1. Design Engineer, VSL Australia Pty. Ltd., Locked Bag 102, Pennant Hills, NSW 2120, Australia (corresponding author). E-mail: gwight@vsl-australia.com.au
2. Associate Professor, Dept. of Civil, Construction and Environmental Engineering, North Carolina State Univ., Box 7908, Raleigh, NC 27695-7908. E-mail: kowalsky@ncsu.edu
3. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Auckland, Private Bag 92019, Auckland, New Zealand. E-mail: j.ingham@auckland.ac.nz