1. Associate Professor, Univ. of Palermo, Edificio 8, Viale delle Scienze, 90128 Palermo, Italy.
2. Full Professor, Univ. of Palermo, Edificio 8, Viale delle Scienze, 90128 Palermo, Italy.
3. Research Fellow, Dept. of Civil, Environmental, Aerospace and Material Engineering, Univ. of Palermo, Edificio 8, Viale delle Scienze, 90128 Palermo, Italy (corresponding author).