1. Research Student, School of Civil and Environmental Engineering, Univ. of New South Wales, UNSW, Sydney, NSW 2052, Australia. E-mail: twang@civeng.unsw.edu.au
2. Scientia Professor and ARC Federation Fellow, School of Civil and Environmental Engineering, Univ. of New South Wales (corresponding author). E-mail: m.bradford@unsw.edu.au
3. Professor and Australian Professorial Fellow, School of Civil and Environmental Engineering, Univ. of New South Wales. E-mail: i.gilbert@unsw.edu.au