1. Professor of Structural Mechanics, Dept. of Structural Engineering and Geotechnics, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.
2. Assistant Professor of Structural Mechanics, Dept. of Structural Engineering and Geotechnics, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy (corresponding author).