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Studies in optimization as an aid to circuit synthesis and design
Describes some of the limitations and difficulties of the finite element method and discusses implications in relation to the analysis of bridge and building structures. The main limitations of the method are related to difficulties encountered in: (i) cost; (ii) complexity; (iii) convergence problems and approximations: (iv) computer storage requirements and (v) associated communication problems. lezernik, A. and Miller, M.C. 75.15 Large user-oriented systems of programs for structural analysis and design' Nuclear Eng. and Des. Vol 27 No 2 (May 1974) pp 238 273 Kamel, H. A. amd McCabe, M.W. 75.16 'Graphics oriented interactive finite element timesharing packages (GIFTS)' Arizona University, Aerospace & Mechanical Engineering Dept., Tuscon USA (July 1973) 7O pp Describes a general purpose analysis package (GIFTS) aimed primarily at ship structure design using the finite element method on a timesharing system. Although the project was started with ship structures in mind, the concept has developed in such a manner as to offer a solution to other problems related to finite element analysis. The end product should provide a nation-wide communication system between users enabling them to exchange data, results and programs with relative ease. The system acknowledges and utilizes some of the latest developments in computer technology, namely, timesharing, cheap graphics teraainals, and computer networks. It also may be used advantageously with minicomputers. Lewis, D. J. and Hellen, T . K . 75.17 'Analysis techniques for elevated temperature applications' Central Electricity Generating Board, Berkeley, UK (December 1973) 51 pp A review is given of some of the more generally used methods of analysis of stress and ~train in structures at elevated tenrperatures, with particular emphasis on finite element methods. It is shown that where iufficiently large computers are available, and where cost is not a severe limitation, creep and plasticity behaviour can be computed for a wide range of components. Where these effects are encountered simultaneously, more knowledge of materials t~ehaviour is required. Calculation of stress and strain is usually only a means to the Jesigner's main aim, which is proving the tifc and integrity of his structure. The short:omings of computational methods in this respect are discussed, and a brief review is given of some of the 'short cut' methocts of tifc assessment available to the designer. McConnel, R . E . 75.18 'Volume optimization of pin-jointed frameworks with variable nodal positions' Oxford University, Engineering Science Dept., UK (October 1973) 34 pp The minimum weight design of pin-jointed frameworks with fixed topology but variable node position is considered. Expressions are obtained for a weight function in terms of the structural variables, and restrictions are quoted on the types of structures for which these expressions are valid. A routine to calculate the weight of such
Volume7
Number 1
January 1975
frameworks is developed in terms of the free node positions, and a computer program to minimize this weight function is presented. Possible extension of the method beyond the restricted class of structures defined is discussed and example calculations are given. The equilibrium equations used by the computer program are listed and the specifications of this program is given. Melosh, R . J . 75.19 'Status report on computational techniques for finite element analyses' Nuclear Eng. and Des. Vol 27 No 2 (May 1974) pp 2 7 4 - 2 8 5 Mondkar, D. P. and Powell, G . H . 75.20 'Towards optimal in-core equation solving' Comput. & Struct., Vol 4, No 3 (May 1974) pp 5 3 1 - 5 4 8 A review is given of equation solving algorithms based on Gauss elimination. A modified Grout reduction procedure of almost optimal efficiency is presented, written in Fortran, for sparsely populated coefficient matrices that are c o m m o n in stiffness analysis of structural systems. Robins, P. J. and Kong, F . K . 75.21 'Modified finite element method applied to RC deep beams' Civil Eng, and Public Works Rev. Vol 68 (1973) No 808 pp 963--6 Deals with the modifications made in an attempt to develop a theoretical model to simulate the post-cracking behaviour of reinforced concrete deep beams. The modifications include (i) the inclusion of a nonlinear stress-strain relation for the concrete; (ii) a method to allow for progressive cracking of the concrete to the beam; (iii) the inclusion of a 'spring linkage element' to simulate the bond between the steel and the concrete; and (iv) a simple method for the representation of web reinforcements. Turcke, D. J. and McNeile, G.M. 75.22 'Guidelines for selecting finite element grids based on an optimization study' C o m p u t and Struct, Vol 4, No 3 (May 1974) pp 4 9 9 - 5 1 9 The paper concentrates on the introduction of nodal co-ordinates as independent unknowns, in addition to nodal displacements which have previously characterized the method. A study is made of o p t i m u m grids in two-dimensional plane stress problems from which guidelines are suggested such that near o p t i m u m grids can be selected by the analyst. These grids lead to improve'l stresses and displacements. Vahl, T. 75.23 'Present and future possibilities within computer-aided design' Comput. and Struct. Vol 4 No 1 (January 1974) pp 115 130
Electrical and electronic
engineering Adams, R . N . 75.24 'Interactive use of a computer program for the design of MV cable networks' Electricity Council, London, UK (January 1974) 16 pp As part of a wider study of computer applications in network design, the Capenhurst MV network design program was adapted for use on an online interactive computing system operating from remote teletype
terminals. Programming requirements are broadly outlined and it is suggested that for design applications of this type in which the final solution emerges in a sequence of improvements, the interactive mode of operation can offer significant advantages over conventional batch processing. An example of terminal printer o u t p u t for a small design exercise and a glossary of c o m m o n terms used in this branch of computing are included as appendices.
Kawasaki, T. 75.25 'Optimal Networks with NOR-OR gates and wired-OR logic' Illinois University, Computer Science Dept. Urbana, USA (Jan 1974) 102 pp Using gates (ECL) with dual outputs and wired-ORs, an algorithm to get the optimal networks, ie, those which have a minimum number of NOR-OR gates and, as the secondary objective, a minimum number of connections, for a given arbitrary function, is discussed in this paper, under the assumption that only non-complemented variables are available as the network inputs.
Wright, D . J . 75.26 'Studies in optimization as an aid to circuit synthesis and design' Ph.D Thesis, University of Leicester (July 1974) Concerned with the application of optimization techniques in the design of lumped, linear, passive, two port networks. In particular, the thesis considers the problem where the trial, starting network is remote from any acceptable solution and, possibly, unable to realize the design requirements without substantial topological alterations. The early aims of the research set out to automate these topological modifications using a logical sequence of changes. An online Marquardt-Levenberg nonlinear least squares algorithm was developed where decisions involving the more nebulous aspects of optimization could be made at run-time, (e.g. linear search qualities, convergence criteria etc). Pole-zero matching was used to study a new network modification process known as the 'generalized growth strategy' and adapted for an online environment. A little qualitative progress was made towards an understanding of network modification processes but most of the results concerned the generation of novel network equivalents. Attempts to quantify the - .ion of problem ill-conditioning and tLe dangers of variable transformations (used to produce realizable solutions) were also made. A final study involved the lumped elemen simulation of a coaxial cable in the frequency domain (1/2 Mttz-1 GHz) where no obvious trial starting network existed. The online approach, proved to be a vital asset particularly for allowing run-time changes to the error weighting strategy. The results obtained were impressive but the design approach was difficult to formulate and acted as an aid to the manual design rather than a replacement of it. In conclusion, in the long term, greater consideration should be given to a study of multi-modality and non-deterministic processes. In the short term, online working is worth further exploitation possibly incorporating use of graphical terminals for monitoring frequency characteristics.
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Volume7
Number 1
January 1975
frameworks is developed in terms of the free node positions, and a computer program to minimize this weight function is presented. Possible extension of the method beyond the restricted class of structures defined is discussed and example calculations are given. The equilibrium equations used by the computer program are listed and the specifications of this program is given. Melosh, R . J . 75.19 'Status report on computational techniques for finite element analyses' Nuclear Eng. and Des. Vol 27 No 2 (May 1974) pp 2 7 4 - 2 8 5 Mondkar, D. P. and Powell, G . H . 75.20 'Towards optimal in-core equation solving' Comput. & Struct., Vol 4, No 3 (May 1974) pp 5 3 1 - 5 4 8 A review is given of equation solving algorithms based on Gauss elimination. A modified Grout reduction procedure of almost optimal efficiency is presented, written in Fortran, for sparsely populated coefficient matrices that are c o m m o n in stiffness analysis of structural systems. Robins, P. J. and Kong, F . K . 75.21 'Modified finite element method applied to RC deep beams' Civil Eng, and Public Works Rev. Vol 68 (1973) No 808 pp 963--6 Deals with the modifications made in an attempt to develop a theoretical model to simulate the post-cracking behaviour of reinforced concrete deep beams. The modifications include (i) the inclusion of a nonlinear stress-strain relation for the concrete; (ii) a method to allow for progressive cracking of the concrete to the beam; (iii) the inclusion of a 'spring linkage element' to simulate the bond between the steel and the concrete; and (iv) a simple method for the representation of web reinforcements. Turcke, D. J. and McNeile, G.M. 75.22 'Guidelines for selecting finite element grids based on an optimization study' C o m p u t and Struct, Vol 4, No 3 (May 1974) pp 4 9 9 - 5 1 9 The paper concentrates on the introduction of nodal co-ordinates as independent unknowns, in addition to nodal displacements which have previously characterized the method. A study is made of o p t i m u m grids in two-dimensional plane stress problems from which guidelines are suggested such that near o p t i m u m grids can be selected by the analyst. These grids lead to improve'l stresses and displacements. Vahl, T. 75.23 'Present and future possibilities within computer-aided design' Comput. and Struct. Vol 4 No 1 (January 1974) pp 115 130
Electrical and electronic
engineering Adams, R . N . 75.24 'Interactive use of a computer program for the design of MV cable networks' Electricity Council, London, UK (January 1974) 16 pp As part of a wider study of computer applications in network design, the Capenhurst MV network design program was adapted for use on an online interactive computing system operating from remote teletype
terminals. Programming requirements are broadly outlined and it is suggested that for design applications of this type in which the final solution emerges in a sequence of improvements, the interactive mode of operation can offer significant advantages over conventional batch processing. An example of terminal printer o u t p u t for a small design exercise and a glossary of c o m m o n terms used in this branch of computing are included as appendices.
Kawasaki, T. 75.25 'Optimal Networks with NOR-OR gates and wired-OR logic' Illinois University, Computer Science Dept. Urbana, USA (Jan 1974) 102 pp Using gates (ECL) with dual outputs and wired-ORs, an algorithm to get the optimal networks, ie, those which have a minimum number of NOR-OR gates and, as the secondary objective, a minimum number of connections, for a given arbitrary function, is discussed in this paper, under the assumption that only non-complemented variables are available as the network inputs.
Wright, D . J . 75.26 'Studies in optimization as an aid to circuit synthesis and design' Ph.D Thesis, University of Leicester (July 1974) Concerned with the application of optimization techniques in the design of lumped, linear, passive, two port networks. In particular, the thesis considers the problem where the trial, starting network is remote from any acceptable solution and, possibly, unable to realize the design requirements without substantial topological alterations. The early aims of the research set out to automate these topological modifications using a logical sequence of changes. An online Marquardt-Levenberg nonlinear least squares algorithm was developed where decisions involving the more nebulous aspects of optimization could be made at run-time, (e.g. linear search qualities, convergence criteria etc). Pole-zero matching was used to study a new network modification process known as the 'generalized growth strategy' and adapted for an online environment. A little qualitative progress was made towards an understanding of network modification processes but most of the results concerned the generation of novel network equivalents. Attempts to quantify the - .ion of problem ill-conditioning and tLe dangers of variable transformations (used to produce realizable solutions) were also made. A final study involved the lumped elemen simulation of a coaxial cable in the frequency domain (1/2 Mttz-1 GHz) where no obvious trial starting network existed. The online approach, proved to be a vital asset particularly for allowing run-time changes to the error weighting strategy. The results obtained were impressive but the design approach was difficult to formulate and acted as an aid to the manual design rather than a replacement of it. In conclusion, in the long term, greater consideration should be given to a study of multi-modality and non-deterministic processes. In the short term, online working is worth further exploitation possibly incorporating use of graphical terminals for monitoring frequency characteristics.
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