1. Dept. of Civil and Environmental Engineering, Univ. of Auckland, 20 Symonds St., Auckland 1010, New Zealand (corresponding author).
2. Lecturer, Dept. of Civil and Environmental Engineering, Univ. of Auckland, 20 Symonds St., Auckland 1010, New Zealand.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Auckland, 20 Symonds St., Auckland 1010, New Zealand.
4. Professor, Dept. of Civil and Natural Resources Engineering, Univ. of Canterbury, Christchurch 8140, New Zealand.