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Optimal Retrofitting of the Steel Moment Resisting Frames Using Telescopic Dampers
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masoud (Supervisor) ; Eskandari, Morteza (Co-Supervisor)
Abstract
The purpose of this thesis is the optimal retrofitting of the moment resisting frames with telescopic dampers, using the adaptive approach. In this regard, numerical modeling of the telescopic behavior has been presented firstly. Also, a 3,9,20 story (sac) moment resisting frame has been modeled in the OpenSees environment and the time history analysis has been carried out under a specific earthquake record. It is shown that inter-story drifts of the frame exceed the acceptance criteria which has been assumed 2.5% according to the Life Safety limit. Then, the optimal retrofitting of the frame has been done. It is demonstrated that the maximum inter-story drift of all stories is 2.5% or less,...
Seismic Performance Assessment of Bridges Equipped with Shape Memory Alloy Added Base Isolation Bearing
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor) ; Jahanshahi, Mohsen (Co-Advisor)
Abstract
Seismic performance analysis is conducted for an isolated three-span continuous highway bridge, which is restrained with shape memory alloy bar. Two series of earthquake ground acceleration, known as ‘pulse records’ and ‘non-pulse records’ are applied to the bridge in three directions. Four types of pier-girder connection are used in the analysis: rigid connection (only for comparison), lead rubber bearing system (LRB), lead rubber bearing along shape memory alloy (SMA) restrainer system and high damping rubber bearing (HDRB) system. SMA bar restrainer is made of Ni-Ti. In the first step of the work, structural properties and analytical models of the bridge segments are introduced. Then, a...
Investigation the ASCE 7-10 Proposed Scaling Method of Earthquake Records in Evaluation of the Response Parameters of Base-Isolated Structures
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayaz (Supervisor)
Abstract
The majority of modern seismic Codes and guidelines require scaling of selected ground motion time histories so that the dynamic time history analyses results will be comparable to those obtained from the dynamic modal analyses. The scaling procedure would basically apply, considering a specific part of the design spectrum depending on the approximate period of the system. In this work, the efficiency of the proposed scaling method of earthquake records by ASCE STANDARD 7-10 for evaluation of true response parameters of base isolated structures will be investigated. For this purpose, a number of 3-D structural models with different numbers of stories will be considered. Then, using...
On the Base Shear Force Distribution Along the Height of Base-Isolated Structures With LRB Isolators Subjected to Near Field Earthquakes
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
Abstract
In recent years there has been a huge amount of attention in the application of the base isolation system as a passive procedure to limit seismic response of structures. A number of international codes including UBC97, ASCE07-2005, and ASCE-2010 have devoted a special part for the Seismic analysis and design of base-isolated structures. The present work investigates the vertical distribution of the lateral seismic force, for base-isolated structures suggested by the ASCE07_05 code under near field earthquakes. Near field earthquakes have attracted so much interest among the researchers and engineers due to their disastrous effects on structures. According to the recorded data, it is...
Evaluation of the Performance of Fluid Dampers in Controlling the Seismic-Induced Response of Structures
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayaz (Supervisor)
Abstract
Natural disasters, such as earthquakes and hurricanes, can strike without warning, resulting in a range of destruction from structural damage to loss of life. For this reason, research on structural control, which provides a new basis for design of structural systems against winds, earthquakes, waves, and traffic loadings, become of interest in civil engineering. This thesis focuses on using fluid dampers as a passive energy dissipation device. Viscous Fluid Dampers (VFD) are the most commonly used passive energy dissipation devices that are manufactured in various forms. However, the orifice type of Viscous Fluid Damper (VFD) is considered for structural applications. In this thesis, the...
Evaluation of Demand Modifier Factor ,M, in FEMA356 for Concrete Structures Under Near-Field Earthquakes
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
Abstract
On the average, ten thousand people die annually due to earthquakes. A UNESCO study gives damage losses amounting to ten billion dollars within the years 1926 to 1950 from earthquakes. These data shows the importance of earthquake issue that causes the scientists to pay special attention to this subject. In despite of significant improvements in many of scientific fields, earthquake is still remains as an unknown event without the possibility of predicting its time and location of occurrence. Because of that, a large effort has been paid for rehabilitation of structures to prevent the human loss and maintaining the necessary life safety. In this regard, various guidelines have been proposed...
Evalution of Demand Modifier Factor "M" in FEMA 356 for Steel Structures Under Far-Field Earthquakes
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
Abstract
Continuous improvement of the existing seismic design codes and regulations clearly shows the need for evaluation and probable retrofitting of the existing building structures. A large amount of literature has been produced on different topics related to retrofitting including FEMA 273, ATC 40, FEMA356 and most recently the draft of FEMA 440. On the other hand, it has been long recognized that the response of buildings to strong ground shaking caused by earthquakes results in inelastic behavior. Until recently, most structural analysis techniques devised for practical application relied on linear procedures to predict the seismic response of the building structures. But due to various...
An Intelligent Routing Protocol for Delay Tolerant Networks Using Genetic Algorithm
, M.Sc. Thesis Sharif University of Technology ; Hendessi, Faramarz (Supervisor)
Abstract
Due to the dynamic topology of vehicular ad hoc networks, routing of packets in these networks faces a lot of difficulties. The situation will become more challenging when we have to deal with Delay Tolerant Networks (DTN) which are also sparse and partitioned and we need to use some vehicles to store the packets and carry them from one partition to another. Despite all these difficulties, by looking through movements of vehicles in an urban environment, we can find out that the topology of the network does not change in a pure random way and we can bring the traffic models of streets into account for having better routing performance. In this thesis, we proposed an intelligent routing...
Investigating the Performance of Tuned Mass Dampers in Controlling the Torsional Response of 3-D Steel Structural Models Under Earthquake Excitation
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofouei, Fayyaz (Supervisor)
Abstract
Existing structural irregularities (in plan and elevation) has always been among the important causes of structural failures under strong earthquakes. The torsional related damages have especially been very important in multi-story buildings as the torsional behavior of structures changes their uniform translational vibration and causes concentration of demands in the elements at the perimeter of the buildings. On the other hand, the Tuned Mass Dampers (TMD) have in general been accepted as an effective passive structural control device to suppress the structural vibration. In this study, Three 3-D, irregular (in plan) steel structural models with 4, 8 and 15 number of floors are considered...
Use of Data Assimilation Methods for Multiphase Flow in Porous Media
, M.Sc. Thesis Sharif University of Technology ; Rajabi Ghahnavieh, Abbas (Supervisor) ; Bazargan, Hamid (Co-Supervisor)
Abstract
The importance of optimizing the extraction process of available resources increases each day due to the increasing energy consumption and the lack of energy resources. Oil and gas are one of the most important sources of energy. Although existing oil and gas resources are thought to be sufficient to meet the growing energy demand for the next few decades, given the non-renewable nature of these resources and the growing demand for oil and gas, it will become much harder to meet the future energy demand. Many existing oil fields are now in the process of maturing, and the discovery of large new oil fields is rare. As a result, new technologies must be used in the future to meet this demand,...
A Historical Analysis of the Evolution of Dominant Industrial Development Approaches in the Age of Pahlavi in Iran
, M.Sc. Thesis Sharif University of Technology ; Souzanchi Kashani, Ebrahim (Supervisor)
Abstract
Our country in no measure is considered as an industrial one, despite its chain of small, medium and large industries. The vague, general “developing” term might be the best term to assign to economic-industrial condition of our country. We have a fairly limited number of big industrial firms (BIF) which could continue operation without state’s supports in a world BIFs are considered as the key indices in industrial development. The question comes to mind with reading what came above is this study’s main question, “What went wrong?”. This study follows the historical approach to the question through a comprehensive case study. Historical case-study thus is our main research approach here....
The Evolution of the Idea of Progress in Western Thought and a Critical Look at It from an Islamic View
, M.Sc. Thesis Sharif University of Technology ; Taghavinia, Nima (Supervisor)
Abstract
“Progress” is among most frequently used terms in the past few centuries in public discussions, scientific communities as well as economic and sociopolitical policy making. This term has been used in our daily conversations so frequently that it seems to become an intrinsic goal for human beings. However, even a short survey of the introduced meanings of and suggested approaches to achieve “progress” during the last four centuries - since the term was first used- demonstrates that we are faced with a multitude of views from the different - and sometimes contradictory - schools of thoughts. Unfortunately, in recent decades, despite our national desire to “progress”, we have not yet thought...
Critique of Kuhns Histirical Perspective from Gadamerian Perspective
, M.Sc. Thesis Sharif University of Technology ; Moeinzadeh, Mahdi (Supervisor) ; Taghavi, Mostafa (Supervisor)
Abstract
Truth and Method is one of the two or three most important works of this century on the philosophy of humanistic studies. The book is powerful, exciting, but undeniably difficult. Published when Gadamer was sixty, it gathers the ripe fruit of a lifetime's reading, teaching, and thinking. Because it is immersed in German philosophy and scholarship, the book is even more challenging for an American reader. An emerging body of commentary in English as well as the many shorter essays Gadamer has, happily, lived to write and which are increasingly available in translation provide additional means of access to his thought. Truth and Method, however, remains his magnum opus, the comprehensive and...
History Modeling in Conversational Question Answering
, M.Sc. Thesis Sharif University of Technology ; Beigy, Hamid (Supervisor)
Abstract
In this thesis, we propose a method for long document modeling to address the issue of handling lengthy documents. The results indicate that our method successfully improves the problem of independently modeling chunks that arise from long documents. Additionally, we present consistent training using history augmentation to enhance the representation of questions with a long history. Our experiments demonstrate that this proposed method increases the performance of the baseline model, particularly for questions with a long history. The long document modeling approach improves the baseline's performance by 2.1% based on the F1 criteria. Furthermore, the consistent training using history...
Conversational Question Answering in Partial Context
, M.Sc. Thesis Sharif University of Technology ; Sameti, Hossein (Supervisor)
Abstract
Conversational Question Answering (CQA) has gained significant attention in recent years due to its potential to facilitate natural language interactions between humans and machines. The ability to effectively incorporate relevant history turns, which are previous utterances in a conversation, plays a crucial role in improving the overall performance of CQA systems. In this master's thesis, we explore the importance of conversational question answering and propose a novel approach for selecting relevant history turns to enhance the accuracy and relevance of the system's responses. Initially, we provide an overview of the recent models developed for addressing the CQA challenge. We analyze...
Event History Analysis in Complex Networks
, Ph.D. Dissertation Sharif University of Technology ; Rabiee, Hamid Reza (Supervisor)
Abstract
Event history analysis is a classic problem in stochastic process, that recently attracts the researchers' attention in complex networks. The goal is to model the time of events, like check in a restaurant check-in or post a message, given their history, and then control them. In this thesis we try to improve both aspects of the problem. In event modeling, we focus on two challenging cases. The first case removes the independence assumption in diffusion of cascades in social networks, and investigate the correlated cascades. We use a multidimensional Hawkes process with soft-max mark function, to model the competitive and cooperative cascades. We infer parameters of the problem using...
Distributed Denial of Service Mitigation
,
M.Sc. Thesis
Sharif University of Technology
;
Kharrazi, Mehdi
(Supervisor)
Abstract
Denial of service (DoS) attacks is the main challenges of service providers due to their purpose to makes their service unavaillable. Nowadays this attacks are changed from centralized to distributed (DDoS) by means of botnets. In addition botnets allow attackers to launch attack on higher layers of network, such as application layer. In new application layer DDoS attacks, attacker send HTTP requests to waste victims resources. In addition, attacker can start attack during flash crowd event which makes attack more undetectable. In this research, in order to migigating such attacks, we introduced a method based on user’s history.
This history consist of user’s request rate for each...
This history consist of user’s request rate for each...
A Botnet Detection Technique
, M.Sc. Thesis Sharif University of Technology ; Kharrazi, Mehdi (Supervisor)
Abstract
A set of infected computers which are coordinated in some manner by one’s willingness and can perform malicious activities and provide threats in the cyberspace forms a network of bots, namely botnet. Botnet threats are more important and significant than other malwares due to their huge scale. A lot of computers coming together in a network obeying one’s commands allows their controller to conduct, for example, DoS attacks larger than ever seen incidents. This thesis, introduces botnets, their various threats, and an effective technique for detecting them. For this reason, different probable states of bots will be studied and modeled as a coherent bot life-cycle. The bot life-cycle allows...
A Security Model based on Modal Description Logic for Semantic Web
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasool (Supervisor)
Abstract
With the growth of semantic-aware environments, such as semantic web, new security requirements are imposed in access control procedures. An access control model for semantic web should take the semantic relationships (in three scopes of subject, object and action) into account in its access decisions. Considering the advantages of logic based models and description logic foundation of semantic web, we use the description logic as a basis to propose access control models in this environment. On the other hand, in some applications, such as e-banking environments, policy definition with the constraint(s) based on previous users’ accesses might be crucial. To consider this aspect, in this...
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...