Im Luftfahrtbereich haben sich kohlenstofffaserverstärkte Kunststoffe (CFK) wegen ihrer hohen spezifischen Festigkeiten und Steifigkeiten längst als Konstruktionswerkstoffe etabliert. In der Großserienfertigung von Automobilkarosserien kommt diese Materialgruppe jedoch nur zögerlich zum Einsatz. Offensichtlich sprechen noch viele Argumente für den Einsatz von metallischen Werkstoffen: Denn auch Leichtmetalle und pressgehärtete Stähle ermöglichen immer höhere Leichtbaugrade, ohne dabei signifikante Kostensteigerungen zu generieren. Zudem sind Fertigungs- und Montageabläufe für Metallkarosserien etabliert und weitgehend frei von Entwicklungsrisiken. Vor diesem Hintergrund erscheint es schwer, mit neuen Leichtbaumaterialien und den zugehörigen Bauweisen einen Durchbruch erzielen zu können. Dabei zeigt das Produktsegment der Supersportwagen schon deutlich, dass zusätzliche Leichtbaupotentiale durch beanspruchungsgerecht gestaltete und optimierte CFK-Strukturen für den Automobilbau eröffnet werden. Bislang lassen sich derartig optimierte CFK-Strukturen jedoch kaum wettbewerbsfähig in Großserie realisieren. An dieser Stelle ergeben sich Chancen und zugleich neue Herausforderungen für die Produktentwickler: Zum einen sind Faserverbundbauweisen zu erarbeiten, mit denen die Leichtbaupotentiale von CFK weitgehend ausgereizt werden. Zum anderen ist die automatisierte Fertigung bei hohen Taktraten zu ermöglichen. Die Lösung beider Teilaufgaben setzt den Einsatz geeigneter materialspezifischer Konstruktionsmethoden voraus.

Le travail de cette thèse a pour but de développer des outils de simulation et une méthode de dimensionnement pour les poteaux hybrides soumis à des chargements combinés. La thèse est composée de 4 parties essentielles et comprend 6 chapitres. Dans la première partie, nous développons un élément fini poutre/poteau hybride élastique et l’interaction partielle avec matrice de raideur exacte. Cet élément fini découle de la solution analytique du système d'équations différentielles couplées obtenues en combinant les équations de champs (équilibre, cinématique et comportement). Les inconnues fondamentales sont les glissements aux interfaces et la déformation de cisaillement de l'élément principal. Ces équations sont résolues pour des conditions de chargement et des conditions aux limites arbitraires en accordant un soin particulier à la détermination des constantes d'intégration. Dans la seconde partie de cette thèse, nous proposons une formulation d'élément fini originale pour l'analyse en grand déplacement des poutres hybrides avec prise en compte des glissements qui se produisent à chaque interface acier-béton. La méthode de co-rotationnelle est retenue. Dans cette approche, le mouvement de l'élément se décompose en un mouvement de corps rigide ct en une partie déformable définie dans un repère co-rotationnel local qui se déplace de manière continue avec l'élément mais qui ne se déforme pas avec ce dernier. Un choix judicieux des variables cinématiques locales accompagné des matrices de transformation correspondantes permet de transposer l'élément linéaire développé en partie 1 en un élément géométriquement non-linéaire performant. La partie 3 est consacrée à l'analyse non linéaire matérielle par élément finis de poutres hybrides en interaction partielle et soumise aux forces combinées de flexion et de cisaillement. Dans la formulation élément fini proposée, nous adoptons la discrétisation par libres et une modèle 3D de comportement du béton avec prise en compte des états plans ce qui permet de reproduire rigoureusement l'effet du confinement et l'action des étriers. En partie 4, nous évaluons la pertinence de la méthode d'amplification des moments proposées dans I'Eurocode 2 et 4 à évaluer la charge ultime de poteaux hybrides soumis à une combinaison de charge axiale et de moment de flexion uni-axial. Dans un premier temps, nous conduisons une étude paramétrique sur 1140 cas différents de poteaux hybrides; étude destinés à couvrir les différentes typologies possibles, afin de disposer d'une base de résultats permettant d'évaluer la pertinence des méthodes simplifiées de I'Eurocode 2 ct de I'Eurocode 4 pour de tels éléments. Cette étude a été réalisée à l'aide d'un élément fini non-linéaire (géométrique et matériel), avec une hypothèse de Bemouilli pour tous les composants du poteau hybride. Il ressort de cette étude que ces méthodes simplifiées ne peuvent être appliquées aux poteaux hybrides. Sur base de l'analyse d'un nombre de cas plus important (2960 configurations), la méthode d'amplification des moments est calibrée pour les poteaux hybrides. / This thesis aims at developing simulation tools and a design method for hybrid beam-columns subjected to combined axial force, bending and shear. The thesis is divided in four main parts and comprises 6 chapters. In the first part, we develop a new finite element formulation based on the exact stiffness matrix for the linear elastic analysis of hybrid beam-columns in partial interaction taking into account the shear deformability of the encasing component. This element relies on the analytical solution of a set of coupled system of differential equations in which the primary variables are the slips and the shear deformation of the encasing beam. The latter is derived by combining the governing equations (equilibrium, kinematics, constitutive laws) and solved for a specific element with arbitrary boundary conditions and loading. Special care has been taken while dealing with the constants of integration. The second part of the thesis addresses a new finite element formulation for a large displacement analysis of elastic hybrid beam-columns taking into account the slips that occur at each steel-concrete interface. The co-rotational method is adopted in which the movement of the clement is divided into a rigid body motion and a deformable portion in the local co-rotational frame which moves and rotates continuously with the element but does not deform with it. Appropriate selection of local kinematic variables along with corresponding transformation matrices allows transforming the linear finite element developed in Part I into a nonlinear one resulting in an efficient locking-free formulation. In Part 3, we derive a finite element formulation for materially nonlinear analysis of hybrid beam-columns with shear deformable encasing component, in partial interaction and subjected to the combined shear and bending. The fiber model is adopted with condensation of the 3D stress-strain relations which allow to account for confinement in a rigorous manner as well as the effect of the stirrups. Part 4 examines the adequacy of the moment magnification method given in Eurocode 2 and 4 to provide an accura te estimation of the ultimate load of hybrid columns subjected to a combination of axial load and uniaxial bending moment. The developed finite element model with a shear rigid encasing component is used to conduct a parametric study comprising 1140 cases to cover the various possible situations. The predictions of the model are compared against the values given by the simplified methods of Eurocode 2 and Eurocode 4. lt is shown that these simplified methods does not give satisfactorily results. Based on the analysis of larger number of cases (2960 configurations), the moment magnification method has been calibrated for hybrid columns.

A comprehensive study was performed to overcome the design issues related to Ocean Current Turbine (OCT) blades. Statistical ocean current models were developed in terms of the probability density function, the vertical profile of mean velocity, and the power spectral density. The models accounted for randomness in ocean currents, tidal effect, and ocean depth. The proposed models gave a good prediction of the velocity variations at the Florida Straits of the Gulf Stream. A novel procedure was developed to couple Fluid-Structure Interaction (FSI) with blade element momentum theory. The FSI effect was included by considering changes in inflow velocity, lift and drag coefficients of blade elements. Geometric non-linearity was also considered to account for large deflection. The proposed FSI analysis predicted a power loss of 3.1 % due to large deflection of the OCT blade. The method contributed to saving extensive computational cost and time compared to a CFD-based FSI analysis. The random ocean current loadings were calculated by considering the ocean current turbulence, the wake flow behind the support structure, and the velocity shear. The random ocean current loadings had large probability of high stress ratio. Fatigue tests of GFRP coupons and composite sandwich panels under such random loading were performed. Fatigue life increased by a power function for GFRP coupons and by a linearlog function for composite sandwich panels as the mean velocity decreased. To accurately predict the fatigue life, a new fatigue model based on the stiffness degradation was proposed. Fatigue life of GFRP coupons was predicted using the proposed model, and a comparison was made with experimental results. As a summary, a set of new design procedures for OCT blades has been introduced and verified with various case studies of experimental turbines. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

This study expands on the work of ElHajjar and HajAli (2003) on a quantitative thermoelastic strain analysis method for composite materials. Computational models for various prepreg and thicksection composites are validated with experiments using this quantitative strain analysis method. This study provides this thermomechanical calibrations for prepreg S2glass/epoxy, Carbon/epoxy, and pultruded Eglass/polyester. A research collaboration with the Institute of Paper Science and Technology (IPST) focused on infrared thermography for defect detection in wood and fibrous materials and structural systems. This study provides some detailed information on various testing setups for fiber and corrugated board systems to analyze anomalies and manufacturing defects. Quantitative infrared thermography is suggested as a preferred method for assessing the bond quality in corrugated paper systems. Methods for tracking fullfield thermal data during fatigue have been developed for FRP composites. The temperature changes on the surface of an FRP composite caused by damage during fatigue are tracked and thermoelastic stress analysis (TSA) technique is developed to relate the surface deformation to the IR emission. Infrared thermography is developed for fatigue damage detection in FRP composites with stochastic methods for analyzing this fullfield data. Future damage detection techniques in aging aircraft will require quantitative and noncontact nondestructive evaluation (NDE) methods especially for composite components. Infrared (IR) thermograpy techniques are qualitatively used to assess and indirectly infer the durability of structural systems. A research collaboration with Lockheed Martin for nondestructive evaluation of composite lap shear joints led to a development of thermoelastic stress analysis techniques for evaluation aerospace structures. Infrared thermography is used to investigate failure initiation and progression in composite lap shear joints.

The objective of the present study is the computational and analytical modelling of a stress and strain state of the composite laminated structures. The exact three dimensional solution is derived for laminated anisotropic thick cylinders with both constant and variable material properties through the thickness of a layer. The governing differential equations are derived in a such form that to satisfy the stress functions and are given for layered cylindrical shell with open ends. The solution then extended to the laminated cylindrical shells with closed ends, that is to pressure vessels. Based on the accurate three-dimensional stress analysis an approach for the optimal design of the thick pressure vessels is formulated. Cylindrical pressure vessels are optimised taking the fibre angle as a design variable to maximise the burst pressure. The effect of the axial force on the optimal design is investigated. Numerical results are given for both single and laminated (up to five layers) cylindrical shells. The maximum burst pressure is computed using the three-dimensional interactive Tsai-: Wu failure criterion, which takes into account the influence of all stress components to the failure. Design optimisation of multilayered composite pressure vessels are based on the use of robust multidimensional methods which give fast convergence. Transverse shear and normal deformation higher-order theory for the solution of dynamic problems of laminated plates and shells is studied. The theory developed is based on the kinematic hypotheses which are derived using iterative technique. Dynamic effects, such as forces of inertia and the direct influence of external loading on the stress and strain components are included at the initial stage of derivation where kinematic hypotheses are formulated. The proposed theory and solution methods provide a basis for theoretical and applied studies in the field of dynamics and statics of the laminated shells, plates and their systems, particularly for investigation of dynamic processes related to the highest vibration forms and wave propagation, for optimal design etc. Geometrically nonlinear higher-order theory of laminated plates and shells with shear and normal deformation is derived. The theory takes into account both transverse shear and normal deformations. The number of numerical results are obtained based on the nonlinear theory developed. The results illustrate importance of the influence of geometrical nonlinearity, especially, at high levels of loading and in case when the laminae exhibit significant differences in their elastic properties. / Thesis (Ph.D.)-University of Natal, Durban, 1995.

Spanwise nonuniformity effects are modeled in the cross-sectional analysis of beam theory. This modeling adheres to an established numerical framework on cross-sectional analysis of uniform beams with arbitrary cross-sections. This framework is based on two concepts: decomposition of the rotation tensor and the variational-asymptotic method. Allowance of arbitrary materials and geometries in the cross-section is from discretization of the warping field by finite elements. By this approach, dimensional reduction from three-dimensional elasticity is performed rigorously and the sectional strain energy is derived to be asymptotically-correct. Elastic stiffness matrices are derived for inputs into the global beam analysis. Recovery relations for the displacement, stress, and strain fields are also derived with care to be consistent with the energy. Spanwise nonuniformity effects appear in the form of pointwise and sectionwise derivatives, which are approximated by finite differences. The formulation also accounts for the effects of spanwise variations in initial twist and/or curvature. A linearly tapered isotropic strip is analyzed to demonstrate spanwise nonuniformity effects on the cross-sectional analysis. The analysis is performed analytically by the variational-asymptotic method. Results from beam theory are validated against solutions from plane stress elasticity. These results demonstrate that spanwise nonuniformity effects become significant as the rate at which the cross-sections vary increases. The modeling of transverse shear modes of deformation is accomplished by transforming the strain energy into generalized Timoshenko form. Approximations in this transformation procedure from previous works, when applied to uniform beams, are identified. The approximations are not used in the present work so as to retain more accuracy. Comparison of present results with those previously published shows that these approximations sometimes change the results measurably and thus are inappropriate. Static and dynamic results, from the global beam analysis, are calculated to show the differences between using stiffness constants from previous works and the present work. As a form of validation of the transformation procedure, calculations from the global beam analysis of initially twisted isotropic beams from using curvilinear coordinate axes featuring twist are shown to be equivalent to calculations using Cartesian coordinates.

Bibliography: leaves 140-144. / xix, 156 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Determines the effect of partial-interaction and interfacial friction on the fatigue behaviour of composite bridge beams and develops a set of design rules for the assessment of the residual strength and performance of composite bridge beams. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1999

Orientador: Leandro Palermo Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-12T00:34:01Z (GMT). No. of bitstreams: 1 Gaiga_Flavio_M.pdf: 4138952 bytes, checksum: a8e6c34a3ba774087ac02c45444601ca (MD5) Previous issue date: 2008 / Resumo: Na construção civil, o uso racional do aço e concreto na composição de seções estruturais é uma forma economicamente e estruturalmente viável, principalmente em edifícios de múltiplos andares. Dentre o vasto campo denominado "estruturas mistas aço concreto", podemos caracterizar os pilares mistos parcialmente revestidos como um perfil de aço estrutural do tipo "I" ou "H" revestido com concreto, armadura longitudinal e transversal, e conectores de cisalhamento nas mesas e alma. Na determinação da resistência dos pilares mistos, parte-se da hipótese básica de que há interação completa entre os dois materiais, e que não haja escorregamento relativo entre as duas superfícies. Tendo em vista estes aspectos, neste trabalho são apresentados modelos numéricos tridimensionais de pilares mistos com o objetivo de simular o seu comportamento estrutural. As simulações foram feitas utilizando o programa ANSYS versão 9.0, com base no Método dos Elementos Finitos (MEF). Com o objetivo de validar a estratégia de análise foram construídos modelos numéricos comparando os resultados obtidos com os provenientes de análise experimental, extraídos de trabalhos apresentados por outros pesquisadores. A partir desta análise numérica foi aplicado o método simplificado proposto pela ABNT/NBR:14323/99 no dimensionamento de um pilar misto parcialmente revestido, comparando os resultados analíticos com os provenientes da análise numérica via MEF, e identificando as regiões de aplicação de cargas e transferência de esforços na interface aço concreto. / Abstract: The rational use of the steel and concrete in buildings, in the composition of structural sections is a economically form and structural viable, mainly in multi storey buildings. Among the vast field called "steel-concrete composite structures", we can characterize the composite columns encased like a profile of structural steel of the type "I" or "H" covered with concrete, longitudinal and transversal bars, and shear connectors in flange and web. For determination of the strength of the composite columns, it starts of the basic hypothesis that there is complete interaction among the two materials, and that there is not relative relationship among the two surfaces. Despite these aspects, this work presents three-dimensional numeric models of composite columns with the goal of simulating shearing structural behavior. The simulations were made using the software ANSYS version 9.0, based on the Finite Element Method (FEM). With the purpose of validating the analysis strategy numeric models it were built comparing the results obtained with the coming of experimental analysis, extracted from works presented by other researchers. From this numerical analysis it was applied the simplified method proposed by ABNT/NBR:14323/99 for the design of a partially encased composite column, comparing the analytical results with the coming of numerical analysis using FEM, and identifying the regions of loads application and transfer in the interface steel-concrete. / Mestrado / Estruturas / Mestre em Engenharia Civil

Mit der Entwicklung von Bewertungssystemen für das Nachhaltige Bauen und der Zertifizierung von Gebäuden gewinnen Kriterien ergänzend zur Funktionalität, Wirtschaftlichkeit und Standsicherheit zunehmend an Bedeutung. Neben der Aufarbeitung wesentlicher Hintergründe dieser Systeme bedarf es Verfahren für die Praxis, Gebäude nach Nachhaltigkeitskriterien zu planen und zu bauen. Im Rahmen der vorliegenden Dissertation „Nachhaltige Bürogebäude in Stahl- und Stahlverbundbauweise“ werden Methoden zur Optimierung von Tragkonstruktionen in Stahl- und Verbundbauweise nach ökologischen und ökonomischen Kriterien vorgestellt. Auf der Basis umfangreicher Parameterstudien werden Empfehlungen zur Konstruktion und Bemessung nachhaltiger Decken- und Stützensysteme für Bürogebäude abgeleitet. Ausgehend von den deutschen Bewertungssystemen DGNB und BNB werden die Grundlagen und Methoden zur Bewertung der ökologischen und ökonomischen Nachhaltigkeit von Tragkonstruktionen abgeleitet. Als Basis der Parameterstudien werden Ökobilanzdaten von Baumaterialien und -produkte, Herstellungsprozesse und Transporte aus generischen Daten, Datenbanken und Umweltproduktdeklarationen mit dem Ziel einer möglichst vollständigen Lebenszyklusanalyse zusammengestellt. Ergänzend hierzu werden Kosten für Baumaterialien und -prozesse auf der Basis von Baukostenkatalogen und Expertenbefragungen ermittelt. Es folgen Parameterstudien zu Unterzugs- und Flachdecken, Stützen und Anschlüssen, bevor die Decken-Stützen-Systemen von Geschossbauten in ihrer Gesamtheit untersucht werden. Dabei werden die Bauweisen, Rastermaße, Materialgüten, Konstruktionsformen und Nutzlasten variiert, um den Einfluss der jeweiligen Parameter isoliert und in Kombination zu verdeutlichen. Zusammenfassend werden aus den Ergebnissen Empfehlungen zur nachhaltigen Gestaltung der Tragkonstruktionen für Bürogebäude in Stahl- und Stahlverbundbauweise abgeleitet.:Inhaltsverzeichnis 1 Einleitung 1.1 Problemstellung und Zielsetzung 1.2 Aufbau der Arbeit 2 Bürogebäude 2.1 Allgemein 2.2 Büroorganisationsformen 2.3 Grundriss und Höhenentwicklung 2.3.1 Grundrissgestaltung 2.3.2 Höhenentwicklung 3 Bausysteme in Stahl- und Stahlverbundbauweise 3.1 Allgemeines 3.2 Deckensysteme 3.3 Stützen 3.4 Anschlüsse 3.5 Systemwahl und Rastermaße 4 Technische Anforderungen 4.1 Lastannahmen 4.2 Korrosionsschutz 4.3 Brandschutz 4.4 Schallschutz 4.5 Technische Gebäudeausrüstung 5 Nachhaltigkeit von Bürogebäuden 5.1 Begriff Nachhaltigkeit 5.2 Richtlinien und Gesetze 5.3 Normative Grundlagen 5.4 Bewertungssysteme für Bürogebäude 5.5 Ökologische Nachhaltigkeit 5.5.1 Methodik zur Ökobilanzierung 5.5.2 Auswahl der Bewertungskriterien 5.5.3 Datengrundlagen 5.5.4 Bewertungssystem für Tragkonstruktionen 5.6 Ökonomische Nachhaltigkeit 6 Bemessung 6.1 Allgemeines 6.2 Grenzzustand der Tragfähigkeit 6.2.1 Decken 6.2.2 Unterzugsträger als Verbundträger 6.2.3 Schweißprofile 6.2.4 Slim-Floor-Träger 6.2.5 Stützen 6.2.6 Anschlüsse 6.3 Grenzzustand der Gebrauchstauglichkeit 6.3.1 Begrenzung der Verformungen 6.3.2 Verformungen von Decken 6.3.3 Verbundträger 6.3.4 Slim-Floor-Träger 6.3.5 Rissbreitenbegrenzung 6.3.6 Schwingungen 6.4 Bemessung im Brandfall 6.4.1 Normative Grundlagen 6.4.2 Brandschutzprodukte 6.4.3 Decken 6.4.4 Unterzugsträger 6.4.5 Slim-Floor-Träger 6.4.6 Stützen 6.4.7 Anschlüsse 7 Programmdokumentation 7.1 Überblick 7.2 Programmstruktur im Allgemeinen 7.3 Decken 7.3.1 Stahlbetondecken und Spannbetonhohldielen 7.3.2 Verbunddecken 7.4 Deckensystem 7.4.1 Unterzugsdecken mit Walzprofilen 7.4.2 Unterzugsdecken mit Schweißprofilen 7.4.3 Slim-Floor-Konstruktionen 7.5 Stützen 8 Nachhaltige Material- und Konstruktionswahl 8.1 Erläuterungen zu den Parameterstudien 8.2 Decken 8.2.1 Stahlbetondecken aus Ortbeton 8.2.2 Verbunddecken 8.2.3 Decken im Vergleich 8.3 Unterzugsdecken 8.3.1 Variation der Trägerabstände 8.3.2 Variation der Nutzlasten 8.3.3 Vergleich Ein- und Zweifeldträger 8.3.4 Variation der Stahlgüte und der Durchbiegungsbegrenzung 8.3.5 Variation der Betongüte 8.3.6 Schweißprofile 8.4 Slim-Floor-Konstruktionen 8.4.1 Variation der Trägerabstände und des Deckentyps 8.4.2 Variation der Querschnittstypen 8.4.3 Untersuchung von Deckensystemen mit Einfeldträgern 8.4.4 Variation der Nutzlast 8.5 Vergleich von Unterzugsdecken und Slim-Floor-Konstruktionen 8.6 Stützen 8.6.1 Querschnittswahl 8.6.2 Materialgüten 8.6.3 Einfluss der Stützenhöhe 8.6.4 Berücksichtigung von Maßnahmen zum Brandschutz 8.7 Anschlüsse 8.8 Tragkonstruktion 8.8.1 Tragkonstruktionen mit Unterzugsdecken 8.8.2 Tragkonstruktionen mit Slim-Floor-Systemen 8.8.3 Vergleich der Tragsysteme mit Unterzugsdecken und Slim-Floor 9 Zusammenfassung und Ausblick 9.1 Allgemeines 9.2 Unterzugsdecken 9.3 Slim-Floor-Konstruktionen 9.4 Stützen 9.5 Anschlüsse 9.6 Ausblick 10 Quellenverzeichnis 11 Anhang Anhang A Büroorganisationsformen Anhang B Schallschutz Anhang C Datengrundlagen Anhang D Bemessung und Produktdaten Anhang E Anschlüsse

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