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plates--structural-components
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Geometrically nonlinear micro-plate formulation based on the modified couple stress theory
, Article International Journal of Engineering Science ; Volume 51 , 2012 , Pages 292-309 ; 00207225 (ISSN) ; Sharif University of Technology
2012
Abstract
The couple stress theory is a non-classical continuum theory which is capable to capture size effects in small-scale structures. This property makes it appropriate for modeling the structures in micron and sub-micron scales. The purpose of this paper is the derivation of the governing motion equations and boundary conditions for the geometrically nonlinear micro-plates with arbitrary shapes based on the modified version of the couple stress theory. The consistent boundary conditions are provided at smooth parts of the plate periphery and also at the sharp corners of the periphery using variational approach
Parametric analyses on the initial stiffness of the SHS column base plate connections using FEM
, Article Engineering Structures ; Volume 34 , 2012 , Pages 363-370 ; 01410296 (ISSN) ; Mohamadi-shooreh, M. R ; Mofid, M ; Sharif University of Technology
Abstract
Bolted Column Base Plate (BCBP) connections are widely used to connect steel columns to the concrete foundations. This paper conducts a parametric study on the initial stiffness of bolted base plate with Square Hollow Section (SHS) column connection, through an extended 3-D Finite Element Modeling (FEM). Different features of the connection such as material behavior, geometric details, typical contact phenomena and large displacements are also considered in the modeling. A comparison between experimental test and FEM is carried out to illustrate the ability of the numerical method to simulate the connection behavior. An analytical explanation on the initial stiffness of the connection is...
Parametric study of the dynamic response of thin rectangular plates traversed by a moving mass
, Article Acta Mechanica ; Volume 223, Issue 1 , September , 2012 , Pages 15-27 ; 00015970 (ISSN) ; Rofooei, F. R ; Sharif University of Technology
2012
Abstract
The governing differential equation of motion of a thin rectangular plate excited by a moving mass is considered. The moving mass is traversing on the plate's surface at arbitrary trajectories. Eigenfunction expansion method is employed to solve the constitutive equation of motion for various boundary conditions. Approximate and exact expressions of the inertial effects are adopted for the problem formulation. In the approximate formulation, only the vertical acceleration component of the moving mass is considered while in the exact formulation all the convective acceleration components are included in the problem formulation as well. Parametric studies are carried out to investigate the...
Interlaminar stress analysis of general composite laminates
, Article International Journal of Mechanical Sciences ; Volume 53, Issue 11 , 2011 , Pages 958-967 ; 00207403 (ISSN) ; Yazdani Sarvestani, M ; Sharif University of Technology
Abstract
In this study, based on the reduced from of elasticity displacement field for a long laminate, an analytical method is established to exactly obtain the interlaminar stresses near the free edges of generally laminated composite plates under the extension and bending. The constant parameters, which describe the global deformation of a laminate, are properly computed by means of the improved first-order shear deformation theory. Reddys layerwise theory is subsequently utilized for analytical and numerical examinations of the boundary layer stresses within arbitrary laminated composite plates. A variety of numerical results are obtained for the interlaminar normal and shear stresses along the...
Dynamic responses of a rectangular plate under motion of an oscillator using a semi-analytical method
, Article JVC/Journal of Vibration and Control ; Volume 17, Issue 9 , 2011 , Pages 1310-1324 ; 10775463 (ISSN) ; Kargarnovin, M. H ; Ghahremani, A. R ; Sharif University of Technology
Abstract
A semi-analytical method is presented to calculate the dynamic responses of a rectangular plate due to a moving oscillator. In previous analytical solutions of the moving oscillator problem, the elastic distributed structure has usually been modeled by an elastic beam structure. This restrictive assumption is removed in this study by assuming a general plate as two-dimensional elastic distributed structure. The method can be applied for any arbitrary path on the plate. A combination of the Fourier and Laplace transformation as well as the convolution theorem is used to solve the governing differential equations of the problem. A modified integration technique is then presented to solve the...
A precise solution for prediction of fiber-reinforced concrete behavior under flexure
, Article Journal of Zhejiang University: Science A ; Volume 12, Issue 7 , 2011 , Pages 495-502 ; 1673565X (ISSN) ; Ghoddousi, P ; Sharifi, M ; Bahreh, V. M ; Sharif University of Technology
2011
Abstract
This paper presents a precise solution to predict the behavior of steel fiber reinforced concrete (SFRC) under the four point bending test (FPBT). All the force components at the beam section (before and after cracking) are formulated by applying these assumptions: a realistic stress-strain model is used for concrete behavior in compression, a linear response is considered for the uncracked tension region in a concrete constitutive model, and an exponential relationship is proposed as a stress-crack opening in the crack region which requires two parameters. Then the moment capacity of the critical cracked section is calculated by using these forces and satisfying equilibrium law at the...
Free vibration analysis of symmetrically laminated fully clamped skew plates using extended Kantorovich method
, Article Key Engineering Materials, 22 March 2011 through 24 March 2011, Kuala Lumpur ; Volume 471-472 , 2011 , Pages 739-744 ; 10139826 (ISSN) ; 9783037850596 (ISBN) ; Kargarnovin, M. H ; Aghdam, M. M ; Sharif University of Technology
2011
Abstract
In this paper, free vibration analysis of thin symmetrically laminated skew plates with fully clamped edges is investigated. The governing differential equation for skew plate which is a fourth order partial differential equation (PDE) is obtained by transforming the differential equation in Cartesian coordinates into skew coordinates. Based on the multi-term extended Kantorovich method (MTEKM) an efficient and accurate approximate closed-form solution is presented for the governing PDE. Application of the MTEKM reduces the governing PDE to a dual set of ordinary differential equations. These sets of equations are then solved with infinite power series solution, in an iterative manner until...
Non-linear vibration analysis of laminated composite plates resting on non-linear elastic foundations
, Article Journal of the Franklin Institute ; Volume 348, Issue 2 , March , 2011 , Pages 353-368 ; 00160032 (ISSN) ; Fesanghary, M ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
In this study, the homotopy analysis method (HAM) is used to obtain an approximate analytical solution for geometrically non-linear vibrations of thin laminated composite plates resting on non-linear elastic foundations. Geometric non-linearity is considered using von Karman's straindisplacement relations. Then, the effects of the initial deflection, ply properties, aspect ratio of the plate and foundation parameters on the non-linear free vibration is studied. Comparison between the obtained results and those available in the literature demonstrates the potential of HAM for the analysis of such vibration problems, whose governing differential equations include the quadratic and cubic...
Elimination of the effect of bottom-plate capacitors in C-2C DAC using a layout technique
, Article Microelectronics Journal ; Volume 46, Issue 12 , 2015 , Pages 1275-1282 ; 00262692 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Abstract
An efficient layout technique is proposed to eliminate the effect of the bottom-plate capacitors in a C-2C Digital to Analog Converter (DAC). Using this technique, the bottom-plate capacitors of 2C capacitors in the C-2C structure are placed in parallel with 1C capacitors. Then, the effect of the bottom plate capacitors is nulled by modifying the size of the main 1C capacitors. Hence, avoiding the complexity of calibration, this technique can preclude the effect of the bottom-plate to ground capacitance. Statistical simulations prove that the proposed technique is robust to non-ideal effects such as mismatch or parasitic capacitors. A 10-bit C-2C DAC is modeled in COMSOL Multiphysics using...
Nonlinear dynamic analysis of a rectangular plate subjected to accelerated/decelerated moving load
, Article Journal of Theoretical and Applied Mechanics ; Volume 53, Issue 1 , 2015 , Pages 151-166 ; 14292955 (ISSN) ; Mohsenzadeh, R ; Kargarnovin, M. H ; Sharif University of Technology
Polish Society of Theoretical and Allied Mechanics
2015
Abstract
In this paper, nonlinear dynamical behavior of a rectangular plate traveled by a moving mass as well as an equivalent concentrated force with non-constant velocity is studied. The nonlinear governing coupled partial differential equations (PDEs) of motion are derived by energy method using Hamilton's principle based on the large deflection theory in conjuncture with the von-Karman strain-displacement relations. Then Galerkin's method is used to transform the equations of motion into a set of three coupled nonlinear ordinary differential equations (ODEs) which then is solved in a semi-analytical way to get the dynamical response of the plate. Also, by using the Finite Element Method (FEM)...
Modeling, design and fabrication of non-uniform catalyst layers for PEM fuel cells
, Article ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology, FUELCELL 2010, 14 June 2010 through 16 June 2010 ; Volume 1 , 2010 , Pages 697-705 ; 9780791844045 (ISBN) ; Advanced Energy Systems Division ; Sharif University of Technology
Abstract
Catalyst layers are one of the most important parts of the PEM fuel cells and the cell performance is highly related to its structure. Catalyst layers are generally made by uniform distribution of catalyst on carbon cloth or carbon papers to form electrodes. In this paper, the idea of using non-uniform catalyst layer instead of common uniform catalyst layers is presented and simulated by a two-dimensional steady-state computational model. The model accounts for species transport, electrochemical kinetics, charge transport and current density distribution. A fuel cell test stand is designed and built to facilitate experimental validation of the model. Modeling results show that electrical...
The performance of bolted slant endplate connections subjected to temperature increase
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010l ; Volume 2 , July , 2010 , Pages 207-217 ; 9780791849163 (ISBN) ; Talebi, E ; Sharif University of Technology
2010
Abstract
In this paper the main goal is to evaluate the vertical and slant bolted endplate connections performance in steel moment frame structures under thermal effect in elastic field, and by a finite element software. the connections are simulated to complete and verify simple modeling of analytical and numerical analysis of the behavior of vertical and slant bolted endplate connections due to increase in temperature. The results that are obtained from performance of a vertical bolted endplate connection and a slant bolted endplate connection due to increase in temperature will be compared
Contact time study of electrostatically actuated microsystems
, Article Scientia Iranica ; Volume 17, Issue 5 B , SEPTEMBER-OCTOBER , 2010 , Pages 348-357 ; 10263098 (ISSN) ; Rashidian, B ; Ahmadian, M. T ; Sharif University of Technology
2010
Abstract
This paper presents a model to analyze contact phenomenon in microsystems actuated by ramp voltages, which has applications in frequency sweeping. First-order shear deformation theory is used to model dynamical system using finite element method, while finite difference method is applied to model squeeze film damping. The model is validated by static pull-in results. The presented hybrid FEMFDM model is utilized to compute values of contact time and dynamic behavior. Considering this model, effects of different geometrical and mechanical parameters on contact time are studied. The influence of imposing the additional reverse voltage on dynamic characteristics of the system is also...
Nonlinear dynamic analysis of a concrete gravity dam considering an elastoplastic constitutive model for the foundation
, Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 1676-1684 ; 10263098 (ISSN) ; Ghaemian, M ; Sharif University of Technology
Sharif University of Technology
2013
Abstract
Dam failure can result in a catastrophic break followed by a ood wave, often with considerable loss of life or property. One of the main causes of dam failure is loss of shear strength and the existence of discontinuity within the foundation. Dynamic analysis of concrete dams usually considered concrete behavior to be nonlinear and the foundation rock is assumed to be linear. In this study, seismic analysis of a concrete gravity dam was conducted to investigate the effect of the foundation on the nonlinear response. A finite element model of a dam-reservoir-foundation was considered to properly model the foundation as well as dam body nonlinear behaviors. An elasto-plastic formulation was...
Contact time study of microsystems actuated by ramp-input voltages
, Article ASME 2009 International Mechanical Engineering Congress and Exposition, IMECE2009, Lake Buena Vista, FL, 13 November 2009 through 19 November 2009 ; Volume 12, Issue PART A , 2010 , Pages 105-112 ; 9780791843857 (ISBN) ; Rashidian, B ; Ahmadian, M. T ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2010
Abstract
This paper presents a model to analyze contact phenomenon in microsystems, actuated by ramp voltages, which has applications in frequency sweeping. First-order shear deformation theory is used to model dynamical system using finite element method, while finite difference method is applied to model squeeze film damping. The model is validated by static pull-in results. The presented hybrid FEM-FDM model is utilized to compute values of contact time and dynamic behavior. Considering this model, effects of different geometrical and mechanical parameters on contact time are studied. The influence of imposing the additional reverse voltage on dynamic characteristics of the system is also...
Compactness requirements of RBS connections
, Article Advances and Trends in Structural Engineering, Mechanics and Computation - Proceedings of the 4th International Conference on Structural Engineering, Mechanics and Computation, SEMC 2010, 6 September 2010 through 8 September 2010 ; 2010 , Pages 663-666 ; 9780415584722 (ISBN) ; Shahidi, S. G ; Zingoni A ; Sharif University of Technology
Abstract
Flexible steel frame system is the most common structural system for mid-rise buildings. Northridge earthquake is turning point in designing flexible steel frames and their connections. During this earthquake a large number of beam-column connections in such structures were ruptured in a brittle manner. After this earthquake many researches were conducted on a variety of beam-column connections with an aim of improving their behavior during earthquake. One such connection which have been studied extensively both experimentally and analytically is a connection with Reduced Beam Section (RBS). The most important advantage of this connection is its high ductility and its ability to dissipate...
Differential quadrature method for nonlocal nonlinear vibration analysis of a boron nitride nanotube using sinusoidal shear deformation theory
, Article Mechanics of Advanced Materials and Structures ; Volume 23, Issue 11 , 2016 , Pages 1278-1283 ; 15376494 (ISSN) ; Sadatshojaie, A ; Fakhar, M. H ; Sharif University of Technology
Taylor and Francis Inc
2016
Abstract
This article presents a nonlocal sinusoidal shear deformation beam theory (SDBT) for the nonlinear vibration of single-walled boron nitride nanotubes (SWBNNTs). The surrounding elastic medium is simulated based on nonlinear Pasternak foundation. Based on the nonlocal differential constitutive relations of Eringen, the equations of motion of the SWBNNTs are derived using Hamilton's principle. Differential quadrature method (DQM) for the nonlinear frequency is presented, and the obtained results are compared with those predicted by the nonlocal Timoshenko beam theory (TBT). The effects of nonlocal parameter, vibrational modes, length, and elastic medium on the nonlinear frequency of SWBNNTs...
Investigation of hydroelastic effect in analysis of high-speed craft
, Article Ships and Offshore Structures ; Volume 11, Issue 1 , 2016 , Pages 16-24 ; 17445302 (ISSN) ; Seif, M. S ; Tabeshpur, M. R ; Yaakob, O ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
Hydroelastic effect in bottom slamming problem of high-speed craft is one of the most challenging issues in structural design. In this paper, numerical method is used to investigate the hydroelastic effect in bottom-water impact analysis of high-speed monohull craft. Slamming with two viewpoints of rigid and elastic structures (hydroelastic effect) is modelled by coupled computational fluid dynamic (CFD) and finite element method (FEM) techniques. The results showed that considering hydroelastic effect, especially in high-impact speed, reduces the structural deformations and stresses compared with quasi-statistic analysis. The effect of different parameters, such as boundary condition, plate...
Inastantaneous baseline multiple damage detection and localization in an aluminum plate using Lamb waves
, Article 30th Congress of the International Council of the Aeronautical Sciences, 25 September 2016 through 30 September 2016 ; 2016 ; 9783932182853 (ISBN) ; Abedian, A ; Nasiri, M ; Sharif University of Technology
International Council of the Aeronautical Sciences
Abstract
In recent years, new Structural Health Monitoring (SHM) methodologies with a concept of "instantaneous baseline damage detection" are being developed by many researchers. In this context, this paper uses a new method to identify multiple damage in the aluminum plate. For this goal use from spars PZWS sensor network to generate and received guided waves. Ultrasonic waves are generated and measured from all possible different pairs of excitation and sensing transducers. For feature extraction of received signals used from continues wavelet transform. A probabilistic damage diagnostic algorithm based on correlation analysis was investigated to locate single or multiple damages. In this study,...
Numerical study of an innovative SMA based beam-column connection in reducing the seismic response of steel MRF structures
, Article Scientia Iranica ; Volume 23, Issue 5 , 2016 , Pages 2033-2043 ; 10263098 (ISSN) ; Yadegari Farzaneh, A ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
During recent years, Shape Memory Alloys (SMAs) have been effectively used to control the seismic response of structural systems. Recovering the residual strains upon unloading (super-elasticity) or by heating (shape memory effect) is the main characteristic of SMA materials. This paper explores the efficiency of a proposed application of steel & SMA bolts in improving the seismic behavior of connections in steel Moment Resisting Frame (MRF) structures. A new semi-rigid, end-plate, beam-column connection is introduced, which is based on parallel application of steel and austenite-phase SMA bolts. A number of 3-D steel MRF structural models with different numbers of stories and mass...