Techno Press
Tp_Editing System.E (TES.E)
Login Search


You have a Free online access.
csm
 
CONTENTS
Volume 4, Number 1, March 2015
 

Abstract
The state-based peridynamics is considered a nonlocal method in which the equations of motion utilize integral form as opposed to the partial differential equations in the classical continuum mechanics. As a result, the enforcement of boundary conditions in solid mechanics analyses cannot follow the standard way as in a classical continuum theory. In this paper, a new approach for the boundary condition enforcement in the state-based peridynamic formulation is presented. The new method is first formulated based on a convex kernel approximation to restore the Kronecker-delta property on the boundary in 1-D case. The convex kernel approximation is further localized near the boundary to meet the condition that recovers the correct boundary particle forces. The new formulation is extended to the two-dimensional problem and is shown to reserve the conservation of linear momentum and angular momentum. Three numerical benchmarks are provided to demonstrate the effectiveness and accuracy of the proposed approach.

Key Words
state-based; peridynamics; convex kernel approximation; boundary condition

Address
C.T. Wu: Livermore Software Technology Corporation, 7374 Las Positas Road, Livermore, CA 94551, USA
Bo Ren: Department of Civil and Environmental Engineering, University of California, Berkeley CA 94720, USA

Abstract
Modelling and analysis of a brick masonry building involves uncertainties like modelling assumptions and properties of local material. Therefore, it is necessary to perform a calibration to evaluate the dynamic properties of the structure. The response of the finite element model is improved by predicting the parameter by performing linear dynamic analysis on experimental data by comparing the acceleration. Further, a nonlinear dynamic analysis was also performed comparing the roof acceleration and damage pattern of the structure obtained analytically with the test findings. The roof accelerations obtained analytically were in good agreement with experimental roof accelerations. The damage patterns observed analytically after every shock were almost similar to that of experimental observations. Damage pattern with amplification in roof acceleration exhibit the potentiality of earthquake resistant measures in brick masonry models.

Key Words
traditional brick masonry; earthquake resistant brick masonry; concrete damage plasticity; non-linear; acceleration; damage pattern

Address
A. Joshua Daniel and R.N. Dubey: Department of Earthquake Engineering, Indian Institute of Technology Roorkee-247667, India

Abstract
Modeling and simulation of mechanical response of infrastructure object, solids and structures, relies on the use of computational models to foretell the state of a physical system under conditions for which such computational model has not been validated. Verification and Validation (V&V) procedures are the primary means of assessing accuracy, building confidence and credibility in modeling and computational simulations of behavior of those infrastructure objects. Validation is the process of determining a degree to which a model is an accurate representation of the real world from the perspective of the intended uses of the model. It is mainly a physics issue and provides evidence that the correct model is solved (Oberkampf et al. 2002). Our primary interest is in modeling and simulating behavior of porous particulate media that is fully saturated with pore fluid, including cyclic mobility and liquefaction. Fully saturated soils undergoing dynamic shaking fall in this category. Verification modeling and simulation of fully saturated porous soils is addressed in more detail by (Tasiopoulou et al. 2014), and in this paper we address validation. A set of centrifuge experiments is used for this purpose. Discussion is provided assessing the effects of scaling laws on centrifuge experiments and their influence on the validation. Available validation test are reviewed in view of first and second order phenomena and their importance to validation. For example, dynamics behavior of the system, following the dynamic time, and dissipation of the pore fluid pressures, following diffusion time, are not happening in the same time scale and those discrepancies are discussed. Laboratory tests, performed on soil that is used in centrifuge experiments, were used to calibrate material models that are then used in a validation process. Number of physical and numerical examples are used for validation and to illustrate presented discussion. In particular, it is shown that for the most part, numerical prediction of behavior, using laboratory test data to calibrate soil material model, prior to centrifuge experiments, can be validated using scaled tests. There are, of course, discrepancies, sources of which are analyzed and discussed.

Key Words
verification and validation; finite elements; fully coupled analysis; porous media

Address
Panagiota Tasiopoulou: National Technical University of Athens, Athens, Greece
Mahdi Taiebat: Department of Civil Engineering, The University of British Columbia, Vancouver, Canada
Nima Tafazzoli: GeotechnicalEngineer, Tetra Tech EBA, Vancouver, BC, Canada
Boris Jeremic: Department of Civil and Environmental Engineering, University of California, Davis, CA, and Faculty Scientist, Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

Abstract
Numerical prediction of dynamic behavior of fully coupled saturated porous media is of great importance in many engineering problems. Specifically, static and dynamic response of soils – porous media with pores filled with fluid, such as air, water, etc. – can only be modeled properly using fully coupled approaches. Modeling and simulation of static and dynamic behavior of soils require significant Verification and Validation (V&V) procedures in order to build credibility and increase confidence in numerical results. By definition, Verification is essentially a mathematics issue and it provides evidence that the model is solved correctly, while Validation, being a physics issue, provides evidence that the right model is solved. This paper focuses on Verification procedure for fully coupled modeling and simulation of porous media. Therefore, a complete Solution Verification suite has been developed consisting of analytical solutions for both static and dynamic problems of porous media, in time domain. Verification for fully coupled modeling and simulation of porous media has been performed through comparison of the numerical solutions with the analytical ones. Modeling and simulation is based on the so called, u–p–U formulation. Of particular interest are numerical dispersion effects which determine the level of numerical accuracy. These effects are investigated in detail, in an effort to suggest a compromise between numerical error and computational cost.

Key Words
verification; finite elements; fully coupled analysis; porous media; numerical dispersion

Address
Panagiota Tasiopoulou: National Technical University of Athens, Athens, Greece
Mahdi Taiebat: Department of Civil Engineering, The University of British Columbia, Vancouver, BC, Canada
Nima Tafazzoli: Tetra Tech EBA, Vancouver, BC, Canada
Boris Jeremic: Department of Civil and Environmental Engineering, University of California, Davis, CA, USA and
Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

Abstract
In this paper, a refined exponential shear deformation beam theory is developed for bending analysis of functionally graded beams. The theory account for parabolic variation of transverse shear strain through the depth of the beam and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. Contrary to the others refined theories elaborated, where the stretching effect is neglected, in the current investigation this so-called \"stretching effect\" is taken into consideration. The material properties of the functionally graded beam are assumed to vary according to power law distribution of the volume fraction of the constituents. Based on the present shear deformation beam theory, the equations of motion are derived from Hamilton\'s principle. Analytical solutions for static are obtained. Numerical examples are presented to verify the accuracy of the present theory.

Key Words
bending; dynamic analysis; functionally graded; stretching effect; vibration

Address
L. Hadji, Z. Khelifa and T.H. Daouadji: Université Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algérie;
Laboratoire des Matériaux and Hydrologie, Université de Sidi Bel Abbes, 22000 Sidi Bel Abbes, Algérie
E.A. Bedia: Laboratoire des Matériaux and Hydrologie, Université de Sidi Bel Abbes, 22000 Sidi Bel Abbes, Algérie


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com