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A model for the evolution of concrete deterioration due to reinforcement corrosion
, Article Mathematical and Computer Modelling ; Volume 52, Issue 9-10 , November , 2010 , Pages 1403-1422 ; 08957177 (ISSN) ; Kiani, K ; Hashemian, A ; Sharif University of Technology
2010
Abstract
One of the most crucial factors affecting the service life of reinforced concrete (RC) structures attacked by aggressive ions is reinforcement corrosion. As the steel corrosion progresses, crack propagation in concrete medium endangers the serviceability and the strength of RC structural members. In this study, a nonlinear mathematical model for determining the displacement and stress fields in RC structures subjected to reinforcement corrosion is introduced. For corrosion products, a nonlinear stress-strain relation which has been previously confirmed by experimental data is incorporated in the present analysis. In formulation of the governing equations for steel-rust-concrete composite,...
A numerical solution of 2D Buckley-Leverett equation via gradient reproducing kernel particle method
, Article CMES - Computer Modeling in Engineering and Sciences ; Volume 32, Issue 1 , 2008 , Pages 17-33 ; 15261492 (ISSN) ; Hashemian, A ; Sharif University of Technology
2008
Abstract
Gradient reproducing kernel particle method (GRKPM) is a meshless technique which incorporates the first gradients of the function into the reproducing equation of RKPM. Therefore, in two-dimensional space GRKPM introduces three types of shape functions rather than one. The robustness of GRKPM's shape functions is established by reconstruction of a third-order polynomial. To enforce the essential boundary conditions (EBCs), GRKPM's shape functions are modified by transformation technique. By utilizing the modified shape functions, the weak form of the nonlinear evolutionary Buckley-Leverett (BL) equation is discretized in space, rendering a system of nonlinear ordinary differential equations...
A remedy to gradient type constraint dilemma encountered in RKPM
, Article Advances in Engineering Software ; Volume 38, Issue 4 , 2007 , Pages 229-243 ; 09659978 (ISSN) ; Hashemian, A ; Sharif University of Technology
Elsevier Ltd
2007
Abstract
A major disadvantage of conventional meshless methods as compared to finite element method (FEM) is their weak performance in dealing with constraints. To overcome this difficulty, the penalty and Lagrange multiplier methods have been proposed in the literature. In the penalty method, constraints cannot be enforced exactly. On the other hand, the method of Lagrange multiplier leads to an ill-conditioned matrix which is not positive definite. The aim of this paper is to boost the effectiveness of the conventional reproducing kernel particle method (RKPM) in handling those types of constraints which specify the field variable and its gradient(s) conveniently. Insertion of the gradient term(s),...
Comparison of natural frequencies of composite cylindrical shells: A squared lattice with its equivalent seamless one
, Article Proceedings of the ASME Design Engineering Technical Conference, 15 August 2010 through 18 August 2010 ; Volume 5 , 2010 , Pages 835-841 ; 9780791844137 (ISBN) ; Jam, J. E ; Hashemian, A. H ; Sharif University of Technology
Abstract
Modern Latticed composite materials whose high specific strength and stiffness are utilized in spacecraft and rocket structures to a sufficiently high extent are now widely used in primary airframe structures. In this work a comparison between squared latticed composite cylinder shells and the equivalent hollow cylinder with same weight, outer radius, length and material is done. An analytical equation is derived for natural frequency of square latticed composite shells. The first fifth modes are taken to be compared. The analytical and FEM results are shown and compared to each other. Also, as discussed, the squared lattice cylinder shell reaches to their natural frequencies easily than the...
RKPM with augmented corrected collocation method for treatment of material discontinuities
, Article CMES - Computer Modeling in Engineering and Sciences ; Volume 62, Issue 2 , 2010 , Pages 171-204 ; 15261492 (ISSN) ; Khezri, M ; Hashemian, A ; Behzadan, A ; Sharif University of Technology
2010
Abstract
An accurate numerical methodology for capturing the field quantities across the interfaces between material discontinuities, in the context of reproducing kernel particle method (RKPM), is of particular interest. For this purpose the innovative numerical technique, so-called augmented corrected collocation method is introduced; this technique is an extension of the corrected collocation method used for imposing essential boundary conditions (EBCs). The robustness of this methodology is shown by utilizing it to solve two benchmark problems of material discontinuities, namely the problem of circular inhomogeneity with uniform radial eigenstrain, and the problem of interaction between a crack...