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structural-optimization
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Total 101 records
Value-Based Seismic Design of Framed Tube System of Tall Steel Buildings
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Pourestekanchi, Homayun (Supervisor)
Abstract
The objective of this research is to evaluate the concept of a new design methodology based on the total value of the structure namely Value Based Design of structures (VBD) by the use of potential benefits of the ET method. While prescriptive and also performance based approaches of seismic design commonly try to find a structure with lower initial cost satisfying a number of requirements under seismic actions, a new design approach to incorporate directly the concept of value in design procedure have been formulated here to achieve an economical design with lower total cost in its life time. In this method the design sections of structural elements are considered as optimization parameters...
Determination of Stable Crystal Structure of Y358 New Superconductor and its Phonon and Electronic Structure using Density Functional Theory
, M.Sc. Thesis Sharif University of Technology ; Khosroabadi, Hossein (Supervisor) ; Akhavan, Mohammad (Co-Advisor)
Abstract
Y-based Superconducting compounds (YBCO) with different stoichiometry have been considered by researchers for its transition temperature above the boiling temperature of liquid nitrogen, preparation of high quality samples, simple crystal and electronic structure and other advantages relative to the other high-Tc copper oxide superconductors. Reaching to higher transition temperature has been considered in the recent years. In 2009, new compound of this family with different stoichiometry Y3Ba5Cu8O18(Y358) and transition temperature above 100 K was synthesized which is 10 K higher than maximum transition temperature in this family. Confirming this transition temperature can be help us for...
Optimization of Distribution and Stiffness of Connections in Steel Frames by Value based Seismic Design
, M.Sc. Thesis Sharif University of Technology ; Esmail Pourestekanchi, Homayoon (Supervisor)
Abstract
Structural optimization has always been one of the concerns of engineers. Usually, engineers decide to optimize the structure with its weight. Nowadays we know that the best solution in weight optimization is not good for the structural damage and performance of the structure due to risk analysis.In this study, using the genetic algorithm to reduce construction cost, Loss and damaged cost and total cost of the structure by calculating structural damage based on FEMA-P58 guidelines according to two types of connections (rigid or hinge) and their elements (beams and columns) in two types of structures 4 and 8 story has been investigated.At each stage of increment in algorithms, first, the...
An Investigation on the Effect of Design Parameters on Behabior of Prestressed Ring-Shaped Steel Structures
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Purestekanchi, Homayoon (Supervisor)
Abstract
A tensile-compression ring is derived from the spoke wheel principle. The wheel is one of the greatest inventions in mankind. The use of the wheel has developed through time. Engineers found out that the use of the spoke wheel as a roof structure provides many benefits. With the spoke wheel principle a lightweight, cost-efficient roof structure can be made. In recent years the spoke wheel principle has also been applied for oval shaped roofs in order to increase the application of the principle. An example is the use of the roof structure for football stadia. The problem is that the spoke wheel principle will only work at full extend when its shape is completely circular. The question rises...
Application and Comparison of Modern Optimization Methods for Optimal Seismic Design of Trusses under Base Excitation
, M.Sc. Thesis Sharif University of Technology ; Joghatayi, Abdolreza (Supervisor)
Abstract
Taking into consideration of optimization methods has been increased recently. Optimization methods in engineering that consumes a lot of time and cost have been developed. Optimal design of structures is a matter that grabbed the attention of civil engineers and due to the deficiency of classical methods the modern approaches are being developed. One of the most important structures that are constructed for industrial and transportation purposes are truss structures.Structural control under support excitation is constraining the structure to some structural limitations. The final target in this paper is to apply the modern methods to get the optimal weight of structure under seismic loads....
Optimum Seismic Design Assessment of Tall Buildings Based on Life Cycle Cost Using Endurance Time Method
, Ph.D. Dissertation Sharif University of Technology ; Esmail Pourestekanchi, Homayoon (Supervisor) ; Ghannad, Mohammad Ali (Co-Supervisor)
Abstract
The relatively large number of structural elements and the variety of design code requirements complicate the design process of tall buildings. This process is exacerbated when the target is to obtain the seismic code-compliant optimal design with the minimum weight which results in a large-scale and challenging optimization problem. On the other hand, past earthquakes and hurricanes demonstrated that while satisfying the requirements of the conventional design codes guarantees the life safety of the occupants, significant economic losses may still be incurred. This highlights the importance of considering life cycle costs in the design process of the structures. But the issue is that the...
Value based seismic design of structures using performance assessment by the endurance time method
, Article Structure and Infrastructure Engineering ; Volume 16, Issue 10 , January , 2020 , Pages 1397-1415 ; Estekanchi, H. E ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
A framework for optimal seismic design of structures, considering maximum value as the design objective, is introduced. In this framework, the value parameter incorporates a comprehensive set of performance indicators. Decision indicators are mapped into equivalent economic values and are directly involved in the design process. This approach leads to optimal assignment of the available resources to meet infrastructure requirements. The construction cost and the risk of seismic consequences are considered as the value components. FEMA-P58 methodology is utilized in estimation of the seismic consequences including the repair cost, repair time, injuries and casualties. Endurance Time method is...
Utility of probability density evolution method for experimental reliability-based active vibration control
, Article Structural Control and Health Monitoring ; Volume 25, Issue 8 , 2018 ; 15452255 (ISSN) ; Pourtakdoust, S. H ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
The utility of probability density evolution method for reliability-based active vibration control of a cantilevered flexible beam is experimentally investigated. In this respect, an optimal linear quadratic regulator (LQR) is utilized together with an observer to design an online full-state feedback controller. In order to design a well-performing controller and to simulate the controller performance, a system model is obtained via identification techniques. Reliability tests are consequently performed to verify the effectiveness of the presented reliability assessment method as a foundation for reliability-based control. Subsequently, a hybrid metaheuristic optimization scheme of...
Tuned mass damper for vibration control in steel jacket platforms
, Article Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 15 June 2008 through 20 June 2008, Berlin ; Volume 1 , 2008 , Pages 35-42 ; 9780791848234 (ISBN) ; Gholizad, A ; Ocean, Offshore, and Arctic Engineering Division; ASME ; Sharif University of Technology
2008
Abstract
Considering the stress cycles in joints and members due to wave induced forces on offshore platforms, fatigue analysis is therefore one of the most important analyses in offshore platforms design. Most of steel jacket type platforms located in areas with relatively high ratios of operational sea-states to maximum design environmental events; fall in acceptable safety margin in inplace and seismic analyses. But in fatigue analyses they will face critical condition. Therefore it seems that utilizing control mechanisms with the aim of increasing fatigue life in such platforms will be more preferable to merely deck displacement control. Investigation of tuned mass dampers adjustable parameters...
Transmission of a bit over a discrete Poisson channel with memory
, Article 2020 IEEE Information Theory Workshop, ITW 2020, 11 April 2021 through 15 April 2021 ; 2021 ; 9781728159621 (ISBN) ; Gohari, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
A coding scheme for transmission of a bit maps a given bit to a sequence of channel inputs (called the codeword associated to the transmitted bit). In this paper, we study the problem of designing the best code for a discrete Poisson channel with memory (under peak-power and total-power constraints). The outputs of a discrete Poisson channel with memory are Poisson distributed random variables with a mean comprising a fixed additive noise and a linear combination of past input symbols. Assuming a maximum-likelihood (ML) decoder, we find the best codebook design by minimizing the error probability of the decoder over all codebooks. For the case of having only a total-power constraint, the...
Transmission of a bit over a discrete Poisson channel with memory
, Article 2020 IEEE Information Theory Workshop, ITW 2020, 11 April 2021 through 15 April 2021 ; 2021 ; 9781728159621 (ISBN) ; Gohari, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
A coding scheme for transmission of a bit maps a given bit to a sequence of channel inputs (called the codeword associated to the transmitted bit). In this paper, we study the problem of designing the best code for a discrete Poisson channel with memory (under peak-power and total-power constraints). The outputs of a discrete Poisson channel with memory are Poisson distributed random variables with a mean comprising a fixed additive noise and a linear combination of past input symbols. Assuming a maximum-likelihood (ML) decoder, we find the best codebook design by minimizing the error probability of the decoder over all codebooks. For the case of having only a total-power constraint, the...
Transmission of a bit over a discrete poisson channel with memory
, Article IEEE Transactions on Information Theory ; Volume 67, Issue 7 , 2021 , Pages 4710-4727 ; 00189448 (ISSN) ; Gohari, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
A coding scheme for transmission of a bit maps a given bit to a sequence of channel inputs (called the codeword associated with the transmitted bit). In this paper, we study the problem of designing the best code for a discrete Poisson channel with memory (under peak-power and total-power constraints). The outputs of a discrete Poisson channel with memory are Poisson distributed random variables with a mean comprising of a fixed additive noise and a linear combination of past input symbols. Assuming a maximum-likelihood (ML) decoder, we search for a codebook that has the smallest possible error probability. This problem is challenging because error probability of a code does not have a...
Transmission of a bit over a discrete poisson channel with memory
, Article IEEE Transactions on Information Theory ; Volume 67, Issue 7 , 2021 , Pages 4710-4727 ; 00189448 (ISSN) ; Gohari, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
A coding scheme for transmission of a bit maps a given bit to a sequence of channel inputs (called the codeword associated with the transmitted bit). In this paper, we study the problem of designing the best code for a discrete Poisson channel with memory (under peak-power and total-power constraints). The outputs of a discrete Poisson channel with memory are Poisson distributed random variables with a mean comprising of a fixed additive noise and a linear combination of past input symbols. Assuming a maximum-likelihood (ML) decoder, we search for a codebook that has the smallest possible error probability. This problem is challenging because error probability of a code does not have a...
Topology optimization for the seismic design of truss-like structures
, Article Computers and Structures ; Volume 89, Issue 7-8 , April , 2011 , Pages 702-711 ; 00457949 (ISSN) ; Pilakoutas, K ; Moghaddam, H ; Sharif University of Technology
2011
Abstract
A practical optimization method is applied to design nonlinear truss-like structures subjected to seismic excitation. To achieve minimum weight design, inefficient material is gradually shifted from strong parts to weak parts of a structure until a state of uniform deformation prevails. By considering different truss structures, effects of seismic excitation, target ductility and buckling of the compression members on optimum topology are investigated. It is shown that the proposed method could lead to 60% less structural weight compared to optimization methods based on elastic behavior and equivalent static loads, and is efficient at controlling performance parameters under a design...
The use of ladder particle swarm optimisation for quantitative structure-activity relationship analysis of human immunodeficiency virus-1 integrase inhibitors
, Article Molecular Simulation ; Volume 37, Issue 15 , 2011 , Pages 1221-1233 ; 08927022 (ISSN) ; Ebrahimi-Najafabadi, H ; Sharif University of Technology
2011
Abstract
This contribution focuses on the use of ladder particle swarm optimisation (LPSO) on modelling of oxadiazole- and triazolesubstituted naphthyridines as human immunodeficiency virus-1 integrase inhibitors. Artificial neural network (ANN) and Monte Carlo cross-validation techniques were combined with LPSO to develop a quantitative structure-activity relationship model. The techniques of LPSO, ANN and sample set partitioning based on joint x-y distances were applied as feature selection, mapping and model evaluation, respectively. The variables selected by LPSO were used as inputs of Bayesian regularisation ANN. The statistical parameters of correlation of deterministic, R2, and...
Theoretical study of nitrogen monoxide adsorption on small Six (x = 3-5) clusters
, Article Molecular Physics ; Volume 109, Issue 2 , 2011 , Pages 229-237 ; 00268976 (ISSN) ; Gobal, F ; Sharif University of Technology
2011
Abstract
Theoretical study of nitrogen monoxide adsorption on small Six (x = 3-5) clusters has been carried out using the advanced hybrid meta-density functional method of Truhlar (MPW1B95). MG3 semi-diffuse basis sets were employed to improve the results. The geometry, adsorption energy, natural bond orbital charge, natural population analysis (NPA)-derived spin density and vibrational frequency of NO adsorption on all optimized nanoclusters were investigated. Also using the NPA, we have investigated the change of bond orders through adsorption. It has been found that NO is capable of making n-centre bonds (n = 1-4) from the nitrogen side but bonds to one site from the oxygen end. In the later case...
Testing soccer league competition algorithm in comparison with ten popular meta-heuristic algorithms for sizing optimization of truss structures
, Article International Journal of Engineering, Transactions A: Basics ; Volume 30, Issue 7 , 2017 , Pages 926-936 ; 17281431 (ISSN) ; Moosavian, H ; Sharif University of Technology
Abstract
Recently, many meta-heuristic algorithms are proposed for optimization of various problems. Some of them originally are presented for continuous optimization problems and some others are just applicable for discrete ones. In the literature, sizing optimization of truss structures is one of the discrete optimization problems which is solved by many meta-heuristic algorithms. In this paper, in order to discover an efficient and reliable algorithm for optimization of truss structures, a discrete optimizer, entitled Soccer League Competition (SLC) algorithm and ten popular and powerful solvers are examined and statistical analysis is carried out for them. The fundamental idea of SLC algorithm is...
Synthesis, characterization, DFT studies and catalytic activities of manganese(ii) complex with 1,4-bis(2,2′:6,2′′-terpyridin- 4′-yl) benzene
, Article Dalton Transactions ; Volume 41, Issue 39 , Jul , 2012 , Pages 12282-12288 ; 14779226 (ISSN) ; Hillier, W ; Shamkhali, A. N ; Amini, M ; Beckmann, K ; Jagličić, Z ; Jagodič, M ; Strauch, P ; Moghaddam, A. N ; Beretta, G ; Bagherzadeh, M ; Sharif University of Technology
2012
Abstract
A new di-manganese complex with "back-to-back" 1,4-bis(2,2′:6,2′′-terpyridin-4′-yl) benzene ligation has been synthesized and characterised by a variety of techniques. The back-to-back ligation presents a novel new mononuclear manganese catalytic centre that functions as a heterogeneous catalysis for the evolution of oxygen in the presence of an exogenous oxidant. We discuss the synthesis and spectroscopic characterizations of this complex and propose a mechanism for oxygen evolution activity of the compound in the presence of oxone. The di-manganese complex also shows efficient and selective catalytic oxidation of sulfides in the presence of H2O2. Density functional theory calculations were...
Study of microstructural evolution and phase's morphology after partial remelting in A356 alloy
, Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 367-372 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Bigdeli, M ; Hajian Heidary, M ; Khomamizadeh, F ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
In this work, effective parameters of SIMA process to obtain non dendritic microstructure in A356 alloy were investigated. In addition, the effect of SIMA process on the evolution of morphology of silicon and intermetallic phases in this alloy was studied. Microstructure images obtained from optical microscopy and SEM observation showed that increase in plastic work up to 40% and then holding of samples in the semi solid state at temperature of 580°C, causes that primary dendritic structure changes to non dendritic, fine and globular structure, but optimum reheating time completely depended on initial thickness of samples. If all parameters of SIMA process are the same, the grain boundaries...
Structural optimization by spherical interpolation of objective function and constraints
, Article Scientia Iranica ; Volume 23, Issue 2 , 2016 , Pages 548-557 ; 10263098 (ISSN) ; Joghataie, A ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
A new method for structural optimization is presented for successive approximation of the objective function and constraints in conjunction with Lagrange multipliers approach. The focus is on presenting the methodology with simple examples. The basis of the iterative algorithm is that after each iteration, it brings the approximate location of the estimated minimum closer to the exact location, gradually. In other words, instead of the linear or parabolic term used in Taylor expansion, which works based on a short step length, an arch is used that has a constant curvature but a longer step length. Using this approximation, the equations of optimization involve the Lagrange multipliers as the...