1. Postdoctoral Researcher, Dipartimento di Ingegneria Idraulica, Marittima e Geotecnica, Universita` di Padova, Vai Loredan 20, 35131 Padua, Italy.
2. Associate Professor, Dept. of Civil, Structural, and Environmental Engineering, 233 Jarvis Hall, State Univ. of New York at Buffalo, Buffalo, NY 14260 (corresponding author).