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Polylactic acid (PLA) is a highly applicable material that is used in 3D printers due to some significant features such as its deformation property and affordable cost. For improvement of the end-use quality, it is of significant importance to enhance the quality of fused filament fabrication (FFF)-printed objects in PLA. The purpose of this investigation was to boost toughness and to reduce the production cost of the FFF-printed tensile test samples with the desired part thickness. To remove the need for numerous and idle printing samples, the response surface method (RSM) was used. Statistical analysis was performed to deal with this concern by considering extruder temperature (ET), infill percentage (IP), and layer thickness (LT) as controlled factors. The artificial intelligence method of artificial neural network (ANN) and ANN-genetic algorithm (ANN-GA) were further developed to estimate the toughness, part thickness, and production-cost-dependent variables. Results were evaluated by correlation coefficient and RMSE values. According to the modeling results, ANN-GA as a hybrid machine learning (ML) technique could enhance the accuracy of modeling by about 7.5, 11.5, and 4.5% for toughness, part thickness, and production cost, respectively, in comparison with those for the single ANN method. On the other hand, the optimization results confirm that the optimized specimen is cost-effective and able to comparatively undergo deformation, which enables the usability of printed PLA objects.
Burning of clinker is the most influencing step of cement quality during the production process. Appropriate characterisation for quality control and decision-making is therefore the critical point to maintain a stable production but also for the development of alternative cements. Scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDX) delivers spatially resolved phase and chemical information for cement clinker. This data can be used to quantify phase fractions and chemical composition of identified phases.
The contribution aims to provide an overview of phase fraction quantification by semi-automatic phase segmentation using high-resolution backscattered electron (BSE) images and lower-resolved EDX element maps. Therefore, a tool for image analysis was developed that uses state-of-the-art algorithms for pixel-wise image segmentation and labelling in combination with a decision tree that allows searching for specific clinker phases. Results show that this tool can be applied to segment sub-micron scale clinker phases and to get a quantification of all phase fractions. In addition, statistical evaluation of the data is implemented within the tool to reveal whether the imaged area is representative for all clinker phases.
This study demonstrates the application and combination of multiple imaging techniques [light microscopy, micro-X-ray computer tomography (μ-CT), scanning electron microscopy (SEM) and focussed ion beam – nano-tomography (FIB-nT)] to the analysis of the microstructure of hydrated alite across multiple scales. However, by comparing findings with mercury intrusion porosimetry (MIP), it becomes obvious that the imaged 3D volumes and 2D images do not sufficiently overlap at certain scales to allow a continuous quantification of the pore size distribution (PSD). This can be overcome by improving the resolution and increasing the measured volume. Furthermore, results show that the fibrous morphology of calcium-silicate-hydrates (C-S-H) phases is preserved during FIB-nT. This is a requirement for characterisation of nano-scale porosity. Finally, it was proven that the combination of FIB-nT with energy-dispersive X-ray spectroscopy (EDX) data facilitates the phase segmentation of a 11 × 11 × 7.7 μm3 volume of hydrated alite.
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.
Realistic uncertainty description incorporating aleatoric and epistemic uncertainties can be described within the framework of polymorphic uncertainty, which is computationally demanding. Utilizing a domain decomposition approach for random field based uncertainty models the proposed level-based sampling method can reduce these computational costs significantly and shows good agreement with a standard sampling technique. While 2-level configurations tend to get unstable with decreasing sampling density 3-level setups show encouraging results for the investigated reliability analysis of a structural unit square.
Bauhaus-Gastprofessorin Mirjam Wenzel referierte am 30. Juni 2021 im Audimax der Bauhaus-Universität Weimar zur Entstehungsgeschichte und Konzeption Jüdischer Museen. Dabei ging sie darauf ein, inwiefern diese Museen besonders relevant für aktuelle gesellschaftliche und politische Fragestellungen sind. Prof. Wenzels zweiter öffentlicher Vortrag an der Bauhaus-Universität Weimar skizzierte die Potentiale von Kultureinrichtungen in Zeiten gesellschaftspolitischer Veränderungen im Allgemeinen und die Bedeutung Jüdischer Museen angesichts verbaler und tätlicher Gewalt gegen Jüdinnen und Juden im Besonderen.
Compiling and disseminating information about incidents and disasters are key to disaster management and relief. But due to inherent limitations of the acquisition process, the required information is often incomplete or missing altogether. To fill these gaps, citizen observations spread through social media are widely considered to be a promising source of relevant information, and many studies propose new methods to tap this resource. Yet, the overarching question of whether and under which circumstances social media can supply relevant information (both qualitatively and quantitatively) still remains unanswered. To shed some light on this question, we review 37 disaster and incident databases covering 27 incident types, compile a unified overview of the contained data and their collection processes, and identify the missing or incomplete information. The resulting data collection reveals six major use cases for social media analysis in incident data collection: (1) impact assessment and verification of model predictions, (2) narrative generation, (3) recruiting citizen volunteers, (4) supporting weakly institutionalized areas, (5) narrowing surveillance areas, and (6) reporting triggers for periodical surveillance. Furthermore, we discuss the benefits and shortcomings of using social media data for closing information gaps related to incidents and disasters.
Chemical glass frosting processes are widely used to create visual attractive glass surfaces. A commonly used frosting bath mainly contains ammonium bifluoride (NH4HF2) mixed with hydrochloric acid (HCl). The frosting process consists of several baths. Firstly, the preliminary bath to clean the object. Secondly, the frosting bath which etches the rough light scattering structure into the glass surface. Finally, the washing baths to clean the frosted object. This is where the constituents of the preceding steps accumulate and have to be filtered from the sewage. In the present contribution, phosphoric acid (H3PO4) was used as a substitute for HCl to reduce the amount of ammonium (NH4+) and chloride (Cl−) dissolved in the waste water. In combination with magnesium carbonate (MgCO3), it allows the precipitation of ammonium within the sewage as ammonium magnesium phosphate (MgNH4PO4). However, a trivial replacement of HCl by H3PO4 within the frosting process causes extensive frosting errors, such as inhomogeneous size distributions of the structures or domains that are not fully covered by these structures. By modifying the preliminary bath composition, it was possible to improve the frosting result considerably. To determine the optimal composition of the preliminary bath, a semi-automatic evaluation method has been developed. This method renders the objective comparison of the resulting surface quality possible.
Entrepreneurship and start-up activities are seen as a key response to recent upheavals in the media industry: Newly founded ventures can act as important drivers for industry transformation and renewal, pioneering new products, business models, and organizational designs (e.g. Achtenhagen, 2017; Buschow & Laugemann, 2020).
In principle, media students represent a crucial population of nascent entrepreneurs: individuals who will likely become founders of start-ups (Casero-Ripollés et al., 2016). However, their willingness to start a new business is generally considered to be rather low (Goyanes, 2015), and for journalism students, the idea of innovation tends to be conservative, following traditional norms and professional standards (Singer & Broersma, 2020). In a sample of Spanish journalism students, López-Meri et al. (2020) found that one of the main barriers to entrepreneurial intentions is that students feel they lack knowledge and training in entrepreneurship.
In the last 10 years, a wide variety of entrepreneurship education courses have been set up in media departments of colleges and universities worldwide.
These programs have been designed to sensitize and prepare communications, media and journalism students to think and act entrepreneurially (e.g. Caplan et al., 2020; Ferrier, 2013; Ferrier & Mays, 2017; Hunter & Nel, 2011). Entrepreneurial competencies
and practices not only play a crucial role for start-ups, but, in imes of digital transformation, are increasingly sought after by legacy media companies as well (Küng, 2015).
At the Department of Journalism and Communication Research, Hanover University of Music, Drama and Media, Germany, we have been addressing these developments with the “Media Entrepreneurship” program. The course, established in 2013, aims to provide fundamental knowledge of entrepreneurship, as well as promoting students‘ entrepreneurial thinking and behavior. This article presents the pedagogical approach of the program and investigates learning outcomes. By outlining and evaluating the Media Entrepreneurship program, this article aims to promote good practices of entrepreneurship education in communications, media and journalism, and to reflect on the limitations of such programs.
Utilizing Modern FIB/SEM Technology and EDS for 3D Imaging of Hydrated Alite and its Pore Space
(2021)
The exploration of cementitious materials using scanning electron microscopes (SEM) is mainly done using fractured or polished surfaces. This leads to high-resolution 2D-images that can be combined using EDX and EBSD to unveil details of the microstructure and composition of materials. Nevertheless, this does not provide a quantitative insight into the three-dimensional fine structure of for example C-S-H phases.
The focused ion beam (FIB) technology can cut a block of material in thin layers of less than 10 nm. This gives us a volume of 1000 μm³ with a voxel resolution of down to 4 x 4 x 10 nm³. The results can be combined with simultaneously acquired EDX data to improve image segmentation. Results of the investigation demonstrate that it is possible to obtain close-to-native 3D-visualisation of the spatial distribution of unreacted C3S, C-S-H and CH. Additionally, an optimized preparation method allows us to quantify the fine structure of C-S-H phases (length, aspect ratio, …) and the pore space.
Überwachungspraktiken und –technologien sind in der heutigen Welt omnipräsent und wohl nicht mehr wegzudenken. Ob CCTV-Systeme, Biometrie oder Data Mining – unsere Gesellschaft befindet sich in einem ständigen Überwachungsmodus, der sich weit über einen begrenzten Raum oder zeitlichen Rahmen hinausstreckt. Überwacht wird überall: privat, am Arbeitsplatz oder im Cyberspace, und alles: Interaktionen, Äußerungen, Verhalten. Es werden Unmengen von Daten gesammelt, strukturiert, kombiniert, gekauft und verkauft.
Dieser Modus stellt mehr als eine bloße Neuauflage des Bentham-Foucaultschen Panoptikons dar: der aktuelle Überwachungsmodus, die informationelle Asymmetrie als ihren tragenden Pfeiler beibehaltend, dient nicht nur der Disziplinierung, sondern viel mehr der Kontrolle, die nicht primär negativ-sanktionierend, sondern positiv-leistungssteigernd wirkt: es ist nicht das Ziel, die Individuen zu bestrafen und ein bestimmtes Verhalten zu verbieten, sondern sie durch Belohnung, Interaktion und spielerische Elemente dazu zu bringen, sich auf die gewünschte Art zu verhalten und im Endeffekt sich selbst zu überwachen. Die Kontrolle wird auf diese Weise zum zentralen Schauplatz der Machtausübung, die sich über das Beobachten, Speichern, Auswerten und Sortieren vollzieht. Diese Prozesse hinterlassen keinen Frei- oder Spielraum für Ambiguität; sie verwirklichen die Diktatur der klaren Kante, der Klassifizierung und Kategorisierung ohne Schattierungen. Die Macht selbst befindet sich in einem kontinuierlichen Fluss, sie ist ubiquitär, dennoch schwer lokalisierbar. Sie fungiert nicht mehr unter dem Signum einer pseudosakralen zentralen Instanz, sondern wird durch diverse Akteure und Assemblages kolportiert. Die durch sie implizierten Praktiken der Selbstkontrolle, kulturgeschichtlich ebenfalls religiös oder zumindest philosophisch konnotiert, sind die neuen Rituale des Sehens und Gesehen-Werdens.
Im Zeitalter der elektronischen Datentechnologien gibt es diverse Agenten der Überwachung. Vom besonderen Interesse sind dabei die Wearables, weil sie intim, affektiv und haptisch arbeiten und so, über das Sehen und Gesehen-Werden hinaus, das Berühren und Berührt-Werden und somit die Neuregulierung von Nähe und Distanz ins Spiel bringen. Sie schreiben sich zwar in eine Vermessungstradition eins, die ihre Ursprünge mindestens im 19. Jahrhundert hat, unterscheiden sich aber von dieser in ihrer Intensität und Sinnlichkeit.
This article is focused on the research and development of new cellulose ether derivatives as innovative superplasticizers for mortar systems. Several synthetic strategies have been pursued to obtain new compounds to study their properties on cementitious systems as new bio-based additives. The new water-soluble admixtures were synthesized using a complex carboxymethylcellulose-based backbone that was first hydrolyzed and then sulfo-ethylated in the presence of sodium vinyl sulphonate. Starting with a complex biopolymer that is widely known as a thickening agent was very challenging. Only by varying the hydrolysis times and temperatures of the reactions was achieved the aimed goal. The obtained derivatives showed different molecular weight (Mw) and anionic charges on their backbones. An improvement in shear stress and dynamic viscosity values of CEM II 42.5R cement was observed with the samples obtained with a longer time of higher temperature hydrolysis and sulfo-ethylation. Investigations into the chemical nature of the pore solution, calorimetric studies and adsorption experiments clearly showed the ability of carboxymethyl cellulose superplasticizer (CMC SP) to interact with cement grains and influence hydration processes within a 48-h time window, causing a delay in hydration reactions in the samples. The fluidity of the cementitious matrices was ascertained through slump test and preliminary studies of mechanical and flexural strength of the hardened mortar formulated with the new ecological additives yielded values in terms of mechanical properties. Finally, the computed tomography (CT) images completed the investigation of the pore network structure of hardened specimens, highlighting their promising structure porosity.
The computational analysis of argumentation strategies is substantial for many downstream applications. It is required for nearly all kinds of text synthesis, writing assistance, and dialogue-management tools. While various tasks have been tackled in the area of computational argumentation, such as argumentation mining and quality assessment, the task of the computational analysis of argumentation strategies in texts has so far been overlooked.
This thesis principally approaches the analysis of the strategies manifested in the persuasive argumentative discourses that aim for persuasion as well as in the deliberative argumentative discourses that aim for consensus. To this end, the thesis presents a novel view of argumentation strategies for the above two goals. Based on this view, new models for pragmatic and stylistic argument attributes are proposed, new methods for the identification of the modelled attributes have been developed, and a new set of strategy principles in texts according to the identified attributes is presented and explored.
Overall, the thesis contributes to the theory, data, method, and evaluation aspects of the analysis of argumentation strategies. The models, methods, and principles developed and explored in this thesis can be regarded as essential for promoting the applications mentioned above, among others.
“How to understand the interaction between urban space and social processes” is a significant question in urban studies. To answer that, the city needs to be recognized as both a physical and a social entity and urban theory and practice need to connect these (Hillier 2007). The present research aims to re-examine the complex correlation between spatial and social inequality manifestations in the city of Tehran regarding the concept of segregation.
It observes the causes and consequences of segregation in Tehran and provides an insight into both concepts of socio-spatial segregation and neighborhood effects and creates a link between them. First, I argue when, where, and for whom spatial locations affect the chances of social networks in Tehran. Then, I discuss how neighborhood effects can emerge via social network mechanisms and thus affect the perceptions of residents in the neighborhoods.
Die interdisziplinäre Dissertationsschrift lässt sich im Horizont internationaler Forschungen zu Denkmalwerten, neuer Ansätze in der Kultur- und Wissensvermittlung rund um Baudenkmale sowie künstlerisch- ethnographischem Forschen an und mit Denkmalen verorten.
Der erste Teil der Arbeit widmet sich Denkmalen und der Denkmalpflege im Kontext künstlerischer und sozialwissenschaftlicher Allianzen. Ausgangspunkt ist die Feststellung, dass die Denkmalpflege zwar sehr vieles über Denkmale weiß, aber kaum etwas über deren Rezeption beim breiten Publikum. Im Mittelpunkt steht die Frage, wie hier Praktiken der bildenden Kunst und Arbeitsweisen der Kulturanthropologie die Disziplin der Denkmalpflege bereichern können, oder sogar müssen.
Den zweiten Teil bildet eine empirische Studie, in der die populäre Wahrnehmung von Denkmalen qualitativ erforscht wird. Das Schloss und Rittergut Bedheim im südlichen ländlichen Thüringen dient dabei als konkreter Untersuchungsort. Reaktionen von Besucherinnen und Besuchern werden mit Hilfe von drei künstlerischen Eingriffen angeregt und diese dann ethnographisch-offen dokumentiert und ausgewertet.
Auf dieser Basis werden Zugänge zum Denkmal ermittelt. Während die meisten BesucherInnen das Denkmal als „Arbeit“ wahrnehmen, geraten einige ins „Träumen“ oder „Erinnern“, man „genießt“ das Ensemble als authentische und ästhetische Ressource, oder findet Zugang über das spontane „Erklären“ baukonstruktiver oder baulicher Situationen. Für andere bedeutet der Besuch die „Teilhabe“ an einem Prozess. Schloss Bedheim wird als Ort stetiger Veränderung geschätzt. In der Wahrnehmung der BesucherInnen verquicken sich Aspekte des Bewunderns mit solchen des Abgrenzens. Die eigene Alltagswelt und das eigene Zuhause bilden hierbei Bezugspunkte. Schloss Bedheim wird auf diese Weise zum Imaginationsraum, zur Energietankstelle und zur gern besuchten Problemwelt.
Die Ergebnisse der Arbeit liegen in zwei Erkenntnisfeldern: Auf einer methodischen Ebene zeigt sie, wie in der Denkmalpflege vertiefte Fachlichkeit mit einer tatsächlichen Kontaktaufnahme mit dem Publikum verbunden werden kann und damit soziale Gefüge an Baudenkmalen qualitativ ermittelt werden können. Ebenso wird deutlich, dass künstlerische Eingriffe Auslöser von Gesprächen sind, als Kontaktflächen zur Alltagswelt dienen und so zu einer vielfältigen Auseinandersetzung mit Denkmalen führen.
Auf einer inhaltlichen Ebene liefert die Arbeit Erkenntnisse zu Wahrnehmungsweisen von Denkmalen. Neben den erwähnten Zugängen, wird die Existenz und Bedeutung einer regional vernetzten Wahrnehmung von Denkmalen aufgedeckt. Des Weiteren zeigen die Ergebnisse, dass das Öffnen von Baudenkmalen als und im Prozess ungenutzte Potentiale birgt und es wird angeregt, dies in zukünftigen denkmalpflegerischen Konzepten eine größere Rolle spielen zu lassen. Die Vision eines „Kompendiums der Zugänge“ wird entwickelt, mit dessen Hilfe sich ein enormes Wissen über Rollen und Bedeutungen die Baudenkmale in unserer Gesellschaft spielen, sammeln ließe.
This thesis examines urban partition in Nicosia, the capital of Cyprus, and how its changing roles and shifting perceptions in a post-conflict setting reflect power relations, and their constant renegotiation. Nicosia, the capital of Cyprus, was officially divided in 1974 in the aftermath of an eighteen-year-long conflict between the island’s Turkish- and Greek-Cypriot communities. As a result, a heavily militarized Buffer Zone, established as an emergency measure against perpetuation of intercommunal violence, has been cutting through its historic centre ever since.
This thesis departs from a genuine interest in the material and ideational dimensions of urban partition. How is it constructed, not merely in physical terms but in the minds of the societies affected by conflict? How is it established in official and everyday discourses? What kinds of mechanisms have been developed to maintain it, and make an inseparable part of the urban experience? Moreover, taking into account the consensus in relevant literature pertaining to the imperative for its removal, this thesis is inquiring into the relevance of peace agreements to overcoming urban partition. For this purpose, it also looks at narratives and practices that have attempted to contest it.
The examples examined in this thesis offer pregnant analytical moments to understand Nicosia’s Buffer Zone as a dynamic social construct, accommodating multiple visions of and for the city. Its space ‘in-between’ facilitates encounters between various actors, accommodates new meanings, socio-spatial practices and diverse imaginaries. In this sense, urban partition is explored in this thesis as a phenomenon that transcends scales as well as temporalities, entwining past, present, and future.
This work presents a robust status monitoring approach for detecting damage in cantilever structures based on logistic functions. Also, a stochastic damage identification approach based on changes of eigenfrequencies is proposed. The proposed algorithms are verified using catenary poles of electrified railways track. The proposed damage features overcome the limitation of frequency-based damage identification methods available in the literature, which are valid to detect damage in structures to Level 1 only. Changes in eigenfrequencies of cantilever structures are enough to identify possible local damage at Level 3, i.e., to cover damage detection, localization, and quantification. The proposed algorithms identified the damage with relatively small errors, even at a high noise level.
This thesis presents the advances and applications of phase field modeling in fracture analysis. In this approach, the sharp crack surface topology in a solid is approximated by a diffusive crack zone governed by a scalar auxiliary variable. The uniqueness of phase field modeling is that the crack paths are automatically determined as part of the solution and no interface tracking is required. The damage parameter varies continuously over the domain. But this flexibility comes with associated difficulties: (1) a very fine spatial discretization is required to represent sharp local gradients correctly; (2) fine discretization results in high computational cost; (3) computation of higher-order derivatives for improved convergence rates and (4) curse of dimensionality in conventional numerical integration techniques. As a consequence, the practical applicability of phase field models is severely limited.
The research presented in this thesis addresses the difficulties of the conventional numerical integration techniques for phase field modeling in quasi-static brittle fracture analysis. The first method relies on polynomial splines over hierarchical T-meshes (PHT-splines) in the framework of isogeometric analysis (IGA). An adaptive h-refinement scheme is developed based on the variational energy formulation of phase field modeling. The fourth-order phase field model provides increased regularity in the exact solution of the phase field equation and improved convergence rates for numerical solutions on a coarser discretization, compared to the second-order model. However, second-order derivatives of the phase field are required in the fourth-order model. Hence, at least a minimum of C1 continuous basis functions are essential, which is achieved using hierarchical cubic B-splines in IGA. PHT-splines enable the refinement to remain local at singularities and high gradients, consequently reducing the computational cost greatly. Unfortunately, when modeling complex geometries, multiple parameter spaces (patches) are joined together to describe the physical domain and there is typically a loss of continuity at the patch boundaries. This decrease of smoothness is dictated by the geometry description, where C0 parameterizations are normally used to deal with kinks and corners in the domain. Hence, the application of the fourth-order model is severely restricted. To overcome the high computational cost for the second-order model, we develop a dual-mesh adaptive h-refinement approach. This approach uses a coarser discretization for the elastic field and a finer discretization for the phase field. Independent refinement strategies have been used for each field.
The next contribution is based on physics informed deep neural networks. The network is trained based on the minimization of the variational energy of the system described by general non-linear partial differential equations while respecting any given law of physics, hence the name physics informed neural network (PINN). The developed approach needs only a set of points to define the geometry, contrary to the conventional mesh-based discretization techniques. The concept of `transfer learning' is integrated with the developed PINN approach to improve the computational efficiency of the network at each displacement step. This approach allows a numerically stable crack growth even with larger displacement steps. An adaptive h-refinement scheme based on the generation of more quadrature points in the damage zone is developed in this framework. For all the developed methods, displacement-controlled loading is considered. The accuracy and the efficiency of both methods are studied numerically showing that the developed methods are powerful and computationally efficient tools for accurately predicting fractures.
In the last decades, Finite Element Method has become the main method in statics and dynamics analysis in engineering practice. For current problems, this method provides a faster, more flexible solution than the analytic approach. Prognoses of complex engineer problems that used to be almost impossible to solve are now feasible.
Although the finite element method is a robust tool, it leads to new questions about engineering solutions. Among these new problems, it is possible to divide into two major groups: the first group is regarding computer performance; the second one is related to understanding the digital solution.
Simultaneously with the development of the finite element method for numerical solutions, a theory between beam theory and shell theory was developed: Generalized Beam Theory, GBT. This theory has not only a systematic and analytical clear presentation of complicated structural problems, but also a compact and elegant calculation approach that can improve computer performance.
Regrettably, GBT was not internationally known since the most publications of this theory were written in German, especially in the first years. Only in recent years, GBT has gradually become a fertile research topic, with developments from linear to non-linear analysis.
Another reason for the misuse of GBT is the isolated application of the theory. Although recently researches apply finite element method to solve the GBT's problems numerically, the coupling between finite elements of GBT and other theories (shell, solid, etc) is not the subject of previous research. Thus, the main goal of this dissertation is the coupling between GBT and shell/membrane elements. Consequently, one achieves the benefits of both sides: the versatility of shell elements with the high performance of GBT elements.
Based on the assumptions of GBT, this dissertation presents how the separation of variables leads to two calculation's domains of a beam structure: a cross-section modal analysis and the longitudinal amplification axis. Therefore, there is the possibility of applying the finite element method not only in the cross-section analysis, but also the development for an exact GBT's finite element in the longitudinal direction.
For the cross-section analysis, this dissertation presents the solution of the quadratic eigenvalue problem with an original separation between plate and membrane mechanism. Subsequently, one obtains a clearer representation of the deformation mode, as well as a reduced quadratic eigenvalue problem.
Concerning the longitudinal direction, this dissertation develops the novel exact elements, based on hyperbolic and trigonometric shape functions. Although these functions do not have trivial expressions, they provide a recursive procedure that allows periodic derivatives to systematise the development of stiffness matrices. Also, these shape functions enable a single-element discretisation of the beam structure and ensure a smooth stress field.
From these developments, this dissertation achieves the formulation of its primary objective: the connection of GBT and shell elements in a mixed model. Based on the displacement field, it is possible to define the coupling equations applied in the master-slave method. Therefore, one can model the structural connections and joints with finite shell elements and the structural beams and columns with GBT finite element.
As a side effect, the coupling equations limit the displacement field of the shell elements under the assumptions of GBT, in particular in the neighbourhood of the coupling cross-section.
Although these side effects are almost unnoticeable in linear analysis, they lead to cumulative errors in non-linear analysis. Therefore, this thesis finishes with the evaluation of the mixed GBT-shell models in non-linear analysis.