1776. Necessary Conditions of Geometrical Stability in Trusses Which Include One-Force Members

Paper

Abstract

Customary definitions of trusses permit them to include three types of members: (1) members which resist only forces in tension, one-force members, (2) members which resist only forces in compression, one-force members, and (3) members which resist both forces in tension and forces in compression, two-force members. If a truss includes only two-force members then a certain set of conditions must occur in order for it to be geometrically stable, and current theory identifies those conditions. If a truss includes any one-force members then it can be shown that for many trusses some different set of conditions must occur; however, current theory does not identify those conditions for any set of trusses. Hence, current theory does not answer an interesting question: Are there any such conditions which on both theoretical and practical criteria are more favorable when trusses are permitted to include one-force members than when trusses are permitted to include only two-force members?