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Developing of MIDA Method in Irregular Structures in Plan with Concentrated Plasticity Model
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
In this research, modal incremental dynamic analysis (MIDA) has been investigated on three-dimensional structures with irregular plans. The MIDA method is an incremental static analysis that considers higher modes of the structure. In fact, it is a combination of modal pushover (MPO) and incremental dynamic analysis (IDA) methods that incorporate the advantages of both and is much faster than the IDA method. Compared to constant analyses, incremental analysis is more extensive in terms of results and response to earthquakes. Due to the uncertainties in the nature of future earthquakes, engineers use the IDA method to achieve a broader view of the structure's response under potential...
Investigation on Seismic Performance of Eccentrically Braced Frames with Vertical Post-tensioned Cables
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Although the moment frame can show deformable behavior against seismic loads, but its flexibility and low stiffness, especially in tall structures, cause the governance criterion to be designed. The use of eccentrically braced frames was able to solve the displacement problem to some extent, because it has the characteristics of both flexural frame systems and conccentric bracing. Different methods have been proposed to eliminate residual displacements in this type of system, one of which is the use of post tensioned cables. The aim of this study was to investigate the seismic behavior of a steel structure with a eccentrically braced frame system with post tension cable.The cables are anchor...
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...
Predicting Structural Response of Steel Building under Ground Motion Excitation using Deep Learning Networks
, M.Sc. Thesis Sharif University of Technology ; Mohtasham Dolatshahi, Kiarash (Supervisor) ; Yazdanpanah, Omid (Supervisor)
Abstract
This paper aims at producing surrogate models which can predict building structural response under ground motion loads. Rapid response prediction has a great influence on post-event decision-making. The current study follows mentioned purpose in two main sections. The first section proposed deep models, able at estimating displacement time-series response by using only ground motion and roof acceleration. By this point, different preprocessing methods and their effects are studied. Also, a novel loss function is introduced and a hybrid model consists of different deep layers utilized to gain accurate models. These models train and evaluate on two case-study buildings; a special moment frame...
Nonmodel Seismic Assessment of Eccentrically Braced Steel Frames with Masonry Infills Using Machine Learning Techniques
, M.Sc. Thesis Sharif University of Technology ; Mohtasham Dolatshahi, Kiarash (Supervisor)
Abstract
This study investigates the seismic behavior of eccentrically braced frames (EBFs) taking into account the influence of masonry infill walls. The primary objectives of the study are to predict the seismic global response and develop associated fragility curves using a nonmodel scenario-based machine learning framework. To model the infill walls, equivalent diagonal struts are employed, and a nonlinear pushover analysis is conducted to assess the overall impact of infills on 4- and 8-story EBF structures. An extensive database of 4 bare and 48 infilled EBFs with various infill properties is assembled to predict story-based engineering demand parameters (EDPs) containing peak and residual...
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...
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...
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...
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,...
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...
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...
A Machine Learning Model for Simplified Damage and Loss Assessment of the Buildings After an Earthquake
, M.Sc. Thesis Sharif University of Technology ; Mohtasham Dolatshahi, Kiarash (Supervisor)
Abstract
This study presents a Machine Learning framework for post-earthquake structural damage state and economic loss estimation. The framework is proposed to rapidly determine whether a structure is safe or unsafe to be occupied following a seismic event, to predict the detailed structural response, and finally to evaluate the economic loss of the buildings. An extensive database is developed by analyzing twelve low-rise, mid-rise, and high-rise eccentrically braced frames (EBFs) under 44 scaled ground motion records through incremental dynamic analysis (IDA) to train the Machine Learning algorithms. Machine Learning algorithms are employed to classify the structural damage state of the buildings...
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...
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 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...
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...
Investigating the Behaviour of A Type of Energy Absorbing Bracing System
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)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...
Design of Fillet Welds in Plastic State
, M.Sc. Thesis Sharif University of Technology ; Maleki, Shervin (Supervisor)
Abstract
Nowadays, many structural engineers use fillet welds in their designs because of their high strength and affordability. In these welds, eccentric loadings either out-of-plane or in-plane create complex condition in welds from stress point of view. To determine the capacity of such fillet welds different methods have been proposed over time. For instance, the method approved by AISC is the Elastic method. This method when combined with load factors, as required by the LRFD design method, yields very conservative designs for fillet welds. Therefore, in this project, we try to propose the plastic method for welds under eccentric loadings. This method is more economical than the elastic method...