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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.
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.
In dieser Arbeit wird der Vortriebsprozess einer Erddruckschildmaschine in einem Simulationsmodell mit Hilfe der System Dynamics modelliert. Nach einer Einführung 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.
Die vorliegende Arbeit beschäftigt sich mit der geometrischen Suffosionsbeständigkeit von Erdstoffen. Mit dem wahrscheinlichkeitstheoretischen Ansatz der Perkolationstheorie wurde ein analytisches Verfahren gewählt, mit dem suffosive Materialtransportprozesse modelliert und quantifiziert werden können. Mit dem verwendeten Perkolationsmodell wurde eine beliebige Porenstruktur eines realen Erdstoffes im 3-Dimensionalen modelliert. Mögliche Materialtransportprozesse innerhalb der modellierten Porenstruktur wurden anschließend simuliert. Allgemein gültige Gesetzmäßigkeiten wurden hergeleitet und Grenzbedingungen formuliert. Diese sind vom Erdstoff unabhängig und beschreiben Zusammenhänge zwischen Materialtransport und Porenstruktur. Anwendbar sind diese Ergebnisse auf homogene, isotrope und selbstähnliche Erdstoffgefüge. Aussagen über konkrete Erdstoffe können über die Transformationsmethode erfolgen. Für die Verwendung der Transformationsmethode ist vorab die relevante Porenstruktur, d. h. die Porenengstellenverteilung, zu ermitteln.
Datenmodelle zur Bearbeitung von Ingenieuraufgaben am Beispiel von Wohnhäusern in Stahlbauweise
(2006)
Modelle bilden die Grundlage der Planung. Sie repräsentieren 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 Zusammenhänge bezüglich der darin abgebildeten Aspekte. Diese Abhängigkeiten werden in der praktischen Planungsbearbeitung gegenwärtig auf Grundlage von Erfahrungswerten, normativen Vorgaben und vereinfachenden Annahmen berücksichtigt. Die detailliertere Modellierung von Bauwerkseigenschaften führt 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 Ansprüchen an eine Bearbeitung von Ingenieuraufgaben gewinnt eine über den Zweck der Bereitstellung ausgewählter Informationen zum Bauwerk und der Unterstützung 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 Wohnhäusern in Stahlbauweise geführt.
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.
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.
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.
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).
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.
Re-examination of the behaviour of structures can be necessary due to deterioration or changes in the traffic situation during their lifetime. The Finite Element Method (FEM) is widely used in order to accomplish numerical analysis. Considering the development of computer performance, more detailed FEM models can be analyzed, even on site, with mobile computers. To compensate the increasing amount of data needed for the model input, measures need to be taken to save time, by distributing the work. In order to provide consistency to the model, fedback data must be checked upon reception. A local wireless computer network of ultra-portable devices linked together with a computer can provide the coordination necessary for efficient parallel working. Based on a digital model consisting of all data gathered, structural modelling and numerical analysis are performed automatically. Thus, the user is released from the work that can be automatized and the time needed for the overall analysis of a structure is decreased.
In current AEC practice client requirements are typically recorded in a building program, which, depending on the building type, covers various aspects from the overall goals, activities and spatial needs to very detailed material and condition requirements. This documentation is used as the starting point of the design process, but as the design progresses, it is usually left aside and changes are made incrementally based on the previous design solution. These incremental small changes can lead to a solution that may no longer meet the original requirements. In addition, design is by nature an iterative process and the proposed solutions often also cause evolution in the client requirements. However, the requirements documentation is usually not updated accordingly. Finding the latest updates and evolution of the requirements from the documentation is very difficult, if not impossible. This process can lead to an end result, which is significantly different from the documented requirements. Some important requirements may not be satisfied, and even if the design process was based on agreed-upon changes in the scope and requirements, differences in the requirements documents and in the completed building can lead to well-justified doubts about the quality of the design and construction process...
This paper describes an ongoing research on the representation and reasoning about construction specifications, which is part of a bigger research project that aims at developing a formalism for automating the identification of deviations and defects on construction sites. We specifically describe the requirements on product and process models and an approach for representing and reasoning about construction specifications to enable automated detection and assessment of construction deviations and defects. This research builds on the previous research on modeling design specifications and extends and elaborates concept of contexts developed in that domain. The paper provides an overview of how the construction specifications are being modele d in this research and points out future steps that need to be accomplished to develop the envisioned automated deviation and defect detection system.
Although there are some good reasons to design engineering software as a stand-alone application for a single computer, there are also numerous possibilities for creating distributed engineering applications, in particular using the Internet. This paper presents some typical scenarios how engineering applications can benefit from including network capabilities. Also, some examples of Internet-based engineering applications are discussed to show how the concepts presented can be implemented.
Collaboration in AEC Design : Web-enabling Applications using Peer-to-Peer Office Communicator
(2004)
A market analysis conducted by Gartner Dataquest in August 2001 has shown the typical characteristics of the AEC design process. High volatility in membership of AEC design groups and members dispersed over several external offices is the common collaboration scenario. Membership is most times short lived, compared to the overall duration of the process. A technical solution has to take that into account by making joining and leaving a collaborative work group very easy. The modelling of roles of collaboration between group members must be based on a commonly understood principle like the publisher / subscriber model, where the individual that is responsible for the distribution of vital information is clear. Security issues and trust in the confidentiality of the system is a central concern for the acceptance of the system. Therefore, keeping the subset of data that will be published under the absolute control of the publisher is a must. This is not the case with server-based scenarios, sometimes even due to psychological reasons. A loosely bound Peer-to-Peer network offers advantages over a server-based solution, because of less administrative overhead and simple installation procedures. In a peer-to-peer environment, a publish/subscribe role model can be more easily implemented. The publish/subscribe model matches the way AEC processes are modelled in real world scenarios today, where legal proof of information exchange between external offices is of high importance. Workflow management systems for small to midsize companies of the AEC industry may adopt the peer-to-peer approach to collaboration in the future. Further investigations are being made on the research level (WINDS) by integrating the viewer and redlining application Collaborate! into a collaborative environment.
Current building product models explicitly represent components, attributes of components, and relationships between components. These designer-focused product models, however, do not represent many of the design conditions that are important for construction, such as component similarity, uniformity, and penetrations. Current design and construction tools offer limited support for detecting these construction-specific design conditions. This paper describes the ontology we developed using the manufacturing concept of features to represent the design conditions that are important for construction. The feature ontology provides the blueprint for the additions and changes needed to transform a standard product model into a constructionspecific product model. The ontology formalizes three classes of features, defines the attributes and functions of each feature type, and represents the relationships between features explicitly. The descriptive semantics of the ontology allows practitioners to represent their varied preferences for naming features, specifying features that result from component intersections and the similarity of components, and grouping features that affect a specific construction domain. A software prototype that implements the ontology enables practitioners to transform designer-focused product models into feature-based product models that represent the construction perspective.
Structural engineering projects are increasingly organized in networked cooperations due to a permanently enlarged competition pressure and a high degree of complexity while performing the concurrent design activities. Software that intends to support such collaborative structural design processes implicates enormous requirements. In the course of our common research work, we analyzed the pros and cons of the application of both the peer-to-peer (University of Bonn) and multiagent architecture style (University of Bochum) within the field of collaborative structural design. In this paper, we join the benefits of both architecture styles in an integrated conceptual approach. We demonstrate the surplus value of the integrated multiagent–peer-to-peer approach by means of an example scenario in which several structural engineers are co-operatively designing the basic structural elements of an arched bridge, applying heterogeneous CAD systems.
The scientific transfer of key technology features to developing countries, together with adequate competence, localisation and adaptation, is the primary purpose of the proposed investigation. It is evident that introducing high-level CAD design and detailing will improve the planning process in developing countries. Successful utilization of applied information technology for the planning process, however, depends on the user-interface of individual software. Therefore, to open the great opportunity embedded in CAD software for clients globally, the language and character-set barrier of traditional user-interfaces must be overcome. A proposal for a research program is given here to address such issue in favour of global civil engineering.
Assuring global consistency in a cooperative working environment is the main focus of many nowaday research projects in the field of civil engineering and others. In this paper, a new approach based on octrees will be discussed. It will be shown that by the usage of octrees not only the management and control of processes in a network-based working environment can be optimised but also an efficient integration platform for processes from various disciplines – such as architecture and civil engineering – can be provided. By means of an octree-based collision detection resp. consistency assurance a client-server-architecture will be described as well as sophisticated information services for a further support of cooperative work.