1. Graduate student, Department of Civil Engineering, University of Toronto, Toronto, M5S 1A4, Ontario Canada
2. Assoc. Prof. of Hydr., Department of Water and Struct. Engineering, University of Perugia, via G. Duranti 93, 06125 Perugia, Italy
3. Professor, Department of Civil Engineering, University of Toronto, Toronto, M5S 1A4, Ontario Canada
4. Research Assistant, Department of Water and Struct. Engineering, University of Perugia, via G. Duranti 93, 06125 Perugia, Italy