Showing papers by "Grant P. Steven published in 1998"
TL;DR: In this article, the authors combine the basic ESO with the additive evolutionary structural optimisation (AESO) to produce bidirectional ESO whereby material can be added and can be removed.
Abstract: Describes development work to combine the basic ESO with the additive evolutionary structural optimisation (AESO) to produce bidirectional ESO whereby material can be added and can be removed. It will be shown that this provides the same results as the traditional ESO. This has two benefits, it validates the whole ESO concept and there is a significant time saving since the structure grows from a small initial one rather than contracting from a sometimes huge initial one where 90 per cent of the material gets removed over many hundreds of finite element analysis (FEA) evolutionary cycles. Presents a brief background to the current state of Structural Optimisation research. This is followed by a discussion of the strategies for the bidirectional ESO (BESO) algorithm and two examples are presented.
463 citations
TL;DR: In this article, the authors present an overview of the modelling that has been proposed by various workers in the field of smart or intelligent structures, and present the main objective of this article.
Abstract: The main objective of this article is to present an overview of the modelling that has been proposed by various workers in the field of smart or intelligent structures. Before the main discussion o...
309 citations
TL;DR: In this paper, the problem of finding the optimum thickness distribution of isotropic plate structures, with a given volume and layout, that would maximise the buckling load is discussed.
65 citations
TL;DR: In this paper, a unit cell model and a laminate model are presented for predicting engineering elastic constants of 3D orthogonal woven composites, and one finite element analyzes the model.
Abstract: In this paper, a unit cell model and a laminate model are presented for predicting engineering elastic constants of 3D orthogonal woven composites. For the unit cell model, one finite element analy...
64 citations
TL;DR: In this paper, a simple evolutionary method for minimizing the weight of structures subject to displacement constraints is presented, where sizing design variables are discrete and sensitivity numbers for element size reduction are derived using optimality criteria methods.
36 citations
TL;DR: Posteroanterior stiffness varies along the spine in a manner consistent with the nature of support for the spine, and appears to be influenced by some factors other than those relating to the spine.
Abstract: Background and Purpose. Evaluation of posteroanterior (PA) movement in the spine is commonly used in the clinic, but little is known about the mechanisms involved. The purposes of this study were to examine variations in PA stiffness along the thoracolumbar spine and to investigate possible factors that might determine the pattern of stiffness. Subjects. Twenty-one pain-free volunteers (10 male, 11 female), aged 18 to 41 years (X=26.6, SD=7.5), participated. Methods. Posteroanterior stiffness was measured at 5 locations (L4, L1, T10, T7, T4), together with various subject characteristics. Results. Mean PA stiffness varied among locations, with the greatest stiffness at L4 (13.3 N/mm) and the lowest stiffness at L1 (10.4 N/mm). A relatively small, but important, proportion (22% or less) of the variance in stiffness data at some vertebral levels was accounted for by the variables describing subject characteristics. Conclusion and Discussion. Posteroanterior stiffness varies along the spine in a manner consistent with the nature of support for the spine. The observed pattern of variation of PA stiffness along the spine appears to be influenced by some factors other than those relating to the spine.
36 citations
TL;DR: In this paper, a generalized evolutionary method is proposed to define structures that utilize their construction material to the greatest effect in the finite element sense, by basing the successive element erosion upon the contribution of an element to the strain energy of a structure and a certain material efficiency indicator.
Abstract: Generalized evolutionary methods, which successively construct and solve static equilibrium problems with progressive mesh adaptation, are useful tools for defining structures that utilize their construction material to greatest effect in the finite element sense. By basing the successive element erosion upon (i) the contribution of an element to the strain energy of a structure and (ii) a certain material efficiency indicator of a structure, several weaknesses associated with previous methods have been overcome. Under static loading conditions, the strain energy contribution of an element is determined solely by the related stiffness and displacement vector. Consequently, the method is effective, and efficient when applied to problems involving such loading conditions. The efficacy of the method is demonstrated through numerical applications to the problem of optimizing the topologies of two structures, a cantilever structure and a Michell structure
34 citations
02 Sep 1998
19 citations
TL;DR: In this article, the contribution factor of an element to the natural frequency of the finite element discretized system of a membrane vibration problem is derived from the general finite element formulation of structural eigenvalue problems, and the method associated with it is called as a generalized evolutionary method.
15 citations
02 Sep 1998
TL;DR: In this paper, the Evolutionary Structural Optimization (ESO) was employed for shape optimization of two-dimensional elastic contact problems, which involves a simple evolutionary and re-meshing procedure based on finite element analysis, in which contact profiles are iteratively modified in terms of the relative levels of contact stress.
Abstract: In this study, the Evolutionary Structural Optimization (ESO) is employed for the shape optimization of twodimensional elastic contact problems. This method involves a simple evolutionary and re-meshing procedure based on finite element analysis, in which contact profiles are iteratively modified in terms of the relative levels of contact stress. Through this procedure the high stress concentration on the contact surfaces is progressively reduced and thereby the contact stress distribution evolves towards uniform or some other predetermined patterns. The design examples of contact profiles are presented herein to demonstrate the capabilities of the ESO method for solving two-dimensional contact problems.
3 citations
02 Sep 1998
TL;DR: Results indicate that the method is able to produce the optimal shape of the cables and the arch that provides the best function for the cable-stayed and the tied arch bridges.
Abstract: This paper presents the optimal design of cablestayed and tied arch bridges. Based on the evolutionary optimization technique, a new element removal scheme is proposed which takes into account both the stress and displacement constraints. The recently developed principal stress criteria and the displacement sensitivity number are used respectively for the stress and displacement controls. For two types of bridges, results indicate that the method is able to produce the optimal shape of the cables and the arch that provides the best function for the cable-stayed and the tied arch bridges.