Synopsis
A brief discussion of the essential differences between yield-line theory and limit analysis is followed by an examination of whether or not it is possible to prove the existence or otherwise of exact solutions in all cases in limit analysis, in the light of considerable new evidence. It is maintained that the evidence is now strong enough to eliminate the possibility of exact solutions for most slabs governed by the ‘square’ yield criterion, especially continuous and encastered slabs commonly dealt with in yield-line theory. The changes that this would entail in the future direction of reinforced concrete research, and the immediate practical consequences, are discussed. It is suggested that the nodal-force theory of Johansen is a general technique which could well find application in many other branches of science.
