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Static and dynamic pushover analysis of steel moment resisting frames
, Article 10th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2010, Bangkok, 3 August 2006 through 5 August 2006 ; Volume 3 , 2006 , Pages 459-464 ; 9748257231 (ISBN); 9789748257235 (ISBN) ; Rahimzadeh Rofooei, F ; Khajeh Ahmad Attari, N ; Shodja, A. H ; Sharif University of Technology
2006
Abstract
Pushover analysis is a simplified nonlinear analysis technique that can be used to estimate the dynamic demands imposed on a structure under earthquake excitations. One of the first steps taken in this approximate solution is to assess the maximum roof displacement, known as target displacement, using the base shear versus roof displacement diagram. That could be done by the socalled dynamic pushover analysis, i.e. a dynamic time history analysis of an equivalent single degree of freedom model of the original system, as well as other available approximate static methods. In this paper, a number of load patterns, including a new approach, are considered to construct the related pushover...
High resolution simulations of unstable modes in a collisionless disc
, Article Astronomy and Astrophysics ; Volume 473, Issue 1 , 2007 , Pages 31-40 ; 00046361 (ISSN) ; Just, A ; Korchagin, V. I ; Jalali, M. A ; Sharif University of Technology
2007
Abstract
We present N-body simulations of unstable spiral modes in a dynamically cool collisionless disc. We show that spiral modes grow in a thin collisionless disk in accordance with the analytical perturbation theory. We use the particle-mesh code SUPERBOX with nested grids to follow the evolution of unstable spirals that emerge from an unstable equilibrium state. We use a large number of particles (up to N = 40 & 106) and high-resolution spatial grids in our simulations (1283 cells). These allow us to trace the dynamics of the unstable spiral modes until their wave amplitudes are saturated due to nonlinear effects. In general, the results of our simulations are in agreement with the analytical...
Cryptanalysis of a Stream Cipher with Large Variables Using Distinguishing Attack
, M.Sc. Thesis Sharif University of Technology ; Salmasizadeh, Mahmoud (Supervisor) ; Mohajeri, Javad (Supervisor)
Abstract
Distinguishing Attacks are a class of attacks on stream ciphers, which evaluate the random peroperties of the keystream generated by a stream cipher. In fact in these attacks the cryptanalyst tries to determine whether a stream is generated by a specific cipher or it seems random. Most of the Distinguishing attacks use the linear cryptanalysis technique and are called Linear Distinguishing Attack. The focus of this thesis is on linear distinguishing attacks. After a survey on stream ciphers and their cryptanalysis methods, distinguishing attack is introduced in detail. Then a new successful linear distinguishing attack on a recently developed stream cipher, Shannon, is presented. This attack...
Effect of molybdenum on grain boundary segregation in Incoloy 901 superalloy
, Article Materials and Design ; Volume 46 , 2013 , Pages 573-578 ; 02641275 (ISSN) ; Abbasi, S. M ; Sharif University of Technology
2013
Abstract
In this paper, the effect of molybdenum on the grain boundary segregation of other elements was studied in Incoloy 901 superalloy. Initially, five alloys were prepared with different percentages of Mo by using a vacuum induction furnace. Then, these alloys were remelted by Electro-slag remelting (ESR) process and after homogenizing at 1160 °C for 2. h followed by air cooling, were rolled. The effect of Mo on segregation of elements was evaluated with Scanning Electron Microscopy, Linear Analysis, and the mechanical tests. The results showed that the grain boundary segregations of elements in Incoloy 901 superalloy were decreased by increasing of molybdenum content up to 6.7% and the...
Numerical study of Slotted-Web-Reduced-Flange moment connection
, Article Journal of Constructional Steel Research ; Volume 69, Issue 1 , February , 2012 , Pages 1-7 ; 0143974X (ISSN) ; Tabbakhha, M ; Sharif University of Technology
2012
Abstract
Reduced Beam Section (RBS) and Slotted Beam Web (SBW) are two types of seismic resistant moment connections that were introduced after the 1994 Northridge earthquake. These connections have been tested under cyclic loading and have had acceptable performance. In this paper, a new hybrid connection is introduced that is composed of RBS and SBW and is named Slotted-Web-Reduced- Flange (SWRF). Nonlinear finite element analyses are performed on SWRF under cyclic loading. It is shown that the new connection in some cases performs better than its RBS and SBW predecessors. The effects of panel zone strength, continuity plates and slot length are also investigated
Nonlinear Seismic Analysis of Concrete Rectangular Storage Tanks Considering Soil-Structure-Interaction
, M.Sc. Thesis Sharif University of Technology ; Khalu, Alireza (Supervisor)
Abstract
Liquid storage tanks as part of the lifeline facilities play an important role in the rescuer work and drinking water supply after earthquakes. Importance of these structures demonstrates the need for investigating their dynamic behavior under dynamic loading. To assure the safety of liquid storage tanks, the dynamic response of liquid storage tanks has been studied intensively in the past. Housner proposed a widely used analytical model in which the hydrodynamic pressures are separated into impulsive and convective components. This model is mostly used for the horizontal groud motion. In this study, considering soil-structure interaction (SSI), nonlinear dynamic behavior of concrete...
Three-dimensional geometrically nonlinear analysis of slack cable structures
, Article Computers and Structures ; Volume 128 , November , 2013 , Pages 160-169 ; 00457949 (ISSN) ; Sharif University of Technology
2013
Abstract
An effective iterative method is proposed for three-dimensional large-displacement analysis of structures consisting of slack cables as the primary load-bearing system. This approach takes advantage of substructuring technique that is specially tailored to address the analysis and form-finding problem of slack cables subjected to arbitrary loads, and to reduce the overall analysis costs. At the overall structural level, a robust procedure is employed for detecting the instabilities and limiting the corresponding incremental displacements. The effectiveness of the proposed method for the analysis of highly unstable or variable-form structures is demonstrated by a number of analysis examples...
Finite element modelling and seismic behaviour of integral abutment bridges considering soil–structure interaction
, Article European Journal of Environmental and Civil Engineering ; 2018 , Pages 1-20 ; 19648189 (ISSN) ; Maleki, S ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
A comprehensive non-linear finite element (FE) model of integral abutment bridges (IABs) is presented to facilitate the analysis of such bridges using commercial software, especially under seismic loading. The presented model is capable of capturing non-linearity in both the structure and soil, in addition to considering far-field soil response. The model is simple enough to be used for practical purposes. On the other hand, many aspects of seismic behaviour of IABs are unclear, due to complicated soil–structure interaction. Using the presented model, a parametric study is performed to identify the effects of bridge length, abutment type and soil type on seismic behaviour of IABs. Non-linear...
Finite element modelling and seismic behaviour of integral abutment bridges considering soil–structure interaction
, Article European Journal of Environmental and Civil Engineering ; Volume 24, Issue 6 , January , 2020 , Pages 767-786 ; Maleki, S ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
A comprehensive non-linear finite element (FE) model of integral abutment bridges (IABs) is presented to facilitate the analysis of such bridges using commercial software, especially under seismic loading. The presented model is capable of capturing non-linearity in both the structure and soil, in addition to considering far-field soil response. The model is simple enough to be used for practical purposes. On the other hand, many aspects of seismic behaviour of IABs are unclear, due to complicated soil–structure interaction. Using the presented model, a parametric study is performed to identify the effects of bridge length, abutment type and soil type on seismic behaviour of IABs. Non-linear...
Non-linear analysis of functionally graded circular plates under asymmetric transverse loading
, Article International Journal of Non-Linear Mechanics ; Volume 44, Issue 8 , 2009 , Pages 928-942 ; 00207462 (ISSN) ; Fallah, F ; Sharif University of Technology
2009
Abstract
Based on the first-order shear deformation plate theory with von Karman non-linearity, the non-linear axisymmetric and asymmetric behavior of functionally graded circular plates under transverse mechanical loading are investigated. Introducing a stress function and a potential function, the governing equations are uncoupled to form equations describing the interior and edge-zone problems of FG plates. This uncoupling is then used to conveniently present an analytical solution for the non-linear asymmetric deformation of an FG circular plate. A perturbation technique, in conjunction with Fourier series method to model the problem asymmetries, is used to obtain the solution for various clamped...
Application of the endurance time method in seismic analysis of concrete gravity dams
, Article Scientia Iranica ; Volume 18, Issue 3 A , June , 2011 , Pages 326-337 ; 10263098 (ISSN) ; Estekanchi, H. E ; Vafai, A ; Ghaemian, M ; Sharif University of Technology
2011
Abstract
In this paper, application of the Endurance Time (ET) method in seismic analysis of concrete gravity dams has been investigated. The ET method is based on time history analysis of structures, subjected to specially designed intensifying acceleration functions. It is expected that by developing its application in analysis of concrete dams, useful information on the seismic behavior of such dams at various excitation intensities can be obtained. Results from linear analysis of Folsom and Koyna dams under real earthquakes and ET acceleration functions have been compared. It is shown that the ET method can predict the response of concrete gravity dams to individual earthquakes with reasonable...
A layerwise finite element for geometrically nonlinear analysis of composite shells
, Article Composite Structures ; Volume 186 , 2018 , Pages 355-364 ; 02638223 (ISSN) ; Soltani, Z ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This work aims to develop a nonlinear layerwise shell element formulation for shear-deformable laminated composite plate and shell structures. The element is formulated based on a zigzag theory in presence of individual local coordinates in the thickness direction for separate layers. In order to properly employ the zigzag theory, the considered local coordinates have different ranges of variation for middle, upper and lower layers. Using Mindlin-Reissner theory a convenient displacement field is derived for each layer and an ordered algorithm is adapted to calculate increments in the director vector of each layer due to relative finite rotations of its adjacent layers. Employing this shear...
On the geometrically nonlinear analysis of sandwich shells with viscoelastic core: a layerwise dynamic finite element formulation
, Article Composite Structures ; Volume 230 , 2019 ; 02638223 (ISSN) ; Khorasani, R ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The objective of this work is to present a finite element formulation for dynamic analysis of sandwich shells with viscoelastic core under large deformation. The present study is based on an incremental updated Lagrangian approach together with the Newmark integration scheme. The viscoelastic constitutive model which is used to define the behavior of the core, comes from the Riesz theorem and the corresponding creep functions are estimated using Dirichlet-Prony series. Also, the viscoelastic deferred strain is derived in an appropriate incremental form using the state variables. The employed layerwise shell element which is based on zig-zag theory has eight nodes on its mid layer. What's...
Experimental and numerical study of geometrically nonlinear behavior of corrugated laminated composite shells using a nonlinear layer-wise shell FE formulation
, Article Engineering Structures ; Volume 184 , 2019 , Pages 61-73 ; 01410296 (ISSN) ; Hosseini Kordkheili, S. A ; Kress, G ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper presents experimental and numerical studies on the geometrically nonlinear behavior of corrugated laminated composite shells (CLCS) under quasi-static loading along the corrugated direction. A geometrically nonlinear layer-wise shell finite element formulation is adopted to study the behavior of CLCS under large deformation by modeling of incremental different moduli in the tensile and compressive regimes through the thickness, where the spatial location of neutral axis shifts with deformation. A master curve is presented to estimate the value of compressive modulus from given tensile and flexural moduli. Using the prepreg autoclave method, the paper also describes practical...
Analytical non-linear analysis of functionally graded sandwich solid/annular sector plates
, Article Composite Structures ; Volume 275 , 2021 ; 02638223 (ISSN) ; Fallah, F ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Nonlinear behavior of functionally graded (FG) sandwich circular sector plates with simply supported radial edges under transverse loading is investigated using the first-order shear deformation theory with von Karman geometric nonlinearity. The nonlinear governing equations are reformulated and solved via single-parameter perturbation and Fourier series methods. Verification is performed by comparing numerical results with the available ones in the literature and the ones obtained via ABAQUS code. The effects of non-linearity, material constant, lay-up, and boundary conditions on bending of FG sandwich sector plates with FG core/homogenous face sheets and metallic core/FG face sheets are...
Non-linear finite element implementation of micropolar hypo-elastic materials
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 197, Issue 49-50 , 15 September , 2008 , Pages 4149-4159 ; 00457825 (ISSN) ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
2008
Abstract
In this paper, updated Lagrangian finite element formulations for large elastic deformation of micropolar hypo-elastic materials are presented. Using representation theorems of tensor functions, the general form of the constitutive equations for the micropolar hypo-elastic materials model are presented. The finite element formulations are based on the general form of the micropolar hypo-elastic constitutive equations in conjunction with Jaumann rate and a new rate called gyration rate. Gyration rate describes the deformation of the material in view of an observer attached to the micro-structure. An incrementally objective stress and couple stress update procedure is developed and its...
On the assessment of modal nonlinear pushover analysis for steel frames with semi-rigid connections
, Article Structural Engineering and Mechanics ; Volume 32, Issue 3 , 2009 , Pages 383-398 ; 12254568 (ISSN) ; Mofid, M ; Sharif University of Technology
2009
Abstract
Applying nonlinear statistical analysis methods in estimating the performance of structures in earthquakes is strongly considered these days. This is due to the methods' simplicity, timely lower cost and reliable estimation in seismic responses in comparison with time-history nonlinear dynamic analysis. Among nonlinear methods, simplified to be incorporated in the future guidelines, Modal Pushover Analysis, known by the abbreviated name of MPA, simply models nonlinear behavior of structures; and presents a very proper estimation of nonlinear dynamic analysis using lateral load pattern appropriate to the mass. Mostly, two kinds of connecting joints, 'hinge' and 'rigid', are carried out in...