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eccentricity
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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 ; 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...
Non-linear analysis of disposable knee bracing
, Article Computers and Structures ; Volume 75, Issue 1 , 2000 , Pages 65-72 ; 00457949 (ISSN) ; Khosravi, P ; Sharif University of Technology
2000
Abstract
An approximate method is presented that can be used to determine the non-linear behaviour of a new structural bracing system called the `Disposable Knee Bracing'. In this framing system, a special form of diagonal brace connected to a knee element instead of beam-column joint, is investigated. The diagonal element provides lateral stiffness during moderate earthquakes. However, the knee element is designed to have three plastic joints for dissipation of the energy caused by strong earthquake. This article demonstrates the transformation of a complex problem into a new, practical set of design charts and graphs. First, by studying of the elastic behaviour of the system, a suitable shape and...
Position Error of Resolver in a Closed Loop Control
, M.Sc. Thesis Sharif University of Technology ; 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) ; 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 ; 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 ; 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) ; 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 ; 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 ; 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 ; 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) ; 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) ; 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 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) ; 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 ; 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 ; 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...
Compensation Position Error In Variable Reluctance Resolver
, Ph.D. Dissertation Sharif University of Technology ; Nasiri Gheidari, Zahra (Supervisor)
Abstract
Position sensors are an integral part of electric machine control systems. There are different ways to determine the position. The most common methods are using resolvers or optical encoders. Resolver is the recommended in harsh environments where there is wide temperature variation, vibration, and dust. Despite their good features, resolvers face challenges such as eccentricity, short circuit fault, single-phase disconnection, and non-ideal signal voltage. The Resolver chosen in this research is the variable reluctance resolver with variable air gap length. Although this type of resolvers is cheaper than wound rotor resolvers, but its position error is high under electrical and mechanical...
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) ; 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) ; 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 ; 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
;
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%)...