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mohammadnejad--hamed
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On the experimental and numerical study of braced steel shear panels
, Article Structural Design of Tall and Special Buildings ; Volume 24, Issue 14 , 2015 , Pages 853-872 ; 15417794 (ISSN) ; Mofid, M ; Sharif University of Technology
2015
Abstract
Steel shear panels in combination with bracing are a novel form of steel shear walls that eliminate large distributed loads to impose on primary beams along with columns. This paper presents the results of a comparative experimental program on two types of steel shear panels with and without stiffeners. For this purpose, the proposed quasi-static cyclic loading history of Federal Emergency Management Agency(FEMA) 461 was applied on two full-scale specimens. Structural steel was selected as the material of the panels, which were welded to the surrounding boundary elements. In addition, using finite element models, performed tests were simulated and scaling effects were investigated. This...
On the equivalent simple models of braced steel shear panels
, Article Proceedings of the Institution of Civil Engineers: Structures and Buildings ; Volume 168, Issue 8 , August , 2015 , Pages 570-577 ; 09650911 (ISSN) ; Mofid, M ; Sharif University of Technology
Thomas Telford Services Ltd
2015
Abstract
Through the combination of two types of seismic resisting systems including braced frames and steel shear walls, braced steel shear panel systems can be formed. This new lateral load-resisting system solves some of the defects of current special steel shear walls, such as imposing significant loads on boundary elements along with gravity load effects. Analysis and design of this new structural system underline the importance of having simple and precise finite-element models. To this aim, this paper presents two types of equivalent braced frames termed ‘overall equivalent brace’ and ‘equivalent mid-brace’. The equations of brace area, material strength and strain-hardening ratio are obtained...
On the plastic analysis of concentrically braced frames with shear panel, obtaining predetermined collapse mechanism
, Article Structural Design of Tall and Special Buildings ; Volume 24, Issue 5 , 2015 , Pages 366-395 ; 15417794 (ISSN) ; Mofid, M ; Sharif University of Technology
2015
Abstract
Summary Conventional design methods do not ensure that the desired collapse mechanism is developed at target displacement. In this paper, a case study is presented to analyze concentrically braced frames with steel shear panel (CBFSP). Also, extensive investigation in the failure modes are made, to have the global yielding mode at the final state. For this purpose, each of one-story, three-story, six-story and nine-story CBFSP models were decomposed into three parts where the members' closed-form equations of internal forces were identified and superimposed. On the basis of the kinematic theorem of plastic collapse, the possible mechanisms and the related energy equations were defined to...
Analysis & Vibration Control of a Rotating Beam with Variable Properties of the Cross Section
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor)
Abstract
The purpose of this project is to model a rotating beam with variable properties of the cross section and also to present an active control method for suppressing the undesired vibrations due to external loading. The beam is modeled as a cantilever Euler-Bernoulli beam with nonuniform physical and geometrical properties. For a practical example, the characteristics of a wind turbine blade was used to solve the problem. The analyzed blade in this study is NREL 5-MW wind turbine blade. But the method can be extended to be used for other blades as well . First the natural frequencies and modeshapes were computed by MATLAB. Then by applying pole placement method, a control strategy was designed...
A Framework to Evaluate the Resilience of Hospitals
, M.Sc. Thesis Sharif University of Technology ; Kashani, Hamed (Supervisor)
Abstract
In the aftermath of earthquakes, hospitals serve the critical role of treating casualties and reducing mortalities and severe injuries. A hospital must be resilient to play its role correctly after the earthquake. A resilient hospital is able to maintain its functionality at an acceptable level and provide service to the injured. In order to enhance the resilience of a hospital, an appropriate framework is needed to evaluate the hospital resilience and determines the impact of modification actions. This framework should characterize the serviceability of a hospital in terms of an appropriate metric. In this framework, the behavior of a given hospital building in the event of an earthquake as...
Plastic design of eccentrically braced frames with shear panels
, Article Proceedings of the Institution of Civil Engineers: Structures and Buildings ; Volume 170, Issue 1 , 2017 , Pages 17-32 ; 09650911 (ISSN) ; Mofid, M ; Sharif University of Technology
Thomas Telford Services Ltd
2017
Abstract
This paper introduces a new earthquake-resistant building design featuring eccentrically braced frames with steel wall shear panels. It also proposes closed-form expressions for analysis and extension of the existing failure mode control design method for the new structural system. Closed-form equations for internal forces were obtained, and probable failure mechanisms and corresponding lateral load multipliers for secondary effects were identified. Selection of member profiles was completed by the mechanism equilibrium curve concept. Pushover modelling was then performed with plastic hinge distribution corresponding to failure mechanisms. Only small differences were found between the...
Modeling of the Flood-induced Failure of Community Infrastructure Systems with Emphasis on Food Supply Chain
, M.Sc. Thesis Sharif University of Technology ; Kashani, Hamed (Supervisor)
Abstract
This study provides a probabilistic framework for assessing and quantifying flood damage to infrastructure. This framework models the state of the community's infrastructure after the occurrence of possible floods in five steps. The first step is to model the hazard using a set of models that determine the characteristics of potential floods. The second step is to model and estimate the damage to community buildings and infrastructure. In the third step, infrastructure serviceability is modeled. The infrastructures that are modeled in this study are water distribution network, power network, transportation networks and industrial facilities for processing agricultural products. In the fourth...
Active Control of Edgewise Vibrations in Wind Turbine Blade by Optimization of the Number and Locations of the Intermediate Actuators
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor)
Abstract
Vibrations in HAWT reduce their efficiency and increase maintenance costs. In this paper, the blade edgewise vibrations are reduced by using several actuators in different parts of the wind turbine blade and optimization of the number and locations of actuators. The wind turbine blade dynamic behavior is investigated by using dynamic modeling. The actuators are trusses that are located inside each blade and apply control force to different parts of the blade. Active control force is applied to reduce edgewise vibrations. The designed controller is applied and simulated on NREL 5MW wind turbine. By applying the controller, the edgewise vibrations of wind turbine blades are significantly...
Probabilistic Modeling of the Repair Time and Cost of the Structural Components of Earthquake-damaged Buildings
, M.Sc. Thesis Sharif University of Technology ; Kashani, Hamed (Supervisor)
Abstract
This study aims to investigate the cost and time uncertainty of the seismic repair process of structural elements in earthquake damaged buildings in Iran. In order to identify the most important type of structural system in the country, using the method of analytic hierarchy process (AHP), 39 activists in the field of construction were interviewed. Based on the results, in buildings with reinforced concrete materials, concrete moment frames and in buildings with steel materials, steel moment frames and braced steel braced frames are the most important structural systems. By selecting the structural component of lateral load-bearing in each of the mentioned structural systems and considering...
Robust Controller Design for Three-Dimensional Overhead Crane System with Variable Cable Length
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor)
Abstract
The main goal of controlling overhead crane systems is to safely transfer the load to its desired position with maximum speed and accuracy, as well as to minimize or eliminate load oscillations. The overhead crane system is considered as an underactuated mechanical system in which the number of control inputs (actuators) is less than the number of degrees of freedom. In addition, overhead crane systems are generally associated with parametric or unmodeled uncertainties. Also, in these systems, external disturbances such as wind have a destructive effect on the system's performance. In addition, if the overhead crane has the hoisting mechanism and the length of the rope changes as the trolley...
Replacement of Pt with Graphene Derivatives in Counter Electrode of Dye-Sensitized Solar Cells
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor) ; Askari, Masoud (Supervisor)
Abstract
Dye-Sensitized solar cells are the third generation of solar cells that have the potential to increase efficiency as much as solar cells of previous generations, along with lower prices. The cathode electrode of the pigmented solar cell as one of the essential components of the cell plays the role of accelerating the oxidation reaction reduction of the electrolyte. Platinum often is used as a catalyst layer. To reduce production costs and maintain cell viability, platinum should replace with other materials at a lower cost and higher electrochemical activity. Recently, carbon materials have been considered for the production of inexpensive solar cells with suitable performance. Among...
Hot workability of ultrafine-grained aluminum alloy produced by severe plastic deformation of Al6063 powder and consolidation [electronic resource]
, Article Materials Science Forum ; Volume 667-669, 2011, Pages 979-984 ; Simchi, A. (Abdolreza) ; Seop Kim, Hyoung ; Sharif University of Technology
Abstract
Al6063 powder was subjected to severe plastic deformation via high-energy mechanical milling to prepare ultrafine-grained (UFG) aluminium alloy. Uniaxial compression test at various temperatures between 300 and 450 °C and strain rates between 0.01 and 1 s-1 was carried out to evaluate hot workability of the material. Microstructural studies were performed by EBSD and TEM. The average activation energy and strain rate sensitivity of the hot deformation process were determined to be 280 kJ mol-1 and 0.05, respectively. The deformation temperature and applied strain rate significantly affected the grain structure of UFG Al alloy. A finer grain structure was obtained at lower temperatures and...
Evaluation of Dea Models for the Out puts,Inputs Estimation and Improvement Organizational Performance
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Farhad (Supervisor)
Abstract
Measurement of efficiency is a significant issue in organizations which is used to improvement efficiency and performance .one of the serious offaires in any country, is banking, inefficiency in which leads to problems and obstacles in developing capital market. In this research, Data Envelopment Analysis models are used to estimate the extent of performance in decision making units (DMU’s) to improve inefficient ones. We change the inputs ( outputs) to a special unit at both the constancy or improvement of efficiency using the DEA models, we estimate the values of output ( input ) levels. Howeve, we assume the data of (the values of input ( output ) levels ) can be either crisp or interval....
Design of Continuous and Time-Invariant Controllers for Exponential Stabilization of Periodic Walking and Running Locomotion in Planar Bipedal Robots
, Ph.D. Dissertation Sharif University of Technology ; Sadati, Nasser (Supervisor)
Abstract
During the last decades there have been enormous advances in robot control of dynamic walking and running. The desire to study legged locomotion has been motivated by 1) the desire to replace humans in hazardous occupations, 2) the desire to assist disabled people to walk and 3) the desire to investigate the complicated motions of the mankind. The control of dynamic walking and running is complicated by (i) limb coordination, (ii) hybrid nature of running due to presence of impact and takeoff, (iii) underactuation and overactuation, (iv) inability to apply the Zero Moment Point (ZMP) criterion, (v) lack of algorithms to achieve feasible period-one orbits, and (vi) conservation of angular...
A Framework to Forecast Highway Construction Materials Prices
, M.Sc. Thesis Sharif University of Technology ; Kashani, Hamed (Supervisor)
Abstract
Due¬ to the volatile nature of material prices, projecting highway construction costs are proven to be very difficult, leading to many challenges in cost estimation process. Bid preparations as well as project planning and control processes are also negatively affected by the concerns about the inaccuracy of cost projections. There is a growing body of evidence that suggests the use of inaccurate cost estimate can result in bid loss or profit loss for contractors and hidden price contingencies, delayed or cancelled projects, inconsistency in budgets and unsteady flow of projects for owner organizations. Analysis of historical data indicates that a relationship between construction materials...
A fast and reliable multi-sender algorithm for peer-to-peer networks
, Article Journal of Network and Computer Applications ; Volume 32, Issue 3 , May , 2009 , Pages 733–740 ; Sharif University of Technology
2009
Abstract
Due to special constraints in peer-to-peer (P2P) networks (such as bandwidth limitation) and because of their highly dynamic characteristics, a single node cannot provide a reliable multimedia stream to the receivers. Several multi-sender algorithms are proposed to reliably deliver a media stream to the receiver through the intrinsically unreliable P2P networks. Based on upload bandwidths and availability of peers as well as the bandwidths of the links connecting the senders and the receiver, PROMISE selects a set of active senders to maximize the expected bit-rate delivered to the receiver. By careful investigation of PROMISE, in this paper, we present why and how it deviates from finding...
Design, Modeling and Investigation of Seismic Behavior of Bracing Type Steel Shear Panels
, Ph.D. Dissertation Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
So far a number of solutions have been proposed to resolve some problems of steel plate shear walls including large induced loads on the surrounding members, late panel’s yielding along with lack of openings. One of the forms that can be considered for steel shear walls is braced shear panels.Regarding to the many advantages of this structural system, in this thesis steel shear panels with concentric or eccentric bracing have been introduced. For this purpose, first a procedure for plastic analysis and design, aiming to develop a predetermined collapse mechanism, is proposed. The results demonstrate that the closed-form analytical equations along with the extension of failure mode control...
Evaluation of Hollowfiber Membranes Uesd In Hemodialysis
, M.Sc. Thesis Sharif University of Technology ; Abdekhodaei, Mohammad Jafar (Supervisor)
Abstract
Due to largre number of patients treated by dialysis and its significant increasing progress, dialysis efficiency and patients' life quality are of great interest.Dialyzer, the dialysis beating heart, has the role of cleaning blood by removing toxic solutes and balancing volume of bood's water through hollow fiber membranes. In this thesis, firstly we tried to focus on performance characteristics of dialyzer by studying effective parameters influencing dialyzer efficiency and ultimately we set two important performance characteristics, ultrafiltration coefficient and solute clearance, as our goal parameters for evaluating dialyzer's yield. To this purpose, we designed an experimental set...
Forced Vibration of Drill String and its Control in Directional Drilling
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor)
Abstract
Nowadays, economical extraction of oil and gas, and their products is an important issue for many countries. Up to now, vertical wells have been used for oil extraction but some wells exist that they cannot be reached by using vertical drilling; for example the wells under a sea. Therefore, this makes the governments and scientists determined to find a new way to reach them. Horizontal drilling is one of the new ways to reach such worthy wells. In this project, dynamics of the horizontal drill string is studied. Then, according to the forces that affect the dynamics of drilling, its vibration is analyzed. After finding the boundary conditions and normal modes of the system with using mode...
Control of Bifurcation and Chatter Suppression in Peripheral Milling Process
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor)
Abstract
Self-excitation vibration or chatter in the milling process is one of the most critical factors in reducing the tool life and surface smoothness. With the change of tool speed or depth of cut, bifurcation phenomena occur at some points (bifurcation points) such that the system behaviour becomes unstable and the chatter is observed. In this study, using nonlinear modelling for cutting forces, two main methods for active control of this process are proposed. The first is an intelligent control based on emotional learning, which is a model-free strategy. In this method, the critic generates a signal (stress signal) using error and its derivative. The purpose of this controller is to reduce the...