TY - CHAP A1 - Schutte, Gerrit T1 - Zur Ermittlung von Spannungen am Rand eines elastischen Kontinuums N2 - Für den Entwurf von Ingenieurbauten ist eine zuverlässige Prognose über den Spannungsverlauf im Bauwerk und auf dessen Rand von großer Bedeutung. Eine geschlossene Lösung der elastischen Bestimmungsgleichungen des Bauwerks ist in der Regel nicht verfügbar. Es wird daher unter Verwendung der Methode der gewichteten Reste eine schwache Form der Gleichungen abgeleitet, die zu einem gemischten Arbeitsprinzip führt. Das zugehörige Finite-Elemente-Modell erlaubt es Spannungen am Rand des Bauwerks zu ermitteln, die im Gleichgewicht zu den angreifenden Lasten stehen. KW - Kontinuum KW - Elastizitätstheorie KW - Randspannung KW - Finite-Elemente-Methode Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-6135 ER - TY - CHAP A1 - Köppler, H. A1 - Roos, Dirk A1 - Burkhardt, Gerhard T1 - Zur Berechnung vielschichtiger Schalen mit orthotropen Schichten N2 - Wirklichkeitsnahe Erfassung und Beschreibung des Trag- und Verformungsverhaltens von Strukturen baulicher Anlagen hat in den letzten Jahrzehnten ständig an Bedeutung gewonnen. Konstruktionen im Hoch- und Industriebau werden zunehmend multifunktional genutzt - die >Grenzen< zwischen Bauwerk und Tragwerk, zwischen Hüll- und Tragkonstruktion lösen sich auf. Werden raumabschließende Elemente (Wände, Decken, Dächer) gleichzeitig als Tragelemente und wärme- und schalldämmende Konstruktionen ausgeführt, so entstehen beispielsweise Sandwichplatten, deren Schichten sehr stark differierende Materialeigenschaften aufweisen. Beim Aufbau des FEM-Modells für vielschichtige Schalen können die Formänderungshypothesen für jede Schicht einzeln als auch für die Schale insgesamt gegeben werden. Im ersten Fall ist der Knotenfreiheitsgrad von der Schichtenzahl abhängig, im zweiten Fall nicht. Im weiteren wird eine Formänderungshypothese für das Schichtenpaket angenommen. Ausgegangen wird von den Gleichungen der 3D-Elastizitätstheorie. Die Berücksichtigung der Querkraftschubverformungen ergibt die Möglichkeit einer adäquaten Beschreibung der Verformungen sowohl dünner Schalen als auch von Schalen mittlerer Dicke; die Berechnung der Krümmungen und der LAMEschen Parameter der Bezugsfläche zu umgehen, was für komplizierte Schalenformen eine selbständige Aufgabe ist; eines natürlichen Übergangs von homogenen zu geschichteten Schalen. Das vielschichtige isoparametrische Schalen-FE wird vorgestellt, seine Implementierung in das in Entwicklung befindliche Programmsystem SLANG wird vorbereitet. KW - Schale KW - Sandwichbauweise KW - Orthotropes Bauteil KW - Finite-Elemente-Methode Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-4379 ER - TY - JOUR A1 - Kaapke, Kai A1 - Milbradt, Peter T1 - Voronoi-based finite volume method for transport problems N2 - Transport problems, as, for instance, the transport of sediment in hydraulic engineering and the transport of harmful substances through porous media, play an important role in many fields of civil engineering. Other examples include the dissipation of heat or sound as well as the simulation of traffic with macroscopic models. The contribution explains the analysis of the applicability of Voronoi-based finite volume methods for the approximation of solutions of transport problems. A special concern is the discretisation of the transport equation. Current limitations of the method as well as ideas for stabilisation are explained with examples. KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Transport Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2558 ER - TY - JOUR A1 - Ganev, T. A1 - Marinov, M. T1 - Towards Optimal Designing of thin elastic Plates with a specific free Oscillations Frequency N2 - Thin elastic plates are the basic constructional elements and are very often subjected to dynamic effects especially in the machine-building structures. Their saving design of resonance conditions of operation is an extremely complicated task which cannot be solved analytically. In the present report an efficient and sufficiently general method for optimal design of thin plates is worked out on the basis of energy resonance method of Wilder, the method of the finite elements for dynamic research and the methods of parameter optimization. By means of these methods various limitations and requirements put by the designer to the plates can be taken into account. A programme module for numerical investigation of the weight variation of the plate depending on the taken variable of the designed thickness at different supporting conditions is developed. The reasons for the considerable quantity and quality difference between the obtained optimal designs are also analysed. KW - Platte KW - Optimierung KW - Freie Schwingung KW - Finite-Elemente-Methode Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5375 ER - TY - CHAP A1 - Bernstein, Swanhild A1 - Richter, Matthias T1 - The Use of Genetic Algorithms in Finite Element Model Identification N2 - A realistic and reliable model is an important precondition for the simulation of revitalization tasks and the estimation of system properties of existing buildings. Thereby, the main focus lies on the parameter identification, the optimization strategies and the preparation of experiments. As usual structures are modeled by the finite element method. This as well as other techniques are based on idealizations and empiric material properties. Within one theory the parameters of the model should be approximated by gradually performed experiments and their analysis. This approximation method is performed by solving an optimization problem, which is usually non-convex, of high dimension and possesses a non-differentiable objective function. Therefore we use an optimization procedure based on genetic algorithms which was implemented by using the program package SLang... KW - Finite-Elemente-Methode KW - Genetischer Algorithmus Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2769 ER - TY - JOUR A1 - Tolok, V. A. A1 - Tolok, A. V. A1 - Gomenyuk, S. I. T1 - The instrumental System of Mechanics Problems Analysis of the deformed Solid Body N2 - In the abstract proposed is the Instrumental System of mechanics problems analysis of the deformed solid body. It supplies the researcher with the possibility to describe the input data on the object under analyses and the problem scheme based upon the variational principles within one task. The particular feature of System is possibility to describe the information concerning the object of any geometrical shape and the computation sheme according to the program defined for purpose. The Methods allow to compute the tasks with indefinite functional and indefinite geometry of the object (or the set of objects). The System provides the possibility to compute the tasks with indefinite sheme based upon the Finite Element Method (FEM). The restrictions of the System usage are therefore determined by the restrictions of the FEM itself. It contrast to other known programms using FEM (ANSYS, LS-DYNA and etc) described system possesses more universality in defining input data and choosing computational scheme. Builtin is an original Subsytem of Numerical Result Analuses. It possesses the possibility to visualise all numerical results, build the epures of the unknown variables, etc. The Subsystem is approved while solving two- and three-dimensional problems of Elasticiti and Plasticity, under the conditions of Geometrical Unlinearity. Discused are Contact Problems of Statics and Dynamics. KW - Festkörpermechanik KW - Finite-Elemente-Methode Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5361 ER - TY - JOUR A1 - Ke, Chen A1 - Jian Ming, Lu T1 - Study of Analysis System for Bridge Test N2 - Analysis System for Bridge Test (Chinese name abbr.: QLJC) is an application software specially designed for bridge test to analyze the static and dynamic character of bridge structures, calculate efficiency ratio of load test, pick up the results of observation points and so on. In this paper, research content, system design, calculation theory, characteristics and practical application of QLJC is introduced in detail. KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Brückenbau KW - Straßenbrücke Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2547 ER - TY - CHAP A1 - Milbradt, Peter T1 - Stabilisierte Finite Elemente in der Hydrodynamik N2 - Hydro- und morphodynamischen Prozesse in Binnengewässern und im Küstennahbereich erzeugen hochkomplexe Phänomene. Zur Beurteilung der Entwicklung von Küstenzohnen, von Flussbetten sowie von Eingriffen des Menschen in Form von Schutzbauwerken sind geeignete numerische Modellwerkzeuge notwendig. Es wird ein holistischer Modellansatz zur Approximation gekoppelter Seegangs-, Strömungs- und Morphodynamischer Prozesse auf der Basis stabilisierter Finiter Elemente vorgestellt. Der Großteil der Modellgleichungen der Hydro- und Morphodynamik sind Transportgleichungen. Dem Transportcharakter dieser Gleichungen entsprechend wird ein stabilisiertes Finites Element Verfahren auf Dreiecken vorgestellt. Die vorgestellte Approximation entspricht einem streamline upwinding Petrov-Galerkin-Verfahrens für vektorwertige mehrdimensionale Probleme, bei dem der Fehler eines Standard-Galerkin-Verfahrens mit Hilfe eines Upwinding-Koeffizienten minimiert wird. Die Wahl des Upwinding-Koeffizienten ist übertragbar auf andere Problemklassen und basiert ausschließlich auf dem Charakter der zugrundeliegene Das Modell wurde für Seegangs- und Strömungs-Untersuchungen im Jade-Weser-Ästuar an der deutschen Nordseeküste eingesetzt. KW - Hydrodynamik KW - Finite-Elemente-Methode Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-3327 ER - TY - JOUR A1 - Lämmer, Lutz A1 - Burghardt, Michael A1 - Meißner, Udo F. T1 - Parallele Netzgenerierung N2 - Bei der Berechnung von statischen oder dynamischen Problemen mit Hilfe der Methode der Finiten Elemente ist eine Diskretisierung des zu berechnenden Gebietes notwendig. Bei einer sinnvollen Modellierung des Gebietes ist die Elementgröße meist nicht konstant, sondern ist an kritischen Stellen kleiner. Die Vorgaben hierfür können einerseits aus Erfahrungen des Anwenders, andererseits aus einer Fehlerabschätzung einer vorangegangenen FE-Berechnung resultieren [5]. Soll die FE-Berechnung auf einem Parallelrechner geschehen, ist eine Partitionierung des Gebietes, d.h. eine Zuordnung der Elemente zu den Prozessoren, notwendig. Bei dem hier beschriebenen Ansatz werden nun im Gegensatz zu den üblichen Verfahren erst die Eingangsdaten für den Netzgenerator umgewandelt und dann das Elementnetz direkt auf dem Parallelrecher gleichzeitig auf allen Prozessoren erzeugt. Eine Aufteilung der Elemente auf die Prozessoren entsteht als Nebenprodukt der Netzaufteilung. Die entstehenden Teilgebietsgrenzen werden geometrisch minimiert. Die Lastbalance der Netzaufteilung sowie der FE-Rechnung wird durch ein annähernd gleiche Anzahl der Elemente je Partition gewährleistet. Als Eingabedaten wird eine Beschreibung des Gebietes durch Polygonzüge, sowie einer Netzdichtefunktion, z.B. durch Punkte mit Angaben über die angestrebte Elementgröße, benötigt. KW - Finite-Elemente-Methode KW - Gittererzeugung Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5315 ER - TY - CHAP A1 - Baitsch, Matthias A1 - Hartmann, Dietrich T1 - Object Oriented Finite Element Analysis for Structural Optimization using p-Elements N2 - The optimization of continuous structures requires careful attention to discretization errors. Compared to ordinary low order formulation (h-elements) in conjunction with an adaptive mesh refinement in each optimization step, the use of high order finite elements (so called p-elements) has several advantages. However, compared to the h-method a higher order finite element analysis program poses higher demands from a software engineering point of view. In this article the basics of an object oriented higher order finite element system especially tailored to the use in structural optimization is presented. Besides the design of the system, aspects related to the employed implementation language Java are discussed. KW - Konzipieren KW - Bauwerk KW - Finite-Elemente-Methode Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-1089 ER - TY - CHAP A1 - Schlegel, Roger A1 - Rautenstrauch, Karl T1 - Numerische Simulation von Mauerwerk als Kontinuum N2 - Im vorliegenden Beitrag wird ein in das FE-Programmsystem ANSYS implementiertes elastoplastisches Berechnungsmodell zur nichtlinearen, räumlichen Untersuchung von Mauerwerkstrukturen vorgestellt. Die Modellierung des heterogenen Baustoffs Mauerwerk erfolgt mit Hilfe eines verschmierten Ersatzkontinuums. Das anisotrope Materialverhalten wird sowohl hinsichtlich der Spannungs-Dehnungsbeziehung als auch bei der Beschreibung der Festigkeit berücksichtigt. Durch die Verwendung einer zusammengesetzten Fließbedingung ist es möglich, das Versagen der einzelnen Mauerwerkkomponenten Stein und Mörtelfugen und des Verbundes zu berücksichtigen. Dadurch ist die Anwendbarkeit des Modells für mehrere Mauerwerksarten gegeben. Die hierfür verwendeten Materialparameter sind aus einfachen Kleinkörperversuchen bestimmbar oder innerhalb gewisser Grenzen aus empirischen Formeln berechenbar. Die notwendige Beschränkung der Anzahl der Materialparameter sichert die praktische Anwendbarkeit des entwickelten Berechnungsmodells. Die numerische Umsetzung des hier verwendeten impliziten Berechnungsverfahrens lässt sich in eine lokale und eine globale Iterationsebene gliedern. Die lokale Iteration am Integrationspunkt dient der Spannungsrückführung. Dabei sind die Besonderheiten der Verarbeitung mehrflächiger Fließfiguren zu beachten. Die globale Iteration auf Systemebene sichert die Umlagerung des Residuums. Mit der Nachrechnung von Versuchsergebnissen soll das entwickelte Modell verifiziert und seine physikalische Leistungsfähigkeit eingeschätzt werden. KW - Mauerwerk KW - Modellierung KW - Elastoplastizität KW - Finite-Elemente-Methode KW - ANSYS KW - Zusammengesetzte Fließbedingung KW - Kontinuum Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-6106 ER - TY - CHAP A1 - Milbradt, Peter A1 - Rose, Martin T1 - Numerische Approximation makroskopischer Verkehrsmodelle mit der Methode der Finiten Elemente N2 - Makroskopische Verkehrsmodelle sind ein wesentliches Hilfsmittel bei der Beurteilung und Steuerung von Verkehrsflüssen auf Hauptverkehrsadern. Für die notwendige Beeinflussung des Verkehrsablaufs werden Online-Messungen und prognostische numerische Simulationen benötigt. Für die Simulationen bieten sich makroskopische Verkehrsmodelle an, die den Verkehr als kontinuierliche Fahrzeugströmeabbilden. Aufgrund der Analogie zu den Modellen der Strömungsmechanik lassen sich die numerischen Verfahren aus diesem Bereich auch zur Lösung makroskopischer Verkehrsmodelle verwenden. Es wird eine Finite-Elemente-Approximation für die numerische Umsetzung makroskopischer Verkehrsmodelle vorgestellt. Exemplarisch wird sie am Verkehrsmodell von Kerner und Konhäuser erläutert. Dieses und andere makroskopische Verkehrsmodelle wurden bisher mit der Methode der Finiten Differenzen gelöst. Die vorgestellte Approximation entspricht einem Petrov-Galerkin-Verfahren, bei dem der Fehler eines Standard-Galerkin-Verfahrens mit Hilfe eines Upwinding-Koeffizienten minimiert wird. Die Wahl des Upwinding-Koeffizienten ist übertragbar und basiert ausschließlich auf dem Charakter der zugrundeliegenden Gleichungen. Die Ergebnisse zeigen typische Phänomene eines Verkehrsablaufs wie die Entstehung von Stop-and-Go-Wellen oder Staus. Die Finite-Elemente-Methode erweist sich für unter-schiedlichste Verkehrsmodelle als ausgesprochen stabil. KW - Verkehrsleitsystem KW - Modellierung KW - Finite-Elemente-Methode Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-6046 ER - TY - CHAP A1 - Kirichuk, A. A1 - Köppler, H. T1 - Numerical Algorithms and Computer Modeling for nonlinear Analysis of Shell Structures N2 - The dynamic behaviour of shells, which are widely used in construction and mechanical engineering as critical components of machinery and 3-D structures, under static and dynamic loadings is described by system of deep nonlinear differential equations. Solution of these equations can be received with assistance of technique basing on a modern numerical algorithms and computer modeling.. The system of nonlinear differential equations of vibration of the shells is proposed taking into account the inertia forces in the tangential and normal directions. Its solution is based on combination of parameter prolongation method, finite-difference method and the Newton-Kantorovich iterative algorithm that allows plotting the loading trajectories and determination of bifurcation points on them. Package of Applied Programs >SEVSOR< is a computation means to be used in research of deformation, stability and vibration in thin axically-symmetric shells of complicated shape Input data include information on shell geometry, physical and mechanical properties, bearing conditions, types of loadings and load application. Frame output of motion forms in real time or either in decelerated or accelerated time scales for creating cartoons or video films is used for analysis of the compound dynamic processes in shell-type structures. KW - Schale KW - Nichtlineares Phänomen KW - Modellierung KW - Finite-Elemente-Methode Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-4382 ER - TY - CHAP A1 - van Rooyen, G.C. A1 - Olivier, A. H. T1 - Notes on structural analysis in a distributed collaboratory N2 - 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. KW - Ingenieurbau KW - Verteiltes System KW - Planungsprozess KW - Modellierung KW - Finite-Elemente-Methode Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-1451 ER - TY - CHAP A1 - Ebert, Matthias A1 - Bucher, Christian T1 - Modelling of changing of dynamic and static parameters of damaged R/C N2 - Dynamic testing for damage assessment as non-destructive method has attracted growing in-terest for systematic inspections and maintenance of civil engineering structures. In this con-text the paper presents the Stochastic Finite Element (SFE) Modeling of the static and dy-namic results of own four point bending experiments with R/C beams. The beams are dam-aged by an increasing load. Between the load levels the dynamic properties are determined. Calculated stiffness loss factors for the displacements and the natural frequencies show differ-ent histories. A FE Model for the beams is developed with a discrete crack formulation. Cor-related random fields are used for structural parameters stiffness and tension strength. The idea is to simulate different crack evolutions. The beams have the same design parameters, but because of the stochastic material properties their undamaged state isn't yet the same. As the structure is loaded a stochastic first crack occurs on the weakest place of the structure. The further crack evolution is also stochastic. These is a great advantage compared with de-terministic formulations. To reduce the computational effort of the Monte Carlo simulation of this nonlinear problem the Latin-Hypercube sampling technique is applied. From the results functions of mean value and standard deviation of displacements and frequencies are calcu-lated. Compared with the experimental results some qualitative phenomena are good de-scribed by the model. Differences occurs especially in the dynamic behavior of the higher load levels. Aim of the investigations is to assess the possibilities of dynamic testing under consideration of effects from stochastic material properties KW - Stahlbetonbauteil KW - Bruchmechanik KW - Dynamische Belastung KW - Statische Last KW - Finite-Elemente-Methode KW - Stochastisches Modell Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5825 ER - TY - CHAP A1 - Popova, E. D. A1 - Datcheva, Maria A1 - Iankov, Roumen T1 - Mechanical Models with Interval Parameters N2 - In this paper we consider modelling of composite material with inclusions where the elastic material properties of both matrix and inclusions are uncertain and vary within prescribed bounds. Such mechanical systems, involving interval uncertainties and modelled by finite element method, can be described by parameter dependent systems of linear interval equations and process variables depending on the system solution. A newly developed hybrid interval approach for solving parametric interval linear systems is applied to the considered model and the results are compared to other interval methods. The hybrid approach provides very sharp bounds for the process variables - element strains and stresses. The sources for overestimation when dealing with interval computations are demonstrated. Based on the element strains and stresses, we introduce a definition for the values of nodal strains and stresses by using a set-theoretic approach. KW - Verbundwerkstoff KW - Modellierung KW - Finite-Elemente-Methode Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-3482 ER - TY - JOUR A1 - Galffy, Mozes A1 - Wellmann Jelic, Andres A1 - Hartmann, Dietrich T1 - Lifetime-oriented modelling of vortex-induced across-wind vibrations on bridge tie rods N2 - The influence of vortex-induces vibrations on vertical tie rods has been proved as a determinant load factor in the lifetime-oriented dimensioning of arched steel bridges. Particularly, the welded connection plates between the suspenders and the arches often exhibit cracks induced primarily rods. In this context, the synchronization of the vortex-shedding to the rod motion in a critical wind velocity range, the so-called lock-in effect, is of essential interest. KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Brückenbau KW - Schwingung Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2536 ER - TY - JOUR A1 - Kashiyama, Kazuo A1 - Hamada, Hidetaka A1 - Taniguchi, Takeo T1 - Large Scale Finite Element Simulation and Modeling Using GIS/CAD for Environmental Flows in Urban Area N2 - A large-scale computer modeling and simulation method is presented for environmental flows in urban area. Several GIS and CAD data were used for the preparation of shape model and an automatic mesh generation method based on Delaunay method was developed. Parallel finite element method based on domain decomposition method was employed for the numerical simulation of natural phenomena. The present method was applied to the simulation of flood flow and wind flow in urban area. The present method is shown to be a useful planning and design tool for the natural disasters and the change of environments. KW - Geoinformationssystem KW - Finite-Elemente-Methode KW - Stadtplanung Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2675 ER - TY - CHAP A1 - Gurtovy, O. G. A1 - Piskunov, V. G. T1 - HIGH-PRECISION MODELING AND FINITE-ELEMENT INVESTIGATION OF ELASTOPLASTIC DEFORMATION OF NON-ISOTROPIC THICK SANDWICH PLATES AND SHELLS N2 - There was suggested a phenomenological modified quadratic condition of the beginning of plasticity for plastic and quasifragile orthotropic materials. Limiting surface in the shape of a paraboloid with an axis bend over hydrostatic axis corresponds to the condition. The equations of theory of current with the isotropic and anisotropic hardenings, associated with the suggested yield condition, modified into the version of determining equations of strain theory of plasticity are received. These defining equations formed the basis of highlyprecise non-classic continual (along thickness) theory of non-linear deformation of thick sandwich plates and sloping shells. In the approximations along the cross coordinate the specificity of flexural and non-flexural deformations is taken into account. The necessity of introducing the approximations of higher order, as well as accounting for the cross compression while decreasing of the relatively cross normal and shear layer rigidness is shown. The specifications, obtained in comparison with the known physically nonlinear specified model of the bending of plates with orthotropic layers are distinguished. An effective procedure of linearization of the solving equations and getting the solutions in frames of the discrete-continual scheme of the finite-element method is suggested. The approximations of higher order let to model the appearance of the cracs of layers being split by the introducing of slightly hard thin layers into the finite element, not violating the idea of continuality of theory. Calculation of a threelayer plate with rigid face diaphragms on the contour is considered KW - Platte KW - Schale KW - Sandwichbauteil KW - Elastoplastizität KW - Finite-Elemente-Methode Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5848 ER - TY - CHAP A1 - Milbradt, Peter A1 - Schwöppe, Axel T1 - Finite Element Approximation auf der Basis geometrischer Zellen N2 - Die Methode der Finiten Elemente ist ein numerisches Verfahren zur Interpolation vorgegebener Werte und zur numerischen Approximation von Lösungen stationärer oder instationärer partieller Differentialgleichungen bzw. Systemen partieller Differentialgleichungen. Grundlage dieser Verfahren ist die Formulierung geeigneter Finiter Elemente und Finiter Element Zerlegungen. Finite Elemente besitzen in der Regel eine geometrische Basis bestehend aus Strecken im eindimensionalen, Drei- oder Vierecken im zweidimensionalen und Tetra- oder Hexaedern im dreidimensionalen euklidischen Raum, eine Menge von Freiheitsgraden und eine Basis von Funktionen. Die geometrische Basis eines Finiten Elements wird verallgemeinert als geometrische Zelle formuliert. Diese geschlossene geometrische Formulierung führt zu einer geometrieunabhängigen Definition der Basisfunktionen eines Finiten Elements in den Zellkoordinaten der geometrischen Zelle. Finite Elemente auf der Basis geometrischer Zellen werden als Bestandteile Finiter Element Zerlegungen in Finiten Element Interpolationen und Finiten Element Approximationen verwendet. Die Finiten Element Approximationen werden am Beispiel der 2-dimensionalen Diffusionsgleichung über das Standard-Galerkin-Verfahren ermittelt. KW - Finite-Elemente-Methode KW - Approximation Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-3333 ER - TY - JOUR A1 - Milbradt, Peter A1 - Schierbaum, Jochen A1 - Schwöppe, Axel T1 - Finite Cell-Elements of Higher Order N2 - The method of the finite elements is an adaptable numerical procedure for interpolation as well as for the numerical approximation of solutions of partial differential equations. The basis of these procedure is the formulation of suitable finite elements and element decompositions of the solution space. Classical finite elements are based on triangles or quadrangles in the two-dimensional space and tetrahedron or hexahedron in the threedimensional space. The use of arbitrary-dimensional convex and non-convex polyhedrons as the geometrical basis of finite elements increases the flexibility of generating finite element decompositions substantially and is sometimes the only way to get a clear decomposition... KW - Finite-Elemente-Methode KW - Physikalisches Verfahren Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2524 ER - TY - CHAP A1 - Berger, Hans A1 - Graeff-Weinberg, K. T1 - FEM-Detailuntersuchungen an Tragwerken unter Einsatz von pNh-Übergangselementen N2 - Detailuntersuchungen an Tragwerken führen bei FE-Berechnungen immer wieder auf das Problem einer geeigneten Netzgestaltung. Während in weiten Bereichen ein grobes Netz ausreicht, muß an kritischen Stellen ein sehr feines Netz gewählt werden, um gerade dort hinreichend genaue Ergebnisse zu erhalten. Bei der Realisierung lokaler Netzverdichtungen stellt die Gestaltung des Übergangs vom groben zum feinen Netz das Hauptproblem dar. Im Beitrag wird hierzu eine Familie von FE-Übergangselementen vorgestellt, mit denen sich eine voll-kompatible Kopplung von wenigen großen Elementen mit vielen kleinen Elementen bereits über nur eine Stufe erzielen läßt. Diese neu entwickelten sogenannten pNh-Elemente ermöglichen an einer oder mehreren Seiten den Anschluß von N kleineren Elementen (Elementseiten für h-Verfeinerung). Das wird durch N stückweise definierte Ansatzfunktionen an den entsprechenden Seiten erreicht, wobei die Teilung nicht äquidistant sein braucht. Darüber hinaus ist es möglich, Elemente unterschiedlichen Polynomgrades p an den Standardseiten und den Verfeinerungsseiten anzuschließen. Der praktische Einsatz der Übergangselemente setzt geeignete automatische oder halbautomatische Netzgeneratoren voraus, die diese Elemente einbeziehen. Im Rahmen einer substrukturorientierten Modellierung läßt sich dies besonders günstig realisieren. Im Beitrag wird gezeigt, wie durch Zerlegung des Gesamtmodells in Bereiche mit grobem Netz, mit Übergangsnetz und mit feinem Netz, eine effektive Generierung der Netzverdichtungen zu erreichen ist. An einem praktischen Beispiel aus dem Bauingenieurwesen werden die Vorteile des vorgestellten Übergangselementkonzeptes umfassend demonstriert. KW - Tragwerk KW - Modellierung KW - Finite-Elemente-Methode Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-4267 ER - TY - CHAP A1 - Tzanev, D. T1 - Entwurf eines objektorientierten Modells zur Analyse von Schalentragwerken N2 - In der vorliegenden Arbeit werden dickwandige Schalentragwerke unter statischen Belastungen betrachtet. Die Schale besteht aus verschiedenen Zonen und in jeder Zone wird die Schalenmittelflaeche mittels eines eigenen Geometriegleichungssystems definiert. Das Verzerrungsfeld hat allen 6 unabhaengigen Komponenten unter der Annahme, dass die Querschnittsfasern, die normal zu der Mittelflaeche der unbelasteten Schale sind, geradelinig bleiben. Ein dreidimensionales isoparametrisches finites Element wird vorgeschlagen. Die Berechnung wird mit der Hilfe der Makroelemententechnik durchgefuehrt. In der Arbeit werden die wesentliche Parameter der Schalengeometrie, sowie auch entsprechendes Anteil von Klassen des konstruktiven Modells, definiert. Ein konstruktives Informationsmodell und ein FEM-Informationsmodell, werden entwickelt. Die Informationsverbindungen zwischen den beiden Modellen werden definiert. Diese objektorientierten Modelle werden in Programmiersprache Microsoft Visual C++ v.4.0 unter Windows 95 implementiert. Als numerisches Beispiel wird ein Bogenmauertragwerk betrachtet. KW - Bogenstaumauer KW - Schale KW - Dickwandiges Bauelement KW - Dreidimensionales Modell KW - Finite-Elemente-Methode Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-4397 ER - TY - JOUR A1 - Kwak, Hyo-Gyoung A1 - Kim, Jin-Kook T1 - Efficient Shoring System in RC Frame Structures N2 - In this paper, systematic analyses for the shoring systems installed to support the applied loads during construction are performed on the basis of the numerical approach. On the basis of a rigorous time-dependent analysis, structural behaviors of reinforced concrete (RC) frame structures according to the changes in design variables such as the types of shoring systems, shore stiffness and shore spacing are analyzed and discussed. The time-dependent deformations of concrete such as creep and shrinkage and construction sequences of frame structures are also taken into account to minimize the structural instability and to reach to an improved design of shoring system because these effects may increase the axial forces delivered to the shores. In advance, the influence of the column shortening effect, generally mentioned in a tall building structure, is analyzed. From many parametric studies, it has been finally concluded that the most effective shoring system in RC frame structures is 2S1R (two shores and one reshore) regardless of the changes in design variables. KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Skelettbau KW - Construction Sequence KW - Shoring System KW - Shore Stiffness KW - Shore Spacing Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2511 ER - TY - CHAP A1 - Gabbert, U. A1 - Grochla, J. A1 - Köppe, H. T1 - Dynamic-explicit finite element simulation of complex problems in civil engineering by parallel computing N2 - The paper deals with the simulation of the non-linear and time dependent behaviour of complex structures in engineering. Such simulations have to provide high accuracy in the prediction of deformations and stability, by taking into account the long term influences of the non-linear behaviour of the material as well as the large deformation and contact conditions. The limiting factors of the computer simulation are the computer run time and the memory requirement during solving large scale problems. To overcome these problems we use a dynamic-explicit time integration procedure for the solution of the semi-discrete equations of motion, which is very suited for parallel processing. In the paper at first we give a brief review of the theoretical background of the mechanical modelling and the dynamic-explicit technique for the solution of the semi-discrete equations of motion. Then the concept of parallel processing will be discussed . A test example concludes the paper. KW - Tragwerk KW - Nichtlineares Phänomen KW - Zeitabhängigkeit KW - Finite-Elemente-Methode Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-4259 ER - TY - CHAP A1 - Burghardt, Michael A1 - Meißner, Udo F. T1 - Dreidimensionale Finite-Element-Baugrundmodelle für Ingeniuerprobleme N2 - Bei komplexen Gründungskonstruktionen sind Planungsfehler durch eine konsistente Modellierung vermeidbar. Manuelle Berechnungsmethoden ermöglichen im allgemeinen ein dreidimensionales Vorgehen nicht. Numerische Berechnungsmethoden, wie z.B. die Finite-Element-Methode, sind ein optimales Werkzeug zur ganzheitlichen Simulation des Problems. Die für die Finite-Element-Analyse notwendige Diskretisierung komplexer Bau- grundstrukturen ist manuell nicht zu bewältigen. Der vorliegende Beitrag zeigt wie ein Finite-Element-Modell automatisch aus einem geotechnischen Modell unter Berücksichtigung der spezifischen Anforderungen der Baugrund-Tragwerk-Struktur und des Bauablaufes erzeugt werden kann. Hierbei wird die Berücksichtigung der geometrischen und der mechanischen Besonderheiten bei der Netzgenerierung dargestellt. KW - Baugrund KW - Mathematisches Modell KW - Dreidimensionales Modell KW - Finite-Elemente-Methode Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5750 ER - TY - CHAP A1 - Zolotov, Alexander B. A1 - Akimov, Pavel T1 - Discrete-continual Finite Element Method of Analysis for Three-dimensional Curvilinear Structures N2 - This paper is devoted to discrete-continual finite element method (DCFEM) of analysis for three-dimensional curvilinear structures. Operational and variational formulations of the problem in the ring coordinate system are presented. The discrete-continual design model for structures with constant physical and geometrical parameters in longitudinal direction is offered on the basis of so-called curvilinear discrete-continual finite elements. Element coordinate system, approximation of nodal unknowns, construction of element nodal load vector are under consideration. Element system of differential equations is formulated with use of special generalized block-structured stiffness matrix of discrete-continual finite element. Local differential relations are formulated. Resultant multipoint boundary problem for system of ordinary differential equations is given. Method of analytical solution of multipoint boundary problems in structural analysis is offered as well. Its major peculiarities include universality, computer-oriented algorithm involving theory of distributions, computational stability, optimal conditionality of resultant systems, partial Jordan decomposition of matrix of coefficients, eliminating necessity of calculation of root vectors. Brief information concerning developed software is provided. KW - Raumtragwerk KW - Kreis KW - Finite-Elemente-Methode Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-3848 ER - TY - CHAP A1 - Ducke, M. A1 - Eckstein, U. A1 - Montag, U. T1 - Die Eisenbahnbrücken des Lehrter Bahnhofs in Berlin - Ein ganzheitliches FE-Berechnungskonzept N2 - Der Komplexität moderner Brückenbauwerke scheinen die verwendeten Berechungsmodelle oft nicht angemessen. Tragwerksberechnungen basieren in vielen Fällen noch auf der Vorgehensweise, das Brückenbauwerk in Einzelbauteile zu zerlegen und mit unterschiedlichen Teilmodellen zu behandeln. Das erscheint, auch vor dem Hintergrund ständig wachsender Rechnerleistung, nicht mehr zeitgemäß. Dies gilt zum Beispiel auch für die gängige Praxis, flächenhafte Brückenüberbauten mit Balkenmodellen zu berechnen. Der vorliegende Beitrag stellt ein ganzheitliches Berech-nungskonzept vor, welches auf der Basis eines einzigen FE-Modells die Berechnung des Gesamtbauwerks erlaubt. Damit wird für alle Bauteile neben der Zustandsgrößenberechnung auch die Bemessung von Stahl- und Spannbetonbauteilen bis hin zu Nachweisen wie zur Beschränkung der Rissbreite geführt. Die Anwendung dieses Berechnungskonzeptes wird am Beispiel der Eisenbahnüberführung des neuen Lehrter Bahn-hofs in Berlin gezeigt. Das verwendete FE-Modell umfasst Baugrund, Fundamente, Stahl- bzw. Gußstahlunterkonstruktion sowie den Stahl- bzw. Spannbetonüberbau. Besonderheiten sind unter anderem die Modellierung des plattenbalkenartigen Überbaus durch exzentrische, vorspannbare Schalenelemente und das getrennte Vorhalten von tragwerks- und lastbezogenen Eingabefiles. Damit gelingt die sequentielle Erfassung unterschiedlicher Bettungsmoduli zur Simulation statischer und dynamischer Beanspruchungen, die Berücksichtigung des Anspannens und der Interaktion zwischen vorgespannten Stahlverbänden zur Aufnahme von Horizontallasten sowie die Berücksichtigung unterschiedlicher statischer Systeme bei der Herstellung des Spannbetonüberbaus. KW - Berlin KW - Eisenbahnbrücke KW - Berechnung KW - Finite-Elemente-Methode KW - Lehrter Bahnhof KW - Gesamtbauwerk Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5812 ER - TY - JOUR A1 - Pick, Tobias A1 - Heimsund, Bjoern-Ove A1 - Milbradt, Peter T1 - Development and Analysis of Sparse Matrix Concepts for Finite Element Approximation on general Cells N2 - In engineering and computing, the finite element approximation is one of the most well-known computational solution techniques. It is a great tool to find solutions for mechanic, fluid mechanic and ecological problems. Whoever works with the finite element method will need to solve a large system of linear equations. There are different ways to find a solution. One way is to use a matrix decomposition technique such as LU or QR. The other possibility is to use an iterative solution algorithm like Conjugate Gradients, Gauß-Seidel, Multigrid Methods, etc. This paper will focus on iterative solvers and the needed storage techniques... KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Bandmatrix Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2500 ER - TY - JOUR A1 - Êirinhevsky, V. V. A1 - Dîkhnyak, B. M. A1 - Êirichevsky, R. V. A1 - Êîzub, Y. G. T1 - Determination of the Temperature of Dissipative Warming and Parameters of Fracture in Elastomers with using of Singular Finite Elements N2 - For modeling of singular fields of stresses and deformations in elasters with a crack is offered to use of three-dimesional a special finite element. Weak compessible of elasters is taken into account on the basis of threefold approximation of fields of displacements, deformations and function of volume change. At intensive cyclic loading of the elastomer constructions with a crack it is necessary to take into account warming and large deformations at the crack top. The stress-deformed state elasters with a crack is determined from the decision of a nonlinear problem by a modified method Newton-Kantorovich. Account stress intensity factors for a rectangular plate with a various arrangement of a through crack is executed. Process of development of a surface crack and dissipative warming in prismatic a element of shift is investigated. KW - Elastomer KW - Temperatur KW - Finite-Elemente-Methode Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5471 ER - TY - JOUR A1 - Kaklauskas, Gintaris A1 - Cervenka, Vladimir A1 - Cervenka, Jan T1 - Deflection Calculation of RC Beams: Finite Element Software versus Design Code Methods N2 - The paper investigates accuracy of deflection predictions made by the finite element package ATENA and design code methods ACI and EC2. Deflections have been calculated for a large number of experimental reinforced concrete beams reported by three investigators. Statistical parameters have been established for each of the technique at different load levels, separately for the beams with small and moderate reinforcement ratio. KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Balken Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2498 ER - TY - JOUR A1 - Melnikov, B. E. A1 - Semenov, Artem T1 - Application of Multimodel Method of Elasto-Plastic Analysis for the Multilevel Computation of Structures N2 - Creation of hierarchical sequence of the plastic and viscoplastic models according to different levels of structure approximations is considered. Developed strategy of multimodel analysis, which consists of creation of the inelastic models library, determination of selection criteria system and caring out of multivariant sequential clarifying computations, is described. Application of the multimodel approach in numerical computations has demonstrated possibility of reliable prediction of stress-strain response under wide variety of combined nonproportional loading. KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Elastoplastizität Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2487 ER - TY - JOUR A1 - Most, Thomas A1 - Eckardt, Stefan T1 - Application of a hybrid parallelization technique to accelerate the numerical simulation of nonlinear mechanical problems N2 - This paper presents the combination of two different parallelization environments, OpenMP and MPI, in one numerical simulation tool. The computation of the system matrices and vectors is parallelized with OpenMP and the solution of the system of equations is done with the MPIbased solver MUMPS. The efficiency of both algorithms is shown on several linear and nonlinear examples using the Finite Element Method and a meshless discretization technique. KW - Framework KW - API KW - Parallelverarbeitung KW - Finite-Elemente-Methode Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2599 ER - TY - CHAP A1 - Daniunas, A. A1 - Komka, A. A1 - Werner, F. T1 - ANALYSIS AND DETERMINATION OF STRENGTH IN PLASTIC STAGE OF FREE FORM STEEL SHAPES N2 - The steel structure design codes require to check up the member strength when evaluating plastic deformations. The model of perfectly plastic material is accepted. The strength criteria for simple cross-sections (I section, etc.) of steel members are given in design codes. The analytical strength criteria for steel cross-sections and numerical approaches based on stepwise procedure are investigated in many articles. Another way for checking the carrying capacity of cross-sections is the use of methods that are applied for defining strain-deformed state of elastic perfectly plastic systems. In this paper non-iterative methods are suggested for checking strength of cross-sections. Carrying capacity of cross section is verified according to extremum principle of plastic fail under monotonically loading and the strain-deformed state of cross-section is defined according to extremum energy principals of elastic potential of residual stresses and complementary work of residual displacements. The mathematical expressions of these principals for discrete cross-section are formulated as problems of convex mathematical programming. The cross-section of steel member using finite element method is divided into free form plane elements. The constant distribution of stresses along the finite element is accepted. The relationships of finite elements for static formulation of the problem are formed so, that kinematics formulation relationships could be obtained in a formal way using the theory of duality. Numerical examples of determination of cross-section strength, composition of interactive curves and composition of moment-curvature curves for different axial force levels are presented. KW - Stahlkonstruktion KW - Plastische Deformation KW - Mathematisches Modell KW - Finite-Elemente-Methode Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5803 ER - TY - JOUR A1 - Lee, Kangkun A1 - Lee, Kijang T1 - Additional bending moment for shear-lag phenomenon in tube structures N2 - Framed-tube system with multiple internal tubes is analysed using an orthotropic box beam analogy approach in which each tube is individually modelled by a box beam that accounts for the flexural and shear deformations, as well as the shear-lag effects. A simple numerical modeling technique is proposed for estimating the shear-lag phenomenon in tube structures with multiple internal tubes. The proposed method idealizes the framed-tube structures with multiple internal tubes as equivalent multiple tubes, each composed of four equivalent orthotropic plate panels. The numerical analysis is based on the minimum potential energy principle in conjunction with the variational approach. The shear-lag phenomenon of such structures is studied taking into account the additional bending moments in the tubes. A detailed work is carried out through the numerical analysis of the additional bending moment. The moment factor is further introduced to identify the shear lag phenomenon along with the additional moment. KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Hochhaus Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2472 ER - TY - CHAP A1 - Skrinar, Matjaz T1 - A simple FEM Beam Element with an Arbitrary Number of Cracks N2 - To fulfil safety requirements the changes in the static and/or dynamic behaviour of the structure must be analysed with great care. These changes are often caused by local reduction of the stiffness of the structure caused by the irregularities in the structure, as for example cracks. In simple structures such analysis can be performed directly, by solving equations of motion, but for more complex structures a different approach, usually numerical, must be applied. The problem of crack implementation into the structure behaviour has been studied by many authors who have usually modelled the crack as a massless rotational spring of suitable stiffness placed at the beam at the location where the crack occurs. Recently, the numerical procedure for the computation of the stiffness matrix for a beam element with a single transverse crack has been replaced with the element stiffness matrix written in fully symbolic form. A detailed comparison of the results obtained by using 200 2D finite elements with those obtained with a single cracked beam element has confirmed the usefulness of such element. KW - Finite-Elemente-Methode KW - Rissbildung Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-4287 ER - TY - JOUR A1 - Mironov, Vadim A1 - Pahl, Peter Jan T1 - A Prismatic Finite Element for Accurate Arch Dam Analysis N2 - The displacements and stresses in arch dams and their abutments are frequently determined with 20-node brick elements. The elements are distorted near the contact plane between the wall and the abutment. A cantilever beam testbed has been developed to investigate the consequences of this distortion. It is shown that the deterioration of the accuracy in the computed stresses is significant. A compatible 18-node wedge element with linear stress variation is developed as an alternative to the brick element. The shape of this element type is readily adapted to the shape of the contact plane. It is shown that the accuracy of the computed stresses in the vicinity of the contact plane is improved significantly by the use of wedge elements. KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Dammbau Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2467 ER - TY - CHAP A1 - Montag, U. T1 - A New Efficient Concept for Elasto-plastic Simulations of Shell Responses N2 - For the analysis of arbitrary, by Finite Elements discretized shell structures, an efficient numerical simulation strategy with quadratic convergence including geometrically and physically nonlinear effects will be presented. In the beginning, a Finite-Rotation shell theory allowing constant shear deformations across the shell thickness is given in an isoparametric formulation. The assumed-strain concept enables the derivation of a locking-free finite element. The Layered Approach will be applied to ensure a sufficiently precise prediction of the propagation of plastic zones even throughout the shell thickness. The Riks-Wempner-Wessels global iteration scheme will be enhanced by a Line-Search procedure to ensure the tracing of nonlinear deformation paths with rather great load steps even in the post-peak range. The elastic-plastic material model includes isotropic hardening. A new Operator-Split return algorithm ensures considerably exact solution of the initial-value problem even for greater load steps. The combination with consistently linearized constitutive equations ensures quadratic convergence in a close neighbourhood to the exact solution. Finally, several examples will demonstrate accuracy and numerical efficiency of the developed algorithm. KW - Schale KW - Elastoplastizität KW - Finite-Elemente-Methode Y1 - 1997 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-4364 ER - TY - CHAP A1 - Häfner, Stefan A1 - Eckardt, Stefan A1 - Könke, Carsten T1 - A geometrical inclusion-matrix model for the finite element analysis of concrete at multiple scales N2 - This paper introduces a method to generate adequate inclusion-matrix geometries of concrete in two and three dimensions, which are independent of any specific numerical discretization. The article starts with an analysis on shapes of natural aggregates and discusses corresponding mathematical realizations. As a first prototype a two-dimensional generation of a mesoscale model is introduced. Particle size distribution functions are analysed and prepared for simulating an adequate three-dimensional representation of the aggregates within a concrete structure. A sample geometry of a three-dimensional test cube is generated and the finite element analysis of its heterogeneous geometry by a uniform mesh is presented. Concluding, aspects of a multiscale analysis are discussed and possible enhancements are proposed. KW - Beton KW - Dreidimensionales Modell KW - Finite-Elemente-Methode Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-3018 ER - TY - CHAP A1 - Brehm, Maik A1 - Most, Thomas T1 - A Four-Node Plane EAS-Element for Stochastic Nonlinear Materials N2 - Iso-parametric finite elements with linear shape functions show in general a too stiff element behavior, called locking. By the investigation of structural parts under bending loading the so-called shear locking appears, because these elements can not reproduce pure bending modes. Many studies dealt with the locking problem and a number of methods to avoid the undesirable effects have been developed. Two well known methods are the >Assumed Natural Strain< (ANS) method and the >Enhanced Assumed Strain< (EAS) method. In this study the EAS method is applied to a four-node plane element with four EAS-parameters. The paper will describe the well-known linear formulation, its extension to nonlinear materials and the modeling of material uncertainties with random fields. For nonlinear material behavior the EAS parameters can not be determined directly. Here the problem is solved by using an internal iteration at the element level, which is much more efficient and stable than the determination via a global iteration. To verify the deterministic element behavior the results of common test examples are presented for linear and nonlinear materials. The modeling of material uncertainties is done by point-discretized random fields. To show the applicability of the element for stochastic finite element calculations Latin Hypercube Sampling was applied to investigate the stochastic hardening behavior of a cantilever beam with nonlinear material. The enhanced linear element can be applied as an alternative to higher-order finite elements where more nodes are necessary. The presented element formulation can be used in a similar manner to improve stochastic linear solid elements. KW - Nichtlineare Mechanik KW - Finite-Elemente-Methode KW - Zufallsvariable Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2825 ER - TY - JOUR A1 - Noh, Jung-Hwi A1 - Park, Jong-Heon T1 - A Calculation of Initial Cable Force for Ko-Ha Grand Bridge N2 - The primary objective of initial shape analysis of a cable stayed bridge is to calculate initial installation cable tension forces and to evaluate fabrication camber of main span and pylon providing the final longitudinal profile of the bridge at the end of construction. In addition, the initial cable forces depending on the alternation of the bridge’s shape can be obtained from the analysis, and will be used to provide construction safety during construction. In this research, we conducted numerical experiments for initial shape of Ko-ha bridge, which will be constructed in the near future, using three different typical methods such as continuous beam method, linear truss method, and IIMF (Introducing Initial Member Force) method KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Hängebrücke KW - cable stayed bridge KW - cable force KW - initial shape KW - initial equilibrium state Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2459 ER -