Numerical Implementation (numerical + implementation)

Distribution by Scientific Domains


Selected Abstracts


Numerical implementation of Aristov,Pukhnachev's formulation for axisymmetric viscous incompressible flows

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2010
N. P. Moshkin
Abstract In the present work a finite-difference technique is developed for the implementation of a new method proposed by Aristov and Pukhnachev (Doklady Phys. 2004; 49(2):112,115) for modeling of the axisymmetric viscous incompressible fluid flows. A new function is introduced that is related to the pressure and a system similar to the vorticity/stream function formulation is derived for the cross-flow. This system is coupled to an equation for the azimuthal velocity component. The scheme and the algorithm treat the equations for the cross-flow as an inextricably coupled system, which allows one to satisfy two conditions for the stream function with no condition on the auxiliary function. The issue of singularity of the matrix is tackled by adding a small parameter in the boundary conditions. The scheme is thoroughly validated on grids with different resolutions. The new numerical tool is applied to the Taylor flow between concentric rotating cylinders when the upper and lower lids are allowed to rotate independently from the inner cylinder, while the outer cylinder is held at rest. The phenomenology of this flow is adequately represented by the numerical model, including the hysteresis that takes place near certain specific values of the Reynolds number. Thus, the present results can be construed to demonstrate the viability of the new model. The success can be attributed to the adequate physical nature of the auxiliary function. The proposed technique can be used in the future for in-depth investigations of the bifurcation phenomena in rotating flows. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Numerical implementation of the Crank,Nicolson/Adams,Bashforth scheme for the time-dependent Navier,Stokes equations

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2010
Yinnian He
Abstract This article considers numerical implementation of the Crank,Nicolson/Adams,Bashforth scheme for the two-dimensional non-stationary Navier,Stokes equations. A finite element method is applied for the spatial approximation of the velocity and pressure. The time discretization is based on the Crank,Nicolson scheme for the linear term and the explicit Adams,Bashforth scheme for the nonlinear term. Comparison with other methods, through a series of numerical experiments, shows that this method is almost unconditionally stable and convergent, i.e. stable and convergent when the time step is smaller than a given constant. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Spectral-element simulations of wave propagation in porous media

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2008
Christina Morency
SUMMARY We present a derivation of the equations describing wave propagation in porous media based upon an averaging technique which accommodates the transition from the microscopic to the macroscopic scale. We demonstrate that the governing macroscopic equations determined by Biot remain valid for media with gradients in porosity. In such media, the well-known expression for the change in porosity, or the change in the fluid content of the pores, acquires two extra terms involving the porosity gradient. One fundamental result of Biot's theory is the prediction of a second compressional wave, often referred to as ,type II' or ,Biot's slow compressional wave', in addition to the classical fast compressional and shear waves. We present a numerical implementation of the Biot equations for 2-D problems based upon the spectral-element method (SEM) that clearly illustrates the existence of these three types of waves as well as their interactions at discontinuities. As in the elastic and acoustic cases, poroelastic wave propagation based upon the SEM involves a diagonal mass matrix, which leads to explicit time integration schemes that are well suited to simulations on parallel computers. Effects associated with physical dispersion and attenuation and frequency-dependent viscous resistance are accommodated based upon a memory variable approach. We perform various benchmarks involving poroelastic wave propagation and acoustic,poroelastic and poroelastic,poroelastic discontinuities, and we discuss the boundary conditions used to deal with these discontinuities based upon domain decomposition. We show potential applications of the method related to wave propagation in compacted sediments, as one encounters in the petroleum industry, and to detect the seismic signature of buried landmines and unexploded ordnance. [source]


Elasto-plastic analysis of block structures through a homogenization method

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2010
G. de Felice
Abstract The paper describes the development and numerical implementation of a constitutive relationship for modeling the elasto-plastic behavior of block structures with periodic texture, regarded at a macroscopic scale as homogenized anisotropic media. The macroscopic model is shown to retain memory of the mechanical characteristics of the joints and of the shape of the blocks. The overall mechanical properties display anisotropy and singularities in the yield surface, arising from the discrete nature of the block structure and the geometrical arrangement of the units. The model is formulated in the framework of multi-surface plasticity. It is implemented in an finite element (FE) code by means of two different algorithms: an implicit return mapping scheme and a minimization algorithm directly derived from the Haar,Karman principle. The model is validated against analytical and experimental results: the comparison between the homogenized continuum and the original block assembly shows a good agreement in terms of ultimate inelastic behavior, when the size of the block is small as compared with that of the whole assembly. Copyright © 2009 John Wiley & Sons, Ltd. [source]


A numerical method for the study of shear band propagation in soft rocks

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2009
Marta Castelli
Abstract This paper investigates the possibility of interpreting progressive shear failure in hard soils and soft rocks as the result of shear propagation of a pre-existing natural defect. This is done through the application of the principles of fracture mechanics, a slip-weakening model (SWM) being used to simulate the non-linear zone at the tips of the discontinuity. A numerical implementation of the SWM in a computation method based on the boundary element technique of the displacement discontinuity method (DDM) is presented. The crack and the non-linear zone at the advancing tip are represented through a set of elements, where the displacement discontinuity (DD) in the tangential direction is determined on the basis of a friction law. A residual friction angle is assumed on the crack elements. Shear resistance decreases on elements in the non-linear zone from a peak value at the tip, which is characteristic of intact material, to the residual value. The simulation of a uniaxial compressive test in plane strain conditions is carried out to exemplify the numerical methodology. The results emphasize the role played by the critical DD on the mechanical behaviour of the specimen. A validation of the model is shown through the back analysis of some experimental observations. The results of this back analysis show that a non-linear fracture mechanics approach seems very promising to simulate experimental results, in particular with regards to the shear band evolution pattern. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Modelling strain localization in granular materials using micropolar theory: numerical implementation and verification

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 15 2006
Khalid A. Alshibli
Abstract Implementation and applications for a constitutive numerical model on F-75 silica sand, course silica sand and two sizes of glass beads compressed under plane strain conditions are presented in this work. The numerical model is used to predict the stress versus axial strain and volumetric strain versus axial strain relationships of those materials; moreover, comparisons between measured and predicted shear band thickness and inclination angles are discussed and the numerical results compare well with the experimental measurements. The numerical model is found to respond to the changes in confining pressure and the initial relative density of a given granular material. The mean particle size is used as an internal length scale. Increasing the confining pressure and the initial density is found to decrease the shear band thickness and increase the inclination angle. The micropolar or Cosserat theory is found to be effective in capturing strain localization in granular materials. The finite element formulations and the solution method for the boundary value problem in the updated Lagrangian frame (UP) are discussed in the companion paper. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Development of hyperplasticity models for soil mechanics

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2006
S. Likitlersuang
Abstract Hyperplasticity theory was developed by Collins and Houlsby (Proc. Roy. Soc. Lon. A 1997; 453:1975,2001) and Houlsby and Puzrin (Int. J. Plasticity 2000; 16(9):1017,1047). Further research has extended the method to continuous hyperplasticity, in which smooth transitions between elastic and plastic behaviour can be modelled. This paper illustrates a development of a new constitutive model for soils using hyperplasticity theory. The research begins with a simple one-dimensional elasticity model. This is extended in stages to an elasto-plastic model with a continuous internal function. The research aims to develop a soil model, which addresses some of the shortcomings of the modified cam-clay model, specifically the fact that it cannot model small strain stiffness, or the effects of immediate stress history. All expressions used are consistent with critical state soil mechanics terminology. Finally, a numerical implementation of the model using a rate-dependent algorithm is described. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Analysis of thick functionally graded plates by local integral equation method

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 8 2007
J. Sladek
Abstract Analysis of functionally graded plates under static and dynamic loads is presented by the meshless local Petrov,Galerkin (MLPG) method. Plate bending problem is described by Reissner,Mindlin theory. Both isotropic and orthotropic material properties are considered in the analysis. A weak formulation for the set of governing equations in the Reissner,Mindlin theory with a unit test function is transformed into local integral equations considered on local subdomains in the mean surface of the plate. Nodal points are randomly spread on this surface and each node is surrounded by a circular subdomain, rendering integrals which can be simply evaluated. The meshless approximation based on the moving least-squares (MLS) method is employed in the numerical implementation. Numerical results for simply supported and clamped plates are presented. Copyright © 2006 John Wiley & Sons, Ltd. [source]


On the residue calculus evaluation of the 3-D anisotropic elastic green's function

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2004
A.-V. Phan
Abstract An algorithm based upon the residue calculus for computing three-dimensional anisotropic elastic Green's function and its derivatives has been presented in Sales and Gray (Comput. Structures 1998; 69:247,254). It has been shown that the algorithm runs three to four times faster than the standard Wilson,Cruse interpolation scheme. However, the main concern of the Sales,Gray algorithm is its numerical instability that could lead to significant errors due to the existence of multiple poles of the residue. This paper proposes a remedy for the problem by adding the capability to evaluate the Green's function in case of multiple poles of the residue. Further, an improved numerical implementation based on the use of double-subscript-notation elastic constants in determining the Christoffel tensor is also at issue. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Symmetric Galerkin BEM for multi-connected bodies

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 11 2001
J. J. Pérez-Gavilán
In this paper, it is shown that the symmetric Galerkin boundary element formulation cannot be used in its standard form for multiple connected bodies. This is because the traction integral equation used for boundaries with Neuman boundary condition give non-unique solutions. While this fact is well known from the classical theory of integral equations, the problem has not been fully addressed in the literature related to symmetric Galerkin formulations. In this paper, the problem is reviewed and a general way to deal with it is proposed. The details of the numerical implementation are discussed and an example is solved to demonstrate the effectiveness of the proposed solution. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Geometry update driven by material forces for simulation of brittle crack growth in functionally graded materials

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2009
Rolf Mahnken
Abstract Functionally graded materials (FGMs) are advanced materials that possess continuously graded properties, such that the growth of cracks is strongly dependent on the gradation of the material. In this work a thermodynamic consistent framework for crack propagation in FGMs is presented, by applying a dissipation inequality to a time-dependent migrating control volume. The direction of crack growth is obtained in terms of material forces as a result of the principle of maximum dissipation. In the numerical implementation a staggered algorithm,deformation update for fixed geometry followed by geometry update for fixed deformation,is employed within each time increment. The geometry update is a result of the incremental crack propagation, which is driven by material forces. The corresponding mesh is generated by combining Delaunay triangulation with local mesh refinement. Furthermore a Newton algorithm is proposed, taking into account mesh transfer of displacements for crack propagation in incremental elasticity. In two numerical examples brittle crack propagation in FGMs is investigated for various directions of strength gradation within the structures. Copyright © 2008 John Wiley & Sons, Ltd. [source]


A robust algorithm for configurational-force-driven brittle crack propagation with R-adaptive mesh alignment

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2007
C. Miehe
Abstract The paper considers a variational formulation of brittle fracture in elastic solids and proposes a numerical implementation by a finite element method. On the theoretical side, we outline a consistent thermodynamic framework for crack propagation in an elastic solid. It is shown that both the elastic equilibrium response as well as the local crack evolution follow in a natural format by exploitation of a global Clausius,Planck inequality in the sense of Coleman's method. Here, the canonical direction of the crack propagation associated with the classical Griffith criterion is the direction of the material configurational force which maximizes the local dissipation at the crack tip and minimizes the incremental energy release. On the numerical side, we exploit this variational structure in terms of crack-driving configurational forces. First, a standard finite element discretization in space yields a discrete formulation of the global dissipation in terms configurational nodal forces. As a consequence, the constitutive setting of crack propagation in the space-discretized finite element context is naturally related to discrete nodes of a typical finite element mesh. Next, consistent with the node-based setting, the discretization of the evolving crack discontinuity is performed by the doubling of critical nodes and interface segments of the mesh. Critical for the success of this procedure is its embedding into an r-adaptive crack-segment reorientation procedure with configurational-force-based directional indicator. Here, successive crack releases appear in discrete steps associated with the given space discretization. These are performed by a staggered loading,release algorithm of energy minimization at frozen crack state followed by the successive crack releases at frozen deformation. This constitutes a sequence of positive-definite discrete subproblems with successively decreasing overall stiffness, providing an extremely robust algorithmic setting in the postcritical range. We demonstrate the performance of the formulation by means of representative numerical simulations. Copyright © 2007 John Wiley & Sons, Ltd. [source]


An accurate scheme for mixed-mode fracture analysis of functionally graded materials using the interaction integral and micromechanics models

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2003
Jeong-Ho Kim
Abstract The interaction integral is a conservation integral that relies on two admissible mechanical states for evaluating mixed-mode stress intensity factors (SIFs). The present paper extends this integral to functionally graded materials in which the material properties are determined by means of either continuum functions (e.g. exponentially graded materials) or micromechanics models (e.g. self-consistent, Mori,Tanaka, or three-phase model). In the latter case, there is no closed-form expression for the material-property variation, and thus several quantities, such as the explicit derivative of the strain energy density, need to be evaluated numerically (this leads to several implications in the numerical implementation). The SIFs are determined using conservation integrals involving known auxiliary solutions. The choice of such auxiliary fields and their implications on the solution procedure are discussed in detail. The computational implementation is done using the finite element method and thus the interaction energy contour integral is converted to an equivalent domain integral over a finite region surrounding the crack tip. Several examples are given which show that the proposed method is convenient, accurate, and computationally efficient. Copyright © 2003 John Wiley & Sons, Ltd. [source]


Numerical implementation of the Crank,Nicolson/Adams,Bashforth scheme for the time-dependent Navier,Stokes equations

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2010
Yinnian He
Abstract This article considers numerical implementation of the Crank,Nicolson/Adams,Bashforth scheme for the two-dimensional non-stationary Navier,Stokes equations. A finite element method is applied for the spatial approximation of the velocity and pressure. The time discretization is based on the Crank,Nicolson scheme for the linear term and the explicit Adams,Bashforth scheme for the nonlinear term. Comparison with other methods, through a series of numerical experiments, shows that this method is almost unconditionally stable and convergent, i.e. stable and convergent when the time step is smaller than a given constant. Copyright © 2009 John Wiley & Sons, Ltd. [source]


A promising boundary element formulation for three-dimensional viscous flow

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 1 2005
Xiao-Wei Gao
Abstract In this paper, a new set of boundary-domain integral equations is derived from the continuity and momentum equations for three-dimensional viscous flows. The primary variables involved in these integral equations are velocity, traction, and pressure. The final system of equations entering the iteration procedure only involves velocities and tractions as unknowns. In the use of the continuity equation, a complex-variable technique is used to compute the divergence of velocity for internal points, while the traction-recovery method is adopted for boundary points. Although the derived equations are valid for steady, unsteady, compressible, and incompressible problems, the numerical implementation is only focused on steady incompressible flows. Two commonly cited numerical examples and one practical pipe flow problem are presented to validate the derived equations. Copyright © 2004 John Wiley & Sons, Ltd. [source]


A priori information in a regularized sinogram-based method for removing ring artefacts in tomography

JOURNAL OF SYNCHROTRON RADIATION, Issue 4 2010
Sofya Titarenko
Ring artefacts in X-ray computerized tomography reconstructions are considered. The authors propose a ring artefact removal method based on a priori information regarding the sinogram including smoothness along the horizontal coordinate, symmetry of the first and the final rows and consideration of small perturbations during acquisition. The method does not require prior reconstruction of the original or corrected sinograms. Its numerical implementation is based on quadratic programming. Its efficacy is examined with regard to experimental data sets collected on graphite and bone. [source]


Qualitative model of concrete acidification due to cathodic protection,

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2008
W. H. A. Peelen
In this paper a mathematical description and numerical implementation for ion transport in concrete due to current passage is developed, in which the heterogeneous equilibrium between Ca2+, OH, and the solid Ca(OH)2 is incorporated. The description is based on the Nernst,Planck equation for ion transport, and reaction terms for the dissolution/precipitation of Ca(OH)2. This description was implemented in the finite element package Comsol Multiphysics. In this way Ca(OH)2 depletion in a zone at a CP anode adjacent to a bulk of concrete with Ca(OH)2 could be modelled in one calculation. Drawback of this model is that the kinetic parameters in the reaction terms are not known, and must be chosen high to ensure the dissolution of Ca(OH)2 to be in equilibrium. This proved numerically challenging and sometimes caused long calculation times. The growth rate of the zone without solid depends on the current density applied, concrete cover, the pore liquid composition and the diffusion constants of Ca2+ and OH,. This rate must be evaluated numerically. This qualitative model of anode acidification shows no participation of Na+; therefore transport properties of this ion do not affect the acidification rate of concrete. The same would hold for any other ion included in the model, which is not involved in electrochemical or chemical reactions. [source]


On the convergence of the finite integration technique for the anisotropic boundary value problem of magnetic tomography

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 9 2003
Roland Potthast
The reconstruction of a current distribution from measurements of the magnetic field is an important problem of current research in inverse problems. Here, we study an appropriate solution to the forward problem, i.e. the calculation of a current distribution given some resistance or conductivity distribution, respectively, and prescribed boundary currents. We briefly describe the well-known solution of the continuous problem, then employ the finite integration technique as developed by Weiland et al. since 1977 for the solution of the problem. Since this method can be physically realized it offers the possibility to develop special tests in the area of inverse problems. Our main point is to provide a new and rigorous study of convergence for the boundary value problem under consideration. In particular, we will show how the arguments which are used in the proof of the continuous case can be carried over to study the finite-dimensional numerical scheme. Finally, we will describe a program package which has been developed for the numerical implementation of the scheme using Matlab. Copyright © 2003 John Wiley & Sons, Ltd. [source]


Loss inclusion via dyadic Green's function modifications for microstrip structures with complex media: Interfacial exponential field behavior within conductor ,

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2001
Clifford M. Krowne
Abstract 2-D field behavior within a metal strip is used to correct the dyadic Green's function for a microstrip structure containing complex-layered media so that the attenuation constant can be determined. In the x -direction, the field is built to display exponential dependence. The strip width is explicitly taken into account, along with the metal thickness and conductivity. New Green's function expressions of the structure are found consistent with a full-wave electromagnetic code employing zero thickness extent conductors for the guiding metal. Implications for numerical implementation are covered. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 54,60, 2001. [source]


An implementation of radiative transfer in the cosmological simulation code gadget

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009
Margarita Petkova
ABSTRACT We present a novel numerical implementation of radiative transfer in the cosmological smoothed particle hydrodynamics (SPH) simulation code gadget. It is based on a fast, robust and photon-conserving integration scheme where the radiation transport problem is approximated in terms of moments of the transfer equation and by using a variable Eddington tensor as a closure relation, following the Optically Thin Variable Eddington Tensor suggestion of Gnedin & Abel. We derive a suitable anisotropic diffusion operator for use in the SPH discretization of the local photon transport, and we combine this with an implicit solver that guarantees robustness and photon conservation. This entails a matrix inversion problem of a huge, sparsely populated matrix that is distributed in memory in our parallel code. We solve this task iteratively with a conjugate gradient scheme. Finally, to model photon sink processes we consider ionization and recombination processes of hydrogen, which is represented with a chemical network that is evolved with an implicit time integration scheme. We present several tests of our implementation, including single and multiple sources in static uniform density fields with and without temperature evolution, shadowing by a dense clump and multiple sources in a static cosmological density field. All tests agree quite well with analytical computations or with predictions from other radiative transfer codes, except for shadowing. However, unlike most other radiative transfer codes presently in use for studying re-ionization, our new method can be used on-the-fly during dynamical cosmological simulation, allowing simultaneous treatments of galaxy formation and the re-ionization process of the Universe. [source]


Astrometric effects of non-uniform telescope throughput

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008
M. Gai
ABSTRACT In real telescopes, the optical parameters evolve with time, and the degradation is often not uniform. This introduces variations in the image profile and therefore photocentre displacements which, unless corrected, may result in astrometric errors. The effects induced on individual telescopes and interferometric arrays are derived by numerical implementation of a range of cases. The results are evaluated with respect to the potential impact on the most relevant experiments for high-precision astrometry in the near future, i.e. Gaia, PRIMA and SIM, and to mitigation techniques applicable from design stage to calibrations. [source]


Theory and Numerics of Rate-Dependent Incremental Variational Formulations in Ferroelectricity

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008
Daniele Rosato
This paper is concerned with macroscopic continuous and discrete variational formulations for domain switching effects at small strains, which occur in ferroelectric ceramics. The developed new three,dimensional model is thermodynamically,consistent and determined by two scalar,valued functions: the energy storage function (Helmholtz free energy) and the dissipation function, which is in particular rate,dependent. The constitutive model successfully reproduces the ferroelastic and the ferroelectric hysteresis as well as the butterfly hysteresis for ferroelectric ceramics. The rate,dependent character of the dissipation function allows us also to reproduce the experimentally observed rate dependency of the above mentioned hysteresis phenomena. An important aspect is the numerical implementation of the coupled problem. The discretization of the two,field problem appears, as a consequence of the proposed incremental variational principle, in a symmetric format. The performance of the proposed methods is demonstrated by means of a benchmark problem. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Modeling and simulation of induced anisotropy and directional hardening effects due to an evolving microstructure in metals

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005
J. Wang
The purpose of the current work is the formulation, numerical implementation and application of a material model for anisotropic hardening in metals taking the interplay between the the direction of inelastic deformation, the orientation of dislocation structures, and the current deformation/loading direction into account. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Numerical Analysis of a Cyclical Loaded Construction under Corrosion Degradation

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005
W. Dudda
A contribution for analytical and numerical tools that permits of a deterministic evaluation of structure behavior in external conditions, under multiparameter and/or cyclic mechanical, thermal and chemical loads, is the aim of this paper. Particular structure elements undergo the plastic and corrosion degradation and they dissipate energy, which consists of irreversible contributions, like a work on the inelastic strains. The construction and its unit lifetime are estimated according to a dissipated energy criterion. The paper emphasizes the modeling and numerical implementation of degradation effects, such as cyclic plasticity, generated by mechanical and thermal loads, stress corrosion, electrochemical corrosion and low-cyclic corrosion. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Nichtlinearer Bettungsansatz von Besler bei Baugrubenwänden

BAUTECHNIK, Issue 9 2005
Achim Hettler Prof. Dr.-Ing. habil.
Im Beitrag wird am Beispiel einer einfach gestützten Wand untersucht, wie im Sinne eines verbesserten Gebrauchstauglichkeitsnachweises das Verhalten des Wandfußes wirklichkeitsnah erfaßt werden kann. Grundlage ist der nichtlineare Bettungsansatz von Besler. Schwerpunkte der Untersuchungen sind die programmtechnische Umsetzung sowie der Einfluß der Biegesteifigkeit und der Vorbelastung aus dem Gewicht des Aushubs auf die Verschiebungen. Aufbauend auf den Ergebnissen werden Empfehlungen für die Anwendung in der Praxis gegeben. Besler's nonlinear subgrade reaction approach for excavation walls. It is investigated how the displacements of the foot of the wall in service states can be described close to the real behaviour. Thereby Besler's non linear approach for the subgrade reaction is used. The main points of the paper are the numerical implementation and the influence of the flexibility and preloading by the weight of the excavation on the displacements. Finally recommendations are given for the use in practice. [source]