1. Graduate Student, Dept. of Civil and Environmental Engineering, The Univ. of Auckland, Private Bag 92019, Auckland, New Zealand. E-mail: tclu001@ec.auckland.ac.nz
2. Professor, Dept. of Engineering, Univ. of Aberdeen, Aberdeen, AB24 3UE, U.K.
3. Associate Professor, Dept. of Civil and Environmental Engineering, The Univ. of Auckland, Private Bag 92019, Auckland, New Zealand.
4. Lecturer, Dept. of Civil and Environmental Engineering, The Univ. of Auckland, Private Bag 92019, Auckland, New Zealand.
5. Professor, Dept. of Civil and Environmental Engineering, The Univ. of Auckland, Private Bag 92019, Auckland, New Zealand.