation of voxel-based images. We adopt the filtering technique to compute the B-spline coefficients and gradients of the images effectively. We then implement the B-spline convolution for developing a non-rigid images registration method. The proposed method is in some sense of "isoparametric", for which all the computation is done within the B-splines framework. Particularly, updating the images by using B-spline composition promote smooth transformation map between the images. We show the possible medical applications of our method by applying it for registration of brain images. Secondly, we develop a self-contained volumetric parametrization method based on the B-splines boundary representation. We aim to convert a given voxel-based data to a matching C1 representation with hierarchical cubic splines. The concept of the osculating circle is employed to enhance the geometric approximation, where it is done by a single template and linear transformations (scaling, translations, and rotations) without the need for solving an optimization problem. Moreover, we use the Laplacian smoothing and refinement techniques to avoid irregular meshes and to improve mesh quality. We show with several examples that the method is capable of handling complex 2D and 3D configurations. In particular, we parametrize the 3D Stanford bunny which contains irregular shapes and voids. Finally, we propose the B´ezier ordinates approach and splines approach for C1 coupling. In the first approach, the new basis functions are defined in terms of the B´ezier Bernstein polynomials. For the second approach, the new basis is defined as a linear combination of C0 basis functions. The methods are not limited to planar or bilinear mappings. They allow the modeling of solutions to fourth order partial differential equations (PDEs) on complex geometric domains, provided that the given patches are G1 continuous. Both methods have their advantages. In particular, the B´ezier approach offer more degree of freedoms, while the spline approach is more computationally efficient. In addition, we proposed partial degree elevation to overcome the C1-locking issue caused by the over constraining of the solution space. We demonstrate the potential of the resulting C1 basis functions for application in IGA which involve fourth order PDEs such as those appearing in Kirchhoff-Love shell models, Cahn-Hilliard phase field application, and biharmonic problems.}, subject = {Modellierung}, language = {en} } @phdthesis{Goebel, author = {G{\"o}bel, Luise}, title = {Experimental and semi-analytical multiscale approaches for the characterization of the elastic and viscoelastic behavior of polymer-modified cement-based materials}, publisher = {Bauhaus-Universit{\"a}tsverlag}, address = {Weimar}, isbn = {978-3-95773-269-9}, doi = {10.25643/bauhaus-universitaet.3827}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181211-38279}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {259}, abstract = {Polymer-modified cement concrete (PCC) is a heterogeneous building material with a hierarchically organized microstructure. Therefore, continuum micromechanics-based multiscale models represent a promising method to estimate the mechanical properties. By means of a bottom-up approach, homogenized properties at the macroscopic scale are derived considering microstructural characteristics. The extension of existing multiscale models for the application to PCC is the main objective of this work. For that, cross-scale experimental studies are required. Both macroscopic and microscopic mechanical tests are performed to characterize the elastic and viscoelastic properties of different PCC. The comparison between experiment and model prediction illustrates the success of the modeling approach.}, subject = {Elastizit{\"a}tsmodul}, language = {en} } @misc{Rahm2011, type = {Master Thesis}, author = {Rahm, Tobias}, title = {Simulation von Kernprozessen eines Erddruckschildes}, doi = {10.25643/bauhaus-universitaet.1461}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20110909-15599}, school = {Bauhaus-Universit{\"a}t Weimar}, year = {2011}, abstract = {In dieser Arbeit wird der Vortriebsprozess einer Erddruckschildmaschine in einem Simulationsmodell mit Hilfe der System Dynamics modelliert. Nach einer Einf{\"u}hrung in den maschinellen Tunnelbau werden die Besonderheiten der Erddruckschildmaschine herausgestellt. Anschließend wird das betrachtete System mit dem Simulationskonzept der System Dynamics modelliert und in einem geeigneten Simulationstool implementiert.}, subject = {Simulation}, language = {de} } @phdthesis{Semar2010, author = {Semar, Olivier}, title = {Anwendung der Perkolationstheorie zur Analyse des suffosiven Partikeltransportes}, doi = {10.25643/bauhaus-universitaet.1438}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20101124-15252}, school = {Bauhaus-Universit{\"a}t Weimar}, year = {2010}, abstract = {Die vorliegende Arbeit besch{\"a}ftigt sich mit der geometrischen Suffosionsbest{\"a}ndigkeit von Erdstoffen. Mit dem wahrscheinlichkeitstheoretischen Ansatz der Perkolationstheorie wurde ein analytisches Verfahren gew{\"a}hlt, mit dem suffosive Materialtransportprozesse modelliert und quantifiziert werden k{\"o}nnen. Mit dem verwendeten Perkolationsmodell wurde eine beliebige Porenstruktur eines realen Erdstoffes im 3-Dimensionalen modelliert. M{\"o}gliche Materialtransportprozesse innerhalb der modellierten Porenstruktur wurden anschließend simuliert. Allgemein g{\"u}ltige Gesetzm{\"a}ßigkeiten wurden hergeleitet und Grenzbedingungen formuliert. Diese sind vom Erdstoff unabh{\"a}ngig und beschreiben Zusammenh{\"a}nge zwischen Materialtransport und Porenstruktur. Anwendbar sind diese Ergebnisse auf homogene, isotrope und selbst{\"a}hnliche Erdstoffgef{\"u}ge. Aussagen {\"u}ber konkrete Erdstoffe k{\"o}nnen {\"u}ber die Transformationsmethode erfolgen. F{\"u}r die Verwendung der Transformationsmethode ist vorab die relevante Porenstruktur, d. h. die Porenengstellenverteilung, zu ermitteln.}, subject = {Perkolationstheorie}, language = {de} } @phdthesis{Bubner2006, author = {Bubner, Andr{\´e}}, title = {Datenmodelle zur Bearbeitung von Ingenieuraufgaben am Beispiel von Wohnh{\"a}usern in Stahlbauweise}, doi = {10.25643/bauhaus-universitaet.808}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20070423-8580}, school = {Bauhaus-Universit{\"a}t Weimar}, year = {2006}, abstract = {Modelle bilden die Grundlage der Planung. Sie repr{\"a}sentieren die zur Bearbeitung erforderlichen Eigenschaften eines Bauwerks in einer an die spezifische Aufgabe angepassten Form. Zwischen den verschiedenen zur Abbildung des Bauwerks eingesetzten Modellen bestehen fachliche Zusammenh{\"a}nge bez{\"u}glich der darin abgebildeten Aspekte. Diese Abh{\"a}ngigkeiten werden in der praktischen Planungsbearbeitung gegenw{\"a}rtig auf Grundlage von Erfahrungswerten, normativen Vorgaben und vereinfachenden Annahmen ber{\"u}cksichtigt. Die detailliertere Modellierung von Bauwerkseigenschaften f{\"u}hrt zu einer engeren Verzahnung der verschiedenen Modelle. Um eine fachliche Inselbildung zu vermeiden, ist eine entsprechend angepasste Abbildung der zwischen den einzelnen Modellen bestehenden Beziehungen erforderlich. Mit den steigenden Anspr{\"u}chen an eine Bearbeitung von Ingenieuraufgaben gewinnt eine {\"u}ber den Zweck der Bereitstellung ausgew{\"a}hlter Informationen zum Bauwerk und der Unterst{\"u}tzung eines Datenaustauschs zwischen verschiedenen Fachplanern hinausgehende datentechnische Abbildung an Bedeutung. Dies setzt eine Diskussion der Anforderungen an eine solche Beschreibung aus fachlicher Sicht voraus. Die Untersuchung der fachlichen Anforderungen wird am Beispiel von Wohnh{\"a}usern in Stahlbauweise gef{\"u}hrt.}, subject = {Modellierung}, language = {de} } @phdthesis{Haefner2006, author = {H{\"a}fner, Stefan}, title = {Grid-based procedures for the mechanical analysis of heterogeneous solids}, doi = {10.25643/bauhaus-universitaet.858}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20070830-9185}, school = {Bauhaus-Universit{\"a}t Weimar}, year = {2006}, abstract = {The importance of modern simulation methods in the mechanical analysis of heterogeneous solids is presented in detail. Thereby the problem is noted that even for small bodies the required high-resolution analysis reaches the limits of today's computational power, in terms of memory demand as well as acceptable computational effort. A further problem is that frequently the accuracy of geometrical modelling of heterogeneous bodies is inadequate. The present work introduces a systematic combination and adaption of grid-based methods for achieving an essentially higher resolution in the numerical analysis of heterogeneous solids. Grid-based methods are as well primely suited for developing efficient and numerically stable algorithms for flexible geometrical modeling. A key aspect is the uniform data management for a grid, which can be utilized to reduce the effort and complexity of almost all concerned methods. A new finite element program, called Mulgrido, was just developed to realize this concept consistently and to test the proposed methods. Several disadvantages which generally result from grid discretizations are selectively corrected by modified methods. The present work is structured into a geometrical model, a mechanical model and a numerical model. The geometrical model includes digital image-based modeling and in particular several methods for the theory-based generation of inclusion-matrix models. Essential contributions refer to variable shape, size distribution, separation checks and placement procedures of inclusions. The mechanical model prepares the fundamentals of continuum mechanics, homogenization and damage modeling for the following numerical methods. The first topic of the numerical model introduces to a special version of B-spline finite elements. These finite elements are entirely variable in the order k of B-splines. For homogeneous bodies this means that the approximation quality can arbitrarily be scaled. In addition, the multiphase finite element concept in combination with transition zones along material interfaces yields a valuable solution for heterogeneous bodies. As the formulation is element-based, the storage of a global stiffness matrix is superseded such that the memory demand can essentially be reduced. This is possible in combination with iterative solver methods which represent the second topic of the numerical model. Here, the focus lies on multigrid methods where the number of required operations to solve a linear equation system only increases linearly with problem size. Moreover, for badly conditioned problems quite an essential improvement is achieved by preconditioning. The third part of the numerical model discusses certain aspects of damage simulation which are closely related to the proposed grid discretization. The strong efficiency of the linear analysis can be maintained for damage simulation. This is achieved by a damage-controlled sequentially linear iteration scheme. Finally a study on the effective material behavior of heterogeneous bodies is presented. Especially the influence of inclusion shapes is examined. By means of altogether more than one hundred thousand random geometrical arrangements, the effective material behavior is statistically analyzed and assessed.}, subject = {B-Spline}, language = {en} } @inproceedings{HauschildBorrmannHuebler2004, author = {Hauschild, Thomas and Borrmann, Andr{\´e} and H{\"u}bler, Reinhard}, title = {Integration of Constraints into Digital Building Models for Cooperative Planning Processes}, doi = {10.25643/bauhaus-universitaet.177}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-1775}, year = {2004}, abstract = {The uniqueness and the long life cycle of buildings imply a dynamically modifiable building model. The technological foundation for the management of digital building models, a dynamic model management system (MMS), developed by our research group, allows to explicitly access and to modify the object model of the stored planning data. In this paper, the integration of constraints in digital building models will be shown. Constraints are conditions, which apply to the instances of domain model classes, and are defined by the user at runtime of the information system. For the expression of constraints, the Constraint Modelling Language (CML) has been developed and will be described in this paper. CML is a powerful, intuitively usable object-oriented language, which allows the expression of constraints at a high semantic level. A constrained-enabled MMS can verify, whether an instance fulfils the applying constraints. To ensure flexibility, the evaluation of constraints is not implicitly performed by the systems, but explicitly initiated by the user. A classification of constraint types and example usage scenarios are given.}, subject = {Architektur}, language = {en} } @inproceedings{vanRooyenOlivier2004, author = {van Rooyen, G.C. and Olivier, A. H.}, title = {Notes on structural analysis in a distributed collaboratory}, doi = {10.25643/bauhaus-universitaet.145}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-1451}, year = {2004}, abstract = {The worldwide growth of communication networks and associated technologies provide the basic infrastructure for new ways of executing the engineering process. Collaboration amongst team members seperated in time and location is of particular importance. Two broad themes can be recognized in research pertaining to distributed collaboration. One theme focusses on the technical and technological aspects of distributed work, while the other emphasises human aspects thereof. The case of finite element structural analysis in a distributed collaboratory is examined in this paper. An approach is taken which has its roots in human aspects of the structural analysis task. Based on experience of how structural engineers currently approach and execute this task while utilising standard software designed for use on local workstations only, criteria are stated for a software architechture that could support collaborative structural analysis. Aspects of a pilot application and the results of qualitative performance measurements are discussed.}, subject = {Ingenieurbau}, language = {en} } @inproceedings{MilesJoitaBurnap2004, author = {Miles, John and Joita, Liviu and Burnap, Peter}, title = {Collaborative Engineering: Virtual Teams in a Grid Environment Supporting Consortia in the Construction Industry}, doi = {10.25643/bauhaus-universitaet.136}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-1362}, year = {2004}, abstract = {In the AEC (Architecture / Engineering / Construction) industry a number of individuals and organisations collaborate and work jointly on a construction project. The resulting consortium has large pool of expertise and experience and can be defined as a Virtual Organisation (VO) formed for the duration of the project. VOs are electronically networked organisations where IT and web based communication technology play an important role in coordinating various activities of these organisations. This paper describes the design, development and implementation of a Grid enabled application called the Product Supplier Catalogue Database (PSCD) which supports collaborative working in consortia. As part of the Grid-enabling process, specialised metadata is being developed to enable PSCD to effectively utilise Grid middleware such as Globus and Java CoG toolkits. We also describe our experience whilst designing, developing and deploying the security service of the application using the Globus Security Interface (GSI).}, subject = {Ingenieurbau}, language = {en} } @inproceedings{Olivier2004, author = {Olivier, A. H.}, title = {An application-centred framework for distributed engineering applications}, doi = {10.25643/bauhaus-universitaet.135}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-1353}, year = {2004}, abstract = {The conceptual structure of an application that can support the structural analysis task in a distributed collaboratory is described in (van Rooyen and Olivier 2004). The application described there has a standalone component for executing the finite element method on a local workstation in the absence of network access. This application is comparable to current, local workstation based finite element packages. However, it differs fundamentally from standard packages since the application itself, and its objects, are adapted to support distributed execution of the analysis task. Basic aspects of an object-oriented framework for the development of applications which can be used in similar distributed collaboratories are described in this paper. An important feature of this framework is its application-centred design. This means that an application can contain any number of engineering models, where the models are formed by the collection of objects according to semantic views within the application. This is achieved through very flexible classes Application and Model, which are described in detail. The advantages of the application-centred design approach is demonstrated with reference to the design of steel structures, where the finite element analysis model, member design model and connection design model interact to provide the required functionality.}, subject = {Ingenieurbau}, language = {en} }