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structural-optimization
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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....
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...
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...
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...
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...
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...
A new real-coded Bayesian optimization algorithm based on a team of learning automata for continuous optimization
, Article Genetic Programming and Evolvable Machines ; Vol. 15, Issue. 2 , 2014 , pp. 169-193 ; ISSN: 13892576 ; Beigy, H ; Sharif University of Technology
Abstract
Estimation of distribution algorithms have evolved as a technique for estimating population distribution in evolutionary algorithms. They estimate the distribution of the candidate solutions and then sample the next generation from the estimated distribution. Bayesian optimization algorithm is an estimation of distribution algorithm, which uses a Bayesian network to estimate the distribution of candidate solutions and then generates the next generation by sampling from the constructed network. The experimental results show that the Bayesian optimization algorithms are capable of identifying correct linkage between the variables of optimization problems. Since the problem of finding the...
An analytical solution for shape-memory-polymer Euler-Bernoulli beams under bending
, Article International Journal of Mechanical Sciences ; Vol. 84, issue , July , 2014 , p. 84-90 ; Mohammadi, H ; Naghdabadi, R ; Sharif University of Technology
Abstract
The purpose of this paper is to present efficient and accurate analytical expressions for deflection of a shape memory polymer (SMP) beam employing Euler-Bernoulli beam theory in a thermomechanical SMP cycle. Material behavior is considered using a recently 3D thermodynamically consistent constitutive model available in literature. In different steps of an SMP thermomechanical cycle, closed form expressions for internal variables variations, stresses and beam curvature distribution are presented. We show that during the cooling process, stored strains evolve to fix the temporary shape and then during the heating process they relax to recover the permanent shape. Effects of applying external...
Discrete optimum design of truss structures by an improved firefly algorithm
, Article Advances in Structural Engineering ; Vol. 17, issue. 10 , 2014 , p. 1517-1530 ; Makiabadi, M ; Sarcheshmehpour, M ; Sharif University of Technology
Abstract
This paper presents an improved firefly algorithm (FA) for fast optimization of truss structures with discrete variables. The enhanced accelerated firefly algorithm (AFA) is a simple, but very effective modification of FA. In order to investigate the performance and robustness of the proposed algorithm, some benchmark (structural optimization) problems are solved and the results are compared with FA and other algorithms. The results show that in some test cases, AFA not only finds lighter structures compared to other algorithms, but also converges faster. In the rest test cases, the optimal solutions are found with very less computational effort. The study also shows that the proposed AFA...
Optimal tuning for fractional-order controllers: An integer-order approximating filter approach
, Article Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME ; Volume 135, Issue 2 , July , 2013 ; 00220434 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
2013
Abstract
This paper offers a systematic framework for the design of suboptimal integer-order controllers based on fractional-order structures. The proposed approach is built upon the integer-order approximations that are traditionally used to implement fractional-order controllers after they are designed. Accordingly, the fractional-order structures are exploited to derive a suitable parameterization for a fixed-structure integer-order controller. The parameters, which describe the structure of the fixed-order integer controller, are the same as those used to describe the original fractional structure. Optimal tuning is then performed in the parameter space of the fractional structure and the...
Severe plastic deformation of rheoforged aluminum alloy A356
, Article Materials Science and Engineering A ; Volume 558 , 2012 , Pages 371-376 ; 09215093 (ISSN) ; Kazeminezhad, M ; Aashuri, H ; Sharif University of Technology
2012
Abstract
In this research, the electromagnetic stirring (EMS) process was used to produce semi-solid slurry with globular structure from cast A356 aluminum alloy. Then the slurry was forged in a die, which named rheoforging process. Utilizing multidirectional forging (MDF), the effect of severe plastic deformation on microstructure and mechanical properties of this alloy in dendritic and globular states was investigated. Shear punch, micro- and macro-hardness tests were used to study the mechanical properties of these samples. For metallographic examinations, the optical microscope equipped with the Clemex ® image analyzer software was used. Optimum globular structure of rheoforged specimens was...
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...
Curvilinear fiber optimization tools for aeroelastic design of composite wings
, Article Journal of Fluids and Structures ; Volume 33 , 2012 , Pages 180-190 ; 08899746 (ISSN) ; Zamani, Z ; Sharif University of Technology
Elsevier
2012
Abstract
The aeroelastic design of composite wings modeled as thin-walled beams is investigated through the use of curvilinear fiber. The structural model considers non-classical effects such as transverse shear, warping restraint, rotary inertia, nonuniform torsional model and also aerodynamic loads based on Wagner's function. In this paper, a linear spanwise variation of the fiber orientation resulting in a variable-stiffness structure is used to optimize the wing for maximum aeroelastic instability speed purpose, while manufacturing constraints are incorporated. Numerical results indicate improvements of aeroelastic stability of variable-stiffness wings over conventional, constant-stiffness ones
Prediction of shape and internal structure of the proximal femur using a modified level set method for structural topology optimisation
, Article Computer Methods in Biomechanics and Biomedical Engineering ; Volume 15, Issue 8 , 2012 , Pages 835-844 ; 10255842 (ISSN) ; Farahmand, F ; Rouhi, G ; Movahhedy, M. R ; Sharif University of Technology
Abstract
A computational framework was developed to simulate the bone remodelling process as a structural topology optimisation problem. The mathematical formulation of the Level Set technique was extended and then implemented into a coronal plane model of the proximal femur to simulate the remodelling of internal structure and external geometry of bone into the optimal state. Results indicated that the proposed approach could reasonably mimic the major geometrical and material features of the natural bone. Simulation of the internal bone remodelling on the typical gross shape of the proximal femur, resulted in a density distribution pattern with good consistency with that of the natural bone. When...
Comparative analysis of hydrate formation pressure applying cubic equations of state (eos), artificial neural network (ann) and adaptive neuro-fuzzy inference system (anfis)
, Article International Journal of Thermodynamics ; Volume 15, Issue 2 , 2012 , Pages 91-101 ; 13019724 (ISSN) ; Saber, M ; Ameri, A ; Sharif University of Technology
Abstract
The objective of this work is making comparison between thermodynamic models and data-driven techniques accuracy in prediction of hydrate formation pressure as a function of temperature and composition of gas mixtures. The Peng-Robinson (PR) and Patel-Teja (PT) equations of state are used for thermodynamic modeling and Artificial Neural Networks (ANNs) and Adaptive Neuro-Fuzzy Inference System (ANFIS) are used as data-driven models. The capability of each method is evaluated by comparison with the experimental data collected from literature. It is shown that there is a good agreement between thermodynamic modeling and the experimental data in most of the cases; however, the prediction...
An efficient performance-based seismic design method for reinforced concrete frames
, Article Earthquake Engineering and Structural Dynamics ; Volume 41, Issue 4 , 2012 , Pages 663-679 ; 00988847 (ISSN) ; Asadi, P ; Pilakoutas, K ; Sharif University of Technology
Abstract
In this paper, a practical method is developed for performance-based design of RC structures subjected to seismic excitations. More efficient design is obtained by redistributing material from strong to weak parts of a structure until a state of uniform deformation or damage prevails. By applying the design algorithm on 5, 10 and 15-storey RC frames, the efficiency of the proposed method is initially demonstrated for specific synthetic and real seismic excitations. The results indicate that, for similar structural weight, designed structures experience up to 30% less global damage compared with code-based design frames. The method is then developed to consider multiple performance objectives...
Neuro-fuzzy control strategy for an offshore steel jacket platform subjected to wave-induced forces using magnetorheological dampers
, Article Journal of Mechanical Science and Technology ; Volume 26, Issue 4 , 2012 , Pages 1179-1196 ; 1738494X (ISSN) ; Zareh, S. H ; Khayyat, A. A. A ; Zabihollah, A ; Sharif University of Technology
2012
Abstract
Magnetorheological (MR) damper is a prominent semi-active control device to vibrate mitigation of structures. Due to the inherent non-linear nature of MR damper, an intelligent non-linear neuro-fuzzy control strategy is designed to control wave-induced vibration of an offshore steel jacket platform equipped with MR dampers. In the proposed control system, a dynamic-feedback neural network is adapted to model non-linear dynamic system, and the fuzzy logic controller is used to determine the control forces of MR dampers. By use of two feedforward neural networks required voltages and actual MR damper forces are obtained, in which the first neural network and the second one acts as the inverse...
GPU implementation of split-field finite difference time-domain method for drudelorentz dispersive media
, Article Progress in Electromagnetics Research ; Volume 125 , 2012 , Pages 55-77 ; 10704698 (ISSN) ; Rashidian, B ; Sharif University of Technology
2012
Abstract
Split-field finite-difference time-domain (SF-FDTD) method can overcome the limitation of ordinary FDTD in analyzing periodic structures under oblique incidence. On the other hand, huge run times of 3D SF-FDTD, is practically a major burden in its usage for analysis and design of nanostructures, particularly when having dispersive media. Here, details of parallel implementation of 3D SF-FDTD method for dispersive media, combined with totalfield/ scattered-field (TF/SF) method for injecting oblique plane wave, are discussed. Graphics processing unit (GPU) has been used for this purpose, and very large speed up factors have been achieved. Also a previously reported formulation of SF-FDTD based...
Novel polyamide-based nanofibers prepared by electrospinning technique for headspace solid-phase microextraction of phenol and chlorophenols from environmental samples
, Article Analytica Chimica Acta ; Volume 716 , 2012 , Pages 34-39 ; 00032670 (ISSN) ; Aghakhani, A ; Baghernejad, M ; Akbarinejad, A ; Sharif University of Technology
2012
Abstract
A novel solid phase microextraction (SPME) fiber was fabricated by electrospinning method in which a polymeric solution was converted to nanofibers using high voltages. A thin stainless steel wire was coated by the network of polymeric nanofibers. The polymeric nanofiber coating on the wire was mechanically stable due to the fine and continuous nanofibers formation around the wire with a three dimensional structure. Polyamide (nylon 6), due to its suitable characteristics was used to prepare the unbreakable SPME nanofiber. The scanning electron microscopy (SEM) images of this new coating showed a diameter range of 100-200nm for polyamide nanofibers with a homogeneous and porous surface...
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...