The Experts below are selected from a list of 121341 Experts worldwide ranked by ideXlab platform
Maged Dessouky - One of the best experts on this subject based on the ideXlab platform.
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Structural Weight optimization of frames using tabu search i optimization procedure
Journal of Structural Engineering-asce, 2006Co-Authors: M. Kargahi, James C. Anderson, Maged DessoukyAbstract:A class of search techniques, heuristic search methods, and their suitability for Structural optimization are considered for discrete optimization problems. The tabu search method is selected for application to Structural Weight optimization of skeleton structures. The search method is first tested to find the minima of a function in a nonlinear nonconvex optimization mathematical problem, and an algorithm is developed. Further, a computer program is developed that uses tabu search for Weight minimization of two-dimensional framed structures. The program, written in the FORTRAN computer language, performs search, Structural analysis, and Structural design in an iterative procedure. The program is used to optimize the Weight of three previously designed frames including three-story/three-bay, nine-story/five-bay, and 20-story/five-bay steel moment resisting frames. The program demonstrated its capability of optimizing the Weight of these medium size frames in a reasonable amount of time without requiring engineer interference during the search. The Structural Weights for the three frames are reduced by an average of 23.4% from their original design Weight.
M. Kargahi - One of the best experts on this subject based on the ideXlab platform.
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Structural Weight optimization of frames using tabu search i optimization procedure
Journal of Structural Engineering-asce, 2006Co-Authors: M. Kargahi, James C. Anderson, Maged DessoukyAbstract:A class of search techniques, heuristic search methods, and their suitability for Structural optimization are considered for discrete optimization problems. The tabu search method is selected for application to Structural Weight optimization of skeleton structures. The search method is first tested to find the minima of a function in a nonlinear nonconvex optimization mathematical problem, and an algorithm is developed. Further, a computer program is developed that uses tabu search for Weight minimization of two-dimensional framed structures. The program, written in the FORTRAN computer language, performs search, Structural analysis, and Structural design in an iterative procedure. The program is used to optimize the Weight of three previously designed frames including three-story/three-bay, nine-story/five-bay, and 20-story/five-bay steel moment resisting frames. The program demonstrated its capability of optimizing the Weight of these medium size frames in a reasonable amount of time without requiring engineer interference during the search. The Structural Weights for the three frames are reduced by an average of 23.4% from their original design Weight.
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Structural Weight Optimization with Tabu Search
Earth & Space 2006, 2006Co-Authors: M. Kargahi, James C. AndersonAbstract:Optimization of Structural Weight is of particular importance for construction in space, moon, or mars since transportation of the Structural elements to these sites is very costly. An optimized structure that satisfies the design requirements while utilizing minimum amount of material is especially suitable for construction in such remote areas and can result in significant savings in transportation costs. The Tabu Search method, a heuristic search technique, was selected for application to the Structural Weight optimization of skeleton structures. Further, a computer program was developed that uses Tabu Search for Weight minimization of two-dimensional framed structures performing search, Structural analysis, and Structural design in an iterative manner. The program was used to optimize the Weight of several frames of varying height including 3-story/3-bay, 9-story/5-bay, and 20-story/5-bay steel moment resisting frames. These frames had previously been designed to resist vertical and lateral loads. The same loads were used for the optimized Weight design using the Tabu Search program. To improve efficiency of the method, several searches were performed with different search parameters and the duration of search was increased if needed. The program demonstrated its capability of optimizing the Weight of these frames in a reasonable amount of time without requiring engineer interface during the search process. The search procedure was able to reduce the Structural Weight of these frames by 26.4%, 18.3%, and 25.5% respectively compared to their original design Weights.
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Structural Weight Optimization of Frames Using Tabu Search. II: Evaluation and Seismic Performance
Journal of Structural Engineering, 2006Co-Authors: M. Kargahi, James C. AndersonAbstract:In a companion paper, a Structural optimization computer program based on tabu search (TS) was developed and used to optimize three two-dimensional moment resisting frames. All three frames were representative of current design practice for steel structures in the Los Angeles area and were part of an SAC program of study following the Northridge earthquake. The Weight reduction obtained for the three-story/three-bay, the nine-story/five-bay, and the twenty-story/five-bay frames in the initial study were 26.4, 18.3, and 25.5%, respectively. In this paper, the seismic performance of the optimized structures is evaluated by calculating the rotation demands in the plastic hinges that form in the Structural elements during nonlinear time history analyses. Twenty ground motion records having the return probability of 10% in 50 years are considered in the study. The frames were expected to achieve the Life Safety performance level as outlined in the FEMA-273 guidelines, and in general, they were able to achieve this level of performance. Next, the same frames are optimized using the optimization module of a commercially available program, with the same assumptions (starting point sections, loading, etc.). The TS optimization program was able to achieve a larger Weight reduction than the commercially available program. The performance of the final commercial program designs is then briefly evaluated by one nonlinear time history analysis for each building using the ground motion record that produced the most severe responses for the TS designs. Performance of these frames was very similar to the TS design frames. Finally, the performance of the three TS designed frames is compared to that of the original design frames, which were designed under the same code lateral forces. The original frame designs are analyzed for the ground motion record (or records) that resulted in the largest plastic hinge rotations in the TS design frames. The values of the maximum story plastic hinge rotations, story displacements, and interstory drift ratios are compared. The response of the TS optimized frames was comparable to the original frames.
James C. Anderson - One of the best experts on this subject based on the ideXlab platform.
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Structural Weight optimization of frames using tabu search i optimization procedure
Journal of Structural Engineering-asce, 2006Co-Authors: M. Kargahi, James C. Anderson, Maged DessoukyAbstract:A class of search techniques, heuristic search methods, and their suitability for Structural optimization are considered for discrete optimization problems. The tabu search method is selected for application to Structural Weight optimization of skeleton structures. The search method is first tested to find the minima of a function in a nonlinear nonconvex optimization mathematical problem, and an algorithm is developed. Further, a computer program is developed that uses tabu search for Weight minimization of two-dimensional framed structures. The program, written in the FORTRAN computer language, performs search, Structural analysis, and Structural design in an iterative procedure. The program is used to optimize the Weight of three previously designed frames including three-story/three-bay, nine-story/five-bay, and 20-story/five-bay steel moment resisting frames. The program demonstrated its capability of optimizing the Weight of these medium size frames in a reasonable amount of time without requiring engineer interference during the search. The Structural Weights for the three frames are reduced by an average of 23.4% from their original design Weight.
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Structural Weight Optimization with Tabu Search
Earth & Space 2006, 2006Co-Authors: M. Kargahi, James C. AndersonAbstract:Optimization of Structural Weight is of particular importance for construction in space, moon, or mars since transportation of the Structural elements to these sites is very costly. An optimized structure that satisfies the design requirements while utilizing minimum amount of material is especially suitable for construction in such remote areas and can result in significant savings in transportation costs. The Tabu Search method, a heuristic search technique, was selected for application to the Structural Weight optimization of skeleton structures. Further, a computer program was developed that uses Tabu Search for Weight minimization of two-dimensional framed structures performing search, Structural analysis, and Structural design in an iterative manner. The program was used to optimize the Weight of several frames of varying height including 3-story/3-bay, 9-story/5-bay, and 20-story/5-bay steel moment resisting frames. These frames had previously been designed to resist vertical and lateral loads. The same loads were used for the optimized Weight design using the Tabu Search program. To improve efficiency of the method, several searches were performed with different search parameters and the duration of search was increased if needed. The program demonstrated its capability of optimizing the Weight of these frames in a reasonable amount of time without requiring engineer interface during the search process. The search procedure was able to reduce the Structural Weight of these frames by 26.4%, 18.3%, and 25.5% respectively compared to their original design Weights.
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Structural Weight Optimization of Frames Using Tabu Search. II: Evaluation and Seismic Performance
Journal of Structural Engineering, 2006Co-Authors: M. Kargahi, James C. AndersonAbstract:In a companion paper, a Structural optimization computer program based on tabu search (TS) was developed and used to optimize three two-dimensional moment resisting frames. All three frames were representative of current design practice for steel structures in the Los Angeles area and were part of an SAC program of study following the Northridge earthquake. The Weight reduction obtained for the three-story/three-bay, the nine-story/five-bay, and the twenty-story/five-bay frames in the initial study were 26.4, 18.3, and 25.5%, respectively. In this paper, the seismic performance of the optimized structures is evaluated by calculating the rotation demands in the plastic hinges that form in the Structural elements during nonlinear time history analyses. Twenty ground motion records having the return probability of 10% in 50 years are considered in the study. The frames were expected to achieve the Life Safety performance level as outlined in the FEMA-273 guidelines, and in general, they were able to achieve this level of performance. Next, the same frames are optimized using the optimization module of a commercially available program, with the same assumptions (starting point sections, loading, etc.). The TS optimization program was able to achieve a larger Weight reduction than the commercially available program. The performance of the final commercial program designs is then briefly evaluated by one nonlinear time history analysis for each building using the ground motion record that produced the most severe responses for the TS designs. Performance of these frames was very similar to the TS design frames. Finally, the performance of the three TS designed frames is compared to that of the original design frames, which were designed under the same code lateral forces. The original frame designs are analyzed for the ground motion record (or records) that resulted in the largest plastic hinge rotations in the TS design frames. The values of the maximum story plastic hinge rotations, story displacements, and interstory drift ratios are compared. The response of the TS optimized frames was comparable to the original frames.
Layne T Watson - One of the best experts on this subject based on the ideXlab platform.
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variable complexity response surface approximations for wing Structural Weight in hsct design
Computational Mechanics, 1996Co-Authors: Matthew Kaufman, Raphael T. Haftka, Vladimir Balabanov, Susan L Burgee, Anthony A Giunta, Bernard Grossman, William H Mason, Layne T WatsonAbstract:A procedure for generating and using a polynomial approximation to wing bending material Weight of a High Speed Civil Transport (HSCT) is presented. Response surface methodology is used to fit a quadratic polynomial to data gathered from a series of Structural optimizations. Several techniques are employed in order to minimize the number of required Structural optimizations and to maintain accuracy. First, another Weight function based on statistical data is used to identify a suitable model function for the response surface. In a similar manner, geometric and loading parameters that are likely to appear in the response surface model are also identified. Next, simple analysis techniques are used to find regions of the design space where reasonable HCST designs could occur. The use of intervening variables along with analysis of variance reduce the number of polynomial terms in the response surface model function. Structural optimization is then performed by the program GENESIS on a 28-node Intel Paragon. Finally, optimizations of the HSCT are completed both with and without the response surface.
Ali Elham - One of the best experts on this subject based on the ideXlab platform.
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Winglet design using multidisciplinary design optimization techniques
2014Co-Authors: Ali Elham, M. J. L. Van ToorenAbstract:A quasi-three-dimensional aerodynamic solver is integrated with a semi-analytical Structural Weight estimation method inside a multidisciplinary design optimization framework to design and optimize a winglet for a passenger aircraft. The winglet is optimized for minimum drag and minimum Structural Weight. The Pareto front between those two objective functions is found applying a genetic algorithm. The aircraft minimum take-off Weight and the aircraft minimum direct operating cost are used to select the best winglets among those on the Pareto front.
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Weight Indexing for Wing-Shape Multi-Objective Optimization
AIAA Journal, 2014Co-Authors: Ali Elham, M. J. L. Van ToorenAbstract:A method for wing-shape optimization is presented, in which the wing outer shape is optimized not only for the best aerodynamic efficiency but also for the minimum Structural Weight. The so-called airfoil effective distance is used to capture the influence of the wing outer shape on the wing-box Structural Weight. The airfoil Weight index is defined based on the airfoil effective distance. Increasing the airfoil Weight index results in decreasing the Structural Weight. The Weight indexing method is used for airfoil multi-objective optimization for minimizing the aerodynamic drag as well as maximizing the Weight index. The Pareto front for the drag and Weight is found, and the airfoils on the Pareto front are used as the basis airfoils for a three-dimensional wing-shape optimization. The same method is applied to optimize the outer shape of three-dimensional wings for two objective functions: minimizing the wing drag and minimizing the wing Structural Weight. A response surface methodology is used to reduc...
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Effect of wing-box structure on the optimum wing outer shape
The Aeronautical Journal, 2014Co-Authors: Ali Elham, M.j.l. Van ToorenAbstract:Abstract A new method for wing shape optimisation is presented, in which the wing shape is optimised not only for the best aerodynamic properties but also for minimum Structural Weight. An advanced Structural sizing method for wing Structural Weight estimation is developed. The method is based on elementary, physics based analyses of simplified structure to determine the amount of required material to resist the applied loads. The sizing loads are determined based on the airworthiness regulations using advanced aerodynamic analysis tools. In this new Weight estimation method, the effect of wing outer (aerodynamic) shape on the wing-box Structural Weight is taken into account. A mathematical equation is derived, which relates the wing-box Structural Weight to the wing outer shape. The Weight estimation method is validated for several existing passenger aircraft. A series of optimisations is performed to optimise the wing shape for a general objective function, which includes both aerodynamic and Structural properties of the wing. The aircraft fuel Weight is used as the objective function. Different structures are tested both metal and composite ones. The latter includes different composite layups. In order to find the effect of the internal structure on the optimum wing outer shape, the design lift coefficient is assumed to be constant for all the test cases. The results of the optimisations showed that the optimum wing shape is depending on the Structural concept (metal alloys versus different composite layups) for different internal structures.
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Weight Indexing for Airfoil Multi-Objective Optimization
Journal of Aircraft, 2013Co-Authors: Ali Elham, M. J. L. Van ToorenAbstract:A new method for airfoil shape optimization is presented, in which the airfoil shape is optimized not only for the best aerodynamic efficiency but also for the minimum Structural Weight. To relate the Structural Weight to the airfoil shape a series of methods are prescribed for initial sizing of the wingbox structure. Based on these methods, a “Weight index” is defined. The airfoil Weight index is a mathematical equation that relates the Structural Weight of the wingbox to the airfoil shape. The Structural Weight of a wingbox reduces by increasing the Weight index of the airfoil. A set of multi-objective optimizations is performed to find the Pareto front of the airfoil drag and the Weight index.
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Encyclopedia of Aerospace Engineering - Structural Design: Weight Estimation
Encyclopedia of Aerospace Engineering, 2012Co-Authors: Ali ElhamAbstract:Weight estimation and calculation of aircraft Structural and nonStructural Weight is an important aspect of the aircraft design process. The estimation and calculation process is built on an aircraft Weight breakdown method. The Weight breakdown process is discussed based on several examples, with a focus on the Structural Weight breakdown principles. The Weight estimation methods are categorized in four different classes. The low-class methods are based on statistical data to estimate the Structural Weight while the high-class methods use physics-based calculations like beam theory and finite element modeling complemented with empirical methods to estimate the Weight of the nonStructural parts. Statistical Weight estimation methods are usually used in the early design stages when the knowledge of designers about the new aircraft is limited and the Weight estimation process has to rely on previous experience. When the design matures there is an increasing understanding of the design and higher class Weight estimation methods can be used. In the final design phase, Weight estimation transfers into Weight calculation. Keywords: aircraft Structural Weight; aircraft Weight decomposition; analytical Weight estimation methods; finite element model; statistical Weight estimation methods; Weight estimation methods
