Accession Number:

AD0415081

Title:

ON SOME MISCONCEPTIONS IN THE DIRECT DESIGN OF STRUCTURES,

Descriptive Note:

Corporate Author:

ILLINOIS INST OF TECH CHICAGO

Report Date:

1963-07-01

Pagination or Media Count:

13.0

Abstract:

In the absence of a direct method of minimumweight design for two-dimensional structures, the concept of equal-strength design has frequently been used in the past. According to this concept, a structure is designed so that the two principal stresses or principal moments in the case of bending are equal at each point. In many problems the equal strength design is the same as the minimum-weight design, but it is erroneous to assume, as has been done in at least one recent paper that the two criteria are synonymous. Ther present paper presents two elementary counter examples to the above false proposition. For a clamped circular plate under a ring load a design is found which is of lower weight than that of the equal-strength design, and for a simply supported annular plate under a ring load on its inner edge it is shown that no equal-strength design exists. Some general conclusions regarding direct minimum-weight design of plates are then presented. In particular it is shown by example that if weight is determined by a single design parameter, the resulting function may have minimum which is nonanalytic and points of zero first variation which are not minima. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE