Force-chain buckling in granular media: a structural mechanics perspective

2010 ◽  
Vol 368 (1910) ◽  
pp. 249-262 ◽  
Author(s):  
Giles W. Hunt ◽  
Antoinette Tordesillas ◽  
Steven C. Green ◽  
Jingyu Shi
Keyword(s):  
Shear Band ◽  
Finite Number ◽  
Granular Medium ◽  
Granular Media ◽  
Structural Model ◽  
Lateral Displacement ◽  
Force Chain ◽  
Linear Elastic ◽  
Evolutionary Route ◽  
Localized Form

Parallels are drawn between the response of a discrete strut on a linear elastic foundation and force-chain buckling in a constrained granular medium. Both systems buckle initially into periodic shapes, with wavelengths that depend on relative resistances to lateral displacement, and curvature in the buckled shape. Under increasing end shortening, the classical structural model evolves to a localized form extending over a finite number of contributing links. By analogy, it is conjectured that the granular model of force-chain buckling might follow much the same evolutionary route into a shear band.

Parametric effect of vertical ground acceleration on the earthquake response of elastic structures

1990 ◽  
Vol 17 (2) ◽  
pp. 209-217 ◽  
Author(s):  
S. T. Ariaratnam ◽  
K. C. K. Leung
Keyword(s):  
Ground Motion ◽  
Structural Model ◽  
Lateral Displacement ◽  
Stochastic Modelling ◽  
Tall Building ◽  
Earthquake Excitation ◽  
Restoring Force ◽  
Ground Acceleration ◽  
Linear Elastic ◽  
Vertical Ground

An analytical procedure is presented for the calculation of the statistical properties of the response of a linear elastic tall building under earthquake excitation. Emphasis is placed on the effect of the vertical ground motion. The restoring force in each story of the structural model is assumed to arise from the bending deformation of the columns whose rigidities are subjected to a general reduction due to the combined action of gravitational forces and the random variations due to vertical ground acceleration. Since earthquakes are random phenomena, stochastic modelling of ground motion seems appropriate. Both the vertical and the horizontal accelerations are treated as amplitude-modulated Gaussian random processes. With these models, the techniques developed herein, using the concept of Markov processes and Itô's stochastic differential equations, may be applied. To illustrate the application of the method, numerical results are presented for a six-story building. For computational purposes, the structural properties are evaluated using the finite element method. Within the limit of linear elastic deformation, the vertical ground acceleration is shown to be capable of causing only a slight increase of 0.08% in the lateral displacement for this moderately tall building. The percentage is expected to be larger for a taller building and much larger when the deformations exceed the elastic limit. Key words: earthquake excitation, elastic frames, random vibration, Markov process, dynamic response.

scholarly journals Under pressure: Hydrogel swelling in a granular medium

2021 ◽  
Vol 7 (7) ◽  
pp. eabd2711
Author(s):  
Jean-François Louf ◽  
Nancy B. Lu ◽  
Margaret G. O’Connell ◽  
H. Jeremy Cho ◽  
Sujit S. Datta
Keyword(s):  
Oil Recovery ◽  
Granular Medium ◽  
Granular Media ◽  
Three Dimensional ◽  
Osmotic Swelling ◽  
Widespread Adoption ◽  
Dry Soil ◽  
Hydrogel Swelling

Hydrogels hold promise in agriculture as reservoirs of water in dry soil, potentially alleviating the burden of irrigation. However, confinement in soil can markedly reduce the ability of hydrogels to absorb water and swell, limiting their widespread adoption. Unfortunately, the underlying reason remains unknown. By directly visualizing the swelling of hydrogels confined in three-dimensional granular media, we demonstrate that the extent of hydrogel swelling is determined by the competition between the force exerted by the hydrogel due to osmotic swelling and the confining force transmitted by the surrounding grains. Furthermore, the medium can itself be restructured by hydrogel swelling, as set by the balance between the osmotic swelling force, the confining force, and intergrain friction. Together, our results provide quantitative principles to predict how hydrogels behave in confinement, potentially improving their use in agriculture as well as informing other applications such as oil recovery, construction, mechanobiology, and filtration.

GRANULAR MEDIA ON A VIBRATING PLATE: A MOLECULAR DYNAMICS SIMULATION

1993 ◽  
Vol 07 (09n10) ◽  
pp. 1779-1788 ◽  
Author(s):  
JASON A.C. GALLAS ◽  
HANS J. HERRMANN ◽  
STEFAN SOKOLOWSKI
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Granular Materials ◽  
Granular Medium ◽  
Granular Media ◽  
Dynamics Simulation ◽  
Dissipation Of Energy ◽  
Conveyor Belts ◽  
Good Agreement ◽  
Vibrating Plate

When sand or other granular materials are shaken, poured or sheared many intriguing phenomena can be observed. We will model the granular medium by a packing of elastic spheres and simulate it via Molecular Dynamics. Dissipation of energy and shear friction at collisions are included. The onset of fluidization can be determined and is in good agreement with experiments. On a vibrating plate we observe the formation of convection cells due to walls or amplitude modulations. Density and velocity profiles on conveyor belts are measured and the influence of an obstacle discussed. We mention various types of rheology for flow down an inclined chute or through a pipe and outflowing containers.

Humidity-Induced Cohesion Effects in Granular Media

2000 ◽  
Vol 627 ◽  
Author(s):  
Nathalie Fraysse ◽  
Luc Petit
Keyword(s):  
Granular Medium ◽  
Granular Media ◽  
Global Scale ◽  
Interparticle Forces ◽  
Wetting Properties ◽  
Small Glass ◽  
Capillary Bridges ◽  
Scale Properties ◽  
Comparison Of The Results ◽  
Maximal Stability

ABSTRACTExperiments were performed under accurately-controlled humidity conditions in order to quantify effects induced by humidity on granular materials. Measurements of the maximal stability angle of a pile made of small glass beads are reported as a function of the relative vapor pressure in the cell, up to close to saturation. The comparison of the results obtained with fluids differing in their molecular interactions with glass, namely water and heptane, shows that the wetting properties of the interstitial liquid on the grains have a strong influence on the cohesion of the non-saturated granular medium. This suggests that gravimetric experiments which could indirectly give information on the size of the capillary bridges that form between grains should be useful to understand the close connection that exists, through interparticle forces, between microscopic properties such as wetting properties and surface roughness of the grains, and global-scale properties of the pile, as its stability and flowability.

scholarly journals Representation of stress and strain in granular materials using functions of direction

2020 ◽  
Vol 22 (4) ◽  
Author(s):  
E. T. R. Dean
Keyword(s):  
Continuous Function ◽  
Granular Materials ◽  
Granular Media ◽  
Physical Space ◽  
Constitutive Modelling ◽  
Rate Equations ◽  
Element Analysis ◽  
History And Memory ◽  
Rigorous Approach ◽  
Linear Elastic

AbstractThis paper proposes a new way of describing effective stress in granular materials, in which stress is represented by a continuous function of direction in physical space. The proposal provides a rigorous approach to the task of upscaling from particle mechanics to continuum mechanics, but is simplified compared to a full discrete element analysis. It leads to an alternative framework of stress–strain constitutive modelling of granular materials that in particular considers directional dependency. The continuous function also contains more information that the corresponding tensor, and thereby provides space for storing information about history and memory. A work-conjugate set of geometric rates representing strain-rates is calculated, and the fundamental principles of local action, determinism, frame indifference, and rigid transformation indifference are shown to apply. A new principle of freedom from tensor constraint is proposed. Existing thermo-mechanics of granular media is extended to apply for the proposed functions, and a new method is described by which strain-rate equations can be used in large-deformations modelling. The new features are illustrated and explored using simple linear elastic models, producing new results for Poisson’s ratio and elastic modulus. Ways of using the new framework to model elastoplasticity including critical states are also discussed.

scholarly journals Anisotropy in granular media: Classical elasticity and directed-force chain network

2003 ◽  
Vol 67 (3) ◽  
Author(s):  
M. Otto ◽  
J.-P. Bouchaud ◽  
P. Claudin ◽  
J. E. S. Socolar
Keyword(s):  
Granular Media ◽  
Force Chain ◽  
Classical Elasticity

scholarly journals Development of Approaches to Creation of Active Vibration Control System in Problems of the Dynamics for Granular Media

2018 ◽  
Vol 148 ◽  
pp. 11004 ◽  
Author(s):  
Andrei P. Khomenko ◽  
Sergey K. Kargapoltsev ◽  
Andrey V. Eliseev
Keyword(s):  
Granular Medium ◽  
Granular Media ◽  
Active Vibration Control ◽  
Evaluation Criteria ◽  
Dynamic Interactions ◽  
Theoretical Understanding ◽  
Vibration Machine ◽  
Vibration Field ◽  
Steel Balls ◽  
Analytical Approaches

The article deals with the development of mathematical models and evaluation criteria of the vibration field in the dynamic interactions of the elements of the vibrational technological machines for the processes of vibrational strengthening of long-length parts with help of a steel balls working medium. The study forms a theoretical understanding of the modes of motions of material particles in interaction with a vibrating surface of the working body of the vibration machine. The generalized approach to the assessment of the dynamic quality of the work of vibrating machines in multiple modes of tossing, when the period of free flight of particles is a multiple of the period of the surface oscillations of the working body, is developed in the article. For the correction of vibration field of the working body, the characteristics of dynamic interactions of granular elements of the medium are taken into account using original sensors. The sensors that can detect different particularities of interaction of the granular medium elements at different points of the working body are proposed to evaluate the deviation from a homogeneous and one-dimensional mode of vibration field. Specially developed sensors are able to register interactions between a single granule, a system of granules in filamentous structures, and multipoint interactions of the elements in a close-spaced cylindrical structure. The system of regularization of the structure of vibration fields based on the introduction of motion translation devices is proposed using the multi-point sensor locations on the working body. The article refers to analytical approaches of the theory of vibration displacements. For the experimental data assessment, the methods of statistical analysis are applied. It is shown that the peculiar features of the motion of granular medium registered by the sensors can be used to build active control systems of field vibration.

scholarly journals Influence of Multiple Openings on Reinforced Concrete Outrigger Walls in a Tall Building

2019 ◽  
Vol 9 (22) ◽  
pp. 4913 ◽  
Author(s):  
Han-Soo Kim ◽  
Yi-Tao Huang ◽  
Hui-Jing Jin
Keyword(s):  
Reinforced Concrete ◽  
Structural Model ◽  
Lateral Displacement ◽  
Tall Buildings ◽  
Structural Performance ◽  
Element Analysis ◽  
Wall Area ◽  
Strut And Tie ◽  
Equivalent Bending Stiffness ◽  
Strut And Tie Model

Outrigger systems have been used to control the lateral displacement of tall buildings. Reinforced concrete (R.C.) outrigger walls with openings can be used to replace conventional steel outrigger trusses. In this paper, a structural model for an R.C. outrigger wall with multiple openings was proposed, and the effects of the multiple openings on the stiffness and strength of the outrigger walls were evaluated. The equivalent bending stiffness of the outrigger wall was derived to predict the lateral displacement at the top of tall buildings and internal shear force developed in the wall. The openings for the passageway in the wall were designed by the strut-and-tie model. The stiffness and strength of the outrigger wall with multiple openings was analyzed by the nonlinear finite element analysis. Taking into consideration the degradation in stiffness and strength, the ratio of the opening area to the outrigger wall area is recommended to be less than 20%. The degradation of stiffness due to openings does not affect the structural performance of the outrigger system when the outrigger has already large stiffness as the case of reinforced concrete outrigger walls.

The Regular Pattern of Demagnetizing Factor Behaviour of Various ‘Cores’ of Granule-Ball Chains

2015 ◽  
Vol 1083 ◽  
pp. 75-79
Author(s):  
Alexander Sandulyak ◽  
Anna Sandulyak ◽  
Vera Ershova ◽  
Petr Shkatov
Keyword(s):  
Granular Medium ◽  
Granular Media ◽  
Relative Size ◽  
Regular Pattern ◽  
Magnetic Media ◽  
Full Agreement ◽  
The Core ◽  
Demagnetizing Factor ◽  
Ferro Magnetic ◽  
The One

We analyze previously not studied issue on the value, nature and manifestation f a demagnetizing factor of effective channels-magnets formed in magnetized granular media by the chains of contacting granules. We provide the factor values for conditionally defined quasi-solid cores of the channels varying in length and diameter, as well as a corresponding consolidating expression which turned out to be exponential with such an argument as the radical of the core relative size. We emphasize full agreement of this expression with the one for a granular medium, i.e. the medium consisting, basically, of the effective channels bundle according to the developed theory of channel-by-channel (selective) magnetization of granular ferro-magnetic media used, e.g. as operating elements in versatile magnetic separators.

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