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http://hdl.handle.net/2433/10
Mon, 21 Jan 2019 21:42:23 GMT2019-01-21T21:42:23ZMachine learning for combinatorial optimization of brace placement of steel frames
http://hdl.handle.net/2433/236063
タイトル: Machine learning for combinatorial optimization of brace placement of steel frames
著者: Tamura, Takuya; Ohsaki, Makoto; Takagi, Jiro
抄録: A method is presented for optimal placement of braces of plane frames using machine learning. The frame is subjected to static horizontal loads representing seismic loads. We consider the process of seismic retrofit by attaching braces. Therefore, the maximum value of additional stresses in the existing beams and columns and the maximum interstory drift angle are incorporated in the optimization problem. Characteristics of approximate optimal solutions and nonoptimal solutions are extracted using machine learning based on support vector machine and binary decision tree. Convolution and pooling are used for defining the features characterizing the solutions while reducing the number of variables. Optimization is carried out using a heuristic algorithm called simulated annealing based on local search. It is shown in the numerical examples that the computational cost is successfully reduced by avoiding costly structural analysis for a solution judged by machine learning as nonoptimal, and the important features in approximate optimal and nonoptimal solutions are identified.Mon, 01 Oct 2018 00:00:00 GMThttp://hdl.handle.net/2433/2360632018-10-01T00:00:00ZSecond-Order Cone Programming Approach to Design of Linkage Mechanisms With Arbitrarily Inclined Hinges
http://hdl.handle.net/2433/236062
タイトル: Second-Order Cone Programming Approach to Design of Linkage Mechanisms With Arbitrarily Inclined Hinges
著者: Ohsaki, Makoto; Kanno, Yoshihiro; Yamaoka, Yuki
抄録: An optimization approach is presented for generating linkage mechanisms consisting of frame members with arbitrarily inclined hinges. A second-order cone programming (SOCP) problem is solved to obtain the locations and directions of hinges of an infinitesimal mechanism. It is shown that the primal and dual SOCP problems correspond to the plastic limit analysis problems based on the lower-bound and upper-bound theorems, respectively, with quadratic yield functions. Constraints on displacement components are added to the dual problem, if a desirable deformation is not obtained. A finite mechanism is generated by carrying out geometrically nonlinear analysis and, if necessary, adding hinges and removing members. Effectiveness of the proposed method is demonstrated through examples of two- and three-dimensional mechanisms.Mon, 30 Jul 2018 00:00:00 GMThttp://hdl.handle.net/2433/2360622018-07-30T00:00:00ZStopping rule of multi-start local search for structural optimization
http://hdl.handle.net/2433/236061
タイトル: Stopping rule of multi-start local search for structural optimization
著者: Ohsaki, Makoto; Yamakawa, Makoto
抄録: Stopping rule for multi-start local search is investigated for application to structural optimization problems with moderately large number of local optima. The size of attractor of an unknown local optimal solution is estimated using the information of already obtained solutions. A stopping rule is defined using the likelihood of obtaining the specific set of local optimal solutions. This way, characteristics of the specific optimization problem is successfully incorporated. The proposed rule is first verified using the mathematical problems in comparison with the existing rule utilizing the estimated ratio of the total size of attractors to the size of feasible domain. The rule is next applied to an optimization problem of a plane frame under constraints on inter-story drift angle and stress against static loads. Characteristics of the distribution of attractors of optimal solutions are also investigated.Thu, 01 Feb 2018 00:00:00 GMThttp://hdl.handle.net/2433/2360612018-02-01T00:00:00ZSeries expansion method for determination of order of 3-dimensional bar-joint mechanism with arbitrarily inclined hinges
http://hdl.handle.net/2433/236060
タイトル: Series expansion method for determination of order of 3-dimensional bar-joint mechanism with arbitrarily inclined hinges
著者: Watada, Ryo; Ohsaki, Makoto
抄録: A general method for evaluating the order of infinitesimal mechanism is presented for 3-dimensional bar-joint mechanism, which is defined as assembly of rigid bars connected to nodes by hinges with arbitrarily inclined directions. Compatibility conditions of translations and rotations are derived at bar-ends with respect to the generalized displacements consisting of displacements and rotations of nodes and bars. Degree of kinematic indeterminacy is computed using singular value decomposition of the linearized compatibility matrix. The order of infinitesimal mechanism is determined by the existence condition of higher-order coefficients of the generalized displacements with respect to the path parameter of deformation. The coefficients are obtained in a similar manner as stability analysis of geometrically nonlinear structures, where symbolic computation software package is used for analytical derivation of equations. The detailed procedure of analysis is shown through the numerical examples of a two-bar and a four-bar linkages, and the results are verified using a finite element analysis software.Fri, 01 Jun 2018 00:00:00 GMThttp://hdl.handle.net/2433/2360602018-06-01T00:00:00Z