Contact Law (contact + law)

Distribution by Scientific Domains


Selected Abstracts


Pounding of structures modelled as non-linear impacts of two oscillators

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2001
K. T. Chau
Abstract A new formulation is proposed to model pounding between two adjacent structures, with natural periods T1 and T2 and damping ratios ,1 and ,2 under harmonic earthquake excitation, as non-linear Hertzian impact between two single-degree-of-freedom oscillators. For the case of rigid impacts, a special case of our analytical solution has been given by Davis (,Pounding of buildings modelled by an impact oscillator' Earthquake Engineering and Structural Dynamics, 1992; 21:253,274) for an oscillator pounding on a stationary barrier. Our analytical predictions for rigid impacts agree qualitatively with our numerical simulations for non-rigid impacts. When the difference in natural periods between the two oscillators increases, the impact velocity also increases drastically. The impact velocity spectrum is, however, relatively insensitive to the standoff distance. The maximum relative impact velocity of the coupled system can occur at an excitation period Tn* which is either between those of the two oscillators or less than both of them, depending on the ratios T1/T2 and ,1/,2. Although the pounding force between two oscillators has been primarily modelled by the Hertz contact law, parametric studies show that the maximum relative impact velocity is not very sensitive to changes in the contact parameters. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Numerical investigation of the effectiveness of a bored pile wall for the minimisation of settlement resulting from tunnel driving.

GEOMECHANICS AND TUNNELLING, Issue 6 2009
Numerische Untersuchung der Wirkungsweise einer Bohrpfahlwand zur Minimierung der Setzungen infolge Tunnel
Soil mechanics; Innovative procedures; Bodenmechanik; Neue Verfahren Abstract Bored pile walls can be constructed between buildings and tunnel alignments to protect sensitive buildings from settlement resulting from tunnelling. The aim of the research work presented here was to evaluate the effectiveness of such a bored pile wall with FE calculations and identify influential parameters. Two methods of predicting settlement were investigated with the programme ABAQUS: The GAP method, where the deformations of the tunnel contour are prescribed, and the stress reduction method, with which the support pressure at the tunnel contour is reduced. The ground is modelled as linear-elastic, ideal-plastic with a Mohr-Coulomb failure criterion as well as with a hypoplastic constitutive law. The contact surface between wall and ground was modelled with complete bonding as well as with a contact law with friction. The simulation results with the stress reduction method and the hypoplastic material model show the best results qualitatively. The predict settlements agree well with empirical methods and centrifuge tests from the literature. The simulations show that the effectiveness of the wall is significantly influenced by the contact properties in the boundary surface. It achieves the best protection effect when frictionless. Zur Abschirmung sensibler Gebäude vor Setzungen infolge Tunnelvortrieb können Bohrpfahlwände zwischen Gebäude und Tunneltrasse eingesetzt werden. Ziel der hier präsentierten Forschungsarbeit war es, die Wirksamkeit einer solchen Bohrpfahlwand mit FE-Berechnungen nachzuvollziehen und Einflussparameter zu identifizieren. Mit dem Programm ABAQUS wurden zwei Möglichkeiten zur Setzungsprognose untersucht: Die GAPMethode, bei der die Verschiebungen der Tunnelkontur vorgegeben werden, und die Spannungsreduktions-Methode, bei welcher der Stützdruck an der Tunnelkontur reduziert wird. Der Boden wurde als linear-elastisch, ideal-plastisch mit Grenzbedingung nach Mohr-Coulomb sowie mit einem hypoplastischen Stoffgesetz modelliert. Die Kontaktfläche zwischen Wand und Boden wurde sowohl mit vollständigem Verbund als auch mit einem Kontaktgesetz mit Reibung modelliert. Die Simulationsergebnisse mit der Spannungsreduktions-Methode und dem hypoplastischen Materialmodell zeigen die qualitativ besten Ergebnisse. Die Setzungsprognosen stimmen gut mit empirischen Ansätzen und Zentrifugenversuchen aus der Literatur überein. Die Simulationen veranschaulichen, dass die Wirksamkeit der Wand maßgeblich von den Kontakteigenschaften in der Grenzfläche beeinflusst wird. Die größte Abschirmwirkung erzielt sie bei Reibungsfreiheit. [source]


Asymptotic numerical methods for unilateral contact

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2006
W. Aggoune
Abstract New algorithms based upon the asymptotic numerical method (ANM) are proposed to solve unilateral contact problems. ANM leads to a representation of a solution path in terms of series or Padé approximants. To get a smooth solution path, a hyperbolic relation between contact forces and clearance is introduced. Three key points are discussed: the influence of the regularization of the contact law, the discretization of the contact force by Lagrange multipliers and prediction,correction algorithms. Simple benchmarks are considered to evaluate the relevance of the proposed algorithms. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Numerical simulation of granular materials by an improved discrete element method

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2005
J. Fortin
Abstract In this paper, we present an improved discrete element method based on the non-smooth contact dynamics and the bi-potential concept. The energy dissipated during the collisions is taken into account by means of restitution coefficients. The interaction between particles is modelled by Coulomb unilateral contact law with dry friction which is typically non-associated: during the contact, the sliding vector is not normal to the friction cone. The main feature of our algorithm is to overcome this difficulty by means of the bi-potential theory. It leads to an easy implement predictor,corrector scheme involving just an orthogonal projection onto the friction cone. Moreover the convergence test is based on an error estimator in constitutive law using the corner stone inequality of the bipotential. Then we present numerical simulations which show the robustness of our algorithm and the various possibilities of the software ,MULTICOR' developed with this approach. Copyright © 2004 John Wiley & Sons, Ltd. [source]