ABSTRACT
The behaviour of concrete elements with a low steel percentage may differ to a significant extent from the ideal scheme which is usually adopted, in which the moment-curvature diagram of an element in flexure takes on the shape illustrated in Fig. 1. This difference has already attracted attention in the years from 1950 to 1960, when steel yielding moment values exceeding (by as much as 35%) the theoretically calculated values, were experimentally observed. This is hard to explain, all the more so as the phenomenon is obviously seen to occur when the steel yield limit is reached and the evaluation of the internal lever arm displays a modest degree of indeterminacy, due to the low steel percentage.
