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Showing papers on "Minimum weight published in 1988"


Journal ArticleDOI
01 Jan 1988
TL;DR: In this paper, an approximate structural analysis based on first order Taylor series expansions of the member forces is proposed to minimize the weight of the truss. But this method is limited to two-and three-dimensional elastic trusses.
Abstract: Two- and three-dimensional elastic trusses are designed for minimum weight by varying the areas of the members and the location of the joints. Constraints on member stresses and Euler buckling are imposed and multiple static loading conditions are considered. The method presented here utilizes an approximate structural analysis based on first order Taylor series expansions of the member forces. A numerical optimizer minimizes the weight of the truss using information from the approximate structural analysis. Comparisons with results from other methods are made. It is shown that the method of forming an approximate structural analysis based on linearized member forces leads to a highly efficient method of truss configuration optimization.

92 citations


Journal ArticleDOI
TL;DR: In this article, an integrated structural/control optimum design algorithm is presented to modify the structural design variables to improve the dynamic response of a space structure with constraints on the damping parameters and the frequency distribution of the closed-loop system.
Abstract: An integrated structural/control optimum design algorithm is presented. The algorithm can be used to modify the structural design variables to improve the dynamic response of a space structure with constraints on the damping parameters and the frequency distribution of the closed-loop system. The method used a nonlinear mathematical programming approach to obtain a structure with minimum weight that satisfies all the constraints. Application of the algorithm is illustrated by designing a truss structure.

60 citations


Journal ArticleDOI
TL;DR: It is shown that any algorithm that solves the FAS problem or the vertex-weighted FVS problem on reducible flow graphs has time complexity at least that of finding a minimum cut in a flow network, for which the best algorithms currently known have time complexity.

60 citations


Journal ArticleDOI
TL;DR: This paper presents a lower bound on the minimum weight of a binary image of a cyclic code over GF(2 m) and the weight enumerator for abinary image of the extended (2 m ,2 m − 4) code of the Reed-Solomon code overGF( 2 m ) with generator polynomial.

41 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a brief review of the relevant literature along with the procedures adopted, results and conclusions for singly and doubly reinforced beams, T-beams and columns with eccentric loads.

36 citations


Journal ArticleDOI
TL;DR: In this paper, an integrated approach to the minimum weight design of geometrically nonlinear three-dimensional truss structures with geometric imperfections, subject to inequality constraints on static displacements, stresses, local buckling and cross sectional areas, is investigated.
Abstract: An integrated approach to the minimum weight design of geometrically nonlinear three-dimensional truss structures with geometric imperfections, subject to inequality constraints on static displacements, stresses, local buckling and cross sectional areas, is investigated. The integrated structural synthesis problem involves design and response quantities as independent variables and equilibrium equations, describing the finite element model, as equality constraints. The nonlinear structural analysis and the optimization are thus merged together into a single process. A computer program developed to compute the constraint values and analytical gradients is coupled with a generalized reduced gradient algorithm to solve the integrated problem. Numerical results for a geometrically nonlinear shallow dome example problem are presented for various types of imperfections. Furthermore, it is found that the algorithm is capable of detecting and guarding against system as well as element elastic instability using equilibrium information only, that is, without imposing system and local buckling inequality constraints.

35 citations


01 Feb 1988
TL;DR: In this paper, the minimum weight design of a helicopter rotor blade subject to constraints on coupled flap-lag natural frequencies has been studied, and a constraint has also been imposed on the minimum value of the autorotational inertia of the blade in order to ensure that it has sufficient inertia to auto-otate in the case of engine failure.
Abstract: The minimum weight design of a helicopter rotor blade subject to constraints on coupled flap-lag natural frequencies has been studied. A constraint has also been imposed on the minimum value of the autorotational inertia of the blade in order to ensure that it has sufficient inertia to autorotate in the case of engine failure. The program CAMRAD is used for the blade modal analysis and CONMIN is used for the optimization. In addition, a linear approximation analysis involving Taylor series expansion has been used to reduce the analysis effort. The procedure contains a sensitivity analysis which consists of analytical derivatives of the objective function and the autorotational inertia constraint and central finite difference derivatives of the frequency constraints. Optimum designs have been obtained for both rectangular and tapered blades. Design variables include taper ratio, segment weights, and box beam dimensions. It is shown that even when starting with an acceptable baseline design, a significant amount of weight reduction is possible while satisfying all the constraints for both rectangular and tapered blades.

18 citations


Journal ArticleDOI
TL;DR: In this paper, different formulations for minimum weight plastic design of structural frames are discussed with reference to the inclusion of tapered members in the optimisation process and an equilibrium method is presented in more detail showing how pinjoints can be taken into account and plastic moment constraints imposed.

16 citations


Journal ArticleDOI
TL;DR: This paper provides a method for determining these “exceptional” characteristics, and the corresponding minimum weights, for quadratic-residue (QR) codes of modest length, and can be used to examine the t -designs derived from the codewords of minimum weight.

15 citations


Journal ArticleDOI
TL;DR: The minimum weight design of circular conical concrete water tanks is studied in this paper, where the internal base radius, the depth and the semi-vertical angle of the cone are fixed while the thickness of the wall along the length is varied so that the bending (tensile) and hoop stresses attain values as close as possible to their respective allowable values.

12 citations


Book ChapterDOI
01 Jan 1988
TL;DR: In this paper, the authors describe two approaches to the design of a structure and its control system in an optimum manner, where the primary objective is to modify the structural stiffness by changing the cross-sectional areas of the members in order to achieve a minimum weight structure and the desired distribution of the closed-loop eigenvalues and structural frequencies.
Abstract: This paper will describe two approaches to the design of a structure and its control system in an optimum manner. The primary objective would be to modify the structural stiffness by changing the cross-sectional areas of the members in order to achieve a minimum weight structure and the desired distribution of the closed-loop eigenvalues and structural frequencies. The application of both methods is illustrated on truss structures.




Journal Article
TL;DR: In this paper, a direct practical method of design for regular moment frames subjected to lateral loading is developed for both elastic and plastic ranges of stress and results in a minimum weight solution for all stages of loading.
Abstract: A direct practical method of design is developed for regular moment frames subjected to lateral loading. The method is applicable to both elastic and plastic ranges of stress and results in a minimum weight solution for all stages of loading. It is shown how this method of material selection results in minimum drift for the given loading and geometry. Several numerical examples are described to illustrate the simplicity and usefulness of the concept. The concept is recommended for preliminary member sizing before satisfying other pertinent design criteria.

Book ChapterDOI
02 Nov 1988
TL;DR: An upper bound for the minimum distance of the q-ary image of a linear code of MDS codes over GF(qs) when q=2 and q=3 is given.
Abstract: In this paper we give an upper bound for the minimum distance of the q-ary image of a linear code over GF(qs) This allows us to give some indications about the minimum distance of the q-ary image of MDS codes over GF(qs) when q=2 and q=3

Proceedings ArticleDOI
01 Jan 1988
TL;DR: In this article, a method for the minimum weight design of helicopter rotor blades having multiple coupled flap-lag natural frequency constraints, in addition to a constraint on the minimum blade autorotation value that will ensure sufficient rotary inertia for auto-otation in the event of engine failure, was developed.
Abstract: A method is developed for the minimum weight design of helicopter rotor blades having multiple coupled flap-lag natural frequency constraints, in addition to a constraint on the minimum blade autorotation value that will ensure sufficient rotary inertia for autorotation in the event of engine failure. Design variables encompass blade taper ratio, box beam dimensions, and the magnitudes of the nonstructural weights. Optimum designs have been obtained for both rectangular and tapered blades; attention is given to the optimum blade weight effect and the blade mass and stiffness distribution effects of adding constraints on higher frequencies and stresses.

Proceedings ArticleDOI
06 Jun 1988
TL;DR: In this paper, an automated procedure is presented to obtain the minimum weight design of gas turbine blades with geometry and multiple natural frequency constraints using a combined finite element-sequential linear programming, FEM-SLP technique.
Abstract: In this paper an automated procedure is presented to obtain the minimum weight design of gas turbine blades with geometry and multiple natural frequency constraints. The objective is achieved using a combined finite element-sequential linear programming, FEM-SLP technique. Thickness of selected finite elements are used as design variables. Geometric constraints are imposed on the thickness variations such that the optimal design has smooth aerodynamic shape. Based on the natural frequencies and mode shapes obtained from finite element analysis an assumed mode reanalysis technique is used to provide the approximate derivatives of weight and constraints with respect to design variables for sequential linear programming. The results from SLP provide the initial design for the next FEM-SLP process. An example is presented to illustrate the interactive system developed for the optimization procedure.© 1988 ASME

Journal ArticleDOI
TL;DR: In this article, the minimum weight optimization of arbitrary shaped plates under size, stress, and displacement constraints was studied, and the 8-nodes isoparametric plate element was incorporated with the optimization procedure by using Lagrange multipliers and the Kuhn-Tucker optimality condition.

Journal ArticleDOI
TL;DR: In this paper, the least-weight problem of a truncated, hollow, hexagonal core and subjected to a given bending moment along each edge is analyzed in order to meet the practical manufacturing requirements and be within allowable stress limits, constraints are placed on the geometrical dimensions of the structural parts of the sandwich panel as well as on the physical strength.
Abstract: The least‐weight problem of a sandwich panel with a truncated, hollow, hexagonal core, and subjected to a given bending moment along each edge is analyzed in this paper. In order to meet the practical manufacturing requirements and be within allowable stress limits, constraints are placed on the geometrical dimensions of the structural parts of the sandwich panel as well as on the physical strength, such as the allowable stresses. Upper and lower limiting values are assigned for each of the design variables. Through the use of the penalty function, the minimization problem subjected to a set of twenty inequality constraints is changed to a sequence of unconstrained ones. The modified Fletcher‐Powell method is used by a proper choice of the penalty parameter and the reduction factor. The methodology presented here can be extended to include multiple loading conditions, bending rigidity, and shear rigidity requirements, which present no additional difficulties except to increase the number of constraints.

Journal ArticleDOI
F. Erbatur1
TL;DR: In this article, the authors considered the optimum design of elastic continuous beams of solid crosssection, subjected to static loading, and the deflection at a given point along the beam, is specified.
Abstract: The paper is concerned with optimum design of elastic continuous beams of solid crosssection, subjected to static loading. The deflection at a given point, along the beam, is specified. Assuming a rectangular cross-section and taking the thickness as the design variable, the thickness variation is sought as to make the weight of the beam a minimum. In the formulation, an energy concept is used. A numerical example is given for illustration.

Book ChapterDOI
01 Jan 1988
TL;DR: Numerical results show that the optimum design sensitivity highly depends on both the pretwist angle and setting angle for the multiple frequency constraint case and for the dynamic response constraint case, which only significantly depends on the setting angle.
Abstract: The objective of this paper is to find the minimum weight design of rotating pretwist cantilevered beam system under periodic loads with frequency and/or dynamic response constraints. The cross-section area of the beam with some limitations (side constraints) are the system design variables. The algorithms of the optimality criterion method (OCM) and the modified method of feasible directions (MMFD) are employed for the optimal design of the system. Numerical results show that the optimum design sensitivity highly depends on both the pretwist angle and setting angle for the multiple frequency constraint case. For the dynamic response constraint case, the optimum design sensitivity only significantly depends on the setting angle.