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Nonlinear finite element modeling of shear-critical reinforced concrete beams using a set of interactive constitutive laws
, Article International Journal of Civil Engineering ; Volume 14, Issue 8 , 2016 , Pages 507-519 ; 17350522 (ISSN) ; Kazemi, M. T ; Sharif University of Technology
Iran University of Science and Technology
2016
Abstract
Complex nature of diagonal tension accompanied by the formation of new cracks as well as closing and propagating preexisting cracks has deterred researchers to achieve an analytical and mathematical procedure for accurate predicting shear behavior of reinforced concrete, and there is the lack of a unique theory accepted universally. Shear behavior of reinforced concrete is studied in this paper based on recently developed constitutive laws for normal strength concrete and mild steel bars using the nonlinear finite element method. The salient feature of these stress-strain relations is to account the interactive effects of concrete and embedded bars on each other in a smeared rotating crack...
Social Reality in John Searle: Do Institutional Facts have Physical Realization?
, M.Sc. Thesis Sharif University of Technology ; Taqavi, Mostafa (Supervisor)
Abstract
In the extension of his former developments of the theories of philosophy of mind and language, John Searle (1932- ) proceeded into the realm of social reality by his The Construction of Social Reality and Making the Social World, written in 1995 and 2010 respectively. With his naturalistic background, he placed his new theory on top of his former theories of mind and language already naturalized and fully worked out. As we will see, social reality comes with our three marvelous capacities, not coming together, to the extent we know, in animals other than us: collective intentionality, assignment of function, and language; all of them already being treated by Searle, in a naturalized manner,...
Numerical modelling of dynamically loaded metal foam-filled square columns
, Article International Journal of Impact Engineering ; Volume 34, Issue 3 , 2007 , Pages 573-586 ; 0734743X (ISSN) ; Petrinic, N ; Vafai, A ; Sharif University of Technology
2007
Abstract
The crushing behaviour of dynamically loaded metal foam-filled square columns has been investigated using an extended version of the existing self-similar pressure dependent constitutive model for metal foams. The model has been implemented in ABAQUS/Explicit and analyses have been conducted using different approaches to model the uniaxial and hydrostatic hardening behaviour of metal foams. A practical and reliable procedure to approximate the observed anisotropic behaviour within the computational framework of isotropic plasticity is introduced. The comparison between the available experimental and newly generated numerical results is presented in order to illustrate the accuracy and...
Validity and size-dependency of Cauchy-Born hypothesis with Tersoff potential in silicon nano-structures
, Article Computational Materials Science ; Volume 63 , 2012 , Pages 168-177 ; 09270256 (ISSN) ; Dormohammadi, H ; Sharif University of Technology
Elsevier
2012
Abstract
One of the most popular constitutive rules that correlate the continuum and atomic properties in multi-scale models is the Cauchy-Born (CB) hypothesis. Based on this constitutive law of continuum media, it assumes that all atoms follow the deformation subjected to the boundary of crystal. In this paper, the validity and failure of CB hypothesis are investigated for the silicon nano-structure by comparison of the continuum and atomic properties. In the atomistic level, the stresses and position of atoms are calculated using the molecular dynamics (MD) simulation based on the Tersoff inter-atomic potential. The stresses and strains are compared between the atomistic and continuous media to...
Sintering viscosity and sintering stress of nanostructured WC-Co parts prepared by powder injection moulding
, Article Powder Metallurgy ; Volume 54, Issue 1 , Nov , 2011 , Pages 84-88 ; 00325899 (ISSN) ; Sharif University of Technology
2011
Abstract
The uniaxial viscosity and sintering stress of WC-10Co-0·9VC (wt-%) were obtained by a loading dilatometer as functions of fractional density (0·64<ρ<0·93) and temperature (1084
Assessing Liquefaction Potential Based on Cone Penetration Test Results
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
This study aimed to model the cone penetration test using FLAC 2D software in order to investigate the silty soils that can be found in tailing dams. Additionally, the model of the direct simple shear test was built in the software to estimate the variation of liquefaction potential in these soils with in-situ conditions. It should be noted that the constitutive law used in this study was the NORSAND model which meets the requirements of modeling in both tests. After validating the models, several important parameters are considered as variables to examine their effects on the results of both experiments. Regarding the validation of the models, the constructed numerical models of the cone...
Visco-hyperelastic constitutive law for modeling of foam's behavior
, Article Materials and Design ; Volume 32, Issue 5 , 2011 , Pages 2940-2948 ; 02641275 (ISSN) ; Alizadeh, Y ; Sharif University of Technology
2011
Abstract
This paper proposes a new visco-hyperelastic constitutive law for modeling the finite-deformation strain rate-dependent behavior of foams as compressible elastomers. The proposed model is based on a phenomenological Zener model, which consists of a hyperelastic equilibrium spring and a Maxwell element parallel to it. The hyperelastic equilibrium spring describes the steady state response. The Maxwell element, which captures the rate-dependency behavior, consists of a nonlinear viscous damper connected in series to a hyperelastic intermediate spring. The nonlinear damper controls the rate-dependency of the Maxwell element. Some strain energy potential functions are proposed for the two...
End bearing capacity of drilled shafts in sand: a numerical approach
, Article Geotechnical and Geological Engineering ; Volume 27, Issue 2 , 2009 , Pages 195-206 ; 09603182 (ISSN) ; Khabbazian, M ; Sharif University of Technology
2009
Abstract
In this paper, a modeling procedure is carried out to numerically analyze the end bearing capacity of drilled shafts in sand. The Mohr-Coulomb elastic plastic constitutive law with stress dependent elastic parameters is used for all numerical analyses performed in this study. The numerical results are compared with the available experimental equations. It is seen that numerical results are in good agreement with experimental equations. The variation of the end bearing capacity of drilled shafts versus embedment depth is also studied. Numerical results show that with increase in pile embedment depth, the end bearing capacity increases. However, the rate of increase becomes smaller as the pile...
Strain energy-based homogenization of nonlinear elastic particulate composites
, Article International Journal of Engineering Science ; Volume 47, Issue 10 , 2009 , Pages 1038-1048 ; 00207225 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
2009
Abstract
The macroscopic constitutive law for a heterogeneous solid containing two dissimilar nonlinear elastic phases undergoing finite deformation is obtained. Attention is restricted to the case of spherical symmetry such that only the materials consisting of an irregular suspension of perfectly spherical particles experiencing all-round uniform loading are considered which leads to a one-dimensional modeling. For the homogenization procedure, a strain-energy based scheme which utilizes Hashin's composite sphere is employed to obtain the macroscopic stress-deformation relation added by the initial volume fraction of the particles. As applications of the procedure, the closed-form macroscopic...
Stability and size-dependency of cauchy-born hypothesis in three-dimensional applications
, Article International Journal of Solids and Structures ; Volume 46, Issue 9 , 2009 , Pages 1925-1936 ; 00207683 (ISSN) ; Abdolhosseini Qomi, M. J ; Kazemi, M. T ; Khoei, A. R ; Sharif University of Technology
2009
Abstract
The Cauchy-Born hypothesis (CB) provides a hierarchical approach in the molecular theory of crystal elasticity to relate the continuum and atomic deformations. This kinematic theory has been extensively used as the constitutive law of continuum regions in multi-scale models. In these models, the fine scale is proposed to describe the real behavior of crystalline structure wherever the continuum description fails. The main objective of this article is to investigate the stability and size-dependency of CB hypothesis in three-dimensional applications by direct comparison of information between atomistic and continuous description of a medium. The Sutton-Chen many-body potential is used for the...
An energetically consistent annular crack in a piezoelectric medium
, Article Engineering Fracture Mechanics ; Volume 77, Issue 5 , 2010 , Pages 819-831 ; 00137944 (ISSN) ; Moeini Ardakani, S. S ; Shodja, H. M ; Sharif University of Technology
2010
Abstract
The analytical treatment of an energetically consistent annular crack in a piezoelectric solid subjected to remote opening electromechanical loading is addressed. Potential functions and Hankel transform in combination with a robust technique are employed to reduce the solution of the mixed boundary value problem into a Fredholm integral equation of the second kind. The limiting case of a penny-shaped crack in a piezoelectric medium with energetically consistent boundary conditions over the crack faces is extracted for the first time. The electrical discharge phenomenon within the crack gap is modeled utilizing a non-linear constitutive law and the effects of the breakdown field on the...
Modeling of visco-hyperelastic behavior of foams
, Article 2008 ASME International Mechanical Engineering Congress and Exposition, IMECE 2008, Boston, MA, 31 October 2008 through 6 November 2008 ; Volume 12 , 2009 , Pages 425-433 ; 9780791848739 (ISBN) ; Asghari, M ; Naghdabadi, R ; Sharif University of Technology
2009
Abstract
In this paper, a new visco-hyperelastic constitutive law for describing the rate dependent behavior of foams is proposed. The proposed model was based on a phenomenological Zener model: a hyperelastic equilibrium spring, which describes the steady-state, long-term response, parallel to a Maxwell element, which captures the rate-dependency. A nonlinear viscous damper connected in series to a hyperelastic intermediate spring, controls the rate-dependency of the Maxwell element. Therefore, the stress is the sum of equilibrium stress on the equilibrium spring and overstress on the intermediate spring. In hyperelastic theory stress is not calculated directly as in the case of small-strain, linear...
Finite-element modelling of laterally loaded piles in clay
, Article Proceedings of the Institution of Civil Engineers: Geotechnical Engineering ; Volume 162, Issue 3 , 2009 , Pages 151-163 ; 13532618 (ISSN) ; Ahmari, S ; Sharif University of Technology
2009
Abstract
A three-dimensional finite-element procedure is used to analyse laterally loaded piles in clay. A strain-hardening von Mises constitutive law is used in the analyses. Two field-measured full-scale case studies, one in soft clay and the other one in stiff clay, are investigated by the constructed finite-element model. In order to study soil anisotropy and soil mass secondary structure, the real shear strength and elastic modulus are back-calculated by fitting the pile head load-deflection curve to the field results. Comparing back-calculated shear strength values with the measured ones indicates high anisotropy effect in stiff clay. In order to verify the model validity, the maximum occurred...
On the multi-scale computation of un-bonded flexible risers
, Article Engineering Structures ; Volume 32, Issue 8 , August , 2010 , Pages 2287-2299 ; 01410296 (ISSN) ; Alfano, G ; Bahai, H ; Hosseini Kordkheili, S. A ; Sharif University of Technology
2010
Abstract
The purpose of this paper is to model the detailed effects of interactions that take place between components of un-bonded flexible risers, and to study the three-dimensional motion responses of risers when subjected to axial loads, bending moments, and internal and external pressures. A constitutive law for un-bonded flexible risers is proposed and a procedure for the identification of the related input parameters is developed using a multi-scale approach. A generalized finite element structural model based on the Euler-Bernoulli beam theory is developed in which the constitutive law is embedded. The beam theory is enhanced by the addition of suitable pressure terms to the generalized...