1. Assistant Professor, Dept. of Structural, Building and Geotechnical Engineering (DISEG), Politecnico di Torino, 10129 Turin, Italy (corresponding author).
2. Research Engineer, ITALGAS.SPA, Largo Regio Parco 9, 10153 Turin, Italy.
3. Professor, Dept. of Civil, Structural and Environmental Engineering, Univ. at Buffalo (SUNY), State Univ. of New York, 130 Ketter Hall, Buffalo, NY 14260.