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Scattering of SH-Waves by a Cylindrical Multi Inhomogeneity Embedded in a Piezo-Electromagnetic Medium Using an Analytical Innovative Micromechanical Approach
, Ph.D. Dissertation Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
This work examines the problem of the fully coupled magneto-electro-elastic (MEE) scattering of SH-waves incident upon a heterogeneous MEE scatterer which is embedded in an unbounded medium. The scatterer consists of a circular core and a circular encapsulator with eccentricity. All three regions: the core, encapsulator, and the surrounding matrix have distinct MEE properties and fully coupled constitutive relations. The generated coupled MEE fields coexist simultaneously in all these regions without resort to any simplifying assumptions. The precise description of the multifunctionality involves the solution of three fully coupled partial differential equations in three different regions....
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...
Developing the MIDA Method for Mid-Rise Structures with Non-symmetrical Plan
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masood (Supervisor)
Abstract
Performance based design becomes an effective method for estimating seismic demands of buildings. Incremental dynamic analysis (IDA) based on a nonlinear response time history analysis (NL-RHA) is considered to be the most accurate method in seismic demand calculations. However, modal incremental dynamic analysis (MIDA), based on the equivalent single degree-of-freedom (SDF) oscillator, is also often used in studying structural engineering performances. The MIDA procedure for estimating seismic demands is extended to unsymmetric-plan buildings. In the MIDA procedure, the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by...
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%)...
Investigating of the Behavior of the Column Base Plate with Eccentirisity Using FEM
, M.Sc. Thesis Sharif University of Technology ; 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...
Nonlinear Quantification and Seismic Evaluation of EBF Disposal Systems in Mid-story Structures
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masoud (Supervisor)
Abstract
In the present study it was intended to evaluate the seismic performance of multi-story EBF structures for designing. When adopting this method, parametric studies are carried out based on the nonlinear performance of such systems whiting the framework of nonlinear static and dynamic analyses. In lines with seismic strengthening of such structures, this study tries to reassess the performance of these systems through increasing ductility and replacing bracing frames with energy damper and special seismic systems. As a result, a fuse type performance is created to protect the other elements of the structure. This study describes the seismic strengthening of this type of dampers using simple...
Investigating the Effect of Reinforced Concrete Wall Positioning, with Irregular Plans
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masoud (Supervisor)
Abstract
Previously, numerous studies were carried out on the shear walls and important information are available in various fields, including wall design with various sections, wall design in areas with high seismicity risk, issues related to the reinforcement of boundary element and etc. In the design codes of reinforced concrete structures in the field of seismic design, some criteria for reinforcement of boundary element in the walls were conducted, but these codes do not answer to designers to arrange the wall with or without eccentricity with respect to column or the effect of separation of wall from the column. Due to the fact that we have a powerful software such as ETABS, design of shear...
Performance Analysis, Optimization and Prototyping of Doubly Salient PM Vernier Generators
, M.Sc. Thesis Sharif University of Technology ; Oraee, Hashem (Supervisor) ; Nasiri-Gheidari, Zahra (Supervisor)
Abstract
In this thesis, no-load and full-load performance of Permanent Magnet Vernier Generators (PMVGs) is investigated in fully-aligned condition and under different types of mechanical faults. The studied mechanical faults are Static Eccentricity (SE), Dynamic Eccentricity (DE), Inclined Rotor (IR), and Run-out (RO). Furthermore, an analytical model is also developed to calculate the permeance of the air-gap and the induced voltages in the health machine and under studied mechanical faults. Then, 2-D and 3-D non-linear, time stepping finite element method is utilized for performance evaluation of the generator in no-load and full-load (with resistive, inductive and capacitive loads). In continue,...
Investigation on Nonlinear Behavior of base Plates with Triangular Hardener under Axial Load and Bending Moment
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
The paper presents the results of nonlinear analysis of steel base plates subjected to different combinations of axial and bending forces. The bending forces range from small moments representing small eccentricities to large moments from seismic actions. The results of nonlinear analysis are done on three samples of the column base plate with large moment, small moment and compression axial force are compared to the results of the code. The parameters investigated in this study are as follows: distribution of strain and stresses in the concrete foundation and the steel plate, the strains and stresses in the tensile anchorage bolts, the location of neutral curve under the base plate, the...
Investigating the Behavior of a Type of Energy Absorbing Bracing System
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)
Abstract
Bracing Systems are usually a set of inclined members that are embedded in structures to resist lateral forces and control lateral displacements. There are different types and behaviors for Bracing Systems depending on the way of assembling and locating them in the structure. Braced Frames, such as Concentrically Braced Frames (CBFs), generally have high stiffness and low ductility. Another Type of Braced Frames is Eccentrically Braced Frames (EBFs) which improves CBFs by establishing suitable ductility as well as stiffness. Inelastic behavior of Links involved with EBFs caused this in EBFs. Nevertheless, these systems have no efficiency in next earthquake, because links are parts of beams...
Seisimc Performance of Dutile End Diaphragms For Slab-on-girder Steel Bridges
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
This thesis illustrates the typical seismic retrofitting of bridges using a model governing transverse seismic response of retrofitted bridges by simplified analytical models of the end diaphragms based on the fundamental dynamic concept as well as previous research works. For three types of ductile diaphragm devices such as Eccentrically Braced Frames (EBF), Triangular-plate Added Damping and Stiffness Devices (TADAS) and Chevron Knee Bracing (CKB)and Shear Panel System(SPS), finite element nonlinear analytical models are developed in separate flexural and shear yielding modes, and the capability of the proposed finite element models is ascertained.The IDA (Incremental Dynamic Analyses) are...
Nonlinear Study on the Behavior of Eccentrically Braced with Vertical Link
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masoud (Supervisor)
Abstract
A new eccentrically braced system is discussed. In this system which Named “eccentrically braced frame with vertical link”, the braces is connected to vertical link, instead of floor beam. The vertical link acts as a ductile energy-dissipating element, allowing the rest of the construction such as floor beams, braces and columns remain in the elastic range. In this paper, a parametric study is performed on sample frames with push-over analysis. In these analysis, the efficacy of the variation of link length, link area and the position of the link beam, is studied. The results showed that, the most important effective parameters in improvement of inelastic behavior of frame is decreasing of...
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 ; 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...
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...
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...
Control of Base Metal Capacity of Welded Connections under Multiaxial Loading
, M.Sc. Thesis Sharif University of Technology ; Maleki, Shervin (Supervisor)
Abstract
Block shear failure in the parent material is considered as a common potential failure mode in welded connections used in steel structures. However, there is only little research reported on the block shear failure of welded connections under multiaxial loading. Multiaxial loading is defined as loading not parallel or perpendicular to weld lines and in the case of in planar eccentricity results in torsional loads. In this research a nonlinear finite element model is developed to study the effect of connection geometry, weld group configuration, and eccentricity of lap splice connection on block shear capacity. The case studied concerns a 3 milimeter thick structural steel plate (CSA G40.21...
Progressive Collapse Due to Sudden Column Removal in Steel Moment and Eccentric Braced Frames
, M.Sc. Thesis Sharif University of Technology ; 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...
An Investigation on the Torsional Effects of Asymmetrically Distributed Shear Walls
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
By investigating reports of severe and destructive earthquakes of the past years we have realized that shear-wall structures most of the times had better seismic performance and more reliability than moment resistance frames. Asymmetrical arrangement of shear walls due to architectural limitations caused distortions in the structure. On the other hand, seismic regulation don’t compliance existence of twisting moment in the structures. What was said are all the most important reasons for not employing asymmetric shear wall sets in the structures by designers. The purpose of this study is to compare the seismic behavior of symmetric moment frame structures with seismic behavior of symmetric...
Reliability-Based Seismic Loss Assessment of Eccentrically Braced Frame Buildings
, M.Sc. Thesis Sharif University of Technology ; Dolatshahi, Kiarash (Supervisor)
Abstract
In this research, seismic loss of eccentrically braced frame buildings is assessed by using reliability methods. For this end, first, Bayesian linear regression is utilized to characterize the epistemic uncertainty of the problem in the form of damage models. The input of these models are mechanical and physical properties of the components, and the outputs are damage ratios. In the second step, by using the developed models and the comprehensive library of probabilistic models of Rt, reliability analysis is conducted on 4, 8, and 16 stories building located in San Jose. The limit state function is seismic loss, including repair loss, collapse loss, and demolition loss, and analysis method...
Design and Prototyping of an Axial Flux Resolver for Reduction of Estimated Position Error
, Ph.D. Dissertation Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor) ; Nasiri-Gheidari, Zahra (Supervisor)
Abstract
Providing a precise estimation of the position of a moving element is one of the requirements of many position control systems. Resolvers, as electromagnetic sensors, are one of the most suitable options for use in harsh environments with high thermal and mechanical stresses and high contamination. Although resolvers are the most reliable solution for sensitive applications in stressful environments, they are less accurate in normal operating conditions than optical encoders. In this regard, many efforts have been made to reduce the estimated position. Most of the studies have focused on modifying the electronic converter structure, which is responsible for processing the output signals of...