1. Researcher, Dept. of Civil Engineering, Univ. of Salerno, Fisciano, 84084 Salerno, Italy.
2. Assistant Professor, Dept. of Civil Engineering, Univ. of Salerno, Fisciano, 84084 Salerno, Italy (corresponding author).
3. Professor, Dept. of Civil Engineering, Univ. of Salerno, Fisciano, 84084 Salerno, Italy.