1. Ph.D. Student, Dept. of Civil and Environmental Engineering, Univ. of Parma, Parco Area delle Scienze, 181/A, 43124 Parma, Italy (corresponding author).
2. Full Professor, Dept. of Civil and Environmental Engineering, Univ. of Parma, Parco Area delle Scienze, 181/A, 43124 Parma, Italy.