1. Assistant Professor, Dept. of Structural and Geotechnical Engineering (DISTR), Politecnico di Torino, Room 7 Corso Duca degli Abruzzi 24, 10129 Turin, Italy (corresponding author).
2. Clifford C Furnas Eminent Professor, Dept. of Civil, Structural and Environmental Engineering, Univ. at Buffalo, The State Univ. of New York, 135 Ketter Hall, Buffalo, NY 14260.