1. Full Professor, Dept. of Structural and Geotechnical Engineering, Technical Univ. of Turin, Corso Duca degli Abruzzi 24-10128 Torino, Italy.
2. Researcher, Dept. of Mechanics and Materials, Mediterranean Univ. of Reggio Calabria, Via Graziella (Feo diVito)-89060 Reggio Calabria, Italy.