Issue 22

S. Bennati et alii, Frattura ed Integrità Strutturale, 22 (2012) 39-55 ; DOI: 10.3221/IGF-ESIS.22.06 50 the instants such displacement exceeds the values 0  w and  u w respectively mark the beginning of interface softening and debonding behaviour. a) b) c) Figure 10 : Relative displacement  w ( z ) and tangential stress  ( z ): a) stage 1: 0 M M  ; b) stage 2: 0.9  u M M ; c) stage 3: 1.01  u M M . Fig. 11 shows a plot of the bending moment in the beam, M , as a function of the abscissa, z , for four values of the applied couple, M , corresponding to the four stages of behaviour described in the previous section. Note that with increasing M and the consequent progressive detachment of the reinforcement, the strengthened beam’s response tends towards that of a beam lacking any reinforcement.