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SIR,In the recent paper entitled “Stress Analysis of Modern Structural Frames,” as
reported in the September issue of The Structural Engineer, Mr. J.B.M. Hay is to be congratulated upon bringing up the question of the direct design of indeterminate structures. Most engineers are familiar with the difficulties of mathematical analysis, some of which Mr. Hay pointed out, but rarely is there an exposition of a method of direct design such as that given in the first paragraph of page 392.
1. The various analytical methods for determining the stresses in a continuous framework all start from the same assumptions and lead to the same conclusions, the intermediate processes being relatively long or short according to the characteristics of the particu1ar problem involved. The Author has indicated elsewhere the derivation of special methods from the principle of least work (R. l), and has shown that where it can be applied directly the method of analysis by the principle of least work gives results more readily and more simply than is possible by the application of special methods (R. 2,3). In this paper the method of least work is extended to cover all types of frameworks.
TESTS made on structures for the purpose of obtaining new or confirmatory information can be divided into three main groups:-
I. Those dealing with the strength, durability and mechanical properties of materials and construction. Tests of the chemical composition of materials are the work of the analytical chemist and not the structural engineer, although the latter is, of course, interested in the chemical composition in so far as it affects strength and durability.
II. Tests of foundations and incidentally of the properties of the media by which the substructures are supported.
III. Tests of the mechanical and static properties and strength of projected or completed superstructures.