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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...
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...
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...
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...
Comparison between uniform deformation method and Genetic Algorithm for optimizing mechanical properties of dampers
, Article Earthquake and Structures ; Volume 14, Issue 1 , February , 2018 , Pages 1-10 ; 20927614 (ISSN) ; Mirjalaly, M ; Mirtaheri, M ; Nazeryan, M ; Sharif University of Technology
Techno Press
2018
Abstract
Seismic retrofitting of existing buildings and design of earth-quake resistant buildings are important issues associated with earthquake-prone zones. Use of metallic-yielding dampers as an energy dissipation system is an acceptable method for controlling damages in structures and improving their seismic performance. In this study, the optimal distribution of dampers for reducing the seismic response of steel frames with multi-degrees freedom is presented utilizing the uniform distribution of deformations. This has been done in a way that, the final configuration of dampers in the frames lead to minimum weight while satisfying the performance criteria. It is shown that such a structure has an...
Optimum design of retaining structures under seismic loading using adaptive sperm swarm optimization
, Article Structural Engineering and Mechanics ; Volume 81, Issue 1 , 2022 , Pages 93-102 ; 12254568 (ISSN) ; Kalhor, A ; Tehrani, M. S ; Jebeli, M ; Sharif University of Technology
Techno-Press
2022
Abstract
The optimum design of reinforced concrete cantilever retaining walls subjected to seismic loads is an extremely important challenge in structural and geotechnical engineering, especially in seismic zones. This study proposes an adaptive sperm swarm optimization algorithm (ASSO) for economic design of retaining structure under static and seismic loading. The proposed ASSO algorithm utilizes a time-varying velocity damping factor to provide a fine balance between the explorative and exploitative behavior of the original method. In addition, the new method considers a reasonable velocity limitation to avoid the divergence of the sperm movement. The proposed algorithm is benchmarked with a set...
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...
Dispersion and deposition of nanoparticles in microchannels with arrays of obstacles
, Article Microfluidics and Nanofluidics ; Volume 21, Issue 4 , 2017 ; 16134982 (ISSN) ; Moosavi, A ; Sadrhosseini, H ; Sharif University of Technology
Springer Verlag
2017
Abstract
Air pollutants are among the hazardous materials for human health. Therefore, many scientists are interested in removing particles from the carrier gas. In this study, flow of air and airborne particles through the virtual multi-fibrous filters that consist of different fiber cross-sectional shapes and arrangements is simulated where particle deposition and filtration performance are studied. Regular and irregular arrangements of fibers with the circular, elliptical, and equilateral triangular cross sections have been considered. Effects of important parameters such as solid volume fraction, internal structure, and filter thickness on particle collection efficiency and pressure drop are...
Optimal design of truss structures with frequency constraints: a comparative study of DE, IDE, LSHADE, and CMAES algorithms
, Article Engineering with Computers ; 2021 ; 01770667 (ISSN) ; Mesbahi, P ; Moosavian, N ; Daliri, H ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
The present study examines the performance of three powerful methods including the original differential evolution (DE), the improved differential evolution (IDE), and the winner of the CEC-2014 competition, LSHADE, in addition to the covariance matrix adaptation evolution strategy (CMAES) for size optimization of truss structures under natural frequency constraints. Despite the abundant researches on novel meta-heuristic algorithms in the literature, the application of CMAES, one of the most powerful and reliable optimization algorithms, on the optimal solution of the truss structures has received scant attention. For consistent comparison between these algorithms, four stopping criteria...
Multi-objective optimization of vehicle floor panel with a laminated structure based on V-shape development model and Taguchi-based grey relational analysis
, Article Structural and Multidisciplinary Optimization ; Volume 65, Issue 3 , 2022 ; 1615147X (ISSN) ; Khalkhali, A ; Ahmadi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
In this paper, the V-shape development model approach for designing an automotive floor panel made by laminated structure is investigated to attain the best trade-off between the system and subsystem level requirements while improving the local and global performance of the vehicle. For this purpose, the bending and torsional stiffness of the body structure, as well as mass, strength, and vibration attenuation of the floor panel, are considered as design objectives at the system and subsystem levels. A multi-objective discrete optimization of a laminated configuration is performed using the Taguchi-based grey relational analysis. Material grades and thicknesses of the sandwich panel face...
Energy-spectral efficient resource allocation and power control in heterogeneous networks with D2D communication
, Article Wireless Networks ; 2018 ; 10220038 (ISSN) ; Sobhi Givi, S ; Kalbkhani, H ; Shayesteh, M. G ; Sharif University of Technology
Springer New York LLC
2018
Abstract
Heterogeneous networks (HetNets) provide the demand for high data rates. In this study, we analyze the coexistence of femtocells and device-to-device (D2D) communication with macrocells. Interference management and decreasing energy consumption are two important issues in HetNets. To this end, we propose an efficient fractional frequency reuse (FFR)-based spectrum partitioning scheme to reduce the cross-tier interference. We also propose to use different optimization problems for resource allocation in different tiers. For this purpose, an energy efficient optimization problem is applied to D2D user equipment. Further, an optimization problem based on the spectral efficiency, i.e.,...
Energy-spectral efficient resource allocation and power control in heterogeneous networks with D2D communication
, Article Wireless Networks ; Volume 26, Issue 1 , August , 2020 , Pages 253-267 ; Sobhi Givi, S ; Kalbkhani, H ; Shayesteh, M. G ; Sharif University of Technology
Springer
2020
Abstract
Heterogeneous networks (HetNets) provide the demand for high data rates. In this study, we analyze the coexistence of femtocells and device-to-device (D2D) communication with macrocells. Interference management and decreasing energy consumption are two important issues in HetNets. To this end, we propose an efficient fractional frequency reuse (FFR)-based spectrum partitioning scheme to reduce the cross-tier interference. We also propose to use different optimization problems for resource allocation in different tiers. For this purpose, an energy efficient optimization problem is applied to D2D user equipment. Further, an optimization problem based on the spectral efficiency, i.e.,...
Multi-objective optimal design of stiffened laminated composite cylindrical shell with piezoelectric actuators
, Article International Journal on Interactive Design and Manufacturing ; Volume 14, Issue 2 , January , 2020 , Pages 595-611 ; Bohlooly, M ; Sharif University of Technology
Springer
2020
Abstract
The stiffeners and piezoelectric actuators are used in many aerospace structures as an auxiliary layer with laminated composites. A question then arises as to whether we can estimate the percentage of these materials in an efficient design. Due to the high computational cost, it is not easy to answer through numerical solutions. The objective of this paper is concurrently to maximize the buckling load and minimize the weight of the cylindrical shell. To reach this aim, a multi-objective optimization problem is developed based on the closed-form solutions of thermal/mechanical buckling and weight of the piezolaminated shell with eccentric/concentric stiffener. The Non-dominated Sorting...
Reliability-based optimization of an active vibration controller using evolutionary algorithms
, Article Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2017, 26 March 2017 through 29 March 2017 ; Volume 10168 , 2017 ; 0277786X (ISSN); 9781510608214 (ISBN) ; Pourtakdoust, S. H ; Fiberguide Industries; Frontiers Media; OZ Optics, Ltd.; Polytec, Inc.; The Society of Photo-Optical Instrumentation Engineers (SPIE) ; Sharif University of Technology
SPIE
2017
Abstract
Many modern industrialized systems such as aircrafts, rotating turbines, satellite booms, etc. cannot perform their desired tasks accurately if their uninhibited structural vibrations are not controlled properly. Structural health monitoring and online reliability calculations are emerging new means to handle system imposed uncertainties. As stochastic forcing are unavoidable, in most engineering systems, it is often needed to take them into the account for the control design process. In this research, smart material technology is utilized for structural health monitoring and control in order to keep the system in a reliable performance range. In this regard, a reliability-based cost...
A methodology for value based seismic design of structures by the endurance time method
, Article Scientia Iranica ; Volume 23, Issue 6 , 2016 , Pages 2514-2527 ; 10263098 (ISSN) ; Estekanchi, H. E ; Vafai, A ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
A new design methodology based on the total value of structures is introduced. This methodology, namely Value Based Design of structures (VBD), uses the advantages of Endurance Time (ET) method. While prescriptive and earlier generations of performance based design approaches commonly try to find structures with the least initial cost, a design approach to directly incorporate the concept of value in design procedure has been formulated here. Reduced computational effort in ET analysis provides the prerequisites to practical use of optimization algorithms in seismic design. A genetic algorithm is used with the objective of minimizing total cost of the building during its lifespan. ET method...
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...
Multi-objective selection and structural optimization of the gantry in a gantry machine tool for improving static, dynamic, and weight and cost performance
, Article Concurrent Engineering Research and Applications ; Volume 24, Issue 1 , 2016 , Pages 83-93 ; 1063293X (ISSN) ; Dabbagh, V ; Amini, H ; Sarhan, A. A. D ; Akbari, J ; Hamdi, M ; Ong, Z. C ; Sharif University of Technology
SAGE Publications Ltd
Abstract
In this investigation, the multi-objective selection and optimization of a gantry machine tool is achieved by analytic hierarchy process, multi-objective genetic algorithm, and Pareto-Edgeworth-Grierson-multi-criteria decision-making method. The objectives include maximum static deformation, the first four natural frequencies, mass, and fabrication cost of the gantry. Further structural optimization of the best configuration was accomplished using multi-objective genetic algorithm to improve all objectives except cost. The result of sensitivity analysis reveals the major contribution of columns of gantry with respect to the crossbeam's contribution. After determining the most effective...