1. Research Assistant, Dept. of Structural and Geotechnical Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.
2. Assistant Professor, Dept. of Civil Engineering, Univ. of Parma, Parco Area delle Scienze 181/A, 43100 Parma, Italy.
3. Professor, Dept. of Structural Engineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.