1. Ph.D. Candidate, Dept. of Civil and Natural Resources Engineering, Univ. of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand (corresponding author).
2. Professor, Dept. of Civil and Natural Resources Engineering, Univ. of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand.
3. Professor, Dept. of Civil and Natural Resources Engineering, Univ. of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand; Professor, Dept. of Structural and Geotechnical Engineering, La Sapienza Univ. of Rome, Piazzale Aldo Moro, 5, 00185 Roma, Italy.