Reza Attarnejad

Bio: Reza Attarnejad is an academic researcher from University of Tehran. The author has contributed to research in topics: Finite element method & Beam (structure). The author has an hindex of 17, co-authored 67 publications receiving 1040 citations. Previous affiliations of Reza Attarnejad include University College of Engineering & University of Kashan.

Tsunami generation and associated waves in the water column and seabed due to an asymmetric earthquake motion within an anisotropic substratum

Abstract: In this paper, closed-form integral expressions are derived to describe how surface gravity waves (tsunamis) are generated when general asymmetric ground displacement (due to earthquake rupturing), involving both horizontal and vertical components of motion, occurs at arbitrary depth within the interior of an anisotropic sub-sea solid beneath the ocean. In addition, we compute the resultant hydrodynamic pressure within the seawater and the elastic wavefield within the seabed at any position. The method of potential functions and an integral transform approach, accompanied by a special contour integration scheme, are adopted to handle the equations of motion and produce the numerical results. The formulation accounts for any number of possible acoustic-gravity modes and is valid for both shallow and deep water situations as well as for any focal depth of the earthquake source. Phase and group velocity dispersion curves are developed for surface gravity (tsunami mode), acoustic-gravity, Rayleigh, and Scholte waves. Several asymptotic cases which arise from the general analysis are discussed and compared to existing solutions. The role of effective parameters such as hypocenter location and frequency of excitation are examined and illustrated through several figures which show the propagation pattern in the vertical and horizontal directions. Attention is directed to the unexpected contribution from the horizontal ground motion. The results have important application in several fields such as tsunami hazard prediction, marine seismology and offshore and coastal engineering. In a companion paper we examine the effect of ocean stratification on the appearance and character of internal and surface gravity waves. This article is protected by copyright. All rights reserved.

Derivation of an efficient element for free vibration analysis of rotating tapered Timoshenko beams using basic displacement functions

Abstract: The accuracy of results predicted by finite element method considerably depends on the shape functions used to formulate the displacement field along the element. In this article, a novel approach is introduced to derive an efficient beam element. Special functions, namely Basic Displacement Functions (BDFs), are introduced and derived through power series solution of the static part of the governing differential equations for rotating tapered Timoshenko beams. It is shown that the shape functions could be derived in terms of BDFs through basic principles of structural mechanics. It is shown that the proposed shape functions have the advantage of including the effect of the rotational speed, hub radius, and varying cross-sectional dimensions. In order to verify the competency of the present element in the determination of natural frequencies, several numerical examples are carried out, and the results compared with those in the literature.

Applying wavelets to improve the boundary element method for elasticity problems

Abstract: This paper describes application of fast wavelet transforms in the boundary element method to solve 2D elasticity problems. Daubechies compactly supported orthogonal wavelets have been applied to compress dense and fully populated matrices arising from BEM. GMRES solver is then used to solve linear algebraic systems. A comprehensive sensitivity study is presented to answer the questions like, which order and level of D-wavelets and thresholding parameters are efficient for elasticity problems. Numerical results include a precise study on effect of applying different wavelet orders (D4, D6, D8, D10 and D12), levels and thresholds on the solution accuracy for displacements and stresses and compression ratio of sparsified matrices. The suitable order, level and thresholding parameter as well as saving in computer time and memory are presented for practical engineering problems. The results show that the proposed method is efficient for large problems.

Dam reservoir interaction in time domain

Abstract: In the paper a dynamic exact solution in the time domain for dynamic analysis dam-reservior interaction is presented. The dam structure is flexible with infinite reservoir Exact consideration of the radiation boundary condition of the infinite reservoir and deformation of dam structure are included in the formulation which explicitly expresses the physical phenomena of fluid-structure system. The hydrodynamic pressure in the fluid domain of the structure-reservoir system is assumed to be governed by the pressure wave equation. The upstream face of the dam is considered vertical. The dam structure is modeled as a cantilever Euler-Bernoulli beam. The thickness of the dam is assumed to be variable. A new method for analysis of non-prismatic beams is presented. This new method is based on using new functions namely Basic Displacement Functions (BDFs).These functions are obtained by solving the governing equation of motion of a non-prismatic Euler-Bernoulli beam. Using this method dynamic shape functions are efficiently obtained for non-prismatic beams. Interactive behavior of the dam-reservoir system with different geometrical properties is demonstrated by numerical examples when the system is subjected to ramp acceleration and El Centro earthquake ground motions. The results are compared with those of literature and the competency of the method is shown in both economy and exactness.

Applications of Variational Iteration Method in Applied Hydrology

Abstract: Due to rapid developments in computational mechanics, various advanced numerical and analytical methods for simulation of differential equations in applied science have been proposed Variational iteration method (VIM) and its developments are a class of exact solutions which are mostly implemented in applied physics The present paper focuses on three hydrological phenomena, namely surface infiltration equation (Green-Ampt equation), surface water simulation (fully dynamic equation), and fully infiltration equation (Richards’ equation) and their exact solution with VIM and its modified version presented by Pade approximation The possibility of the application of this type of mathematical approach in applied hydrology has been studied and comparison demonstrates competent developments in physics and applied physics solution procedures

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Introduction to the Finite Element Method

Abstract: This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Seismic Design Of Reinforced Concrete And Masonry Buildings

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