The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform

Makoto Ohsaki - One of the best experts on this subject based on the ideXlab platform.

  • SIMULTANEOUS OPTIMIZATION OF TOPOLOGY AND NODAL LOCATIONS OF A Plane Truss ASSOCIATED WITH BEZIER CURVE
    1999
    Co-Authors: Makoto Ohsaki, Y Kato
    Abstract:

    A method is presented for simultaneous optimization of topology and geometry of an arch-type Plane Truss modeled by a Bezier curve. Explicit geometrical constraints are given to prevent existence of practically inadmissible shape, and optimal topologies and nodal locations are found by using a genetic algorithm. It is shown that the proposed operator of mutation is effectively used for local search among the Trusses with the same topology, and practically admissible optimal shape is found by introducing the geometrical constraints.

  • Shape-Size Optimization of Plane Trusses with Designer’s Preference
    Journal of Structural Engineering-asce, 1998
    Co-Authors: Makoto Ohsaki, Tsuneyoshi Nakamura, Y. Isshiki
    Abstract:

    This paper describes a new method for shape and member-size optimization of a Plane Truss by using techniques of parametric curves. Description of nodal coordinates as well as cross-sectional areas in terms of Bezier curves enables one to find a smooth optimal Truss. The optimal Truss is found under the constraints such that all the response strains to multiple design loads including static loads and earthquake excitation are within a prescribed range. The objective function to be minimized is a weighted sum of the total structural mass and the deviation of the shape from the one preferred by the designer. The latter is written explicitly in terms of the coordinates of the control points. Side constraints are easily incorporated based on the convex hull property of the Bezier curve. In the examples, optimal Trusses are found under single and multiple loading conditions and the characteristics of the optimal Trusses in reference to the weight coefficients are discussed.

  • simultaneous optimization of topology and geometry of a regular Plane Truss
    Computers & Structures, 1998
    Co-Authors: Makoto Ohsaki
    Abstract:

    Abstract An algorithm is presented for simultaneous optimization of geometry and topology of a regular Plane Truss with uniform cross-sectional area. Difficulties arising from singularity and discontinuity in eliminating unnecessary members and nodes from the ground structure are discussed in detail by using a cantilever-type Plane Truss. Note that the optimization problem becomes more complicated by limiting the feasible designs to regular Trusses with uniform cross-sectional areas. In the proposed method, a pin-jointed Truss is first modeled as a rigidly jointed frame. A sigmoid function is used for modeling continuous transition between frames with different topologies. In this manner, coalescent nodes and members are successfully removed from the initial ground structure. In the examples, optimal solutions are found for a rectangular Plane Truss which consists of rectangular units, and the effect of nodal cost on the optimal topology is discussed.

T. Birker - One of the best experts on this subject based on the ideXlab platform.

  • Generalized Michell structures — exact least-weight Truss layouts for combined stress and displacement constraints: Part I — General theory for Plane Trusses
    Structural Optimization, 1995
    Co-Authors: George I. N. Rozvany, T. Birker
    Abstract:

    In Part I of this study, earlier results are briefly reviewed and then general optimality criteria derived for exact leastweight Plane Truss layouts with combined stress and displacement constraints. Whilst these are necessary conditions for a local minimum with respect toany topology, Part II discusses analytical solutions within agiven two-bar topology for a vertical support and a point load. The latter results are used for verifying the general theory in Part I.

  • generalized michell structures exact least weight Truss layouts for combined stress and displacement constraints part i general theory for Plane Trusses
    Structural Optimization, 1995
    Co-Authors: G I N Rozvany, T. Birker
    Abstract:

    In Part I of this study, earlier results are briefly reviewed and then general optimality criteria derived for exact leastweight Plane Truss layouts with combined stress and displacement constraints. Whilst these are necessary conditions for a local minimum with respect toany topology, Part II discusses analytical solutions within agiven two-bar topology for a vertical support and a point load. The latter results are used for verifying the general theory in Part I.

  • A well-posed non-selfadjoint layout problem: Least-weight Plane Truss for one load condition and two displacement constraints
    Structural Optimization, 1994
    Co-Authors: T. Birker, T. Lewiński, George I. N. Rozvany
    Abstract:

    Exact optimal Plane Truss layouts are derived for a vertical support and a concentrated load with two displacement constraints. The latter are imposed at the point of application of the load, in the direction of the load and in another direction. It is shown that for the above class of problems the optimal solution always consists of two symmetrically positioned bars. These solutions are derived analytically by two independent methods: (i) in the first one a two-bar topology is assumed and then the orientations and cross-sectional areas of the bars are optimized; (ii) in the second one, the same optimal solutions are derived from general optimality criteria, which show that the optimum is valid even when we consider all possible topologies. The paper demonstrates the power and versatility of continuum-type optimality criteria and also shows that for two displacement constraints at a loaded point the problem is non-selfadjoint but always well-posed, having a stationary optimum with a finite structural weight. The exact layout solutions given in this paper can be used as test examples for numerical methods in topology optimization.

  • Some unexpected properties of exact least-weight Plane Truss layouts with displacement constraints for several alternate loads
    Structural Optimization, 1994
    Co-Authors: George I. N. Rozvany, T. Birker, T. Lewiński
    Abstract:

    Basic geometrical properties of optimal Plane Truss layouts for multiple displacement constraints and several load conditions are derived. These include the feature that at any point, optimal bars may run in at most two directions and that even for two nonsymmetric alternative loads at the same point the optimal two-bar layout is always symmetrical for a vertical support. The above general findings are illustrated with examples, in which the results are derived by several independent methods, including a proof of global optimality of the layout.

Harry H. West - One of the best experts on this subject based on the ideXlab platform.

  • Fundamentals of Structural Analysis
    European Journal of Engineering Education, 1993
    Co-Authors: Harry H. West
    Abstract:

    There are two new developments in the last twenty years in the civil engineering curricula that have a direct bearing on the design of the content of a course in structural analysis: the reduction of credit hours to three required hours in structural analysis in most civil engineering curricula and the increasing gap between what is taught in textbooks and classrooms and what is being practiced in engineering firms. The former is brought about by the recognition of civil engineering educators that structural analysis as a required course for all civil engineering majors need not cover in great detail all the analytical methods. The latter is certainly the result of the ubiquitous applications of personal digital computer. This structural analysis text is designed to bridge the gap between engineering practice and education. Acknowledging the fact that virtually all computer structural analysis programs are based on the matrix displacement method of analysis, the text begins with the matrix displacement method. A matrix operations tutorial is included as a review and a self-learning tool. To minimize the conceptual difficulty a student may have in the displacement method, it is introduced with Plane Truss analysis, where the concept of nodal displacements presents itself. Introducing the matrix displacement method early also makes it easier for students to work on term project assignments that involve the utilization of computer programs. The force method of analysis for Plane Trusses is then introduced to provide the coverage of force equilibrium, deflection, statical indeterminacy, etc., that are important in the understanding of the behavior of a structure and the development of a feel for it. The force method of analysis is then extended to beam and rigid frame analysis, almost in parallel to the topics covered in Truss analysis. The beam and rigid frame analysis is presented in an integrated way so that all the important concepts are covered concisely without undue duplicity. The displacement method then re-appears when the moment distribution and slope- deflection methods are presented as a prelude to the matrix displacement method for beam and rigid frame analysis. The matrix displacement method is presented as a generalization of the slope-deflection method. The above description outlines the introduction of the two fundamental methods of structural analysis, the displacement method and the force method, and their applications to the two groups of structures, Trusses and beams-and-rigid frames. Other related topics such as influence lines, non-prismatic members, composite structures, secondary stress analysis, limits of linear and static structural analysis are presented at the end.

Xinong Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Chapter 28 Nonlinear Self-Defined Truss Element Based on the Plane Truss Structure with Flexible Connector
    2020
    Co-Authors: Xinong Zhang, Minglong Xu
    Abstract:

    A finite-element method based on the self-defined Truss element is developed and used to model the Plane Truss structure with the flexible connector, moreover, the dynamic characteristic of the corresponding model is analyzed in this paper. Firstly, a kind of new type Truss structure is analyzed where the flexible connectors between Trusses include clearance effects. A self-defined Truss element is defined based on the mechanical analysis and then used to build the finite-element model. And the nonlinear elastic-damper model and the Coulomb friction model are adopted to analyze the nonlinear nodal forces from the clearance field. Secondly, a nonlinear numerical solution method is developed based on the Newmark implicit integrate method together with Newton-Raphson iterated method and then used to solve the nonlinear dynamic model. Finally a numerical example is performed by the method above and the effects of several key parameters (such as the contact stiffness and the clearance) on the dynamic characteristic are analyzed. The results validate the numerical solution method and show that the nonlinear finite-element model is effective.

  • nonlinear self defined Truss element based on the Plane Truss structure with flexible connector
    Communications in Nonlinear Science and Numerical Simulation, 2010
    Co-Authors: Minglong Xu, Xinong Zhang
    Abstract:

    A finite-element method based on the self-defined Truss element is developed and used to model the Plane Truss structure with the flexible connector, moreover, the dynamic characteristic of the corresponding model is analyzed in this paper. Firstly, a kind of new type Truss structure is analyzed where the flexible connectors between Trusses include clearance effects. A self-defined Truss element is defined based on the mechanical analysis and then used to build the finite-element model. And the nonlinear elastic-damper model and the Coulomb friction model are adopted to analyze the nonlinear nodal forces from the clearance field. Secondly, a nonlinear numerical solution method is developed based on the Newmark implicit integrate method together with Newton–Raphson iterated method and then used to solve the nonlinear dynamic model. Finally a numerical example is performed by the method above and the effects of several key parameters (such as the contact stiffness and the clearance) on the dynamic characteristic are analyzed. The results validate the numerical solution method and show that the nonlinear finite-element model is effective.

Marcin Marek Kamiński - One of the best experts on this subject based on the ideXlab platform.

  • A generalized stochastic perturbation technique for plasticity problems
    Computational Mechanics, 2009
    Co-Authors: Marcin Marek Kamiński
    Abstract:

    The main aim of this paper is to present an algorithm and the solution to the nonlinear plasticity problems with random parameters. This methodology is based on the finite element method covering physical and geometrical nonlinearities and, on the other hand, on the generalized n th order stochastic perturbation method. The perturbation approach resulting from the Taylor series expansion with uncertain parameters is provided in two different ways: (i) via the straightforward differentiation of the initial incremental equation and (ii) using the modified response surface method. This methodology is illustrated with the analysis of the elasto-plastic Plane Truss with random Young’s modulus leading to the determination of the probabilistic moments by the hybrid stochastic symbolic-finite element method computations.