Showing papers on "Minimum weight published in 1979"

Comparison of Optimality Criteria Algorithms for Minimum Weight Design of Structures

Abstract: This paper presents a comparison of frequently used optimization algorithms based on optimality criteria to design a minimum weight structure. After summarizing the different methods, the relationship between the various algorithms is shown. They differ only in the degree of approximations made in formulating the recurrence relations to modify the design variables and to evaluate the Lagrange multipliers. A new iterative scheme, similar to Newton-Raphson, is also presented, with the equations written in such a form that it is not necessary to select the initial design vector of the unknown Lagrange multipliers. It is shown that with this scheme a minimum weight design can be obtained with a smaller number of analyses of the structure than with previously proposed methods.

A cubic extended interior penalty function for structural optimization

Abstract: This paper describes an optimization procedure for the minimum weight design of complex structures. The procedure is based on a new cubic extended interior penalty function (CEIPF) used with the sequence of unconstrained minimization technique (SUMT) and Newton's method. The Hessian matrix of the penalty function is approximated using only constraints and their derivatives. The CEIPF is designed to minimize the error in the approximation of the Hessian matrix, and as a result the number of structural analyses required is small and independent of the number of design variables. Three example problems are reported. The number of structural analyses is reduced by as much as 50 per cent below previously reported results.

An improved analysis/synthesis capability based on dual methods - ACCESS 3

Abstract: Approximation concepts and dual method algorithms are combined to create a new method for minimum weight design of structural systems. Approximation concepts convert the basic mathematical programming statement of the structural synthesis problem into a sequence of explicit primal problems of separable form. These problems are solved by constructing explicit dual functions, which are maximized subject to nonnegativity constraints. The dual method is successfully extended to deal with pure discrete and mixed continuous-discrete design variable problems. The power of the method presented is illustrated with numerical results for example problems, including a thin delta wing with fiber composite skins.

Minimum weight design

Abstract: This chapter discusses the minimum weight design. The process of design is one in which the load factor is required to have a given minimum value, and the plastic moments of the various members of the structure are required. When a design is required for a single set of loads, any bending moment distribution satisfying the equilibrium and yield conditions constitutes a possible basis for design. The chapter reviews minimum weight design using prismatic members, and the use of members of continuously varying cross section is discussed. If the weight line is tangential to the permissible region over a finite range, a range of minimum weight designs is possible. A design gives the minimum weight if it satisfies four conditions: (1) equilibrium condition, (2) yield condition, (3) mechanism condition, and (4) plastic hinge condition. The first three conditions are identical with those for the plastic collapse of any structure, and it is the fourth condition that imposes minimum weight.

An improved analysis/synthesis capability based on dual methods - ACCESS 3. [for minimum weight design of structures]

Abstract: Approximation concepts and dual method algorithms are combined to create a new method for minimum weight design of structural systems. Approximation concepts convert the basic mathematical programming statement of the structural synthesis problem into a sequence of explicit primal problems of separable form. These problems are solved by constructing explicit dual functions, which are maximized subject to nonnegativity constraints. The dual method is successfully extended to deal with pure discrete and mixed continuous-discrete design variable problems. The power of the method presented is illustrated with numerical results for example problems, including a thin delta wing with fiber composite skins.

On design problems of grid shells

Abstract: The paper deals with some design problems for grid shells, i.e. spatial structures composed of beam elements whose shape is obtained with inversion of a suspended cable net. The method comes from the conviction that optimal shape of the grid shell is so obtained. The paper points the attention on the fact that the method in object doesn't lead to the optimal shape in case of multiple load conditions. Through an optimization computer procedure, using iterative perturbations of the initial net shape, under constraints of constructive type, the geometry of the cable net that leads to the real minimum weight of the shell structure is finally reached.

Optimum Design of Pressure Stabilized Beams

Abstract: : The minimum weight design problem for pressure-stabilized beams is formulated and solved in order to provide the designer some guidance in the use of the design analysis capability developed and reported previously. The weight is minimized subject to four inequality constraints to give the inflation pressure, cross-section radius and fabric density corresponding to the minimum weight. It is shown that high pressures, small radii, and low fabric density give minimum weight. In addition, it is found that high fabric strength and low fabric stiffness per unit weight should be used for minimizing the weight.

Binomial vector multiplier circuit

Abstract: PURPOSE:To simplify a circuit constitution by using a single accumulator, other simple control circuits, a minimum weight code generator circuit, etc., to make binominal vector multiplication possible and reducing the circuit scale without lowering a processing speed. CONSTITUTION:Minimum weight code generator circuit 200 which converts the first and the second variables inputted in series from input terminals 1 and 2 to minimum weight codes different from each other is provided, and further, control circuit 300 which uses minimum weight codes of the first and the second variables, which are obtained by circuit 200, to generate a selection signal and an adjustable control signal is provided. Meanwhile, selection circuit 400 which selects one of the third varaible, the fourth variable, the half of the value of the fourth variable and a zero on a basis of the third and the fourth variables, which are inputted in parallel to input terminals 103 and 104, and the selection signal from circuit 300 and adder- subtractor 500 which executes the addition or subtraction operation between the half of the accumulated value and the output of circuit 400 on a basis of the adjustable control signal generated from circuit 300 and outputs a new accumulated value are provided, thereby operating the sum of the product between the first variable and the third variable and the product between the second variable and the fourth variable.

Properties of Transparent Shortened Codes for Memories With Stuck-at Faults

Abstract: This correspondence deals with the problem of selecting optimal shortened d = 3 Hamming codes and d = 4 extended Hamming codes. The studied codes are transparent codes, minimum column weight codes, and codes with a minimum number of codewords of minimum weight. It is concluded that a shortened code normally does not combine the properties of being transparent, being of minimum column weight type and having a minimum number of codewords of minimum weight. Furthermore, it is concluded that the weight distribution of a shortened code depends on the selected set of shortened information symbols for a given fixed number of shortened symbols. The correspondence also gives examples of good 22, 16 codes.