Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen
OPUS4-3471 Konferenzveröffentlichung Könke, Carsten; Eckardt, Stefan; Häfner, Stefan Spatial and temporal multiscale simulations of damage processes for concrete Spatial and temporal multiscale simulations of damage processes for concrete Institut für Strukturmechanik
OPUS4-3506 Konferenzveröffentlichung Eckardt, Stefan; Häfner, Stefan; Könke, Carsten Simulation of the fracture behaviour of concrete using continuum damage models at the mesoscale Simulation of the fracture behaviour of concrete using continuum damage models at the mesoscale Institut für Strukturmechanik
OPUS4-3494 Konferenzveröffentlichung Könke, Carsten; Eckardt, Stefan; Häfner, Stefan; Luther, Torsten; Unger, Jörg F. Schädigungs- und Verbundmodellierung für Stahlbetontragwerke Schädigungs- und Verbundmodellierung für Stahlbetontragwerke Institut für Strukturmechanik
OPUS4-3404 Wissenschaftlicher Artikel Könke, Carsten; Eckardt, Stefan; Häfner, Stefan; Luther, Torsten; Unger, Jörg F. Multiscale simulation methods in damage prediction of brittle and ductile materials Multiscale simulation methods in damage prediction of brittle and ductile materials 19 International Journal for Multiscale Computational Engineering 17 36 Institut für Strukturmechanik
OPUS4-3466 Konferenzveröffentlichung Häfner, Stefan; Kessel, Marco; Könke, Carsten Multiphase B-spline finite elements of variable order in the mechanical analysis of heterogeneous solids Multiphase B-spline finite elements of variable order in the mechanical analysis of heterogeneous solids Institut für Strukturmechanik
OPUS4-2964 Konferenzveröffentlichung Häfner, Stefan; Kessel, Marco; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten MULTIPHASE B-SPLINE FINITE ELEMENTS OF VARIABLE ORDER IN THE MECHANICAL ANALYSIS OF HETEROGENEOUS SOLIDS Advanced finite elements are proposed for the mechanical analysis of heterogeneous materials. The approximation quality of these finite elements can be controlled by a variable order of B-spline shape functions. An element-based formulation is developed such that the finite element problem can iteratively be solved without storing a global stiffness matrix. This memory saving allows for an essential increase of problem size. The heterogeneous material is modelled by projection onto a uniform, orthogonal grid of elements. Conventional, strictly grid-based finite element models show severe oscillating defects in the stress solutions at material interfaces. This problem is cured by the extension to multiphase finite elements. This concept enables to define a heterogeneous material distribution within the finite element. This is possible by a variable number of integration points to each of which individual material properties can be assigned. Based on an interpolation of material properties at nodes and further smooth interpolation within the finite elements, a continuous material function is established. With both, continuous B-spline shape function and continuous material function, also the stress solution will be continuous in the domain. The inaccuracy implied by the continuous material field is by far less defective than the prior oscillating behaviour of stresses. One- and two-dimensional numerical examples are presented. 37 urn:nbn:de:gbv:wim2-20170327-29643 10.25643/bauhaus-universitaet.2964 Institut für Strukturmechanik
OPUS4-3467 Konferenzveröffentlichung Häfner, Stefan; Könke, Carsten Multigrid preconditioned conjugate gradient method in the mechanical analysis of heterogeneous solids Multigrid preconditioned conjugate gradient method in the mechanical analysis of heterogeneous solids Institut für Strukturmechanik
OPUS4-2962 Konferenzveröffentlichung Häfner, Stefan; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten MULTIGRID PRECONDITIONED CONJUGATE GRADIENT METHOD IN THE MECHANICAL ANALYSIS OF HETEROGENEOUS SOLIDS A fast solver method called the multigrid preconditioned conjugate gradient method is proposed for the mechanical analysis of heterogeneous materials on the mesoscale. Even small samples of a heterogeneous material such as concrete show a complex geometry of different phases. These materials can be modelled by projection onto a uniform, orthogonal grid of elements. As one major problem the possible resolution of the concrete specimen is generally restricted due to (a) computation times and even more critical (b) memory demand. Iterative solvers can be based on a local element-based formulation while orthogonal grids consist of geometrical identical elements. The element-based formulation is short and transparent, and therefore efficient in implementation. A variation of the material properties in elements or integration points is possible. The multigrid method is a fast iterative solver method, where ideally the computational effort only increases linear with problem size. This is an optimal property which is almost reached in the implementation presented here. In fact no other method is known which scales better than linear. Therefore the multigrid method gains in importance the larger the problem becomes. But for heterogeneous models with very large ratios of Young's moduli the multigrid method considerably slows down by a constant factor. Such large ratios occur in certain heterogeneous solids, as well as in the damage analysis of solids. As solution to this problem the multigrid preconditioned conjugate gradient method is proposed. A benchmark highlights the multigrid preconditioned conjugate gradient method as the method of choice for very large ratio's of Young's modulus. A proposed modified multigrid cycle shows good results, in the application as stand-alone solver or as preconditioner. 29 urn:nbn:de:gbv:wim2-20170327-29626 10.25643/bauhaus-universitaet.2962 Institut für Strukturmechanik
OPUS4-3460 Wissenschaftlicher Artikel Häfner, Stefan; Eckardt, Stefan; Luther, Torsten; Könke, Carsten Mesoscale modeling of concrete: Geometry and numerics Mesoscale modeling of concrete: Geometry and numerics 11 Computers and Structures 450 461 Institut für Strukturmechanik
OPUS4-2848 Konferenzveröffentlichung Häfner, Stefan; Vogel, Frank; Könke, Carsten Gürlebeck, Klaus; Könke, Carsten FINITE ELEMENT ANALYSIS OF TORSION FOR ARBITRARY CROSS-SECTIONS The present article proposes an alternative way to compute the torsional stiffness based on three-dimensional continuum mechanics instead of applying a specific theory of torsion. A thin, representative beam slice is discretized by solid finite elements. Adequate boundary conditions and coupling conditions are integrated into the numerical model to obtain a proper answer on the torsion behaviour, thus on shear center, shear stress and torsional stiffness. This finite element approach only includes general assumptions of beam torsion which are independent of cross-section geometry. These assumptions essentially are: no in-plane deformation, constant torsion and free warping. Thus it is possible to achieve numerical solutions of high accuracy for arbitrary cross-sections. Due to the direct link to three-dimensional continuum mechanics, it is possible to extend the range of torsion analysis to sections which are composed of different materials or even to heterogeneous beams on a high scale of resolution. A brief study follows to validate the implementation and results are compared to analytical solutions. 11 urn:nbn:de:gbv:wim2-20170314-28483 10.25643/bauhaus-universitaet.2848 Institut für Strukturmechanik