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Öğe Advanced energy-based analyses of trusses employing hybrid metaheuristics(Wiley, 2019) Bekdas, Gebrail; Kayabekir, Aylin Ece; Nigdeli, Sinan Melih; Toklu, Yusuf CengizTotal potential optimization using metaheuristic algorithm (TPO/MA) is an alternative method in structural analyses, and it is a black-box application for nonlinear analyses. In the study, an advanced TPO/MA using hybridization of several metaheuristic algorithms is investigated to solve large-scale structural analyses problems. The new generation algorithms considered in the study are flower pollination algorithm (FPA), teaching learning-based optimization, and Jaya algorithm (JA). Also, the proposed methods are compared with methodologies using classic and previously used algorithms such as differential evaluation, particle swarm optimization, and harmony search. Numerical investigations were carried out for structures with four to 150 degrees of freedoms (design variables). It has been seen that in several runs, JA gets trapped into local solutions. For that reason, four different hybrid algorithms using fundamentals of JA and phases of other algorithms, namely, JA using Levy flights, JA using Levy flights and linear distribution, JA with consequent student phase, and JA with probabilistic student phase (JA1SP), are developed. It is observed that among the variants tried, JA1SP is seen to be more effective on approaching to the global optimum without getting trapped in a local solution.Öğe Analysis of Plane-Stress Systems via Total Potential Optimization Method Considering Nonlinear Behavior(Asce-Amer Soc Civil Engineers, 2020) Toklu, Yusuf Cengiz; Kayabekir, Aylin Ece; Bekdas, Gebrail; Nigdeli, Sinan Melih; Yucel, MeldaAs an alternative structural analysis method, total potential optimization using metaheuristic algorithms (TPO/MAs) has been demonstrated to be very effective, especially in nonlinear cases, for trusses and trusslike systems such as tensegric structures and cable networks. A recent study showed that TPO/MAs also can be applied successfully to plane-stress problems with linear constitutive equations. The present study enlarged the application area of TPO/MAs to the analysis of plates for plane-stress cases with nonlinear stress-strain equations. A relevant formulation was developed and used to solve five problems. Because TPO/MAs can be applied by using different metaheuristic algorithms, a number of them, some hybrid, were used, and they were compared among themselves and with finite-element solutions. The final example was a tunnel problem with 150 nodes, i.e., with 265 unknowns. This problem also was solved via hybrid algorithms. Several proposals for future research are listed. (c) 2020 American Society of Civil Engineers.Öğe Harmony Search Optimization of Nozzle Movement for Additive Manufacturing of Concrete Structures and Concrete Elements(MDPI, 2020) Toklu, Yusuf Cengiz; Bekdaş, Gebrail; Geem, Zong WooThere are several ways of using three-dimensional printing techniques in the construction industry. One method that seems quite feasible is the concreting of walls and structural components starting at the bottom and progressing up in layers according to the principles of additive manufacturing. The goal of this study is to optimize the movements of a nozzle at one level hatwillresultinthisoperation. Thisstudyconsidersthatthemovementsofthenozzlecanbeoftwo types: rectangular only (i.e., only in x and y directions) or more freely, including moving in diagonal directions. Applications are performed on four hypothetical ?ats (with 7, 8, 14, and 31 walls, respectively) and a structural component with 17 members. It is shown that as the number of walls and members increase, the problem of optimizing the movements of the nozzle becomes increasingly di?cult due to exponentially increasing path combinations. A comparison is presented in terms of the ratio of movements of the nozzle without concreting to total distances traveled. The optimization rocessisconductedusingtheHarmonySearchalgorithmwithaspecialcodingandencodingsystemÖğe Lunar Soil Simulants- An Assessment(IEEE, 2019) Toklu, Yusuf Cengiz; Akpinar, PinarIn this study an assessment is done about lunar soil simulants. It is found that until now more than 40 simulants are produced in 9 countries. This procedure is a still ongoing one, after its start in the year 1990. The list of the simulants produced given in the paper is the most comprehensive one and it includes not only all of the types given in previous surveys, but also presents information on the most recent simulants that were produced within the last decade. The properties of the simulants are explained briefly. Possible uses of lunar soils in lunar constructions are also explained. The fact that all countries, even those which are not considered as developed ones, can take place in this field of research is also emphasized.Öğe Lunar soils, simulants and lunar construction materials: An overview(Elsevier Sci Ltd, 2022) Toklu, Yusuf Cengiz; Akpinar, PinarOne of the hot subjects in space civil engineering is the research for establishing outposts on space bodies, starting with the Moon. This wide research topic mainly covers learning about ground conditions and soils of these extraterrestrial bodies, looking for means of using the soil in producing construction materials, designing structures appropriate for local conditions, and finally choosing construction techniques to be applied using mainly these materials. In this paper, as the title indicates, an overview is presented on three aspects of using local materials in lunar construction activities: nature of in-situ soils obtained with lunar missions, the variety of lunar soil simulants produced on Earth, and their use in producing lunar construction materials. (C) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.Öğe A metaheuristic-based method for analysis of tensegrity structures(Wiley, 2024) Bekdas, Gebrail; Ocak, Ayla; Nigdeli, Sinan Melih; Toklu, Yusuf CengizTensegrity systems are construction system that offers solutions for lighter designs compared with a standard truss system consisting of tension and compression elements. Due to their structure, they are recommended in the design of space structures due to the use of lighter and easy-to-assemble structural elements such as cables, ropes, and similar to provide the desired durability. In this study, energy minimization was carried out to solve the structural element displacements. It is expected to reduce the total potential energy of the system with minimization. By minimizing the total potential energy of the tensegrity system models, the displacement of each building element is found for the equilibrium condition. Tensegrity models were analyzed by minimizing energy via the adaptive harmony search (AHS) algorithm. In this research, two distinct tensegrity structure specimens were employed. One comprised a cantilever beam, while the other adopted a cyclic model, forming eight equal octagons from eight nodes at both the base and the top. Additionally, an examination was conducted on a two-layer iteration of the cyclic model. The method is robust for both space and planar tensegrity structures, allowing the determination of deformed shapes under various loads without design assumptions. The TPO/MA method demonstrates superiority in handling nonlinear and barely stable systems, as evidenced by examples illustrating its efficacy in maintaining structural form under increasing loads and challenging conditions.Öğe A Novel Hybrid Harmony Search Approach for the Analysis of Plane Stress Systems via Total Potential Optimization(MDPI, 2020) Toklu, Yusuf Cengiz; Kayabekir, Aylin Ece; Bekdaş, Gebrail; Niğdeli, Sinan MelihBy finding the minimum total potential energy of a structural system with a defined degree of freedoms assigned as design variables, it is possible to find the equilibrium condition of the deformed system. This method, called total potential optimization using metaheuristic algorithms (TPO/MA), has been verified on truss and truss-like structures, such as cable systems and tensegric structures. Harmony Search (HS) algorithm methods perfectly found the analysis results of the previous structure types. In this study, TPO/MA is presented for analysis of plates for plane stress members to solve general types of problems. Due to the complex nature of the system, a novel hybrid Harmony Search (HHS) approach was proposed. HHS is the hybridization of local search phases of HS and the global search phase of the Flower Pollination Algorithm (FPA). The results found via HHS were verified with the finite element method (FEM). When compared with classical HS, HHS provides smaller total potential energy values, and needs less iterations than other new generation metaheuristic algorithms.Öğe Total Potential Optimization Using Metaheuristic Algorithms for Solving Nonlinear Plane Strain Systems(MDPI [Commercial Publisher], 2021) Toklu, Yusuf Cengiz; Bekdaş, Gebrail; Yücel, Melda; Niğdeli, Sinan Melih; Karabekir, Aylin Ece; Kim, Sanghun; Geem, Zong WooTotal Potential Optimization using Metaheuristic Algorithms (TPO/MA) is an alternative tool for the analysis of structures. It is shown that this emerging method is advantageous in solving nonlinear problems like trusses, tensegrity structures, cable networks, and plane stress systems. In the present study, TPO/MA, which does not need any specific implementation for nonlinearity, is demonstrated to be successfully applied to the analysis of plane strain structures. A numerical investigation is performed using nine different metaheuristic algorithms and an adaptive harmony search in linear analysis of a structural mechanics problem having 8 free nodes defined as design variables in the minimization problem of total potential energy. For nonlinear stress-strain relation cases, two structural mechanics problems, one being a thick-walled pipe and the other being a cantilever retaining wall, are analyzed by employing adaptive harmony search, which was found to be the best one in linear analyses. The nonlinear stress-strain relations considered in these analyses are hypothetical ones due to the lack of any such relationship in the literature. The results have shown that TPO/MA can solve nonlinear plane strain problems that can be encountered as engineering problems in structural mechanics.Öğe Tranfer function amplitude minimization for structures with tuned mass dampers considering soil-structure interaction(Elsevier Sci Ltd, 2019) Bekdas, Gebrail; Kayabekir, Aylin Ece; Nigdeli, Sinan Melih; Toklu, Yusuf CengizThe optimum tuned mass damper (TMD) parameters rely on the superstructure's natural frequency, which, in turn, depends on the soil condition under the structure. Thus, the consideration of soil conditions in determination of the optimum TMD parameters is necessary. In this study, a methodology is proposed for the determination of TMD parameters considering soil-structure interaction. The objective function in the study is the acceleration transfer function. For the stochastic optimization problem, several metaheuristic algorithms, namely harmony search, flower pollination algorithm, teaching, learning based optimization, Jaya algorithm and two new versions of it are employed. Numerical experiments on methodology are presented for a 40-story structure considering soil-structure interaction. It is shown through applications that, especially for soft soils, the use of TMDs is an effective way to damp structural vibrations resulting from seismic sources and consideration of the base stiffness is effective on the optimum TMD parameters. Comparisons among the results obtained through different metaheuristic algorithms are also given.
