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    Analytical investigation of torsional mode in symmetric and asymmetric systems with mass or stiffness eccentricity

    , Article Structures ; Volume 27 , 2020 , Pages 1433-1445 Tabeshpour, M. R ; Noorifard, A ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    At the first glance, it seems that asymmetry in geometry, mass, and stiffness cause torsion, while there are systems in which, despite the symmetry in all these parameters, the transferred energy to the torsional mode is more than the translational mode. The main purpose of this research was to study the torsional mode of a symmetric system in terms of geometry, mass, and stiffness, then investigate the effect of mass eccentricity and stiffness eccentricity. This is a fundamental problem and its main applications are in the buildings, automobile industry, and offshore structures. Parametric calculations on the free vibration equation of a completely symmetric system show that in a system... 

    Position Error of Resolver in a Closed Loop Control

    , M.Sc. Thesis Sharif University of Technology Khajueezadeh Ravari, Mohammad Sadegh (Author) ; Nasiri Gheidari, Zahra (Supervisor)
    Abstract
    Permanent Magnet Synchronous Motors (PMSMs) are more conventional and widely employed in Electric Vehicles (EVs) applications. The rotor position performed an essential role through PMSMs drive; therefore, any deviation in the detected position will be evaded in coordinate transformations, originating from external or inherence sources. Subsequently, the discussed faults will be conducted to three-phase currents and output torque through erroneous transformations. Resolver’s estimated rotor position due to fault occurrence will be defined as aggregating ideal and non-ideal components. Moreover, based on inherence periodic in resolvers’ principle, non-ideal components could be written by the... 

    Modified eccentric connectivity polynomial of some graph operations

    , Article Carpathian Journal of Mathematics ; Volume 28, Issue 2 , 2012 , Pages 247-256 ; 15842851 (ISSN) Ghorbani, M ; Hosseinzadeh, M. A ; Diudea, M. V ; Ashrafi, A. R ; Sharif University of Technology
    2012
    Abstract
    The modified eccentricity connectivity polynomial of a connected graph G is defined as Ξ(G; x)=Σ u∈V(G)d G(u)x ε′G (u), where ε′ G(u)=Σ v∈NG(u)εG(u)and d G(u) is the degree of u in G. In this paper modified eccentric connectivity polynomial is computed for several classes of composite graphs  

    Online static/dynamic eccentricity fault diagnosis in inverter-driven electrical machines using resolver signals

    , Article IEEE Transactions on Energy Conversion ; Volume 35, Issue 4 , May , 2020 , Pages 1973-1980 Lasjerdi, H ; Nasiri Gheidari, Z ; Tootoonchian, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Abstract
    Inverter driven electrical machines need resolver for position estimation and efficient electronic commutations. In this paper, the resolver signals are also used for the purpose of mechanical fault diagnosis. Therefore, a comprehensive procedure based on winding function (WF) method is presented to propose a noninvasive index to identify the mechanical fault's type (static/dynamic eccentricity) and even its percentage. In this regard, once the resolver signals are measured and saved in health condition. Then, during the operation of the motor, calculating the proposed index using the healthy and faulty signals leads to predict the fault type and its percentage. The success of the proposed... 

    Investigating the Response Modification Factor of 3-D Steel Braced/Moment-Resisting Frames with Irregularity in Plan

    , M.Sc. Thesis Sharif University of Technology Rezazadeh, Mohsen (Author) ; Khonsari, Vahid (Supervisor)
    Abstract
    Study of former earthquakes damages reveals that irregular structures are more susceptive to failure than regular ones. Irregular structures are classified into two categories, namely those with irregularity in elevation and the ones with irregularity in plan. Besides, one of the crucial parameters in working out the earthquake’s equivalent static load is response modification coefficient (R). Based on the type of seismic lateral force-resisting system, this parameter can have various values. In this research, using nonlinear static analysis, the response modification coefficient of a great number of 3-D steel frames of 5, 7 and 9 m spans and having 1 to 10 stories with various... 

    Position error calculation of linear resolver under mechanical fault conditions

    , Article IET Science, Measurement and Technology ; Volume 11, Issue 7 , 2017 , Pages 948-954 ; 17518822 (ISSN) Daniar, A ; Nasiri-Gheidari, Z ; Tootoonchian, F ; Sharif University of Technology
    Abstract
    Position sensors are inseparable part of motion control systems. Linear resolvers (LRs) are electromagnetic position sensors that are suitable for high vibration, polluted environments. The accuracy of their detected position can be affected by different mechanical faults. In this study, variety of possible mechanical faults along with their mathematical index in LRs is introduced. Static eccentricity, dynamic eccentricity, inclined mover and run out error are the presented mechanical faults that are discussed independently and simultaneously. Then, three-dimensional non-linear, time-stepping finite element method is employed to investigate the performance of the studied resolver under... 

    Modeling of eccentric nanoneedle in trolling-mode atomic force microscope

    , Article Microscopy Research and Technique ; 2020 Chahari, M ; Sajjadi, M ; Sharif University of Technology
    Wiley-Liss Inc  2020
    Abstract
    Limitations on installation of a standard TR-AFM nanoneedle can have unpredictable effects on dynamics of system. Therefore, it is crucial to pay close attention to the position and geometry of mounted nanoneedle when deriving the mathematical model. During TR-AFM fabrication process, the nanoneedle may not always deposit precisely at the middle of AFM tip, which would result in coupled bending-torsion modes in the dynamical operation of system. In this paper, we investigate the effect of eccentric nanoneedle in dynamic response of TR-AFM. To address this issue, a continuous mathematical model is developed. This model accounts for eccentric nanoneedle which can address the couplings in... 

    Seismic performance evaluation of deficient steel moment-resisting frames retrofitted by vertical link elements

    , Article Structures ; Volume 26 , August , 2020 , Pages 724-736 Mohsenian, V ; Filizadeh, R ; Ozdemir, Z ; Hajirasouliha, I ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    In many earthquake prone regions in developing countries, substandard steel moment resisting frame (SMRF) systems pose a profound danger to people and economy in the case of a strong seismic event. Eccentric bracing systems with replaceable vertical links can be utilized as an efficient and practical seismic retrofitting technique to reduce future earthquake damages to such structures. This paper aims, for the first time, to demonstrate the efficiency of eccentric bracing systems with vertical links as a seismic retrofitting technique for the SMRF structures with WCSB and to develop fragility curves for such structures. To achieve this aim, first, the effect of the vertical links on the... 

    VM link element for consideration of shear-flexural interaction

    , Article 10th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2010, Bangkok, 3 August 2006 through 5 August 2006 ; Volume 2 , 2006 , Pages 149-154 Erfani, S ; Kazemi, M. T ; Sharif University of Technology
    2006
    Abstract
    A mixed shear-flexural beam element, which is called VM link element, is introduced. Dissimilar multi-surfaces in the shear-flexural space and non zero off diagonal components in flexibility matrixes are used for more realistic modeling of inelastic shear-flexural interaction. For preventing of intersecting among the yield surfaces, a new non-associated flow rule and a new kinematic hardening rule are developed. Capability of this element is examined for shear links used in eccentrically braced frames analysis for cyclic loading. It is shown that, the proposed link element is in a good agreement with the existing test results  

    Modeling of eccentric nanoneedle in trolling-mode atomic force microscope

    , Article Microscopy Research and Technique ; Volume 84, Issue 4 , 2021 , Pages 639-655 ; 1059910X (ISSN) Chahari, M ; Sajjadi, M ; Sharif University of Technology
    John Wiley and Sons Inc  2021
    Abstract
    Limitations on installation of a standard TR-AFM nanoneedle can have unpredictable effects on dynamics of system. Therefore, it is crucial to pay close attention to the position and geometry of mounted nanoneedle when deriving the mathematical model. During TR-AFM fabrication process, the nanoneedle may not always deposit precisely at the middle of AFM tip, which would result in coupled bending-torsion modes in the dynamical operation of system. In this paper, we investigate the effect of eccentric nanoneedle in dynamic response of TR-AFM. To address this issue, a continuous mathematical model is developed. This model accounts for eccentric nanoneedle which can address the couplings in... 

    Investigating the behavior of circular concrete filled PVC tube columns under concentric and eccentric load using FEM

    , Article Asian Journal of Civil Engineering ; Volume 22, Issue 4 , 2021 , Pages 589-603 ; 15630854 (ISSN) Alinejad, A ; Khaloo, A ; Hassanpour, S ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    Abstract
    The purpose of this research is to investigate the response of concrete-filled composite tube column under concentric and eccentric loads. To evaluate the influence of PVC pipe on the behavior of concrete-filled composite tubes, concrete-filled PVC pipe (CFPT) were modeled by ABAQUS software. The results demonstrate that the presence of the PVC pipe makes the concrete column more ductile and have a significant effect on the stress–strain curve of the CFPT after the peak strength, in a way that the confinement increased by raising the thickness of PVC pipe, but the confinement effect of the PVC pipe decreased by the increment of the column diameter and compressive strength of the concrete... 

    Investigating the Response Reduction Factor of Steel 3-D Braced Frames with Eccentricity

    , M.Sc. Thesis Sharif University of Technology Afshari, Behrouz (Author) ; Khonsari, Vahid (Supervisor)
    Abstract
    Studying the performance of irregular structures in past earthquakes reveals that due to their severe vulnerability, we need to accurately assess the behavioral characteristics of such structures. On the other hand, all existing seismic codes recommend the use of response modification factor to determine the base shear, design forces of the members, and the design drift ratios, which seem to have limited comprehensiveness. Moreover, the response modification factor for a structural system is discussed in a general manner and the effect of factors such as number of bays, number of stories, span length, story height and irregularities are not considered. In this research, the effects of... 

    Electrical and Eccentricity Fault Diagnose in Wound Rotor Resolvers

    , M.Sc. Thesis Sharif University of Technology Lasjerdi, Hamed (Author) ; Nasiri Gheidari, Zahra (Supervisor) ; Totonchian, Farid (Co-Supervisor)
    Abstract
    Resolver is the recommended position sensor in harsh environments where there is wide temperature variation, vibration, and dust. Resolvers are divided into two groups: Wound-Rotor (WR) resolvers and Variable Reluctance (VR) ones. The most commercial resolvers are WR resolvers that they have 2-phase, orthogonal, signal windings on their stator and a single-phase excitation winding on their rotor. Due to the electromechanical structure of the resolver, the mechanical and electrical faults of electrical machines are expected in resolvers. Therefore, in this dissertation, the effect of mentioned faults in WR resolvers was investigated.In this dissertation, a non-invasive method with the help of... 

    An optimized axial flux variable reluctance resolver with concentric windings

    , Article 24th Iranian Conference on Electrical Engineering, ICEE 2016, 10 May 2016 through 12 May 2016 ; 2016 , Pages 1284-1290 ; 9781467387897 (ISBN) Tootoonchian, F ; Nasiri Gheidari, Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    Radial flux variable reluctance resolvers (RFVR2s) are widely used in variety of applications. However, they suffer from an intrinsic error which is called static eccentricity (SE). Although most of the errors in the resolvers can be suppressed using electronic methods in resolver to digital (R/D) converters, static misalignment is an exception. In this paper an axial flux configuration is proposed for variable reluctance (VR) resolvers with concentric windings. Then the proposed structure is optimized to achieve the minimum sensitivity of accuracy against SE. The performance of the presented structure, so called axial flux variable reluctance resolver (AFVR2), is validated using 3-D time... 

    Seismic performance assessment of eccentrically braced steel frames with energy-absorbing links under sequential earthquakes

    , Article Journal of Building Engineering ; Volume 33 , 2021 ; 23527102 (ISSN) Mohsenian, V ; Filizadeh, R ; Hajirasouliha, I ; Garcia, R ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    Recent studies have indicated the need of considering aftershocks in the seismic design/assessment of structures. This article investigates the effect of sequential mainshock and aftershock earthquakes on eccentrically braced steel frames with vertical energy-absorbing links. To achieve this, 4, 8 and 12-storey frame buildings are modelled in Perform3D® software considering non-linear behaviour of materials and components. The frames are subjected to a set of 12 main earthquake records corresponding to the required hazard level, and then subsequent aftershocks are applied using incremental dynamic analysis (IDA). To reduce the computational cost, an alternative approach is also adopted by... 

    Seismic Rehabilitation of Reinforced Concrete Structures Using Eccentric Steel Bracing

    , M.Sc. Thesis Sharif University of Technology Rajaee Mohammadiye, Kourosh (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    Abstract
    The seismic performance of a low-rise nonductile reinforced concrete (RC) building rehabilitated using eccentric steel bracing is investigated. At first three-story building was Modeled using sap 2000 computer program then analyzed and getting the results. The effectiveness of the eccentric steel bracing in rehabilitating the building was examined. The effect of distributing the steel bracing over the height of the RC frame on the seismic performance of the rehabilitated building was studied. The behavior of the nonductile RC frame members is represented by a beam–column element capable of modeling the strength deterioration and the effect of the axial force on the yield moment and the... 

    Investigation on Performance of Active Tuned Mass Dampers on Vibration Control of Three Dimentional Structures

    , M.Sc. Thesis Sharif University of Technology Shahrokhi, Sasan (Author) ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
    Abstract
    Tuned Mass Dampers(TMD) are among the most studied passive or active control devices that have been used around the world to control the lateral vibration of different building structures. On the other hand, since 2-D structural models are not appropriate for estimating the true response of the eccentric structures, application of 3-D models have been considered for determining their seismic-induced coupled lateral-torsional behavior. In this research, the performance of the Active Tuned Mass Dampers (ATMD) in controlling the seismic response of 3-D structural models was investigated. Three structural models with 4, 8 and 15 number of stories and 3 different eccentricities (0, 10% and 15%)... 

    Investigating of the Behavior of the Column Base Plate with Eccentirisity Using FEM

    , M.Sc. Thesis Sharif University of Technology Moeini, Amin (Author) ; Vafaei, Abolhassan (Supervisor) ; Mofid, massoud (Co-Advisor)
    Abstract
    Base plate is one of the crucial elements in steel structures which transfer force from column to foundation and also prevent stress concentration in jointing area between them. For investigating the behavior of base plate under different caseloads such as axial, transverse and earthquake loads, it is necessary to consider all the involved elements including column, base plate, foundation, anchor rods and also interaction between these elements. In this study the connection between column and base plate, base plate and foundation are analyzed thoroughly. The behavior of base plate with a box type column with and without stiffener under the static loads is analyzed using finite element... 

    An Investigation of the Effects of Zipper Strut on the Cost and Energy Dissipation Capacity of Concentrically & Eccentrically Chevron Braced Systems

    , M.Sc. Thesis Sharif University of Technology Dehghany Yazdeli, Mahdi (Author) ; Ahmadizadeh, Mehdi (Supervisor)
    Abstract
    Concentric and eccentric chevron braces are among the more economical lateral force resisting systems for structures. However, chevron braced systems are prone to concentration of damage in a single story and formation of soft stories when buckling occurs in the bracing elements. This leads to a gradual loss in the structural performance, particularly as the height of the structure increases. One of the most notable methods to alleviate this problem and improve the structural performance is the addition of zipper struts to concentrically chevron braced frames that are known to improve the distribution of plastic energy dissipation along the height of the structure. While this usually... 

    Progressive Collapse Due to Sudden Column Removal in Steel Moment and Eccentric Braced Frames

    , M.Sc. Thesis Sharif University of Technology Moosadoost, Ali Asghar (Author) ; Khaloo, Alireza (Supervisor) ; Kazemi, Mohammad Taghi (Co-Supervisor)
    Abstract
    With increasing population and lack of habitable spaces, the building heights increased in cities around the world. Placing components of a structure in tandem may cause a permanent failure of the members due to strength reduction. During recent years, this kind of failure occurred in different places of the world, and is called progressive collapse. There are some various samples of the progressive collapse which all are good samples of failures such as building failure in Ronan Point in the UK, Twin Towers or the world trade center in NY, and Pentagon building. According to these issues, different institutions codified guidelines and codes in this field such as Department of Defense as DoD...