Force Limiting Devices in Space Trusses

The notion of a force-limiting device that has the characteristic of ideal elastic-plastic behavior is introduced and applied to the compressive chords of a two-layer parallel-chord space truss. Examples are used to illustrate the usefulness of force-limiting devices in providing a desirable overall truss load-deflection characteristic. The results illustrate the variation of load capacity of the trusses depending on the load level chosen for the force-limiting device. An analysis is given of the problem of scatter of pin-ended column peak loads, the scatter of forces in these trusses from the theoretical values, and the possible scatter in load capacities of force-limiting devices. The end result is that the brittle-type characteristic that is usually associated with strut buckling in trusses is replaced by the elastic-plastic characteristic of the member force-limiting device, with a consequent beneficial effect on overall truss behavior in the inelastic range.