@inproceedings{BrehmMost2003,
  author    = {Brehm, Maik and Most, Thomas},
  title     = {A Four-Node Plane EAS-Element for Stochastic Nonlinear Materials},
  doi       = {10.25643/bauhaus-universitaet.282},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-2825},
  year      = {2003},
  abstract  = {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.},
  subject      = {Nichtlineare Mechanik},
  language  = {en}
}
@inproceedings{HaefnerEckardtKoenke2003,
  author    = {H{\"a}fner, Stefan and Eckardt, Stefan and K{\"o}nke, Carsten},
  title     = {A geometrical inclusion-matrix model for the finite element analysis of concrete at multiple scales},
  doi       = {10.25643/bauhaus-universitaet.301},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-3018},
  year      = {2003},
  abstract  = {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.},
  subject      = {Beton},
  language  = {en}
}
@inproceedings{Montag1997,
  author    = {Montag, U.},
  title     = {A New Efficient Concept for Elasto-plastic Simulations of Shell Responses},
  doi       = {10.25643/bauhaus-universitaet.436},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-4364},
  year      = {1997},
  abstract  = {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.},
  subject      = {Schale},
  language  = {en}
}
@inproceedings{Skrinar1997,
  author    = {Skrinar, Matjaz},
  title     = {A simple FEM Beam Element with an Arbitrary Number of Cracks},
  doi       = {10.25643/bauhaus-universitaet.428},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-4287},
  year      = {1997},
  abstract  = {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.},
  subject      = {Finite-Elemente-Methode},
  language  = {en}
}
@inproceedings{DaniunasKomkaWerner2000,
  author    = {Daniunas, A. and Komka, A. and Werner, F.},
  title     = {ANALYSIS AND DETERMINATION OF STRENGTH IN PLASTIC STAGE OF FREE FORM STEEL SHAPES},
  doi       = {10.25643/bauhaus-universitaet.580},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-5803},
  year      = {2000},
  abstract  = {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.},
  subject      = {Stahlkonstruktion},
  language  = {en}
}
@inproceedings{DuckeEcksteinMontag2000,
  author    = {Ducke, M. and Eckstein, U. and Montag, U.},
  title     = {Die Eisenbahnbr{\"u}cken des Lehrter Bahnhofs in Berlin - Ein ganzheitliches FE-Berechnungskonzept},
  doi       = {10.25643/bauhaus-universitaet.581},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-5812},
  year      = {2000},
  abstract  = {Der Komplexit{\"a}t moderner Br{\"u}ckenbauwerke scheinen die verwendeten Berechungsmodelle oft nicht angemessen. Tragwerksberechnungen basieren in vielen F{\"a}llen noch auf der Vorgehensweise, das Br{\"u}ckenbauwerk in Einzelbauteile zu zerlegen und mit unterschiedlichen Teilmodellen zu behandeln. Das erscheint, auch vor dem Hintergrund st{\"a}ndig wachsender Rechnerleistung, nicht mehr zeitgem{\"a}ß. Dies gilt zum Beispiel auch f{\"u}r die g{\"a}ngige Praxis, fl{\"a}chenhafte Br{\"u}cken{\"u}berbauten 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 f{\"u}r alle Bauteile neben der Zustandsgr{\"o}ßenberechnung auch die Bemessung von Stahl- und Spannbetonbauteilen bis hin zu Nachweisen wie zur Beschr{\"a}nkung der Rissbreite gef{\"u}hrt. Die Anwendung dieses Berechnungskonzeptes wird am Beispiel der Eisenbahn{\"u}berf{\"u}hrung des neuen Lehrter Bahn-hofs in Berlin gezeigt. Das verwendete FE-Modell umfasst Baugrund, Fundamente, Stahl- bzw. Gußstahlunterkonstruktion sowie den Stahl- bzw. Spannbeton{\"u}berbau. Besonderheiten sind unter anderem die Modellierung des plattenbalkenartigen {\"U}berbaus 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 Ber{\"u}cksichtigung des Anspannens und der Interaktion zwischen vorgespannten Stahlverb{\"a}nden zur Aufnahme von Horizontallasten sowie die Ber{\"u}cksichtigung unterschiedlicher statischer Systeme bei der Herstellung des Spannbeton{\"u}berbaus.},
  subject      = {Berlin},
  language  = {de}
}
@inproceedings{ZolotovAkimov2003,
  author    = {Zolotov, Alexander B. and Akimov, Pavel},
  title     = {Discrete-continual Finite Element Method of Analysis for Three-dimensional Curvilinear Structures},
  doi       = {10.25643/bauhaus-universitaet.384},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-3848},
  year      = {2003},
  abstract  = {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.},
  subject      = {Raumtragwerk},
  language  = {de}
}
@inproceedings{BurghardtMeissner2000,
  author    = {Burghardt, Michael and Meißner, Udo F.},
  title     = {Dreidimensionale Finite-Element-Baugrundmodelle f{\"u}r Ingeniuerprobleme},
  doi       = {10.25643/bauhaus-universitaet.575},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-5750},
  year      = {2000},
  abstract  = {Bei komplexen Gr{\"u}ndungskonstruktionen sind Planungsfehler durch eine konsistente Modellierung vermeidbar. Manuelle Berechnungsmethoden erm{\"o}glichen 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 f{\"u}r die Finite-Element-Analyse notwendige Diskretisierung komplexer Bau- grundstrukturen ist manuell nicht zu bew{\"a}ltigen. Der vorliegende Beitrag zeigt wie ein Finite-Element-Modell automatisch aus einem geotechnischen Modell unter Ber{\"u}cksichtigung der spezifischen Anforderungen der Baugrund-Tragwerk-Struktur und des Bauablaufes erzeugt werden kann. Hierbei wird die Ber{\"u}cksichtigung der geometrischen und der mechanischen Besonderheiten bei der Netzgenerierung dargestellt.},
  subject      = {Baugrund},
  language  = {de}
}
@inproceedings{GabbertGrochlaKoeppe1997,
  author    = {Gabbert, U. and Grochla, J. and K{\"o}ppe, H.},
  title     = {Dynamic-explicit finite element simulation of complex problems in civil engineering by parallel computing},
  doi       = {10.25643/bauhaus-universitaet.425},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-4259},
  year      = {1997},
  abstract  = {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.},
  subject      = {Tragwerk},
  language  = {en}
}
@inproceedings{Tzanev1997,
  author    = {Tzanev, D.},
  title     = {Entwurf eines objektorientierten Modells zur Analyse von Schalentragwerken},
  doi       = {10.25643/bauhaus-universitaet.439},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-4397},
  year      = {1997},
  abstract  = {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.},
  subject      = {Bogenstaumauer},
  language  = {de}
}