1. Full Professor, Structural Engineering, Dept. of Engineering, Univ. of Palermo, Viale delle Scienze, Palermo 90128, Italy (corresponding author).
2. Postdoctoral Researcher, Dept. of Engineering, Univ. of Palermo, Viale delle Scienze, Palermo 90128, Italy.
3. Full Professor, Structural Engineering, Dept. of Engineering, Univ. of Palermo, Viale delle Scienze, Palermo 90128, Italy.