1. Dept. of Structural and Geotechnical Engineering, Sapienza Univ. of Rome, 18, Eudossiana St., 00184 Rome, Italy (corresponding author).
2. Full Professor, Dept. of Structural and Geotechnical Engineering, Sapienza Univ. of Rome, 18, Eudossiana St., 00184 Rome, Italy.
3. Associate Professor, Dept. of Engineering and Geology, Univ. G. D’Annunzio of Chieti-Pescara, 42, Pindaro St., 65127 Pescara, Italy.