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structural-dynamics
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Novel aspects of elastic flapping wing: analytical solution for inertial forcing
, Article Advances in Aircraft and Spacecraft Science ; Volume 5, Issue 3 , May , 2018 , Pages 335-348 ; 2287528X (ISSN) ; Pourtakdoust, S. H ; Bighashdel, A ; Sharif University of Technology
Techno Press
2018
Abstract
The structural dynamics (SD) behavior of Elastic Flapping Wings (EFWs) is investigated analytically as a novel approach in EFWs analysis. In this regard an analytical SD solution of EFW undergoing a prescribed rigid body motion is initially derived, where the governing equations are expressed in modal space. The inertial forces are also analytically computed utilizing the actuator induced acceleration effects on the wing structure, while due to importance of analytical solution the linearity assumption is also considered. The formulated initial-value problem is solved analytically to study the EFW structural responses, where the effect of structure-actuator frequency ratio,...
Evaluation of vierendeel peripheral frame as supporting structural element for prevention of progressive collapse
, Article Steel and Composite Structures ; Volume 26, Issue 5 , March , 2018 , Pages 549-556 ; 12299367 (ISSN) ; Omidi, H ; Sharif University of Technology
Techno Press
2018
Abstract
Progressive building collapse occurs when failure of a structural component leads to the failure and collapse of surrounding members, possibly promoting additional failure. Global system collapse will occur if the damaged system is unable to reach a new static equilibrium configuration. The most common type of primary failure which led to the progressive collapse phenomenon, is the sudden removal of a column by various factors. In this study, a method is proposed to prevent progressive collapse phenomena in structures subjected to removal of a single column. A vierendeel peripheral frame at roof level is used to redistribute the removed column’s load on other columns of the structure. For...
Dynamic response of euler-Bernoulli, Timoshenko and higher-Order beams under a moving mass via RKPM
, Article 7th European Conference on Structural Dynamics, EURODYN 2008, 7 July 2008 through 9 July 2008 ; 2008 ; 9780854328826 (ISBN) ; Kiani, K ; Mehri, B ; Sharif University of Technology
University of Southampton, Institute of Sound Vibration and Research
2008
Abstract
Discrete motion equations of an Euler-Bernoulli, Timoshenko and higher-order beams under a moving mass are derived for different boundary conditions. To this end, the reproducing kernel particle method (RKPM) has been utilized for spatial discretization, beside the extension of Newmark-β method for time discretization of the beams motion equations. The effects of significant parameters such as the beam's slenderness and velocity of the moving mass on the maximum deflection and bending moment of different beams are studied in some details. The results indicate the existence of a critical beam's slenderness mostly as a function of beam's boundary conditions, in which for slenderness lower than...
On the Stability of Rotating Cylinder Conveying Flow in an External Fluid Medium
, M.Sc. Thesis Sharif University of Technology ; Dehghani Firoozabadi, Rouhollah (Supervisor)
Abstract
The present study aims at investigating the stability of flexible spinning cylinders conveying flow in an external fluid Medium. Using the linearized Navier-Stokes equations for the flow, a two-dimensional model is developed governing the fluid motion. The resultant force exerted on the flexible cylinder wall due to the fluid interactions is calculated as a function of the lateral acceleration. Applying the Hamilton principle, the governing equations of flexural vibration of the rotary flexible cylinder mounted on simply supported axles are derived. Having the forces due to the conveying fluid calculated and substituting into the governing equations, a coupled field governing equations of...
Dynamic response of a delaminated beam due to a moving force
, Article International Conference on Noise and Vibration Engineering 2012, ISMA 2012, including USD 2012: International Conference on Uncertainty in Structure Dynamics, 17 September 2012 through 19 September 2012 ; Volume 4 , September , 2012 , Pages 3189-3200 ; 9781622768257 (ISBN) ; Kargarnovin, M. H ; Ahmadian, M. T ; Abedi, M ; Katholieke Universiteit Leuven ; Sharif University of Technology
Katholieke Universiteit Leuven
2012
Abstract
This paper deals with the dynamic analysis of a delaminated Bernoulli-Euler beam with constrained model under the action of an external moving force. The beam is analyzed as four interconnected sub-beams using the delamination as their boundaries. The continuity and compatibility conditions are satisfied between adjoining beams. An analytical solution is presented in a basis of the series expansion of the unknown deflection. The delaminated beam response differences with the healthy beam have been investigated. Effect of the parameters like the moving speed of the force and the size, depth and spanwise location of the delamination on the dynamic response of the beam has been studied....
Seismic performance evaluation and design of steel structures equipped with dual-pipe dampers
, Article Journal of Constructional Steel Research ; Volume 122 , 2016 , Pages 25-39 ; 0143974X (ISSN) ; Maleki, S ; Sharif University of Technology
Elsevier Ltd
Abstract
Dual-pipe damper (DPD) is a metallic yielding device for passive control of structures, introduced recently by the authors. The objective of the current study is to provide guidelines for implementing DPDs in actual steel buildings, evaluate and compare their performance against other metallic dampers. In this study, a representative load-displacement model for DPDs is proposed for the first time, and assessed based on previous experimental cyclic tests. Guidelines for the design of DPD devices are also presented. Three steel moment resisting frames of 5, 10 and 20 stories are designed and then equipped with DPDs of various properties. The responses of the frames to seven earthquake...
Generation of transfer functions of subsystems using the test results of the whole system
, Article Conference Proceedings of the Society for Experimental Mechanics Series, 9 February 2009 through 12 February 2009 ; 2009 ; 21915644 (ISSN) ; 9781605609614 (ISBN) ; Albooyeh, A. R ; Ashory, M. R ; Khatibi, M. M ; Sharif University of Technology
Abstract
This paper presents a new experimental-numerical method for deriving the transfer functions of a half-automobile model, containing: chassis, body, engine, engine mount and steering wheel, with five degrees of freedom. In this method different parts of system are not required to be disassembled from the main system and the transfer functions of subsystem are obtained through testing of the whole system. This method is based on the experimental results and does not need a mathematical model of the half-automobile. In this method, transfer functions of various parts of chassis are calculated through obtaining the response of secondary elements mounted on the chassis to the displacement input...
A new self-powered electromagnetic damper for structural vibration control
, Article Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2017, 26 March 2017 through 29 March 2017 ; Volume 10168 , 2017 ; 0277786X (ISSN); 9781510608214 (ISBN) ; Chang, C. C ; Fiberguide Industries; Frontiers Media; OZ Optics, Ltd.; Polytec, Inc.; The Society of Photo-Optical Instrumentation Engineers (SPIE) ; Sharif University of Technology
SPIE
2017
Abstract
This paper presents a new self-powered hybrid electromagnetic damper that can mitigate vibration of a structure. The damper is able to switch between a power-regenerative passive mode and a semi-active mode depending on the power demand and capacity. The energy harvested in the passive mode due to suppression of vibration is employed to power up the sensing and electronic components necessary for the semi-active control. This provides a hybrid control capability that is autonomous in terms of its power requirement. The device mechanism and the circuitry that can realize this self-powered electromagnetic damper are described in this paper. The parameters that determine the device feasible...
Reliable nonlinear hybrid simulation using modified operator splitting technique
, Article Structural Control and Health Monitoring ; 2018 ; 15452255 (ISSN) ; Tasnimi, A. A ; Ahmadizadeh, M ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
One of the main challenges of hybrid simulation is developing integration methods that not only provide accurate and stable results but also are compatible with the hybrid simulation circumstances. This paper presents a novel enhanced integration technique for hybrid simulation termed “modified operator splitting” (MOS) method. The main aim of the MOS technique is to improve the precision of the operator splitting (OS) method by reducing the corrector step length, where initial stiffness is utilized instead of actual stiffness. For this purpose, a new algorithm is proposed, which makes a more precise estimation of the predictor displacement; thus minimizes the effect of the corrective...
Analytical structural behaviour of elastic flapping wings under the actuator effect
, Article Aeronautical Journal ; Volume 122, Issue 1254 , 2018 , Pages 1176-1198 ; 00019240 (ISSN) ; Pourtakdoust, S. H ; Bighashdel, A ; Sharif University of Technology
Cambridge University Press
2018
Abstract
The effect of inertial forces on the Structural Dynamics (SD) behaviour of Elastic Flapping Wings (EFWs) is investigated. In this regard, an analytical modal-based SD solution of EFW undergoing a prescribed rigid body motion is initially derived. The formulated initial-value problem is solved analytically to study the EFW structural responses, and sensitivity with respect to EFWs' key parameters. As a case study, a rectangular wing undergoing a prescribed sinusoidal motion is simulated. The analytical solution is derived for the first time and helps towards a conceptual understanding of the overall EFW's SD behaviour and its analysis required in their designs. Specifically, the EFW transient...
Experimental identification of closely spaced modes using NExT-ERA
, Article Journal of Sound and Vibration ; Volume 412 , 2018 , Pages 116-129 ; 0022460X (ISSN) ; Momeni Massouleh, S. H ; Hajirezayi, S ; Bahai, H ; Sharif University of Technology
Academic Press
2018
Abstract
This article presents a study on the capability of the time domain OMA method, NExT-ERA, to identify closely spaced structural dynamic modes. A survey in the literature reveals that few experimental studies have been conducted on the effectiveness of the NExT-ERA methodology in case of closely spaced modes specifically. In this paper we present the formulation for NExT-ERA. This formulation is then implemented in an algorithm and a code, developed in house to identify the modal parameters of different systems using their generated time history data. Some numerical models are firstly investigated to validate the code. Two different case studies involving a plate with closely spaced modes and...
Reliable nonlinear hybrid simulation using modified operator splitting technique
, Article Structural Control and Health Monitoring ; Volume 26, Issue 1 , 2019 ; 15452255 (ISSN) ; Tasnimi, A. A ; Ahmadizadeh, M ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
One of the main challenges of hybrid simulation is developing integration methods that not only provide accurate and stable results but also are compatible with the hybrid simulation circumstances. This paper presents a novel enhanced integration technique for hybrid simulation termed “modified operator splitting” (MOS) method. The main aim of the MOS technique is to improve the precision of the operator splitting (OS) method by reducing the corrector step length, where initial stiffness is utilized instead of actual stiffness. For this purpose, a new algorithm is proposed, which makes a more precise estimation of the predictor displacement; thus minimizes the effect of the corrective...
Charge asymmetry effect in ion transport through angstrom-scale channels
, Article Journal of Physical Chemistry C ; Volume 123, Issue 2 , 2019 , Pages 1462-1469 ; 19327447 (ISSN) ; Fan, J ; Esfandiar, A ; Zhu, Y ; Wu, H ; Wang, F ; Sharif University of Technology
American Chemical Society
2019
Abstract
Structural and dynamic properties of ions confined in nanoslits are crucial to understand the fundamental mechanism underlying a wide range of chemical and biological phenomena. K + and Cl - show similar ion mobilities in a bulk aqueous solution, whereas they exhibit a remarkable difference when transporting through an angstrom-scale channel. Our molecular dynamics simulations uncover that such discrepancy originates from the subtle differences in their hydration structures and preferable locations across the channel. Opposite charge causes different water dipolar orientations around ions, mediating the distance and tribological interactions between hydrated ions and channel's walls....
Reliable nonlinear hybrid simulation using modified operator splitting technique
, Article Structural Control and Health Monitoring ; Volume 26, Issue 1 , 2019 ; 15452255 (ISSN) ; Tasnimi, A. A ; Ahmadizadeh, M ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
One of the main challenges of hybrid simulation is developing integration methods that not only provide accurate and stable results but also are compatible with the hybrid simulation circumstances. This paper presents a novel enhanced integration technique for hybrid simulation termed “modified operator splitting” (MOS) method. The main aim of the MOS technique is to improve the precision of the operator splitting (OS) method by reducing the corrector step length, where initial stiffness is utilized instead of actual stiffness. For this purpose, a new algorithm is proposed, which makes a more precise estimation of the predictor displacement; thus minimizes the effect of the corrective...
Quench dynamics in one-dimensional optomechanical arrays
, Article Physical Review A ; Volume 101, Issue 2 , 2020 ; Marquardt, F ; Sharif University of Technology
American Physical Society
2020
Abstract
Nonequilibrium dynamics induced by rapid changes of external parameters is relevant for a wide range of scenarios across many domains of physics. For waves in spatially periodic systems, quenches will alter the band structure and generate new excitations. In the case of topological band structures, defect modes at boundaries can be generated or destroyed when quenching through a topological phase transition. Here, we show that optomechanical arrays are a promising platform for studying such dynamics, as their band structure can be tuned temporally by a control laser. We study the creation of nonequilibrium optical and mechanical excitations in one-dimensional arrays, including a bosonic...
Numerical simulation of structural dynamics using a high-order compact finite-difference scheme
, Article Applied Mathematical Modelling ; Volume 40, Issue 3 , 2016 , Pages 2431-2453 ; 0307904X (ISSN) ; Parseh, K ; Sharif University of Technology
Elsevier Inc
Abstract
A high-order compact finite-difference scheme is applied and assessed for the numerical simulation of structural dynamics. The two-dimensional elastic stress-strain equations are considered in the generalized curvilinear coordinates and the spatial derivatives in the resulting equations are discretized by a fourth-order compact finite-difference scheme. For the time integration, an implicit second-order dual time-stepping method is utilized in which a fourth-order Runge-Kutta scheme is used to integrate in the pseudo-time level. The accuracy and robustness of the solution procedure proposed are investigated through simulating different two-dimensional benchmark test cases in structural...
Development of a high-order compact finite-difference total Lagrangian method for nonlinear structural dynamic analysis
, Article Applied Mathematical Modelling ; Volume 63 , 2018 , Pages 179-202 ; 0307904X (ISSN) ; Hejranfar, K ; Sharif University of Technology
Elsevier Inc
2018
Abstract
A high-order compact finite-difference total Lagrangian method (CFDTLM) is developed and applied to nonlinear structural dynamic analysis. The two-dimensional simulation of thermo-elastodynamics is numerically performed in generalized curvilinear coordinates by taking into account the geometric and material nonlinearities. The spatial discretization is carried out by a fourth-order compact finite-difference scheme and an implicit second-order accurate dual time-stepping method is applied for the time integration. The accuracy and capability of the proposed solution methodology for the nonlinear structural analysis is investigated through simulating different static and dynamic benchmark...
Identification of inelastic shear frames using the prandtl-ishlinskii model
, Article Scientia Iranica ; Volume 16, Issue 1 A , 2009 , Pages 43-49 ; 10263098 (ISSN) ; Joghataie, A ; Sharif University of Technology
2009
Abstract
In this paper, a new method is proposed for identification of inelastic shear frame structures with hesteresis, using data collected on their dynamic response. It uses the. Prandtl-Ishlinskii rate independent model for hysteresis, which was originally used in the field of plasticity and ferromagnetism. The proposed identification method is capable, of identifying the. mass, damping and restoring force of a frame, structure, which can be. used in forming the. equations of motion of the.frame. By solving the equations of motion, the. dynamic response is predicted. The method is based on the.combined use. of Quadratic Programming (QP) and Genetic Algorithms (GA). First, assuming a set of...
Aeroelastic Analysis of a Complete Aircraft Via State Space Modeling
, M.Sc. Thesis Sharif University of Technology ; Keshavarz Haddad, Gholamreza (Supervisor)
Abstract
This dissertation presents aeroelastic stability analysis (flutter) pertinent to the complete flexible aircraft based on analytical dynamics, structural dynamics and aerodynamics. The unified formulation is based on fundamental principles and incorporates in a natural manner both rigid body motions of the aircraft as a whole and elastic deformations of the flexible components (fuselage, wing and empennage), as well as the aerodynamic, propulsion and gravity forces. The aircraft motion is described in terms of three translations and three rotations of a reference frame attached to the undeformed fuselage, and acting as aircraft body axes, and elastic displacements of each of the flexible...
Developing a Compact Finite Difference Method for Solving Fluid - Solid Interaction in Incompressible Flow
, M.Sc. Thesis Sharif University of Technology ; Hejranfar, Kazem (Supervisor)
Abstract
In this study, fluid-solid interaction (FSI) is simulated computationally by using a high-order accurate numerical method. The two-dimensional incompressible viscous flows are considered in the fluid domain. The primary problem with solutions of the incompressible Navier–Stokes equations is the difficulty of coupling changes in the velocity field with changes in the pressure field while satisfying the continuity equation. Herein, the artificial compressibility method is used to overcome this difficulty. Preconditioning is implemented to reduce the stiffness of the system of equations to increase the convergence rate of the solution. Using preconditioning, physical solutions even at low...