1. Ph.D. Candidate, Dept. of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061.
2. Professor, Dept. of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061 (corresponding author).
3. Research Fellow, Dept. of Civil and Environmental Engineering, National Univ. of Singapore, Singapore 117576; formerly, Associate Research Fellow, School of Civil, Mining, and Environmental Engineering, Univ. of Wollongong, NSW, Australia.
4. Professor, Dept. of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061.