Showing papers on "Minimum weight published in 1970"

Minimum weight design of complex structures subject to a frequency constraint

Abstract: An analytical procedure is presented for the determination of the least weight structure which satisfies a specific frequency requirement. The approach is to modify an existing structure by varying the cross-sectional properties of its member. This is accomplished using separate gradient equations to first obtain the correct structural frequency and then, while the frequency is held constant, to minimize the weight. These equations are derived in matrix notation for direct application to the finite element method of analysis. This procedure has been completely automated in a computer program which includes the substructure analysis capability for treating large complex structures. Problems up to 1800 degrees of freedom may be optimized by varying as many as 100 of the structural elements in a single run. Results of four numerical examples show that the method is convergent and that optimized configurations can be determined in less than 10 redesign cycles.

Minimum Weight Design of Light Gage Steel Members

Abstract: Light gage steel is used extensively in light construction components. Large tonnages of a standard design are commonly produced, thus the minimum material requirements are of utmost importance to the product designer. A technique is presented for designing a minimum weight member to support a given loading condition. The problem is treated as a numerical optimization problem in which the variables are the dimensions and thickness of a given type of cross-sectional shape. Design requirements are based on the American Iron and Steel Institute Specification for the Design of Cold-Formed Steel Structural Members, 1968 Edition. These requirements are used to calculate a minimum acceptable thickness for a section whose other dimensions are considered temporarily fixed. This establishes the minimum weight design for the particular set of dimensions. Search methods are then employed to systematically establish sets of dimensions yielding reduced weight sections. Both a direct search and gradient search were examined and the latter found to be more efficient.

Minimum weight design of stiffened cylinders

Abstract: Minimum weight design for symmetrically stiffened cylindrical shells under compression based on linear orthotropic stability theory

Minimum Weight Design with Stability Constraint

Abstract: The problem of minimum weight design of structures composed of finite elements each having a finite number of degrees of freedom and subject to a critical buckling load constraint is formulated as in nonlinear programming. Employing the accelerated cutting plane method of Wolfe, all constraints except the general buckling load constraint are expressed by linear inequalities. A method for the solution of this problem is developed which differs from the projected gradient method only in the way the direction of motion is selected once the nonlinear constraint is encountered. The method involves first moving in the direction of the projected gradient, and then returning to this region on the hyperplane of constant weight along the projection of the buckling-constraint gradient. The method is applied to the minimum weight design of a built-up column of varying width.

Hamming Codes, Single Error — Correcting and Cyclic

Abstract: We now consider the problem of constructing linear codes which are capable of correcting all error words of weight no greater than t. If the code is defined as the null space of the H matrix, and the syndrome is given by st = HRt, then the decoder must attempt to find a minimum weight E which solves the equation

Optimization of Redundant Prestressed Structures

Abstract: The load index approach to structural optimization is extended to similar or mixed element systems with statically determinate or redundant prestressed configurations and under multiple load conditions. Employing component optimization expressions reduces the problem to an unconstrained search through a space defined in terms of variables which express the relative orientation of component elements and the redundant loads. It is shown that a minimum weight truss may be prestressed redundant under a single external load condition if the internal prestress is considered as a separate load condition, i.e., the truss must not fail under the internal prestress in the absence of the applied load. Multiple load truss applications show that additional weight savings over previous analyses can be realized by optimizing bar orientation and redundant load. Optimizing of redundant loads, however, will in general require a turnbuckle in series with a flexible spring in order to maintain a unique prestress under multiple load conditions.

Numerical Optimisation Of Sandwich AndLaminated Composite Structures

Abstract: The main object of present investigations is numerical optimisation of damping the vibrations and weight of sandwich and laminated composite structures in harmonic oscillations at frequencies close to the natural frequencies of structure. The method of planning of experiments is used for this purpose. Computations are carried out by using a finite element method and two methods of dynamic analysis: the method of complex eigenvalues and method of the potential energy of eigenmodes. The frequency response analysis is also applied. For numerical analysis of examined structures the finite element models of sandwich and laminated composite beams and plates were developed. Energy of dissipation in the viscoelastic layers is taking into account using complex modules of elasticity. As examples the optimal design of sandwich and laminated composite beams and plates for a maximum damping and minimum weight is presented.

Minimum Weight Shear Panels

Abstract: some of the complexities encountered in designing efficient structures from composite materials. The problem is the apparently simple one of designing a minimum weight boron/epoxy shear panel. The primary mechanical requirement is that of maintaining a specified level of shear stiffness. Suppose also that the panel contains a regularly spaced array of circular cutouts, as shown in Figure 1. The holes could come about either as an additional requirement on the proper functioning of the structure

Minimum weight design of frames using sway subassemblage theory, December 1970

Abstract: TABLE OF CONTENTS 1

On the Minimum Weight of Orthogonally Stiffened Plates under Lateral Pressure

Abstract: This paper concerns on the minimum weight design of such a stiffened plates as bulkheads bottom plates and outside platings of ship under lateral pressure.Criterion of these plates based on the collapse load of orthogonally stiffened plates, and the deflection criterion was applied to the plate of panel.The weight of the stiffened plates was calculated assuming the external pressure, safety factor, the aspect ratio of the plates, and the number of stiffeners.In these calculation, the local buckling of the stiffener was considered in the ratio of breadth and thickness of web or flange plate.The minimum weight of the stiffened plates and the corresponding number of stiffeners were obtained for giving pressure, aspect ratio of the plates and safety factors.