1. Full Professor, Dept. of Civil, Environmental and Mechanical Engineering, Univ. of Trento, Via Mesiano, 77, 38123 Trento, Italy.
2. Full Professor, Dept. of Civil, Environmental, Aerospace, Materials Engineering, Univ. of Palermo, viale delle Scienze, Ed. 8, 90128 Palermo, Italy.
3. Associate Professor, Dept. of Civil, Environmental, Aerospace, Materials Engineering, Univ. of Palermo, viale delle Scienze, Ed. 8, 90128 Palermo, Italy (corresponding author).