Fig. 2
![Fig. 2](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40623-017-0641-3/MediaObjects/40623_2017_641_Fig2_HTML.gif)
Definition of the damage index based on the damage state and displacements thresholds of Lagomarsino and Giovinazzi (2006). The black line is the capacity curve; the multi-colored piecewise linear line corresponds to the new defined damage index. d y is the yield displacement (m) and d u is the ultimate displacement (m). See text for further explanations