Structural analysis by method of equivalent stiffness

The aim of this paper is to introduce a simplified method for the structural analysis of rigid plane and space frames, based on principles which are well known to structural engineers and which do not involve serious mathematics. The derivation of formulae is based on the concept that when a member, continuous over several rigid joints or supports, is cut at any of its joints, the equilibrium of the two portions of the structure is unaltered if the slopes at the section cut are preserved. Thus, either its left-hand or its righthand portion can be replaced by any such torsional or flexural member that fulfils this requirement. This substitute member is said to have the equivalent stiffness of the portion of the structure which it replaces as it exerts the same effect on the remaining portion of the structure as the part removed. This concept leads to the development of a method of transforming a complicated plane or space frame having mutually perpendicular members into a much simpler type of plane structure for analysis.

L.K. Chen and K.C. Wong