1. Lecturer, School of Built Environment, Heriot-Watt Univ., Edinburgh EH14 4AS, U.K. (corresponding author).
2. Assistant Professor, School of Engineering, Univ. of Warwick, Coventry CV4 7AL, U.K.
3. Professor, Centre for Infrastructure Engineering and Safety, Univ. of New South Wales, Sydney, NSW 2052, Australia.