1. Prof., Dept. of Civ. and Envir. Engrg., Univ. of Adelaide, Adelaide 5005, Australia. E-mail: gdandy@civeng.adelaide.edu.au
2. Former Grad. Student, Dept. of Civ. and Envir. Engrg., Univ. of Adelaide, Adelaide 5005, Australia. E-mail: M.O.Engelhardt@exeter.ac.uk