A measure of utility of parts of plane frames

This study was undertaken because of a paper by Croll [4] showing that the basic structural economy of suspension bridges was inferior to that of cable-stayed ones. While agreeing with this result, the present author sought for an insight that would make it plain that this was so, and why, and developed a quantitative measure of utility u for any element of such a structure. This utility factor gives an immediate indication of the relative usefulness of an element of given direction at a given point in a plane structure carrying a given system of loads and confined to a certain area of its plane. It confirms Croll's result by inspection, and is offered as an aid to designers concerned with structural economy. Its derivation and examples of its use are given.